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dtrace.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 *
 * $FreeBSD$
 */

/*
 * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#pragma ident     "%Z%%M%     %I%   %E% SMI"

/*
 * DTrace - Dynamic Tracing for Solaris
 *
 * This is the implementation of the Solaris Dynamic Tracing framework
 * (DTrace).  The user-visible interface to DTrace is described at length in
 * the "Solaris Dynamic Tracing Guide".  The interfaces between the libdtrace
 * library, the in-kernel DTrace framework, and the DTrace providers are
 * described in the block comments in the <sys/dtrace.h> header file.  The
 * internal architecture of DTrace is described in the block comments in the
 * <sys/dtrace_impl.h> header file.  The comments contained within the DTrace
 * implementation very much assume mastery of all of these sources; if one has
 * an unanswered question about the implementation, one should consult them
 * first.
 *
 * The functions here are ordered roughly as follows:
 *
 *   - Probe context functions
 *   - Probe hashing functions
 *   - Non-probe context utility functions
 *   - Matching functions
 *   - Provider-to-Framework API functions
 *   - Probe management functions
 *   - DIF object functions
 *   - Format functions
 *   - Predicate functions
 *   - ECB functions
 *   - Buffer functions
 *   - Enabling functions
 *   - DOF functions
 *   - Anonymous enabling functions
 *   - Consumer state functions
 *   - Helper functions
 *   - Hook functions
 *   - Driver cookbook functions
 *
 * Each group of functions begins with a block comment labelled the "DTrace
 * [Group] Functions", allowing one to find each block by searching forward
 * on capital-f functions.
 */
#include <sys/errno.h>
#if !defined(sun)
#include <sys/time.h>
#endif
#include <sys/stat.h>
#include <sys/modctl.h>
#include <sys/conf.h>
#include <sys/systm.h>
#if defined(sun)
#include <sys/ddi.h>
#include <sys/sunddi.h>
#endif
#include <sys/cpuvar.h>
#include <sys/kmem.h>
#if defined(sun)
#include <sys/strsubr.h>
#endif
#include <sys/sysmacros.h>
#include <sys/dtrace_impl.h>
#include <sys/atomic.h>
#include <sys/cmn_err.h>
#if defined(sun)
#include <sys/mutex_impl.h>
#include <sys/rwlock_impl.h>
#endif
#include <sys/ctf_api.h>
#if defined(sun)
#include <sys/panic.h>
#include <sys/priv_impl.h>
#endif
#include <sys/policy.h>
#if defined(sun)
#include <sys/cred_impl.h>
#include <sys/procfs_isa.h>
#endif
#include <sys/taskq.h>
#if defined(sun)
#include <sys/mkdev.h>
#include <sys/kdi.h>
#endif
#include <sys/zone.h>
#include <sys/socket.h>
#include <netinet/in.h>

/* FreeBSD includes: */
#if !defined(sun)
#include <sys/callout.h>
#include <sys/ctype.h>
#include <sys/limits.h>
#include <sys/kdb.h>
#include <sys/kernel.h>
#include <sys/malloc.h>
#include <sys/sysctl.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/rwlock.h>
#include <sys/sx.h>
#include <sys/dtrace_bsd.h>
#include <netinet/in.h>
#include "dtrace_cddl.h"
#include "dtrace_debug.c"
#endif

/*
 * DTrace Tunable Variables
 *
 * The following variables may be tuned by adding a line to /etc/system that
 * includes both the name of the DTrace module ("dtrace") and the name of the
 * variable.  For example:
 *
 *   set dtrace:dtrace_destructive_disallow = 1
 *
 * In general, the only variables that one should be tuning this way are those
 * that affect system-wide DTrace behavior, and for which the default behavior
 * is undesirable.  Most of these variables are tunable on a per-consumer
 * basis using DTrace options, and need not be tuned on a system-wide basis.
 * When tuning these variables, avoid pathological values; while some attempt
 * is made to verify the integrity of these variables, they are not considered
 * part of the supported interface to DTrace, and they are therefore not
 * checked comprehensively.  Further, these variables should not be tuned
 * dynamically via "mdb -kw" or other means; they should only be tuned via
 * /etc/system.
 */
int         dtrace_destructive_disallow = 0;
dtrace_optval_t   dtrace_nonroot_maxsize = (16 * 1024 * 1024);
size_t            dtrace_difo_maxsize = (256 * 1024);
dtrace_optval_t   dtrace_dof_maxsize = (256 * 1024);
size_t            dtrace_global_maxsize = (16 * 1024);
size_t            dtrace_actions_max = (16 * 1024);
size_t            dtrace_retain_max = 1024;
dtrace_optval_t   dtrace_helper_actions_max = 32;
dtrace_optval_t   dtrace_helper_providers_max = 32;
dtrace_optval_t   dtrace_dstate_defsize = (1 * 1024 * 1024);
size_t            dtrace_strsize_default = 256;
dtrace_optval_t   dtrace_cleanrate_default = 9900990;       /* 101 hz */
dtrace_optval_t   dtrace_cleanrate_min = 200000;                  /* 5000 hz */
dtrace_optval_t   dtrace_cleanrate_max = (uint64_t)60 * NANOSEC;  /* 1/minute */
dtrace_optval_t   dtrace_aggrate_default = NANOSEC;         /* 1 hz */
dtrace_optval_t   dtrace_statusrate_default = NANOSEC;            /* 1 hz */
dtrace_optval_t dtrace_statusrate_max = (hrtime_t)10 * NANOSEC;    /* 6/minute */
dtrace_optval_t   dtrace_switchrate_default = NANOSEC;            /* 1 hz */
dtrace_optval_t   dtrace_nspec_default = 1;
dtrace_optval_t   dtrace_specsize_default = 32 * 1024;
dtrace_optval_t dtrace_stackframes_default = 20;
dtrace_optval_t dtrace_ustackframes_default = 20;
dtrace_optval_t dtrace_jstackframes_default = 50;
dtrace_optval_t dtrace_jstackstrsize_default = 512;
int         dtrace_msgdsize_max = 128;
hrtime_t    dtrace_chill_max = 500 * (NANOSEC / MILLISEC);  /* 500 ms */
hrtime_t    dtrace_chill_interval = NANOSEC;          /* 1000 ms */
int         dtrace_devdepth_max = 32;
int         dtrace_err_verbose;
hrtime_t    dtrace_deadman_interval = NANOSEC;
hrtime_t    dtrace_deadman_timeout = (hrtime_t)10 * NANOSEC;
hrtime_t    dtrace_deadman_user = (hrtime_t)30 * NANOSEC;

/*
 * DTrace External Variables
 *
 * As dtrace(7D) is a kernel module, any DTrace variables are obviously
 * available to DTrace consumers via the backtick (`) syntax.  One of these,
 * dtrace_zero, is made deliberately so:  it is provided as a source of
 * well-known, zero-filled memory.  While this variable is not documented,
 * it is used by some translators as an implementation detail.
 */
const char  dtrace_zero[256] = { 0 };     /* zero-filled memory */

/*
 * DTrace Internal Variables
 */
#if defined(sun)
static dev_info_t *dtrace_devi;           /* device info */
#endif
#if defined(sun)
static vmem_t           *dtrace_arena;          /* probe ID arena */
static vmem_t           *dtrace_minor;          /* minor number arena */
static taskq_t          *dtrace_taskq;          /* task queue */
#else
static struct unrhdr    *dtrace_arena;          /* Probe ID number.     */
#endif
static dtrace_probe_t   **dtrace_probes;  /* array of all probes */
static int        dtrace_nprobes;         /* number of probes */
static dtrace_provider_t *dtrace_provider;      /* provider list */
static dtrace_meta_t    *dtrace_meta_pid; /* user-land meta provider */
static int        dtrace_opens;           /* number of opens */
static int        dtrace_helpers;         /* number of helpers */
#if defined(sun)
static void       *dtrace_softstate;      /* softstate pointer */
#endif
static dtrace_hash_t    *dtrace_bymod;          /* probes hashed by module */
static dtrace_hash_t    *dtrace_byfunc;         /* probes hashed by function */
static dtrace_hash_t    *dtrace_byname;         /* probes hashed by name */
static dtrace_toxrange_t *dtrace_toxrange;      /* toxic range array */
static int        dtrace_toxranges; /* number of toxic ranges */
static int        dtrace_toxranges_max;   /* size of toxic range array */
static dtrace_anon_t    dtrace_anon;            /* anonymous enabling */
static kmem_cache_t     *dtrace_state_cache;    /* cache for dynamic state */
static uint64_t         dtrace_vtime_references; /* number of vtimestamp refs */
static kthread_t  *dtrace_panicked; /* panicking thread */
static dtrace_ecb_t     *dtrace_ecb_create_cache; /* cached created ECB */
static dtrace_genid_t   dtrace_probegen;  /* current probe generation */
static dtrace_helpers_t *dtrace_deferred_pid;   /* deferred helper list */
static dtrace_enabling_t *dtrace_retained;      /* list of retained enablings */
static dtrace_dynvar_t  dtrace_dynhash_sink;    /* end of dynamic hash chains */
#if !defined(sun)
static struct mtx dtrace_unr_mtx;
MTX_SYSINIT(dtrace_unr_mtx, &dtrace_unr_mtx, "Unique resource identifier", MTX_DEF);
int         dtrace_in_probe;  /* non-zero if executing a probe */
#if defined(__i386__) || defined(__amd64__)
uintptr_t   dtrace_in_probe_addr;   /* Address of invop when already in probe */
#endif
#endif

/*
 * DTrace Locking
 * DTrace is protected by three (relatively coarse-grained) locks:
 *
 * (1) dtrace_lock is required to manipulate essentially any DTrace state,
 *     including enabling state, probes, ECBs, consumer state, helper state,
 *     etc.  Importantly, dtrace_lock is _not_ required when in probe context;
 *     probe context is lock-free -- synchronization is handled via the
 *     dtrace_sync() cross call mechanism.
 *
 * (2) dtrace_provider_lock is required when manipulating provider state, or
 *     when provider state must be held constant.
 *
 * (3) dtrace_meta_lock is required when manipulating meta provider state, or
 *     when meta provider state must be held constant.
 *
 * The lock ordering between these three locks is dtrace_meta_lock before
 * dtrace_provider_lock before dtrace_lock.  (In particular, there are
 * several places where dtrace_provider_lock is held by the framework as it
 * calls into the providers -- which then call back into the framework,
 * grabbing dtrace_lock.)
 *
 * There are two other locks in the mix:  mod_lock and cpu_lock.  With respect
 * to dtrace_provider_lock and dtrace_lock, cpu_lock continues its historical
 * role as a coarse-grained lock; it is acquired before both of these locks.
 * With respect to dtrace_meta_lock, its behavior is stranger:  cpu_lock must
 * be acquired _between_ dtrace_meta_lock and any other DTrace locks.
 * mod_lock is similar with respect to dtrace_provider_lock in that it must be
 * acquired _between_ dtrace_provider_lock and dtrace_lock.
 */
static kmutex_t         dtrace_lock;            /* probe state lock */
static kmutex_t         dtrace_provider_lock;   /* provider state lock */
static kmutex_t         dtrace_meta_lock; /* meta-provider state lock */

#if !defined(sun)
/* XXX FreeBSD hacks. */
static kmutex_t         mod_lock;

#define cr_suid         cr_svuid
#define cr_sgid         cr_svgid
#define     ipaddr_t    in_addr_t
#define mod_modname     pathname
#define vuprintf  vprintf
#define ttoproc(_a)     ((_a)->td_proc)
#define crgetzoneid(_a) 0
#define     NCPU        MAXCPU
#define SNOCD           0
#define CPU_ON_INTR(_a) 0

#define PRIV_EFFECTIVE        (1 << 0)
#define PRIV_DTRACE_KERNEL    (1 << 1)
#define PRIV_DTRACE_PROC      (1 << 2)
#define PRIV_DTRACE_USER      (1 << 3)
#define PRIV_PROC_OWNER       (1 << 4)
#define PRIV_PROC_ZONE        (1 << 5)
#define PRIV_ALL        ~0

SYSCTL_NODE(_debug, OID_AUTO, dtrace, CTLFLAG_RD, 0, "DTrace Information");
#endif

#if defined(sun)
#define curcpu    CPU->cpu_id
#endif


/*
 * DTrace Provider Variables
 *
 * These are the variables relating to DTrace as a provider (that is, the
 * provider of the BEGIN, END, and ERROR probes).
 */
static dtrace_pattr_t   dtrace_provider_attr = {
{ DTRACE_STABILITY_STABLE, DTRACE_STABILITY_STABLE, DTRACE_CLASS_COMMON },
{ DTRACE_STABILITY_PRIVATE, DTRACE_STABILITY_PRIVATE, DTRACE_CLASS_UNKNOWN },
{ DTRACE_STABILITY_PRIVATE, DTRACE_STABILITY_PRIVATE, DTRACE_CLASS_UNKNOWN },
{ DTRACE_STABILITY_STABLE, DTRACE_STABILITY_STABLE, DTRACE_CLASS_COMMON },
{ DTRACE_STABILITY_STABLE, DTRACE_STABILITY_STABLE, DTRACE_CLASS_COMMON },
};

static void
dtrace_nullop(void)
{}

static dtrace_pops_t    dtrace_provider_ops = {
      (void (*)(void *, dtrace_probedesc_t *))dtrace_nullop,
      (void (*)(void *, modctl_t *))dtrace_nullop,
      (void (*)(void *, dtrace_id_t, void *))dtrace_nullop,
      (void (*)(void *, dtrace_id_t, void *))dtrace_nullop,
      (void (*)(void *, dtrace_id_t, void *))dtrace_nullop,
      (void (*)(void *, dtrace_id_t, void *))dtrace_nullop,
      NULL,
      NULL,
      NULL,
      (void (*)(void *, dtrace_id_t, void *))dtrace_nullop
};

static dtrace_id_t      dtrace_probeid_begin;   /* special BEGIN probe */
static dtrace_id_t      dtrace_probeid_end;     /* special END probe */
dtrace_id_t       dtrace_probeid_error;   /* special ERROR probe */

/*
 * DTrace Helper Tracing Variables
 */
uint32_t dtrace_helptrace_next = 0;
uint32_t dtrace_helptrace_nlocals;
char  *dtrace_helptrace_buffer;
int   dtrace_helptrace_bufsize = 512 * 1024;

#ifdef DEBUG
int   dtrace_helptrace_enabled = 1;
#else
int   dtrace_helptrace_enabled = 0;
#endif

/*
 * DTrace Error Hashing
 *
 * On DEBUG kernels, DTrace will track the errors that has seen in a hash
 * table.  This is very useful for checking coverage of tests that are
 * expected to induce DIF or DOF processing errors, and may be useful for
 * debugging problems in the DIF code generator or in DOF generation .  The
 * error hash may be examined with the ::dtrace_errhash MDB dcmd.
 */
#ifdef DEBUG
static dtrace_errhash_t dtrace_errhash[DTRACE_ERRHASHSZ];
static const char *dtrace_errlast;
static kthread_t *dtrace_errthread;
static kmutex_t dtrace_errlock;
#endif

/*
 * DTrace Macros and Constants
 *
 * These are various macros that are useful in various spots in the
 * implementation, along with a few random constants that have no meaning
 * outside of the implementation.  There is no real structure to this cpp
 * mishmash -- but is there ever?
 */
#define     DTRACE_HASHSTR(hash, probe)   \
      dtrace_hash_str(*((char **)((uintptr_t)(probe) + (hash)->dth_stroffs)))

#define     DTRACE_HASHNEXT(hash, probe)  \
      (dtrace_probe_t **)((uintptr_t)(probe) + (hash)->dth_nextoffs)

#define     DTRACE_HASHPREV(hash, probe)  \
      (dtrace_probe_t **)((uintptr_t)(probe) + (hash)->dth_prevoffs)

#define     DTRACE_HASHEQ(hash, lhs, rhs) \
      (strcmp(*((char **)((uintptr_t)(lhs) + (hash)->dth_stroffs)), \
          *((char **)((uintptr_t)(rhs) + (hash)->dth_stroffs))) == 0)

#define     DTRACE_AGGHASHSIZE_SLEW       17

#define     DTRACE_V4MAPPED_OFFSET        (sizeof (uint32_t) * 3)

/*
 * The key for a thread-local variable consists of the lower 61 bits of the
 * t_did, plus the 3 bits of the highest active interrupt above LOCK_LEVEL.
 * We add DIF_VARIABLE_MAX to t_did to assure that the thread key is never
 * equal to a variable identifier.  This is necessary (but not sufficient) to
 * assure that global associative arrays never collide with thread-local
 * variables.  To guarantee that they cannot collide, we must also define the
 * order for keying dynamic variables.  That order is:
 *
 *   [ key0 ] ... [ keyn ] [ variable-key ] [ tls-key ]
 *
 * Because the variable-key and the tls-key are in orthogonal spaces, there is
 * no way for a global variable key signature to match a thread-local key
 * signature.
 */
#if defined(sun)
#define     DTRACE_TLS_THRKEY(where) { \
      uint_t intr = 0; \
      uint_t actv = CPU->cpu_intr_actv >> (LOCK_LEVEL + 1); \
      for (; actv; actv >>= 1) \
            intr++; \
      ASSERT(intr < (1 << 3)); \
      (where) = ((curthread->t_did + DIF_VARIABLE_MAX) & \
          (((uint64_t)1 << 61) - 1)) | ((uint64_t)intr << 61); \
}
#else
#define     DTRACE_TLS_THRKEY(where) { \
      solaris_cpu_t *_c = &solaris_cpu[curcpu]; \
      uint_t intr = 0; \
      uint_t actv = _c->cpu_intr_actv; \
      for (; actv; actv >>= 1) \
            intr++; \
      ASSERT(intr < (1 << 3)); \
      (where) = ((curthread->td_tid + DIF_VARIABLE_MAX) & \
          (((uint64_t)1 << 61) - 1)) | ((uint64_t)intr << 61); \
}
#endif

#define     DT_BSWAP_8(x)     ((x) & 0xff)
#define     DT_BSWAP_16(x)    ((DT_BSWAP_8(x) << 8) | DT_BSWAP_8((x) >> 8))
#define     DT_BSWAP_32(x)    ((DT_BSWAP_16(x) << 16) | DT_BSWAP_16((x) >> 16))
#define     DT_BSWAP_64(x)    ((DT_BSWAP_32(x) << 32) | DT_BSWAP_32((x) >> 32))

#define     DT_MASK_LO 0x00000000FFFFFFFFULL

#define     DTRACE_STORE(type, tomax, offset, what) \
      *((type *)((uintptr_t)(tomax) + (uintptr_t)offset)) = (type)(what);

#ifndef __i386
#define     DTRACE_ALIGNCHECK(addr, size, flags)                        \
      if (addr & (size - 1)) {                              \
            *flags |= CPU_DTRACE_BADALIGN;                        \
            cpu_core[curcpu].cpuc_dtrace_illval = addr;     \
            return (0);                               \
      }
#else
#define     DTRACE_ALIGNCHECK(addr, size, flags)
#endif

/*
 * Test whether a range of memory starting at testaddr of size testsz falls
 * within the range of memory described by addr, sz.  We take care to avoid
 * problems with overflow and underflow of the unsigned quantities, and
 * disallow all negative sizes.  Ranges of size 0 are allowed.
 */
#define     DTRACE_INRANGE(testaddr, testsz, baseaddr, basesz) \
      ((testaddr) - (baseaddr) < (basesz) && \
      (testaddr) + (testsz) - (baseaddr) <= (basesz) && \
      (testaddr) + (testsz) >= (testaddr))

/*
 * Test whether alloc_sz bytes will fit in the scratch region.  We isolate
 * alloc_sz on the righthand side of the comparison in order to avoid overflow
 * or underflow in the comparison with it.  This is simpler than the INRANGE
 * check above, because we know that the dtms_scratch_ptr is valid in the
 * range.  Allocations of size zero are allowed.
 */
#define     DTRACE_INSCRATCH(mstate, alloc_sz) \
      ((mstate)->dtms_scratch_base + (mstate)->dtms_scratch_size - \
      (mstate)->dtms_scratch_ptr >= (alloc_sz))

#define     DTRACE_LOADFUNC(bits)                                 \
/*CSTYLED*/                                           \
uint##bits##_t                                              \
dtrace_load##bits(uintptr_t addr)                           \
{                                                     \
      size_t size = bits / NBBY;                            \
      /*CSTYLED*/                                     \
      uint##bits##_t rval;                                  \
      int i;                                                \
      volatile uint16_t *flags = (volatile uint16_t *)            \
          &cpu_core[curcpu].cpuc_dtrace_flags;              \
                                                      \
      DTRACE_ALIGNCHECK(addr, size, flags);                       \
                                                      \
      for (i = 0; i < dtrace_toxranges; i++) {              \
            if (addr >= dtrace_toxrange[i].dtt_limit)       \
                  continue;                           \
                                                      \
            if (addr + size <= dtrace_toxrange[i].dtt_base)       \
                  continue;                           \
                                                      \
            /*                                        \
             * This address falls within a toxic region; return 0.      \
             */                                       \
            *flags |= CPU_DTRACE_BADADDR;                   \
            cpu_core[curcpu].cpuc_dtrace_illval = addr;           \
            return (0);                               \
      }                                               \
                                                      \
      *flags |= CPU_DTRACE_NOFAULT;                         \
      /*CSTYLED*/                                     \
      rval = *((volatile uint##bits##_t *)addr);                  \
      *flags &= ~CPU_DTRACE_NOFAULT;                              \
                                                      \
      return (!(*flags & CPU_DTRACE_FAULT) ? rval : 0);           \
}

#ifdef _LP64
#define     dtrace_loadptr    dtrace_load64
#else
#define     dtrace_loadptr    dtrace_load32
#endif

#define     DTRACE_DYNHASH_FREE     0
#define     DTRACE_DYNHASH_SINK     1
#define     DTRACE_DYNHASH_VALID    2

#define     DTRACE_MATCH_NEXT 0
#define     DTRACE_MATCH_DONE 1
#define     DTRACE_ANCHORED(probe)  ((probe)->dtpr_func[0] != '\0')
#define     DTRACE_STATE_ALIGN      64

#define     DTRACE_FLAGS2FLT(flags)                               \
      (((flags) & CPU_DTRACE_BADADDR) ? DTRACEFLT_BADADDR :       \
      ((flags) & CPU_DTRACE_ILLOP) ? DTRACEFLT_ILLOP :            \
      ((flags) & CPU_DTRACE_DIVZERO) ? DTRACEFLT_DIVZERO :        \
      ((flags) & CPU_DTRACE_KPRIV) ? DTRACEFLT_KPRIV :            \
      ((flags) & CPU_DTRACE_UPRIV) ? DTRACEFLT_UPRIV :            \
      ((flags) & CPU_DTRACE_TUPOFLOW) ?  DTRACEFLT_TUPOFLOW :           \
      ((flags) & CPU_DTRACE_BADALIGN) ?  DTRACEFLT_BADALIGN :           \
      ((flags) & CPU_DTRACE_NOSCRATCH) ?  DTRACEFLT_NOSCRATCH :   \
      ((flags) & CPU_DTRACE_BADSTACK) ?  DTRACEFLT_BADSTACK :           \
      DTRACEFLT_UNKNOWN)

#define     DTRACEACT_ISSTRING(act)                               \
      ((act)->dta_kind == DTRACEACT_DIFEXPR &&              \
      (act)->dta_difo->dtdo_rtype.dtdt_kind == DIF_TYPE_STRING)

/* Function prototype definitions: */
static size_t dtrace_strlen(const char *, size_t);
static dtrace_probe_t *dtrace_probe_lookup_id(dtrace_id_t id);
static void dtrace_enabling_provide(dtrace_provider_t *);
static int dtrace_enabling_match(dtrace_enabling_t *, int *);
static void dtrace_enabling_matchall(void);
static dtrace_state_t *dtrace_anon_grab(void);
#if defined(sun)
static uint64_t dtrace_helper(int, dtrace_mstate_t *,
    dtrace_state_t *, uint64_t, uint64_t);
static dtrace_helpers_t *dtrace_helpers_create(proc_t *);
#endif
static void dtrace_buffer_drop(dtrace_buffer_t *);
static intptr_t dtrace_buffer_reserve(dtrace_buffer_t *, size_t, size_t,
    dtrace_state_t *, dtrace_mstate_t *);
static int dtrace_state_option(dtrace_state_t *, dtrace_optid_t,
    dtrace_optval_t);
static int dtrace_ecb_create_enable(dtrace_probe_t *, void *);
#if defined(sun)
static void dtrace_helper_provider_destroy(dtrace_helper_provider_t *);
#endif
uint16_t dtrace_load16(uintptr_t);
uint32_t dtrace_load32(uintptr_t);
uint64_t dtrace_load64(uintptr_t);
uint8_t dtrace_load8(uintptr_t);
void dtrace_dynvar_clean(dtrace_dstate_t *);
dtrace_dynvar_t *dtrace_dynvar(dtrace_dstate_t *, uint_t, dtrace_key_t *,
    size_t, dtrace_dynvar_op_t, dtrace_mstate_t *, dtrace_vstate_t *);
uintptr_t dtrace_dif_varstr(uintptr_t, dtrace_state_t *, dtrace_mstate_t *);

/*
 * DTrace Probe Context Functions
 *
 * These functions are called from probe context.  Because probe context is
 * any context in which C may be called, arbitrarily locks may be held,
 * interrupts may be disabled, we may be in arbitrary dispatched state, etc.
 * As a result, functions called from probe context may only call other DTrace
 * support functions -- they may not interact at all with the system at large.
 * (Note that the ASSERT macro is made probe-context safe by redefining it in
 * terms of dtrace_assfail(), a probe-context safe function.) If arbitrary
 * loads are to be performed from probe context, they _must_ be in terms of
 * the safe dtrace_load*() variants.
 *
 * Some functions in this block are not actually called from probe context;
 * for these functions, there will be a comment above the function reading
 * "Note:  not called from probe context."
 */
void
dtrace_panic(const char *format, ...)
{
      va_list alist;

      va_start(alist, format);
      dtrace_vpanic(format, alist);
      va_end(alist);
}

int
dtrace_assfail(const char *a, const char *f, int l)
{
      dtrace_panic("assertion failed: %s, file: %s, line: %d", a, f, l);

      /*
       * We just need something here that even the most clever compiler
       * cannot optimize away.
       */
      return (a[(uintptr_t)f]);
}

/*
 * Atomically increment a specified error counter from probe context.
 */
static void
dtrace_error(uint32_t *counter)
{
      /*
       * Most counters stored to in probe context are per-CPU counters.
       * However, there are some error conditions that are sufficiently
       * arcane that they don't merit per-CPU storage.  If these counters
       * are incremented concurrently on different CPUs, scalability will be
       * adversely affected -- but we don't expect them to be white-hot in a
       * correctly constructed enabling...
       */
      uint32_t oval, nval;

      do {
            oval = *counter;

            if ((nval = oval + 1) == 0) {
                  /*
                   * If the counter would wrap, set it to 1 -- assuring
                   * that the counter is never zero when we have seen
                   * errors.  (The counter must be 32-bits because we
                   * aren't guaranteed a 64-bit compare&swap operation.)
                   * To save this code both the infamy of being fingered
                   * by a priggish news story and the indignity of being
                   * the target of a neo-puritan witch trial, we're
                   * carefully avoiding any colorful description of the
                   * likelihood of this condition -- but suffice it to
                   * say that it is only slightly more likely than the
                   * overflow of predicate cache IDs, as discussed in
                   * dtrace_predicate_create().
                   */
                  nval = 1;
            }
      } while (dtrace_cas32(counter, oval, nval) != oval);
}

/*
 * Use the DTRACE_LOADFUNC macro to define functions for each of loading a
 * uint8_t, a uint16_t, a uint32_t and a uint64_t.
 */
DTRACE_LOADFUNC(8)
DTRACE_LOADFUNC(16)
DTRACE_LOADFUNC(32)
DTRACE_LOADFUNC(64)

static int
dtrace_inscratch(uintptr_t dest, size_t size, dtrace_mstate_t *mstate)
{
      if (dest < mstate->dtms_scratch_base)
            return (0);

      if (dest + size < dest)
            return (0);

      if (dest + size > mstate->dtms_scratch_ptr)
            return (0);

      return (1);
}

static int
dtrace_canstore_statvar(uint64_t addr, size_t sz,
    dtrace_statvar_t **svars, int nsvars)
{
      int i;

      for (i = 0; i < nsvars; i++) {
            dtrace_statvar_t *svar = svars[i];

            if (svar == NULL || svar->dtsv_size == 0)
                  continue;

            if (DTRACE_INRANGE(addr, sz, svar->dtsv_data, svar->dtsv_size))
                  return (1);
      }

      return (0);
}

/*
 * Check to see if the address is within a memory region to which a store may
 * be issued.  This includes the DTrace scratch areas, and any DTrace variable
 * region.  The caller of dtrace_canstore() is responsible for performing any
 * alignment checks that are needed before stores are actually executed.
 */
static int
dtrace_canstore(uint64_t addr, size_t sz, dtrace_mstate_t *mstate,
    dtrace_vstate_t *vstate)
{
      /*
       * First, check to see if the address is in scratch space...
       */
      if (DTRACE_INRANGE(addr, sz, mstate->dtms_scratch_base,
          mstate->dtms_scratch_size))
            return (1);

      /*
       * Now check to see if it's a dynamic variable.  This check will pick
       * up both thread-local variables and any global dynamically-allocated
       * variables.
       */
      if (DTRACE_INRANGE(addr, sz, (uintptr_t)vstate->dtvs_dynvars.dtds_base,
          vstate->dtvs_dynvars.dtds_size)) {
            dtrace_dstate_t *dstate = &vstate->dtvs_dynvars;
            uintptr_t base = (uintptr_t)dstate->dtds_base +
                (dstate->dtds_hashsize * sizeof (dtrace_dynhash_t));
            uintptr_t chunkoffs;

            /*
             * Before we assume that we can store here, we need to make
             * sure that it isn't in our metadata -- storing to our
             * dynamic variable metadata would corrupt our state.  For
             * the range to not include any dynamic variable metadata,
             * it must:
             *
             *    (1) Start above the hash table that is at the base of
             *    the dynamic variable space
             *
             *    (2) Have a starting chunk offset that is beyond the
             *    dtrace_dynvar_t that is at the base of every chunk
             *
             *    (3) Not span a chunk boundary
             *
             */
            if (addr < base)
                  return (0);

            chunkoffs = (addr - base) % dstate->dtds_chunksize;

            if (chunkoffs < sizeof (dtrace_dynvar_t))
                  return (0);

            if (chunkoffs + sz > dstate->dtds_chunksize)
                  return (0);

            return (1);
      }

      /*
       * Finally, check the static local and global variables.  These checks
       * take the longest, so we perform them last.
       */
      if (dtrace_canstore_statvar(addr, sz,
          vstate->dtvs_locals, vstate->dtvs_nlocals))
            return (1);

      if (dtrace_canstore_statvar(addr, sz,
          vstate->dtvs_globals, vstate->dtvs_nglobals))
            return (1);

      return (0);
}


/*
 * Convenience routine to check to see if the address is within a memory
 * region in which a load may be issued given the user's privilege level;
 * if not, it sets the appropriate error flags and loads 'addr' into the
 * illegal value slot.
 *
 * DTrace subroutines (DIF_SUBR_*) should use this helper to implement
 * appropriate memory access protection.
 */
static int
dtrace_canload(uint64_t addr, size_t sz, dtrace_mstate_t *mstate,
    dtrace_vstate_t *vstate)
{
      volatile uintptr_t *illval = &cpu_core[curcpu].cpuc_dtrace_illval;

      /*
       * If we hold the privilege to read from kernel memory, then
       * everything is readable.
       */
      if ((mstate->dtms_access & DTRACE_ACCESS_KERNEL) != 0)
            return (1);

      /*
       * You can obviously read that which you can store.
       */
      if (dtrace_canstore(addr, sz, mstate, vstate))
            return (1);

      /*
       * We're allowed to read from our own string table.
       */
      if (DTRACE_INRANGE(addr, sz, (uintptr_t)mstate->dtms_difo->dtdo_strtab,
          mstate->dtms_difo->dtdo_strlen))
            return (1);

      DTRACE_CPUFLAG_SET(CPU_DTRACE_KPRIV);
      *illval = addr;
      return (0);
}

/*
 * Convenience routine to check to see if a given string is within a memory
 * region in which a load may be issued given the user's privilege level;
 * this exists so that we don't need to issue unnecessary dtrace_strlen()
 * calls in the event that the user has all privileges.
 */
static int
dtrace_strcanload(uint64_t addr, size_t sz, dtrace_mstate_t *mstate,
    dtrace_vstate_t *vstate)
{
      size_t strsz;

      /*
       * If we hold the privilege to read from kernel memory, then
       * everything is readable.
       */
      if ((mstate->dtms_access & DTRACE_ACCESS_KERNEL) != 0)
            return (1);

      strsz = 1 + dtrace_strlen((char *)(uintptr_t)addr, sz);
      if (dtrace_canload(addr, strsz, mstate, vstate))
            return (1);

      return (0);
}

/*
 * Convenience routine to check to see if a given variable is within a memory
 * region in which a load may be issued given the user's privilege level.
 */
static int
dtrace_vcanload(void *src, dtrace_diftype_t *type, dtrace_mstate_t *mstate,
    dtrace_vstate_t *vstate)
{
      size_t sz;
      ASSERT(type->dtdt_flags & DIF_TF_BYREF);

      /*
       * If we hold the privilege to read from kernel memory, then
       * everything is readable.
       */
      if ((mstate->dtms_access & DTRACE_ACCESS_KERNEL) != 0)
            return (1);

      if (type->dtdt_kind == DIF_TYPE_STRING)
            sz = dtrace_strlen(src,
                vstate->dtvs_state->dts_options[DTRACEOPT_STRSIZE]) + 1;
      else
            sz = type->dtdt_size;

      return (dtrace_canload((uintptr_t)src, sz, mstate, vstate));
}

/*
 * Compare two strings using safe loads.
 */
static int
dtrace_strncmp(char *s1, char *s2, size_t limit)
{
      uint8_t c1, c2;
      volatile uint16_t *flags;

      if (s1 == s2 || limit == 0)
            return (0);

      flags = (volatile uint16_t *)&cpu_core[curcpu].cpuc_dtrace_flags;

      do {
            if (s1 == NULL) {
                  c1 = '\0';
            } else {
                  c1 = dtrace_load8((uintptr_t)s1++);
            }

            if (s2 == NULL) {
                  c2 = '\0';
            } else {
                  c2 = dtrace_load8((uintptr_t)s2++);
            }

            if (c1 != c2)
                  return (c1 - c2);
      } while (--limit && c1 != '\0' && !(*flags & CPU_DTRACE_FAULT));

      return (0);
}

/*
 * Compute strlen(s) for a string using safe memory accesses.  The additional
 * len parameter is used to specify a maximum length to ensure completion.
 */
static size_t
dtrace_strlen(const char *s, size_t lim)
{
      uint_t len;

      for (len = 0; len != lim; len++) {
            if (dtrace_load8((uintptr_t)s++) == '\0')
                  break;
      }

      return (len);
}

/*
 * Check if an address falls within a toxic region.
 */
static int
dtrace_istoxic(uintptr_t kaddr, size_t size)
{
      uintptr_t taddr, tsize;
      int i;

      for (i = 0; i < dtrace_toxranges; i++) {
            taddr = dtrace_toxrange[i].dtt_base;
            tsize = dtrace_toxrange[i].dtt_limit - taddr;

            if (kaddr - taddr < tsize) {
                  DTRACE_CPUFLAG_SET(CPU_DTRACE_BADADDR);
                  cpu_core[curcpu].cpuc_dtrace_illval = kaddr;
                  return (1);
            }

            if (taddr - kaddr < size) {
                  DTRACE_CPUFLAG_SET(CPU_DTRACE_BADADDR);
                  cpu_core[curcpu].cpuc_dtrace_illval = taddr;
                  return (1);
            }
      }

      return (0);
}

/*
 * Copy src to dst using safe memory accesses.  The src is assumed to be unsafe
 * memory specified by the DIF program.  The dst is assumed to be safe memory
 * that we can store to directly because it is managed by DTrace.  As with
 * standard bcopy, overlapping copies are handled properly.
 */
static void
dtrace_bcopy(const void *src, void *dst, size_t len)
{
      if (len != 0) {
            uint8_t *s1 = dst;
            const uint8_t *s2 = src;

            if (s1 <= s2) {
                  do {
                        *s1++ = dtrace_load8((uintptr_t)s2++);
                  } while (--len != 0);
            } else {
                  s2 += len;
                  s1 += len;

                  do {
                        *--s1 = dtrace_load8((uintptr_t)--s2);
                  } while (--len != 0);
            }
      }
}

/*
 * Copy src to dst using safe memory accesses, up to either the specified
 * length, or the point that a nul byte is encountered.  The src is assumed to
 * be unsafe memory specified by the DIF program.  The dst is assumed to be
 * safe memory that we can store to directly because it is managed by DTrace.
 * Unlike dtrace_bcopy(), overlapping regions are not handled.
 */
static void
dtrace_strcpy(const void *src, void *dst, size_t len)
{
      if (len != 0) {
            uint8_t *s1 = dst, c;
            const uint8_t *s2 = src;

            do {
                  *s1++ = c = dtrace_load8((uintptr_t)s2++);
            } while (--len != 0 && c != '\0');
      }
}

/*
 * Copy src to dst, deriving the size and type from the specified (BYREF)
 * variable type.  The src is assumed to be unsafe memory specified by the DIF
 * program.  The dst is assumed to be DTrace variable memory that is of the
 * specified type; we assume that we can store to directly.
 */
static void
dtrace_vcopy(void *src, void *dst, dtrace_diftype_t *type)
{
      ASSERT(type->dtdt_flags & DIF_TF_BYREF);

      if (type->dtdt_kind == DIF_TYPE_STRING) {
            dtrace_strcpy(src, dst, type->dtdt_size);
      } else {
            dtrace_bcopy(src, dst, type->dtdt_size);
      }
}

/*
 * Compare s1 to s2 using safe memory accesses.  The s1 data is assumed to be
 * unsafe memory specified by the DIF program.  The s2 data is assumed to be
 * safe memory that we can access directly because it is managed by DTrace.
 */
static int
dtrace_bcmp(const void *s1, const void *s2, size_t len)
{
      volatile uint16_t *flags;

      flags = (volatile uint16_t *)&cpu_core[curcpu].cpuc_dtrace_flags;

      if (s1 == s2)
            return (0);

      if (s1 == NULL || s2 == NULL)
            return (1);

      if (s1 != s2 && len != 0) {
            const uint8_t *ps1 = s1;
            const uint8_t *ps2 = s2;

            do {
                  if (dtrace_load8((uintptr_t)ps1++) != *ps2++)
                        return (1);
            } while (--len != 0 && !(*flags & CPU_DTRACE_FAULT));
      }
      return (0);
}

/*
 * Zero the specified region using a simple byte-by-byte loop.  Note that this
 * is for safe DTrace-managed memory only.
 */
static void
dtrace_bzero(void *dst, size_t len)
{
      uchar_t *cp;

      for (cp = dst; len != 0; len--)
            *cp++ = 0;
}

static void
dtrace_add_128(uint64_t *addend1, uint64_t *addend2, uint64_t *sum)
{
      uint64_t result[2];

      result[0] = addend1[0] + addend2[0];
      result[1] = addend1[1] + addend2[1] +
          (result[0] < addend1[0] || result[0] < addend2[0] ? 1 : 0);

      sum[0] = result[0];
      sum[1] = result[1];
}

/*
 * Shift the 128-bit value in a by b. If b is positive, shift left.
 * If b is negative, shift right.
 */
static void
dtrace_shift_128(uint64_t *a, int b)
{
      uint64_t mask;

      if (b == 0)
            return;

      if (b < 0) {
            b = -b;
            if (b >= 64) {
                  a[0] = a[1] >> (b - 64);
                  a[1] = 0;
            } else {
                  a[0] >>= b;
                  mask = 1LL << (64 - b);
                  mask -= 1;
                  a[0] |= ((a[1] & mask) << (64 - b));
                  a[1] >>= b;
            }
      } else {
            if (b >= 64) {
                  a[1] = a[0] << (b - 64);
                  a[0] = 0;
            } else {
                  a[1] <<= b;
                  mask = a[0] >> (64 - b);
                  a[1] |= mask;
                  a[0] <<= b;
            }
      }
}

/*
 * The basic idea is to break the 2 64-bit values into 4 32-bit values,
 * use native multiplication on those, and then re-combine into the
 * resulting 128-bit value.
 *
 * (hi1 << 32 + lo1) * (hi2 << 32 + lo2) =
 *     hi1 * hi2 << 64 +
 *     hi1 * lo2 << 32 +
 *     hi2 * lo1 << 32 +
 *     lo1 * lo2
 */
static void
dtrace_multiply_128(uint64_t factor1, uint64_t factor2, uint64_t *product)
{
      uint64_t hi1, hi2, lo1, lo2;
      uint64_t tmp[2];

      hi1 = factor1 >> 32;
      hi2 = factor2 >> 32;

      lo1 = factor1 & DT_MASK_LO;
      lo2 = factor2 & DT_MASK_LO;

      product[0] = lo1 * lo2;
      product[1] = hi1 * hi2;

      tmp[0] = hi1 * lo2;
      tmp[1] = 0;
      dtrace_shift_128(tmp, 32);
      dtrace_add_128(product, tmp, product);

      tmp[0] = hi2 * lo1;
      tmp[1] = 0;
      dtrace_shift_128(tmp, 32);
      dtrace_add_128(product, tmp, product);
}

/*
 * This privilege check should be used by actions and subroutines to
 * verify that the user credentials of the process that enabled the
 * invoking ECB match the target credentials
 */
static int
dtrace_priv_proc_common_user(dtrace_state_t *state)
{
      cred_t *cr, *s_cr = state->dts_cred.dcr_cred;

      /*
       * We should always have a non-NULL state cred here, since if cred
       * is null (anonymous tracing), we fast-path bypass this routine.
       */
      ASSERT(s_cr != NULL);

      if ((cr = CRED()) != NULL &&
          s_cr->cr_uid == cr->cr_uid &&
          s_cr->cr_uid == cr->cr_ruid &&
          s_cr->cr_uid == cr->cr_suid &&
          s_cr->cr_gid == cr->cr_gid &&
          s_cr->cr_gid == cr->cr_rgid &&
          s_cr->cr_gid == cr->cr_sgid)
            return (1);

      return (0);
}

/*
 * This privilege check should be used by actions and subroutines to
 * verify that the zone of the process that enabled the invoking ECB
 * matches the target credentials
 */
static int
dtrace_priv_proc_common_zone(dtrace_state_t *state)
{
#if defined(sun)
      cred_t *cr, *s_cr = state->dts_cred.dcr_cred;

      /*
       * We should always have a non-NULL state cred here, since if cred
       * is null (anonymous tracing), we fast-path bypass this routine.
       */
      ASSERT(s_cr != NULL);

      if ((cr = CRED()) != NULL &&
          s_cr->cr_zone == cr->cr_zone)
            return (1);

      return (0);
#else
      return (1);
#endif
}

/*
 * This privilege check should be used by actions and subroutines to
 * verify that the process has not setuid or changed credentials.
 */
static int
dtrace_priv_proc_common_nocd(void)
{
      proc_t *proc;

      if ((proc = ttoproc(curthread)) != NULL &&
          !(proc->p_flag & SNOCD))
            return (1);

      return (0);
}

static int
dtrace_priv_proc_destructive(dtrace_state_t *state)
{
      int action = state->dts_cred.dcr_action;

      if (((action & DTRACE_CRA_PROC_DESTRUCTIVE_ALLZONE) == 0) &&
          dtrace_priv_proc_common_zone(state) == 0)
            goto bad;

      if (((action & DTRACE_CRA_PROC_DESTRUCTIVE_ALLUSER) == 0) &&
          dtrace_priv_proc_common_user(state) == 0)
            goto bad;

      if (((action & DTRACE_CRA_PROC_DESTRUCTIVE_CREDCHG) == 0) &&
          dtrace_priv_proc_common_nocd() == 0)
            goto bad;

      return (1);

bad:
      cpu_core[curcpu].cpuc_dtrace_flags |= CPU_DTRACE_UPRIV;

      return (0);
}

static int
dtrace_priv_proc_control(dtrace_state_t *state)
{
      if (state->dts_cred.dcr_action & DTRACE_CRA_PROC_CONTROL)
            return (1);

      if (dtrace_priv_proc_common_zone(state) &&
          dtrace_priv_proc_common_user(state) &&
          dtrace_priv_proc_common_nocd())
            return (1);

      cpu_core[curcpu].cpuc_dtrace_flags |= CPU_DTRACE_UPRIV;

      return (0);
}

static int
dtrace_priv_proc(dtrace_state_t *state)
{
      if (state->dts_cred.dcr_action & DTRACE_CRA_PROC)
            return (1);

      cpu_core[curcpu].cpuc_dtrace_flags |= CPU_DTRACE_UPRIV;

      return (0);
}

static int
dtrace_priv_kernel(dtrace_state_t *state)
{
      if (state->dts_cred.dcr_action & DTRACE_CRA_KERNEL)
            return (1);

      cpu_core[curcpu].cpuc_dtrace_flags |= CPU_DTRACE_KPRIV;

      return (0);
}

static int
dtrace_priv_kernel_destructive(dtrace_state_t *state)
{
      if (state->dts_cred.dcr_action & DTRACE_CRA_KERNEL_DESTRUCTIVE)
            return (1);

      cpu_core[curcpu].cpuc_dtrace_flags |= CPU_DTRACE_KPRIV;

      return (0);
}

/*
 * Note:  not called from probe context.  This function is called
 * asynchronously (and at a regular interval) from outside of probe context to
 * clean the dirty dynamic variable lists on all CPUs.  Dynamic variable
 * cleaning is explained in detail in <sys/dtrace_impl.h>.
 */
void
dtrace_dynvar_clean(dtrace_dstate_t *dstate)
{
      dtrace_dynvar_t *dirty;
      dtrace_dstate_percpu_t *dcpu;
      int i, work = 0;

      for (i = 0; i < NCPU; i++) {
            dcpu = &dstate->dtds_percpu[i];

            ASSERT(dcpu->dtdsc_rinsing == NULL);

            /*
             * If the dirty list is NULL, there is no dirty work to do.
             */
            if (dcpu->dtdsc_dirty == NULL)
                  continue;

            /*
             * If the clean list is non-NULL, then we're not going to do
             * any work for this CPU -- it means that there has not been
             * a dtrace_dynvar() allocation on this CPU (or from this CPU)
             * since the last time we cleaned house.
             */
            if (dcpu->dtdsc_clean != NULL)
                  continue;

            work = 1;

            /*
             * Atomically move the dirty list aside.
             */
            do {
                  dirty = dcpu->dtdsc_dirty;

                  /*
                   * Before we zap the dirty list, set the rinsing list.
                   * (This allows for a potential assertion in
                   * dtrace_dynvar():  if a free dynamic variable appears
                   * on a hash chain, either the dirty list or the
                   * rinsing list for some CPU must be non-NULL.)
                   */
                  dcpu->dtdsc_rinsing = dirty;
                  dtrace_membar_producer();
            } while (dtrace_casptr(&dcpu->dtdsc_dirty,
                dirty, NULL) != dirty);
      }

      if (!work) {
            /*
             * We have no work to do; we can simply return.
             */
            return;
      }

      dtrace_sync();

      for (i = 0; i < NCPU; i++) {
            dcpu = &dstate->dtds_percpu[i];

            if (dcpu->dtdsc_rinsing == NULL)
                  continue;

            /*
             * We are now guaranteed that no hash chain contains a pointer
             * into this dirty list; we can make it clean.
             */
            ASSERT(dcpu->dtdsc_clean == NULL);
            dcpu->dtdsc_clean = dcpu->dtdsc_rinsing;
            dcpu->dtdsc_rinsing = NULL;
      }

      /*
       * Before we actually set the state to be DTRACE_DSTATE_CLEAN, make
       * sure that all CPUs have seen all of the dtdsc_clean pointers.
       * This prevents a race whereby a CPU incorrectly decides that
       * the state should be something other than DTRACE_DSTATE_CLEAN
       * after dtrace_dynvar_clean() has completed.
       */
      dtrace_sync();

      dstate->dtds_state = DTRACE_DSTATE_CLEAN;
}

/*
 * Depending on the value of the op parameter, this function looks-up,
 * allocates or deallocates an arbitrarily-keyed dynamic variable.  If an
 * allocation is requested, this function will return a pointer to a
 * dtrace_dynvar_t corresponding to the allocated variable -- or NULL if no
 * variable can be allocated.  If NULL is returned, the appropriate counter
 * will be incremented.
 */
dtrace_dynvar_t *
dtrace_dynvar(dtrace_dstate_t *dstate, uint_t nkeys,
    dtrace_key_t *key, size_t dsize, dtrace_dynvar_op_t op,
    dtrace_mstate_t *mstate, dtrace_vstate_t *vstate)
{
      uint64_t hashval = DTRACE_DYNHASH_VALID;
      dtrace_dynhash_t *hash = dstate->dtds_hash;
      dtrace_dynvar_t *free, *new_free, *next, *dvar, *start, *prev = NULL;
      processorid_t me = curcpu, cpu = me;
      dtrace_dstate_percpu_t *dcpu = &dstate->dtds_percpu[me];
      size_t bucket, ksize;
      size_t chunksize = dstate->dtds_chunksize;
      uintptr_t kdata, lock, nstate;
      uint_t i;

      ASSERT(nkeys != 0);

      /*
       * Hash the key.  As with aggregations, we use Jenkins' "One-at-a-time"
       * algorithm.  For the by-value portions, we perform the algorithm in
       * 16-bit chunks (as opposed to 8-bit chunks).  This speeds things up a
       * bit, and seems to have only a minute effect on distribution.  For
       * the by-reference data, we perform "One-at-a-time" iterating (safely)
       * over each referenced byte.  It's painful to do this, but it's much
       * better than pathological hash distribution.  The efficacy of the
       * hashing algorithm (and a comparison with other algorithms) may be
       * found by running the ::dtrace_dynstat MDB dcmd.
       */
      for (i = 0; i < nkeys; i++) {
            if (key[i].dttk_size == 0) {
                  uint64_t val = key[i].dttk_value;

                  hashval += (val >> 48) & 0xffff;
                  hashval += (hashval << 10);
                  hashval ^= (hashval >> 6);

                  hashval += (val >> 32) & 0xffff;
                  hashval += (hashval << 10);
                  hashval ^= (hashval >> 6);

                  hashval += (val >> 16) & 0xffff;
                  hashval += (hashval << 10);
                  hashval ^= (hashval >> 6);

                  hashval += val & 0xffff;
                  hashval += (hashval << 10);
                  hashval ^= (hashval >> 6);
            } else {
                  /*
                   * This is incredibly painful, but it beats the hell
                   * out of the alternative.
                   */
                  uint64_t j, size = key[i].dttk_size;
                  uintptr_t base = (uintptr_t)key[i].dttk_value;

                  if (!dtrace_canload(base, size, mstate, vstate))
                        break;

                  for (j = 0; j < size; j++) {
                        hashval += dtrace_load8(base + j);
                        hashval += (hashval << 10);
                        hashval ^= (hashval >> 6);
                  }
            }
      }

      if (DTRACE_CPUFLAG_ISSET(CPU_DTRACE_FAULT))
            return (NULL);

      hashval += (hashval << 3);
      hashval ^= (hashval >> 11);
      hashval += (hashval << 15);

      /*
       * There is a remote chance (ideally, 1 in 2^31) that our hashval
       * comes out to be one of our two sentinel hash values.  If this
       * actually happens, we set the hashval to be a value known to be a
       * non-sentinel value.
       */
      if (hashval == DTRACE_DYNHASH_FREE || hashval == DTRACE_DYNHASH_SINK)
            hashval = DTRACE_DYNHASH_VALID;

      /*
       * Yes, it's painful to do a divide here.  If the cycle count becomes
       * important here, tricks can be pulled to reduce it.  (However, it's
       * critical that hash collisions be kept to an absolute minimum;
       * they're much more painful than a divide.)  It's better to have a
       * solution that generates few collisions and still keeps things
       * relatively simple.
       */
      bucket = hashval % dstate->dtds_hashsize;

      if (op == DTRACE_DYNVAR_DEALLOC) {
            volatile uintptr_t *lockp = &hash[bucket].dtdh_lock;

            for (;;) {
                  while ((lock = *lockp) & 1)
                        continue;

                  if (dtrace_casptr((volatile void *)lockp,
                      (volatile void *)lock, (volatile void *)(lock + 1)) == (void *)lock)
                        break;
            }

            dtrace_membar_producer();
      }

top:
      prev = NULL;
      lock = hash[bucket].dtdh_lock;

      dtrace_membar_consumer();

      start = hash[bucket].dtdh_chain;
      ASSERT(start != NULL && (start->dtdv_hashval == DTRACE_DYNHASH_SINK ||
          start->dtdv_hashval != DTRACE_DYNHASH_FREE ||
          op != DTRACE_DYNVAR_DEALLOC));

      for (dvar = start; dvar != NULL; dvar = dvar->dtdv_next) {
            dtrace_tuple_t *dtuple = &dvar->dtdv_tuple;
            dtrace_key_t *dkey = &dtuple->dtt_key[0];

            if (dvar->dtdv_hashval != hashval) {
                  if (dvar->dtdv_hashval == DTRACE_DYNHASH_SINK) {
                        /*
                         * We've reached the sink, and therefore the
                         * end of the hash chain; we can kick out of
                         * the loop knowing that we have seen a valid
                         * snapshot of state.
                         */
                        ASSERT(dvar->dtdv_next == NULL);
                        ASSERT(dvar == &dtrace_dynhash_sink);
                        break;
                  }

                  if (dvar->dtdv_hashval == DTRACE_DYNHASH_FREE) {
                        /*
                         * We've gone off the rails:  somewhere along
                         * the line, one of the members of this hash
                         * chain was deleted.  Note that we could also
                         * detect this by simply letting this loop run
                         * to completion, as we would eventually hit
                         * the end of the dirty list.  However, we
                         * want to avoid running the length of the
                         * dirty list unnecessarily (it might be quite
                         * long), so we catch this as early as
                         * possible by detecting the hash marker.  In
                         * this case, we simply set dvar to NULL and
                         * break; the conditional after the loop will
                         * send us back to top.
                         */
                        dvar = NULL;
                        break;
                  }

                  goto next;
            }

            if (dtuple->dtt_nkeys != nkeys)
                  goto next;

            for (i = 0; i < nkeys; i++, dkey++) {
                  if (dkey->dttk_size != key[i].dttk_size)
                        goto next; /* size or type mismatch */

                  if (dkey->dttk_size != 0) {
                        if (dtrace_bcmp(
                            (void *)(uintptr_t)key[i].dttk_value,
                            (void *)(uintptr_t)dkey->dttk_value,
                            dkey->dttk_size))
                              goto next;
                  } else {
                        if (dkey->dttk_value != key[i].dttk_value)
                              goto next;
                  }
            }

            if (op != DTRACE_DYNVAR_DEALLOC)
                  return (dvar);

            ASSERT(dvar->dtdv_next == NULL ||
                dvar->dtdv_next->dtdv_hashval != DTRACE_DYNHASH_FREE);

            if (prev != NULL) {
                  ASSERT(hash[bucket].dtdh_chain != dvar);
                  ASSERT(start != dvar);
                  ASSERT(prev->dtdv_next == dvar);
                  prev->dtdv_next = dvar->dtdv_next;
            } else {
                  if (dtrace_casptr(&hash[bucket].dtdh_chain,
                      start, dvar->dtdv_next) != start) {
                        /*
                         * We have failed to atomically swing the
                         * hash table head pointer, presumably because
                         * of a conflicting allocation on another CPU.
                         * We need to reread the hash chain and try
                         * again.
                         */
                        goto top;
                  }
            }

            dtrace_membar_producer();

            /*
             * Now set the hash value to indicate that it's free.
             */
            ASSERT(hash[bucket].dtdh_chain != dvar);
            dvar->dtdv_hashval = DTRACE_DYNHASH_FREE;

            dtrace_membar_producer();

            /*
             * Set the next pointer to point at the dirty list, and
             * atomically swing the dirty pointer to the newly freed dvar.
             */
            do {
                  next = dcpu->dtdsc_dirty;
                  dvar->dtdv_next = next;
            } while (dtrace_casptr(&dcpu->dtdsc_dirty, next, dvar) != next);

            /*
             * Finally, unlock this hash bucket.
             */
            ASSERT(hash[bucket].dtdh_lock == lock);
            ASSERT(lock & 1);
            hash[bucket].dtdh_lock++;

            return (NULL);
next:
            prev = dvar;
            continue;
      }

      if (dvar == NULL) {
            /*
             * If dvar is NULL, it is because we went off the rails:
             * one of the elements that we traversed in the hash chain
             * was deleted while we were traversing it.  In this case,
             * we assert that we aren't doing a dealloc (deallocs lock
             * the hash bucket to prevent themselves from racing with
             * one another), and retry the hash chain traversal.
             */
            ASSERT(op != DTRACE_DYNVAR_DEALLOC);
            goto top;
      }

      if (op != DTRACE_DYNVAR_ALLOC) {
            /*
             * If we are not to allocate a new variable, we want to
             * return NULL now.  Before we return, check that the value
             * of the lock word hasn't changed.  If it has, we may have
             * seen an inconsistent snapshot.
             */
            if (op == DTRACE_DYNVAR_NOALLOC) {
                  if (hash[bucket].dtdh_lock != lock)
                        goto top;
            } else {
                  ASSERT(op == DTRACE_DYNVAR_DEALLOC);
                  ASSERT(hash[bucket].dtdh_lock == lock);
                  ASSERT(lock & 1);
                  hash[bucket].dtdh_lock++;
            }

            return (NULL);
      }

      /*
       * We need to allocate a new dynamic variable.  The size we need is the
       * size of dtrace_dynvar plus the size of nkeys dtrace_key_t's plus the
       * size of any auxiliary key data (rounded up to 8-byte alignment) plus
       * the size of any referred-to data (dsize).  We then round the final
       * size up to the chunksize for allocation.
       */
      for (ksize = 0, i = 0; i < nkeys; i++)
            ksize += P2ROUNDUP(key[i].dttk_size, sizeof (uint64_t));

      /*
       * This should be pretty much impossible, but could happen if, say,
       * strange DIF specified the tuple.  Ideally, this should be an
       * assertion and not an error condition -- but that requires that the
       * chunksize calculation in dtrace_difo_chunksize() be absolutely
       * bullet-proof.  (That is, it must not be able to be fooled by
       * malicious DIF.)  Given the lack of backwards branches in DIF,
       * solving this would presumably not amount to solving the Halting
       * Problem -- but it still seems awfully hard.
       */
      if (sizeof (dtrace_dynvar_t) + sizeof (dtrace_key_t) * (nkeys - 1) +
          ksize + dsize > chunksize) {
            dcpu->dtdsc_drops++;
            return (NULL);
      }

      nstate = DTRACE_DSTATE_EMPTY;

      do {
retry:
            free = dcpu->dtdsc_free;

            if (free == NULL) {
                  dtrace_dynvar_t *clean = dcpu->dtdsc_clean;
                  void *rval;

                  if (clean == NULL) {
                        /*
                         * We're out of dynamic variable space on
                         * this CPU.  Unless we have tried all CPUs,
                         * we'll try to allocate from a different
                         * CPU.
                         */
                        switch (dstate->dtds_state) {
                        case DTRACE_DSTATE_CLEAN: {
                              void *sp = &dstate->dtds_state;

                              if (++cpu >= NCPU)
                                    cpu = 0;

                              if (dcpu->dtdsc_dirty != NULL &&
                                  nstate == DTRACE_DSTATE_EMPTY)
                                    nstate = DTRACE_DSTATE_DIRTY;

                              if (dcpu->dtdsc_rinsing != NULL)
                                    nstate = DTRACE_DSTATE_RINSING;

                              dcpu = &dstate->dtds_percpu[cpu];

                              if (cpu != me)
                                    goto retry;

                              (void) dtrace_cas32(sp,
                                  DTRACE_DSTATE_CLEAN, nstate);

                              /*
                               * To increment the correct bean
                               * counter, take another lap.
                               */
                              goto retry;
                        }

                        case DTRACE_DSTATE_DIRTY:
                              dcpu->dtdsc_dirty_drops++;
                              break;

                        case DTRACE_DSTATE_RINSING:
                              dcpu->dtdsc_rinsing_drops++;
                              break;

                        case DTRACE_DSTATE_EMPTY:
                              dcpu->dtdsc_drops++;
                              break;
                        }

                        DTRACE_CPUFLAG_SET(CPU_DTRACE_DROP);
                        return (NULL);
                  }

                  /*
                   * The clean list appears to be non-empty.  We want to
                   * move the clean list to the free list; we start by
                   * moving the clean pointer aside.
                   */
                  if (dtrace_casptr(&dcpu->dtdsc_clean,
                      clean, NULL) != clean) {
                        /*
                         * We are in one of two situations:
                         *
                         *  (a)     The clean list was switched to the
                         *    free list by another CPU.
                         *
                         *  (b)     The clean list was added to by the
                         *    cleansing cyclic.
                         *
                         * In either of these situations, we can
                         * just reattempt the free list allocation.
                         */
                        goto retry;
                  }

                  ASSERT(clean->dtdv_hashval == DTRACE_DYNHASH_FREE);

                  /*
                   * Now we'll move the clean list to the free list.
                   * It's impossible for this to fail:  the only way
                   * the free list can be updated is through this
                   * code path, and only one CPU can own the clean list.
                   * Thus, it would only be possible for this to fail if
                   * this code were racing with dtrace_dynvar_clean().
                   * (That is, if dtrace_dynvar_clean() updated the clean
                   * list, and we ended up racing to update the free
                   * list.)  This race is prevented by the dtrace_sync()
                   * in dtrace_dynvar_clean() -- which flushes the
                   * owners of the clean lists out before resetting
                   * the clean lists.
                   */
                  rval = dtrace_casptr(&dcpu->dtdsc_free, NULL, clean);
                  ASSERT(rval == NULL);
                  goto retry;
            }

            dvar = free;
            new_free = dvar->dtdv_next;
      } while (dtrace_casptr(&dcpu->dtdsc_free, free, new_free) != free);

      /*
       * We have now allocated a new chunk.  We copy the tuple keys into the
       * tuple array and copy any referenced key data into the data space
       * following the tuple array.  As we do this, we relocate dttk_value
       * in the final tuple to point to the key data address in the chunk.
       */
      kdata = (uintptr_t)&dvar->dtdv_tuple.dtt_key[nkeys];
      dvar->dtdv_data = (void *)(kdata + ksize);
      dvar->dtdv_tuple.dtt_nkeys = nkeys;

      for (i = 0; i < nkeys; i++) {
            dtrace_key_t *dkey = &dvar->dtdv_tuple.dtt_key[i];
            size_t kesize = key[i].dttk_size;

            if (kesize != 0) {
                  dtrace_bcopy(
                      (const void *)(uintptr_t)key[i].dttk_value,
                      (void *)kdata, kesize);
                  dkey->dttk_value = kdata;
                  kdata += P2ROUNDUP(kesize, sizeof (uint64_t));
            } else {
                  dkey->dttk_value = key[i].dttk_value;
            }

            dkey->dttk_size = kesize;
      }

      ASSERT(dvar->dtdv_hashval == DTRACE_DYNHASH_FREE);
      dvar->dtdv_hashval = hashval;
      dvar->dtdv_next = start;

      if (dtrace_casptr(&hash[bucket].dtdh_chain, start, dvar) == start)
            return (dvar);

      /*
       * The cas has failed.  Either another CPU is adding an element to
       * this hash chain, or another CPU is deleting an element from this
       * hash chain.  The simplest way to deal with both of these cases
       * (though not necessarily the most efficient) is to free our
       * allocated block and tail-call ourselves.  Note that the free is
       * to the dirty list and _not_ to the free list.  This is to prevent
       * races with allocators, above.
       */
      dvar->dtdv_hashval = DTRACE_DYNHASH_FREE;

      dtrace_membar_producer();

      do {
            free = dcpu->dtdsc_dirty;
            dvar->dtdv_next = free;
      } while (dtrace_casptr(&dcpu->dtdsc_dirty, free, dvar) != free);

      return (dtrace_dynvar(dstate, nkeys, key, dsize, op, mstate, vstate));
}

/*ARGSUSED*/
static void
dtrace_aggregate_min(uint64_t *oval, uint64_t nval, uint64_t arg)
{
      if ((int64_t)nval < (int64_t)*oval)
            *oval = nval;
}

/*ARGSUSED*/
static void
dtrace_aggregate_max(uint64_t *oval, uint64_t nval, uint64_t arg)
{
      if ((int64_t)nval > (int64_t)*oval)
            *oval = nval;
}

static void
dtrace_aggregate_quantize(uint64_t *quanta, uint64_t nval, uint64_t incr)
{
      int i, zero = DTRACE_QUANTIZE_ZEROBUCKET;
      int64_t val = (int64_t)nval;

      if (val < 0) {
            for (i = 0; i < zero; i++) {
                  if (val <= DTRACE_QUANTIZE_BUCKETVAL(i)) {
                        quanta[i] += incr;
                        return;
                  }
            }
      } else {
            for (i = zero + 1; i < DTRACE_QUANTIZE_NBUCKETS; i++) {
                  if (val < DTRACE_QUANTIZE_BUCKETVAL(i)) {
                        quanta[i - 1] += incr;
                        return;
                  }
            }

            quanta[DTRACE_QUANTIZE_NBUCKETS - 1] += incr;
            return;
      }

      ASSERT(0);
}

static void
dtrace_aggregate_lquantize(uint64_t *lquanta, uint64_t nval, uint64_t incr)
{
      uint64_t arg = *lquanta++;
      int32_t base = DTRACE_LQUANTIZE_BASE(arg);
      uint16_t step = DTRACE_LQUANTIZE_STEP(arg);
      uint16_t levels = DTRACE_LQUANTIZE_LEVELS(arg);
      int32_t val = (int32_t)nval, level;

      ASSERT(step != 0);
      ASSERT(levels != 0);

      if (val < base) {
            /*
             * This is an underflow.
             */
            lquanta[0] += incr;
            return;
      }

      level = (val - base) / step;

      if (level < levels) {
            lquanta[level + 1] += incr;
            return;
      }

      /*
       * This is an overflow.
       */
      lquanta[levels + 1] += incr;
}

/*ARGSUSED*/
static void
dtrace_aggregate_avg(uint64_t *data, uint64_t nval, uint64_t arg)
{
      data[0]++;
      data[1] += nval;
}

/*ARGSUSED*/
static void
dtrace_aggregate_stddev(uint64_t *data, uint64_t nval, uint64_t arg)
{
      int64_t snval = (int64_t)nval;
      uint64_t tmp[2];

      data[0]++;
      data[1] += nval;

      /*
       * What we want to say here is:
       *
       * data[2] += nval * nval;
       *
       * But given that nval is 64-bit, we could easily overflow, so
       * we do this as 128-bit arithmetic.
       */
      if (snval < 0)
            snval = -snval;

      dtrace_multiply_128((uint64_t)snval, (uint64_t)snval, tmp);
      dtrace_add_128(data + 2, tmp, data + 2);
}

/*ARGSUSED*/
static void
dtrace_aggregate_count(uint64_t *oval, uint64_t nval, uint64_t arg)
{
      *oval = *oval + 1;
}

/*ARGSUSED*/
static void
dtrace_aggregate_sum(uint64_t *oval, uint64_t nval, uint64_t arg)
{
      *oval += nval;
}

/*
 * Aggregate given the tuple in the principal data buffer, and the aggregating
 * action denoted by the specified dtrace_aggregation_t.  The aggregation
 * buffer is specified as the buf parameter.  This routine does not return
 * failure; if there is no space in the aggregation buffer, the data will be
 * dropped, and a corresponding counter incremented.
 */
static void
dtrace_aggregate(dtrace_aggregation_t *agg, dtrace_buffer_t *dbuf,
    intptr_t offset, dtrace_buffer_t *buf, uint64_t expr, uint64_t arg)
{
      dtrace_recdesc_t *rec = &agg->dtag_action.dta_rec;
      uint32_t i, ndx, size, fsize;
      uint32_t align = sizeof (uint64_t) - 1;
      dtrace_aggbuffer_t *agb;
      dtrace_aggkey_t *key;
      uint32_t hashval = 0, limit, isstr;
      caddr_t tomax, data, kdata;
      dtrace_actkind_t action;
      dtrace_action_t *act;
      uintptr_t offs;

      if (buf == NULL)
            return;

      if (!agg->dtag_hasarg) {
            /*
             * Currently, only quantize() and lquantize() take additional
             * arguments, and they have the same semantics:  an increment
             * value that defaults to 1 when not present.  If additional
             * aggregating actions take arguments, the setting of the
             * default argument value will presumably have to become more
             * sophisticated...
             */
            arg = 1;
      }

      action = agg->dtag_action.dta_kind - DTRACEACT_AGGREGATION;
      size = rec->dtrd_offset - agg->dtag_base;
      fsize = size + rec->dtrd_size;

      ASSERT(dbuf->dtb_tomax != NULL);
      data = dbuf->dtb_tomax + offset + agg->dtag_base;

      if ((tomax = buf->dtb_tomax) == NULL) {
            dtrace_buffer_drop(buf);
            return;
      }

      /*
       * The metastructure is always at the bottom of the buffer.
       */
      agb = (dtrace_aggbuffer_t *)(tomax + buf->dtb_size -
          sizeof (dtrace_aggbuffer_t));

      if (buf->dtb_offset == 0) {
            /*
             * We just kludge up approximately 1/8th of the size to be
             * buckets.  If this guess ends up being routinely
             * off-the-mark, we may need to dynamically readjust this
             * based on past performance.
             */
            uintptr_t hashsize = (buf->dtb_size >> 3) / sizeof (uintptr_t);

            if ((uintptr_t)agb - hashsize * sizeof (dtrace_aggkey_t *) <
                (uintptr_t)tomax || hashsize == 0) {
                  /*
                   * We've been given a ludicrously small buffer;
                   * increment our drop count and leave.
                   */
                  dtrace_buffer_drop(buf);
                  return;
            }

            /*
             * And now, a pathetic attempt to try to get a an odd (or
             * perchance, a prime) hash size for better hash distribution.
             */
            if (hashsize > (DTRACE_AGGHASHSIZE_SLEW << 3))
                  hashsize -= DTRACE_AGGHASHSIZE_SLEW;

            agb->dtagb_hashsize = hashsize;
            agb->dtagb_hash = (dtrace_aggkey_t **)((uintptr_t)agb -
                agb->dtagb_hashsize * sizeof (dtrace_aggkey_t *));
            agb->dtagb_free = (uintptr_t)agb->dtagb_hash;

            for (i = 0; i < agb->dtagb_hashsize; i++)
                  agb->dtagb_hash[i] = NULL;
      }

      ASSERT(agg->dtag_first != NULL);
      ASSERT(agg->dtag_first->dta_intuple);

      /*
       * Calculate the hash value based on the key.  Note that we _don't_
       * include the aggid in the hashing (but we will store it as part of
       * the key).  The hashing algorithm is Bob Jenkins' "One-at-a-time"
       * algorithm: a simple, quick algorithm that has no known funnels, and
       * gets good distribution in practice.  The efficacy of the hashing
       * algorithm (and a comparison with other algorithms) may be found by
       * running the ::dtrace_aggstat MDB dcmd.
       */
      for (act = agg->dtag_first; act->dta_intuple; act = act->dta_next) {
            i = act->dta_rec.dtrd_offset - agg->dtag_base;
            limit = i + act->dta_rec.dtrd_size;
            ASSERT(limit <= size);
            isstr = DTRACEACT_ISSTRING(act);

            for (; i < limit; i++) {
                  hashval += data[i];
                  hashval += (hashval << 10);
                  hashval ^= (hashval >> 6);

                  if (isstr && data[i] == '\0')
                        break;
            }
      }

      hashval += (hashval << 3);
      hashval ^= (hashval >> 11);
      hashval += (hashval << 15);

      /*
       * Yes, the divide here is expensive -- but it's generally the least
       * of the performance issues given the amount of data that we iterate
       * over to compute hash values, compare data, etc.
       */
      ndx = hashval % agb->dtagb_hashsize;

      for (key = agb->dtagb_hash[ndx]; key != NULL; key = key->dtak_next) {
            ASSERT((caddr_t)key >= tomax);
            ASSERT((caddr_t)key < tomax + buf->dtb_size);

            if (hashval != key->dtak_hashval || key->dtak_size != size)
                  continue;

            kdata = key->dtak_data;
            ASSERT(kdata >= tomax && kdata < tomax + buf->dtb_size);

            for (act = agg->dtag_first; act->dta_intuple;
                act = act->dta_next) {
                  i = act->dta_rec.dtrd_offset - agg->dtag_base;
                  limit = i + act->dta_rec.dtrd_size;
                  ASSERT(limit <= size);
                  isstr = DTRACEACT_ISSTRING(act);

                  for (; i < limit; i++) {
                        if (kdata[i] != data[i])
                              goto next;

                        if (isstr && data[i] == '\0')
                              break;
                  }
            }

            if (action != key->dtak_action) {
                  /*
                   * We are aggregating on the same value in the same
                   * aggregation with two different aggregating actions.
                   * (This should have been picked up in the compiler,
                   * so we may be dealing with errant or devious DIF.)
                   * This is an error condition; we indicate as much,
                   * and return.
                   */
                  DTRACE_CPUFLAG_SET(CPU_DTRACE_ILLOP);
                  return;
            }

            /*
             * This is a hit:  we need to apply the aggregator to
             * the value at this key.
             */
            agg->dtag_aggregate((uint64_t *)(kdata + size), expr, arg);
            return;
next:
            continue;
      }

      /*
       * We didn't find it.  We need to allocate some zero-filled space,
       * link it into the hash table appropriately, and apply the aggregator
       * to the (zero-filled) value.
       */
      offs = buf->dtb_offset;
      while (offs & (align - 1))
            offs += sizeof (uint32_t);

      /*
       * If we don't have enough room to both allocate a new key _and_
       * its associated data, increment the drop count and return.
       */
      if ((uintptr_t)tomax + offs + fsize >
          agb->dtagb_free - sizeof (dtrace_aggkey_t)) {
            dtrace_buffer_drop(buf);
            return;
      }

      /*CONSTCOND*/
      ASSERT(!(sizeof (dtrace_aggkey_t) & (sizeof (uintptr_t) - 1)));
      key = (dtrace_aggkey_t *)(agb->dtagb_free - sizeof (dtrace_aggkey_t));
      agb->dtagb_free -= sizeof (dtrace_aggkey_t);

      key->dtak_data = kdata = tomax + offs;
      buf->dtb_offset = offs + fsize;

      /*
       * Now copy the data across.
       */
      *((dtrace_aggid_t *)kdata) = agg->dtag_id;

      for (i = sizeof (dtrace_aggid_t); i < size; i++)
            kdata[i] = data[i];

      /*
       * Because strings are not zeroed out by default, we need to iterate
       * looking for actions that store strings, and we need to explicitly
       * pad these strings out with zeroes.
       */
      for (act = agg->dtag_first; act->dta_intuple; act = act->dta_next) {
            int nul;

            if (!DTRACEACT_ISSTRING(act))
                  continue;

            i = act->dta_rec.dtrd_offset - agg->dtag_base;
            limit = i + act->dta_rec.dtrd_size;
            ASSERT(limit <= size);

            for (nul = 0; i < limit; i++) {
                  if (nul) {
                        kdata[i] = '\0';
                        continue;
                  }

                  if (data[i] != '\0')
                        continue;

                  nul = 1;
            }
      }

      for (i = size; i < fsize; i++)
            kdata[i] = 0;

      key->dtak_hashval = hashval;
      key->dtak_size = size;
      key->dtak_action = action;
      key->dtak_next = agb->dtagb_hash[ndx];
      agb->dtagb_hash[ndx] = key;

      /*
       * Finally, apply the aggregator.
       */
      *((uint64_t *)(key->dtak_data + size)) = agg->dtag_initial;
      agg->dtag_aggregate((uint64_t *)(key->dtak_data + size), expr, arg);
}

/*
 * Given consumer state, this routine finds a speculation in the INACTIVE
 * state and transitions it into the ACTIVE state.  If there is no speculation
 * in the INACTIVE state, 0 is returned.  In this case, no error counter is
 * incremented -- it is up to the caller to take appropriate action.
 */
static int
dtrace_speculation(dtrace_state_t *state)
{
      int i = 0;
      dtrace_speculation_state_t current;
      uint32_t *stat = &state->dts_speculations_unavail, count;

      while (i < state->dts_nspeculations) {
            dtrace_speculation_t *spec = &state->dts_speculations[i];

            current = spec->dtsp_state;

            if (current != DTRACESPEC_INACTIVE) {
                  if (current == DTRACESPEC_COMMITTINGMANY ||
                      current == DTRACESPEC_COMMITTING ||
                      current == DTRACESPEC_DISCARDING)
                        stat = &state->dts_speculations_busy;
                  i++;
                  continue;
            }

            if (dtrace_cas32((uint32_t *)&spec->dtsp_state,
                current, DTRACESPEC_ACTIVE) == current)
                  return (i + 1);
      }

      /*
       * We couldn't find a speculation.  If we found as much as a single
       * busy speculation buffer, we'll attribute this failure as "busy"
       * instead of "unavail".
       */
      do {
            count = *stat;
      } while (dtrace_cas32(stat, count, count + 1) != count);

      return (0);
}

/*
 * This routine commits an active speculation.  If the specified speculation
 * is not in a valid state to perform a commit(), this routine will silently do
 * nothing.  The state of the specified speculation is transitioned according
 * to the state transition diagram outlined in <sys/dtrace_impl.h>
 */
static void
dtrace_speculation_commit(dtrace_state_t *state, processorid_t cpu,
    dtrace_specid_t which)
{
      dtrace_speculation_t *spec;
      dtrace_buffer_t *src, *dest;
      uintptr_t daddr, saddr, dlimit;
      dtrace_speculation_state_t current, new = 0;
      intptr_t offs;

      if (which == 0)
            return;

      if (which > state->dts_nspeculations) {
            cpu_core[cpu].cpuc_dtrace_flags |= CPU_DTRACE_ILLOP;
            return;
      }

      spec = &state->dts_speculations[which - 1];
      src = &spec->dtsp_buffer[cpu];
      dest = &state->dts_buffer[cpu];

      do {
            current = spec->dtsp_state;

            if (current == DTRACESPEC_COMMITTINGMANY)
                  break;

            switch (current) {
            case DTRACESPEC_INACTIVE:
            case DTRACESPEC_DISCARDING:
                  return;

            case DTRACESPEC_COMMITTING:
                  /*
                   * This is only possible if we are (a) commit()'ing
                   * without having done a prior speculate() on this CPU
                   * and (b) racing with another commit() on a different
                   * CPU.  There's nothing to do -- we just assert that
                   * our offset is 0.
                   */
                  ASSERT(src->dtb_offset == 0);
                  return;

            case DTRACESPEC_ACTIVE:
                  new = DTRACESPEC_COMMITTING;
                  break;

            case DTRACESPEC_ACTIVEONE:
                  /*
                   * This speculation is active on one CPU.  If our
                   * buffer offset is non-zero, we know that the one CPU
                   * must be us.  Otherwise, we are committing on a
                   * different CPU from the speculate(), and we must
                   * rely on being asynchronously cleaned.
                   */
                  if (src->dtb_offset != 0) {
                        new = DTRACESPEC_COMMITTING;
                        break;
                  }
                  /*FALLTHROUGH*/

            case DTRACESPEC_ACTIVEMANY:
                  new = DTRACESPEC_COMMITTINGMANY;
                  break;

            default:
                  ASSERT(0);
            }
      } while (dtrace_cas32((uint32_t *)&spec->dtsp_state,
          current, new) != current);

      /*
       * We have set the state to indicate that we are committing this
       * speculation.  Now reserve the necessary space in the destination
       * buffer.
       */
      if ((offs = dtrace_buffer_reserve(dest, src->dtb_offset,
          sizeof (uint64_t), state, NULL)) < 0) {
            dtrace_buffer_drop(dest);
            goto out;
      }

      /*
       * We have the space; copy the buffer across.  (Note that this is a
       * highly subobtimal bcopy(); in the unlikely event that this becomes
       * a serious performance issue, a high-performance DTrace-specific
       * bcopy() should obviously be invented.)
       */
      daddr = (uintptr_t)dest->dtb_tomax + offs;
      dlimit = daddr + src->dtb_offset;
      saddr = (uintptr_t)src->dtb_tomax;

      /*
       * First, the aligned portion.
       */
      while (dlimit - daddr >= sizeof (uint64_t)) {
            *((uint64_t *)daddr) = *((uint64_t *)saddr);

            daddr += sizeof (uint64_t);
            saddr += sizeof (uint64_t);
      }

      /*
       * Now any left-over bit...
       */
      while (dlimit - daddr)
            *((uint8_t *)daddr++) = *((uint8_t *)saddr++);

      /*
       * Finally, commit the reserved space in the destination buffer.
       */
      dest->dtb_offset = offs + src->dtb_offset;

out:
      /*
       * If we're lucky enough to be the only active CPU on this speculation
       * buffer, we can just set the state back to DTRACESPEC_INACTIVE.
       */
      if (current == DTRACESPEC_ACTIVE ||
          (current == DTRACESPEC_ACTIVEONE && new == DTRACESPEC_COMMITTING)) {
            uint32_t rval = dtrace_cas32((uint32_t *)&spec->dtsp_state,
                DTRACESPEC_COMMITTING, DTRACESPEC_INACTIVE);

            ASSERT(rval == DTRACESPEC_COMMITTING);
      }

      src->dtb_offset = 0;
      src->dtb_xamot_drops += src->dtb_drops;
      src->dtb_drops = 0;
}

/*
 * This routine discards an active speculation.  If the specified speculation
 * is not in a valid state to perform a discard(), this routine will silently
 * do nothing.  The state of the specified speculation is transitioned
 * according to the state transition diagram outlined in <sys/dtrace_impl.h>
 */
static void
dtrace_speculation_discard(dtrace_state_t *state, processorid_t cpu,
    dtrace_specid_t which)
{
      dtrace_speculation_t *spec;
      dtrace_speculation_state_t current, new = 0;
      dtrace_buffer_t *buf;

      if (which == 0)
            return;

      if (which > state->dts_nspeculations) {
            cpu_core[cpu].cpuc_dtrace_flags |= CPU_DTRACE_ILLOP;
            return;
      }

      spec = &state->dts_speculations[which - 1];
      buf = &spec->dtsp_buffer[cpu];

      do {
            current = spec->dtsp_state;

            switch (current) {
            case DTRACESPEC_INACTIVE:
            case DTRACESPEC_COMMITTINGMANY:
            case DTRACESPEC_COMMITTING:
            case DTRACESPEC_DISCARDING:
                  return;

            case DTRACESPEC_ACTIVE:
            case DTRACESPEC_ACTIVEMANY:
                  new = DTRACESPEC_DISCARDING;
                  break;

            case DTRACESPEC_ACTIVEONE:
                  if (buf->dtb_offset != 0) {
                        new = DTRACESPEC_INACTIVE;
                  } else {
                        new = DTRACESPEC_DISCARDING;
                  }
                  break;

            default:
                  ASSERT(0);
            }
      } while (dtrace_cas32((uint32_t *)&spec->dtsp_state,
          current, new) != current);

      buf->dtb_offset = 0;
      buf->dtb_drops = 0;
}

/*
 * Note:  not called from probe context.  This function is called
 * asynchronously from cross call context to clean any speculations that are
 * in the COMMITTINGMANY or DISCARDING states.  These speculations may not be
 * transitioned back to the INACTIVE state until all CPUs have cleaned the
 * speculation.
 */
static void
dtrace_speculation_clean_here(dtrace_state_t *state)
{
      dtrace_icookie_t cookie;
      processorid_t cpu = curcpu;
      dtrace_buffer_t *dest = &state->dts_buffer[cpu];
      dtrace_specid_t i;

      cookie = dtrace_interrupt_disable();

      if (dest->dtb_tomax == NULL) {
            dtrace_interrupt_enable(cookie);
            return;
      }

      for (i = 0; i < state->dts_nspeculations; i++) {
            dtrace_speculation_t *spec = &state->dts_speculations[i];
            dtrace_buffer_t *src = &spec->dtsp_buffer[cpu];

            if (src->dtb_tomax == NULL)
                  continue;

            if (spec->dtsp_state == DTRACESPEC_DISCARDING) {
                  src->dtb_offset = 0;
                  continue;
            }

            if (spec->dtsp_state != DTRACESPEC_COMMITTINGMANY)
                  continue;

            if (src->dtb_offset == 0)
                  continue;

            dtrace_speculation_commit(state, cpu, i + 1);
      }

      dtrace_interrupt_enable(cookie);
}

/*
 * Note:  not called from probe context.  This function is called
 * asynchronously (and at a regular interval) to clean any speculations that
 * are in the COMMITTINGMANY or DISCARDING states.  If it discovers that there
 * is work to be done, it cross calls all CPUs to perform that work;
 * COMMITMANY and DISCARDING speculations may not be transitioned back to the
 * INACTIVE state until they have been cleaned by all CPUs.
 */
static void
dtrace_speculation_clean(dtrace_state_t *state)
{
      int work = 0, rv;
      dtrace_specid_t i;

      for (i = 0; i < state->dts_nspeculations; i++) {
            dtrace_speculation_t *spec = &state->dts_speculations[i];

            ASSERT(!spec->dtsp_cleaning);

            if (spec->dtsp_state != DTRACESPEC_DISCARDING &&
                spec->dtsp_state != DTRACESPEC_COMMITTINGMANY)
                  continue;

            work++;
            spec->dtsp_cleaning = 1;
      }

      if (!work)
            return;

      dtrace_xcall(DTRACE_CPUALL,
          (dtrace_xcall_t)dtrace_speculation_clean_here, state);

      /*
       * We now know that all CPUs have committed or discarded their
       * speculation buffers, as appropriate.  We can now set the state
       * to inactive.
       */
      for (i = 0; i < state->dts_nspeculations; i++) {
            dtrace_speculation_t *spec = &state->dts_speculations[i];
            dtrace_speculation_state_t current, new;

            if (!spec->dtsp_cleaning)
                  continue;

            current = spec->dtsp_state;
            ASSERT(current == DTRACESPEC_DISCARDING ||
                current == DTRACESPEC_COMMITTINGMANY);

            new = DTRACESPEC_INACTIVE;

            rv = dtrace_cas32((uint32_t *)&spec->dtsp_state, current, new);
            ASSERT(rv == current);
            spec->dtsp_cleaning = 0;
      }
}

/*
 * Called as part of a speculate() to get the speculative buffer associated
 * with a given speculation.  Returns NULL if the specified speculation is not
 * in an ACTIVE state.  If the speculation is in the ACTIVEONE state -- and
 * the active CPU is not the specified CPU -- the speculation will be
 * atomically transitioned into the ACTIVEMANY state.
 */
static dtrace_buffer_t *
dtrace_speculation_buffer(dtrace_state_t *state, processorid_t cpuid,
    dtrace_specid_t which)
{
      dtrace_speculation_t *spec;
      dtrace_speculation_state_t current, new = 0;
      dtrace_buffer_t *buf;

      if (which == 0)
            return (NULL);

      if (which > state->dts_nspeculations) {
            cpu_core[cpuid].cpuc_dtrace_flags |= CPU_DTRACE_ILLOP;
            return (NULL);
      }

      spec = &state->dts_speculations[which - 1];
      buf = &spec->dtsp_buffer[cpuid];

      do {
            current = spec->dtsp_state;

            switch (current) {
            case DTRACESPEC_INACTIVE:
            case DTRACESPEC_COMMITTINGMANY:
            case DTRACESPEC_DISCARDING:
                  return (NULL);

            case DTRACESPEC_COMMITTING:
                  ASSERT(buf->dtb_offset == 0);
                  return (NULL);

            case DTRACESPEC_ACTIVEONE:
                  /*
                   * This speculation is currently active on one CPU.
                   * Check the offset in the buffer; if it's non-zero,
                   * that CPU must be us (and we leave the state alone).
                   * If it's zero, assume that we're starting on a new
                   * CPU -- and change the state to indicate that the
                   * speculation is active on more than one CPU.
                   */
                  if (buf->dtb_offset != 0)
                        return (buf);

                  new = DTRACESPEC_ACTIVEMANY;
                  break;

            case DTRACESPEC_ACTIVEMANY:
                  return (buf);

            case DTRACESPEC_ACTIVE:
                  new = DTRACESPEC_ACTIVEONE;
                  break;

            default:
                  ASSERT(0);
            }
      } while (dtrace_cas32((uint32_t *)&spec->dtsp_state,
          current, new) != current);

      ASSERT(new == DTRACESPEC_ACTIVEONE || new == DTRACESPEC_ACTIVEMANY);
      return (buf);
}

/*
 * Return a string.  In the event that the user lacks the privilege to access
 * arbitrary kernel memory, we copy the string out to scratch memory so that we
 * don't fail access checking.
 *
 * dtrace_dif_variable() uses this routine as a helper for various
 * builtin values such as 'execname' and 'probefunc.'
 */
uintptr_t
dtrace_dif_varstr(uintptr_t addr, dtrace_state_t *state,
    dtrace_mstate_t *mstate)
{
      uint64_t size = state->dts_options[DTRACEOPT_STRSIZE];
      uintptr_t ret;
      size_t strsz;

      /*
       * The easy case: this probe is allowed to read all of memory, so
       * we can just return this as a vanilla pointer.
       */
      if ((mstate->dtms_access & DTRACE_ACCESS_KERNEL) != 0)
            return (addr);

      /*
       * This is the tougher case: we copy the string in question from
       * kernel memory into scratch memory and return it that way: this
       * ensures that we won't trip up when access checking tests the
       * BYREF return value.
       */
      strsz = dtrace_strlen((char *)addr, size) + 1;

      if (mstate->dtms_scratch_ptr + strsz >
          mstate->dtms_scratch_base + mstate->dtms_scratch_size) {
            DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
            return (0);
      }

      dtrace_strcpy((const void *)addr, (void *)mstate->dtms_scratch_ptr,
          strsz);
      ret = mstate->dtms_scratch_ptr;
      mstate->dtms_scratch_ptr += strsz;
      return (ret);
}

/*
 * Return a string from a memoy address which is known to have one or
 * more concatenated, individually zero terminated, sub-strings.
 * In the event that the user lacks the privilege to access
 * arbitrary kernel memory, we copy the string out to scratch memory so that we
 * don't fail access checking.
 *
 * dtrace_dif_variable() uses this routine as a helper for various
 * builtin values such as 'execargs'.
 */
static uintptr_t
dtrace_dif_varstrz(uintptr_t addr, size_t strsz, dtrace_state_t *state,
    dtrace_mstate_t *mstate)
{
      char *p;
      size_t i;
      uintptr_t ret;

      if (mstate->dtms_scratch_ptr + strsz >
          mstate->dtms_scratch_base + mstate->dtms_scratch_size) {
            DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
            return (0);
      }

      dtrace_bcopy((const void *)addr, (void *)mstate->dtms_scratch_ptr,
          strsz);

      /* Replace sub-string termination characters with a space. */
      for (p = (char *) mstate->dtms_scratch_ptr, i = 0; i < strsz - 1;
          p++, i++)
            if (*p == '\0')
                  *p = ' ';

      ret = mstate->dtms_scratch_ptr;
      mstate->dtms_scratch_ptr += strsz;
      return (ret);
}

/*
 * This function implements the DIF emulator's variable lookups.  The emulator
 * passes a reserved variable identifier and optional built-in array index.
 */
static uint64_t
dtrace_dif_variable(dtrace_mstate_t *mstate, dtrace_state_t *state, uint64_t v,
    uint64_t ndx)
{
      /*
       * If we're accessing one of the uncached arguments, we'll turn this
       * into a reference in the args array.
       */
      if (v >= DIF_VAR_ARG0 && v <= DIF_VAR_ARG9) {
            ndx = v - DIF_VAR_ARG0;
            v = DIF_VAR_ARGS;
      }

      switch (v) {
      case DIF_VAR_ARGS:
            ASSERT(mstate->dtms_present & DTRACE_MSTATE_ARGS);
            if (ndx >= sizeof (mstate->dtms_arg) /
                sizeof (mstate->dtms_arg[0])) {
                  int aframes = mstate->dtms_probe->dtpr_aframes + 2;
                  dtrace_provider_t *pv;
                  uint64_t val;

                  pv = mstate->dtms_probe->dtpr_provider;
                  if (pv->dtpv_pops.dtps_getargval != NULL)
                        val = pv->dtpv_pops.dtps_getargval(pv->dtpv_arg,
                            mstate->dtms_probe->dtpr_id,
                            mstate->dtms_probe->dtpr_arg, ndx, aframes);
                  else
                        val = dtrace_getarg(ndx, aframes);

                  /*
                   * This is regrettably required to keep the compiler
                   * from tail-optimizing the call to dtrace_getarg().
                   * The condition always evaluates to true, but the
                   * compiler has no way of figuring that out a priori.
                   * (None of this would be necessary if the compiler
                   * could be relied upon to _always_ tail-optimize
                   * the call to dtrace_getarg() -- but it can't.)
                   */
                  if (mstate->dtms_probe != NULL)
                        return (val);

                  ASSERT(0);
            }

            return (mstate->dtms_arg[ndx]);

#if defined(sun)
      case DIF_VAR_UREGS: {
            klwp_t *lwp;

            if (!dtrace_priv_proc(state))
                  return (0);

            if ((lwp = curthread->t_lwp) == NULL) {
                  DTRACE_CPUFLAG_SET(CPU_DTRACE_BADADDR);
                  cpu_core[curcpu].cpuc_dtrace_illval = NULL;
                  return (0);
            }

            return (dtrace_getreg(lwp->lwp_regs, ndx));
            return (0);
      }
#endif

      case DIF_VAR_CURTHREAD:
            if (!dtrace_priv_kernel(state))
                  return (0);
            return ((uint64_t)(uintptr_t)curthread);

      case DIF_VAR_TIMESTAMP:
            if (!(mstate->dtms_present & DTRACE_MSTATE_TIMESTAMP)) {
                  mstate->dtms_timestamp = dtrace_gethrtime();
                  mstate->dtms_present |= DTRACE_MSTATE_TIMESTAMP;
            }
            return (mstate->dtms_timestamp);

      case DIF_VAR_VTIMESTAMP:
            ASSERT(dtrace_vtime_references != 0);
            return (curthread->t_dtrace_vtime);

      case DIF_VAR_WALLTIMESTAMP:
            if (!(mstate->dtms_present & DTRACE_MSTATE_WALLTIMESTAMP)) {
                  mstate->dtms_walltimestamp = dtrace_gethrestime();
                  mstate->dtms_present |= DTRACE_MSTATE_WALLTIMESTAMP;
            }
            return (mstate->dtms_walltimestamp);

#if defined(sun)
      case DIF_VAR_IPL:
            if (!dtrace_priv_kernel(state))
                  return (0);
            if (!(mstate->dtms_present & DTRACE_MSTATE_IPL)) {
                  mstate->dtms_ipl = dtrace_getipl();
                  mstate->dtms_present |= DTRACE_MSTATE_IPL;
            }
            return (mstate->dtms_ipl);
#endif

      case DIF_VAR_EPID:
            ASSERT(mstate->dtms_present & DTRACE_MSTATE_EPID);
            return (mstate->dtms_epid);

      case DIF_VAR_ID:
            ASSERT(mstate->dtms_present & DTRACE_MSTATE_PROBE);
            return (mstate->dtms_probe->dtpr_id);

      case DIF_VAR_STACKDEPTH:
            if (!dtrace_priv_kernel(state))
                  return (0);
            if (!(mstate->dtms_present & DTRACE_MSTATE_STACKDEPTH)) {
                  int aframes = mstate->dtms_probe->dtpr_aframes + 2;

                  mstate->dtms_stackdepth = dtrace_getstackdepth(aframes);
                  mstate->dtms_present |= DTRACE_MSTATE_STACKDEPTH;
            }
            return (mstate->dtms_stackdepth);

#if defined(sun)
      case DIF_VAR_USTACKDEPTH:
            if (!dtrace_priv_proc(state))
                  return (0);
            if (!(mstate->dtms_present & DTRACE_MSTATE_USTACKDEPTH)) {
                  /*
                   * See comment in DIF_VAR_PID.
                   */
                  if (DTRACE_ANCHORED(mstate->dtms_probe) &&
                      CPU_ON_INTR(CPU)) {
                        mstate->dtms_ustackdepth = 0;
                  } else {
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
                        mstate->dtms_ustackdepth =
                            dtrace_getustackdepth();
                        DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT);
                  }
                  mstate->dtms_present |= DTRACE_MSTATE_USTACKDEPTH;
            }
            return (mstate->dtms_ustackdepth);
#endif

      case DIF_VAR_CALLER:
            if (!dtrace_priv_kernel(state))
                  return (0);
            if (!(mstate->dtms_present & DTRACE_MSTATE_CALLER)) {
                  int aframes = mstate->dtms_probe->dtpr_aframes + 2;

                  if (!DTRACE_ANCHORED(mstate->dtms_probe)) {
                        /*
                         * If this is an unanchored probe, we are
                         * required to go through the slow path:
                         * dtrace_caller() only guarantees correct
                         * results for anchored probes.
                         */
                        pc_t caller[2] = {0, 0};

                        dtrace_getpcstack(caller, 2, aframes,
                            (uint32_t *)(uintptr_t)mstate->dtms_arg[0]);
                        mstate->dtms_caller = caller[1];
                  } else if ((mstate->dtms_caller =
                      dtrace_caller(aframes)) == -1) {
                        /*
                         * We have failed to do this the quick way;
                         * we must resort to the slower approach of
                         * calling dtrace_getpcstack().
                         */
                        pc_t caller = 0;

                        dtrace_getpcstack(&caller, 1, aframes, NULL);
                        mstate->dtms_caller = caller;
                  }

                  mstate->dtms_present |= DTRACE_MSTATE_CALLER;
            }
            return (mstate->dtms_caller);

#if defined(sun)
      case DIF_VAR_UCALLER:
            if (!dtrace_priv_proc(state))
                  return (0);

            if (!(mstate->dtms_present & DTRACE_MSTATE_UCALLER)) {
                  uint64_t ustack[3];

                  /*
                   * dtrace_getupcstack() fills in the first uint64_t
                   * with the current PID.  The second uint64_t will
                   * be the program counter at user-level.  The third
                   * uint64_t will contain the caller, which is what
                   * we're after.
                   */
                  ustack[2] = 0;
                  DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
                  dtrace_getupcstack(ustack, 3);
                  DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT);
                  mstate->dtms_ucaller = ustack[2];
                  mstate->dtms_present |= DTRACE_MSTATE_UCALLER;
            }

            return (mstate->dtms_ucaller);
#endif

      case DIF_VAR_PROBEPROV:
            ASSERT(mstate->dtms_present & DTRACE_MSTATE_PROBE);
            return (dtrace_dif_varstr(
                (uintptr_t)mstate->dtms_probe->dtpr_provider->dtpv_name,
                state, mstate));

      case DIF_VAR_PROBEMOD:
            ASSERT(mstate->dtms_present & DTRACE_MSTATE_PROBE);
            return (dtrace_dif_varstr(
                (uintptr_t)mstate->dtms_probe->dtpr_mod,
                state, mstate));

      case DIF_VAR_PROBEFUNC:
            ASSERT(mstate->dtms_present & DTRACE_MSTATE_PROBE);
            return (dtrace_dif_varstr(
                (uintptr_t)mstate->dtms_probe->dtpr_func,
                state, mstate));

      case DIF_VAR_PROBENAME:
            ASSERT(mstate->dtms_present & DTRACE_MSTATE_PROBE);
            return (dtrace_dif_varstr(
                (uintptr_t)mstate->dtms_probe->dtpr_name,
                state, mstate));

      case DIF_VAR_PID:
            if (!dtrace_priv_proc(state))
                  return (0);

#if defined(sun)
            /*
             * Note that we are assuming that an unanchored probe is
             * always due to a high-level interrupt.  (And we're assuming
             * that there is only a single high level interrupt.)
             */
            if (DTRACE_ANCHORED(mstate->dtms_probe) && CPU_ON_INTR(CPU))
                  return (pid0.pid_id);

            /*
             * It is always safe to dereference one's own t_procp pointer:
             * it always points to a valid, allocated proc structure.
             * Further, it is always safe to dereference the p_pidp member
             * of one's own proc structure.  (These are truisms becuase
             * threads and processes don't clean up their own state --
             * they leave that task to whomever reaps them.)
             */
            return ((uint64_t)curthread->t_procp->p_pidp->pid_id);
#else
            return ((uint64_t)curproc->p_pid);
#endif

      case DIF_VAR_PPID:
            if (!dtrace_priv_proc(state))
                  return (0);

#if defined(sun)
            /*
             * See comment in DIF_VAR_PID.
             */
            if (DTRACE_ANCHORED(mstate->dtms_probe) && CPU_ON_INTR(CPU))
                  return (pid0.pid_id);

            /*
             * It is always safe to dereference one's own t_procp pointer:
             * it always points to a valid, allocated proc structure.
             * (This is true because threads don't clean up their own
             * state -- they leave that task to whomever reaps them.)
             */
            return ((uint64_t)curthread->t_procp->p_ppid);
#else
            return ((uint64_t)curproc->p_pptr->p_pid);
#endif

      case DIF_VAR_TID:
#if defined(sun)
            /*
             * See comment in DIF_VAR_PID.
             */
            if (DTRACE_ANCHORED(mstate->dtms_probe) && CPU_ON_INTR(CPU))
                  return (0);
#endif

            return ((uint64_t)curthread->t_tid);

      case DIF_VAR_EXECARGS: {
            struct pargs *p_args = curthread->td_proc->p_args;

            if (p_args == NULL)
                  return(0);

            return (dtrace_dif_varstrz(
                (uintptr_t) p_args->ar_args, p_args->ar_length, state, mstate));
      }

      case DIF_VAR_EXECNAME:
#if defined(sun)
            if (!dtrace_priv_proc(state))
                  return (0);

            /*
             * See comment in DIF_VAR_PID.
             */
            if (DTRACE_ANCHORED(mstate->dtms_probe) && CPU_ON_INTR(CPU))
                  return ((uint64_t)(uintptr_t)p0.p_user.u_comm);

            /*
             * It is always safe to dereference one's own t_procp pointer:
             * it always points to a valid, allocated proc structure.
             * (This is true because threads don't clean up their own
             * state -- they leave that task to whomever reaps them.)
             */
            return (dtrace_dif_varstr(
                (uintptr_t)curthread->t_procp->p_user.u_comm,
                state, mstate));
#else
            return (dtrace_dif_varstr(
                (uintptr_t) curthread->td_proc->p_comm, state, mstate));
#endif

      case DIF_VAR_ZONENAME:
#if defined(sun)
            if (!dtrace_priv_proc(state))
                  return (0);

            /*
             * See comment in DIF_VAR_PID.
             */
            if (DTRACE_ANCHORED(mstate->dtms_probe) && CPU_ON_INTR(CPU))
                  return ((uint64_t)(uintptr_t)p0.p_zone->zone_name);

            /*
             * It is always safe to dereference one's own t_procp pointer:
             * it always points to a valid, allocated proc structure.
             * (This is true because threads don't clean up their own
             * state -- they leave that task to whomever reaps them.)
             */
            return (dtrace_dif_varstr(
                (uintptr_t)curthread->t_procp->p_zone->zone_name,
                state, mstate));
#else
            return (0);
#endif

      case DIF_VAR_UID:
            if (!dtrace_priv_proc(state))
                  return (0);

#if defined(sun)
            /*
             * See comment in DIF_VAR_PID.
             */
            if (DTRACE_ANCHORED(mstate->dtms_probe) && CPU_ON_INTR(CPU))
                  return ((uint64_t)p0.p_cred->cr_uid);
#endif

            /*
             * It is always safe to dereference one's own t_procp pointer:
             * it always points to a valid, allocated proc structure.
             * (This is true because threads don't clean up their own
             * state -- they leave that task to whomever reaps them.)
             *
             * Additionally, it is safe to dereference one's own process
             * credential, since this is never NULL after process birth.
             */
            return ((uint64_t)curthread->t_procp->p_cred->cr_uid);

      case DIF_VAR_GID:
            if (!dtrace_priv_proc(state))
                  return (0);

#if defined(sun)
            /*
             * See comment in DIF_VAR_PID.
             */
            if (DTRACE_ANCHORED(mstate->dtms_probe) && CPU_ON_INTR(CPU))
                  return ((uint64_t)p0.p_cred->cr_gid);
#endif

            /*
             * It is always safe to dereference one's own t_procp pointer:
             * it always points to a valid, allocated proc structure.
             * (This is true because threads don't clean up their own
             * state -- they leave that task to whomever reaps them.)
             *
             * Additionally, it is safe to dereference one's own process
             * credential, since this is never NULL after process birth.
             */
            return ((uint64_t)curthread->t_procp->p_cred->cr_gid);

      case DIF_VAR_ERRNO: {
#if defined(sun)
            klwp_t *lwp;
            if (!dtrace_priv_proc(state))
                  return (0);

            /*
             * See comment in DIF_VAR_PID.
             */
            if (DTRACE_ANCHORED(mstate->dtms_probe) && CPU_ON_INTR(CPU))
                  return (0);

            /*
             * It is always safe to dereference one's own t_lwp pointer in
             * the event that this pointer is non-NULL.  (This is true
             * because threads and lwps don't clean up their own state --
             * they leave that task to whomever reaps them.)
             */
            if ((lwp = curthread->t_lwp) == NULL)
                  return (0);

            return ((uint64_t)lwp->lwp_errno);
#else
            return (curthread->td_errno);
#endif
      }
      default:
            DTRACE_CPUFLAG_SET(CPU_DTRACE_ILLOP);
            return (0);
      }
}

/*
 * Emulate the execution of DTrace ID subroutines invoked by the call opcode.
 * Notice that we don't bother validating the proper number of arguments or
 * their types in the tuple stack.  This isn't needed because all argument
 * interpretation is safe because of our load safety -- the worst that can
 * happen is that a bogus program can obtain bogus results.
 */
static void
dtrace_dif_subr(uint_t subr, uint_t rd, uint64_t *regs,
    dtrace_key_t *tupregs, int nargs,
    dtrace_mstate_t *mstate, dtrace_state_t *state)
{
      volatile uint16_t *flags = &cpu_core[curcpu].cpuc_dtrace_flags;
      volatile uintptr_t *illval = &cpu_core[curcpu].cpuc_dtrace_illval;
      dtrace_vstate_t *vstate = &state->dts_vstate;

#if defined(sun)
      union {
            mutex_impl_t mi;
            uint64_t mx;
      } m;

      union {
            krwlock_t ri;
            uintptr_t rw;
      } r;
#else
      struct thread *lowner;
      union {
            struct lock_object *li;
            uintptr_t lx;
      } l;
#endif

      switch (subr) {
      case DIF_SUBR_RAND:
            regs[rd] = (dtrace_gethrtime() * 2416 + 374441) % 1771875;
            break;

#if defined(sun)
      case DIF_SUBR_MUTEX_OWNED:
            if (!dtrace_canload(tupregs[0].dttk_value, sizeof (kmutex_t),
                mstate, vstate)) {
                  regs[rd] = 0;
                  break;
            }

            m.mx = dtrace_load64(tupregs[0].dttk_value);
            if (MUTEX_TYPE_ADAPTIVE(&m.mi))
                  regs[rd] = MUTEX_OWNER(&m.mi) != MUTEX_NO_OWNER;
            else
                  regs[rd] = LOCK_HELD(&m.mi.m_spin.m_spinlock);
            break;

      case DIF_SUBR_MUTEX_OWNER:
            if (!dtrace_canload(tupregs[0].dttk_value, sizeof (kmutex_t),
                mstate, vstate)) {
                  regs[rd] = 0;
                  break;
            }

            m.mx = dtrace_load64(tupregs[0].dttk_value);
            if (MUTEX_TYPE_ADAPTIVE(&m.mi) &&
                MUTEX_OWNER(&m.mi) != MUTEX_NO_OWNER)
                  regs[rd] = (uintptr_t)MUTEX_OWNER(&m.mi);
            else
                  regs[rd] = 0;
            break;

      case DIF_SUBR_MUTEX_TYPE_ADAPTIVE:
            if (!dtrace_canload(tupregs[0].dttk_value, sizeof (kmutex_t),
                mstate, vstate)) {
                  regs[rd] = 0;
                  break;
            }

            m.mx = dtrace_load64(tupregs[0].dttk_value);
            regs[rd] = MUTEX_TYPE_ADAPTIVE(&m.mi);
            break;

      case DIF_SUBR_MUTEX_TYPE_SPIN:
            if (!dtrace_canload(tupregs[0].dttk_value, sizeof (kmutex_t),
                mstate, vstate)) {
                  regs[rd] = 0;
                  break;
            }

            m.mx = dtrace_load64(tupregs[0].dttk_value);
            regs[rd] = MUTEX_TYPE_SPIN(&m.mi);
            break;

      case DIF_SUBR_RW_READ_HELD: {
            uintptr_t tmp;

            if (!dtrace_canload(tupregs[0].dttk_value, sizeof (uintptr_t),
                mstate, vstate)) {
                  regs[rd] = 0;
                  break;
            }

            r.rw = dtrace_loadptr(tupregs[0].dttk_value);
            regs[rd] = _RW_READ_HELD(&r.ri, tmp);
            break;
      }

      case DIF_SUBR_RW_WRITE_HELD:
            if (!dtrace_canload(tupregs[0].dttk_value, sizeof (krwlock_t),
                mstate, vstate)) {
                  regs[rd] = 0;
                  break;
            }

            r.rw = dtrace_loadptr(tupregs[0].dttk_value);
            regs[rd] = _RW_WRITE_HELD(&r.ri);
            break;

      case DIF_SUBR_RW_ISWRITER:
            if (!dtrace_canload(tupregs[0].dttk_value, sizeof (krwlock_t),
                mstate, vstate)) {
                  regs[rd] = 0;
                  break;
            }

            r.rw = dtrace_loadptr(tupregs[0].dttk_value);
            regs[rd] = _RW_ISWRITER(&r.ri);
            break;

#else
      case DIF_SUBR_MUTEX_OWNED:
            if (!dtrace_canload(tupregs[0].dttk_value,
                  sizeof (struct lock_object), mstate, vstate)) {
                  regs[rd] = 0;
                  break;
            }
            l.lx = dtrace_loadptr((uintptr_t)&tupregs[0].dttk_value);
            regs[rd] = LOCK_CLASS(l.li)->lc_owner(l.li, &lowner);
            break;

      case DIF_SUBR_MUTEX_OWNER:
            if (!dtrace_canload(tupregs[0].dttk_value,
                  sizeof (struct lock_object), mstate, vstate)) {
                  regs[rd] = 0;
                  break;
            }
            l.lx = dtrace_loadptr((uintptr_t)&tupregs[0].dttk_value);
            LOCK_CLASS(l.li)->lc_owner(l.li, &lowner);
            regs[rd] = (uintptr_t)lowner;
            break;

      case DIF_SUBR_MUTEX_TYPE_ADAPTIVE:
            if (!dtrace_canload(tupregs[0].dttk_value, sizeof (struct mtx),
                mstate, vstate)) {
                  regs[rd] = 0;
                  break;
            }
            l.lx = dtrace_loadptr((uintptr_t)&tupregs[0].dttk_value);
            /* XXX - should be only LC_SLEEPABLE? */
            regs[rd] = (LOCK_CLASS(l.li)->lc_flags &
                (LC_SLEEPLOCK | LC_SLEEPABLE)) != 0;
            break;

      case DIF_SUBR_MUTEX_TYPE_SPIN:
            if (!dtrace_canload(tupregs[0].dttk_value, sizeof (struct mtx),
                mstate, vstate)) {
                  regs[rd] = 0;
                  break;
            }
            l.lx = dtrace_loadptr((uintptr_t)&tupregs[0].dttk_value);
            regs[rd] = (LOCK_CLASS(l.li)->lc_flags & LC_SPINLOCK) != 0;
            break;

      case DIF_SUBR_RW_READ_HELD: 
      case DIF_SUBR_SX_SHARED_HELD: 
            if (!dtrace_canload(tupregs[0].dttk_value, sizeof (uintptr_t),
                mstate, vstate)) {
                  regs[rd] = 0;
                  break;
            }
            l.lx = dtrace_loadptr((uintptr_t)&tupregs[0].dttk_value);
            regs[rd] = LOCK_CLASS(l.li)->lc_owner(l.li, &lowner) &&
                lowner == NULL;
            break;

      case DIF_SUBR_RW_WRITE_HELD:
      case DIF_SUBR_SX_EXCLUSIVE_HELD:
            if (!dtrace_canload(tupregs[0].dttk_value, sizeof (uintptr_t),
                mstate, vstate)) {
                  regs[rd] = 0;
                  break;
            }
            l.lx = dtrace_loadptr(tupregs[0].dttk_value);
            LOCK_CLASS(l.li)->lc_owner(l.li, &lowner);
            regs[rd] = (lowner == curthread);
            break;

      case DIF_SUBR_RW_ISWRITER:
      case DIF_SUBR_SX_ISEXCLUSIVE:
            if (!dtrace_canload(tupregs[0].dttk_value, sizeof (uintptr_t),
                mstate, vstate)) {
                  regs[rd] = 0;
                  break;
            }
            l.lx = dtrace_loadptr(tupregs[0].dttk_value);
            regs[rd] = LOCK_CLASS(l.li)->lc_owner(l.li, &lowner) &&
                lowner != NULL;
            break;
#endif /* ! defined(sun) */

      case DIF_SUBR_BCOPY: {
            /*
             * We need to be sure that the destination is in the scratch
             * region -- no other region is allowed.
             */
            uintptr_t src = tupregs[0].dttk_value;
            uintptr_t dest = tupregs[1].dttk_value;
            size_t size = tupregs[2].dttk_value;

            if (!dtrace_inscratch(dest, size, mstate)) {
                  *flags |= CPU_DTRACE_BADADDR;
                  *illval = regs[rd];
                  break;
            }

            if (!dtrace_canload(src, size, mstate, vstate)) {
                  regs[rd] = 0;
                  break;
            }

            dtrace_bcopy((void *)src, (void *)dest, size);
            break;
      }

      case DIF_SUBR_ALLOCA:
      case DIF_SUBR_COPYIN: {
            uintptr_t dest = P2ROUNDUP(mstate->dtms_scratch_ptr, 8);
            uint64_t size =
                tupregs[subr == DIF_SUBR_ALLOCA ? 0 : 1].dttk_value;
            size_t scratch_size = (dest - mstate->dtms_scratch_ptr) + size;

            /*
             * This action doesn't require any credential checks since
             * probes will not activate in user contexts to which the
             * enabling user does not have permissions.
             */

            /*
             * Rounding up the user allocation size could have overflowed
             * a large, bogus allocation (like -1ULL) to 0.
             */
            if (scratch_size < size ||
                !DTRACE_INSCRATCH(mstate, scratch_size)) {
                  DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
                  regs[rd] = 0;
                  break;
            }

            if (subr == DIF_SUBR_COPYIN) {
                  DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
                  dtrace_copyin(tupregs[0].dttk_value, dest, size, flags);
                  DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT);
            }

            mstate->dtms_scratch_ptr += scratch_size;
            regs[rd] = dest;
            break;
      }

      case DIF_SUBR_COPYINTO: {
            uint64_t size = tupregs[1].dttk_value;
            uintptr_t dest = tupregs[2].dttk_value;

            /*
             * This action doesn't require any credential checks since
             * probes will not activate in user contexts to which the
             * enabling user does not have permissions.
             */
            if (!dtrace_inscratch(dest, size, mstate)) {
                  *flags |= CPU_DTRACE_BADADDR;
                  *illval = regs[rd];
                  break;
            }

            DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
            dtrace_copyin(tupregs[0].dttk_value, dest, size, flags);
            DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT);
            break;
      }

      case DIF_SUBR_COPYINSTR: {
            uintptr_t dest = mstate->dtms_scratch_ptr;
            uint64_t size = state->dts_options[DTRACEOPT_STRSIZE];

            if (nargs > 1 && tupregs[1].dttk_value < size)
                  size = tupregs[1].dttk_value + 1;

            /*
             * This action doesn't require any credential checks since
             * probes will not activate in user contexts to which the
             * enabling user does not have permissions.
             */
            if (!DTRACE_INSCRATCH(mstate, size)) {
                  DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
                  regs[rd] = 0;
                  break;
            }

            DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
            dtrace_copyinstr(tupregs[0].dttk_value, dest, size, flags);
            DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT);

            ((char *)dest)[size - 1] = '\0';
            mstate->dtms_scratch_ptr += size;
            regs[rd] = dest;
            break;
      }

#if defined(sun)
      case DIF_SUBR_MSGSIZE:
      case DIF_SUBR_MSGDSIZE: {
            uintptr_t baddr = tupregs[0].dttk_value, daddr;
            uintptr_t wptr, rptr;
            size_t count = 0;
            int cont = 0;

            while (baddr != 0 && !(*flags & CPU_DTRACE_FAULT)) {

                  if (!dtrace_canload(baddr, sizeof (mblk_t), mstate,
                      vstate)) {
                        regs[rd] = 0;
                        break;
                  }

                  wptr = dtrace_loadptr(baddr +
                      offsetof(mblk_t, b_wptr));

                  rptr = dtrace_loadptr(baddr +
                      offsetof(mblk_t, b_rptr));

                  if (wptr < rptr) {
                        *flags |= CPU_DTRACE_BADADDR;
                        *illval = tupregs[0].dttk_value;
                        break;
                  }

                  daddr = dtrace_loadptr(baddr +
                      offsetof(mblk_t, b_datap));

                  baddr = dtrace_loadptr(baddr +
                      offsetof(mblk_t, b_cont));

                  /*
                   * We want to prevent against denial-of-service here,
                   * so we're only going to search the list for
                   * dtrace_msgdsize_max mblks.
                   */
                  if (cont++ > dtrace_msgdsize_max) {
                        *flags |= CPU_DTRACE_ILLOP;
                        break;
                  }

                  if (subr == DIF_SUBR_MSGDSIZE) {
                        if (dtrace_load8(daddr +
                            offsetof(dblk_t, db_type)) != M_DATA)
                              continue;
                  }

                  count += wptr - rptr;
            }

            if (!(*flags & CPU_DTRACE_FAULT))
                  regs[rd] = count;

            break;
      }
#endif

      case DIF_SUBR_PROGENYOF: {
            pid_t pid = tupregs[0].dttk_value;
            proc_t *p;
            int rval = 0;

            DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);

            for (p = curthread->t_procp; p != NULL; p = p->p_parent) {
#if defined(sun)
                  if (p->p_pidp->pid_id == pid) {
#else
                  if (p->p_pid == pid) {
#endif
                        rval = 1;
                        break;
                  }
            }

            DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT);

            regs[rd] = rval;
            break;
      }

      case DIF_SUBR_SPECULATION:
            regs[rd] = dtrace_speculation(state);
            break;

      case DIF_SUBR_COPYOUT: {
            uintptr_t kaddr = tupregs[0].dttk_value;
            uintptr_t uaddr = tupregs[1].dttk_value;
            uint64_t size = tupregs[2].dttk_value;

            if (!dtrace_destructive_disallow &&
                dtrace_priv_proc_control(state) &&
                !dtrace_istoxic(kaddr, size)) {
                  DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
                  dtrace_copyout(kaddr, uaddr, size, flags);
                  DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT);
            }
            break;
      }

      case DIF_SUBR_COPYOUTSTR: {
            uintptr_t kaddr = tupregs[0].dttk_value;
            uintptr_t uaddr = tupregs[1].dttk_value;
            uint64_t size = tupregs[2].dttk_value;

            if (!dtrace_destructive_disallow &&
                dtrace_priv_proc_control(state) &&
                !dtrace_istoxic(kaddr, size)) {
                  DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
                  dtrace_copyoutstr(kaddr, uaddr, size, flags);
                  DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT);
            }
            break;
      }

      case DIF_SUBR_STRLEN: {
            size_t sz;
            uintptr_t addr = (uintptr_t)tupregs[0].dttk_value;
            sz = dtrace_strlen((char *)addr,
                state->dts_options[DTRACEOPT_STRSIZE]);

            if (!dtrace_canload(addr, sz + 1, mstate, vstate)) {
                  regs[rd] = 0;
                  break;
            }

            regs[rd] = sz;

            break;
      }

      case DIF_SUBR_STRCHR:
      case DIF_SUBR_STRRCHR: {
            /*
             * We're going to iterate over the string looking for the
             * specified character.  We will iterate until we have reached
             * the string length or we have found the character.  If this
             * is DIF_SUBR_STRRCHR, we will look for the last occurrence
             * of the specified character instead of the first.
             */
            uintptr_t saddr = tupregs[0].dttk_value;
            uintptr_t addr = tupregs[0].dttk_value;
            uintptr_t limit = addr + state->dts_options[DTRACEOPT_STRSIZE];
            char c, target = (char)tupregs[1].dttk_value;

            for (regs[rd] = 0; addr < limit; addr++) {
                  if ((c = dtrace_load8(addr)) == target) {
                        regs[rd] = addr;

                        if (subr == DIF_SUBR_STRCHR)
                              break;
                  }

                  if (c == '\0')
                        break;
            }

            if (!dtrace_canload(saddr, addr - saddr, mstate, vstate)) {
                  regs[rd] = 0;
                  break;
            }

            break;
      }

      case DIF_SUBR_STRSTR:
      case DIF_SUBR_INDEX:
      case DIF_SUBR_RINDEX: {
            /*
             * We're going to iterate over the string looking for the
             * specified string.  We will iterate until we have reached
             * the string length or we have found the string.  (Yes, this
             * is done in the most naive way possible -- but considering
             * that the string we're searching for is likely to be
             * relatively short, the complexity of Rabin-Karp or similar
             * hardly seems merited.)
             */
            char *addr = (char *)(uintptr_t)tupregs[0].dttk_value;
            char *substr = (char *)(uintptr_t)tupregs[1].dttk_value;
            uint64_t size = state->dts_options[DTRACEOPT_STRSIZE];
            size_t len = dtrace_strlen(addr, size);
            size_t sublen = dtrace_strlen(substr, size);
            char *limit = addr + len, *orig = addr;
            int notfound = subr == DIF_SUBR_STRSTR ? 0 : -1;
            int inc = 1;

            regs[rd] = notfound;

            if (!dtrace_canload((uintptr_t)addr, len + 1, mstate, vstate)) {
                  regs[rd] = 0;
                  break;
            }

            if (!dtrace_canload((uintptr_t)substr, sublen + 1, mstate,
                vstate)) {
                  regs[rd] = 0;
                  break;
            }

            /*
             * strstr() and index()/rindex() have similar semantics if
             * both strings are the empty string: strstr() returns a
             * pointer to the (empty) string, and index() and rindex()
             * both return index 0 (regardless of any position argument).
             */
            if (sublen == 0 && len == 0) {
                  if (subr == DIF_SUBR_STRSTR)
                        regs[rd] = (uintptr_t)addr;
                  else
                        regs[rd] = 0;
                  break;
            }

            if (subr != DIF_SUBR_STRSTR) {
                  if (subr == DIF_SUBR_RINDEX) {
                        limit = orig - 1;
                        addr += len;
                        inc = -1;
                  }

                  /*
                   * Both index() and rindex() take an optional position
                   * argument that denotes the starting position.
                   */
                  if (nargs == 3) {
                        int64_t pos = (int64_t)tupregs[2].dttk_value;

                        /*
                         * If the position argument to index() is
                         * negative, Perl implicitly clamps it at
                         * zero.  This semantic is a little surprising
                         * given the special meaning of negative
                         * positions to similar Perl functions like
                         * substr(), but it appears to reflect a
                         * notion that index() can start from a
                         * negative index and increment its way up to
                         * the string.  Given this notion, Perl's
                         * rindex() is at least self-consistent in
                         * that it implicitly clamps positions greater
                         * than the string length to be the string
                         * length.  Where Perl completely loses
                         * coherence, however, is when the specified
                         * substring is the empty string ("").  In
                         * this case, even if the position is
                         * negative, rindex() returns 0 -- and even if
                         * the position is greater than the length,
                         * index() returns the string length.  These
                         * semantics violate the notion that index()
                         * should never return a value less than the
                         * specified position and that rindex() should
                         * never return a value greater than the
                         * specified position.  (One assumes that
                         * these semantics are artifacts of Perl's
                         * implementation and not the results of
                         * deliberate design -- it beggars belief that
                         * even Larry Wall could desire such oddness.)
                         * While in the abstract one would wish for
                         * consistent position semantics across
                         * substr(), index() and rindex() -- or at the
                         * very least self-consistent position
                         * semantics for index() and rindex() -- we
                         * instead opt to keep with the extant Perl
                         * semantics, in all their broken glory.  (Do
                         * we have more desire to maintain Perl's
                         * semantics than Perl does?  Probably.)
                         */
                        if (subr == DIF_SUBR_RINDEX) {
                              if (pos < 0) {
                                    if (sublen == 0)
                                          regs[rd] = 0;
                                    break;
                              }

                              if (pos > len)
                                    pos = len;
                        } else {
                              if (pos < 0)
                                    pos = 0;

                              if (pos >= len) {
                                    if (sublen == 0)
                                          regs[rd] = len;
                                    break;
                              }
                        }

                        addr = orig + pos;
                  }
            }

            for (regs[rd] = notfound; addr != limit; addr += inc) {
                  if (dtrace_strncmp(addr, substr, sublen) == 0) {
                        if (subr != DIF_SUBR_STRSTR) {
                              /*
                               * As D index() and rindex() are
                               * modeled on Perl (and not on awk),
                               * we return a zero-based (and not a
                               * one-based) index.  (For you Perl
                               * weenies: no, we're not going to add
                               * $[ -- and shouldn't you be at a con
                               * or something?)
                               */
                              regs[rd] = (uintptr_t)(addr - orig);
                              break;
                        }

                        ASSERT(subr == DIF_SUBR_STRSTR);
                        regs[rd] = (uintptr_t)addr;
                        break;
                  }
            }

            break;
      }

      case DIF_SUBR_STRTOK: {
            uintptr_t addr = tupregs[0].dttk_value;
            uintptr_t tokaddr = tupregs[1].dttk_value;
            uint64_t size = state->dts_options[DTRACEOPT_STRSIZE];
            uintptr_t limit, toklimit = tokaddr + size;
            uint8_t c = 0, tokmap[32];     /* 256 / 8 */
            char *dest = (char *)mstate->dtms_scratch_ptr;
            int i;

            /*
             * Check both the token buffer and (later) the input buffer,
             * since both could be non-scratch addresses.
             */
            if (!dtrace_strcanload(tokaddr, size, mstate, vstate)) {
                  regs[rd] = 0;
                  break;
            }

            if (!DTRACE_INSCRATCH(mstate, size)) {
                  DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
                  regs[rd] = 0;
                  break;
            }

            if (addr == 0) {
                  /*
                   * If the address specified is NULL, we use our saved
                   * strtok pointer from the mstate.  Note that this
                   * means that the saved strtok pointer is _only_
                   * valid within multiple enablings of the same probe --
                   * it behaves like an implicit clause-local variable.
                   */
                  addr = mstate->dtms_strtok;
            } else {
                  /*
                   * If the user-specified address is non-NULL we must
                   * access check it.  This is the only time we have
                   * a chance to do so, since this address may reside
                   * in the string table of this clause-- future calls
                   * (when we fetch addr from mstate->dtms_strtok)
                   * would fail this access check.
                   */
                  if (!dtrace_strcanload(addr, size, mstate, vstate)) {
                        regs[rd] = 0;
                        break;
                  }
            }

            /*
             * First, zero the token map, and then process the token
             * string -- setting a bit in the map for every character
             * found in the token string.
             */
            for (i = 0; i < sizeof (tokmap); i++)
                  tokmap[i] = 0;

            for (; tokaddr < toklimit; tokaddr++) {
                  if ((c = dtrace_load8(tokaddr)) == '\0')
                        break;

                  ASSERT((c >> 3) < sizeof (tokmap));
                  tokmap[c >> 3] |= (1 << (c & 0x7));
            }

            for (limit = addr + size; addr < limit; addr++) {
                  /*
                   * We're looking for a character that is _not_ contained
                   * in the token string.
                   */
                  if ((c = dtrace_load8(addr)) == '\0')
                        break;

                  if (!(tokmap[c >> 3] & (1 << (c & 0x7))))
                        break;
            }

            if (c == '\0') {
                  /*
                   * We reached the end of the string without finding
                   * any character that was not in the token string.
                   * We return NULL in this case, and we set the saved
                   * address to NULL as well.
                   */
                  regs[rd] = 0;
                  mstate->dtms_strtok = 0;
                  break;
            }

            /*
             * From here on, we're copying into the destination string.
             */
            for (i = 0; addr < limit && i < size - 1; addr++) {
                  if ((c = dtrace_load8(addr)) == '\0')
                        break;

                  if (tokmap[c >> 3] & (1 << (c & 0x7)))
                        break;

                  ASSERT(i < size);
                  dest[i++] = c;
            }

            ASSERT(i < size);
            dest[i] = '\0';
            regs[rd] = (uintptr_t)dest;
            mstate->dtms_scratch_ptr += size;
            mstate->dtms_strtok = addr;
            break;
      }

      case DIF_SUBR_SUBSTR: {
            uintptr_t s = tupregs[0].dttk_value;
            uint64_t size = state->dts_options[DTRACEOPT_STRSIZE];
            char *d = (char *)mstate->dtms_scratch_ptr;
            int64_t index = (int64_t)tupregs[1].dttk_value;
            int64_t remaining = (int64_t)tupregs[2].dttk_value;
            size_t len = dtrace_strlen((char *)s, size);
            int64_t i = 0;

            if (!dtrace_canload(s, len + 1, mstate, vstate)) {
                  regs[rd] = 0;
                  break;
            }

            if (!DTRACE_INSCRATCH(mstate, size)) {
                  DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
                  regs[rd] = 0;
                  break;
            }

            if (nargs <= 2)
                  remaining = (int64_t)size;

            if (index < 0) {
                  index += len;

                  if (index < 0 && index + remaining > 0) {
                        remaining += index;
                        index = 0;
                  }
            }

            if (index >= len || index < 0) {
                  remaining = 0;
            } else if (remaining < 0) {
                  remaining += len - index;
            } else if (index + remaining > size) {
                  remaining = size - index;
            }

            for (i = 0; i < remaining; i++) {
                  if ((d[i] = dtrace_load8(s + index + i)) == '\0')
                        break;
            }

            d[i] = '\0';

            mstate->dtms_scratch_ptr += size;
            regs[rd] = (uintptr_t)d;
            break;
      }

#if defined(sun)
      case DIF_SUBR_GETMAJOR:
#ifdef _LP64
            regs[rd] = (tupregs[0].dttk_value >> NBITSMINOR64) & MAXMAJ64;
#else
            regs[rd] = (tupregs[0].dttk_value >> NBITSMINOR) & MAXMAJ;
#endif
            break;

      case DIF_SUBR_GETMINOR:
#ifdef _LP64
            regs[rd] = tupregs[0].dttk_value & MAXMIN64;
#else
            regs[rd] = tupregs[0].dttk_value & MAXMIN;
#endif
            break;

      case DIF_SUBR_DDI_PATHNAME: {
            /*
             * This one is a galactic mess.  We are going to roughly
             * emulate ddi_pathname(), but it's made more complicated
             * by the fact that we (a) want to include the minor name and
             * (b) must proceed iteratively instead of recursively.
             */
            uintptr_t dest = mstate->dtms_scratch_ptr;
            uint64_t size = state->dts_options[DTRACEOPT_STRSIZE];
            char *start = (char *)dest, *end = start + size - 1;
            uintptr_t daddr = tupregs[0].dttk_value;
            int64_t minor = (int64_t)tupregs[1].dttk_value;
            char *s;
            int i, len, depth = 0;

            /*
             * Due to all the pointer jumping we do and context we must
             * rely upon, we just mandate that the user must have kernel
             * read privileges to use this routine.
             */
            if ((mstate->dtms_access & DTRACE_ACCESS_KERNEL) == 0) {
                  *flags |= CPU_DTRACE_KPRIV;
                  *illval = daddr;
                  regs[rd] = 0;
            }

            if (!DTRACE_INSCRATCH(mstate, size)) {
                  DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
                  regs[rd] = 0;
                  break;
            }

            *end = '\0';

            /*
             * We want to have a name for the minor.  In order to do this,
             * we need to walk the minor list from the devinfo.  We want
             * to be sure that we don't infinitely walk a circular list,
             * so we check for circularity by sending a scout pointer
             * ahead two elements for every element that we iterate over;
             * if the list is circular, these will ultimately point to the
             * same element.  You may recognize this little trick as the
             * answer to a stupid interview question -- one that always
             * seems to be asked by those who had to have it laboriously
             * explained to them, and who can't even concisely describe
             * the conditions under which one would be forced to resort to
             * this technique.  Needless to say, those conditions are
             * found here -- and probably only here.  Is this the only use
             * of this infamous trick in shipping, production code?  If it
             * isn't, it probably should be...
             */
            if (minor != -1) {
                  uintptr_t maddr = dtrace_loadptr(daddr +
                      offsetof(struct dev_info, devi_minor));

                  uintptr_t next = offsetof(struct ddi_minor_data, next);
                  uintptr_t name = offsetof(struct ddi_minor_data,
                      d_minor) + offsetof(struct ddi_minor, name);
                  uintptr_t dev = offsetof(struct ddi_minor_data,
                      d_minor) + offsetof(struct ddi_minor, dev);
                  uintptr_t scout;

                  if (maddr != NULL)
                        scout = dtrace_loadptr(maddr + next);

                  while (maddr != NULL && !(*flags & CPU_DTRACE_FAULT)) {
                        uint64_t m;
#ifdef _LP64
                        m = dtrace_load64(maddr + dev) & MAXMIN64;
#else
                        m = dtrace_load32(maddr + dev) & MAXMIN;
#endif
                        if (m != minor) {
                              maddr = dtrace_loadptr(maddr + next);

                              if (scout == NULL)
                                    continue;

                              scout = dtrace_loadptr(scout + next);

                              if (scout == NULL)
                                    continue;

                              scout = dtrace_loadptr(scout + next);

                              if (scout == NULL)
                                    continue;

                              if (scout == maddr) {
                                    *flags |= CPU_DTRACE_ILLOP;
                                    break;
                              }

                              continue;
                        }

                        /*
                         * We have the minor data.  Now we need to
                         * copy the minor's name into the end of the
                         * pathname.
                         */
                        s = (char *)dtrace_loadptr(maddr + name);
                        len = dtrace_strlen(s, size);

                        if (*flags & CPU_DTRACE_FAULT)
                              break;

                        if (len != 0) {
                              if ((end -= (len + 1)) < start)
                                    break;

                              *end = ':';
                        }

                        for (i = 1; i <= len; i++)
                              end[i] = dtrace_load8((uintptr_t)s++);
                        break;
                  }
            }

            while (daddr != NULL && !(*flags & CPU_DTRACE_FAULT)) {
                  ddi_node_state_t devi_state;

                  devi_state = dtrace_load32(daddr +
                      offsetof(struct dev_info, devi_node_state));

                  if (*flags & CPU_DTRACE_FAULT)
                        break;

                  if (devi_state >= DS_INITIALIZED) {
                        s = (char *)dtrace_loadptr(daddr +
                            offsetof(struct dev_info, devi_addr));
                        len = dtrace_strlen(s, size);

                        if (*flags & CPU_DTRACE_FAULT)
                              break;

                        if (len != 0) {
                              if ((end -= (len + 1)) < start)
                                    break;

                              *end = '@';
                        }

                        for (i = 1; i <= len; i++)
                              end[i] = dtrace_load8((uintptr_t)s++);
                  }

                  /*
                   * Now for the node name...
                   */
                  s = (char *)dtrace_loadptr(daddr +
                      offsetof(struct dev_info, devi_node_name));

                  daddr = dtrace_loadptr(daddr +
                      offsetof(struct dev_info, devi_parent));

                  /*
                   * If our parent is NULL (that is, if we're the root
                   * node), we're going to use the special path
                   * "devices".
                   */
                  if (daddr == 0)
                        s = "devices";

                  len = dtrace_strlen(s, size);
                  if (*flags & CPU_DTRACE_FAULT)
                        break;

                  if ((end -= (len + 1)) < start)
                        break;

                  for (i = 1; i <= len; i++)
                        end[i] = dtrace_load8((uintptr_t)s++);
                  *end = '/';

                  if (depth++ > dtrace_devdepth_max) {
                        *flags |= CPU_DTRACE_ILLOP;
                        break;
                  }
            }

            if (end < start)
                  DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);

            if (daddr == 0) {
                  regs[rd] = (uintptr_t)end;
                  mstate->dtms_scratch_ptr += size;
            }

            break;
      }
#endif

      case DIF_SUBR_STRJOIN: {
            char *d = (char *)mstate->dtms_scratch_ptr;
            uint64_t size = state->dts_options[DTRACEOPT_STRSIZE];
            uintptr_t s1 = tupregs[0].dttk_value;
            uintptr_t s2 = tupregs[1].dttk_value;
            int i = 0;

            if (!dtrace_strcanload(s1, size, mstate, vstate) ||
                !dtrace_strcanload(s2, size, mstate, vstate)) {
                  regs[rd] = 0;
                  break;
            }

            if (!DTRACE_INSCRATCH(mstate, size)) {
                  DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
                  regs[rd] = 0;
                  break;
            }

            for (;;) {
                  if (i >= size) {
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
                        regs[rd] = 0;
                        break;
                  }

                  if ((d[i++] = dtrace_load8(s1++)) == '\0') {
                        i--;
                        break;
                  }
            }

            for (;;) {
                  if (i >= size) {
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
                        regs[rd] = 0;
                        break;
                  }

                  if ((d[i++] = dtrace_load8(s2++)) == '\0')
                        break;
            }

            if (i < size) {
                  mstate->dtms_scratch_ptr += i;
                  regs[rd] = (uintptr_t)d;
            }

            break;
      }

      case DIF_SUBR_LLTOSTR: {
            int64_t i = (int64_t)tupregs[0].dttk_value;
            int64_t val = i < 0 ? i * -1 : i;
            uint64_t size = 22;     /* enough room for 2^64 in decimal */
            char *end = (char *)mstate->dtms_scratch_ptr + size - 1;

            if (!DTRACE_INSCRATCH(mstate, size)) {
                  DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
                  regs[rd] = 0;
                  break;
            }

            for (*end-- = '\0'; val; val /= 10)
                  *end-- = '0' + (val % 10);

            if (i == 0)
                  *end-- = '0';

            if (i < 0)
                  *end-- = '-';

            regs[rd] = (uintptr_t)end + 1;
            mstate->dtms_scratch_ptr += size;
            break;
      }

      case DIF_SUBR_HTONS:
      case DIF_SUBR_NTOHS:
#if BYTE_ORDER == BIG_ENDIAN
            regs[rd] = (uint16_t)tupregs[0].dttk_value;
#else
            regs[rd] = DT_BSWAP_16((uint16_t)tupregs[0].dttk_value);
#endif
            break;


      case DIF_SUBR_HTONL:
      case DIF_SUBR_NTOHL:
#if BYTE_ORDER == BIG_ENDIAN
            regs[rd] = (uint32_t)tupregs[0].dttk_value;
#else
            regs[rd] = DT_BSWAP_32((uint32_t)tupregs[0].dttk_value);
#endif
            break;


      case DIF_SUBR_HTONLL:
      case DIF_SUBR_NTOHLL:
#if BYTE_ORDER == BIG_ENDIAN
            regs[rd] = (uint64_t)tupregs[0].dttk_value;
#else
            regs[rd] = DT_BSWAP_64((uint64_t)tupregs[0].dttk_value);
#endif
            break;


      case DIF_SUBR_DIRNAME:
      case DIF_SUBR_BASENAME: {
            char *dest = (char *)mstate->dtms_scratch_ptr;
            uint64_t size = state->dts_options[DTRACEOPT_STRSIZE];
            uintptr_t src = tupregs[0].dttk_value;
            int i, j, len = dtrace_strlen((char *)src, size);
            int lastbase = -1, firstbase = -1, lastdir = -1;
            int start, end;

            if (!dtrace_canload(src, len + 1, mstate, vstate)) {
                  regs[rd] = 0;
                  break;
            }

            if (!DTRACE_INSCRATCH(mstate, size)) {
                  DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
                  regs[rd] = 0;
                  break;
            }

            /*
             * The basename and dirname for a zero-length string is
             * defined to be "."
             */
            if (len == 0) {
                  len = 1;
                  src = (uintptr_t)".";
            }

            /*
             * Start from the back of the string, moving back toward the
             * front until we see a character that isn't a slash.  That
             * character is the last character in the basename.
             */
            for (i = len - 1; i >= 0; i--) {
                  if (dtrace_load8(src + i) != '/')
                        break;
            }

            if (i >= 0)
                  lastbase = i;

            /*
             * Starting from the last character in the basename, move
             * towards the front until we find a slash.  The character
             * that we processed immediately before that is the first
             * character in the basename.
             */
            for (; i >= 0; i--) {
                  if (dtrace_load8(src + i) == '/')
                        break;
            }

            if (i >= 0)
                  firstbase = i + 1;

            /*
             * Now keep going until we find a non-slash character.  That
             * character is the last character in the dirname.
             */
            for (; i >= 0; i--) {
                  if (dtrace_load8(src + i) != '/')
                        break;
            }

            if (i >= 0)
                  lastdir = i;

            ASSERT(!(lastbase == -1 && firstbase != -1));
            ASSERT(!(firstbase == -1 && lastdir != -1));

            if (lastbase == -1) {
                  /*
                   * We didn't find a non-slash character.  We know that
                   * the length is non-zero, so the whole string must be
                   * slashes.  In either the dirname or the basename
                   * case, we return '/'.
                   */
                  ASSERT(firstbase == -1);
                  firstbase = lastbase = lastdir = 0;
            }

            if (firstbase == -1) {
                  /*
                   * The entire string consists only of a basename
                   * component.  If we're looking for dirname, we need
                   * to change our string to be just "."; if we're
                   * looking for a basename, we'll just set the first
                   * character of the basename to be 0.
                   */
                  if (subr == DIF_SUBR_DIRNAME) {
                        ASSERT(lastdir == -1);
                        src = (uintptr_t)".";
                        lastdir = 0;
                  } else {
                        firstbase = 0;
                  }
            }

            if (subr == DIF_SUBR_DIRNAME) {
                  if (lastdir == -1) {
                        /*
                         * We know that we have a slash in the name --
                         * or lastdir would be set to 0, above.  And
                         * because lastdir is -1, we know that this
                         * slash must be the first character.  (That
                         * is, the full string must be of the form
                         * "/basename".)  In this case, the last
                         * character of the directory name is 0.
                         */
                        lastdir = 0;
                  }

                  start = 0;
                  end = lastdir;
            } else {
                  ASSERT(subr == DIF_SUBR_BASENAME);
                  ASSERT(firstbase != -1 && lastbase != -1);
                  start = firstbase;
                  end = lastbase;
            }

            for (i = start, j = 0; i <= end && j < size - 1; i++, j++)
                  dest[j] = dtrace_load8(src + i);

            dest[j] = '\0';
            regs[rd] = (uintptr_t)dest;
            mstate->dtms_scratch_ptr += size;
            break;
      }

      case DIF_SUBR_CLEANPATH: {
            char *dest = (char *)mstate->dtms_scratch_ptr, c;
            uint64_t size = state->dts_options[DTRACEOPT_STRSIZE];
            uintptr_t src = tupregs[0].dttk_value;
            int i = 0, j = 0;

            if (!dtrace_strcanload(src, size, mstate, vstate)) {
                  regs[rd] = 0;
                  break;
            }

            if (!DTRACE_INSCRATCH(mstate, size)) {
                  DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
                  regs[rd] = 0;
                  break;
            }

            /*
             * Move forward, loading each character.
             */
            do {
                  c = dtrace_load8(src + i++);
next:
                  if (j + 5 >= size)      /* 5 = strlen("/..c\0") */
                        break;

                  if (c != '/') {
                        dest[j++] = c;
                        continue;
                  }

                  c = dtrace_load8(src + i++);

                  if (c == '/') {
                        /*
                         * We have two slashes -- we can just advance
                         * to the next character.
                         */
                        goto next;
                  }

                  if (c != '.') {
                        /*
                         * This is not "." and it's not ".." -- we can
                         * just store the "/" and this character and
                         * drive on.
                         */
                        dest[j++] = '/';
                        dest[j++] = c;
                        continue;
                  }

                  c = dtrace_load8(src + i++);

                  if (c == '/') {
                        /*
                         * This is a "/./" component.  We're not going
                         * to store anything in the destination buffer;
                         * we're just going to go to the next component.
                         */
                        goto next;
                  }

                  if (c != '.') {
                        /*
                         * This is not ".." -- we can just store the
                         * "/." and this character and continue
                         * processing.
                         */
                        dest[j++] = '/';
                        dest[j++] = '.';
                        dest[j++] = c;
                        continue;
                  }

                  c = dtrace_load8(src + i++);

                  if (c != '/' && c != '\0') {
                        /*
                         * This is not ".." -- it's "..[mumble]".
                         * We'll store the "/.." and this character
                         * and continue processing.
                         */
                        dest[j++] = '/';
                        dest[j++] = '.';
                        dest[j++] = '.';
                        dest[j++] = c;
                        continue;
                  }

                  /*
                   * This is "/../" or "/..\0".  We need to back up
                   * our destination pointer until we find a "/".
                   */
                  i--;
                  while (j != 0 && dest[--j] != '/')
                        continue;

                  if (c == '\0')
                        dest[++j] = '/';
            } while (c != '\0');

            dest[j] = '\0';
            regs[rd] = (uintptr_t)dest;
            mstate->dtms_scratch_ptr += size;
            break;
      }

      case DIF_SUBR_INET_NTOA:
      case DIF_SUBR_INET_NTOA6:
      case DIF_SUBR_INET_NTOP: {
            size_t size;
            int af, argi, i;
            char *base, *end;

            if (subr == DIF_SUBR_INET_NTOP) {
                  af = (int)tupregs[0].dttk_value;
                  argi = 1;
            } else {
                  af = subr == DIF_SUBR_INET_NTOA ? AF_INET: AF_INET6;
                  argi = 0;
            }

            if (af == AF_INET) {
                  ipaddr_t ip4;
                  uint8_t *ptr8, val;

                  /*
                   * Safely load the IPv4 address.
                   */
                  ip4 = dtrace_load32(tupregs[argi].dttk_value);

                  /*
                   * Check an IPv4 string will fit in scratch.
                   */
                  size = INET_ADDRSTRLEN;
                  if (!DTRACE_INSCRATCH(mstate, size)) {
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
                        regs[rd] = 0;
                        break;
                  }
                  base = (char *)mstate->dtms_scratch_ptr;
                  end = (char *)mstate->dtms_scratch_ptr + size - 1;

                  /*
                   * Stringify as a dotted decimal quad.
                   */
                  *end-- = '\0';
                  ptr8 = (uint8_t *)&ip4;
                  for (i = 3; i >= 0; i--) {
                        val = ptr8[i];

                        if (val == 0) {
                              *end-- = '0';
                        } else {
                              for (; val; val /= 10) {
                                    *end-- = '0' + (val % 10);
                              }
                        }

                        if (i > 0)
                              *end-- = '.';
                  }
                  ASSERT(end + 1 >= base);

            } else if (af == AF_INET6) {
                  struct in6_addr ip6;
                  int firstzero, tryzero, numzero, v6end;
                  uint16_t val;
                  const char digits[] = "0123456789abcdef";

                  /*
                   * Stringify using RFC 1884 convention 2 - 16 bit
                   * hexadecimal values with a zero-run compression.
                   * Lower case hexadecimal digits are used.
                   *    eg, fe80::214:4fff:fe0b:76c8.
                   * The IPv4 embedded form is returned for inet_ntop,
                   * just the IPv4 string is returned for inet_ntoa6.
                   */

                  /*
                   * Safely load the IPv6 address.
                   */
                  dtrace_bcopy(
                      (void *)(uintptr_t)tupregs[argi].dttk_value,
                      (void *)(uintptr_t)&ip6, sizeof (struct in6_addr));

                  /*
                   * Check an IPv6 string will fit in scratch.
                   */
                  size = INET6_ADDRSTRLEN;
                  if (!DTRACE_INSCRATCH(mstate, size)) {
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
                        regs[rd] = 0;
                        break;
                  }
                  base = (char *)mstate->dtms_scratch_ptr;
                  end = (char *)mstate->dtms_scratch_ptr + size - 1;
                  *end-- = '\0';

                  /*
                   * Find the longest run of 16 bit zero values
                   * for the single allowed zero compression - "::".
                   */
                  firstzero = -1;
                  tryzero = -1;
                  numzero = 1;
                  for (i = 0; i < sizeof (struct in6_addr); i++) {
#if defined(sun)
                        if (ip6._S6_un._S6_u8[i] == 0 &&
#else
                        if (ip6.__u6_addr.__u6_addr8[i] == 0 &&
#endif
                            tryzero == -1 && i % 2 == 0) {
                              tryzero = i;
                              continue;
                        }

                        if (tryzero != -1 &&
#if defined(sun)
                            (ip6._S6_un._S6_u8[i] != 0 ||
#else
                            (ip6.__u6_addr.__u6_addr8[i] != 0 ||
#endif
                            i == sizeof (struct in6_addr) - 1)) {

                              if (i - tryzero <= numzero) {
                                    tryzero = -1;
                                    continue;
                              }

                              firstzero = tryzero;
                              numzero = i - i % 2 - tryzero;
                              tryzero = -1;

#if defined(sun)
                              if (ip6._S6_un._S6_u8[i] == 0 &&
#else
                              if (ip6.__u6_addr.__u6_addr8[i] == 0 &&
#endif
                                  i == sizeof (struct in6_addr) - 1)
                                    numzero += 2;
                        }
                  }
                  ASSERT(firstzero + numzero <= sizeof (struct in6_addr));

                  /*
                   * Check for an IPv4 embedded address.
                   */
                  v6end = sizeof (struct in6_addr) - 2;
                  if (IN6_IS_ADDR_V4MAPPED(&ip6) ||
                      IN6_IS_ADDR_V4COMPAT(&ip6)) {
                        for (i = sizeof (struct in6_addr) - 1;
                            i >= DTRACE_V4MAPPED_OFFSET; i--) {
                              ASSERT(end >= base);

#if defined(sun)
                              val = ip6._S6_un._S6_u8[i];
#else
                              val = ip6.__u6_addr.__u6_addr8[i];
#endif

                              if (val == 0) {
                                    *end-- = '0';
                              } else {
                                    for (; val; val /= 10) {
                                          *end-- = '0' + val % 10;
                                    }
                              }

                              if (i > DTRACE_V4MAPPED_OFFSET)
                                    *end-- = '.';
                        }

                        if (subr == DIF_SUBR_INET_NTOA6)
                              goto inetout;

                        /*
                         * Set v6end to skip the IPv4 address that
                         * we have already stringified.
                         */
                        v6end = 10;
                  }

                  /*
                   * Build the IPv6 string by working through the
                   * address in reverse.
                   */
                  for (i = v6end; i >= 0; i -= 2) {
                        ASSERT(end >= base);

                        if (i == firstzero + numzero - 2) {
                              *end-- = ':';
                              *end-- = ':';
                              i -= numzero - 2;
                              continue;
                        }

                        if (i < 14 && i != firstzero - 2)
                              *end-- = ':';

#if defined(sun)
                        val = (ip6._S6_un._S6_u8[i] << 8) +
                            ip6._S6_un._S6_u8[i + 1];
#else
                        val = (ip6.__u6_addr.__u6_addr8[i] << 8) +
                            ip6.__u6_addr.__u6_addr8[i + 1];
#endif

                        if (val == 0) {
                              *end-- = '0';
                        } else {
                              for (; val; val /= 16) {
                                    *end-- = digits[val % 16];
                              }
                        }
                  }
                  ASSERT(end + 1 >= base);

            } else {
                  /*
                   * The user didn't use AH_INET or AH_INET6.
                   */
                  DTRACE_CPUFLAG_SET(CPU_DTRACE_ILLOP);
                  regs[rd] = 0;
                  break;
            }

inetout:    regs[rd] = (uintptr_t)end + 1;
            mstate->dtms_scratch_ptr += size;
            break;
      }

      case DIF_SUBR_MEMREF: {
            uintptr_t size = 2 * sizeof(uintptr_t);
            uintptr_t *memref = (uintptr_t *) P2ROUNDUP(mstate->dtms_scratch_ptr, sizeof(uintptr_t));
            size_t scratch_size = ((uintptr_t) memref - mstate->dtms_scratch_ptr) + size;

            /* address and length */
            memref[0] = tupregs[0].dttk_value;
            memref[1] = tupregs[1].dttk_value;

            regs[rd] = (uintptr_t) memref;
            mstate->dtms_scratch_ptr += scratch_size;
            break;
      }

      case DIF_SUBR_TYPEREF: {
            uintptr_t size = 4 * sizeof(uintptr_t);
            uintptr_t *typeref = (uintptr_t *) P2ROUNDUP(mstate->dtms_scratch_ptr, sizeof(uintptr_t));
            size_t scratch_size = ((uintptr_t) typeref - mstate->dtms_scratch_ptr) + size;

            /* address, num_elements, type_str, type_len */
            typeref[0] = tupregs[0].dttk_value;
            typeref[1] = tupregs[1].dttk_value;
            typeref[2] = tupregs[2].dttk_value;
            typeref[3] = tupregs[3].dttk_value;

            regs[rd] = (uintptr_t) typeref;
            mstate->dtms_scratch_ptr += scratch_size;
            break;
      }
      }
}

/*
 * Emulate the execution of DTrace IR instructions specified by the given
 * DIF object.  This function is deliberately void of assertions as all of
 * the necessary checks are handled by a call to dtrace_difo_validate().
 */
static uint64_t
dtrace_dif_emulate(dtrace_difo_t *difo, dtrace_mstate_t *mstate,
    dtrace_vstate_t *vstate, dtrace_state_t *state)
{
      const dif_instr_t *text = difo->dtdo_buf;
      const uint_t textlen = difo->dtdo_len;
      const char *strtab = difo->dtdo_strtab;
      const uint64_t *inttab = difo->dtdo_inttab;

      uint64_t rval = 0;
      dtrace_statvar_t *svar;
      dtrace_dstate_t *dstate = &vstate->dtvs_dynvars;
      dtrace_difv_t *v;
      volatile uint16_t *flags = &cpu_core[curcpu].cpuc_dtrace_flags;
      volatile uintptr_t *illval = &cpu_core[curcpu].cpuc_dtrace_illval;

      dtrace_key_t tupregs[DIF_DTR_NREGS + 2]; /* +2 for thread and id */
      uint64_t regs[DIF_DIR_NREGS];
      uint64_t *tmp;

      uint8_t cc_n = 0, cc_z = 0, cc_v = 0, cc_c = 0;
      int64_t cc_r;
      uint_t pc = 0, id, opc = 0;
      uint8_t ttop = 0;
      dif_instr_t instr;
      uint_t r1, r2, rd;

      /*
       * We stash the current DIF object into the machine state: we need it
       * for subsequent access checking.
       */
      mstate->dtms_difo = difo;

      regs[DIF_REG_R0] = 0;         /* %r0 is fixed at zero */

      while (pc < textlen && !(*flags & CPU_DTRACE_FAULT)) {
            opc = pc;

            instr = text[pc++];
            r1 = DIF_INSTR_R1(instr);
            r2 = DIF_INSTR_R2(instr);
            rd = DIF_INSTR_RD(instr);

            switch (DIF_INSTR_OP(instr)) {
            case DIF_OP_OR:
                  regs[rd] = regs[r1] | regs[r2];
                  break;
            case DIF_OP_XOR:
                  regs[rd] = regs[r1] ^ regs[r2];
                  break;
            case DIF_OP_AND:
                  regs[rd] = regs[r1] & regs[r2];
                  break;
            case DIF_OP_SLL:
                  regs[rd] = regs[r1] << regs[r2];
                  break;
            case DIF_OP_SRL:
                  regs[rd] = regs[r1] >> regs[r2];
                  break;
            case DIF_OP_SUB:
                  regs[rd] = regs[r1] - regs[r2];
                  break;
            case DIF_OP_ADD:
                  regs[rd] = regs[r1] + regs[r2];
                  break;
            case DIF_OP_MUL:
                  regs[rd] = regs[r1] * regs[r2];
                  break;
            case DIF_OP_SDIV:
                  if (regs[r2] == 0) {
                        regs[rd] = 0;
                        *flags |= CPU_DTRACE_DIVZERO;
                  } else {
                        regs[rd] = (int64_t)regs[r1] /
                            (int64_t)regs[r2];
                  }
                  break;

            case DIF_OP_UDIV:
                  if (regs[r2] == 0) {
                        regs[rd] = 0;
                        *flags |= CPU_DTRACE_DIVZERO;
                  } else {
                        regs[rd] = regs[r1] / regs[r2];
                  }
                  break;

            case DIF_OP_SREM:
                  if (regs[r2] == 0) {
                        regs[rd] = 0;
                        *flags |= CPU_DTRACE_DIVZERO;
                  } else {
                        regs[rd] = (int64_t)regs[r1] %
                            (int64_t)regs[r2];
                  }
                  break;

            case DIF_OP_UREM:
                  if (regs[r2] == 0) {
                        regs[rd] = 0;
                        *flags |= CPU_DTRACE_DIVZERO;
                  } else {
                        regs[rd] = regs[r1] % regs[r2];
                  }
                  break;

            case DIF_OP_NOT:
                  regs[rd] = ~regs[r1];
                  break;
            case DIF_OP_MOV:
                  regs[rd] = regs[r1];
                  break;
            case DIF_OP_CMP:
                  cc_r = regs[r1] - regs[r2];
                  cc_n = cc_r < 0;
                  cc_z = cc_r == 0;
                  cc_v = 0;
                  cc_c = regs[r1] < regs[r2];
                  break;
            case DIF_OP_TST:
                  cc_n = cc_v = cc_c = 0;
                  cc_z = regs[r1] == 0;
                  break;
            case DIF_OP_BA:
                  pc = DIF_INSTR_LABEL(instr);
                  break;
            case DIF_OP_BE:
                  if (cc_z)
                        pc = DIF_INSTR_LABEL(instr);
                  break;
            case DIF_OP_BNE:
                  if (cc_z == 0)
                        pc = DIF_INSTR_LABEL(instr);
                  break;
            case DIF_OP_BG:
                  if ((cc_z | (cc_n ^ cc_v)) == 0)
                        pc = DIF_INSTR_LABEL(instr);
                  break;
            case DIF_OP_BGU:
                  if ((cc_c | cc_z) == 0)
                        pc = DIF_INSTR_LABEL(instr);
                  break;
            case DIF_OP_BGE:
                  if ((cc_n ^ cc_v) == 0)
                        pc = DIF_INSTR_LABEL(instr);
                  break;
            case DIF_OP_BGEU:
                  if (cc_c == 0)
                        pc = DIF_INSTR_LABEL(instr);
                  break;
            case DIF_OP_BL:
                  if (cc_n ^ cc_v)
                        pc = DIF_INSTR_LABEL(instr);
                  break;
            case DIF_OP_BLU:
                  if (cc_c)
                        pc = DIF_INSTR_LABEL(instr);
                  break;
            case DIF_OP_BLE:
                  if (cc_z | (cc_n ^ cc_v))
                        pc = DIF_INSTR_LABEL(instr);
                  break;
            case DIF_OP_BLEU:
                  if (cc_c | cc_z)
                        pc = DIF_INSTR_LABEL(instr);
                  break;
            case DIF_OP_RLDSB:
                  if (!dtrace_canstore(regs[r1], 1, mstate, vstate)) {
                        *flags |= CPU_DTRACE_KPRIV;
                        *illval = regs[r1];
                        break;
                  }
                  /*FALLTHROUGH*/
            case DIF_OP_LDSB:
                  regs[rd] = (int8_t)dtrace_load8(regs[r1]);
                  break;
            case DIF_OP_RLDSH:
                  if (!dtrace_canstore(regs[r1], 2, mstate, vstate)) {
                        *flags |= CPU_DTRACE_KPRIV;
                        *illval = regs[r1];
                        break;
                  }
                  /*FALLTHROUGH*/
            case DIF_OP_LDSH:
                  regs[rd] = (int16_t)dtrace_load16(regs[r1]);
                  break;
            case DIF_OP_RLDSW:
                  if (!dtrace_canstore(regs[r1], 4, mstate, vstate)) {
                        *flags |= CPU_DTRACE_KPRIV;
                        *illval = regs[r1];
                        break;
                  }
                  /*FALLTHROUGH*/
            case DIF_OP_LDSW:
                  regs[rd] = (int32_t)dtrace_load32(regs[r1]);
                  break;
            case DIF_OP_RLDUB:
                  if (!dtrace_canstore(regs[r1], 1, mstate, vstate)) {
                        *flags |= CPU_DTRACE_KPRIV;
                        *illval = regs[r1];
                        break;
                  }
                  /*FALLTHROUGH*/
            case DIF_OP_LDUB:
                  regs[rd] = dtrace_load8(regs[r1]);
                  break;
            case DIF_OP_RLDUH:
                  if (!dtrace_canstore(regs[r1], 2, mstate, vstate)) {
                        *flags |= CPU_DTRACE_KPRIV;
                        *illval = regs[r1];
                        break;
                  }
                  /*FALLTHROUGH*/
            case DIF_OP_LDUH:
                  regs[rd] = dtrace_load16(regs[r1]);
                  break;
            case DIF_OP_RLDUW:
                  if (!dtrace_canstore(regs[r1], 4, mstate, vstate)) {
                        *flags |= CPU_DTRACE_KPRIV;
                        *illval = regs[r1];
                        break;
                  }
                  /*FALLTHROUGH*/
            case DIF_OP_LDUW:
                  regs[rd] = dtrace_load32(regs[r1]);
                  break;
            case DIF_OP_RLDX:
                  if (!dtrace_canstore(regs[r1], 8, mstate, vstate)) {
                        *flags |= CPU_DTRACE_KPRIV;
                        *illval = regs[r1];
                        break;
                  }
                  /*FALLTHROUGH*/
            case DIF_OP_LDX:
                  regs[rd] = dtrace_load64(regs[r1]);
                  break;
            case DIF_OP_ULDSB:
                  regs[rd] = (int8_t)
                      dtrace_fuword8((void *)(uintptr_t)regs[r1]);
                  break;
            case DIF_OP_ULDSH:
                  regs[rd] = (int16_t)
                      dtrace_fuword16((void *)(uintptr_t)regs[r1]);
                  break;
            case DIF_OP_ULDSW:
                  regs[rd] = (int32_t)
                      dtrace_fuword32((void *)(uintptr_t)regs[r1]);
                  break;
            case DIF_OP_ULDUB:
                  regs[rd] =
                      dtrace_fuword8((void *)(uintptr_t)regs[r1]);
                  break;
            case DIF_OP_ULDUH:
                  regs[rd] =
                      dtrace_fuword16((void *)(uintptr_t)regs[r1]);
                  break;
            case DIF_OP_ULDUW:
                  regs[rd] =
                      dtrace_fuword32((void *)(uintptr_t)regs[r1]);
                  break;
            case DIF_OP_ULDX:
                  regs[rd] =
                      dtrace_fuword64((void *)(uintptr_t)regs[r1]);
                  break;
            case DIF_OP_RET:
                  rval = regs[rd];
                  pc = textlen;
                  break;
            case DIF_OP_NOP:
                  break;
            case DIF_OP_SETX:
                  regs[rd] = inttab[DIF_INSTR_INTEGER(instr)];
                  break;
            case DIF_OP_SETS:
                  regs[rd] = (uint64_t)(uintptr_t)
                      (strtab + DIF_INSTR_STRING(instr));
                  break;
            case DIF_OP_SCMP: {
                  size_t sz = state->dts_options[DTRACEOPT_STRSIZE];
                  uintptr_t s1 = regs[r1];
                  uintptr_t s2 = regs[r2];

                  if (s1 != 0 &&
                      !dtrace_strcanload(s1, sz, mstate, vstate))
                        break;
                  if (s2 != 0 &&
                      !dtrace_strcanload(s2, sz, mstate, vstate))
                        break;

                  cc_r = dtrace_strncmp((char *)s1, (char *)s2, sz);

                  cc_n = cc_r < 0;
                  cc_z = cc_r == 0;
                  cc_v = cc_c = 0;
                  break;
            }
            case DIF_OP_LDGA:
                  regs[rd] = dtrace_dif_variable(mstate, state,
                      r1, regs[r2]);
                  break;
            case DIF_OP_LDGS:
                  id = DIF_INSTR_VAR(instr);

                  if (id >= DIF_VAR_OTHER_UBASE) {
                        uintptr_t a;

                        id -= DIF_VAR_OTHER_UBASE;
                        svar = vstate->dtvs_globals[id];
                        ASSERT(svar != NULL);
                        v = &svar->dtsv_var;

                        if (!(v->dtdv_type.dtdt_flags & DIF_TF_BYREF)) {
                              regs[rd] = svar->dtsv_data;
                              break;
                        }

                        a = (uintptr_t)svar->dtsv_data;

                        if (*(uint8_t *)a == UINT8_MAX) {
                              /*
                               * If the 0th byte is set to UINT8_MAX
                               * then this is to be treated as a
                               * reference to a NULL variable.
                               */
                              regs[rd] = 0;
                        } else {
                              regs[rd] = a + sizeof (uint64_t);
                        }

                        break;
                  }

                  regs[rd] = dtrace_dif_variable(mstate, state, id, 0);
                  break;

            case DIF_OP_STGS:
                  id = DIF_INSTR_VAR(instr);

                  ASSERT(id >= DIF_VAR_OTHER_UBASE);
                  id -= DIF_VAR_OTHER_UBASE;

                  svar = vstate->dtvs_globals[id];
                  ASSERT(svar != NULL);
                  v = &svar->dtsv_var;

                  if (v->dtdv_type.dtdt_flags & DIF_TF_BYREF) {
                        uintptr_t a = (uintptr_t)svar->dtsv_data;

                        ASSERT(a != 0);
                        ASSERT(svar->dtsv_size != 0);

                        if (regs[rd] == 0) {
                              *(uint8_t *)a = UINT8_MAX;
                              break;
                        } else {
                              *(uint8_t *)a = 0;
                              a += sizeof (uint64_t);
                        }
                        if (!dtrace_vcanload(
                            (void *)(uintptr_t)regs[rd], &v->dtdv_type,
                            mstate, vstate))
                              break;

                        dtrace_vcopy((void *)(uintptr_t)regs[rd],
                            (void *)a, &v->dtdv_type);
                        break;
                  }

                  svar->dtsv_data = regs[rd];
                  break;

            case DIF_OP_LDTA:
                  /*
                   * There are no DTrace built-in thread-local arrays at
                   * present.  This opcode is saved for future work.
                   */
                  *flags |= CPU_DTRACE_ILLOP;
                  regs[rd] = 0;
                  break;

            case DIF_OP_LDLS:
                  id = DIF_INSTR_VAR(instr);

                  if (id < DIF_VAR_OTHER_UBASE) {
                        /*
                         * For now, this has no meaning.
                         */
                        regs[rd] = 0;
                        break;
                  }

                  id -= DIF_VAR_OTHER_UBASE;

                  ASSERT(id < vstate->dtvs_nlocals);
                  ASSERT(vstate->dtvs_locals != NULL);

                  svar = vstate->dtvs_locals[id];
                  ASSERT(svar != NULL);
                  v = &svar->dtsv_var;

                  if (v->dtdv_type.dtdt_flags & DIF_TF_BYREF) {
                        uintptr_t a = (uintptr_t)svar->dtsv_data;
                        size_t sz = v->dtdv_type.dtdt_size;

                        sz += sizeof (uint64_t);
                        ASSERT(svar->dtsv_size == NCPU * sz);
                        a += curcpu * sz;

                        if (*(uint8_t *)a == UINT8_MAX) {
                              /*
                               * If the 0th byte is set to UINT8_MAX
                               * then this is to be treated as a
                               * reference to a NULL variable.
                               */
                              regs[rd] = 0;
                        } else {
                              regs[rd] = a + sizeof (uint64_t);
                        }

                        break;
                  }

                  ASSERT(svar->dtsv_size == NCPU * sizeof (uint64_t));
                  tmp = (uint64_t *)(uintptr_t)svar->dtsv_data;
                  regs[rd] = tmp[curcpu];
                  break;

            case DIF_OP_STLS:
                  id = DIF_INSTR_VAR(instr);

                  ASSERT(id >= DIF_VAR_OTHER_UBASE);
                  id -= DIF_VAR_OTHER_UBASE;
                  ASSERT(id < vstate->dtvs_nlocals);

                  ASSERT(vstate->dtvs_locals != NULL);
                  svar = vstate->dtvs_locals[id];
                  ASSERT(svar != NULL);
                  v = &svar->dtsv_var;

                  if (v->dtdv_type.dtdt_flags & DIF_TF_BYREF) {
                        uintptr_t a = (uintptr_t)svar->dtsv_data;
                        size_t sz = v->dtdv_type.dtdt_size;

                        sz += sizeof (uint64_t);
                        ASSERT(svar->dtsv_size == NCPU * sz);
                        a += curcpu * sz;

                        if (regs[rd] == 0) {
                              *(uint8_t *)a = UINT8_MAX;
                              break;
                        } else {
                              *(uint8_t *)a = 0;
                              a += sizeof (uint64_t);
                        }

                        if (!dtrace_vcanload(
                            (void *)(uintptr_t)regs[rd], &v->dtdv_type,
                            mstate, vstate))
                              break;

                        dtrace_vcopy((void *)(uintptr_t)regs[rd],
                            (void *)a, &v->dtdv_type);
                        break;
                  }

                  ASSERT(svar->dtsv_size == NCPU * sizeof (uint64_t));
                  tmp = (uint64_t *)(uintptr_t)svar->dtsv_data;
                  tmp[curcpu] = regs[rd];
                  break;

            case DIF_OP_LDTS: {
                  dtrace_dynvar_t *dvar;
                  dtrace_key_t *key;

                  id = DIF_INSTR_VAR(instr);
                  ASSERT(id >= DIF_VAR_OTHER_UBASE);
                  id -= DIF_VAR_OTHER_UBASE;
                  v = &vstate->dtvs_tlocals[id];

                  key = &tupregs[DIF_DTR_NREGS];
                  key[0].dttk_value = (uint64_t)id;
                  key[0].dttk_size = 0;
                  DTRACE_TLS_THRKEY(key[1].dttk_value);
                  key[1].dttk_size = 0;

                  dvar = dtrace_dynvar(dstate, 2, key,
                      sizeof (uint64_t), DTRACE_DYNVAR_NOALLOC,
                      mstate, vstate);

                  if (dvar == NULL) {
                        regs[rd] = 0;
                        break;
                  }

                  if (v->dtdv_type.dtdt_flags & DIF_TF_BYREF) {
                        regs[rd] = (uint64_t)(uintptr_t)dvar->dtdv_data;
                  } else {
                        regs[rd] = *((uint64_t *)dvar->dtdv_data);
                  }

                  break;
            }

            case DIF_OP_STTS: {
                  dtrace_dynvar_t *dvar;
                  dtrace_key_t *key;

                  id = DIF_INSTR_VAR(instr);
                  ASSERT(id >= DIF_VAR_OTHER_UBASE);
                  id -= DIF_VAR_OTHER_UBASE;

                  key = &tupregs[DIF_DTR_NREGS];
                  key[0].dttk_value = (uint64_t)id;
                  key[0].dttk_size = 0;
                  DTRACE_TLS_THRKEY(key[1].dttk_value);
                  key[1].dttk_size = 0;
                  v = &vstate->dtvs_tlocals[id];

                  dvar = dtrace_dynvar(dstate, 2, key,
                      v->dtdv_type.dtdt_size > sizeof (uint64_t) ?
                      v->dtdv_type.dtdt_size : sizeof (uint64_t),
                      regs[rd] ? DTRACE_DYNVAR_ALLOC :
                      DTRACE_DYNVAR_DEALLOC, mstate, vstate);

                  /*
                   * Given that we're storing to thread-local data,
                   * we need to flush our predicate cache.
                   */
                  curthread->t_predcache = 0;

                  if (dvar == NULL)
                        break;

                  if (v->dtdv_type.dtdt_flags & DIF_TF_BYREF) {
                        if (!dtrace_vcanload(
                            (void *)(uintptr_t)regs[rd],
                            &v->dtdv_type, mstate, vstate))
                              break;

                        dtrace_vcopy((void *)(uintptr_t)regs[rd],
                            dvar->dtdv_data, &v->dtdv_type);
                  } else {
                        *((uint64_t *)dvar->dtdv_data) = regs[rd];
                  }

                  break;
            }

            case DIF_OP_SRA:
                  regs[rd] = (int64_t)regs[r1] >> regs[r2];
                  break;

            case DIF_OP_CALL:
                  dtrace_dif_subr(DIF_INSTR_SUBR(instr), rd,
                      regs, tupregs, ttop, mstate, state);
                  break;

            case DIF_OP_PUSHTR:
                  if (ttop == DIF_DTR_NREGS) {
                        *flags |= CPU_DTRACE_TUPOFLOW;
                        break;
                  }

                  if (r1 == DIF_TYPE_STRING) {
                        /*
                         * If this is a string type and the size is 0,
                         * we'll use the system-wide default string
                         * size.  Note that we are _not_ looking at
                         * the value of the DTRACEOPT_STRSIZE option;
                         * had this been set, we would expect to have
                         * a non-zero size value in the "pushtr".
                         */
                        tupregs[ttop].dttk_size =
                            dtrace_strlen((char *)(uintptr_t)regs[rd],
                            regs[r2] ? regs[r2] :
                            dtrace_strsize_default) + 1;
                  } else {
                        tupregs[ttop].dttk_size = regs[r2];
                  }

                  tupregs[ttop++].dttk_value = regs[rd];
                  break;

            case DIF_OP_PUSHTV:
                  if (ttop == DIF_DTR_NREGS) {
                        *flags |= CPU_DTRACE_TUPOFLOW;
                        break;
                  }

                  tupregs[ttop].dttk_value = regs[rd];
                  tupregs[ttop++].dttk_size = 0;
                  break;

            case DIF_OP_POPTS:
                  if (ttop != 0)
                        ttop--;
                  break;

            case DIF_OP_FLUSHTS:
                  ttop = 0;
                  break;

            case DIF_OP_LDGAA:
            case DIF_OP_LDTAA: {
                  dtrace_dynvar_t *dvar;
                  dtrace_key_t *key = tupregs;
                  uint_t nkeys = ttop;

                  id = DIF_INSTR_VAR(instr);
                  ASSERT(id >= DIF_VAR_OTHER_UBASE);
                  id -= DIF_VAR_OTHER_UBASE;

                  key[nkeys].dttk_value = (uint64_t)id;
                  key[nkeys++].dttk_size = 0;

                  if (DIF_INSTR_OP(instr) == DIF_OP_LDTAA) {
                        DTRACE_TLS_THRKEY(key[nkeys].dttk_value);
                        key[nkeys++].dttk_size = 0;
                        v = &vstate->dtvs_tlocals[id];
                  } else {
                        v = &vstate->dtvs_globals[id]->dtsv_var;
                  }

                  dvar = dtrace_dynvar(dstate, nkeys, key,
                      v->dtdv_type.dtdt_size > sizeof (uint64_t) ?
                      v->dtdv_type.dtdt_size : sizeof (uint64_t),
                      DTRACE_DYNVAR_NOALLOC, mstate, vstate);

                  if (dvar == NULL) {
                        regs[rd] = 0;
                        break;
                  }

                  if (v->dtdv_type.dtdt_flags & DIF_TF_BYREF) {
                        regs[rd] = (uint64_t)(uintptr_t)dvar->dtdv_data;
                  } else {
                        regs[rd] = *((uint64_t *)dvar->dtdv_data);
                  }

                  break;
            }

            case DIF_OP_STGAA:
            case DIF_OP_STTAA: {
                  dtrace_dynvar_t *dvar;
                  dtrace_key_t *key = tupregs;
                  uint_t nkeys = ttop;

                  id = DIF_INSTR_VAR(instr);
                  ASSERT(id >= DIF_VAR_OTHER_UBASE);
                  id -= DIF_VAR_OTHER_UBASE;

                  key[nkeys].dttk_value = (uint64_t)id;
                  key[nkeys++].dttk_size = 0;

                  if (DIF_INSTR_OP(instr) == DIF_OP_STTAA) {
                        DTRACE_TLS_THRKEY(key[nkeys].dttk_value);
                        key[nkeys++].dttk_size = 0;
                        v = &vstate->dtvs_tlocals[id];
                  } else {
                        v = &vstate->dtvs_globals[id]->dtsv_var;
                  }

                  dvar = dtrace_dynvar(dstate, nkeys, key,
                      v->dtdv_type.dtdt_size > sizeof (uint64_t) ?
                      v->dtdv_type.dtdt_size : sizeof (uint64_t),
                      regs[rd] ? DTRACE_DYNVAR_ALLOC :
                      DTRACE_DYNVAR_DEALLOC, mstate, vstate);

                  if (dvar == NULL)
                        break;

                  if (v->dtdv_type.dtdt_flags & DIF_TF_BYREF) {
                        if (!dtrace_vcanload(
                            (void *)(uintptr_t)regs[rd], &v->dtdv_type,
                            mstate, vstate))
                              break;

                        dtrace_vcopy((void *)(uintptr_t)regs[rd],
                            dvar->dtdv_data, &v->dtdv_type);
                  } else {
                        *((uint64_t *)dvar->dtdv_data) = regs[rd];
                  }

                  break;
            }

            case DIF_OP_ALLOCS: {
                  uintptr_t ptr = P2ROUNDUP(mstate->dtms_scratch_ptr, 8);
                  size_t size = ptr - mstate->dtms_scratch_ptr + regs[r1];

                  /*
                   * Rounding up the user allocation size could have
                   * overflowed large, bogus allocations (like -1ULL) to
                   * 0.
                   */
                  if (size < regs[r1] ||
                      !DTRACE_INSCRATCH(mstate, size)) {
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
                        regs[rd] = 0;
                        break;
                  }

                  dtrace_bzero((void *) mstate->dtms_scratch_ptr, size);
                  mstate->dtms_scratch_ptr += size;
                  regs[rd] = ptr;
                  break;
            }

            case DIF_OP_COPYS:
                  if (!dtrace_canstore(regs[rd], regs[r2],
                      mstate, vstate)) {
                        *flags |= CPU_DTRACE_BADADDR;
                        *illval = regs[rd];
                        break;
                  }

                  if (!dtrace_canload(regs[r1], regs[r2], mstate, vstate))
                        break;

                  dtrace_bcopy((void *)(uintptr_t)regs[r1],
                      (void *)(uintptr_t)regs[rd], (size_t)regs[r2]);
                  break;

            case DIF_OP_STB:
                  if (!dtrace_canstore(regs[rd], 1, mstate, vstate)) {
                        *flags |= CPU_DTRACE_BADADDR;
                        *illval = regs[rd];
                        break;
                  }
                  *((uint8_t *)(uintptr_t)regs[rd]) = (uint8_t)regs[r1];
                  break;

            case DIF_OP_STH:
                  if (!dtrace_canstore(regs[rd], 2, mstate, vstate)) {
                        *flags |= CPU_DTRACE_BADADDR;
                        *illval = regs[rd];
                        break;
                  }
                  if (regs[rd] & 1) {
                        *flags |= CPU_DTRACE_BADALIGN;
                        *illval = regs[rd];
                        break;
                  }
                  *((uint16_t *)(uintptr_t)regs[rd]) = (uint16_t)regs[r1];
                  break;

            case DIF_OP_STW:
                  if (!dtrace_canstore(regs[rd], 4, mstate, vstate)) {
                        *flags |= CPU_DTRACE_BADADDR;
                        *illval = regs[rd];
                        break;
                  }
                  if (regs[rd] & 3) {
                        *flags |= CPU_DTRACE_BADALIGN;
                        *illval = regs[rd];
                        break;
                  }
                  *((uint32_t *)(uintptr_t)regs[rd]) = (uint32_t)regs[r1];
                  break;

            case DIF_OP_STX:
                  if (!dtrace_canstore(regs[rd], 8, mstate, vstate)) {
                        *flags |= CPU_DTRACE_BADADDR;
                        *illval = regs[rd];
                        break;
                  }
                  if (regs[rd] & 7) {
                        *flags |= CPU_DTRACE_BADALIGN;
                        *illval = regs[rd];
                        break;
                  }
                  *((uint64_t *)(uintptr_t)regs[rd]) = regs[r1];
                  break;
            }
      }

      if (!(*flags & CPU_DTRACE_FAULT))
            return (rval);

      mstate->dtms_fltoffs = opc * sizeof (dif_instr_t);
      mstate->dtms_present |= DTRACE_MSTATE_FLTOFFS;

      return (0);
}

static void
dtrace_action_breakpoint(dtrace_ecb_t *ecb)
{
      dtrace_probe_t *probe = ecb->dte_probe;
      dtrace_provider_t *prov = probe->dtpr_provider;
      char c[DTRACE_FULLNAMELEN + 80], *str;
      char *msg = "dtrace: breakpoint action at probe ";
      char *ecbmsg = " (ecb ";
      uintptr_t mask = (0xf << (sizeof (uintptr_t) * NBBY / 4));
      uintptr_t val = (uintptr_t)ecb;
      int shift = (sizeof (uintptr_t) * NBBY) - 4, i = 0;

      if (dtrace_destructive_disallow)
            return;

      /*
       * It's impossible to be taking action on the NULL probe.
       */
      ASSERT(probe != NULL);

      /*
       * This is a poor man's (destitute man's?) sprintf():  we want to
       * print the provider name, module name, function name and name of
       * the probe, along with the hex address of the ECB with the breakpoint
       * action -- all of which we must place in the character buffer by
       * hand.
       */
      while (*msg != '\0')
            c[i++] = *msg++;

      for (str = prov->dtpv_name; *str != '\0'; str++)
            c[i++] = *str;
      c[i++] = ':';

      for (str = probe->dtpr_mod; *str != '\0'; str++)
            c[i++] = *str;
      c[i++] = ':';

      for (str = probe->dtpr_func; *str != '\0'; str++)
            c[i++] = *str;
      c[i++] = ':';

      for (str = probe->dtpr_name; *str != '\0'; str++)
            c[i++] = *str;

      while (*ecbmsg != '\0')
            c[i++] = *ecbmsg++;

      while (shift >= 0) {
            mask = (uintptr_t)0xf << shift;

            if (val >= ((uintptr_t)1 << shift))
                  c[i++] = "0123456789abcdef"[(val & mask) >> shift];
            shift -= 4;
      }

      c[i++] = ')';
      c[i] = '\0';

#if defined(sun)
      debug_enter(c);
#else
      kdb_enter(KDB_WHY_DTRACE, "breakpoint action");
#endif
}

static void
dtrace_action_panic(dtrace_ecb_t *ecb)
{
      dtrace_probe_t *probe = ecb->dte_probe;

      /*
       * It's impossible to be taking action on the NULL probe.
       */
      ASSERT(probe != NULL);

      if (dtrace_destructive_disallow)
            return;

      if (dtrace_panicked != NULL)
            return;

      if (dtrace_casptr(&dtrace_panicked, NULL, curthread) != NULL)
            return;

      /*
       * We won the right to panic.  (We want to be sure that only one
       * thread calls panic() from dtrace_probe(), and that panic() is
       * called exactly once.)
       */
      dtrace_panic("dtrace: panic action at probe %s:%s:%s:%s (ecb %p)",
          probe->dtpr_provider->dtpv_name, probe->dtpr_mod,
          probe->dtpr_func, probe->dtpr_name, (void *)ecb);
}

static void
dtrace_action_raise(uint64_t sig)
{
      if (dtrace_destructive_disallow)
            return;

      if (sig >= NSIG) {
            DTRACE_CPUFLAG_SET(CPU_DTRACE_ILLOP);
            return;
      }

#if defined(sun)
      /*
       * raise() has a queue depth of 1 -- we ignore all subsequent
       * invocations of the raise() action.
       */
      if (curthread->t_dtrace_sig == 0)
            curthread->t_dtrace_sig = (uint8_t)sig;

      curthread->t_sig_check = 1;
      aston(curthread);
#else
      struct proc *p = curproc;
      PROC_LOCK(p);
      psignal(p, sig);
      PROC_UNLOCK(p);
#endif
}

static void
dtrace_action_stop(void)
{
      if (dtrace_destructive_disallow)
            return;

#if defined(sun)
      if (!curthread->t_dtrace_stop) {
            curthread->t_dtrace_stop = 1;
            curthread->t_sig_check = 1;
            aston(curthread);
      }
#else
      struct proc *p = curproc;
      PROC_LOCK(p);
      psignal(p, SIGSTOP);
      PROC_UNLOCK(p);
#endif
}

static void
dtrace_action_chill(dtrace_mstate_t *mstate, hrtime_t val)
{
      hrtime_t now;
      volatile uint16_t *flags;
#if defined(sun)
      cpu_t *cpu = CPU;
#else
      cpu_t *cpu = &solaris_cpu[curcpu];
#endif

      if (dtrace_destructive_disallow)
            return;

      flags = (volatile uint16_t *)&cpu_core[cpu->cpu_id].cpuc_dtrace_flags;

      now = dtrace_gethrtime();

      if (now - cpu->cpu_dtrace_chillmark > dtrace_chill_interval) {
            /*
             * We need to advance the mark to the current time.
             */
            cpu->cpu_dtrace_chillmark = now;
            cpu->cpu_dtrace_chilled = 0;
      }

      /*
       * Now check to see if the requested chill time would take us over
       * the maximum amount of time allowed in the chill interval.  (Or
       * worse, if the calculation itself induces overflow.)
       */
      if (cpu->cpu_dtrace_chilled + val > dtrace_chill_max ||
          cpu->cpu_dtrace_chilled + val < cpu->cpu_dtrace_chilled) {
            *flags |= CPU_DTRACE_ILLOP;
            return;
      }

      while (dtrace_gethrtime() - now < val)
            continue;

      /*
       * Normally, we assure that the value of the variable "timestamp" does
       * not change within an ECB.  The presence of chill() represents an
       * exception to this rule, however.
       */
      mstate->dtms_present &= ~DTRACE_MSTATE_TIMESTAMP;
      cpu->cpu_dtrace_chilled += val;
}

#if defined(sun)
static void
dtrace_action_ustack(dtrace_mstate_t *mstate, dtrace_state_t *state,
    uint64_t *buf, uint64_t arg)
{
      int nframes = DTRACE_USTACK_NFRAMES(arg);
      int strsize = DTRACE_USTACK_STRSIZE(arg);
      uint64_t *pcs = &buf[1], *fps;
      char *str = (char *)&pcs[nframes];
      int size, offs = 0, i, j;
      uintptr_t old = mstate->dtms_scratch_ptr, saved;
      uint16_t *flags = &cpu_core[curcpu].cpuc_dtrace_flags;
      char *sym;

      /*
       * Should be taking a faster path if string space has not been
       * allocated.
       */
      ASSERT(strsize != 0);

      /*
       * We will first allocate some temporary space for the frame pointers.
       */
      fps = (uint64_t *)P2ROUNDUP(mstate->dtms_scratch_ptr, 8);
      size = (uintptr_t)fps - mstate->dtms_scratch_ptr +
          (nframes * sizeof (uint64_t));

      if (!DTRACE_INSCRATCH(mstate, size)) {
            /*
             * Not enough room for our frame pointers -- need to indicate
             * that we ran out of scratch space.
             */
            DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
            return;
      }

      mstate->dtms_scratch_ptr += size;
      saved = mstate->dtms_scratch_ptr;

      /*
       * Now get a stack with both program counters and frame pointers.
       */
      DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
      dtrace_getufpstack(buf, fps, nframes + 1);
      DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT);

      /*
       * If that faulted, we're cooked.
       */
      if (*flags & CPU_DTRACE_FAULT)
            goto out;

      /*
       * Now we want to walk up the stack, calling the USTACK helper.  For
       * each iteration, we restore the scratch pointer.
       */
      for (i = 0; i < nframes; i++) {
            mstate->dtms_scratch_ptr = saved;

            if (offs >= strsize)
                  break;

            sym = (char *)(uintptr_t)dtrace_helper(
                DTRACE_HELPER_ACTION_USTACK,
                mstate, state, pcs[i], fps[i]);

            /*
             * If we faulted while running the helper, we're going to
             * clear the fault and null out the corresponding string.
             */
            if (*flags & CPU_DTRACE_FAULT) {
                  *flags &= ~CPU_DTRACE_FAULT;
                  str[offs++] = '\0';
                  continue;
            }

            if (sym == NULL) {
                  str[offs++] = '\0';
                  continue;
            }

            DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);

            /*
             * Now copy in the string that the helper returned to us.
             */
            for (j = 0; offs + j < strsize; j++) {
                  if ((str[offs + j] = sym[j]) == '\0')
                        break;
            }

            DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT);

            offs += j + 1;
      }

      if (offs >= strsize) {
            /*
             * If we didn't have room for all of the strings, we don't
             * abort processing -- this needn't be a fatal error -- but we
             * still want to increment a counter (dts_stkstroverflows) to
             * allow this condition to be warned about.  (If this is from
             * a jstack() action, it is easily tuned via jstackstrsize.)
             */
            dtrace_error(&state->dts_stkstroverflows);
      }

      while (offs < strsize)
            str[offs++] = '\0';

out:
      mstate->dtms_scratch_ptr = old;
}
#endif

/*
 * If you're looking for the epicenter of DTrace, you just found it.  This
 * is the function called by the provider to fire a probe -- from which all
 * subsequent probe-context DTrace activity emanates.
 */
void
dtrace_probe(dtrace_id_t id, uintptr_t arg0, uintptr_t arg1,
    uintptr_t arg2, uintptr_t arg3, uintptr_t arg4)
{
      processorid_t cpuid;
      dtrace_icookie_t cookie;
      dtrace_probe_t *probe;
      dtrace_mstate_t mstate;
      dtrace_ecb_t *ecb;
      dtrace_action_t *act;
      intptr_t offs;
      size_t size;
      int vtime, onintr;
      volatile uint16_t *flags;
      hrtime_t now;

#if defined(sun)
      /*
       * Kick out immediately if this CPU is still being born (in which case
       * curthread will be set to -1) or the current thread can't allow
       * probes in its current context.
       */
      if (((uintptr_t)curthread & 1) || (curthread->t_flag & T_DONTDTRACE))
            return;
#endif

      cookie = dtrace_interrupt_disable();
      probe = dtrace_probes[id - 1];
      cpuid = curcpu;
      onintr = CPU_ON_INTR(CPU);

      if (!onintr && probe->dtpr_predcache != DTRACE_CACHEIDNONE &&
          probe->dtpr_predcache == curthread->t_predcache) {
            /*
             * We have hit in the predicate cache; we know that
             * this predicate would evaluate to be false.
             */
            dtrace_interrupt_enable(cookie);
            return;
      }

#if defined(sun)
      if (panic_quiesce) {
#else
      if (panicstr != NULL) {
#endif
            /*
             * We don't trace anything if we're panicking.
             */
            dtrace_interrupt_enable(cookie);
            return;
      }

      now = dtrace_gethrtime();
      vtime = dtrace_vtime_references != 0;

      if (vtime && curthread->t_dtrace_start)
            curthread->t_dtrace_vtime += now - curthread->t_dtrace_start;

      mstate.dtms_difo = NULL;
      mstate.dtms_probe = probe;
      mstate.dtms_strtok = 0;
      mstate.dtms_arg[0] = arg0;
      mstate.dtms_arg[1] = arg1;
      mstate.dtms_arg[2] = arg2;
      mstate.dtms_arg[3] = arg3;
      mstate.dtms_arg[4] = arg4;

      flags = (volatile uint16_t *)&cpu_core[cpuid].cpuc_dtrace_flags;

      for (ecb = probe->dtpr_ecb; ecb != NULL; ecb = ecb->dte_next) {
            dtrace_predicate_t *pred = ecb->dte_predicate;
            dtrace_state_t *state = ecb->dte_state;
            dtrace_buffer_t *buf = &state->dts_buffer[cpuid];
            dtrace_buffer_t *aggbuf = &state->dts_aggbuffer[cpuid];
            dtrace_vstate_t *vstate = &state->dts_vstate;
            dtrace_provider_t *prov = probe->dtpr_provider;
            int committed = 0;
            caddr_t tomax;

            /*
             * A little subtlety with the following (seemingly innocuous)
             * declaration of the automatic 'val':  by looking at the
             * code, you might think that it could be declared in the
             * action processing loop, below.  (That is, it's only used in
             * the action processing loop.)  However, it must be declared
             * out of that scope because in the case of DIF expression
             * arguments to aggregating actions, one iteration of the
             * action loop will use the last iteration's value.
             */
            uint64_t val = 0;

            mstate.dtms_present = DTRACE_MSTATE_ARGS | DTRACE_MSTATE_PROBE;
            *flags &= ~CPU_DTRACE_ERROR;

            if (prov == dtrace_provider) {
                  /*
                   * If dtrace itself is the provider of this probe,
                   * we're only going to continue processing the ECB if
                   * arg0 (the dtrace_state_t) is equal to the ECB's
                   * creating state.  (This prevents disjoint consumers
                   * from seeing one another's metaprobes.)
                   */
                  if (arg0 != (uint64_t)(uintptr_t)state)
                        continue;
            }

            if (state->dts_activity != DTRACE_ACTIVITY_ACTIVE) {
                  /*
                   * We're not currently active.  If our provider isn't
                   * the dtrace pseudo provider, we're not interested.
                   */
                  if (prov != dtrace_provider)
                        continue;

                  /*
                   * Now we must further check if we are in the BEGIN
                   * probe.  If we are, we will only continue processing
                   * if we're still in WARMUP -- if one BEGIN enabling
                   * has invoked the exit() action, we don't want to
                   * evaluate subsequent BEGIN enablings.
                   */
                  if (probe->dtpr_id == dtrace_probeid_begin &&
                      state->dts_activity != DTRACE_ACTIVITY_WARMUP) {
                        ASSERT(state->dts_activity ==
                            DTRACE_ACTIVITY_DRAINING);
                        continue;
                  }
            }

            if (ecb->dte_cond) {
                  /*
                   * If the dte_cond bits indicate that this
                   * consumer is only allowed to see user-mode firings
                   * of this probe, call the provider's dtps_usermode()
                   * entry point to check that the probe was fired
                   * while in a user context. Skip this ECB if that's
                   * not the case.
                   */
                  if ((ecb->dte_cond & DTRACE_COND_USERMODE) &&
                      prov->dtpv_pops.dtps_usermode(prov->dtpv_arg,
                      probe->dtpr_id, probe->dtpr_arg) == 0)
                        continue;

#if defined(sun)
                  /*
                   * This is more subtle than it looks. We have to be
                   * absolutely certain that CRED() isn't going to
                   * change out from under us so it's only legit to
                   * examine that structure if we're in constrained
                   * situations. Currently, the only times we'll this
                   * check is if a non-super-user has enabled the
                   * profile or syscall providers -- providers that
                   * allow visibility of all processes. For the
                   * profile case, the check above will ensure that
                   * we're examining a user context.
                   */
                  if (ecb->dte_cond & DTRACE_COND_OWNER) {
                        cred_t *cr;
                        cred_t *s_cr =
                            ecb->dte_state->dts_cred.dcr_cred;
                        proc_t *proc;

                        ASSERT(s_cr != NULL);

                        if ((cr = CRED()) == NULL ||
                            s_cr->cr_uid != cr->cr_uid ||
                            s_cr->cr_uid != cr->cr_ruid ||
                            s_cr->cr_uid != cr->cr_suid ||
                            s_cr->cr_gid != cr->cr_gid ||
                            s_cr->cr_gid != cr->cr_rgid ||
                            s_cr->cr_gid != cr->cr_sgid ||
                            (proc = ttoproc(curthread)) == NULL ||
                            (proc->p_flag & SNOCD))
                              continue;
                  }

                  if (ecb->dte_cond & DTRACE_COND_ZONEOWNER) {
                        cred_t *cr;
                        cred_t *s_cr =
                            ecb->dte_state->dts_cred.dcr_cred;

                        ASSERT(s_cr != NULL);

                        if ((cr = CRED()) == NULL ||
                            s_cr->cr_zone->zone_id !=
                            cr->cr_zone->zone_id)
                              continue;
                  }
#endif
            }

            if (now - state->dts_alive > dtrace_deadman_timeout) {
                  /*
                   * We seem to be dead.  Unless we (a) have kernel
                   * destructive permissions (b) have expicitly enabled
                   * destructive actions and (c) destructive actions have
                   * not been disabled, we're going to transition into
                   * the KILLED state, from which no further processing
                   * on this state will be performed.
                   */
                  if (!dtrace_priv_kernel_destructive(state) ||
                      !state->dts_cred.dcr_destructive ||
                      dtrace_destructive_disallow) {
                        void *activity = &state->dts_activity;
                        dtrace_activity_t current;

                        do {
                              current = state->dts_activity;
                        } while (dtrace_cas32(activity, current,
                            DTRACE_ACTIVITY_KILLED) != current);

                        continue;
                  }
            }

            if ((offs = dtrace_buffer_reserve(buf, ecb->dte_needed,
                ecb->dte_alignment, state, &mstate)) < 0)
                  continue;

            tomax = buf->dtb_tomax;
            ASSERT(tomax != NULL);

            if (ecb->dte_size != 0)
                  DTRACE_STORE(uint32_t, tomax, offs, ecb->dte_epid);

            mstate.dtms_epid = ecb->dte_epid;
            mstate.dtms_present |= DTRACE_MSTATE_EPID;

            if (state->dts_cred.dcr_visible & DTRACE_CRV_KERNEL)
                  mstate.dtms_access = DTRACE_ACCESS_KERNEL;
            else
                  mstate.dtms_access = 0;

            if (pred != NULL) {
                  dtrace_difo_t *dp = pred->dtp_difo;
                  int rval;

                  rval = dtrace_dif_emulate(dp, &mstate, vstate, state);

                  if (!(*flags & CPU_DTRACE_ERROR) && !rval) {
                        dtrace_cacheid_t cid = probe->dtpr_predcache;

                        if (cid != DTRACE_CACHEIDNONE && !onintr) {
                              /*
                               * Update the predicate cache...
                               */
                              ASSERT(cid == pred->dtp_cacheid);
                              curthread->t_predcache = cid;
                        }

                        continue;
                  }
            }

            for (act = ecb->dte_action; !(*flags & CPU_DTRACE_ERROR) &&
                act != NULL; act = act->dta_next) {
                  size_t valoffs;
                  dtrace_difo_t *dp;
                  dtrace_recdesc_t *rec = &act->dta_rec;

                  size = rec->dtrd_size;
                  valoffs = offs + rec->dtrd_offset;

                  if (DTRACEACT_ISAGG(act->dta_kind)) {
                        uint64_t v = 0xbad;
                        dtrace_aggregation_t *agg;

                        agg = (dtrace_aggregation_t *)act;

                        if ((dp = act->dta_difo) != NULL)
                              v = dtrace_dif_emulate(dp,
                                  &mstate, vstate, state);

                        if (*flags & CPU_DTRACE_ERROR)
                              continue;

                        /*
                         * Note that we always pass the expression
                         * value from the previous iteration of the
                         * action loop.  This value will only be used
                         * if there is an expression argument to the
                         * aggregating action, denoted by the
                         * dtag_hasarg field.
                         */
                        dtrace_aggregate(agg, buf,
                            offs, aggbuf, v, val);
                        continue;
                  }

                  switch (act->dta_kind) {
                  case DTRACEACT_STOP:
                        if (dtrace_priv_proc_destructive(state))
                              dtrace_action_stop();
                        continue;

                  case DTRACEACT_BREAKPOINT:
                        if (dtrace_priv_kernel_destructive(state))
                              dtrace_action_breakpoint(ecb);
                        continue;

                  case DTRACEACT_PANIC:
                        if (dtrace_priv_kernel_destructive(state))
                              dtrace_action_panic(ecb);
                        continue;

                  case DTRACEACT_STACK:
                        if (!dtrace_priv_kernel(state))
                              continue;

                        dtrace_getpcstack((pc_t *)(tomax + valoffs),
                            size / sizeof (pc_t), probe->dtpr_aframes,
                            DTRACE_ANCHORED(probe) ? NULL :
                            (uint32_t *)arg0);
                        continue;

#if defined(sun)
                  case DTRACEACT_JSTACK:
                  case DTRACEACT_USTACK:
                        if (!dtrace_priv_proc(state))
                              continue;

                        /*
                         * See comment in DIF_VAR_PID.
                         */
                        if (DTRACE_ANCHORED(mstate.dtms_probe) &&
                            CPU_ON_INTR(CPU)) {
                              int depth = DTRACE_USTACK_NFRAMES(
                                  rec->dtrd_arg) + 1;

                              dtrace_bzero((void *)(tomax + valoffs),
                                  DTRACE_USTACK_STRSIZE(rec->dtrd_arg)
                                  + depth * sizeof (uint64_t));

                              continue;
                        }

                        if (DTRACE_USTACK_STRSIZE(rec->dtrd_arg) != 0 &&
                            curproc->p_dtrace_helpers != NULL) {
                              /*
                               * This is the slow path -- we have
                               * allocated string space, and we're
                               * getting the stack of a process that
                               * has helpers.  Call into a separate
                               * routine to perform this processing.
                               */
                              dtrace_action_ustack(&mstate, state,
                                  (uint64_t *)(tomax + valoffs),
                                  rec->dtrd_arg);
                              continue;
                        }

                        DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
                        dtrace_getupcstack((uint64_t *)
                            (tomax + valoffs),
                            DTRACE_USTACK_NFRAMES(rec->dtrd_arg) + 1);
                        DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT);
                        continue;
#endif

                  default:
                        break;
                  }

                  dp = act->dta_difo;
                  ASSERT(dp != NULL);

                  val = dtrace_dif_emulate(dp, &mstate, vstate, state);

                  if (*flags & CPU_DTRACE_ERROR)
                        continue;

                  switch (act->dta_kind) {
                  case DTRACEACT_SPECULATE:
                        ASSERT(buf == &state->dts_buffer[cpuid]);
                        buf = dtrace_speculation_buffer(state,
                            cpuid, val);

                        if (buf == NULL) {
                              *flags |= CPU_DTRACE_DROP;
                              continue;
                        }

                        offs = dtrace_buffer_reserve(buf,
                            ecb->dte_needed, ecb->dte_alignment,
                            state, NULL);

                        if (offs < 0) {
                              *flags |= CPU_DTRACE_DROP;
                              continue;
                        }

                        tomax = buf->dtb_tomax;
                        ASSERT(tomax != NULL);

                        if (ecb->dte_size != 0)
                              DTRACE_STORE(uint32_t, tomax, offs,
                                  ecb->dte_epid);
                        continue;

                  case DTRACEACT_PRINTM: {
                        /* The DIF returns a 'memref'. */
                        uintptr_t *memref = (uintptr_t *)(uintptr_t) val;

                        /* Get the size from the memref. */
                        size = memref[1];

                        /*
                         * Check if the size exceeds the allocated
                         * buffer size.
                         */
                        if (size + sizeof(uintptr_t) > dp->dtdo_rtype.dtdt_size) {
                              /* Flag a drop! */
                              *flags |= CPU_DTRACE_DROP;
                              continue;
                        }

                        /* Store the size in the buffer first. */
                        DTRACE_STORE(uintptr_t, tomax,
                            valoffs, size);

                        /*
                         * Offset the buffer address to the start
                         * of the data.
                         */
                        valoffs += sizeof(uintptr_t);

                        /*
                         * Reset to the memory address rather than
                         * the memref array, then let the BYREF
                         * code below do the work to store the 
                         * memory data in the buffer.
                         */
                        val = memref[0];
                        break;
                  }

                  case DTRACEACT_PRINTT: {
                        /* The DIF returns a 'typeref'. */
                        uintptr_t *typeref = (uintptr_t *)(uintptr_t) val;
                        char c = '\0' + 1;
                        size_t s;

                        /*
                         * Get the type string length and round it
                         * up so that the data that follows is
                         * aligned for easy access.
                         */
                        size_t typs = strlen((char *) typeref[2]) + 1;
                        typs = roundup(typs,  sizeof(uintptr_t));

                        /*
                         *Get the size from the typeref using the
                         * number of elements and the type size.
                         */
                        size = typeref[1] * typeref[3];

                        /*
                         * Check if the size exceeds the allocated
                         * buffer size.
                         */
                        if (size + typs + 2 * sizeof(uintptr_t) > dp->dtdo_rtype.dtdt_size) {
                              /* Flag a drop! */
                              *flags |= CPU_DTRACE_DROP;
                        
                        }

                        /* Store the size in the buffer first. */
                        DTRACE_STORE(uintptr_t, tomax,
                            valoffs, size);
                        valoffs += sizeof(uintptr_t);

                        /* Store the type size in the buffer. */
                        DTRACE_STORE(uintptr_t, tomax,
                            valoffs, typeref[3]);
                        valoffs += sizeof(uintptr_t);

                        val = typeref[2];

                        for (s = 0; s < typs; s++) {
                              if (c != '\0')
                                    c = dtrace_load8(val++);

                              DTRACE_STORE(uint8_t, tomax,
                                  valoffs++, c);
                        }

                        /*
                         * Reset to the memory address rather than
                         * the typeref array, then let the BYREF
                         * code below do the work to store the 
                         * memory data in the buffer.
                         */
                        val = typeref[0];
                        break;
                  }

                  case DTRACEACT_CHILL:
                        if (dtrace_priv_kernel_destructive(state))
                              dtrace_action_chill(&mstate, val);
                        continue;

                  case DTRACEACT_RAISE:
                        if (dtrace_priv_proc_destructive(state))
                              dtrace_action_raise(val);
                        continue;

                  case DTRACEACT_COMMIT:
                        ASSERT(!committed);

                        /*
                         * We need to commit our buffer state.
                         */
                        if (ecb->dte_size)
                              buf->dtb_offset = offs + ecb->dte_size;
                        buf = &state->dts_buffer[cpuid];
                        dtrace_speculation_commit(state, cpuid, val);
                        committed = 1;
                        continue;

                  case DTRACEACT_DISCARD:
                        dtrace_speculation_discard(state, cpuid, val);
                        continue;

                  case DTRACEACT_DIFEXPR:
                  case DTRACEACT_LIBACT:
                  case DTRACEACT_PRINTF:
                  case DTRACEACT_PRINTA:
                  case DTRACEACT_SYSTEM:
                  case DTRACEACT_FREOPEN:
                        break;

                  case DTRACEACT_SYM:
                  case DTRACEACT_MOD:
                        if (!dtrace_priv_kernel(state))
                              continue;
                        break;

                  case DTRACEACT_USYM:
                  case DTRACEACT_UMOD:
                  case DTRACEACT_UADDR: {
#if defined(sun)
                        struct pid *pid = curthread->t_procp->p_pidp;
#endif

                        if (!dtrace_priv_proc(state))
                              continue;

                        DTRACE_STORE(uint64_t, tomax,
#if defined(sun)
                            valoffs, (uint64_t)pid->pid_id);
#else
                            valoffs, (uint64_t) curproc->p_pid);
#endif
                        DTRACE_STORE(uint64_t, tomax,
                            valoffs + sizeof (uint64_t), val);

                        continue;
                  }

                  case DTRACEACT_EXIT: {
                        /*
                         * For the exit action, we are going to attempt
                         * to atomically set our activity to be
                         * draining.  If this fails (either because
                         * another CPU has beat us to the exit action,
                         * or because our current activity is something
                         * other than ACTIVE or WARMUP), we will
                         * continue.  This assures that the exit action
                         * can be successfully recorded at most once
                         * when we're in the ACTIVE state.  If we're
                         * encountering the exit() action while in
                         * COOLDOWN, however, we want to honor the new
                         * status code.  (We know that we're the only
                         * thread in COOLDOWN, so there is no race.)
                         */
                        void *activity = &state->dts_activity;
                        dtrace_activity_t current = state->dts_activity;

                        if (current == DTRACE_ACTIVITY_COOLDOWN)
                              break;

                        if (current != DTRACE_ACTIVITY_WARMUP)
                              current = DTRACE_ACTIVITY_ACTIVE;

                        if (dtrace_cas32(activity, current,
                            DTRACE_ACTIVITY_DRAINING) != current) {
                              *flags |= CPU_DTRACE_DROP;
                              continue;
                        }

                        break;
                  }

                  default:
                        ASSERT(0);
                  }

                  if (dp->dtdo_rtype.dtdt_flags & DIF_TF_BYREF) {
                        uintptr_t end = valoffs + size;

                        if (!dtrace_vcanload((void *)(uintptr_t)val,
                            &dp->dtdo_rtype, &mstate, vstate))
                              continue;

                        /*
                         * If this is a string, we're going to only
                         * load until we find the zero byte -- after
                         * which we'll store zero bytes.
                         */
                        if (dp->dtdo_rtype.dtdt_kind ==
                            DIF_TYPE_STRING) {
                              char c = '\0' + 1;
                              int intuple = act->dta_intuple;
                              size_t s;

                              for (s = 0; s < size; s++) {
                                    if (c != '\0')
                                          c = dtrace_load8(val++);

                                    DTRACE_STORE(uint8_t, tomax,
                                        valoffs++, c);

                                    if (c == '\0' && intuple)
                                          break;
                              }

                              continue;
                        }

                        while (valoffs < end) {
                              DTRACE_STORE(uint8_t, tomax, valoffs++,
                                  dtrace_load8(val++));
                        }

                        continue;
                  }

                  switch (size) {
                  case 0:
                        break;

                  case sizeof (uint8_t):
                        DTRACE_STORE(uint8_t, tomax, valoffs, val);
                        break;
                  case sizeof (uint16_t):
                        DTRACE_STORE(uint16_t, tomax, valoffs, val);
                        break;
                  case sizeof (uint32_t):
                        DTRACE_STORE(uint32_t, tomax, valoffs, val);
                        break;
                  case sizeof (uint64_t):
                        DTRACE_STORE(uint64_t, tomax, valoffs, val);
                        break;
                  default:
                        /*
                         * Any other size should have been returned by
                         * reference, not by value.
                         */
                        ASSERT(0);
                        break;
                  }
            }

            if (*flags & CPU_DTRACE_DROP)
                  continue;

            if (*flags & CPU_DTRACE_FAULT) {
                  int ndx;
                  dtrace_action_t *err;

                  buf->dtb_errors++;

                  if (probe->dtpr_id == dtrace_probeid_error) {
                        /*
                         * There's nothing we can do -- we had an
                         * error on the error probe.  We bump an
                         * error counter to at least indicate that
                         * this condition happened.
                         */
                        dtrace_error(&state->dts_dblerrors);
                        continue;
                  }

                  if (vtime) {
                        /*
                         * Before recursing on dtrace_probe(), we
                         * need to explicitly clear out our start
                         * time to prevent it from being accumulated
                         * into t_dtrace_vtime.
                         */
                        curthread->t_dtrace_start = 0;
                  }

                  /*
                   * Iterate over the actions to figure out which action
                   * we were processing when we experienced the error.
                   * Note that act points _past_ the faulting action; if
                   * act is ecb->dte_action, the fault was in the
                   * predicate, if it's ecb->dte_action->dta_next it's
                   * in action #1, and so on.
                   */
                  for (err = ecb->dte_action, ndx = 0;
                      err != act; err = err->dta_next, ndx++)
                        continue;

                  dtrace_probe_error(state, ecb->dte_epid, ndx,
                      (mstate.dtms_present & DTRACE_MSTATE_FLTOFFS) ?
                      mstate.dtms_fltoffs : -1, DTRACE_FLAGS2FLT(*flags),
                      cpu_core[cpuid].cpuc_dtrace_illval);

                  continue;
            }

            if (!committed)
                  buf->dtb_offset = offs + ecb->dte_size;
      }

      if (vtime)
            curthread->t_dtrace_start = dtrace_gethrtime();

      dtrace_interrupt_enable(cookie);
}

/*
 * DTrace Probe Hashing Functions
 *
 * The functions in this section (and indeed, the functions in remaining
 * sections) are not _called_ from probe context.  (Any exceptions to this are
 * marked with a "Note:".)  Rather, they are called from elsewhere in the
 * DTrace framework to look-up probes in, add probes to and remove probes from
 * the DTrace probe hashes.  (Each probe is hashed by each element of the
 * probe tuple -- allowing for fast lookups, regardless of what was
 * specified.)
 */
static uint_t
dtrace_hash_str(const char *p)
{
      unsigned int g;
      uint_t hval = 0;

      while (*p) {
            hval = (hval << 4) + *p++;
            if ((g = (hval & 0xf0000000)) != 0)
                  hval ^= g >> 24;
            hval &= ~g;
      }
      return (hval);
}

static dtrace_hash_t *
dtrace_hash_create(uintptr_t stroffs, uintptr_t nextoffs, uintptr_t prevoffs)
{
      dtrace_hash_t *hash = kmem_zalloc(sizeof (dtrace_hash_t), KM_SLEEP);

      hash->dth_stroffs = stroffs;
      hash->dth_nextoffs = nextoffs;
      hash->dth_prevoffs = prevoffs;

      hash->dth_size = 1;
      hash->dth_mask = hash->dth_size - 1;

      hash->dth_tab = kmem_zalloc(hash->dth_size *
          sizeof (dtrace_hashbucket_t *), KM_SLEEP);

      return (hash);
}

static void
dtrace_hash_destroy(dtrace_hash_t *hash)
{
#ifdef DEBUG
      int i;

      for (i = 0; i < hash->dth_size; i++)
            ASSERT(hash->dth_tab[i] == NULL);
#endif

      kmem_free(hash->dth_tab,
          hash->dth_size * sizeof (dtrace_hashbucket_t *));
      kmem_free(hash, sizeof (dtrace_hash_t));
}

static void
dtrace_hash_resize(dtrace_hash_t *hash)
{
      int size = hash->dth_size, i, ndx;
      int new_size = hash->dth_size << 1;
      int new_mask = new_size - 1;
      dtrace_hashbucket_t **new_tab, *bucket, *next;

      ASSERT((new_size & new_mask) == 0);

      new_tab = kmem_zalloc(new_size * sizeof (void *), KM_SLEEP);

      for (i = 0; i < size; i++) {
            for (bucket = hash->dth_tab[i]; bucket != NULL; bucket = next) {
                  dtrace_probe_t *probe = bucket->dthb_chain;

                  ASSERT(probe != NULL);
                  ndx = DTRACE_HASHSTR(hash, probe) & new_mask;

                  next = bucket->dthb_next;
                  bucket->dthb_next = new_tab[ndx];
                  new_tab[ndx] = bucket;
            }
      }

      kmem_free(hash->dth_tab, hash->dth_size * sizeof (void *));
      hash->dth_tab = new_tab;
      hash->dth_size = new_size;
      hash->dth_mask = new_mask;
}

static void
dtrace_hash_add(dtrace_hash_t *hash, dtrace_probe_t *new)
{
      int hashval = DTRACE_HASHSTR(hash, new);
      int ndx = hashval & hash->dth_mask;
      dtrace_hashbucket_t *bucket = hash->dth_tab[ndx];
      dtrace_probe_t **nextp, **prevp;

      for (; bucket != NULL; bucket = bucket->dthb_next) {
            if (DTRACE_HASHEQ(hash, bucket->dthb_chain, new))
                  goto add;
      }

      if ((hash->dth_nbuckets >> 1) > hash->dth_size) {
            dtrace_hash_resize(hash);
            dtrace_hash_add(hash, new);
            return;
      }

      bucket = kmem_zalloc(sizeof (dtrace_hashbucket_t), KM_SLEEP);
      bucket->dthb_next = hash->dth_tab[ndx];
      hash->dth_tab[ndx] = bucket;
      hash->dth_nbuckets++;

add:
      nextp = DTRACE_HASHNEXT(hash, new);
      ASSERT(*nextp == NULL && *(DTRACE_HASHPREV(hash, new)) == NULL);
      *nextp = bucket->dthb_chain;

      if (bucket->dthb_chain != NULL) {
            prevp = DTRACE_HASHPREV(hash, bucket->dthb_chain);
            ASSERT(*prevp == NULL);
            *prevp = new;
      }

      bucket->dthb_chain = new;
      bucket->dthb_len++;
}

static dtrace_probe_t *
dtrace_hash_lookup(dtrace_hash_t *hash, dtrace_probe_t *template)
{
      int hashval = DTRACE_HASHSTR(hash, template);
      int ndx = hashval & hash->dth_mask;
      dtrace_hashbucket_t *bucket = hash->dth_tab[ndx];

      for (; bucket != NULL; bucket = bucket->dthb_next) {
            if (DTRACE_HASHEQ(hash, bucket->dthb_chain, template))
                  return (bucket->dthb_chain);
      }

      return (NULL);
}

static int
dtrace_hash_collisions(dtrace_hash_t *hash, dtrace_probe_t *template)
{
      int hashval = DTRACE_HASHSTR(hash, template);
      int ndx = hashval & hash->dth_mask;
      dtrace_hashbucket_t *bucket = hash->dth_tab[ndx];

      for (; bucket != NULL; bucket = bucket->dthb_next) {
            if (DTRACE_HASHEQ(hash, bucket->dthb_chain, template))
                  return (bucket->dthb_len);
      }

      return (0);
}

static void
dtrace_hash_remove(dtrace_hash_t *hash, dtrace_probe_t *probe)
{
      int ndx = DTRACE_HASHSTR(hash, probe) & hash->dth_mask;
      dtrace_hashbucket_t *bucket = hash->dth_tab[ndx];

      dtrace_probe_t **prevp = DTRACE_HASHPREV(hash, probe);
      dtrace_probe_t **nextp = DTRACE_HASHNEXT(hash, probe);

      /*
       * Find the bucket that we're removing this probe from.
       */
      for (; bucket != NULL; bucket = bucket->dthb_next) {
            if (DTRACE_HASHEQ(hash, bucket->dthb_chain, probe))
                  break;
      }

      ASSERT(bucket != NULL);

      if (*prevp == NULL) {
            if (*nextp == NULL) {
                  /*
                   * The removed probe was the only probe on this
                   * bucket; we need to remove the bucket.
                   */
                  dtrace_hashbucket_t *b = hash->dth_tab[ndx];

                  ASSERT(bucket->dthb_chain == probe);
                  ASSERT(b != NULL);

                  if (b == bucket) {
                        hash->dth_tab[ndx] = bucket->dthb_next;
                  } else {
                        while (b->dthb_next != bucket)
                              b = b->dthb_next;
                        b->dthb_next = bucket->dthb_next;
                  }

                  ASSERT(hash->dth_nbuckets > 0);
                  hash->dth_nbuckets--;
                  kmem_free(bucket, sizeof (dtrace_hashbucket_t));
                  return;
            }

            bucket->dthb_chain = *nextp;
      } else {
            *(DTRACE_HASHNEXT(hash, *prevp)) = *nextp;
      }

      if (*nextp != NULL)
            *(DTRACE_HASHPREV(hash, *nextp)) = *prevp;
}

/*
 * DTrace Utility Functions
 *
 * These are random utility functions that are _not_ called from probe context.
 */
static int
dtrace_badattr(const dtrace_attribute_t *a)
{
      return (a->dtat_name > DTRACE_STABILITY_MAX ||
          a->dtat_data > DTRACE_STABILITY_MAX ||
          a->dtat_class > DTRACE_CLASS_MAX);
}

/*
 * Return a duplicate copy of a string.  If the specified string is NULL,
 * this function returns a zero-length string.
 */
static char *
dtrace_strdup(const char *str)
{
      char *new = kmem_zalloc((str != NULL ? strlen(str) : 0) + 1, KM_SLEEP);

      if (str != NULL)
            (void) strcpy(new, str);

      return (new);
}

#define     DTRACE_ISALPHA(c) \
      (((c) >= 'a' && (c) <= 'z') || ((c) >= 'A' && (c) <= 'Z'))

static int
dtrace_badname(const char *s)
{
      char c;

      if (s == NULL || (c = *s++) == '\0')
            return (0);

      if (!DTRACE_ISALPHA(c) && c != '-' && c != '_' && c != '.')
            return (1);

      while ((c = *s++) != '\0') {
            if (!DTRACE_ISALPHA(c) && (c < '0' || c > '9') &&
                c != '-' && c != '_' && c != '.' && c != '`')
                  return (1);
      }

      return (0);
}

static void
dtrace_cred2priv(cred_t *cr, uint32_t *privp, uid_t *uidp, zoneid_t *zoneidp)
{
      uint32_t priv;

#if defined(sun)
      if (cr == NULL || PRIV_POLICY_ONLY(cr, PRIV_ALL, B_FALSE)) {
            /*
             * For DTRACE_PRIV_ALL, the uid and zoneid don't matter.
             */
            priv = DTRACE_PRIV_ALL;
      } else {
            *uidp = crgetuid(cr);
            *zoneidp = crgetzoneid(cr);

            priv = 0;
            if (PRIV_POLICY_ONLY(cr, PRIV_DTRACE_KERNEL, B_FALSE))
                  priv |= DTRACE_PRIV_KERNEL | DTRACE_PRIV_USER;
            else if (PRIV_POLICY_ONLY(cr, PRIV_DTRACE_USER, B_FALSE))
                  priv |= DTRACE_PRIV_USER;
            if (PRIV_POLICY_ONLY(cr, PRIV_DTRACE_PROC, B_FALSE))
                  priv |= DTRACE_PRIV_PROC;
            if (PRIV_POLICY_ONLY(cr, PRIV_PROC_OWNER, B_FALSE))
                  priv |= DTRACE_PRIV_OWNER;
            if (PRIV_POLICY_ONLY(cr, PRIV_PROC_ZONE, B_FALSE))
                  priv |= DTRACE_PRIV_ZONEOWNER;
      }
#else
      priv = DTRACE_PRIV_ALL;
#endif

      *privp = priv;
}

#ifdef DTRACE_ERRDEBUG
static void
dtrace_errdebug(const char *str)
{
      int hval = dtrace_hash_str(str) % DTRACE_ERRHASHSZ;
      int occupied = 0;

      mutex_enter(&dtrace_errlock);
      dtrace_errlast = str;
      dtrace_errthread = curthread;

      while (occupied++ < DTRACE_ERRHASHSZ) {
            if (dtrace_errhash[hval].dter_msg == str) {
                  dtrace_errhash[hval].dter_count++;
                  goto out;
            }

            if (dtrace_errhash[hval].dter_msg != NULL) {
                  hval = (hval + 1) % DTRACE_ERRHASHSZ;
                  continue;
            }

            dtrace_errhash[hval].dter_msg = str;
            dtrace_errhash[hval].dter_count = 1;
            goto out;
      }

      panic("dtrace: undersized error hash");
out:
      mutex_exit(&dtrace_errlock);
}
#endif

/*
 * DTrace Matching Functions
 *
 * These functions are used to match groups of probes, given some elements of
 * a probe tuple, or some globbed expressions for elements of a probe tuple.
 */
static int
dtrace_match_priv(const dtrace_probe_t *prp, uint32_t priv, uid_t uid,
    zoneid_t zoneid)
{
      if (priv != DTRACE_PRIV_ALL) {
            uint32_t ppriv = prp->dtpr_provider->dtpv_priv.dtpp_flags;
            uint32_t match = priv & ppriv;

            /*
             * No PRIV_DTRACE_* privileges...
             */
            if ((priv & (DTRACE_PRIV_PROC | DTRACE_PRIV_USER |
                DTRACE_PRIV_KERNEL)) == 0)
                  return (0);

            /*
             * No matching bits, but there were bits to match...
             */
            if (match == 0 && ppriv != 0)
                  return (0);

            /*
             * Need to have permissions to the process, but don't...
             */
            if (((ppriv & ~match) & DTRACE_PRIV_OWNER) != 0 &&
                uid != prp->dtpr_provider->dtpv_priv.dtpp_uid) {
                  return (0);
            }

            /*
             * Need to be in the same zone unless we possess the
             * privilege to examine all zones.
             */
            if (((ppriv & ~match) & DTRACE_PRIV_ZONEOWNER) != 0 &&
                zoneid != prp->dtpr_provider->dtpv_priv.dtpp_zoneid) {
                  return (0);
            }
      }

      return (1);
}

/*
 * dtrace_match_probe compares a dtrace_probe_t to a pre-compiled key, which
 * consists of input pattern strings and an ops-vector to evaluate them.
 * This function returns >0 for match, 0 for no match, and <0 for error.
 */
static int
dtrace_match_probe(const dtrace_probe_t *prp, const dtrace_probekey_t *pkp,
    uint32_t priv, uid_t uid, zoneid_t zoneid)
{
      dtrace_provider_t *pvp = prp->dtpr_provider;
      int rv;

      if (pvp->dtpv_defunct)
            return (0);

      if ((rv = pkp->dtpk_pmatch(pvp->dtpv_name, pkp->dtpk_prov, 0)) <= 0)
            return (rv);

      if ((rv = pkp->dtpk_mmatch(prp->dtpr_mod, pkp->dtpk_mod, 0)) <= 0)
            return (rv);

      if ((rv = pkp->dtpk_fmatch(prp->dtpr_func, pkp->dtpk_func, 0)) <= 0)
            return (rv);

      if ((rv = pkp->dtpk_nmatch(prp->dtpr_name, pkp->dtpk_name, 0)) <= 0)
            return (rv);

      if (dtrace_match_priv(prp, priv, uid, zoneid) == 0)
            return (0);

      return (rv);
}

/*
 * dtrace_match_glob() is a safe kernel implementation of the gmatch(3GEN)
 * interface for matching a glob pattern 'p' to an input string 's'.  Unlike
 * libc's version, the kernel version only applies to 8-bit ASCII strings.
 * In addition, all of the recursion cases except for '*' matching have been
 * unwound.  For '*', we still implement recursive evaluation, but a depth
 * counter is maintained and matching is aborted if we recurse too deep.
 * The function returns 0 if no match, >0 if match, and <0 if recursion error.
 */
static int
dtrace_match_glob(const char *s, const char *p, int depth)
{
      const char *olds;
      char s1, c;
      int gs;

      if (depth > DTRACE_PROBEKEY_MAXDEPTH)
            return (-1);

      if (s == NULL)
            s = ""; /* treat NULL as empty string */

top:
      olds = s;
      s1 = *s++;

      if (p == NULL)
            return (0);

      if ((c = *p++) == '\0')
            return (s1 == '\0');

      switch (c) {
      case '[': {
            int ok = 0, notflag = 0;
            char lc = '\0';

            if (s1 == '\0')
                  return (0);

            if (*p == '!') {
                  notflag = 1;
                  p++;
            }

            if ((c = *p++) == '\0')
                  return (0);

            do {
                  if (c == '-' && lc != '\0' && *p != ']') {
                        if ((c = *p++) == '\0')
                              return (0);
                        if (c == '\\' && (c = *p++) == '\0')
                              return (0);

                        if (notflag) {
                              if (s1 < lc || s1 > c)
                                    ok++;
                              else
                                    return (0);
                        } else if (lc <= s1 && s1 <= c)
                              ok++;

                  } else if (c == '\\' && (c = *p++) == '\0')
                        return (0);

                  lc = c; /* save left-hand 'c' for next iteration */

                  if (notflag) {
                        if (s1 != c)
                              ok++;
                        else
                              return (0);
                  } else if (s1 == c)
                        ok++;

                  if ((c = *p++) == '\0')
                        return (0);

            } while (c != ']');

            if (ok)
                  goto top;

            return (0);
      }

      case '\\':
            if ((c = *p++) == '\0')
                  return (0);
            /*FALLTHRU*/

      default:
            if (c != s1)
                  return (0);
            /*FALLTHRU*/

      case '?':
            if (s1 != '\0')
                  goto top;
            return (0);

      case '*':
            while (*p == '*')
                  p++; /* consecutive *'s are identical to a single one */

            if (*p == '\0')
                  return (1);

            for (s = olds; *s != '\0'; s++) {
                  if ((gs = dtrace_match_glob(s, p, depth + 1)) != 0)
                        return (gs);
            }

            return (0);
      }
}

/*ARGSUSED*/
static int
dtrace_match_string(const char *s, const char *p, int depth)
{
      return (s != NULL && strcmp(s, p) == 0);
}

/*ARGSUSED*/
static int
dtrace_match_nul(const char *s, const char *p, int depth)
{
      return (1); /* always match the empty pattern */
}

/*ARGSUSED*/
static int
dtrace_match_nonzero(const char *s, const char *p, int depth)
{
      return (s != NULL && s[0] != '\0');
}

static int
dtrace_match(const dtrace_probekey_t *pkp, uint32_t priv, uid_t uid,
    zoneid_t zoneid, int (*matched)(dtrace_probe_t *, void *), void *arg)
{
      dtrace_probe_t template, *probe;
      dtrace_hash_t *hash = NULL;
      int len, best = INT_MAX, nmatched = 0;
      dtrace_id_t i;

      ASSERT(MUTEX_HELD(&dtrace_lock));

      /*
       * If the probe ID is specified in the key, just lookup by ID and
       * invoke the match callback once if a matching probe is found.
       */
      if (pkp->dtpk_id != DTRACE_IDNONE) {
            if ((probe = dtrace_probe_lookup_id(pkp->dtpk_id)) != NULL &&
                dtrace_match_probe(probe, pkp, priv, uid, zoneid) > 0) {
                  (void) (*matched)(probe, arg);
                  nmatched++;
            }
            return (nmatched);
      }

      template.dtpr_mod = (char *)pkp->dtpk_mod;
      template.dtpr_func = (char *)pkp->dtpk_func;
      template.dtpr_name = (char *)pkp->dtpk_name;

      /*
       * We want to find the most distinct of the module name, function
       * name, and name.  So for each one that is not a glob pattern or
       * empty string, we perform a lookup in the corresponding hash and
       * use the hash table with the fewest collisions to do our search.
       */
      if (pkp->dtpk_mmatch == &dtrace_match_string &&
          (len = dtrace_hash_collisions(dtrace_bymod, &template)) < best) {
            best = len;
            hash = dtrace_bymod;
      }

      if (pkp->dtpk_fmatch == &dtrace_match_string &&
          (len = dtrace_hash_collisions(dtrace_byfunc, &template)) < best) {
            best = len;
            hash = dtrace_byfunc;
      }

      if (pkp->dtpk_nmatch == &dtrace_match_string &&
          (len = dtrace_hash_collisions(dtrace_byname, &template)) < best) {
            best = len;
            hash = dtrace_byname;
      }

      /*
       * If we did not select a hash table, iterate over every probe and
       * invoke our callback for each one that matches our input probe key.
       */
      if (hash == NULL) {
            for (i = 0; i < dtrace_nprobes; i++) {
                  if ((probe = dtrace_probes[i]) == NULL ||
                      dtrace_match_probe(probe, pkp, priv, uid,
                      zoneid) <= 0)
                        continue;

                  nmatched++;

                  if ((*matched)(probe, arg) != DTRACE_MATCH_NEXT)
                        break;
            }

            return (nmatched);
      }

      /*
       * If we selected a hash table, iterate over each probe of the same key
       * name and invoke the callback for every probe that matches the other
       * attributes of our input probe key.
       */
      for (probe = dtrace_hash_lookup(hash, &template); probe != NULL;
          probe = *(DTRACE_HASHNEXT(hash, probe))) {

            if (dtrace_match_probe(probe, pkp, priv, uid, zoneid) <= 0)
                  continue;

            nmatched++;

            if ((*matched)(probe, arg) != DTRACE_MATCH_NEXT)
                  break;
      }

      return (nmatched);
}

/*
 * Return the function pointer dtrace_probecmp() should use to compare the
 * specified pattern with a string.  For NULL or empty patterns, we select
 * dtrace_match_nul().  For glob pattern strings, we use dtrace_match_glob().
 * For non-empty non-glob strings, we use dtrace_match_string().
 */
static dtrace_probekey_f *
dtrace_probekey_func(const char *p)
{
      char c;

      if (p == NULL || *p == '\0')
            return (&dtrace_match_nul);

      while ((c = *p++) != '\0') {
            if (c == '[' || c == '?' || c == '*' || c == '\\')
                  return (&dtrace_match_glob);
      }

      return (&dtrace_match_string);
}

/*
 * Build a probe comparison key for use with dtrace_match_probe() from the
 * given probe description.  By convention, a null key only matches anchored
 * probes: if each field is the empty string, reset dtpk_fmatch to
 * dtrace_match_nonzero().
 */
static void
dtrace_probekey(dtrace_probedesc_t *pdp, dtrace_probekey_t *pkp)
{
      pkp->dtpk_prov = pdp->dtpd_provider;
      pkp->dtpk_pmatch = dtrace_probekey_func(pdp->dtpd_provider);

      pkp->dtpk_mod = pdp->dtpd_mod;
      pkp->dtpk_mmatch = dtrace_probekey_func(pdp->dtpd_mod);

      pkp->dtpk_func = pdp->dtpd_func;
      pkp->dtpk_fmatch = dtrace_probekey_func(pdp->dtpd_func);

      pkp->dtpk_name = pdp->dtpd_name;
      pkp->dtpk_nmatch = dtrace_probekey_func(pdp->dtpd_name);

      pkp->dtpk_id = pdp->dtpd_id;

      if (pkp->dtpk_id == DTRACE_IDNONE &&
          pkp->dtpk_pmatch == &dtrace_match_nul &&
          pkp->dtpk_mmatch == &dtrace_match_nul &&
          pkp->dtpk_fmatch == &dtrace_match_nul &&
          pkp->dtpk_nmatch == &dtrace_match_nul)
            pkp->dtpk_fmatch = &dtrace_match_nonzero;
}

/*
 * DTrace Provider-to-Framework API Functions
 *
 * These functions implement much of the Provider-to-Framework API, as
 * described in <sys/dtrace.h>.  The parts of the API not in this section are
 * the functions in the API for probe management (found below), and
 * dtrace_probe() itself (found above).
 */

/*
 * Register the calling provider with the DTrace framework.  This should
 * generally be called by DTrace providers in their attach(9E) entry point.
 */
int
dtrace_register(const char *name, const dtrace_pattr_t *pap, uint32_t priv,
    cred_t *cr, const dtrace_pops_t *pops, void *arg, dtrace_provider_id_t *idp)
{
      dtrace_provider_t *provider;

      if (name == NULL || pap == NULL || pops == NULL || idp == NULL) {
            cmn_err(CE_WARN, "failed to register provider '%s': invalid "
                "arguments", name ? name : "<NULL>");
            return (EINVAL);
      }

      if (name[0] == '\0' || dtrace_badname(name)) {
            cmn_err(CE_WARN, "failed to register provider '%s': invalid "
                "provider name", name);
            return (EINVAL);
      }

      if ((pops->dtps_provide == NULL && pops->dtps_provide_module == NULL) ||
          pops->dtps_enable == NULL || pops->dtps_disable == NULL ||
          pops->dtps_destroy == NULL ||
          ((pops->dtps_resume == NULL) != (pops->dtps_suspend == NULL))) {
            cmn_err(CE_WARN, "failed to register provider '%s': invalid "
                "provider ops", name);
            return (EINVAL);
      }

      if (dtrace_badattr(&pap->dtpa_provider) ||
          dtrace_badattr(&pap->dtpa_mod) ||
          dtrace_badattr(&pap->dtpa_func) ||
          dtrace_badattr(&pap->dtpa_name) ||
          dtrace_badattr(&pap->dtpa_args)) {
            cmn_err(CE_WARN, "failed to register provider '%s': invalid "
                "provider attributes", name);
            return (EINVAL);
      }

      if (priv & ~DTRACE_PRIV_ALL) {
            cmn_err(CE_WARN, "failed to register provider '%s': invalid "
                "privilege attributes", name);
            return (EINVAL);
      }

      if ((priv & DTRACE_PRIV_KERNEL) &&
          (priv & (DTRACE_PRIV_USER | DTRACE_PRIV_OWNER)) &&
          pops->dtps_usermode == NULL) {
            cmn_err(CE_WARN, "failed to register provider '%s': need "
                "dtps_usermode() op for given privilege attributes", name);
            return (EINVAL);
      }

      provider = kmem_zalloc(sizeof (dtrace_provider_t), KM_SLEEP);
      provider->dtpv_name = kmem_alloc(strlen(name) + 1, KM_SLEEP);
      (void) strcpy(provider->dtpv_name, name);

      provider->dtpv_attr = *pap;
      provider->dtpv_priv.dtpp_flags = priv;
      if (cr != NULL) {
            provider->dtpv_priv.dtpp_uid = crgetuid(cr);
            provider->dtpv_priv.dtpp_zoneid = crgetzoneid(cr);
      }
      provider->dtpv_pops = *pops;

      if (pops->dtps_provide == NULL) {
            ASSERT(pops->dtps_provide_module != NULL);
            provider->dtpv_pops.dtps_provide =
                (void (*)(void *, dtrace_probedesc_t *))dtrace_nullop;
      }

      if (pops->dtps_provide_module == NULL) {
            ASSERT(pops->dtps_provide != NULL);
            provider->dtpv_pops.dtps_provide_module =
                (void (*)(void *, modctl_t *))dtrace_nullop;
      }

      if (pops->dtps_suspend == NULL) {
            ASSERT(pops->dtps_resume == NULL);
            provider->dtpv_pops.dtps_suspend =
                (void (*)(void *, dtrace_id_t, void *))dtrace_nullop;
            provider->dtpv_pops.dtps_resume =
                (void (*)(void *, dtrace_id_t, void *))dtrace_nullop;
      }

      provider->dtpv_arg = arg;
      *idp = (dtrace_provider_id_t)provider;

      if (pops == &dtrace_provider_ops) {
            ASSERT(MUTEX_HELD(&dtrace_provider_lock));
            ASSERT(MUTEX_HELD(&dtrace_lock));
            ASSERT(dtrace_anon.dta_enabling == NULL);

            /*
             * We make sure that the DTrace provider is at the head of
             * the provider chain.
             */
            provider->dtpv_next = dtrace_provider;
            dtrace_provider = provider;
            return (0);
      }

      mutex_enter(&dtrace_provider_lock);
      mutex_enter(&dtrace_lock);

      /*
       * If there is at least one provider registered, we'll add this
       * provider after the first provider.
       */
      if (dtrace_provider != NULL) {
            provider->dtpv_next = dtrace_provider->dtpv_next;
            dtrace_provider->dtpv_next = provider;
      } else {
            dtrace_provider = provider;
      }

      if (dtrace_retained != NULL) {
            dtrace_enabling_provide(provider);

            /*
             * Now we need to call dtrace_enabling_matchall() -- which
             * will acquire cpu_lock and dtrace_lock.  We therefore need
             * to drop all of our locks before calling into it...
             */
            mutex_exit(&dtrace_lock);
            mutex_exit(&dtrace_provider_lock);
            dtrace_enabling_matchall();

            return (0);
      }

      mutex_exit(&dtrace_lock);
      mutex_exit(&dtrace_provider_lock);

      return (0);
}

/*
 * Unregister the specified provider from the DTrace framework.  This should
 * generally be called by DTrace providers in their detach(9E) entry point.
 */
int
dtrace_unregister(dtrace_provider_id_t id)
{
      dtrace_provider_t *old = (dtrace_provider_t *)id;
      dtrace_provider_t *prev = NULL;
      int i, self = 0;
      dtrace_probe_t *probe, *first = NULL;

      if (old->dtpv_pops.dtps_enable ==
          (void (*)(void *, dtrace_id_t, void *))dtrace_nullop) {
            /*
             * If DTrace itself is the provider, we're called with locks
             * already held.
             */
            ASSERT(old == dtrace_provider);
#if defined(sun)
            ASSERT(dtrace_devi != NULL);
#endif
            ASSERT(MUTEX_HELD(&dtrace_provider_lock));
            ASSERT(MUTEX_HELD(&dtrace_lock));
            self = 1;

            if (dtrace_provider->dtpv_next != NULL) {
                  /*
                   * There's another provider here; return failure.
                   */
                  return (EBUSY);
            }
      } else {
            mutex_enter(&dtrace_provider_lock);
            mutex_enter(&mod_lock);
            mutex_enter(&dtrace_lock);
      }

      /*
       * If anyone has /dev/dtrace open, or if there are anonymous enabled
       * probes, we refuse to let providers slither away, unless this
       * provider has already been explicitly invalidated.
       */
      if (!old->dtpv_defunct &&
          (dtrace_opens || (dtrace_anon.dta_state != NULL &&
          dtrace_anon.dta_state->dts_necbs > 0))) {
            if (!self) {
                  mutex_exit(&dtrace_lock);
                  mutex_exit(&mod_lock);
                  mutex_exit(&dtrace_provider_lock);
            }
            return (EBUSY);
      }

      /*
       * Attempt to destroy the probes associated with this provider.
       */
      for (i = 0; i < dtrace_nprobes; i++) {
            if ((probe = dtrace_probes[i]) == NULL)
                  continue;

            if (probe->dtpr_provider != old)
                  continue;

            if (probe->dtpr_ecb == NULL)
                  continue;

            /*
             * We have at least one ECB; we can't remove this provider.
             */
            if (!self) {
                  mutex_exit(&dtrace_lock);
                  mutex_exit(&mod_lock);
                  mutex_exit(&dtrace_provider_lock);
            }
            return (EBUSY);
      }

      /*
       * All of the probes for this provider are disabled; we can safely
       * remove all of them from their hash chains and from the probe array.
       */
      for (i = 0; i < dtrace_nprobes; i++) {
            if ((probe = dtrace_probes[i]) == NULL)
                  continue;

            if (probe->dtpr_provider != old)
                  continue;

            dtrace_probes[i] = NULL;

            dtrace_hash_remove(dtrace_bymod, probe);
            dtrace_hash_remove(dtrace_byfunc, probe);
            dtrace_hash_remove(dtrace_byname, probe);

            if (first == NULL) {
                  first = probe;
                  probe->dtpr_nextmod = NULL;
            } else {
                  probe->dtpr_nextmod = first;
                  first = probe;
            }
      }

      /*
       * The provider's probes have been removed from the hash chains and
       * from the probe array.  Now issue a dtrace_sync() to be sure that
       * everyone has cleared out from any probe array processing.
       */
      dtrace_sync();

      for (probe = first; probe != NULL; probe = first) {
            first = probe->dtpr_nextmod;

            old->dtpv_pops.dtps_destroy(old->dtpv_arg, probe->dtpr_id,
                probe->dtpr_arg);
            kmem_free(probe->dtpr_mod, strlen(probe->dtpr_mod) + 1);
            kmem_free(probe->dtpr_func, strlen(probe->dtpr_func) + 1);
            kmem_free(probe->dtpr_name, strlen(probe->dtpr_name) + 1);
#if defined(sun)
            vmem_free(dtrace_arena, (void *)(uintptr_t)(probe->dtpr_id), 1);
#else
            free_unr(dtrace_arena, probe->dtpr_id);
#endif
            kmem_free(probe, sizeof (dtrace_probe_t));
      }

      if ((prev = dtrace_provider) == old) {
#if defined(sun)
            ASSERT(self || dtrace_devi == NULL);
            ASSERT(old->dtpv_next == NULL || dtrace_devi == NULL);
#endif
            dtrace_provider = old->dtpv_next;
      } else {
            while (prev != NULL && prev->dtpv_next != old)
                  prev = prev->dtpv_next;

            if (prev == NULL) {
                  panic("attempt to unregister non-existent "
                      "dtrace provider %p\n", (void *)id);
            }

            prev->dtpv_next = old->dtpv_next;
      }

      if (!self) {
            mutex_exit(&dtrace_lock);
            mutex_exit(&mod_lock);
            mutex_exit(&dtrace_provider_lock);
      }

      kmem_free(old->dtpv_name, strlen(old->dtpv_name) + 1);
      kmem_free(old, sizeof (dtrace_provider_t));

      return (0);
}

/*
 * Invalidate the specified provider.  All subsequent probe lookups for the
 * specified provider will fail, but its probes will not be removed.
 */
void
dtrace_invalidate(dtrace_provider_id_t id)
{
      dtrace_provider_t *pvp = (dtrace_provider_t *)id;

      ASSERT(pvp->dtpv_pops.dtps_enable !=
          (void (*)(void *, dtrace_id_t, void *))dtrace_nullop);

      mutex_enter(&dtrace_provider_lock);
      mutex_enter(&dtrace_lock);

      pvp->dtpv_defunct = 1;

      mutex_exit(&dtrace_lock);
      mutex_exit(&dtrace_provider_lock);
}

/*
 * Indicate whether or not DTrace has attached.
 */
int
dtrace_attached(void)
{
      /*
       * dtrace_provider will be non-NULL iff the DTrace driver has
       * attached.  (It's non-NULL because DTrace is always itself a
       * provider.)
       */
      return (dtrace_provider != NULL);
}

/*
 * Remove all the unenabled probes for the given provider.  This function is
 * not unlike dtrace_unregister(), except that it doesn't remove the provider
 * -- just as many of its associated probes as it can.
 */
int
dtrace_condense(dtrace_provider_id_t id)
{
      dtrace_provider_t *prov = (dtrace_provider_t *)id;
      int i;
      dtrace_probe_t *probe;

      /*
       * Make sure this isn't the dtrace provider itself.
       */
      ASSERT(prov->dtpv_pops.dtps_enable !=
          (void (*)(void *, dtrace_id_t, void *))dtrace_nullop);

      mutex_enter(&dtrace_provider_lock);
      mutex_enter(&dtrace_lock);

      /*
       * Attempt to destroy the probes associated with this provider.
       */
      for (i = 0; i < dtrace_nprobes; i++) {
            if ((probe = dtrace_probes[i]) == NULL)
                  continue;

            if (probe->dtpr_provider != prov)
                  continue;

            if (probe->dtpr_ecb != NULL)
                  continue;

            dtrace_probes[i] = NULL;

            dtrace_hash_remove(dtrace_bymod, probe);
            dtrace_hash_remove(dtrace_byfunc, probe);
            dtrace_hash_remove(dtrace_byname, probe);

            prov->dtpv_pops.dtps_destroy(prov->dtpv_arg, i + 1,
                probe->dtpr_arg);
            kmem_free(probe->dtpr_mod, strlen(probe->dtpr_mod) + 1);
            kmem_free(probe->dtpr_func, strlen(probe->dtpr_func) + 1);
            kmem_free(probe->dtpr_name, strlen(probe->dtpr_name) + 1);
            kmem_free(probe, sizeof (dtrace_probe_t));
#if defined(sun)
            vmem_free(dtrace_arena, (void *)((uintptr_t)i + 1), 1);
#else
            free_unr(dtrace_arena, i + 1);
#endif
      }

      mutex_exit(&dtrace_lock);
      mutex_exit(&dtrace_provider_lock);

      return (0);
}

/*
 * DTrace Probe Management Functions
 *
 * The functions in this section perform the DTrace probe management,
 * including functions to create probes, look-up probes, and call into the
 * providers to request that probes be provided.  Some of these functions are
 * in the Provider-to-Framework API; these functions can be identified by the
 * fact that they are not declared "static".
 */

/*
 * Create a probe with the specified module name, function name, and name.
 */
dtrace_id_t
dtrace_probe_create(dtrace_provider_id_t prov, const char *mod,
    const char *func, const char *name, int aframes, void *arg)
{
      dtrace_probe_t *probe, **probes;
      dtrace_provider_t *provider = (dtrace_provider_t *)prov;
      dtrace_id_t id;

      if (provider == dtrace_provider) {
            ASSERT(MUTEX_HELD(&dtrace_lock));
      } else {
            mutex_enter(&dtrace_lock);
      }

#if defined(sun)
      id = (dtrace_id_t)(uintptr_t)vmem_alloc(dtrace_arena, 1,
          VM_BESTFIT | VM_SLEEP);
#else
      id = alloc_unr(dtrace_arena);
#endif
      probe = kmem_zalloc(sizeof (dtrace_probe_t), KM_SLEEP);

      probe->dtpr_id = id;
      probe->dtpr_gen = dtrace_probegen++;
      probe->dtpr_mod = dtrace_strdup(mod);
      probe->dtpr_func = dtrace_strdup(func);
      probe->dtpr_name = dtrace_strdup(name);
      probe->dtpr_arg = arg;
      probe->dtpr_aframes = aframes;
      probe->dtpr_provider = provider;

      dtrace_hash_add(dtrace_bymod, probe);
      dtrace_hash_add(dtrace_byfunc, probe);
      dtrace_hash_add(dtrace_byname, probe);

      if (id - 1 >= dtrace_nprobes) {
            size_t osize = dtrace_nprobes * sizeof (dtrace_probe_t *);
            size_t nsize = osize << 1;

            if (nsize == 0) {
                  ASSERT(osize == 0);
                  ASSERT(dtrace_probes == NULL);
                  nsize = sizeof (dtrace_probe_t *);
            }

            probes = kmem_zalloc(nsize, KM_SLEEP);

            if (dtrace_probes == NULL) {
                  ASSERT(osize == 0);
                  dtrace_probes = probes;
                  dtrace_nprobes = 1;
            } else {
                  dtrace_probe_t **oprobes = dtrace_probes;

                  bcopy(oprobes, probes, osize);
                  dtrace_membar_producer();
                  dtrace_probes = probes;

                  dtrace_sync();

                  /*
                   * All CPUs are now seeing the new probes array; we can
                   * safely free the old array.
                   */
                  kmem_free(oprobes, osize);
                  dtrace_nprobes <<= 1;
            }

            ASSERT(id - 1 < dtrace_nprobes);
      }

      ASSERT(dtrace_probes[id - 1] == NULL);
      dtrace_probes[id - 1] = probe;

      if (provider != dtrace_provider)
            mutex_exit(&dtrace_lock);

      return (id);
}

static dtrace_probe_t *
dtrace_probe_lookup_id(dtrace_id_t id)
{
      ASSERT(MUTEX_HELD(&dtrace_lock));

      if (id == 0 || id > dtrace_nprobes)
            return (NULL);

      return (dtrace_probes[id - 1]);
}

static int
dtrace_probe_lookup_match(dtrace_probe_t *probe, void *arg)
{
      *((dtrace_id_t *)arg) = probe->dtpr_id;

      return (DTRACE_MATCH_DONE);
}

/*
 * Look up a probe based on provider and one or more of module name, function
 * name and probe name.
 */
dtrace_id_t
dtrace_probe_lookup(dtrace_provider_id_t prid, char *mod,
    char *func, char *name)
{
      dtrace_probekey_t pkey;
      dtrace_id_t id;
      int match;

      pkey.dtpk_prov = ((dtrace_provider_t *)prid)->dtpv_name;
      pkey.dtpk_pmatch = &dtrace_match_string;
      pkey.dtpk_mod = mod;
      pkey.dtpk_mmatch = mod ? &dtrace_match_string : &dtrace_match_nul;
      pkey.dtpk_func = func;
      pkey.dtpk_fmatch = func ? &dtrace_match_string : &dtrace_match_nul;
      pkey.dtpk_name = name;
      pkey.dtpk_nmatch = name ? &dtrace_match_string : &dtrace_match_nul;
      pkey.dtpk_id = DTRACE_IDNONE;

      mutex_enter(&dtrace_lock);
      match = dtrace_match(&pkey, DTRACE_PRIV_ALL, 0, 0,
          dtrace_probe_lookup_match, &id);
      mutex_exit(&dtrace_lock);

      ASSERT(match == 1 || match == 0);
      return (match ? id : 0);
}

/*
 * Returns the probe argument associated with the specified probe.
 */
void *
dtrace_probe_arg(dtrace_provider_id_t id, dtrace_id_t pid)
{
      dtrace_probe_t *probe;
      void *rval = NULL;

      mutex_enter(&dtrace_lock);

      if ((probe = dtrace_probe_lookup_id(pid)) != NULL &&
          probe->dtpr_provider == (dtrace_provider_t *)id)
            rval = probe->dtpr_arg;

      mutex_exit(&dtrace_lock);

      return (rval);
}

/*
 * Copy a probe into a probe description.
 */
static void
dtrace_probe_description(const dtrace_probe_t *prp, dtrace_probedesc_t *pdp)
{
      bzero(pdp, sizeof (dtrace_probedesc_t));
      pdp->dtpd_id = prp->dtpr_id;

      (void) strncpy(pdp->dtpd_provider,
          prp->dtpr_provider->dtpv_name, DTRACE_PROVNAMELEN - 1);

      (void) strncpy(pdp->dtpd_mod, prp->dtpr_mod, DTRACE_MODNAMELEN - 1);
      (void) strncpy(pdp->dtpd_func, prp->dtpr_func, DTRACE_FUNCNAMELEN - 1);
      (void) strncpy(pdp->dtpd_name, prp->dtpr_name, DTRACE_NAMELEN - 1);
}

#if !defined(sun)
static int
dtrace_probe_provide_cb(linker_file_t lf, void *arg)
{
      dtrace_provider_t *prv = (dtrace_provider_t *) arg;

      prv->dtpv_pops.dtps_provide_module(prv->dtpv_arg, lf);

      return(0);
}
#endif


/*
 * Called to indicate that a probe -- or probes -- should be provided by a
 * specfied provider.  If the specified description is NULL, the provider will
 * be told to provide all of its probes.  (This is done whenever a new
 * consumer comes along, or whenever a retained enabling is to be matched.) If
 * the specified description is non-NULL, the provider is given the
 * opportunity to dynamically provide the specified probe, allowing providers
 * to support the creation of probes on-the-fly.  (So-called _autocreated_
 * probes.)  If the provider is NULL, the operations will be applied to all
 * providers; if the provider is non-NULL the operations will only be applied
 * to the specified provider.  The dtrace_provider_lock must be held, and the
 * dtrace_lock must _not_ be held -- the provider's dtps_provide() operation
 * will need to grab the dtrace_lock when it reenters the framework through
 * dtrace_probe_lookup(), dtrace_probe_create(), etc.
 */
static void
dtrace_probe_provide(dtrace_probedesc_t *desc, dtrace_provider_t *prv)
{
#if defined(sun)
      modctl_t *ctl;
#endif
      int all = 0;

      ASSERT(MUTEX_HELD(&dtrace_provider_lock));

      if (prv == NULL) {
            all = 1;
            prv = dtrace_provider;
      }

      do {
            /*
             * First, call the blanket provide operation.
             */
            prv->dtpv_pops.dtps_provide(prv->dtpv_arg, desc);

            /*
             * Now call the per-module provide operation.  We will grab
             * mod_lock to prevent the list from being modified.  Note
             * that this also prevents the mod_busy bits from changing.
             * (mod_busy can only be changed with mod_lock held.)
             */
            mutex_enter(&mod_lock);

#if defined(sun)
            ctl = &modules;
            do {
                  if (ctl->mod_busy || ctl->mod_mp == NULL)
                        continue;

                  prv->dtpv_pops.dtps_provide_module(prv->dtpv_arg, ctl);

            } while ((ctl = ctl->mod_next) != &modules);
#else
            (void) linker_file_foreach(dtrace_probe_provide_cb, prv);
#endif

            mutex_exit(&mod_lock);
      } while (all && (prv = prv->dtpv_next) != NULL);
}

#if defined(sun)
/*
 * Iterate over each probe, and call the Framework-to-Provider API function
 * denoted by offs.
 */
static void
dtrace_probe_foreach(uintptr_t offs)
{
      dtrace_provider_t *prov;
      void (*func)(void *, dtrace_id_t, void *);
      dtrace_probe_t *probe;
      dtrace_icookie_t cookie;
      int i;

      /*
       * We disable interrupts to walk through the probe array.  This is
       * safe -- the dtrace_sync() in dtrace_unregister() assures that we
       * won't see stale data.
       */
      cookie = dtrace_interrupt_disable();

      for (i = 0; i < dtrace_nprobes; i++) {
            if ((probe = dtrace_probes[i]) == NULL)
                  continue;

            if (probe->dtpr_ecb == NULL) {
                  /*
                   * This probe isn't enabled -- don't call the function.
                   */
                  continue;
            }

            prov = probe->dtpr_provider;
            func = *((void(**)(void *, dtrace_id_t, void *))
                ((uintptr_t)&prov->dtpv_pops + offs));

            func(prov->dtpv_arg, i + 1, probe->dtpr_arg);
      }

      dtrace_interrupt_enable(cookie);
}
#endif

static int
dtrace_probe_enable(dtrace_probedesc_t *desc, dtrace_enabling_t *enab)
{
      dtrace_probekey_t pkey;
      uint32_t priv;
      uid_t uid;
      zoneid_t zoneid;

      ASSERT(MUTEX_HELD(&dtrace_lock));
      dtrace_ecb_create_cache = NULL;

      if (desc == NULL) {
            /*
             * If we're passed a NULL description, we're being asked to
             * create an ECB with a NULL probe.
             */
            (void) dtrace_ecb_create_enable(NULL, enab);
            return (0);
      }

      dtrace_probekey(desc, &pkey);
      dtrace_cred2priv(enab->dten_vstate->dtvs_state->dts_cred.dcr_cred,
          &priv, &uid, &zoneid);

      return (dtrace_match(&pkey, priv, uid, zoneid, dtrace_ecb_create_enable,
          enab));
}

/*
 * DTrace Helper Provider Functions
 */
static void
dtrace_dofattr2attr(dtrace_attribute_t *attr, const dof_attr_t dofattr)
{
      attr->dtat_name = DOF_ATTR_NAME(dofattr);
      attr->dtat_data = DOF_ATTR_DATA(dofattr);
      attr->dtat_class = DOF_ATTR_CLASS(dofattr);
}

static void
dtrace_dofprov2hprov(dtrace_helper_provdesc_t *hprov,
    const dof_provider_t *dofprov, char *strtab)
{
      hprov->dthpv_provname = strtab + dofprov->dofpv_name;
      dtrace_dofattr2attr(&hprov->dthpv_pattr.dtpa_provider,
          dofprov->dofpv_provattr);
      dtrace_dofattr2attr(&hprov->dthpv_pattr.dtpa_mod,
          dofprov->dofpv_modattr);
      dtrace_dofattr2attr(&hprov->dthpv_pattr.dtpa_func,
          dofprov->dofpv_funcattr);
      dtrace_dofattr2attr(&hprov->dthpv_pattr.dtpa_name,
          dofprov->dofpv_nameattr);
      dtrace_dofattr2attr(&hprov->dthpv_pattr.dtpa_args,
          dofprov->dofpv_argsattr);
}

static void
dtrace_helper_provide_one(dof_helper_t *dhp, dof_sec_t *sec, pid_t pid)
{
      uintptr_t daddr = (uintptr_t)dhp->dofhp_dof;
      dof_hdr_t *dof = (dof_hdr_t *)daddr;
      dof_sec_t *str_sec, *prb_sec, *arg_sec, *off_sec, *enoff_sec;
      dof_provider_t *provider;
      dof_probe_t *probe;
      uint32_t *off, *enoff;
      uint8_t *arg;
      char *strtab;
      uint_t i, nprobes;
      dtrace_helper_provdesc_t dhpv;
      dtrace_helper_probedesc_t dhpb;
      dtrace_meta_t *meta = dtrace_meta_pid;
      dtrace_mops_t *mops = &meta->dtm_mops;
      void *parg;

      provider = (dof_provider_t *)(uintptr_t)(daddr + sec->dofs_offset);
      str_sec = (dof_sec_t *)(uintptr_t)(daddr + dof->dofh_secoff +
          provider->dofpv_strtab * dof->dofh_secsize);
      prb_sec = (dof_sec_t *)(uintptr_t)(daddr + dof->dofh_secoff +
          provider->dofpv_probes * dof->dofh_secsize);
      arg_sec = (dof_sec_t *)(uintptr_t)(daddr + dof->dofh_secoff +
          provider->dofpv_prargs * dof->dofh_secsize);
      off_sec = (dof_sec_t *)(uintptr_t)(daddr + dof->dofh_secoff +
          provider->dofpv_proffs * dof->dofh_secsize);

      strtab = (char *)(uintptr_t)(daddr + str_sec->dofs_offset);
      off = (uint32_t *)(uintptr_t)(daddr + off_sec->dofs_offset);
      arg = (uint8_t *)(uintptr_t)(daddr + arg_sec->dofs_offset);
      enoff = NULL;

      /*
       * See dtrace_helper_provider_validate().
       */
      if (dof->dofh_ident[DOF_ID_VERSION] != DOF_VERSION_1 &&
          provider->dofpv_prenoffs != DOF_SECT_NONE) {
            enoff_sec = (dof_sec_t *)(uintptr_t)(daddr + dof->dofh_secoff +
                provider->dofpv_prenoffs * dof->dofh_secsize);
            enoff = (uint32_t *)(uintptr_t)(daddr + enoff_sec->dofs_offset);
      }

      nprobes = prb_sec->dofs_size / prb_sec->dofs_entsize;

      /*
       * Create the provider.
       */
      dtrace_dofprov2hprov(&dhpv, provider, strtab);

      if ((parg = mops->dtms_provide_pid(meta->dtm_arg, &dhpv, pid)) == NULL)
            return;

      meta->dtm_count++;

      /*
       * Create the probes.
       */
      for (i = 0; i < nprobes; i++) {
            probe = (dof_probe_t *)(uintptr_t)(daddr +
                prb_sec->dofs_offset + i * prb_sec->dofs_entsize);

            dhpb.dthpb_mod = dhp->dofhp_mod;
            dhpb.dthpb_func = strtab + probe->dofpr_func;
            dhpb.dthpb_name = strtab + probe->dofpr_name;
            dhpb.dthpb_base = probe->dofpr_addr;
            dhpb.dthpb_offs = off + probe->dofpr_offidx;
            dhpb.dthpb_noffs = probe->dofpr_noffs;
            if (enoff != NULL) {
                  dhpb.dthpb_enoffs = enoff + probe->dofpr_enoffidx;
                  dhpb.dthpb_nenoffs = probe->dofpr_nenoffs;
            } else {
                  dhpb.dthpb_enoffs = NULL;
                  dhpb.dthpb_nenoffs = 0;
            }
            dhpb.dthpb_args = arg + probe->dofpr_argidx;
            dhpb.dthpb_nargc = probe->dofpr_nargc;
            dhpb.dthpb_xargc = probe->dofpr_xargc;
            dhpb.dthpb_ntypes = strtab + probe->dofpr_nargv;
            dhpb.dthpb_xtypes = strtab + probe->dofpr_xargv;

            mops->dtms_create_probe(meta->dtm_arg, parg, &dhpb);
      }
}

static void
dtrace_helper_provide(dof_helper_t *dhp, pid_t pid)
{
      uintptr_t daddr = (uintptr_t)dhp->dofhp_dof;
      dof_hdr_t *dof = (dof_hdr_t *)daddr;
      int i;

      ASSERT(MUTEX_HELD(&dtrace_meta_lock));

      for (i = 0; i < dof->dofh_secnum; i++) {
            dof_sec_t *sec = (dof_sec_t *)(uintptr_t)(daddr +
                dof->dofh_secoff + i * dof->dofh_secsize);

            if (sec->dofs_type != DOF_SECT_PROVIDER)
                  continue;

            dtrace_helper_provide_one(dhp, sec, pid);
      }

      /*
       * We may have just created probes, so we must now rematch against
       * any retained enablings.  Note that this call will acquire both
       * cpu_lock and dtrace_lock; the fact that we are holding
       * dtrace_meta_lock now is what defines the ordering with respect to
       * these three locks.
       */
      dtrace_enabling_matchall();
}

#if defined(sun)
static void
dtrace_helper_provider_remove_one(dof_helper_t *dhp, dof_sec_t *sec, pid_t pid)
{
      uintptr_t daddr = (uintptr_t)dhp->dofhp_dof;
      dof_hdr_t *dof = (dof_hdr_t *)daddr;
      dof_sec_t *str_sec;
      dof_provider_t *provider;
      char *strtab;
      dtrace_helper_provdesc_t dhpv;
      dtrace_meta_t *meta = dtrace_meta_pid;
      dtrace_mops_t *mops = &meta->dtm_mops;

      provider = (dof_provider_t *)(uintptr_t)(daddr + sec->dofs_offset);
      str_sec = (dof_sec_t *)(uintptr_t)(daddr + dof->dofh_secoff +
          provider->dofpv_strtab * dof->dofh_secsize);

      strtab = (char *)(uintptr_t)(daddr + str_sec->dofs_offset);

      /*
       * Create the provider.
       */
      dtrace_dofprov2hprov(&dhpv, provider, strtab);

      mops->dtms_remove_pid(meta->dtm_arg, &dhpv, pid);

      meta->dtm_count--;
}

static void
dtrace_helper_provider_remove(dof_helper_t *dhp, pid_t pid)
{
      uintptr_t daddr = (uintptr_t)dhp->dofhp_dof;
      dof_hdr_t *dof = (dof_hdr_t *)daddr;
      int i;

      ASSERT(MUTEX_HELD(&dtrace_meta_lock));

      for (i = 0; i < dof->dofh_secnum; i++) {
            dof_sec_t *sec = (dof_sec_t *)(uintptr_t)(daddr +
                dof->dofh_secoff + i * dof->dofh_secsize);

            if (sec->dofs_type != DOF_SECT_PROVIDER)
                  continue;

            dtrace_helper_provider_remove_one(dhp, sec, pid);
      }
}
#endif

/*
 * DTrace Meta Provider-to-Framework API Functions
 *
 * These functions implement the Meta Provider-to-Framework API, as described
 * in <sys/dtrace.h>.
 */
int
dtrace_meta_register(const char *name, const dtrace_mops_t *mops, void *arg,
    dtrace_meta_provider_id_t *idp)
{
      dtrace_meta_t *meta;
      dtrace_helpers_t *help, *next;
      int i;

      *idp = DTRACE_METAPROVNONE;

      /*
       * We strictly don't need the name, but we hold onto it for
       * debuggability. All hail error queues!
       */
      if (name == NULL) {
            cmn_err(CE_WARN, "failed to register meta-provider: "
                "invalid name");
            return (EINVAL);
      }

      if (mops == NULL ||
          mops->dtms_create_probe == NULL ||
          mops->dtms_provide_pid == NULL ||
          mops->dtms_remove_pid == NULL) {
            cmn_err(CE_WARN, "failed to register meta-register %s: "
                "invalid ops", name);
            return (EINVAL);
      }

      meta = kmem_zalloc(sizeof (dtrace_meta_t), KM_SLEEP);
      meta->dtm_mops = *mops;
      meta->dtm_name = kmem_alloc(strlen(name) + 1, KM_SLEEP);
      (void) strcpy(meta->dtm_name, name);
      meta->dtm_arg = arg;

      mutex_enter(&dtrace_meta_lock);
      mutex_enter(&dtrace_lock);

      if (dtrace_meta_pid != NULL) {
            mutex_exit(&dtrace_lock);
            mutex_exit(&dtrace_meta_lock);
            cmn_err(CE_WARN, "failed to register meta-register %s: "
                "user-land meta-provider exists", name);
            kmem_free(meta->dtm_name, strlen(meta->dtm_name) + 1);
            kmem_free(meta, sizeof (dtrace_meta_t));
            return (EINVAL);
      }

      dtrace_meta_pid = meta;
      *idp = (dtrace_meta_provider_id_t)meta;

      /*
       * If there are providers and probes ready to go, pass them
       * off to the new meta provider now.
       */

      help = dtrace_deferred_pid;
      dtrace_deferred_pid = NULL;

      mutex_exit(&dtrace_lock);

      while (help != NULL) {
            for (i = 0; i < help->dthps_nprovs; i++) {
                  dtrace_helper_provide(&help->dthps_provs[i]->dthp_prov,
                      help->dthps_pid);
            }

            next = help->dthps_next;
            help->dthps_next = NULL;
            help->dthps_prev = NULL;
            help->dthps_deferred = 0;
            help = next;
      }

      mutex_exit(&dtrace_meta_lock);

      return (0);
}

int
dtrace_meta_unregister(dtrace_meta_provider_id_t id)
{
      dtrace_meta_t **pp, *old = (dtrace_meta_t *)id;

      mutex_enter(&dtrace_meta_lock);
      mutex_enter(&dtrace_lock);

      if (old == dtrace_meta_pid) {
            pp = &dtrace_meta_pid;
      } else {
            panic("attempt to unregister non-existent "
                "dtrace meta-provider %p\n", (void *)old);
      }

      if (old->dtm_count != 0) {
            mutex_exit(&dtrace_lock);
            mutex_exit(&dtrace_meta_lock);
            return (EBUSY);
      }

      *pp = NULL;

      mutex_exit(&dtrace_lock);
      mutex_exit(&dtrace_meta_lock);

      kmem_free(old->dtm_name, strlen(old->dtm_name) + 1);
      kmem_free(old, sizeof (dtrace_meta_t));

      return (0);
}


/*
 * DTrace DIF Object Functions
 */
static int
dtrace_difo_err(uint_t pc, const char *format, ...)
{
      if (dtrace_err_verbose) {
            va_list alist;

            (void) uprintf("dtrace DIF object error: [%u]: ", pc);
            va_start(alist, format);
            (void) vuprintf(format, alist);
            va_end(alist);
      }

#ifdef DTRACE_ERRDEBUG
      dtrace_errdebug(format);
#endif
      return (1);
}

/*
 * Validate a DTrace DIF object by checking the IR instructions.  The following
 * rules are currently enforced by dtrace_difo_validate():
 *
 * 1. Each instruction must have a valid opcode
 * 2. Each register, string, variable, or subroutine reference must be valid
 * 3. No instruction can modify register %r0 (must be zero)
 * 4. All instruction reserved bits must be set to zero
 * 5. The last instruction must be a "ret" instruction
 * 6. All branch targets must reference a valid instruction _after_ the branch
 */
static int
dtrace_difo_validate(dtrace_difo_t *dp, dtrace_vstate_t *vstate, uint_t nregs,
    cred_t *cr)
{
      int err = 0, i;
      int (*efunc)(uint_t pc, const char *, ...) = dtrace_difo_err;
      int kcheckload;
      uint_t pc;

      kcheckload = cr == NULL ||
          (vstate->dtvs_state->dts_cred.dcr_visible & DTRACE_CRV_KERNEL) == 0;

      dp->dtdo_destructive = 0;

      for (pc = 0; pc < dp->dtdo_len && err == 0; pc++) {
            dif_instr_t instr = dp->dtdo_buf[pc];

            uint_t r1 = DIF_INSTR_R1(instr);
            uint_t r2 = DIF_INSTR_R2(instr);
            uint_t rd = DIF_INSTR_RD(instr);
            uint_t rs = DIF_INSTR_RS(instr);
            uint_t label = DIF_INSTR_LABEL(instr);
            uint_t v = DIF_INSTR_VAR(instr);
            uint_t subr = DIF_INSTR_SUBR(instr);
            uint_t type = DIF_INSTR_TYPE(instr);
            uint_t op = DIF_INSTR_OP(instr);

            switch (op) {
            case DIF_OP_OR:
            case DIF_OP_XOR:
            case DIF_OP_AND:
            case DIF_OP_SLL:
            case DIF_OP_SRL:
            case DIF_OP_SRA:
            case DIF_OP_SUB:
            case DIF_OP_ADD:
            case DIF_OP_MUL:
            case DIF_OP_SDIV:
            case DIF_OP_UDIV:
            case DIF_OP_SREM:
            case DIF_OP_UREM:
            case DIF_OP_COPYS:
                  if (r1 >= nregs)
                        err += efunc(pc, "invalid register %u\n", r1);
                  if (r2 >= nregs)
                        err += efunc(pc, "invalid register %u\n", r2);
                  if (rd >= nregs)
                        err += efunc(pc, "invalid register %u\n", rd);
                  if (rd == 0)
                        err += efunc(pc, "cannot write to %r0\n");
                  break;
            case DIF_OP_NOT:
            case DIF_OP_MOV:
            case DIF_OP_ALLOCS:
                  if (r1 >= nregs)
                        err += efunc(pc, "invalid register %u\n", r1);
                  if (r2 != 0)
                        err += efunc(pc, "non-zero reserved bits\n");
                  if (rd >= nregs)
                        err += efunc(pc, "invalid register %u\n", rd);
                  if (rd == 0)
                        err += efunc(pc, "cannot write to %r0\n");
                  break;
            case DIF_OP_LDSB:
            case DIF_OP_LDSH:
            case DIF_OP_LDSW:
            case DIF_OP_LDUB:
            case DIF_OP_LDUH:
            case DIF_OP_LDUW:
            case DIF_OP_LDX:
                  if (r1 >= nregs)
                        err += efunc(pc, "invalid register %u\n", r1);
                  if (r2 != 0)
                        err += efunc(pc, "non-zero reserved bits\n");
                  if (rd >= nregs)
                        err += efunc(pc, "invalid register %u\n", rd);
                  if (rd == 0)
                        err += efunc(pc, "cannot write to %r0\n");
                  if (kcheckload)
                        dp->dtdo_buf[pc] = DIF_INSTR_LOAD(op +
                            DIF_OP_RLDSB - DIF_OP_LDSB, r1, rd);
                  break;
            case DIF_OP_RLDSB:
            case DIF_OP_RLDSH:
            case DIF_OP_RLDSW:
            case DIF_OP_RLDUB:
            case DIF_OP_RLDUH:
            case DIF_OP_RLDUW:
            case DIF_OP_RLDX:
                  if (r1 >= nregs)
                        err += efunc(pc, "invalid register %u\n", r1);
                  if (r2 != 0)
                        err += efunc(pc, "non-zero reserved bits\n");
                  if (rd >= nregs)
                        err += efunc(pc, "invalid register %u\n", rd);
                  if (rd == 0)
                        err += efunc(pc, "cannot write to %r0\n");
                  break;
            case DIF_OP_ULDSB:
            case DIF_OP_ULDSH:
            case DIF_OP_ULDSW:
            case DIF_OP_ULDUB:
            case DIF_OP_ULDUH:
            case DIF_OP_ULDUW:
            case DIF_OP_ULDX:
                  if (r1 >= nregs)
                        err += efunc(pc, "invalid register %u\n", r1);
                  if (r2 != 0)
                        err += efunc(pc, "non-zero reserved bits\n");
                  if (rd >= nregs)
                        err += efunc(pc, "invalid register %u\n", rd);
                  if (rd == 0)
                        err += efunc(pc, "cannot write to %r0\n");
                  break;
            case DIF_OP_STB:
            case DIF_OP_STH:
            case DIF_OP_STW:
            case DIF_OP_STX:
                  if (r1 >= nregs)
                        err += efunc(pc, "invalid register %u\n", r1);
                  if (r2 != 0)
                        err += efunc(pc, "non-zero reserved bits\n");
                  if (rd >= nregs)
                        err += efunc(pc, "invalid register %u\n", rd);
                  if (rd == 0)
                        err += efunc(pc, "cannot write to 0 address\n");
                  break;
            case DIF_OP_CMP:
            case DIF_OP_SCMP:
                  if (r1 >= nregs)
                        err += efunc(pc, "invalid register %u\n", r1);
                  if (r2 >= nregs)
                        err += efunc(pc, "invalid register %u\n", r2);
                  if (rd != 0)
                        err += efunc(pc, "non-zero reserved bits\n");
                  break;
            case DIF_OP_TST:
                  if (r1 >= nregs)
                        err += efunc(pc, "invalid register %u\n", r1);
                  if (r2 != 0 || rd != 0)
                        err += efunc(pc, "non-zero reserved bits\n");
                  break;
            case DIF_OP_BA:
            case DIF_OP_BE:
            case DIF_OP_BNE:
            case DIF_OP_BG:
            case DIF_OP_BGU:
            case DIF_OP_BGE:
            case DIF_OP_BGEU:
            case DIF_OP_BL:
            case DIF_OP_BLU:
            case DIF_OP_BLE:
            case DIF_OP_BLEU:
                  if (label >= dp->dtdo_len) {
                        err += efunc(pc, "invalid branch target %u\n",
                            label);
                  }
                  if (label <= pc) {
                        err += efunc(pc, "backward branch to %u\n",
                            label);
                  }
                  break;
            case DIF_OP_RET:
                  if (r1 != 0 || r2 != 0)
                        err += efunc(pc, "non-zero reserved bits\n");
                  if (rd >= nregs)
                        err += efunc(pc, "invalid register %u\n", rd);
                  break;
            case DIF_OP_NOP:
            case DIF_OP_POPTS:
            case DIF_OP_FLUSHTS:
                  if (r1 != 0 || r2 != 0 || rd != 0)
                        err += efunc(pc, "non-zero reserved bits\n");
                  break;
            case DIF_OP_SETX:
                  if (DIF_INSTR_INTEGER(instr) >= dp->dtdo_intlen) {
                        err += efunc(pc, "invalid integer ref %u\n",
                            DIF_INSTR_INTEGER(instr));
                  }
                  if (rd >= nregs)
                        err += efunc(pc, "invalid register %u\n", rd);
                  if (rd == 0)
                        err += efunc(pc, "cannot write to %r0\n");
                  break;
            case DIF_OP_SETS:
                  if (DIF_INSTR_STRING(instr) >= dp->dtdo_strlen) {
                        err += efunc(pc, "invalid string ref %u\n",
                            DIF_INSTR_STRING(instr));
                  }
                  if (rd >= nregs)
                        err += efunc(pc, "invalid register %u\n", rd);
                  if (rd == 0)
                        err += efunc(pc, "cannot write to %r0\n");
                  break;
            case DIF_OP_LDGA:
            case DIF_OP_LDTA:
                  if (r1 > DIF_VAR_ARRAY_MAX)
                        err += efunc(pc, "invalid array %u\n", r1);
                  if (r2 >= nregs)
                        err += efunc(pc, "invalid register %u\n", r2);
                  if (rd >= nregs)
                        err += efunc(pc, "invalid register %u\n", rd);
                  if (rd == 0)
                        err += efunc(pc, "cannot write to %r0\n");
                  break;
            case DIF_OP_LDGS:
            case DIF_OP_LDTS:
            case DIF_OP_LDLS:
            case DIF_OP_LDGAA:
            case DIF_OP_LDTAA:
                  if (v < DIF_VAR_OTHER_MIN || v > DIF_VAR_OTHER_MAX)
                        err += efunc(pc, "invalid variable %u\n", v);
                  if (rd >= nregs)
                        err += efunc(pc, "invalid register %u\n", rd);
                  if (rd == 0)
                        err += efunc(pc, "cannot write to %r0\n");
                  break;
            case DIF_OP_STGS:
            case DIF_OP_STTS:
            case DIF_OP_STLS:
            case DIF_OP_STGAA:
            case DIF_OP_STTAA:
                  if (v < DIF_VAR_OTHER_UBASE || v > DIF_VAR_OTHER_MAX)
                        err += efunc(pc, "invalid variable %u\n", v);
                  if (rs >= nregs)
                        err += efunc(pc, "invalid register %u\n", rd);
                  break;
            case DIF_OP_CALL:
                  if (subr > DIF_SUBR_MAX)
                        err += efunc(pc, "invalid subr %u\n", subr);
                  if (rd >= nregs)
                        err += efunc(pc, "invalid register %u\n", rd);
                  if (rd == 0)
                        err += efunc(pc, "cannot write to %r0\n");

                  if (subr == DIF_SUBR_COPYOUT ||
                      subr == DIF_SUBR_COPYOUTSTR) {
                        dp->dtdo_destructive = 1;
                  }
                  break;
            case DIF_OP_PUSHTR:
                  if (type != DIF_TYPE_STRING && type != DIF_TYPE_CTF)
                        err += efunc(pc, "invalid ref type %u\n", type);
                  if (r2 >= nregs)
                        err += efunc(pc, "invalid register %u\n", r2);
                  if (rs >= nregs)
                        err += efunc(pc, "invalid register %u\n", rs);
                  break;
            case DIF_OP_PUSHTV:
                  if (type != DIF_TYPE_CTF)
                        err += efunc(pc, "invalid val type %u\n", type);
                  if (r2 >= nregs)
                        err += efunc(pc, "invalid register %u\n", r2);
                  if (rs >= nregs)
                        err += efunc(pc, "invalid register %u\n", rs);
                  break;
            default:
                  err += efunc(pc, "invalid opcode %u\n",
                      DIF_INSTR_OP(instr));
            }
      }

      if (dp->dtdo_len != 0 &&
          DIF_INSTR_OP(dp->dtdo_buf[dp->dtdo_len - 1]) != DIF_OP_RET) {
            err += efunc(dp->dtdo_len - 1,
                "expected 'ret' as last DIF instruction\n");
      }

      if (!(dp->dtdo_rtype.dtdt_flags & DIF_TF_BYREF)) {
            /*
             * If we're not returning by reference, the size must be either
             * 0 or the size of one of the base types.
             */
            switch (dp->dtdo_rtype.dtdt_size) {
            case 0:
            case sizeof (uint8_t):
            case sizeof (uint16_t):
            case sizeof (uint32_t):
            case sizeof (uint64_t):
                  break;

            default:
                  err += efunc(dp->dtdo_len - 1, "bad return size");
            }
      }

      for (i = 0; i < dp->dtdo_varlen && err == 0; i++) {
            dtrace_difv_t *v = &dp->dtdo_vartab[i], *existing = NULL;
            dtrace_diftype_t *vt, *et;
            uint_t id, ndx;

            if (v->dtdv_scope != DIFV_SCOPE_GLOBAL &&
                v->dtdv_scope != DIFV_SCOPE_THREAD &&
                v->dtdv_scope != DIFV_SCOPE_LOCAL) {
                  err += efunc(i, "unrecognized variable scope %d\n",
                      v->dtdv_scope);
                  break;
            }

            if (v->dtdv_kind != DIFV_KIND_ARRAY &&
                v->dtdv_kind != DIFV_KIND_SCALAR) {
                  err += efunc(i, "unrecognized variable type %d\n",
                      v->dtdv_kind);
                  break;
            }

            if ((id = v->dtdv_id) > DIF_VARIABLE_MAX) {
                  err += efunc(i, "%d exceeds variable id limit\n", id);
                  break;
            }

            if (id < DIF_VAR_OTHER_UBASE)
                  continue;

            /*
             * For user-defined variables, we need to check that this
             * definition is identical to any previous definition that we
             * encountered.
             */
            ndx = id - DIF_VAR_OTHER_UBASE;

            switch (v->dtdv_scope) {
            case DIFV_SCOPE_GLOBAL:
                  if (ndx < vstate->dtvs_nglobals) {
                        dtrace_statvar_t *svar;

                        if ((svar = vstate->dtvs_globals[ndx]) != NULL)
                              existing = &svar->dtsv_var;
                  }

                  break;

            case DIFV_SCOPE_THREAD:
                  if (ndx < vstate->dtvs_ntlocals)
                        existing = &vstate->dtvs_tlocals[ndx];
                  break;

            case DIFV_SCOPE_LOCAL:
                  if (ndx < vstate->dtvs_nlocals) {
                        dtrace_statvar_t *svar;

                        if ((svar = vstate->dtvs_locals[ndx]) != NULL)
                              existing = &svar->dtsv_var;
                  }

                  break;
            }

            vt = &v->dtdv_type;

            if (vt->dtdt_flags & DIF_TF_BYREF) {
                  if (vt->dtdt_size == 0) {
                        err += efunc(i, "zero-sized variable\n");
                        break;
                  }

                  if (v->dtdv_scope == DIFV_SCOPE_GLOBAL &&
                      vt->dtdt_size > dtrace_global_maxsize) {
                        err += efunc(i, "oversized by-ref global\n");
                        break;
                  }
            }

            if (existing == NULL || existing->dtdv_id == 0)
                  continue;

            ASSERT(existing->dtdv_id == v->dtdv_id);
            ASSERT(existing->dtdv_scope == v->dtdv_scope);

            if (existing->dtdv_kind != v->dtdv_kind)
                  err += efunc(i, "%d changed variable kind\n", id);

            et = &existing->dtdv_type;

            if (vt->dtdt_flags != et->dtdt_flags) {
                  err += efunc(i, "%d changed variable type flags\n", id);
                  break;
            }

            if (vt->dtdt_size != 0 && vt->dtdt_size != et->dtdt_size) {
                  err += efunc(i, "%d changed variable type size\n", id);
                  break;
            }
      }

      return (err);
}

#if defined(sun)
/*
 * Validate a DTrace DIF object that it is to be used as a helper.  Helpers
 * are much more constrained than normal DIFOs.  Specifically, they may
 * not:
 *
 * 1. Make calls to subroutines other than copyin(), copyinstr() or
 *    miscellaneous string routines
 * 2. Access DTrace variables other than the args[] array, and the
 *    curthread, pid, ppid, tid, execname, zonename, uid and gid variables.
 * 3. Have thread-local variables.
 * 4. Have dynamic variables.
 */
static int
dtrace_difo_validate_helper(dtrace_difo_t *dp)
{
      int (*efunc)(uint_t pc, const char *, ...) = dtrace_difo_err;
      int err = 0;
      uint_t pc;

      for (pc = 0; pc < dp->dtdo_len; pc++) {
            dif_instr_t instr = dp->dtdo_buf[pc];

            uint_t v = DIF_INSTR_VAR(instr);
            uint_t subr = DIF_INSTR_SUBR(instr);
            uint_t op = DIF_INSTR_OP(instr);

            switch (op) {
            case DIF_OP_OR:
            case DIF_OP_XOR:
            case DIF_OP_AND:
            case DIF_OP_SLL:
            case DIF_OP_SRL:
            case DIF_OP_SRA:
            case DIF_OP_SUB:
            case DIF_OP_ADD:
            case DIF_OP_MUL:
            case DIF_OP_SDIV:
            case DIF_OP_UDIV:
            case DIF_OP_SREM:
            case DIF_OP_UREM:
            case DIF_OP_COPYS:
            case DIF_OP_NOT:
            case DIF_OP_MOV:
            case DIF_OP_RLDSB:
            case DIF_OP_RLDSH:
            case DIF_OP_RLDSW:
            case DIF_OP_RLDUB:
            case DIF_OP_RLDUH:
            case DIF_OP_RLDUW:
            case DIF_OP_RLDX:
            case DIF_OP_ULDSB:
            case DIF_OP_ULDSH:
            case DIF_OP_ULDSW:
            case DIF_OP_ULDUB:
            case DIF_OP_ULDUH:
            case DIF_OP_ULDUW:
            case DIF_OP_ULDX:
            case DIF_OP_STB:
            case DIF_OP_STH:
            case DIF_OP_STW:
            case DIF_OP_STX:
            case DIF_OP_ALLOCS:
            case DIF_OP_CMP:
            case DIF_OP_SCMP:
            case DIF_OP_TST:
            case DIF_OP_BA:
            case DIF_OP_BE:
            case DIF_OP_BNE:
            case DIF_OP_BG:
            case DIF_OP_BGU:
            case DIF_OP_BGE:
            case DIF_OP_BGEU:
            case DIF_OP_BL:
            case DIF_OP_BLU:
            case DIF_OP_BLE:
            case DIF_OP_BLEU:
            case DIF_OP_RET:
            case DIF_OP_NOP:
            case DIF_OP_POPTS:
            case DIF_OP_FLUSHTS:
            case DIF_OP_SETX:
            case DIF_OP_SETS:
            case DIF_OP_LDGA:
            case DIF_OP_LDLS:
            case DIF_OP_STGS:
            case DIF_OP_STLS:
            case DIF_OP_PUSHTR:
            case DIF_OP_PUSHTV:
                  break;

            case DIF_OP_LDGS:
                  if (v >= DIF_VAR_OTHER_UBASE)
                        break;

                  if (v >= DIF_VAR_ARG0 && v <= DIF_VAR_ARG9)
                        break;

                  if (v == DIF_VAR_CURTHREAD || v == DIF_VAR_PID ||
                      v == DIF_VAR_PPID || v == DIF_VAR_TID ||
                      v == DIF_VAR_EXECARGS ||
                      v == DIF_VAR_EXECNAME || v == DIF_VAR_ZONENAME ||
                      v == DIF_VAR_UID || v == DIF_VAR_GID)
                        break;

                  err += efunc(pc, "illegal variable %u\n", v);
                  break;

            case DIF_OP_LDTA:
            case DIF_OP_LDTS:
            case DIF_OP_LDGAA:
            case DIF_OP_LDTAA:
                  err += efunc(pc, "illegal dynamic variable load\n");
                  break;

            case DIF_OP_STTS:
            case DIF_OP_STGAA:
            case DIF_OP_STTAA:
                  err += efunc(pc, "illegal dynamic variable store\n");
                  break;

            case DIF_OP_CALL:
                  if (subr == DIF_SUBR_ALLOCA ||
                      subr == DIF_SUBR_BCOPY ||
                      subr == DIF_SUBR_COPYIN ||
                      subr == DIF_SUBR_COPYINTO ||
                      subr == DIF_SUBR_COPYINSTR ||
                      subr == DIF_SUBR_INDEX ||
                      subr == DIF_SUBR_INET_NTOA ||
                      subr == DIF_SUBR_INET_NTOA6 ||
                      subr == DIF_SUBR_INET_NTOP ||
                      subr == DIF_SUBR_LLTOSTR ||
                      subr == DIF_SUBR_RINDEX ||
                      subr == DIF_SUBR_STRCHR ||
                      subr == DIF_SUBR_STRJOIN ||
                      subr == DIF_SUBR_STRRCHR ||
                      subr == DIF_SUBR_STRSTR ||
                      subr == DIF_SUBR_HTONS ||
                      subr == DIF_SUBR_HTONL ||
                      subr == DIF_SUBR_HTONLL ||
                      subr == DIF_SUBR_NTOHS ||
                      subr == DIF_SUBR_NTOHL ||
                      subr == DIF_SUBR_NTOHLL ||
                      subr == DIF_SUBR_MEMREF ||
                      subr == DIF_SUBR_TYPEREF)
                        break;

                  err += efunc(pc, "invalid subr %u\n", subr);
                  break;

            default:
                  err += efunc(pc, "invalid opcode %u\n",
                      DIF_INSTR_OP(instr));
            }
      }

      return (err);
}
#endif

/*
 * Returns 1 if the expression in the DIF object can be cached on a per-thread
 * basis; 0 if not.
 */
static int
dtrace_difo_cacheable(dtrace_difo_t *dp)
{
      int i;

      if (dp == NULL)
            return (0);

      for (i = 0; i < dp->dtdo_varlen; i++) {
            dtrace_difv_t *v = &dp->dtdo_vartab[i];

            if (v->dtdv_scope != DIFV_SCOPE_GLOBAL)
                  continue;

            switch (v->dtdv_id) {
            case DIF_VAR_CURTHREAD:
            case DIF_VAR_PID:
            case DIF_VAR_TID:
            case DIF_VAR_EXECARGS:
            case DIF_VAR_EXECNAME:
            case DIF_VAR_ZONENAME:
                  break;

            default:
                  return (0);
            }
      }

      /*
       * This DIF object may be cacheable.  Now we need to look for any
       * array loading instructions, any memory loading instructions, or
       * any stores to thread-local variables.
       */
      for (i = 0; i < dp->dtdo_len; i++) {
            uint_t op = DIF_INSTR_OP(dp->dtdo_buf[i]);

            if ((op >= DIF_OP_LDSB && op <= DIF_OP_LDX) ||
                (op >= DIF_OP_ULDSB && op <= DIF_OP_ULDX) ||
                (op >= DIF_OP_RLDSB && op <= DIF_OP_RLDX) ||
                op == DIF_OP_LDGA || op == DIF_OP_STTS)
                  return (0);
      }

      return (1);
}

static void
dtrace_difo_hold(dtrace_difo_t *dp)
{
      int i;

      ASSERT(MUTEX_HELD(&dtrace_lock));

      dp->dtdo_refcnt++;
      ASSERT(dp->dtdo_refcnt != 0);

      /*
       * We need to check this DIF object for references to the variable
       * DIF_VAR_VTIMESTAMP.
       */
      for (i = 0; i < dp->dtdo_varlen; i++) {
            dtrace_difv_t *v = &dp->dtdo_vartab[i];

            if (v->dtdv_id != DIF_VAR_VTIMESTAMP)
                  continue;

            if (dtrace_vtime_references++ == 0)
                  dtrace_vtime_enable();
      }
}

/*
 * This routine calculates the dynamic variable chunksize for a given DIF
 * object.  The calculation is not fool-proof, and can probably be tricked by
 * malicious DIF -- but it works for all compiler-generated DIF.  Because this
 * calculation is likely imperfect, dtrace_dynvar() is able to gracefully fail
 * if a dynamic variable size exceeds the chunksize.
 */
static void
dtrace_difo_chunksize(dtrace_difo_t *dp, dtrace_vstate_t *vstate)
{
      uint64_t sval = 0;
      dtrace_key_t tupregs[DIF_DTR_NREGS + 2]; /* +2 for thread and id */
      const dif_instr_t *text = dp->dtdo_buf;
      uint_t pc, srd = 0;
      uint_t ttop = 0;
      size_t size, ksize;
      uint_t id, i;

      for (pc = 0; pc < dp->dtdo_len; pc++) {
            dif_instr_t instr = text[pc];
            uint_t op = DIF_INSTR_OP(instr);
            uint_t rd = DIF_INSTR_RD(instr);
            uint_t r1 = DIF_INSTR_R1(instr);
            uint_t nkeys = 0;
            uchar_t scope = 0;

            dtrace_key_t *key = tupregs;

            switch (op) {
            case DIF_OP_SETX:
                  sval = dp->dtdo_inttab[DIF_INSTR_INTEGER(instr)];
                  srd = rd;
                  continue;

            case DIF_OP_STTS:
                  key = &tupregs[DIF_DTR_NREGS];
                  key[0].dttk_size = 0;
                  key[1].dttk_size = 0;
                  nkeys = 2;
                  scope = DIFV_SCOPE_THREAD;
                  break;

            case DIF_OP_STGAA:
            case DIF_OP_STTAA:
                  nkeys = ttop;

                  if (DIF_INSTR_OP(instr) == DIF_OP_STTAA)
                        key[nkeys++].dttk_size = 0;

                  key[nkeys++].dttk_size = 0;

                  if (op == DIF_OP_STTAA) {
                        scope = DIFV_SCOPE_THREAD;
                  } else {
                        scope = DIFV_SCOPE_GLOBAL;
                  }

                  break;

            case DIF_OP_PUSHTR:
                  if (ttop == DIF_DTR_NREGS)
                        return;

                  if ((srd == 0 || sval == 0) && r1 == DIF_TYPE_STRING) {
                        /*
                         * If the register for the size of the "pushtr"
                         * is %r0 (or the value is 0) and the type is
                         * a string, we'll use the system-wide default
                         * string size.
                         */
                        tupregs[ttop++].dttk_size =
                            dtrace_strsize_default;
                  } else {
                        if (srd == 0)
                              return;

                        tupregs[ttop++].dttk_size = sval;
                  }

                  break;

            case DIF_OP_PUSHTV:
                  if (ttop == DIF_DTR_NREGS)
                        return;

                  tupregs[ttop++].dttk_size = 0;
                  break;

            case DIF_OP_FLUSHTS:
                  ttop = 0;
                  break;

            case DIF_OP_POPTS:
                  if (ttop != 0)
                        ttop--;
                  break;
            }

            sval = 0;
            srd = 0;

            if (nkeys == 0)
                  continue;

            /*
             * We have a dynamic variable allocation; calculate its size.
             */
            for (ksize = 0, i = 0; i < nkeys; i++)
                  ksize += P2ROUNDUP(key[i].dttk_size, sizeof (uint64_t));

            size = sizeof (dtrace_dynvar_t);
            size += sizeof (dtrace_key_t) * (nkeys - 1);
            size += ksize;

            /*
             * Now we need to determine the size of the stored data.
             */
            id = DIF_INSTR_VAR(instr);

            for (i = 0; i < dp->dtdo_varlen; i++) {
                  dtrace_difv_t *v = &dp->dtdo_vartab[i];

                  if (v->dtdv_id == id && v->dtdv_scope == scope) {
                        size += v->dtdv_type.dtdt_size;
                        break;
                  }
            }

            if (i == dp->dtdo_varlen)
                  return;

            /*
             * We have the size.  If this is larger than the chunk size
             * for our dynamic variable state, reset the chunk size.
             */
            size = P2ROUNDUP(size, sizeof (uint64_t));

            if (size > vstate->dtvs_dynvars.dtds_chunksize)
                  vstate->dtvs_dynvars.dtds_chunksize = size;
      }
}

static void
dtrace_difo_init(dtrace_difo_t *dp, dtrace_vstate_t *vstate)
{
      int i, oldsvars, osz, nsz, otlocals, ntlocals;
      uint_t id;

      ASSERT(MUTEX_HELD(&dtrace_lock));
      ASSERT(dp->dtdo_buf != NULL && dp->dtdo_len != 0);

      for (i = 0; i < dp->dtdo_varlen; i++) {
            dtrace_difv_t *v = &dp->dtdo_vartab[i];
            dtrace_statvar_t *svar, ***svarp = NULL;
            size_t dsize = 0;
            uint8_t scope = v->dtdv_scope;
            int *np = NULL;

            if ((id = v->dtdv_id) < DIF_VAR_OTHER_UBASE)
                  continue;

            id -= DIF_VAR_OTHER_UBASE;

            switch (scope) {
            case DIFV_SCOPE_THREAD:
                  while (id >= (otlocals = vstate->dtvs_ntlocals)) {
                        dtrace_difv_t *tlocals;

                        if ((ntlocals = (otlocals << 1)) == 0)
                              ntlocals = 1;

                        osz = otlocals * sizeof (dtrace_difv_t);
                        nsz = ntlocals * sizeof (dtrace_difv_t);

                        tlocals = kmem_zalloc(nsz, KM_SLEEP);

                        if (osz != 0) {
                              bcopy(vstate->dtvs_tlocals,
                                  tlocals, osz);
                              kmem_free(vstate->dtvs_tlocals, osz);
                        }

                        vstate->dtvs_tlocals = tlocals;
                        vstate->dtvs_ntlocals = ntlocals;
                  }

                  vstate->dtvs_tlocals[id] = *v;
                  continue;

            case DIFV_SCOPE_LOCAL:
                  np = &vstate->dtvs_nlocals;
                  svarp = &vstate->dtvs_locals;

                  if (v->dtdv_type.dtdt_flags & DIF_TF_BYREF)
                        dsize = NCPU * (v->dtdv_type.dtdt_size +
                            sizeof (uint64_t));
                  else
                        dsize = NCPU * sizeof (uint64_t);

                  break;

            case DIFV_SCOPE_GLOBAL:
                  np = &vstate->dtvs_nglobals;
                  svarp = &vstate->dtvs_globals;

                  if (v->dtdv_type.dtdt_flags & DIF_TF_BYREF)
                        dsize = v->dtdv_type.dtdt_size +
                            sizeof (uint64_t);

                  break;

            default:
                  ASSERT(0);
            }

            while (id >= (oldsvars = *np)) {
                  dtrace_statvar_t **statics;
                  int newsvars, oldsize, newsize;

                  if ((newsvars = (oldsvars << 1)) == 0)
                        newsvars = 1;

                  oldsize = oldsvars * sizeof (dtrace_statvar_t *);
                  newsize = newsvars * sizeof (dtrace_statvar_t *);

                  statics = kmem_zalloc(newsize, KM_SLEEP);

                  if (oldsize != 0) {
                        bcopy(*svarp, statics, oldsize);
                        kmem_free(*svarp, oldsize);
                  }

                  *svarp = statics;
                  *np = newsvars;
            }

            if ((svar = (*svarp)[id]) == NULL) {
                  svar = kmem_zalloc(sizeof (dtrace_statvar_t), KM_SLEEP);
                  svar->dtsv_var = *v;

                  if ((svar->dtsv_size = dsize) != 0) {
                        svar->dtsv_data = (uint64_t)(uintptr_t)
                            kmem_zalloc(dsize, KM_SLEEP);
                  }

                  (*svarp)[id] = svar;
            }

            svar->dtsv_refcnt++;
      }

      dtrace_difo_chunksize(dp, vstate);
      dtrace_difo_hold(dp);
}

#if defined(sun)
static dtrace_difo_t *
dtrace_difo_duplicate(dtrace_difo_t *dp, dtrace_vstate_t *vstate)
{
      dtrace_difo_t *new;
      size_t sz;

      ASSERT(dp->dtdo_buf != NULL);
      ASSERT(dp->dtdo_refcnt != 0);

      new = kmem_zalloc(sizeof (dtrace_difo_t), KM_SLEEP);

      ASSERT(dp->dtdo_buf != NULL);
      sz = dp->dtdo_len * sizeof (dif_instr_t);
      new->dtdo_buf = kmem_alloc(sz, KM_SLEEP);
      bcopy(dp->dtdo_buf, new->dtdo_buf, sz);
      new->dtdo_len = dp->dtdo_len;

      if (dp->dtdo_strtab != NULL) {
            ASSERT(dp->dtdo_strlen != 0);
            new->dtdo_strtab = kmem_alloc(dp->dtdo_strlen, KM_SLEEP);
            bcopy(dp->dtdo_strtab, new->dtdo_strtab, dp->dtdo_strlen);
            new->dtdo_strlen = dp->dtdo_strlen;
      }

      if (dp->dtdo_inttab != NULL) {
            ASSERT(dp->dtdo_intlen != 0);
            sz = dp->dtdo_intlen * sizeof (uint64_t);
            new->dtdo_inttab = kmem_alloc(sz, KM_SLEEP);
            bcopy(dp->dtdo_inttab, new->dtdo_inttab, sz);
            new->dtdo_intlen = dp->dtdo_intlen;
      }

      if (dp->dtdo_vartab != NULL) {
            ASSERT(dp->dtdo_varlen != 0);
            sz = dp->dtdo_varlen * sizeof (dtrace_difv_t);
            new->dtdo_vartab = kmem_alloc(sz, KM_SLEEP);
            bcopy(dp->dtdo_vartab, new->dtdo_vartab, sz);
            new->dtdo_varlen = dp->dtdo_varlen;
      }

      dtrace_difo_init(new, vstate);
      return (new);
}
#endif

static void
dtrace_difo_destroy(dtrace_difo_t *dp, dtrace_vstate_t *vstate)
{
      int i;

      ASSERT(dp->dtdo_refcnt == 0);

      for (i = 0; i < dp->dtdo_varlen; i++) {
            dtrace_difv_t *v = &dp->dtdo_vartab[i];
            dtrace_statvar_t *svar, **svarp = NULL;
            uint_t id;
            uint8_t scope = v->dtdv_scope;
            int *np = NULL;

            switch (scope) {
            case DIFV_SCOPE_THREAD:
                  continue;

            case DIFV_SCOPE_LOCAL:
                  np = &vstate->dtvs_nlocals;
                  svarp = vstate->dtvs_locals;
                  break;

            case DIFV_SCOPE_GLOBAL:
                  np = &vstate->dtvs_nglobals;
                  svarp = vstate->dtvs_globals;
                  break;

            default:
                  ASSERT(0);
            }

            if ((id = v->dtdv_id) < DIF_VAR_OTHER_UBASE)
                  continue;

            id -= DIF_VAR_OTHER_UBASE;
            ASSERT(id < *np);

            svar = svarp[id];
            ASSERT(svar != NULL);
            ASSERT(svar->dtsv_refcnt > 0);

            if (--svar->dtsv_refcnt > 0)
                  continue;

            if (svar->dtsv_size != 0) {
                  ASSERT(svar->dtsv_data != 0);
                  kmem_free((void *)(uintptr_t)svar->dtsv_data,
                      svar->dtsv_size);
            }

            kmem_free(svar, sizeof (dtrace_statvar_t));
            svarp[id] = NULL;
      }

      if (dp->dtdo_buf != NULL)
            kmem_free(dp->dtdo_buf, dp->dtdo_len * sizeof (dif_instr_t));
      if (dp->dtdo_inttab != NULL)
            kmem_free(dp->dtdo_inttab, dp->dtdo_intlen * sizeof (uint64_t));
      if (dp->dtdo_strtab != NULL)
            kmem_free(dp->dtdo_strtab, dp->dtdo_strlen);
      if (dp->dtdo_vartab != NULL)
            kmem_free(dp->dtdo_vartab, dp->dtdo_varlen * sizeof (dtrace_difv_t));

      kmem_free(dp, sizeof (dtrace_difo_t));
}

static void
dtrace_difo_release(dtrace_difo_t *dp, dtrace_vstate_t *vstate)
{
      int i;

      ASSERT(MUTEX_HELD(&dtrace_lock));
      ASSERT(dp->dtdo_refcnt != 0);

      for (i = 0; i < dp->dtdo_varlen; i++) {
            dtrace_difv_t *v = &dp->dtdo_vartab[i];

            if (v->dtdv_id != DIF_VAR_VTIMESTAMP)
                  continue;

            ASSERT(dtrace_vtime_references > 0);
            if (--dtrace_vtime_references == 0)
                  dtrace_vtime_disable();
      }

      if (--dp->dtdo_refcnt == 0)
            dtrace_difo_destroy(dp, vstate);
}

/*
 * DTrace Format Functions
 */
static uint16_t
dtrace_format_add(dtrace_state_t *state, char *str)
{
      char *fmt, **new;
      uint16_t ndx, len = strlen(str) + 1;

      fmt = kmem_zalloc(len, KM_SLEEP);
      bcopy(str, fmt, len);

      for (ndx = 0; ndx < state->dts_nformats; ndx++) {
            if (state->dts_formats[ndx] == NULL) {
                  state->dts_formats[ndx] = fmt;
                  return (ndx + 1);
            }
      }

      if (state->dts_nformats == USHRT_MAX) {
            /*
             * This is only likely if a denial-of-service attack is being
             * attempted.  As such, it's okay to fail silently here.
             */
            kmem_free(fmt, len);
            return (0);
      }

      /*
       * For simplicity, we always resize the formats array to be exactly the
       * number of formats.
       */
      ndx = state->dts_nformats++;
      new = kmem_alloc((ndx + 1) * sizeof (char *), KM_SLEEP);

      if (state->dts_formats != NULL) {
            ASSERT(ndx != 0);
            bcopy(state->dts_formats, new, ndx * sizeof (char *));
            kmem_free(state->dts_formats, ndx * sizeof (char *));
      }

      state->dts_formats = new;
      state->dts_formats[ndx] = fmt;

      return (ndx + 1);
}

static void
dtrace_format_remove(dtrace_state_t *state, uint16_t format)
{
      char *fmt;

      ASSERT(state->dts_formats != NULL);
      ASSERT(format <= state->dts_nformats);
      ASSERT(state->dts_formats[format - 1] != NULL);

      fmt = state->dts_formats[format - 1];
      kmem_free(fmt, strlen(fmt) + 1);
      state->dts_formats[format - 1] = NULL;
}

static void
dtrace_format_destroy(dtrace_state_t *state)
{
      int i;

      if (state->dts_nformats == 0) {
            ASSERT(state->dts_formats == NULL);
            return;
      }

      ASSERT(state->dts_formats != NULL);

      for (i = 0; i < state->dts_nformats; i++) {
            char *fmt = state->dts_formats[i];

            if (fmt == NULL)
                  continue;

            kmem_free(fmt, strlen(fmt) + 1);
      }

      kmem_free(state->dts_formats, state->dts_nformats * sizeof (char *));
      state->dts_nformats = 0;
      state->dts_formats = NULL;
}

/*
 * DTrace Predicate Functions
 */
static dtrace_predicate_t *
dtrace_predicate_create(dtrace_difo_t *dp)
{
      dtrace_predicate_t *pred;

      ASSERT(MUTEX_HELD(&dtrace_lock));
      ASSERT(dp->dtdo_refcnt != 0);

      pred = kmem_zalloc(sizeof (dtrace_predicate_t), KM_SLEEP);
      pred->dtp_difo = dp;
      pred->dtp_refcnt = 1;

      if (!dtrace_difo_cacheable(dp))
            return (pred);

      if (dtrace_predcache_id == DTRACE_CACHEIDNONE) {
            /*
             * This is only theoretically possible -- we have had 2^32
             * cacheable predicates on this machine.  We cannot allow any
             * more predicates to become cacheable:  as unlikely as it is,
             * there may be a thread caching a (now stale) predicate cache
             * ID. (N.B.: the temptation is being successfully resisted to
             * have this cmn_err() "Holy shit -- we executed this code!")
             */
            return (pred);
      }

      pred->dtp_cacheid = dtrace_predcache_id++;

      return (pred);
}

static void
dtrace_predicate_hold(dtrace_predicate_t *pred)
{
      ASSERT(MUTEX_HELD(&dtrace_lock));
      ASSERT(pred->dtp_difo != NULL && pred->dtp_difo->dtdo_refcnt != 0);
      ASSERT(pred->dtp_refcnt > 0);

      pred->dtp_refcnt++;
}

static void
dtrace_predicate_release(dtrace_predicate_t *pred, dtrace_vstate_t *vstate)
{
      dtrace_difo_t *dp = pred->dtp_difo;

      ASSERT(MUTEX_HELD(&dtrace_lock));
      ASSERT(dp != NULL && dp->dtdo_refcnt != 0);
      ASSERT(pred->dtp_refcnt > 0);

      if (--pred->dtp_refcnt == 0) {
            dtrace_difo_release(pred->dtp_difo, vstate);
            kmem_free(pred, sizeof (dtrace_predicate_t));
      }
}

/*
 * DTrace Action Description Functions
 */
static dtrace_actdesc_t *
dtrace_actdesc_create(dtrace_actkind_t kind, uint32_t ntuple,
    uint64_t uarg, uint64_t arg)
{
      dtrace_actdesc_t *act;

#if defined(sun)
      ASSERT(!DTRACEACT_ISPRINTFLIKE(kind) || (arg != NULL &&
          arg >= KERNELBASE) || (arg == NULL && kind == DTRACEACT_PRINTA));
#endif

      act = kmem_zalloc(sizeof (dtrace_actdesc_t), KM_SLEEP);
      act->dtad_kind = kind;
      act->dtad_ntuple = ntuple;
      act->dtad_uarg = uarg;
      act->dtad_arg = arg;
      act->dtad_refcnt = 1;

      return (act);
}

static void
dtrace_actdesc_hold(dtrace_actdesc_t *act)
{
      ASSERT(act->dtad_refcnt >= 1);
      act->dtad_refcnt++;
}

static void
dtrace_actdesc_release(dtrace_actdesc_t *act, dtrace_vstate_t *vstate)
{
      dtrace_actkind_t kind = act->dtad_kind;
      dtrace_difo_t *dp;

      ASSERT(act->dtad_refcnt >= 1);

      if (--act->dtad_refcnt != 0)
            return;

      if ((dp = act->dtad_difo) != NULL)
            dtrace_difo_release(dp, vstate);

      if (DTRACEACT_ISPRINTFLIKE(kind)) {
            char *str = (char *)(uintptr_t)act->dtad_arg;

#if defined(sun)
            ASSERT((str != NULL && (uintptr_t)str >= KERNELBASE) ||
                (str == NULL && act->dtad_kind == DTRACEACT_PRINTA));
#endif

            if (str != NULL)
                  kmem_free(str, strlen(str) + 1);
      }

      kmem_free(act, sizeof (dtrace_actdesc_t));
}

/*
 * DTrace ECB Functions
 */
static dtrace_ecb_t *
dtrace_ecb_add(dtrace_state_t *state, dtrace_probe_t *probe)
{
      dtrace_ecb_t *ecb;
      dtrace_epid_t epid;

      ASSERT(MUTEX_HELD(&dtrace_lock));

      ecb = kmem_zalloc(sizeof (dtrace_ecb_t), KM_SLEEP);
      ecb->dte_predicate = NULL;
      ecb->dte_probe = probe;

      /*
       * The default size is the size of the default action: recording
       * the epid.
       */
      ecb->dte_size = ecb->dte_needed = sizeof (dtrace_epid_t);
      ecb->dte_alignment = sizeof (dtrace_epid_t);

      epid = state->dts_epid++;

      if (epid - 1 >= state->dts_necbs) {
            dtrace_ecb_t **oecbs = state->dts_ecbs, **ecbs;
            int necbs = state->dts_necbs << 1;

            ASSERT(epid == state->dts_necbs + 1);

            if (necbs == 0) {
                  ASSERT(oecbs == NULL);
                  necbs = 1;
            }

            ecbs = kmem_zalloc(necbs * sizeof (*ecbs), KM_SLEEP);

            if (oecbs != NULL)
                  bcopy(oecbs, ecbs, state->dts_necbs * sizeof (*ecbs));

            dtrace_membar_producer();
            state->dts_ecbs = ecbs;

            if (oecbs != NULL) {
                  /*
                   * If this state is active, we must dtrace_sync()
                   * before we can free the old dts_ecbs array:  we're
                   * coming in hot, and there may be active ring
                   * buffer processing (which indexes into the dts_ecbs
                   * array) on another CPU.
                   */
                  if (state->dts_activity != DTRACE_ACTIVITY_INACTIVE)
                        dtrace_sync();

                  kmem_free(oecbs, state->dts_necbs * sizeof (*ecbs));
            }

            dtrace_membar_producer();
            state->dts_necbs = necbs;
      }

      ecb->dte_state = state;

      ASSERT(state->dts_ecbs[epid - 1] == NULL);
      dtrace_membar_producer();
      state->dts_ecbs[(ecb->dte_epid = epid) - 1] = ecb;

      return (ecb);
}

static void
dtrace_ecb_enable(dtrace_ecb_t *ecb)
{
      dtrace_probe_t *probe = ecb->dte_probe;

      ASSERT(MUTEX_HELD(&cpu_lock));
      ASSERT(MUTEX_HELD(&dtrace_lock));
      ASSERT(ecb->dte_next == NULL);

      if (probe == NULL) {
            /*
             * This is the NULL probe -- there's nothing to do.
             */
            return;
      }

      if (probe->dtpr_ecb == NULL) {
            dtrace_provider_t *prov = probe->dtpr_provider;

            /*
             * We're the first ECB on this probe.
             */
            probe->dtpr_ecb = probe->dtpr_ecb_last = ecb;

            if (ecb->dte_predicate != NULL)
                  probe->dtpr_predcache = ecb->dte_predicate->dtp_cacheid;

            prov->dtpv_pops.dtps_enable(prov->dtpv_arg,
                probe->dtpr_id, probe->dtpr_arg);
      } else {
            /*
             * This probe is already active.  Swing the last pointer to
             * point to the new ECB, and issue a dtrace_sync() to assure
             * that all CPUs have seen the change.
             */
            ASSERT(probe->dtpr_ecb_last != NULL);
            probe->dtpr_ecb_last->dte_next = ecb;
            probe->dtpr_ecb_last = ecb;
            probe->dtpr_predcache = 0;

            dtrace_sync();
      }
}

static void
dtrace_ecb_resize(dtrace_ecb_t *ecb)
{
      uint32_t maxalign = sizeof (dtrace_epid_t);
      uint32_t align = sizeof (uint8_t), offs, diff;
      dtrace_action_t *act;
      int wastuple = 0;
      uint32_t aggbase = UINT32_MAX;
      dtrace_state_t *state = ecb->dte_state;

      /*
       * If we record anything, we always record the epid.  (And we always
       * record it first.)
       */
      offs = sizeof (dtrace_epid_t);
      ecb->dte_size = ecb->dte_needed = sizeof (dtrace_epid_t);

      for (act = ecb->dte_action; act != NULL; act = act->dta_next) {
            dtrace_recdesc_t *rec = &act->dta_rec;

            if ((align = rec->dtrd_alignment) > maxalign)
                  maxalign = align;

            if (!wastuple && act->dta_intuple) {
                  /*
                   * This is the first record in a tuple.  Align the
                   * offset to be at offset 4 in an 8-byte aligned
                   * block.
                   */
                  diff = offs + sizeof (dtrace_aggid_t);

                  if ((diff = (diff & (sizeof (uint64_t) - 1))))
                        offs += sizeof (uint64_t) - diff;

                  aggbase = offs - sizeof (dtrace_aggid_t);
                  ASSERT(!(aggbase & (sizeof (uint64_t) - 1)));
            }

            /*LINTED*/
            if (rec->dtrd_size != 0 && (diff = (offs & (align - 1)))) {
                  /*
                   * The current offset is not properly aligned; align it.
                   */
                  offs += align - diff;
            }

            rec->dtrd_offset = offs;

            if (offs + rec->dtrd_size > ecb->dte_needed) {
                  ecb->dte_needed = offs + rec->dtrd_size;

                  if (ecb->dte_needed > state->dts_needed)
                        state->dts_needed = ecb->dte_needed;
            }

            if (DTRACEACT_ISAGG(act->dta_kind)) {
                  dtrace_aggregation_t *agg = (dtrace_aggregation_t *)act;
                  dtrace_action_t *first = agg->dtag_first, *prev;

                  ASSERT(rec->dtrd_size != 0 && first != NULL);
                  ASSERT(wastuple);
                  ASSERT(aggbase != UINT32_MAX);

                  agg->dtag_base = aggbase;

                  while ((prev = first->dta_prev) != NULL &&
                      DTRACEACT_ISAGG(prev->dta_kind)) {
                        agg = (dtrace_aggregation_t *)prev;
                        first = agg->dtag_first;
                  }

                  if (prev != NULL) {
                        offs = prev->dta_rec.dtrd_offset +
                            prev->dta_rec.dtrd_size;
                  } else {
                        offs = sizeof (dtrace_epid_t);
                  }
                  wastuple = 0;
            } else {
                  if (!act->dta_intuple)
                        ecb->dte_size = offs + rec->dtrd_size;

                  offs += rec->dtrd_size;
            }

            wastuple = act->dta_intuple;
      }

      if ((act = ecb->dte_action) != NULL &&
          !(act->dta_kind == DTRACEACT_SPECULATE && act->dta_next == NULL) &&
          ecb->dte_size == sizeof (dtrace_epid_t)) {
            /*
             * If the size is still sizeof (dtrace_epid_t), then all
             * actions store no data; set the size to 0.
             */
            ecb->dte_alignment = maxalign;
            ecb->dte_size = 0;

            /*
             * If the needed space is still sizeof (dtrace_epid_t), then
             * all actions need no additional space; set the needed
             * size to 0.
             */
            if (ecb->dte_needed == sizeof (dtrace_epid_t))
                  ecb->dte_needed = 0;

            return;
      }

      /*
       * Set our alignment, and make sure that the dte_size and dte_needed
       * are aligned to the size of an EPID.
       */
      ecb->dte_alignment = maxalign;
      ecb->dte_size = (ecb->dte_size + (sizeof (dtrace_epid_t) - 1)) &
          ~(sizeof (dtrace_epid_t) - 1);
      ecb->dte_needed = (ecb->dte_needed + (sizeof (dtrace_epid_t) - 1)) &
          ~(sizeof (dtrace_epid_t) - 1);
      ASSERT(ecb->dte_size <= ecb->dte_needed);
}

static dtrace_action_t *
dtrace_ecb_aggregation_create(dtrace_ecb_t *ecb, dtrace_actdesc_t *desc)
{
      dtrace_aggregation_t *agg;
      size_t size = sizeof (uint64_t);
      int ntuple = desc->dtad_ntuple;
      dtrace_action_t *act;
      dtrace_recdesc_t *frec;
      dtrace_aggid_t aggid;
      dtrace_state_t *state = ecb->dte_state;

      agg = kmem_zalloc(sizeof (dtrace_aggregation_t), KM_SLEEP);
      agg->dtag_ecb = ecb;

      ASSERT(DTRACEACT_ISAGG(desc->dtad_kind));

      switch (desc->dtad_kind) {
      case DTRACEAGG_MIN:
            agg->dtag_initial = INT64_MAX;
            agg->dtag_aggregate = dtrace_aggregate_min;
            break;

      case DTRACEAGG_MAX:
            agg->dtag_initial = INT64_MIN;
            agg->dtag_aggregate = dtrace_aggregate_max;
            break;

      case DTRACEAGG_COUNT:
            agg->dtag_aggregate = dtrace_aggregate_count;
            break;

      case DTRACEAGG_QUANTIZE:
            agg->dtag_aggregate = dtrace_aggregate_quantize;
            size = (((sizeof (uint64_t) * NBBY) - 1) * 2 + 1) *
                sizeof (uint64_t);
            break;

      case DTRACEAGG_LQUANTIZE: {
            uint16_t step = DTRACE_LQUANTIZE_STEP(desc->dtad_arg);
            uint16_t levels = DTRACE_LQUANTIZE_LEVELS(desc->dtad_arg);

            agg->dtag_initial = desc->dtad_arg;
            agg->dtag_aggregate = dtrace_aggregate_lquantize;

            if (step == 0 || levels == 0)
                  goto err;

            size = levels * sizeof (uint64_t) + 3 * sizeof (uint64_t);
            break;
      }

      case DTRACEAGG_AVG:
            agg->dtag_aggregate = dtrace_aggregate_avg;
            size = sizeof (uint64_t) * 2;
            break;

      case DTRACEAGG_STDDEV:
            agg->dtag_aggregate = dtrace_aggregate_stddev;
            size = sizeof (uint64_t) * 4;
            break;

      case DTRACEAGG_SUM:
            agg->dtag_aggregate = dtrace_aggregate_sum;
            break;

      default:
            goto err;
      }

      agg->dtag_action.dta_rec.dtrd_size = size;

      if (ntuple == 0)
            goto err;

      /*
       * We must make sure that we have enough actions for the n-tuple.
       */
      for (act = ecb->dte_action_last; act != NULL; act = act->dta_prev) {
            if (DTRACEACT_ISAGG(act->dta_kind))
                  break;

            if (--ntuple == 0) {
                  /*
                   * This is the action with which our n-tuple begins.
                   */
                  agg->dtag_first = act;
                  goto success;
            }
      }

      /*
       * This n-tuple is short by ntuple elements.  Return failure.
       */
      ASSERT(ntuple != 0);
err:
      kmem_free(agg, sizeof (dtrace_aggregation_t));
      return (NULL);

success:
      /*
       * If the last action in the tuple has a size of zero, it's actually
       * an expression argument for the aggregating action.
       */
      ASSERT(ecb->dte_action_last != NULL);
      act = ecb->dte_action_last;

      if (act->dta_kind == DTRACEACT_DIFEXPR) {
            ASSERT(act->dta_difo != NULL);

            if (act->dta_difo->dtdo_rtype.dtdt_size == 0)
                  agg->dtag_hasarg = 1;
      }

      /*
       * We need to allocate an id for this aggregation.
       */
#if defined(sun)
      aggid = (dtrace_aggid_t)(uintptr_t)vmem_alloc(state->dts_aggid_arena, 1,
          VM_BESTFIT | VM_SLEEP);
#else
      aggid = alloc_unr(state->dts_aggid_arena);
#endif

      if (aggid - 1 >= state->dts_naggregations) {
            dtrace_aggregation_t **oaggs = state->dts_aggregations;
            dtrace_aggregation_t **aggs;
            int naggs = state->dts_naggregations << 1;
            int onaggs = state->dts_naggregations;

            ASSERT(aggid == state->dts_naggregations + 1);

            if (naggs == 0) {
                  ASSERT(oaggs == NULL);
                  naggs = 1;
            }

            aggs = kmem_zalloc(naggs * sizeof (*aggs), KM_SLEEP);

            if (oaggs != NULL) {
                  bcopy(oaggs, aggs, onaggs * sizeof (*aggs));
                  kmem_free(oaggs, onaggs * sizeof (*aggs));
            }

            state->dts_aggregations = aggs;
            state->dts_naggregations = naggs;
      }

      ASSERT(state->dts_aggregations[aggid - 1] == NULL);
      state->dts_aggregations[(agg->dtag_id = aggid) - 1] = agg;

      frec = &agg->dtag_first->dta_rec;
      if (frec->dtrd_alignment < sizeof (dtrace_aggid_t))
            frec->dtrd_alignment = sizeof (dtrace_aggid_t);

      for (act = agg->dtag_first; act != NULL; act = act->dta_next) {
            ASSERT(!act->dta_intuple);
            act->dta_intuple = 1;
      }

      return (&agg->dtag_action);
}

static void
dtrace_ecb_aggregation_destroy(dtrace_ecb_t *ecb, dtrace_action_t *act)
{
      dtrace_aggregation_t *agg = (dtrace_aggregation_t *)act;
      dtrace_state_t *state = ecb->dte_state;
      dtrace_aggid_t aggid = agg->dtag_id;

      ASSERT(DTRACEACT_ISAGG(act->dta_kind));
#if defined(sun)
      vmem_free(state->dts_aggid_arena, (void *)(uintptr_t)aggid, 1);
#else
      free_unr(state->dts_aggid_arena, aggid);
#endif

      ASSERT(state->dts_aggregations[aggid - 1] == agg);
      state->dts_aggregations[aggid - 1] = NULL;

      kmem_free(agg, sizeof (dtrace_aggregation_t));
}

static int
dtrace_ecb_action_add(dtrace_ecb_t *ecb, dtrace_actdesc_t *desc)
{
      dtrace_action_t *action, *last;
      dtrace_difo_t *dp = desc->dtad_difo;
      uint32_t size = 0, align = sizeof (uint8_t), mask;
      uint16_t format = 0;
      dtrace_recdesc_t *rec;
      dtrace_state_t *state = ecb->dte_state;
      dtrace_optval_t *opt = state->dts_options, nframes = 0, strsize;
      uint64_t arg = desc->dtad_arg;

      ASSERT(MUTEX_HELD(&dtrace_lock));
      ASSERT(ecb->dte_action == NULL || ecb->dte_action->dta_refcnt == 1);

      if (DTRACEACT_ISAGG(desc->dtad_kind)) {
            /*
             * If this is an aggregating action, there must be neither
             * a speculate nor a commit on the action chain.
             */
            dtrace_action_t *act;

            for (act = ecb->dte_action; act != NULL; act = act->dta_next) {
                  if (act->dta_kind == DTRACEACT_COMMIT)
                        return (EINVAL);

                  if (act->dta_kind == DTRACEACT_SPECULATE)
                        return (EINVAL);
            }

            action = dtrace_ecb_aggregation_create(ecb, desc);

            if (action == NULL)
                  return (EINVAL);
      } else {
            if (DTRACEACT_ISDESTRUCTIVE(desc->dtad_kind) ||
                (desc->dtad_kind == DTRACEACT_DIFEXPR &&
                dp != NULL && dp->dtdo_destructive)) {
                  state->dts_destructive = 1;
            }

            switch (desc->dtad_kind) {
            case DTRACEACT_PRINTF:
            case DTRACEACT_PRINTA:
            case DTRACEACT_SYSTEM:
            case DTRACEACT_FREOPEN:
                  /*
                   * We know that our arg is a string -- turn it into a
                   * format.
                   */
                  if (arg == 0) {
                        ASSERT(desc->dtad_kind == DTRACEACT_PRINTA);
                        format = 0;
                  } else {
                        ASSERT(arg != 0);
#if defined(sun)
                        ASSERT(arg > KERNELBASE);
#endif
                        format = dtrace_format_add(state,
                            (char *)(uintptr_t)arg);
                  }

                  /*FALLTHROUGH*/
            case DTRACEACT_LIBACT:
            case DTRACEACT_DIFEXPR:
                  if (dp == NULL)
                        return (EINVAL);

                  if ((size = dp->dtdo_rtype.dtdt_size) != 0)
                        break;

                  if (dp->dtdo_rtype.dtdt_kind == DIF_TYPE_STRING) {
                        if (!(dp->dtdo_rtype.dtdt_flags & DIF_TF_BYREF))
                              return (EINVAL);

                        size = opt[DTRACEOPT_STRSIZE];
                  }

                  break;

            case DTRACEACT_STACK:
                  if ((nframes = arg) == 0) {
                        nframes = opt[DTRACEOPT_STACKFRAMES];
                        ASSERT(nframes > 0);
                        arg = nframes;
                  }

                  size = nframes * sizeof (pc_t);
                  break;

            case DTRACEACT_JSTACK:
                  if ((strsize = DTRACE_USTACK_STRSIZE(arg)) == 0)
                        strsize = opt[DTRACEOPT_JSTACKSTRSIZE];

                  if ((nframes = DTRACE_USTACK_NFRAMES(arg)) == 0)
                        nframes = opt[DTRACEOPT_JSTACKFRAMES];

                  arg = DTRACE_USTACK_ARG(nframes, strsize);

                  /*FALLTHROUGH*/
            case DTRACEACT_USTACK:
                  if (desc->dtad_kind != DTRACEACT_JSTACK &&
                      (nframes = DTRACE_USTACK_NFRAMES(arg)) == 0) {
                        strsize = DTRACE_USTACK_STRSIZE(arg);
                        nframes = opt[DTRACEOPT_USTACKFRAMES];
                        ASSERT(nframes > 0);
                        arg = DTRACE_USTACK_ARG(nframes, strsize);
                  }

                  /*
                   * Save a slot for the pid.
                   */
                  size = (nframes + 1) * sizeof (uint64_t);
                  size += DTRACE_USTACK_STRSIZE(arg);
                  size = P2ROUNDUP(size, (uint32_t)(sizeof (uintptr_t)));

                  break;

            case DTRACEACT_SYM:
            case DTRACEACT_MOD:
                  if (dp == NULL || ((size = dp->dtdo_rtype.dtdt_size) !=
                      sizeof (uint64_t)) ||
                      (dp->dtdo_rtype.dtdt_flags & DIF_TF_BYREF))
                        return (EINVAL);
                  break;

            case DTRACEACT_USYM:
            case DTRACEACT_UMOD:
            case DTRACEACT_UADDR:
                  if (dp == NULL ||
                      (dp->dtdo_rtype.dtdt_size != sizeof (uint64_t)) ||
                      (dp->dtdo_rtype.dtdt_flags & DIF_TF_BYREF))
                        return (EINVAL);

                  /*
                   * We have a slot for the pid, plus a slot for the
                   * argument.  To keep things simple (aligned with
                   * bitness-neutral sizing), we store each as a 64-bit
                   * quantity.
                   */
                  size = 2 * sizeof (uint64_t);
                  break;

            case DTRACEACT_STOP:
            case DTRACEACT_BREAKPOINT:
            case DTRACEACT_PANIC:
                  break;

            case DTRACEACT_CHILL:
            case DTRACEACT_DISCARD:
            case DTRACEACT_RAISE:
                  if (dp == NULL)
                        return (EINVAL);
                  break;

            case DTRACEACT_EXIT:
                  if (dp == NULL ||
                      (size = dp->dtdo_rtype.dtdt_size) != sizeof (int) ||
                      (dp->dtdo_rtype.dtdt_flags & DIF_TF_BYREF))
                        return (EINVAL);
                  break;

            case DTRACEACT_SPECULATE:
                  if (ecb->dte_size > sizeof (dtrace_epid_t))
                        return (EINVAL);

                  if (dp == NULL)
                        return (EINVAL);

                  state->dts_speculates = 1;
                  break;

            case DTRACEACT_PRINTM:
                  size = dp->dtdo_rtype.dtdt_size;
                  break;

            case DTRACEACT_PRINTT:
                  size = dp->dtdo_rtype.dtdt_size;
                  break;

            case DTRACEACT_COMMIT: {
                  dtrace_action_t *act = ecb->dte_action;

                  for (; act != NULL; act = act->dta_next) {
                        if (act->dta_kind == DTRACEACT_COMMIT)
                              return (EINVAL);
                  }

                  if (dp == NULL)
                        return (EINVAL);
                  break;
            }

            default:
                  return (EINVAL);
            }

            if (size != 0 || desc->dtad_kind == DTRACEACT_SPECULATE) {
                  /*
                   * If this is a data-storing action or a speculate,
                   * we must be sure that there isn't a commit on the
                   * action chain.
                   */
                  dtrace_action_t *act = ecb->dte_action;

                  for (; act != NULL; act = act->dta_next) {
                        if (act->dta_kind == DTRACEACT_COMMIT)
                              return (EINVAL);
                  }
            }

            action = kmem_zalloc(sizeof (dtrace_action_t), KM_SLEEP);
            action->dta_rec.dtrd_size = size;
      }

      action->dta_refcnt = 1;
      rec = &action->dta_rec;
      size = rec->dtrd_size;

      for (mask = sizeof (uint64_t) - 1; size != 0 && mask > 0; mask >>= 1) {
            if (!(size & mask)) {
                  align = mask + 1;
                  break;
            }
      }

      action->dta_kind = desc->dtad_kind;

      if ((action->dta_difo = dp) != NULL)
            dtrace_difo_hold(dp);

      rec->dtrd_action = action->dta_kind;
      rec->dtrd_arg = arg;
      rec->dtrd_uarg = desc->dtad_uarg;
      rec->dtrd_alignment = (uint16_t)align;
      rec->dtrd_format = format;

      if ((last = ecb->dte_action_last) != NULL) {
            ASSERT(ecb->dte_action != NULL);
            action->dta_prev = last;
            last->dta_next = action;
      } else {
            ASSERT(ecb->dte_action == NULL);
            ecb->dte_action = action;
      }

      ecb->dte_action_last = action;

      return (0);
}

static void
dtrace_ecb_action_remove(dtrace_ecb_t *ecb)
{
      dtrace_action_t *act = ecb->dte_action, *next;
      dtrace_vstate_t *vstate = &ecb->dte_state->dts_vstate;
      dtrace_difo_t *dp;
      uint16_t format;

      if (act != NULL && act->dta_refcnt > 1) {
            ASSERT(act->dta_next == NULL || act->dta_next->dta_refcnt == 1);
            act->dta_refcnt--;
      } else {
            for (; act != NULL; act = next) {
                  next = act->dta_next;
                  ASSERT(next != NULL || act == ecb->dte_action_last);
                  ASSERT(act->dta_refcnt == 1);

                  if ((format = act->dta_rec.dtrd_format) != 0)
                        dtrace_format_remove(ecb->dte_state, format);

                  if ((dp = act->dta_difo) != NULL)
                        dtrace_difo_release(dp, vstate);

                  if (DTRACEACT_ISAGG(act->dta_kind)) {
                        dtrace_ecb_aggregation_destroy(ecb, act);
                  } else {
                        kmem_free(act, sizeof (dtrace_action_t));
                  }
            }
      }

      ecb->dte_action = NULL;
      ecb->dte_action_last = NULL;
      ecb->dte_size = sizeof (dtrace_epid_t);
}

static void
dtrace_ecb_disable(dtrace_ecb_t *ecb)
{
      /*
       * We disable the ECB by removing it from its probe.
       */
      dtrace_ecb_t *pecb, *prev = NULL;
      dtrace_probe_t *probe = ecb->dte_probe;

      ASSERT(MUTEX_HELD(&dtrace_lock));

      if (probe == NULL) {
            /*
             * This is the NULL probe; there is nothing to disable.
             */
            return;
      }

      for (pecb = probe->dtpr_ecb; pecb != NULL; pecb = pecb->dte_next) {
            if (pecb == ecb)
                  break;
            prev = pecb;
      }

      ASSERT(pecb != NULL);

      if (prev == NULL) {
            probe->dtpr_ecb = ecb->dte_next;
      } else {
            prev->dte_next = ecb->dte_next;
      }

      if (ecb == probe->dtpr_ecb_last) {
            ASSERT(ecb->dte_next == NULL);
            probe->dtpr_ecb_last = prev;
      }

      /*
       * The ECB has been disconnected from the probe; now sync to assure
       * that all CPUs have seen the change before returning.
       */
      dtrace_sync();

      if (probe->dtpr_ecb == NULL) {
            /*
             * That was the last ECB on the probe; clear the predicate
             * cache ID for the probe, disable it and sync one more time
             * to assure that we'll never hit it again.
             */
            dtrace_provider_t *prov = probe->dtpr_provider;

            ASSERT(ecb->dte_next == NULL);
            ASSERT(probe->dtpr_ecb_last == NULL);
            probe->dtpr_predcache = DTRACE_CACHEIDNONE;
            prov->dtpv_pops.dtps_disable(prov->dtpv_arg,
                probe->dtpr_id, probe->dtpr_arg);
            dtrace_sync();
      } else {
            /*
             * There is at least one ECB remaining on the probe.  If there
             * is _exactly_ one, set the probe's predicate cache ID to be
             * the predicate cache ID of the remaining ECB.
             */
            ASSERT(probe->dtpr_ecb_last != NULL);
            ASSERT(probe->dtpr_predcache == DTRACE_CACHEIDNONE);

            if (probe->dtpr_ecb == probe->dtpr_ecb_last) {
                  dtrace_predicate_t *p = probe->dtpr_ecb->dte_predicate;

                  ASSERT(probe->dtpr_ecb->dte_next == NULL);

                  if (p != NULL)
                        probe->dtpr_predcache = p->dtp_cacheid;
            }

            ecb->dte_next = NULL;
      }
}

static void
dtrace_ecb_destroy(dtrace_ecb_t *ecb)
{
      dtrace_state_t *state = ecb->dte_state;
      dtrace_vstate_t *vstate = &state->dts_vstate;
      dtrace_predicate_t *pred;
      dtrace_epid_t epid = ecb->dte_epid;

      ASSERT(MUTEX_HELD(&dtrace_lock));
      ASSERT(ecb->dte_next == NULL);
      ASSERT(ecb->dte_probe == NULL || ecb->dte_probe->dtpr_ecb != ecb);

      if ((pred = ecb->dte_predicate) != NULL)
            dtrace_predicate_release(pred, vstate);

      dtrace_ecb_action_remove(ecb);

      ASSERT(state->dts_ecbs[epid - 1] == ecb);
      state->dts_ecbs[epid - 1] = NULL;

      kmem_free(ecb, sizeof (dtrace_ecb_t));
}

static dtrace_ecb_t *
dtrace_ecb_create(dtrace_state_t *state, dtrace_probe_t *probe,
    dtrace_enabling_t *enab)
{
      dtrace_ecb_t *ecb;
      dtrace_predicate_t *pred;
      dtrace_actdesc_t *act;
      dtrace_provider_t *prov;
      dtrace_ecbdesc_t *desc = enab->dten_current;

      ASSERT(MUTEX_HELD(&dtrace_lock));
      ASSERT(state != NULL);

      ecb = dtrace_ecb_add(state, probe);
      ecb->dte_uarg = desc->dted_uarg;

      if ((pred = desc->dted_pred.dtpdd_predicate) != NULL) {
            dtrace_predicate_hold(pred);
            ecb->dte_predicate = pred;
      }

      if (probe != NULL) {
            /*
             * If the provider shows more leg than the consumer is old
             * enough to see, we need to enable the appropriate implicit
             * predicate bits to prevent the ecb from activating at
             * revealing times.
             *
             * Providers specifying DTRACE_PRIV_USER at register time
             * are stating that they need the /proc-style privilege
             * model to be enforced, and this is what DTRACE_COND_OWNER
             * and DTRACE_COND_ZONEOWNER will then do at probe time.
             */
            prov = probe->dtpr_provider;
            if (!(state->dts_cred.dcr_visible & DTRACE_CRV_ALLPROC) &&
                (prov->dtpv_priv.dtpp_flags & DTRACE_PRIV_USER))
                  ecb->dte_cond |= DTRACE_COND_OWNER;

            if (!(state->dts_cred.dcr_visible & DTRACE_CRV_ALLZONE) &&
                (prov->dtpv_priv.dtpp_flags & DTRACE_PRIV_USER))
                  ecb->dte_cond |= DTRACE_COND_ZONEOWNER;

            /*
             * If the provider shows us kernel innards and the user
             * is lacking sufficient privilege, enable the
             * DTRACE_COND_USERMODE implicit predicate.
             */
            if (!(state->dts_cred.dcr_visible & DTRACE_CRV_KERNEL) &&
                (prov->dtpv_priv.dtpp_flags & DTRACE_PRIV_KERNEL))
                  ecb->dte_cond |= DTRACE_COND_USERMODE;
      }

      if (dtrace_ecb_create_cache != NULL) {
            /*
             * If we have a cached ecb, we'll use its action list instead
             * of creating our own (saving both time and space).
             */
            dtrace_ecb_t *cached = dtrace_ecb_create_cache;
            dtrace_action_t *act = cached->dte_action;

            if (act != NULL) {
                  ASSERT(act->dta_refcnt > 0);
                  act->dta_refcnt++;
                  ecb->dte_action = act;
                  ecb->dte_action_last = cached->dte_action_last;
                  ecb->dte_needed = cached->dte_needed;
                  ecb->dte_size = cached->dte_size;
                  ecb->dte_alignment = cached->dte_alignment;
            }

            return (ecb);
      }

      for (act = desc->dted_action; act != NULL; act = act->dtad_next) {
            if ((enab->dten_error = dtrace_ecb_action_add(ecb, act)) != 0) {
                  dtrace_ecb_destroy(ecb);
                  return (NULL);
            }
      }

      dtrace_ecb_resize(ecb);

      return (dtrace_ecb_create_cache = ecb);
}

static int
dtrace_ecb_create_enable(dtrace_probe_t *probe, void *arg)
{
      dtrace_ecb_t *ecb;
      dtrace_enabling_t *enab = arg;
      dtrace_state_t *state = enab->dten_vstate->dtvs_state;

      ASSERT(state != NULL);

      if (probe != NULL && probe->dtpr_gen < enab->dten_probegen) {
            /*
             * This probe was created in a generation for which this
             * enabling has previously created ECBs; we don't want to
             * enable it again, so just kick out.
             */
            return (DTRACE_MATCH_NEXT);
      }

      if ((ecb = dtrace_ecb_create(state, probe, enab)) == NULL)
            return (DTRACE_MATCH_DONE);

      dtrace_ecb_enable(ecb);
      return (DTRACE_MATCH_NEXT);
}

static dtrace_ecb_t *
dtrace_epid2ecb(dtrace_state_t *state, dtrace_epid_t id)
{
      dtrace_ecb_t *ecb;

      ASSERT(MUTEX_HELD(&dtrace_lock));

      if (id == 0 || id > state->dts_necbs)
            return (NULL);

      ASSERT(state->dts_necbs > 0 && state->dts_ecbs != NULL);
      ASSERT((ecb = state->dts_ecbs[id - 1]) == NULL || ecb->dte_epid == id);

      return (state->dts_ecbs[id - 1]);
}

static dtrace_aggregation_t *
dtrace_aggid2agg(dtrace_state_t *state, dtrace_aggid_t id)
{
      dtrace_aggregation_t *agg;

      ASSERT(MUTEX_HELD(&dtrace_lock));

      if (id == 0 || id > state->dts_naggregations)
            return (NULL);

      ASSERT(state->dts_naggregations > 0 && state->dts_aggregations != NULL);
      ASSERT((agg = state->dts_aggregations[id - 1]) == NULL ||
          agg->dtag_id == id);

      return (state->dts_aggregations[id - 1]);
}

/*
 * DTrace Buffer Functions
 *
 * The following functions manipulate DTrace buffers.  Most of these functions
 * are called in the context of establishing or processing consumer state;
 * exceptions are explicitly noted.
 */

/*
 * Note:  called from cross call context.  This function switches the two
 * buffers on a given CPU.  The atomicity of this operation is assured by
 * disabling interrupts while the actual switch takes place; the disabling of
 * interrupts serializes the execution with any execution of dtrace_probe() on
 * the same CPU.
 */
static void
dtrace_buffer_switch(dtrace_buffer_t *buf)
{
      caddr_t tomax = buf->dtb_tomax;
      caddr_t xamot = buf->dtb_xamot;
      dtrace_icookie_t cookie;

      ASSERT(!(buf->dtb_flags & DTRACEBUF_NOSWITCH));
      ASSERT(!(buf->dtb_flags & DTRACEBUF_RING));

      cookie = dtrace_interrupt_disable();
      buf->dtb_tomax = xamot;
      buf->dtb_xamot = tomax;
      buf->dtb_xamot_drops = buf->dtb_drops;
      buf->dtb_xamot_offset = buf->dtb_offset;
      buf->dtb_xamot_errors = buf->dtb_errors;
      buf->dtb_xamot_flags = buf->dtb_flags;
      buf->dtb_offset = 0;
      buf->dtb_drops = 0;
      buf->dtb_errors = 0;
      buf->dtb_flags &= ~(DTRACEBUF_ERROR | DTRACEBUF_DROPPED);
      dtrace_interrupt_enable(cookie);
}

/*
 * Note:  called from cross call context.  This function activates a buffer
 * on a CPU.  As with dtrace_buffer_switch(), the atomicity of the operation
 * is guaranteed by the disabling of interrupts.
 */
static void
dtrace_buffer_activate(dtrace_state_t *state)
{
      dtrace_buffer_t *buf;
      dtrace_icookie_t cookie = dtrace_interrupt_disable();

      buf = &state->dts_buffer[curcpu];

      if (buf->dtb_tomax != NULL) {
            /*
             * We might like to assert that the buffer is marked inactive,
             * but this isn't necessarily true:  the buffer for the CPU
             * that processes the BEGIN probe has its buffer activated
             * manually.  In this case, we take the (harmless) action
             * re-clearing the bit INACTIVE bit.
             */
            buf->dtb_flags &= ~DTRACEBUF_INACTIVE;
      }

      dtrace_interrupt_enable(cookie);
}

static int
dtrace_buffer_alloc(dtrace_buffer_t *bufs, size_t size, int flags,
    processorid_t cpu)
{
#if defined(sun)
      cpu_t *cp;
#else
      struct pcpu *cp;
#endif
      dtrace_buffer_t *buf;

#if defined(sun)
      ASSERT(MUTEX_HELD(&cpu_lock));
      ASSERT(MUTEX_HELD(&dtrace_lock));

      if (size > dtrace_nonroot_maxsize &&
          !PRIV_POLICY_CHOICE(CRED(), PRIV_ALL, B_FALSE))
            return (EFBIG);

      cp = cpu_list;

      do {
            if (cpu != DTRACE_CPUALL && cpu != cp->cpu_id)
                  continue;

            buf = &bufs[cp->cpu_id];

            /*
             * If there is already a buffer allocated for this CPU, it
             * is only possible that this is a DR event.  In this case,
             */
            if (buf->dtb_tomax != NULL) {
                  ASSERT(buf->dtb_size == size);
                  continue;
            }

            ASSERT(buf->dtb_xamot == NULL);

            if ((buf->dtb_tomax = kmem_zalloc(size, KM_NOSLEEP)) == NULL)
                  goto err;

            buf->dtb_size = size;
            buf->dtb_flags = flags;
            buf->dtb_offset = 0;
            buf->dtb_drops = 0;

            if (flags & DTRACEBUF_NOSWITCH)
                  continue;

            if ((buf->dtb_xamot = kmem_zalloc(size, KM_NOSLEEP)) == NULL)
                  goto err;
      } while ((cp = cp->cpu_next) != cpu_list);

      return (0);

err:
      cp = cpu_list;

      do {
            if (cpu != DTRACE_CPUALL && cpu != cp->cpu_id)
                  continue;

            buf = &bufs[cp->cpu_id];

            if (buf->dtb_xamot != NULL) {
                  ASSERT(buf->dtb_tomax != NULL);
                  ASSERT(buf->dtb_size == size);
                  kmem_free(buf->dtb_xamot, size);
            }

            if (buf->dtb_tomax != NULL) {
                  ASSERT(buf->dtb_size == size);
                  kmem_free(buf->dtb_tomax, size);
            }

            buf->dtb_tomax = NULL;
            buf->dtb_xamot = NULL;
            buf->dtb_size = 0;
      } while ((cp = cp->cpu_next) != cpu_list);

      return (ENOMEM);
#else
      int i;

#if defined(__amd64__)
      /*
       * FreeBSD isn't good at limiting the amount of memory we
       * ask to malloc, so let's place a limit here before trying
       * to do something that might well end in tears at bedtime.
       */
      if (size > physmem * PAGE_SIZE / (128 * (mp_maxid + 1)))
            return(ENOMEM);
#endif

      ASSERT(MUTEX_HELD(&dtrace_lock));
      for (i = 0; i <= mp_maxid; i++) {
            if ((cp = pcpu_find(i)) == NULL)
                  continue;

            if (cpu != DTRACE_CPUALL && cpu != i)
                  continue;

            buf = &bufs[i];

            /*
             * If there is already a buffer allocated for this CPU, it
             * is only possible that this is a DR event.  In this case,
             * the buffer size must match our specified size.
             */
            if (buf->dtb_tomax != NULL) {
                  ASSERT(buf->dtb_size == size);
                  continue;
            }

            ASSERT(buf->dtb_xamot == NULL);

            if ((buf->dtb_tomax = kmem_zalloc(size, KM_NOSLEEP)) == NULL)
                  goto err;

            buf->dtb_size = size;
            buf->dtb_flags = flags;
            buf->dtb_offset = 0;
            buf->dtb_drops = 0;

            if (flags & DTRACEBUF_NOSWITCH)
                  continue;

            if ((buf->dtb_xamot = kmem_zalloc(size, KM_NOSLEEP)) == NULL)
                  goto err;
      }

      return (0);

err:
      /*
       * Error allocating memory, so free the buffers that were
       * allocated before the failed allocation.
       */
      for (i = 0; i <= mp_maxid; i++) {
            if ((cp = pcpu_find(i)) == NULL)
                  continue;

            if (cpu != DTRACE_CPUALL && cpu != i)
                  continue;

            buf = &bufs[i];

            if (buf->dtb_xamot != NULL) {
                  ASSERT(buf->dtb_tomax != NULL);
                  ASSERT(buf->dtb_size == size);
                  kmem_free(buf->dtb_xamot, size);
            }

            if (buf->dtb_tomax != NULL) {
                  ASSERT(buf->dtb_size == size);
                  kmem_free(buf->dtb_tomax, size);
            }

            buf->dtb_tomax = NULL;
            buf->dtb_xamot = NULL;
            buf->dtb_size = 0;

      }

      return (ENOMEM);
#endif
}

/*
 * Note:  called from probe context.  This function just increments the drop
 * count on a buffer.  It has been made a function to allow for the
 * possibility of understanding the source of mysterious drop counts.  (A
 * problem for which one may be particularly disappointed that DTrace cannot
 * be used to understand DTrace.)
 */
static void
dtrace_buffer_drop(dtrace_buffer_t *buf)
{
      buf->dtb_drops++;
}

/*
 * Note:  called from probe context.  This function is called to reserve space
 * in a buffer.  If mstate is non-NULL, sets the scratch base and size in the
 * mstate.  Returns the new offset in the buffer, or a negative value if an
 * error has occurred.
 */
static intptr_t
dtrace_buffer_reserve(dtrace_buffer_t *buf, size_t needed, size_t align,
    dtrace_state_t *state, dtrace_mstate_t *mstate)
{
      intptr_t offs = buf->dtb_offset, soffs;
      intptr_t woffs;
      caddr_t tomax;
      size_t total;

      if (buf->dtb_flags & DTRACEBUF_INACTIVE)
            return (-1);

      if ((tomax = buf->dtb_tomax) == NULL) {
            dtrace_buffer_drop(buf);
            return (-1);
      }

      if (!(buf->dtb_flags & (DTRACEBUF_RING | DTRACEBUF_FILL))) {
            while (offs & (align - 1)) {
                  /*
                   * Assert that our alignment is off by a number which
                   * is itself sizeof (uint32_t) aligned.
                   */
                  ASSERT(!((align - (offs & (align - 1))) &
                      (sizeof (uint32_t) - 1)));
                  DTRACE_STORE(uint32_t, tomax, offs, DTRACE_EPIDNONE);
                  offs += sizeof (uint32_t);
            }

            if ((soffs = offs + needed) > buf->dtb_size) {
                  dtrace_buffer_drop(buf);
                  return (-1);
            }

            if (mstate == NULL)
                  return (offs);

            mstate->dtms_scratch_base = (uintptr_t)tomax + soffs;
            mstate->dtms_scratch_size = buf->dtb_size - soffs;
            mstate->dtms_scratch_ptr = mstate->dtms_scratch_base;

            return (offs);
      }

      if (buf->dtb_flags & DTRACEBUF_FILL) {
            if (state->dts_activity != DTRACE_ACTIVITY_COOLDOWN &&
                (buf->dtb_flags & DTRACEBUF_FULL))
                  return (-1);
            goto out;
      }

      total = needed + (offs & (align - 1));

      /*
       * For a ring buffer, life is quite a bit more complicated.  Before
       * we can store any padding, we need to adjust our wrapping offset.
       * (If we've never before wrapped or we're not about to, no adjustment
       * is required.)
       */
      if ((buf->dtb_flags & DTRACEBUF_WRAPPED) ||
          offs + total > buf->dtb_size) {
            woffs = buf->dtb_xamot_offset;

            if (offs + total > buf->dtb_size) {
                  /*
                   * We can't fit in the end of the buffer.  First, a
                   * sanity check that we can fit in the buffer at all.
                   */
                  if (total > buf->dtb_size) {
                        dtrace_buffer_drop(buf);
                        return (-1);
                  }

                  /*
                   * We're going to be storing at the top of the buffer,
                   * so now we need to deal with the wrapped offset.  We
                   * only reset our wrapped offset to 0 if it is
                   * currently greater than the current offset.  If it
                   * is less than the current offset, it is because a
                   * previous allocation induced a wrap -- but the
                   * allocation didn't subsequently take the space due
                   * to an error or false predicate evaluation.  In this
                   * case, we'll just leave the wrapped offset alone: if
                   * the wrapped offset hasn't been advanced far enough
                   * for this allocation, it will be adjusted in the
                   * lower loop.
                   */
                  if (buf->dtb_flags & DTRACEBUF_WRAPPED) {
                        if (woffs >= offs)
                              woffs = 0;
                  } else {
                        woffs = 0;
                  }

                  /*
                   * Now we know that we're going to be storing to the
                   * top of the buffer and that there is room for us
                   * there.  We need to clear the buffer from the current
                   * offset to the end (there may be old gunk there).
                   */
                  while (offs < buf->dtb_size)
                        tomax[offs++] = 0;

                  /*
                   * We need to set our offset to zero.  And because we
                   * are wrapping, we need to set the bit indicating as
                   * much.  We can also adjust our needed space back
                   * down to the space required by the ECB -- we know
                   * that the top of the buffer is aligned.
                   */
                  offs = 0;
                  total = needed;
                  buf->dtb_flags |= DTRACEBUF_WRAPPED;
            } else {
                  /*
                   * There is room for us in the buffer, so we simply
                   * need to check the wrapped offset.
                   */
                  if (woffs < offs) {
                        /*
                         * The wrapped offset is less than the offset.
                         * This can happen if we allocated buffer space
                         * that induced a wrap, but then we didn't
                         * subsequently take the space due to an error
                         * or false predicate evaluation.  This is
                         * okay; we know that _this_ allocation isn't
                         * going to induce a wrap.  We still can't
                         * reset the wrapped offset to be zero,
                         * however: the space may have been trashed in
                         * the previous failed probe attempt.  But at
                         * least the wrapped offset doesn't need to
                         * be adjusted at all...
                         */
                        goto out;
                  }
            }

            while (offs + total > woffs) {
                  dtrace_epid_t epid = *(uint32_t *)(tomax + woffs);
                  size_t size;

                  if (epid == DTRACE_EPIDNONE) {
                        size = sizeof (uint32_t);
                  } else {
                        ASSERT(epid <= state->dts_necbs);
                        ASSERT(state->dts_ecbs[epid - 1] != NULL);

                        size = state->dts_ecbs[epid - 1]->dte_size;
                  }

                  ASSERT(woffs + size <= buf->dtb_size);
                  ASSERT(size != 0);

                  if (woffs + size == buf->dtb_size) {
                        /*
                         * We've reached the end of the buffer; we want
                         * to set the wrapped offset to 0 and break
                         * out.  However, if the offs is 0, then we're
                         * in a strange edge-condition:  the amount of
                         * space that we want to reserve plus the size
                         * of the record that we're overwriting is
                         * greater than the size of the buffer.  This
                         * is problematic because if we reserve the
                         * space but subsequently don't consume it (due
                         * to a failed predicate or error) the wrapped
                         * offset will be 0 -- yet the EPID at offset 0
                         * will not be committed.  This situation is
                         * relatively easy to deal with:  if we're in
                         * this case, the buffer is indistinguishable
                         * from one that hasn't wrapped; we need only
                         * finish the job by clearing the wrapped bit,
                         * explicitly setting the offset to be 0, and
                         * zero'ing out the old data in the buffer.
                         */
                        if (offs == 0) {
                              buf->dtb_flags &= ~DTRACEBUF_WRAPPED;
                              buf->dtb_offset = 0;
                              woffs = total;

                              while (woffs < buf->dtb_size)
                                    tomax[woffs++] = 0;
                        }

                        woffs = 0;
                        break;
                  }

                  woffs += size;
            }

            /*
             * We have a wrapped offset.  It may be that the wrapped offset
             * has become zero -- that's okay.
             */
            buf->dtb_xamot_offset = woffs;
      }

out:
      /*
       * Now we can plow the buffer with any necessary padding.
       */
      while (offs & (align - 1)) {
            /*
             * Assert that our alignment is off by a number which
             * is itself sizeof (uint32_t) aligned.
             */
            ASSERT(!((align - (offs & (align - 1))) &
                (sizeof (uint32_t) - 1)));
            DTRACE_STORE(uint32_t, tomax, offs, DTRACE_EPIDNONE);
            offs += sizeof (uint32_t);
      }

      if (buf->dtb_flags & DTRACEBUF_FILL) {
            if (offs + needed > buf->dtb_size - state->dts_reserve) {
                  buf->dtb_flags |= DTRACEBUF_FULL;
                  return (-1);
            }
      }

      if (mstate == NULL)
            return (offs);

      /*
       * For ring buffers and fill buffers, the scratch space is always
       * the inactive buffer.
       */
      mstate->dtms_scratch_base = (uintptr_t)buf->dtb_xamot;
      mstate->dtms_scratch_size = buf->dtb_size;
      mstate->dtms_scratch_ptr = mstate->dtms_scratch_base;

      return (offs);
}

static void
dtrace_buffer_polish(dtrace_buffer_t *buf)
{
      ASSERT(buf->dtb_flags & DTRACEBUF_RING);
      ASSERT(MUTEX_HELD(&dtrace_lock));

      if (!(buf->dtb_flags & DTRACEBUF_WRAPPED))
            return;

      /*
       * We need to polish the ring buffer.  There are three cases:
       *
       * - The first (and presumably most common) is that there is no gap
       *   between the buffer offset and the wrapped offset.  In this case,
       *   there is nothing in the buffer that isn't valid data; we can
       *   mark the buffer as polished and return.
       *
       * - The second (less common than the first but still more common
       *   than the third) is that there is a gap between the buffer offset
       *   and the wrapped offset, and the wrapped offset is larger than the
       *   buffer offset.  This can happen because of an alignment issue, or
       *   can happen because of a call to dtrace_buffer_reserve() that
       *   didn't subsequently consume the buffer space.  In this case,
       *   we need to zero the data from the buffer offset to the wrapped
       *   offset.
       *
       * - The third (and least common) is that there is a gap between the
       *   buffer offset and the wrapped offset, but the wrapped offset is
       *   _less_ than the buffer offset.  This can only happen because a
       *   call to dtrace_buffer_reserve() induced a wrap, but the space
       *   was not subsequently consumed.  In this case, we need to zero the
       *   space from the offset to the end of the buffer _and_ from the
       *   top of the buffer to the wrapped offset.
       */
      if (buf->dtb_offset < buf->dtb_xamot_offset) {
            bzero(buf->dtb_tomax + buf->dtb_offset,
                buf->dtb_xamot_offset - buf->dtb_offset);
      }

      if (buf->dtb_offset > buf->dtb_xamot_offset) {
            bzero(buf->dtb_tomax + buf->dtb_offset,
                buf->dtb_size - buf->dtb_offset);
            bzero(buf->dtb_tomax, buf->dtb_xamot_offset);
      }
}

static void
dtrace_buffer_free(dtrace_buffer_t *bufs)
{
      int i;

      for (i = 0; i < NCPU; i++) {
            dtrace_buffer_t *buf = &bufs[i];

            if (buf->dtb_tomax == NULL) {
                  ASSERT(buf->dtb_xamot == NULL);
                  ASSERT(buf->dtb_size == 0);
                  continue;
            }

            if (buf->dtb_xamot != NULL) {
                  ASSERT(!(buf->dtb_flags & DTRACEBUF_NOSWITCH));
                  kmem_free(buf->dtb_xamot, buf->dtb_size);
            }

            kmem_free(buf->dtb_tomax, buf->dtb_size);
            buf->dtb_size = 0;
            buf->dtb_tomax = NULL;
            buf->dtb_xamot = NULL;
      }
}

/*
 * DTrace Enabling Functions
 */
static dtrace_enabling_t *
dtrace_enabling_create(dtrace_vstate_t *vstate)
{
      dtrace_enabling_t *enab;

      enab = kmem_zalloc(sizeof (dtrace_enabling_t), KM_SLEEP);
      enab->dten_vstate = vstate;

      return (enab);
}

static void
dtrace_enabling_add(dtrace_enabling_t *enab, dtrace_ecbdesc_t *ecb)
{
      dtrace_ecbdesc_t **ndesc;
      size_t osize, nsize;

      /*
       * We can't add to enablings after we've enabled them, or after we've
       * retained them.
       */
      ASSERT(enab->dten_probegen == 0);
      ASSERT(enab->dten_next == NULL && enab->dten_prev == NULL);

      if (enab->dten_ndesc < enab->dten_maxdesc) {
            enab->dten_desc[enab->dten_ndesc++] = ecb;
            return;
      }

      osize = enab->dten_maxdesc * sizeof (dtrace_enabling_t *);

      if (enab->dten_maxdesc == 0) {
            enab->dten_maxdesc = 1;
      } else {
            enab->dten_maxdesc <<= 1;
      }

      ASSERT(enab->dten_ndesc < enab->dten_maxdesc);

      nsize = enab->dten_maxdesc * sizeof (dtrace_enabling_t *);
      ndesc = kmem_zalloc(nsize, KM_SLEEP);
      bcopy(enab->dten_desc, ndesc, osize);
      if (enab->dten_desc != NULL)
            kmem_free(enab->dten_desc, osize);

      enab->dten_desc = ndesc;
      enab->dten_desc[enab->dten_ndesc++] = ecb;
}

static void
dtrace_enabling_addlike(dtrace_enabling_t *enab, dtrace_ecbdesc_t *ecb,
    dtrace_probedesc_t *pd)
{
      dtrace_ecbdesc_t *new;
      dtrace_predicate_t *pred;
      dtrace_actdesc_t *act;

      /*
       * We're going to create a new ECB description that matches the
       * specified ECB in every way, but has the specified probe description.
       */
      new = kmem_zalloc(sizeof (dtrace_ecbdesc_t), KM_SLEEP);

      if ((pred = ecb->dted_pred.dtpdd_predicate) != NULL)
            dtrace_predicate_hold(pred);

      for (act = ecb->dted_action; act != NULL; act = act->dtad_next)
            dtrace_actdesc_hold(act);

      new->dted_action = ecb->dted_action;
      new->dted_pred = ecb->dted_pred;
      new->dted_probe = *pd;
      new->dted_uarg = ecb->dted_uarg;

      dtrace_enabling_add(enab, new);
}

static void
dtrace_enabling_dump(dtrace_enabling_t *enab)
{
      int i;

      for (i = 0; i < enab->dten_ndesc; i++) {
            dtrace_probedesc_t *desc = &enab->dten_desc[i]->dted_probe;

            cmn_err(CE_NOTE, "enabling probe %d (%s:%s:%s:%s)", i,
                desc->dtpd_provider, desc->dtpd_mod,
                desc->dtpd_func, desc->dtpd_name);
      }
}

static void
dtrace_enabling_destroy(dtrace_enabling_t *enab)
{
      int i;
      dtrace_ecbdesc_t *ep;
      dtrace_vstate_t *vstate = enab->dten_vstate;

      ASSERT(MUTEX_HELD(&dtrace_lock));

      for (i = 0; i < enab->dten_ndesc; i++) {
            dtrace_actdesc_t *act, *next;
            dtrace_predicate_t *pred;

            ep = enab->dten_desc[i];

            if ((pred = ep->dted_pred.dtpdd_predicate) != NULL)
                  dtrace_predicate_release(pred, vstate);

            for (act = ep->dted_action; act != NULL; act = next) {
                  next = act->dtad_next;
                  dtrace_actdesc_release(act, vstate);
            }

            kmem_free(ep, sizeof (dtrace_ecbdesc_t));
      }

      if (enab->dten_desc != NULL)
            kmem_free(enab->dten_desc,
                enab->dten_maxdesc * sizeof (dtrace_enabling_t *));

      /*
       * If this was a retained enabling, decrement the dts_nretained count
       * and take it off of the dtrace_retained list.
       */
      if (enab->dten_prev != NULL || enab->dten_next != NULL ||
          dtrace_retained == enab) {
            ASSERT(enab->dten_vstate->dtvs_state != NULL);
            ASSERT(enab->dten_vstate->dtvs_state->dts_nretained > 0);
            enab->dten_vstate->dtvs_state->dts_nretained--;
      }

      if (enab->dten_prev == NULL) {
            if (dtrace_retained == enab) {
                  dtrace_retained = enab->dten_next;

                  if (dtrace_retained != NULL)
                        dtrace_retained->dten_prev = NULL;
            }
      } else {
            ASSERT(enab != dtrace_retained);
            ASSERT(dtrace_retained != NULL);
            enab->dten_prev->dten_next = enab->dten_next;
      }

      if (enab->dten_next != NULL) {
            ASSERT(dtrace_retained != NULL);
            enab->dten_next->dten_prev = enab->dten_prev;
      }

      kmem_free(enab, sizeof (dtrace_enabling_t));
}

static int
dtrace_enabling_retain(dtrace_enabling_t *enab)
{
      dtrace_state_t *state;

      ASSERT(MUTEX_HELD(&dtrace_lock));
      ASSERT(enab->dten_next == NULL && enab->dten_prev == NULL);
      ASSERT(enab->dten_vstate != NULL);

      state = enab->dten_vstate->dtvs_state;
      ASSERT(state != NULL);

      /*
       * We only allow each state to retain dtrace_retain_max enablings.
       */
      if (state->dts_nretained >= dtrace_retain_max)
            return (ENOSPC);

      state->dts_nretained++;

      if (dtrace_retained == NULL) {
            dtrace_retained = enab;
            return (0);
      }

      enab->dten_next = dtrace_retained;
      dtrace_retained->dten_prev = enab;
      dtrace_retained = enab;

      return (0);
}

static int
dtrace_enabling_replicate(dtrace_state_t *state, dtrace_probedesc_t *match,
    dtrace_probedesc_t *create)
{
      dtrace_enabling_t *new, *enab;
      int found = 0, err = ENOENT;

      ASSERT(MUTEX_HELD(&dtrace_lock));
      ASSERT(strlen(match->dtpd_provider) < DTRACE_PROVNAMELEN);
      ASSERT(strlen(match->dtpd_mod) < DTRACE_MODNAMELEN);
      ASSERT(strlen(match->dtpd_func) < DTRACE_FUNCNAMELEN);
      ASSERT(strlen(match->dtpd_name) < DTRACE_NAMELEN);

      new = dtrace_enabling_create(&state->dts_vstate);

      /*
       * Iterate over all retained enablings, looking for enablings that
       * match the specified state.
       */
      for (enab = dtrace_retained; enab != NULL; enab = enab->dten_next) {
            int i;

            /*
             * dtvs_state can only be NULL for helper enablings -- and
             * helper enablings can't be retained.
             */
            ASSERT(enab->dten_vstate->dtvs_state != NULL);

            if (enab->dten_vstate->dtvs_state != state)
                  continue;

            /*
             * Now iterate over each probe description; we're looking for
             * an exact match to the specified probe description.
             */
            for (i = 0; i < enab->dten_ndesc; i++) {
                  dtrace_ecbdesc_t *ep = enab->dten_desc[i];
                  dtrace_probedesc_t *pd = &ep->dted_probe;

                  if (strcmp(pd->dtpd_provider, match->dtpd_provider))
                        continue;

                  if (strcmp(pd->dtpd_mod, match->dtpd_mod))
                        continue;

                  if (strcmp(pd->dtpd_func, match->dtpd_func))
                        continue;

                  if (strcmp(pd->dtpd_name, match->dtpd_name))
                        continue;

                  /*
                   * We have a winning probe!  Add it to our growing
                   * enabling.
                   */
                  found = 1;
                  dtrace_enabling_addlike(new, ep, create);
            }
      }

      if (!found || (err = dtrace_enabling_retain(new)) != 0) {
            dtrace_enabling_destroy(new);
            return (err);
      }

      return (0);
}

static void
dtrace_enabling_retract(dtrace_state_t *state)
{
      dtrace_enabling_t *enab, *next;

      ASSERT(MUTEX_HELD(&dtrace_lock));

      /*
       * Iterate over all retained enablings, destroy the enablings retained
       * for the specified state.
       */
      for (enab = dtrace_retained; enab != NULL; enab = next) {
            next = enab->dten_next;

            /*
             * dtvs_state can only be NULL for helper enablings -- and
             * helper enablings can't be retained.
             */
            ASSERT(enab->dten_vstate->dtvs_state != NULL);

            if (enab->dten_vstate->dtvs_state == state) {
                  ASSERT(state->dts_nretained > 0);
                  dtrace_enabling_destroy(enab);
            }
      }

      ASSERT(state->dts_nretained == 0);
}

static int
dtrace_enabling_match(dtrace_enabling_t *enab, int *nmatched)
{
      int i = 0;
      int matched = 0;

      ASSERT(MUTEX_HELD(&cpu_lock));
      ASSERT(MUTEX_HELD(&dtrace_lock));

      for (i = 0; i < enab->dten_ndesc; i++) {
            dtrace_ecbdesc_t *ep = enab->dten_desc[i];

            enab->dten_current = ep;
            enab->dten_error = 0;

            matched += dtrace_probe_enable(&ep->dted_probe, enab);

            if (enab->dten_error != 0) {
                  /*
                   * If we get an error half-way through enabling the
                   * probes, we kick out -- perhaps with some number of
                   * them enabled.  Leaving enabled probes enabled may
                   * be slightly confusing for user-level, but we expect
                   * that no one will attempt to actually drive on in
                   * the face of such errors.  If this is an anonymous
                   * enabling (indicated with a NULL nmatched pointer),
                   * we cmn_err() a message.  We aren't expecting to
                   * get such an error -- such as it can exist at all,
                   * it would be a result of corrupted DOF in the driver
                   * properties.
                   */
                  if (nmatched == NULL) {
                        cmn_err(CE_WARN, "dtrace_enabling_match() "
                            "error on %p: %d", (void *)ep,
                            enab->dten_error);
                  }

                  return (enab->dten_error);
            }
      }

      enab->dten_probegen = dtrace_probegen;
      if (nmatched != NULL)
            *nmatched = matched;

      return (0);
}

static void
dtrace_enabling_matchall(void)
{
      dtrace_enabling_t *enab;

      mutex_enter(&cpu_lock);
      mutex_enter(&dtrace_lock);

      /*
       * Iterate over all retained enablings to see if any probes match
       * against them.  We only perform this operation on enablings for which
       * we have sufficient permissions by virtue of being in the global zone
       * or in the same zone as the DTrace client.  Because we can be called
       * after dtrace_detach() has been called, we cannot assert that there
       * are retained enablings.  We can safely load from dtrace_retained,
       * however:  the taskq_destroy() at the end of dtrace_detach() will
       * block pending our completion.
       */
      for (enab = dtrace_retained; enab != NULL; enab = enab->dten_next) {
#if defined(sun)
            cred_t *cr = enab->dten_vstate->dtvs_state->dts_cred.dcr_cred;

            if (INGLOBALZONE(curproc) || getzoneid() == crgetzoneid(cr))
#endif
                  (void) dtrace_enabling_match(enab, NULL);
      }

      mutex_exit(&dtrace_lock);
      mutex_exit(&cpu_lock);
}

/*
 * If an enabling is to be enabled without having matched probes (that is, if
 * dtrace_state_go() is to be called on the underlying dtrace_state_t), the
 * enabling must be _primed_ by creating an ECB for every ECB description.
 * This must be done to assure that we know the number of speculations, the
 * number of aggregations, the minimum buffer size needed, etc. before we
 * transition out of DTRACE_ACTIVITY_INACTIVE.  To do this without actually
 * enabling any probes, we create ECBs for every ECB decription, but with a
 * NULL probe -- which is exactly what this function does.
 */
static void
dtrace_enabling_prime(dtrace_state_t *state)
{
      dtrace_enabling_t *enab;
      int i;

      for (enab = dtrace_retained; enab != NULL; enab = enab->dten_next) {
            ASSERT(enab->dten_vstate->dtvs_state != NULL);

            if (enab->dten_vstate->dtvs_state != state)
                  continue;

            /*
             * We don't want to prime an enabling more than once, lest
             * we allow a malicious user to induce resource exhaustion.
             * (The ECBs that result from priming an enabling aren't
             * leaked -- but they also aren't deallocated until the
             * consumer state is destroyed.)
             */
            if (enab->dten_primed)
                  continue;

            for (i = 0; i < enab->dten_ndesc; i++) {
                  enab->dten_current = enab->dten_desc[i];
                  (void) dtrace_probe_enable(NULL, enab);
            }

            enab->dten_primed = 1;
      }
}

/*
 * Called to indicate that probes should be provided due to retained
 * enablings.  This is implemented in terms of dtrace_probe_provide(), but it
 * must take an initial lap through the enabling calling the dtps_provide()
 * entry point explicitly to allow for autocreated probes.
 */
static void
dtrace_enabling_provide(dtrace_provider_t *prv)
{
      int i, all = 0;
      dtrace_probedesc_t desc;

      ASSERT(MUTEX_HELD(&dtrace_lock));
      ASSERT(MUTEX_HELD(&dtrace_provider_lock));

      if (prv == NULL) {
            all = 1;
            prv = dtrace_provider;
      }

      do {
            dtrace_enabling_t *enab = dtrace_retained;
            void *parg = prv->dtpv_arg;

            for (; enab != NULL; enab = enab->dten_next) {
                  for (i = 0; i < enab->dten_ndesc; i++) {
                        desc = enab->dten_desc[i]->dted_probe;
                        mutex_exit(&dtrace_lock);
                        prv->dtpv_pops.dtps_provide(parg, &desc);
                        mutex_enter(&dtrace_lock);
                  }
            }
      } while (all && (prv = prv->dtpv_next) != NULL);

      mutex_exit(&dtrace_lock);
      dtrace_probe_provide(NULL, all ? NULL : prv);
      mutex_enter(&dtrace_lock);
}

/*
 * DTrace DOF Functions
 */
/*ARGSUSED*/
static void
dtrace_dof_error(dof_hdr_t *dof, const char *str)
{
      if (dtrace_err_verbose)
            cmn_err(CE_WARN, "failed to process DOF: %s", str);

#ifdef DTRACE_ERRDEBUG
      dtrace_errdebug(str);
#endif
}

/*
 * Create DOF out of a currently enabled state.  Right now, we only create
 * DOF containing the run-time options -- but this could be expanded to create
 * complete DOF representing the enabled state.
 */
static dof_hdr_t *
dtrace_dof_create(dtrace_state_t *state)
{
      dof_hdr_t *dof;
      dof_sec_t *sec;
      dof_optdesc_t *opt;
      int i, len = sizeof (dof_hdr_t) +
          roundup(sizeof (dof_sec_t), sizeof (uint64_t)) +
          sizeof (dof_optdesc_t) * DTRACEOPT_MAX;

      ASSERT(MUTEX_HELD(&dtrace_lock));

      dof = kmem_zalloc(len, KM_SLEEP);
      dof->dofh_ident[DOF_ID_MAG0] = DOF_MAG_MAG0;
      dof->dofh_ident[DOF_ID_MAG1] = DOF_MAG_MAG1;
      dof->dofh_ident[DOF_ID_MAG2] = DOF_MAG_MAG2;
      dof->dofh_ident[DOF_ID_MAG3] = DOF_MAG_MAG3;

      dof->dofh_ident[DOF_ID_MODEL] = DOF_MODEL_NATIVE;
      dof->dofh_ident[DOF_ID_ENCODING] = DOF_ENCODE_NATIVE;
      dof->dofh_ident[DOF_ID_VERSION] = DOF_VERSION;
      dof->dofh_ident[DOF_ID_DIFVERS] = DIF_VERSION;
      dof->dofh_ident[DOF_ID_DIFIREG] = DIF_DIR_NREGS;
      dof->dofh_ident[DOF_ID_DIFTREG] = DIF_DTR_NREGS;

      dof->dofh_flags = 0;
      dof->dofh_hdrsize = sizeof (dof_hdr_t);
      dof->dofh_secsize = sizeof (dof_sec_t);
      dof->dofh_secnum = 1;   /* only DOF_SECT_OPTDESC */
      dof->dofh_secoff = sizeof (dof_hdr_t);
      dof->dofh_loadsz = len;
      dof->dofh_filesz = len;
      dof->dofh_pad = 0;

      /*
       * Fill in the option section header...
       */
      sec = (dof_sec_t *)((uintptr_t)dof + sizeof (dof_hdr_t));
      sec->dofs_type = DOF_SECT_OPTDESC;
      sec->dofs_align = sizeof (uint64_t);
      sec->dofs_flags = DOF_SECF_LOAD;
      sec->dofs_entsize = sizeof (dof_optdesc_t);

      opt = (dof_optdesc_t *)((uintptr_t)sec +
          roundup(sizeof (dof_sec_t), sizeof (uint64_t)));

      sec->dofs_offset = (uintptr_t)opt - (uintptr_t)dof;
      sec->dofs_size = sizeof (dof_optdesc_t) * DTRACEOPT_MAX;

      for (i = 0; i < DTRACEOPT_MAX; i++) {
            opt[i].dofo_option = i;
            opt[i].dofo_strtab = DOF_SECIDX_NONE;
            opt[i].dofo_value = state->dts_options[i];
      }

      return (dof);
}

static dof_hdr_t *
dtrace_dof_copyin(uintptr_t uarg, int *errp)
{
      dof_hdr_t hdr, *dof;

      ASSERT(!MUTEX_HELD(&dtrace_lock));

      /*
       * First, we're going to copyin() the sizeof (dof_hdr_t).
       */
      if (copyin((void *)uarg, &hdr, sizeof (hdr)) != 0) {
            dtrace_dof_error(NULL, "failed to copyin DOF header");
            *errp = EFAULT;
            return (NULL);
      }

      /*
       * Now we'll allocate the entire DOF and copy it in -- provided
       * that the length isn't outrageous.
       */
      if (hdr.dofh_loadsz >= dtrace_dof_maxsize) {
            dtrace_dof_error(&hdr, "load size exceeds maximum");
            *errp = E2BIG;
            return (NULL);
      }

      if (hdr.dofh_loadsz < sizeof (hdr)) {
            dtrace_dof_error(&hdr, "invalid load size");
            *errp = EINVAL;
            return (NULL);
      }

      dof = kmem_alloc(hdr.dofh_loadsz, KM_SLEEP);

      if (copyin((void *)uarg, dof, hdr.dofh_loadsz) != 0) {
            kmem_free(dof, hdr.dofh_loadsz);
            *errp = EFAULT;
            return (NULL);
      }

      return (dof);
}

#if !defined(sun)
static __inline uchar_t
dtrace_dof_char(char c) {
      switch (c) {
      case '0':
      case '1':
      case '2':
      case '3':
      case '4':
      case '5':
      case '6':
      case '7':
      case '8':
      case '9':
            return (c - '0');
      case 'A':
      case 'B':
      case 'C':
      case 'D':
      case 'E':
      case 'F':
            return (c - 'A' + 10);
      case 'a':
      case 'b':
      case 'c':
      case 'd':
      case 'e':
      case 'f':
            return (c - 'a' + 10);
      }
      /* Should not reach here. */
      return (0);
}
#endif

static dof_hdr_t *
dtrace_dof_property(const char *name)
{
      uchar_t *buf;
      uint64_t loadsz;
      unsigned int len, i;
      dof_hdr_t *dof;

#if defined(sun)
      /*
       * Unfortunately, array of values in .conf files are always (and
       * only) interpreted to be integer arrays.  We must read our DOF
       * as an integer array, and then squeeze it into a byte array.
       */
      if (ddi_prop_lookup_int_array(DDI_DEV_T_ANY, dtrace_devi, 0,
          (char *)name, (int **)&buf, &len) != DDI_PROP_SUCCESS)
            return (NULL);

      for (i = 0; i < len; i++)
            buf[i] = (uchar_t)(((int *)buf)[i]);

      if (len < sizeof (dof_hdr_t)) {
            ddi_prop_free(buf);
            dtrace_dof_error(NULL, "truncated header");
            return (NULL);
      }

      if (len < (loadsz = ((dof_hdr_t *)buf)->dofh_loadsz)) {
            ddi_prop_free(buf);
            dtrace_dof_error(NULL, "truncated DOF");
            return (NULL);
      }

      if (loadsz >= dtrace_dof_maxsize) {
            ddi_prop_free(buf);
            dtrace_dof_error(NULL, "oversized DOF");
            return (NULL);
      }

      dof = kmem_alloc(loadsz, KM_SLEEP);
      bcopy(buf, dof, loadsz);
      ddi_prop_free(buf);
#else
      char *p;
      char *p_env;

      if ((p_env = getenv(name)) == NULL)
            return (NULL);

      len = strlen(p_env) / 2;

      buf = kmem_alloc(len, KM_SLEEP);

      dof = (dof_hdr_t *) buf;

      p = p_env;

      for (i = 0; i < len; i++) {
            buf[i] = (dtrace_dof_char(p[0]) << 4) |
                 dtrace_dof_char(p[1]);
            p += 2;
      }

      freeenv(p_env);

      if (len < sizeof (dof_hdr_t)) {
            kmem_free(buf, 0);
            dtrace_dof_error(NULL, "truncated header");
            return (NULL);
      }

      if (len < (loadsz = dof->dofh_loadsz)) {
            kmem_free(buf, 0);
            dtrace_dof_error(NULL, "truncated DOF");
            return (NULL);
      }

      if (loadsz >= dtrace_dof_maxsize) {
            kmem_free(buf, 0);
            dtrace_dof_error(NULL, "oversized DOF");
            return (NULL);
      }
#endif

      return (dof);
}

static void
dtrace_dof_destroy(dof_hdr_t *dof)
{
      kmem_free(dof, dof->dofh_loadsz);
}

/*
 * Return the dof_sec_t pointer corresponding to a given section index.  If the
 * index is not valid, dtrace_dof_error() is called and NULL is returned.  If
 * a type other than DOF_SECT_NONE is specified, the header is checked against
 * this type and NULL is returned if the types do not match.
 */
static dof_sec_t *
dtrace_dof_sect(dof_hdr_t *dof, uint32_t type, dof_secidx_t i)
{
      dof_sec_t *sec = (dof_sec_t *)(uintptr_t)
          ((uintptr_t)dof + dof->dofh_secoff + i * dof->dofh_secsize);

      if (i >= dof->dofh_secnum) {
            dtrace_dof_error(dof, "referenced section index is invalid");
            return (NULL);
      }

      if (!(sec->dofs_flags & DOF_SECF_LOAD)) {
            dtrace_dof_error(dof, "referenced section is not loadable");
            return (NULL);
      }

      if (type != DOF_SECT_NONE && type != sec->dofs_type) {
            dtrace_dof_error(dof, "referenced section is the wrong type");
            return (NULL);
      }

      return (sec);
}

static dtrace_probedesc_t *
dtrace_dof_probedesc(dof_hdr_t *dof, dof_sec_t *sec, dtrace_probedesc_t *desc)
{
      dof_probedesc_t *probe;
      dof_sec_t *strtab;
      uintptr_t daddr = (uintptr_t)dof;
      uintptr_t str;
      size_t size;

      if (sec->dofs_type != DOF_SECT_PROBEDESC) {
            dtrace_dof_error(dof, "invalid probe section");
            return (NULL);
      }

      if (sec->dofs_align != sizeof (dof_secidx_t)) {
            dtrace_dof_error(dof, "bad alignment in probe description");
            return (NULL);
      }

      if (sec->dofs_offset + sizeof (dof_probedesc_t) > dof->dofh_loadsz) {
            dtrace_dof_error(dof, "truncated probe description");
            return (NULL);
      }

      probe = (dof_probedesc_t *)(uintptr_t)(daddr + sec->dofs_offset);
      strtab = dtrace_dof_sect(dof, DOF_SECT_STRTAB, probe->dofp_strtab);

      if (strtab == NULL)
            return (NULL);

      str = daddr + strtab->dofs_offset;
      size = strtab->dofs_size;

      if (probe->dofp_provider >= strtab->dofs_size) {
            dtrace_dof_error(dof, "corrupt probe provider");
            return (NULL);
      }

      (void) strncpy(desc->dtpd_provider,
          (char *)(str + probe->dofp_provider),
          MIN(DTRACE_PROVNAMELEN - 1, size - probe->dofp_provider));

      if (probe->dofp_mod >= strtab->dofs_size) {
            dtrace_dof_error(dof, "corrupt probe module");
            return (NULL);
      }

      (void) strncpy(desc->dtpd_mod, (char *)(str + probe->dofp_mod),
          MIN(DTRACE_MODNAMELEN - 1, size - probe->dofp_mod));

      if (probe->dofp_func >= strtab->dofs_size) {
            dtrace_dof_error(dof, "corrupt probe function");
            return (NULL);
      }

      (void) strncpy(desc->dtpd_func, (char *)(str + probe->dofp_func),
          MIN(DTRACE_FUNCNAMELEN - 1, size - probe->dofp_func));

      if (probe->dofp_name >= strtab->dofs_size) {
            dtrace_dof_error(dof, "corrupt probe name");
            return (NULL);
      }

      (void) strncpy(desc->dtpd_name, (char *)(str + probe->dofp_name),
          MIN(DTRACE_NAMELEN - 1, size - probe->dofp_name));

      return (desc);
}

static dtrace_difo_t *
dtrace_dof_difo(dof_hdr_t *dof, dof_sec_t *sec, dtrace_vstate_t *vstate,
    cred_t *cr)
{
      dtrace_difo_t *dp;
      size_t ttl = 0;
      dof_difohdr_t *dofd;
      uintptr_t daddr = (uintptr_t)dof;
      size_t max = dtrace_difo_maxsize;
      int i, l, n;

      static const struct {
            int section;
            int bufoffs;
            int lenoffs;
            int entsize;
            int align;
            const char *msg;
      } difo[] = {
            { DOF_SECT_DIF, offsetof(dtrace_difo_t, dtdo_buf),
            offsetof(dtrace_difo_t, dtdo_len), sizeof (dif_instr_t),
            sizeof (dif_instr_t), "multiple DIF sections" },

            { DOF_SECT_INTTAB, offsetof(dtrace_difo_t, dtdo_inttab),
            offsetof(dtrace_difo_t, dtdo_intlen), sizeof (uint64_t),
            sizeof (uint64_t), "multiple integer tables" },

            { DOF_SECT_STRTAB, offsetof(dtrace_difo_t, dtdo_strtab),
            offsetof(dtrace_difo_t, dtdo_strlen), 0,
            sizeof (char), "multiple string tables" },

            { DOF_SECT_VARTAB, offsetof(dtrace_difo_t, dtdo_vartab),
            offsetof(dtrace_difo_t, dtdo_varlen), sizeof (dtrace_difv_t),
            sizeof (uint_t), "multiple variable tables" },

            { DOF_SECT_NONE, 0, 0, 0, 0, NULL }
      };

      if (sec->dofs_type != DOF_SECT_DIFOHDR) {
            dtrace_dof_error(dof, "invalid DIFO header section");
            return (NULL);
      }

      if (sec->dofs_align != sizeof (dof_secidx_t)) {
            dtrace_dof_error(dof, "bad alignment in DIFO header");
            return (NULL);
      }

      if (sec->dofs_size < sizeof (dof_difohdr_t) ||
          sec->dofs_size % sizeof (dof_secidx_t)) {
            dtrace_dof_error(dof, "bad size in DIFO header");
            return (NULL);
      }

      dofd = (dof_difohdr_t *)(uintptr_t)(daddr + sec->dofs_offset);
      n = (sec->dofs_size - sizeof (*dofd)) / sizeof (dof_secidx_t) + 1;

      dp = kmem_zalloc(sizeof (dtrace_difo_t), KM_SLEEP);
      dp->dtdo_rtype = dofd->dofd_rtype;

      for (l = 0; l < n; l++) {
            dof_sec_t *subsec;
            void **bufp;
            uint32_t *lenp;

            if ((subsec = dtrace_dof_sect(dof, DOF_SECT_NONE,
                dofd->dofd_links[l])) == NULL)
                  goto err; /* invalid section link */

            if (ttl + subsec->dofs_size > max) {
                  dtrace_dof_error(dof, "exceeds maximum size");
                  goto err;
            }

            ttl += subsec->dofs_size;

            for (i = 0; difo[i].section != DOF_SECT_NONE; i++) {
                  if (subsec->dofs_type != difo[i].section)
                        continue;

                  if (!(subsec->dofs_flags & DOF_SECF_LOAD)) {
                        dtrace_dof_error(dof, "section not loaded");
                        goto err;
                  }

                  if (subsec->dofs_align != difo[i].align) {
                        dtrace_dof_error(dof, "bad alignment");
                        goto err;
                  }

                  bufp = (void **)((uintptr_t)dp + difo[i].bufoffs);
                  lenp = (uint32_t *)((uintptr_t)dp + difo[i].lenoffs);

                  if (*bufp != NULL) {
                        dtrace_dof_error(dof, difo[i].msg);
                        goto err;
                  }

                  if (difo[i].entsize != subsec->dofs_entsize) {
                        dtrace_dof_error(dof, "entry size mismatch");
                        goto err;
                  }

                  if (subsec->dofs_entsize != 0 &&
                      (subsec->dofs_size % subsec->dofs_entsize) != 0) {
                        dtrace_dof_error(dof, "corrupt entry size");
                        goto err;
                  }

                  *lenp = subsec->dofs_size;
                  *bufp = kmem_alloc(subsec->dofs_size, KM_SLEEP);
                  bcopy((char *)(uintptr_t)(daddr + subsec->dofs_offset),
                      *bufp, subsec->dofs_size);

                  if (subsec->dofs_entsize != 0)
                        *lenp /= subsec->dofs_entsize;

                  break;
            }

            /*
             * If we encounter a loadable DIFO sub-section that is not
             * known to us, assume this is a broken program and fail.
             */
            if (difo[i].section == DOF_SECT_NONE &&
                (subsec->dofs_flags & DOF_SECF_LOAD)) {
                  dtrace_dof_error(dof, "unrecognized DIFO subsection");
                  goto err;
            }
      }

      if (dp->dtdo_buf == NULL) {
            /*
             * We can't have a DIF object without DIF text.
             */
            dtrace_dof_error(dof, "missing DIF text");
            goto err;
      }

      /*
       * Before we validate the DIF object, run through the variable table
       * looking for the strings -- if any of their size are under, we'll set
       * their size to be the system-wide default string size.  Note that
       * this should _not_ happen if the "strsize" option has been set --
       * in this case, the compiler should have set the size to reflect the
       * setting of the option.
       */
      for (i = 0; i < dp->dtdo_varlen; i++) {
            dtrace_difv_t *v = &dp->dtdo_vartab[i];
            dtrace_diftype_t *t = &v->dtdv_type;

            if (v->dtdv_id < DIF_VAR_OTHER_UBASE)
                  continue;

            if (t->dtdt_kind == DIF_TYPE_STRING && t->dtdt_size == 0)
                  t->dtdt_size = dtrace_strsize_default;
      }

      if (dtrace_difo_validate(dp, vstate, DIF_DIR_NREGS, cr) != 0)
            goto err;

      dtrace_difo_init(dp, vstate);
      return (dp);

err:
      kmem_free(dp->dtdo_buf, dp->dtdo_len * sizeof (dif_instr_t));
      kmem_free(dp->dtdo_inttab, dp->dtdo_intlen * sizeof (uint64_t));
      kmem_free(dp->dtdo_strtab, dp->dtdo_strlen);
      kmem_free(dp->dtdo_vartab, dp->dtdo_varlen * sizeof (dtrace_difv_t));

      kmem_free(dp, sizeof (dtrace_difo_t));
      return (NULL);
}

static dtrace_predicate_t *
dtrace_dof_predicate(dof_hdr_t *dof, dof_sec_t *sec, dtrace_vstate_t *vstate,
    cred_t *cr)
{
      dtrace_difo_t *dp;

      if ((dp = dtrace_dof_difo(dof, sec, vstate, cr)) == NULL)
            return (NULL);

      return (dtrace_predicate_create(dp));
}

static dtrace_actdesc_t *
dtrace_dof_actdesc(dof_hdr_t *dof, dof_sec_t *sec, dtrace_vstate_t *vstate,
    cred_t *cr)
{
      dtrace_actdesc_t *act, *first = NULL, *last = NULL, *next;
      dof_actdesc_t *desc;
      dof_sec_t *difosec;
      size_t offs;
      uintptr_t daddr = (uintptr_t)dof;
      uint64_t arg;
      dtrace_actkind_t kind;

      if (sec->dofs_type != DOF_SECT_ACTDESC) {
            dtrace_dof_error(dof, "invalid action section");
            return (NULL);
      }

      if (sec->dofs_offset + sizeof (dof_actdesc_t) > dof->dofh_loadsz) {
            dtrace_dof_error(dof, "truncated action description");
            return (NULL);
      }

      if (sec->dofs_align != sizeof (uint64_t)) {
            dtrace_dof_error(dof, "bad alignment in action description");
            return (NULL);
      }

      if (sec->dofs_size < sec->dofs_entsize) {
            dtrace_dof_error(dof, "section entry size exceeds total size");
            return (NULL);
      }

      if (sec->dofs_entsize != sizeof (dof_actdesc_t)) {
            dtrace_dof_error(dof, "bad entry size in action description");
            return (NULL);
      }

      if (sec->dofs_size / sec->dofs_entsize > dtrace_actions_max) {
            dtrace_dof_error(dof, "actions exceed dtrace_actions_max");
            return (NULL);
      }

      for (offs = 0; offs < sec->dofs_size; offs += sec->dofs_entsize) {
            desc = (dof_actdesc_t *)(daddr +
                (uintptr_t)sec->dofs_offset + offs);
            kind = (dtrace_actkind_t)desc->dofa_kind;

            if (DTRACEACT_ISPRINTFLIKE(kind) &&
                (kind != DTRACEACT_PRINTA ||
                desc->dofa_strtab != DOF_SECIDX_NONE)) {
                  dof_sec_t *strtab;
                  char *str, *fmt;
                  uint64_t i;

                  /*
                   * printf()-like actions must have a format string.
                   */
                  if ((strtab = dtrace_dof_sect(dof,
                      DOF_SECT_STRTAB, desc->dofa_strtab)) == NULL)
                        goto err;

                  str = (char *)((uintptr_t)dof +
                      (uintptr_t)strtab->dofs_offset);

                  for (i = desc->dofa_arg; i < strtab->dofs_size; i++) {
                        if (str[i] == '\0')
                              break;
                  }

                  if (i >= strtab->dofs_size) {
                        dtrace_dof_error(dof, "bogus format string");
                        goto err;
                  }

                  if (i == desc->dofa_arg) {
                        dtrace_dof_error(dof, "empty format string");
                        goto err;
                  }

                  i -= desc->dofa_arg;
                  fmt = kmem_alloc(i + 1, KM_SLEEP);
                  bcopy(&str[desc->dofa_arg], fmt, i + 1);
                  arg = (uint64_t)(uintptr_t)fmt;
            } else {
                  if (kind == DTRACEACT_PRINTA) {
                        ASSERT(desc->dofa_strtab == DOF_SECIDX_NONE);
                        arg = 0;
                  } else {
                        arg = desc->dofa_arg;
                  }
            }

            act = dtrace_actdesc_create(kind, desc->dofa_ntuple,
                desc->dofa_uarg, arg);

            if (last != NULL) {
                  last->dtad_next = act;
            } else {
                  first = act;
            }

            last = act;

            if (desc->dofa_difo == DOF_SECIDX_NONE)
                  continue;

            if ((difosec = dtrace_dof_sect(dof,
                DOF_SECT_DIFOHDR, desc->dofa_difo)) == NULL)
                  goto err;

            act->dtad_difo = dtrace_dof_difo(dof, difosec, vstate, cr);

            if (act->dtad_difo == NULL)
                  goto err;
      }

      ASSERT(first != NULL);
      return (first);

err:
      for (act = first; act != NULL; act = next) {
            next = act->dtad_next;
            dtrace_actdesc_release(act, vstate);
      }

      return (NULL);
}

static dtrace_ecbdesc_t *
dtrace_dof_ecbdesc(dof_hdr_t *dof, dof_sec_t *sec, dtrace_vstate_t *vstate,
    cred_t *cr)
{
      dtrace_ecbdesc_t *ep;
      dof_ecbdesc_t *ecb;
      dtrace_probedesc_t *desc;
      dtrace_predicate_t *pred = NULL;

      if (sec->dofs_size < sizeof (dof_ecbdesc_t)) {
            dtrace_dof_error(dof, "truncated ECB description");
            return (NULL);
      }

      if (sec->dofs_align != sizeof (uint64_t)) {
            dtrace_dof_error(dof, "bad alignment in ECB description");
            return (NULL);
      }

      ecb = (dof_ecbdesc_t *)((uintptr_t)dof + (uintptr_t)sec->dofs_offset);
      sec = dtrace_dof_sect(dof, DOF_SECT_PROBEDESC, ecb->dofe_probes);

      if (sec == NULL)
            return (NULL);

      ep = kmem_zalloc(sizeof (dtrace_ecbdesc_t), KM_SLEEP);
      ep->dted_uarg = ecb->dofe_uarg;
      desc = &ep->dted_probe;

      if (dtrace_dof_probedesc(dof, sec, desc) == NULL)
            goto err;

      if (ecb->dofe_pred != DOF_SECIDX_NONE) {
            if ((sec = dtrace_dof_sect(dof,
                DOF_SECT_DIFOHDR, ecb->dofe_pred)) == NULL)
                  goto err;

            if ((pred = dtrace_dof_predicate(dof, sec, vstate, cr)) == NULL)
                  goto err;

            ep->dted_pred.dtpdd_predicate = pred;
      }

      if (ecb->dofe_actions != DOF_SECIDX_NONE) {
            if ((sec = dtrace_dof_sect(dof,
                DOF_SECT_ACTDESC, ecb->dofe_actions)) == NULL)
                  goto err;

            ep->dted_action = dtrace_dof_actdesc(dof, sec, vstate, cr);

            if (ep->dted_action == NULL)
                  goto err;
      }

      return (ep);

err:
      if (pred != NULL)
            dtrace_predicate_release(pred, vstate);
      kmem_free(ep, sizeof (dtrace_ecbdesc_t));
      return (NULL);
}

/*
 * Apply the relocations from the specified 'sec' (a DOF_SECT_URELHDR) to the
 * specified DOF.  At present, this amounts to simply adding 'ubase' to the
 * site of any user SETX relocations to account for load object base address.
 * In the future, if we need other relocations, this function can be extended.
 */
static int
dtrace_dof_relocate(dof_hdr_t *dof, dof_sec_t *sec, uint64_t ubase)
{
      uintptr_t daddr = (uintptr_t)dof;
      dof_relohdr_t *dofr =
          (dof_relohdr_t *)(uintptr_t)(daddr + sec->dofs_offset);
      dof_sec_t *ss, *rs, *ts;
      dof_relodesc_t *r;
      uint_t i, n;

      if (sec->dofs_size < sizeof (dof_relohdr_t) ||
          sec->dofs_align != sizeof (dof_secidx_t)) {
            dtrace_dof_error(dof, "invalid relocation header");
            return (-1);
      }

      ss = dtrace_dof_sect(dof, DOF_SECT_STRTAB, dofr->dofr_strtab);
      rs = dtrace_dof_sect(dof, DOF_SECT_RELTAB, dofr->dofr_relsec);
      ts = dtrace_dof_sect(dof, DOF_SECT_NONE, dofr->dofr_tgtsec);

      if (ss == NULL || rs == NULL || ts == NULL)
            return (-1); /* dtrace_dof_error() has been called already */

      if (rs->dofs_entsize < sizeof (dof_relodesc_t) ||
          rs->dofs_align != sizeof (uint64_t)) {
            dtrace_dof_error(dof, "invalid relocation section");
            return (-1);
      }

      r = (dof_relodesc_t *)(uintptr_t)(daddr + rs->dofs_offset);
      n = rs->dofs_size / rs->dofs_entsize;

      for (i = 0; i < n; i++) {
            uintptr_t taddr = daddr + ts->dofs_offset + r->dofr_offset;

            switch (r->dofr_type) {
            case DOF_RELO_NONE:
                  break;
            case DOF_RELO_SETX:
                  if (r->dofr_offset >= ts->dofs_size || r->dofr_offset +
                      sizeof (uint64_t) > ts->dofs_size) {
                        dtrace_dof_error(dof, "bad relocation offset");
                        return (-1);
                  }

                  if (!IS_P2ALIGNED(taddr, sizeof (uint64_t))) {
                        dtrace_dof_error(dof, "misaligned setx relo");
                        return (-1);
                  }

                  *(uint64_t *)taddr += ubase;
                  break;
            default:
                  dtrace_dof_error(dof, "invalid relocation type");
                  return (-1);
            }

            r = (dof_relodesc_t *)((uintptr_t)r + rs->dofs_entsize);
      }

      return (0);
}

/*
 * The dof_hdr_t passed to dtrace_dof_slurp() should be a partially validated
 * header:  it should be at the front of a memory region that is at least
 * sizeof (dof_hdr_t) in size -- and then at least dof_hdr.dofh_loadsz in
 * size.  It need not be validated in any other way.
 */
static int
dtrace_dof_slurp(dof_hdr_t *dof, dtrace_vstate_t *vstate, cred_t *cr,
    dtrace_enabling_t **enabp, uint64_t ubase, int noprobes)
{
      uint64_t len = dof->dofh_loadsz, seclen;
      uintptr_t daddr = (uintptr_t)dof;
      dtrace_ecbdesc_t *ep;
      dtrace_enabling_t *enab;
      uint_t i;

      ASSERT(MUTEX_HELD(&dtrace_lock));
      ASSERT(dof->dofh_loadsz >= sizeof (dof_hdr_t));

      /*
       * Check the DOF header identification bytes.  In addition to checking
       * valid settings, we also verify that unused bits/bytes are zeroed so
       * we can use them later without fear of regressing existing binaries.
       */
      if (bcmp(&dof->dofh_ident[DOF_ID_MAG0],
          DOF_MAG_STRING, DOF_MAG_STRLEN) != 0) {
            dtrace_dof_error(dof, "DOF magic string mismatch");
            return (-1);
      }

      if (dof->dofh_ident[DOF_ID_MODEL] != DOF_MODEL_ILP32 &&
          dof->dofh_ident[DOF_ID_MODEL] != DOF_MODEL_LP64) {
            dtrace_dof_error(dof, "DOF has invalid data model");
            return (-1);
      }

      if (dof->dofh_ident[DOF_ID_ENCODING] != DOF_ENCODE_NATIVE) {
            dtrace_dof_error(dof, "DOF encoding mismatch");
            return (-1);
      }

      if (dof->dofh_ident[DOF_ID_VERSION] != DOF_VERSION_1 &&
          dof->dofh_ident[DOF_ID_VERSION] != DOF_VERSION_2) {
            dtrace_dof_error(dof, "DOF version mismatch");
            return (-1);
      }

      if (dof->dofh_ident[DOF_ID_DIFVERS] != DIF_VERSION_2) {
            dtrace_dof_error(dof, "DOF uses unsupported instruction set");
            return (-1);
      }

      if (dof->dofh_ident[DOF_ID_DIFIREG] > DIF_DIR_NREGS) {
            dtrace_dof_error(dof, "DOF uses too many integer registers");
            return (-1);
      }

      if (dof->dofh_ident[DOF_ID_DIFTREG] > DIF_DTR_NREGS) {
            dtrace_dof_error(dof, "DOF uses too many tuple registers");
            return (-1);
      }

      for (i = DOF_ID_PAD; i < DOF_ID_SIZE; i++) {
            if (dof->dofh_ident[i] != 0) {
                  dtrace_dof_error(dof, "DOF has invalid ident byte set");
                  return (-1);
            }
      }

      if (dof->dofh_flags & ~DOF_FL_VALID) {
            dtrace_dof_error(dof, "DOF has invalid flag bits set");
            return (-1);
      }

      if (dof->dofh_secsize == 0) {
            dtrace_dof_error(dof, "zero section header size");
            return (-1);
      }

      /*
       * Check that the section headers don't exceed the amount of DOF
       * data.  Note that we cast the section size and number of sections
       * to uint64_t's to prevent possible overflow in the multiplication.
       */
      seclen = (uint64_t)dof->dofh_secnum * (uint64_t)dof->dofh_secsize;

      if (dof->dofh_secoff > len || seclen > len ||
          dof->dofh_secoff + seclen > len) {
            dtrace_dof_error(dof, "truncated section headers");
            return (-1);
      }

      if (!IS_P2ALIGNED(dof->dofh_secoff, sizeof (uint64_t))) {
            dtrace_dof_error(dof, "misaligned section headers");
            return (-1);
      }

      if (!IS_P2ALIGNED(dof->dofh_secsize, sizeof (uint64_t))) {
            dtrace_dof_error(dof, "misaligned section size");
            return (-1);
      }

      /*
       * Take an initial pass through the section headers to be sure that
       * the headers don't have stray offsets.  If the 'noprobes' flag is
       * set, do not permit sections relating to providers, probes, or args.
       */
      for (i = 0; i < dof->dofh_secnum; i++) {
            dof_sec_t *sec = (dof_sec_t *)(daddr +
                (uintptr_t)dof->dofh_secoff + i * dof->dofh_secsize);

            if (noprobes) {
                  switch (sec->dofs_type) {
                  case DOF_SECT_PROVIDER:
                  case DOF_SECT_PROBES:
                  case DOF_SECT_PRARGS:
                  case DOF_SECT_PROFFS:
                        dtrace_dof_error(dof, "illegal sections "
                            "for enabling");
                        return (-1);
                  }
            }

            if (!(sec->dofs_flags & DOF_SECF_LOAD))
                  continue; /* just ignore non-loadable sections */

            if (sec->dofs_align & (sec->dofs_align - 1)) {
                  dtrace_dof_error(dof, "bad section alignment");
                  return (-1);
            }

            if (sec->dofs_offset & (sec->dofs_align - 1)) {
                  dtrace_dof_error(dof, "misaligned section");
                  return (-1);
            }

            if (sec->dofs_offset > len || sec->dofs_size > len ||
                sec->dofs_offset + sec->dofs_size > len) {
                  dtrace_dof_error(dof, "corrupt section header");
                  return (-1);
            }

            if (sec->dofs_type == DOF_SECT_STRTAB && *((char *)daddr +
                sec->dofs_offset + sec->dofs_size - 1) != '\0') {
                  dtrace_dof_error(dof, "non-terminating string table");
                  return (-1);
            }
      }

      /*
       * Take a second pass through the sections and locate and perform any
       * relocations that are present.  We do this after the first pass to
       * be sure that all sections have had their headers validated.
       */
      for (i = 0; i < dof->dofh_secnum; i++) {
            dof_sec_t *sec = (dof_sec_t *)(daddr +
                (uintptr_t)dof->dofh_secoff + i * dof->dofh_secsize);

            if (!(sec->dofs_flags & DOF_SECF_LOAD))
                  continue; /* skip sections that are not loadable */

            switch (sec->dofs_type) {
            case DOF_SECT_URELHDR:
                  if (dtrace_dof_relocate(dof, sec, ubase) != 0)
                        return (-1);
                  break;
            }
      }

      if ((enab = *enabp) == NULL)
            enab = *enabp = dtrace_enabling_create(vstate);

      for (i = 0; i < dof->dofh_secnum; i++) {
            dof_sec_t *sec = (dof_sec_t *)(daddr +
                (uintptr_t)dof->dofh_secoff + i * dof->dofh_secsize);

            if (sec->dofs_type != DOF_SECT_ECBDESC)
                  continue;

            if ((ep = dtrace_dof_ecbdesc(dof, sec, vstate, cr)) == NULL) {
                  dtrace_enabling_destroy(enab);
                  *enabp = NULL;
                  return (-1);
            }

            dtrace_enabling_add(enab, ep);
      }

      return (0);
}

/*
 * Process DOF for any options.  This routine assumes that the DOF has been
 * at least processed by dtrace_dof_slurp().
 */
static int
dtrace_dof_options(dof_hdr_t *dof, dtrace_state_t *state)
{
      int i, rval;
      uint32_t entsize;
      size_t offs;
      dof_optdesc_t *desc;

      for (i = 0; i < dof->dofh_secnum; i++) {
            dof_sec_t *sec = (dof_sec_t *)((uintptr_t)dof +
                (uintptr_t)dof->dofh_secoff + i * dof->dofh_secsize);

            if (sec->dofs_type != DOF_SECT_OPTDESC)
                  continue;

            if (sec->dofs_align != sizeof (uint64_t)) {
                  dtrace_dof_error(dof, "bad alignment in "
                      "option description");
                  return (EINVAL);
            }

            if ((entsize = sec->dofs_entsize) == 0) {
                  dtrace_dof_error(dof, "zeroed option entry size");
                  return (EINVAL);
            }

            if (entsize < sizeof (dof_optdesc_t)) {
                  dtrace_dof_error(dof, "bad option entry size");
                  return (EINVAL);
            }

            for (offs = 0; offs < sec->dofs_size; offs += entsize) {
                  desc = (dof_optdesc_t *)((uintptr_t)dof +
                      (uintptr_t)sec->dofs_offset + offs);

                  if (desc->dofo_strtab != DOF_SECIDX_NONE) {
                        dtrace_dof_error(dof, "non-zero option string");
                        return (EINVAL);
                  }

                  if (desc->dofo_value == DTRACEOPT_UNSET) {
                        dtrace_dof_error(dof, "unset option");
                        return (EINVAL);
                  }

                  if ((rval = dtrace_state_option(state,
                      desc->dofo_option, desc->dofo_value)) != 0) {
                        dtrace_dof_error(dof, "rejected option");
                        return (rval);
                  }
            }
      }

      return (0);
}

/*
 * DTrace Consumer State Functions
 */
static int
dtrace_dstate_init(dtrace_dstate_t *dstate, size_t size)
{
      size_t hashsize, maxper, min, chunksize = dstate->dtds_chunksize;
      void *base;
      uintptr_t limit;
      dtrace_dynvar_t *dvar, *next, *start;
      int i;

      ASSERT(MUTEX_HELD(&dtrace_lock));
      ASSERT(dstate->dtds_base == NULL && dstate->dtds_percpu == NULL);

      bzero(dstate, sizeof (dtrace_dstate_t));

      if ((dstate->dtds_chunksize = chunksize) == 0)
            dstate->dtds_chunksize = DTRACE_DYNVAR_CHUNKSIZE;

      if (size < (min = dstate->dtds_chunksize + sizeof (dtrace_dynhash_t)))
            size = min;

      if ((base = kmem_zalloc(size, KM_NOSLEEP)) == NULL)
            return (ENOMEM);

      dstate->dtds_size = size;
      dstate->dtds_base = base;
      dstate->dtds_percpu = kmem_cache_alloc(dtrace_state_cache, KM_SLEEP);
      bzero(dstate->dtds_percpu, NCPU * sizeof (dtrace_dstate_percpu_t));

      hashsize = size / (dstate->dtds_chunksize + sizeof (dtrace_dynhash_t));

      if (hashsize != 1 && (hashsize & 1))
            hashsize--;

      dstate->dtds_hashsize = hashsize;
      dstate->dtds_hash = dstate->dtds_base;

      /*
       * Set all of our hash buckets to point to the single sink, and (if
       * it hasn't already been set), set the sink's hash value to be the
       * sink sentinel value.  The sink is needed for dynamic variable
       * lookups to know that they have iterated over an entire, valid hash
       * chain.
       */
      for (i = 0; i < hashsize; i++)
            dstate->dtds_hash[i].dtdh_chain = &dtrace_dynhash_sink;

      if (dtrace_dynhash_sink.dtdv_hashval != DTRACE_DYNHASH_SINK)
            dtrace_dynhash_sink.dtdv_hashval = DTRACE_DYNHASH_SINK;

      /*
       * Determine number of active CPUs.  Divide free list evenly among
       * active CPUs.
       */
      start = (dtrace_dynvar_t *)
          ((uintptr_t)base + hashsize * sizeof (dtrace_dynhash_t));
      limit = (uintptr_t)base + size;

      maxper = (limit - (uintptr_t)start) / NCPU;
      maxper = (maxper / dstate->dtds_chunksize) * dstate->dtds_chunksize;

      for (i = 0; i < NCPU; i++) {
#if !defined(sun)
            if (CPU_ABSENT(i))
                  continue;
#endif
            dstate->dtds_percpu[i].dtdsc_free = dvar = start;

            /*
             * If we don't even have enough chunks to make it once through
             * NCPUs, we're just going to allocate everything to the first
             * CPU.  And if we're on the last CPU, we're going to allocate
             * whatever is left over.  In either case, we set the limit to
             * be the limit of the dynamic variable space.
             */
            if (maxper == 0 || i == NCPU - 1) {
                  limit = (uintptr_t)base + size;
                  start = NULL;
            } else {
                  limit = (uintptr_t)start + maxper;
                  start = (dtrace_dynvar_t *)limit;
            }

            ASSERT(limit <= (uintptr_t)base + size);

            for (;;) {
                  next = (dtrace_dynvar_t *)((uintptr_t)dvar +
                      dstate->dtds_chunksize);

                  if ((uintptr_t)next + dstate->dtds_chunksize >= limit)
                        break;

                  dvar->dtdv_next = next;
                  dvar = next;
            }

            if (maxper == 0)
                  break;
      }

      return (0);
}

static void
dtrace_dstate_fini(dtrace_dstate_t *dstate)
{
      ASSERT(MUTEX_HELD(&cpu_lock));

      if (dstate->dtds_base == NULL)
            return;

      kmem_free(dstate->dtds_base, dstate->dtds_size);
      kmem_cache_free(dtrace_state_cache, dstate->dtds_percpu);
}

static void
dtrace_vstate_fini(dtrace_vstate_t *vstate)
{
      /*
       * Logical XOR, where are you?
       */
      ASSERT((vstate->dtvs_nglobals == 0) ^ (vstate->dtvs_globals != NULL));

      if (vstate->dtvs_nglobals > 0) {
            kmem_free(vstate->dtvs_globals, vstate->dtvs_nglobals *
                sizeof (dtrace_statvar_t *));
      }

      if (vstate->dtvs_ntlocals > 0) {
            kmem_free(vstate->dtvs_tlocals, vstate->dtvs_ntlocals *
                sizeof (dtrace_difv_t));
      }

      ASSERT((vstate->dtvs_nlocals == 0) ^ (vstate->dtvs_locals != NULL));

      if (vstate->dtvs_nlocals > 0) {
            kmem_free(vstate->dtvs_locals, vstate->dtvs_nlocals *
                sizeof (dtrace_statvar_t *));
      }
}

#if defined(sun)
static void
dtrace_state_clean(dtrace_state_t *state)
{
      if (state->dts_activity == DTRACE_ACTIVITY_INACTIVE)
            return;

      dtrace_dynvar_clean(&state->dts_vstate.dtvs_dynvars);
      dtrace_speculation_clean(state);
}

static void
dtrace_state_deadman(dtrace_state_t *state)
{
      hrtime_t now;

      dtrace_sync();

      now = dtrace_gethrtime();

      if (state != dtrace_anon.dta_state &&
          now - state->dts_laststatus >= dtrace_deadman_user)
            return;

      /*
       * We must be sure that dts_alive never appears to be less than the
       * value upon entry to dtrace_state_deadman(), and because we lack a
       * dtrace_cas64(), we cannot store to it atomically.  We thus instead
       * store INT64_MAX to it, followed by a memory barrier, followed by
       * the new value.  This assures that dts_alive never appears to be
       * less than its true value, regardless of the order in which the
       * stores to the underlying storage are issued.
       */
      state->dts_alive = INT64_MAX;
      dtrace_membar_producer();
      state->dts_alive = now;
}
#else
static void
dtrace_state_clean(void *arg)
{
      dtrace_state_t *state = arg;
      dtrace_optval_t *opt = state->dts_options;

      if (state->dts_activity == DTRACE_ACTIVITY_INACTIVE)
            return;

      dtrace_dynvar_clean(&state->dts_vstate.dtvs_dynvars);
      dtrace_speculation_clean(state);

      callout_reset(&state->dts_cleaner, hz * opt[DTRACEOPT_CLEANRATE] / NANOSEC,
          dtrace_state_clean, state);
}

static void
dtrace_state_deadman(void *arg)
{
      dtrace_state_t *state = arg;
      hrtime_t now;

      dtrace_sync();

      dtrace_debug_output();

      now = dtrace_gethrtime();

      if (state != dtrace_anon.dta_state &&
          now - state->dts_laststatus >= dtrace_deadman_user)
            return;

      /*
       * We must be sure that dts_alive never appears to be less than the
       * value upon entry to dtrace_state_deadman(), and because we lack a
       * dtrace_cas64(), we cannot store to it atomically.  We thus instead
       * store INT64_MAX to it, followed by a memory barrier, followed by
       * the new value.  This assures that dts_alive never appears to be
       * less than its true value, regardless of the order in which the
       * stores to the underlying storage are issued.
       */
      state->dts_alive = INT64_MAX;
      dtrace_membar_producer();
      state->dts_alive = now;

      callout_reset(&state->dts_deadman, hz * dtrace_deadman_interval / NANOSEC,
          dtrace_state_deadman, state);
}
#endif

static dtrace_state_t *
#if defined(sun)
dtrace_state_create(dev_t *devp, cred_t *cr)
#else
dtrace_state_create(struct cdev *dev)
#endif
{
#if defined(sun)
      minor_t minor;
      major_t major;
#else
      cred_t *cr = NULL;
      int m = 0;
#endif
      char c[30];
      dtrace_state_t *state;
      dtrace_optval_t *opt;
      int bufsize = NCPU * sizeof (dtrace_buffer_t), i;

      ASSERT(MUTEX_HELD(&dtrace_lock));
      ASSERT(MUTEX_HELD(&cpu_lock));

#if defined(sun)
      minor = (minor_t)(uintptr_t)vmem_alloc(dtrace_minor, 1,
          VM_BESTFIT | VM_SLEEP);

      if (ddi_soft_state_zalloc(dtrace_softstate, minor) != DDI_SUCCESS) {
            vmem_free(dtrace_minor, (void *)(uintptr_t)minor, 1);
            return (NULL);
      }

      state = ddi_get_soft_state(dtrace_softstate, minor);
#else
      if (dev != NULL) {
            cr = dev->si_cred;
            m = dev2unit(dev);
            }

      /* Allocate memory for the state. */
      state = kmem_zalloc(sizeof(dtrace_state_t), KM_SLEEP);
#endif

      state->dts_epid = DTRACE_EPIDNONE + 1;

      (void) snprintf(c, sizeof (c), "dtrace_aggid_%d", m);
#if defined(sun)
      state->dts_aggid_arena = vmem_create(c, (void *)1, UINT32_MAX, 1,
          NULL, NULL, NULL, 0, VM_SLEEP | VMC_IDENTIFIER);

      if (devp != NULL) {
            major = getemajor(*devp);
      } else {
            major = ddi_driver_major(dtrace_devi);
      }

      state->dts_dev = makedevice(major, minor);

      if (devp != NULL)
            *devp = state->dts_dev;
#else
      state->dts_aggid_arena = new_unrhdr(1, INT_MAX, &dtrace_unr_mtx);
      state->dts_dev = dev;
#endif

      /*
       * We allocate NCPU buffers.  On the one hand, this can be quite
       * a bit of memory per instance (nearly 36K on a Starcat).  On the
       * other hand, it saves an additional memory reference in the probe
       * path.
       */
      state->dts_buffer = kmem_zalloc(bufsize, KM_SLEEP);
      state->dts_aggbuffer = kmem_zalloc(bufsize, KM_SLEEP);

#if defined(sun)
      state->dts_cleaner = CYCLIC_NONE;
      state->dts_deadman = CYCLIC_NONE;
#else
      callout_init(&state->dts_cleaner, CALLOUT_MPSAFE);
      callout_init(&state->dts_deadman, CALLOUT_MPSAFE);
#endif
      state->dts_vstate.dtvs_state = state;

      for (i = 0; i < DTRACEOPT_MAX; i++)
            state->dts_options[i] = DTRACEOPT_UNSET;

      /*
       * Set the default options.
       */
      opt = state->dts_options;
      opt[DTRACEOPT_BUFPOLICY] = DTRACEOPT_BUFPOLICY_SWITCH;
      opt[DTRACEOPT_BUFRESIZE] = DTRACEOPT_BUFRESIZE_AUTO;
      opt[DTRACEOPT_NSPEC] = dtrace_nspec_default;
      opt[DTRACEOPT_SPECSIZE] = dtrace_specsize_default;
      opt[DTRACEOPT_CPU] = (dtrace_optval_t)DTRACE_CPUALL;
      opt[DTRACEOPT_STRSIZE] = dtrace_strsize_default;
      opt[DTRACEOPT_STACKFRAMES] = dtrace_stackframes_default;
      opt[DTRACEOPT_USTACKFRAMES] = dtrace_ustackframes_default;
      opt[DTRACEOPT_CLEANRATE] = dtrace_cleanrate_default;
      opt[DTRACEOPT_AGGRATE] = dtrace_aggrate_default;
      opt[DTRACEOPT_SWITCHRATE] = dtrace_switchrate_default;
      opt[DTRACEOPT_STATUSRATE] = dtrace_statusrate_default;
      opt[DTRACEOPT_JSTACKFRAMES] = dtrace_jstackframes_default;
      opt[DTRACEOPT_JSTACKSTRSIZE] = dtrace_jstackstrsize_default;

      state->dts_activity = DTRACE_ACTIVITY_INACTIVE;

      /*
       * Depending on the user credentials, we set flag bits which alter probe
       * visibility or the amount of destructiveness allowed.  In the case of
       * actual anonymous tracing, or the possession of all privileges, all of
       * the normal checks are bypassed.
       */
      if (cr == NULL || PRIV_POLICY_ONLY(cr, PRIV_ALL, B_FALSE)) {
            state->dts_cred.dcr_visible = DTRACE_CRV_ALL;
            state->dts_cred.dcr_action = DTRACE_CRA_ALL;
      } else {
            /*
             * Set up the credentials for this instantiation.  We take a
             * hold on the credential to prevent it from disappearing on
             * us; this in turn prevents the zone_t referenced by this
             * credential from disappearing.  This means that we can
             * examine the credential and the zone from probe context.
             */
            crhold(cr);
            state->dts_cred.dcr_cred = cr;

            /*
             * CRA_PROC means "we have *some* privilege for dtrace" and
             * unlocks the use of variables like pid, zonename, etc.
             */
            if (PRIV_POLICY_ONLY(cr, PRIV_DTRACE_USER, B_FALSE) ||
                PRIV_POLICY_ONLY(cr, PRIV_DTRACE_PROC, B_FALSE)) {
                  state->dts_cred.dcr_action |= DTRACE_CRA_PROC;
            }

            /*
             * dtrace_user allows use of syscall and profile providers.
             * If the user also has proc_owner and/or proc_zone, we
             * extend the scope to include additional visibility and
             * destructive power.
             */
            if (PRIV_POLICY_ONLY(cr, PRIV_DTRACE_USER, B_FALSE)) {
                  if (PRIV_POLICY_ONLY(cr, PRIV_PROC_OWNER, B_FALSE)) {
                        state->dts_cred.dcr_visible |=
                            DTRACE_CRV_ALLPROC;

                        state->dts_cred.dcr_action |=
                            DTRACE_CRA_PROC_DESTRUCTIVE_ALLUSER;
                  }

                  if (PRIV_POLICY_ONLY(cr, PRIV_PROC_ZONE, B_FALSE)) {
                        state->dts_cred.dcr_visible |=
                            DTRACE_CRV_ALLZONE;

                        state->dts_cred.dcr_action |=
                            DTRACE_CRA_PROC_DESTRUCTIVE_ALLZONE;
                  }

                  /*
                   * If we have all privs in whatever zone this is,
                   * we can do destructive things to processes which
                   * have altered credentials.
                   */
#if defined(sun)
                  if (priv_isequalset(priv_getset(cr, PRIV_EFFECTIVE),
                      cr->cr_zone->zone_privset)) {
                        state->dts_cred.dcr_action |=
                            DTRACE_CRA_PROC_DESTRUCTIVE_CREDCHG;
                  }
#endif
            }

            /*
             * Holding the dtrace_kernel privilege also implies that
             * the user has the dtrace_user privilege from a visibility
             * perspective.  But without further privileges, some
             * destructive actions are not available.
             */
            if (PRIV_POLICY_ONLY(cr, PRIV_DTRACE_KERNEL, B_FALSE)) {
                  /*
                   * Make all probes in all zones visible.  However,
                   * this doesn't mean that all actions become available
                   * to all zones.
                   */
                  state->dts_cred.dcr_visible |= DTRACE_CRV_KERNEL |
                      DTRACE_CRV_ALLPROC | DTRACE_CRV_ALLZONE;

                  state->dts_cred.dcr_action |= DTRACE_CRA_KERNEL |
                      DTRACE_CRA_PROC;
                  /*
                   * Holding proc_owner means that destructive actions
                   * for *this* zone are allowed.
                   */
                  if (PRIV_POLICY_ONLY(cr, PRIV_PROC_OWNER, B_FALSE))
                        state->dts_cred.dcr_action |=
                            DTRACE_CRA_PROC_DESTRUCTIVE_ALLUSER;

                  /*
                   * Holding proc_zone means that destructive actions
                   * for this user/group ID in all zones is allowed.
                   */
                  if (PRIV_POLICY_ONLY(cr, PRIV_PROC_ZONE, B_FALSE))
                        state->dts_cred.dcr_action |=
                            DTRACE_CRA_PROC_DESTRUCTIVE_ALLZONE;

#if defined(sun)
                  /*
                   * If we have all privs in whatever zone this is,
                   * we can do destructive things to processes which
                   * have altered credentials.
                   */
                  if (priv_isequalset(priv_getset(cr, PRIV_EFFECTIVE),
                      cr->cr_zone->zone_privset)) {
                        state->dts_cred.dcr_action |=
                            DTRACE_CRA_PROC_DESTRUCTIVE_CREDCHG;
                  }
#endif
            }

            /*
             * Holding the dtrace_proc privilege gives control over fasttrap
             * and pid providers.  We need to grant wider destructive
             * privileges in the event that the user has proc_owner and/or
             * proc_zone.
             */
            if (PRIV_POLICY_ONLY(cr, PRIV_DTRACE_PROC, B_FALSE)) {
                  if (PRIV_POLICY_ONLY(cr, PRIV_PROC_OWNER, B_FALSE))
                        state->dts_cred.dcr_action |=
                            DTRACE_CRA_PROC_DESTRUCTIVE_ALLUSER;

                  if (PRIV_POLICY_ONLY(cr, PRIV_PROC_ZONE, B_FALSE))
                        state->dts_cred.dcr_action |=
                            DTRACE_CRA_PROC_DESTRUCTIVE_ALLZONE;
            }
      }

      return (state);
}

static int
dtrace_state_buffer(dtrace_state_t *state, dtrace_buffer_t *buf, int which)
{
      dtrace_optval_t *opt = state->dts_options, size;
      processorid_t cpu = 0;;
      int flags = 0, rval;

      ASSERT(MUTEX_HELD(&dtrace_lock));
      ASSERT(MUTEX_HELD(&cpu_lock));
      ASSERT(which < DTRACEOPT_MAX);
      ASSERT(state->dts_activity == DTRACE_ACTIVITY_INACTIVE ||
          (state == dtrace_anon.dta_state &&
          state->dts_activity == DTRACE_ACTIVITY_ACTIVE));

      if (opt[which] == DTRACEOPT_UNSET || opt[which] == 0)
            return (0);

      if (opt[DTRACEOPT_CPU] != DTRACEOPT_UNSET)
            cpu = opt[DTRACEOPT_CPU];

      if (which == DTRACEOPT_SPECSIZE)
            flags |= DTRACEBUF_NOSWITCH;

      if (which == DTRACEOPT_BUFSIZE) {
            if (opt[DTRACEOPT_BUFPOLICY] == DTRACEOPT_BUFPOLICY_RING)
                  flags |= DTRACEBUF_RING;

            if (opt[DTRACEOPT_BUFPOLICY] == DTRACEOPT_BUFPOLICY_FILL)
                  flags |= DTRACEBUF_FILL;

            if (state != dtrace_anon.dta_state ||
                state->dts_activity != DTRACE_ACTIVITY_ACTIVE)
                  flags |= DTRACEBUF_INACTIVE;
      }

      for (size = opt[which]; size >= sizeof (uint64_t); size >>= 1) {
            /*
             * The size must be 8-byte aligned.  If the size is not 8-byte
             * aligned, drop it down by the difference.
             */
            if (size & (sizeof (uint64_t) - 1))
                  size -= size & (sizeof (uint64_t) - 1);

            if (size < state->dts_reserve) {
                  /*
                   * Buffers always must be large enough to accommodate
                   * their prereserved space.  We return E2BIG instead
                   * of ENOMEM in this case to allow for user-level
                   * software to differentiate the cases.
                   */
                  return (E2BIG);
            }

            rval = dtrace_buffer_alloc(buf, size, flags, cpu);

            if (rval != ENOMEM) {
                  opt[which] = size;
                  return (rval);
            }

            if (opt[DTRACEOPT_BUFRESIZE] == DTRACEOPT_BUFRESIZE_MANUAL)
                  return (rval);
      }

      return (ENOMEM);
}

static int
dtrace_state_buffers(dtrace_state_t *state)
{
      dtrace_speculation_t *spec = state->dts_speculations;
      int rval, i;

      if ((rval = dtrace_state_buffer(state, state->dts_buffer,
          DTRACEOPT_BUFSIZE)) != 0)
            return (rval);

      if ((rval = dtrace_state_buffer(state, state->dts_aggbuffer,
          DTRACEOPT_AGGSIZE)) != 0)
            return (rval);

      for (i = 0; i < state->dts_nspeculations; i++) {
            if ((rval = dtrace_state_buffer(state,
                spec[i].dtsp_buffer, DTRACEOPT_SPECSIZE)) != 0)
                  return (rval);
      }

      return (0);
}

static void
dtrace_state_prereserve(dtrace_state_t *state)
{
      dtrace_ecb_t *ecb;
      dtrace_probe_t *probe;

      state->dts_reserve = 0;

      if (state->dts_options[DTRACEOPT_BUFPOLICY] != DTRACEOPT_BUFPOLICY_FILL)
            return;

      /*
       * If our buffer policy is a "fill" buffer policy, we need to set the
       * prereserved space to be the space required by the END probes.
       */
      probe = dtrace_probes[dtrace_probeid_end - 1];
      ASSERT(probe != NULL);

      for (ecb = probe->dtpr_ecb; ecb != NULL; ecb = ecb->dte_next) {
            if (ecb->dte_state != state)
                  continue;

            state->dts_reserve += ecb->dte_needed + ecb->dte_alignment;
      }
}

static int
dtrace_state_go(dtrace_state_t *state, processorid_t *cpu)
{
      dtrace_optval_t *opt = state->dts_options, sz, nspec;
      dtrace_speculation_t *spec;
      dtrace_buffer_t *buf;
#if defined(sun)
      cyc_handler_t hdlr;
      cyc_time_t when;
#endif
      int rval = 0, i, bufsize = NCPU * sizeof (dtrace_buffer_t);
      dtrace_icookie_t cookie;

      mutex_enter(&cpu_lock);
      mutex_enter(&dtrace_lock);

      if (state->dts_activity != DTRACE_ACTIVITY_INACTIVE) {
            rval = EBUSY;
            goto out;
      }

      /*
       * Before we can perform any checks, we must prime all of the
       * retained enablings that correspond to this state.
       */
      dtrace_enabling_prime(state);

      if (state->dts_destructive && !state->dts_cred.dcr_destructive) {
            rval = EACCES;
            goto out;
      }

      dtrace_state_prereserve(state);

      /*
       * Now we want to do is try to allocate our speculations.
       * We do not automatically resize the number of speculations; if
       * this fails, we will fail the operation.
       */
      nspec = opt[DTRACEOPT_NSPEC];
      ASSERT(nspec != DTRACEOPT_UNSET);

      if (nspec > INT_MAX) {
            rval = ENOMEM;
            goto out;
      }

      spec = kmem_zalloc(nspec * sizeof (dtrace_speculation_t), KM_NOSLEEP);

      if (spec == NULL) {
            rval = ENOMEM;
            goto out;
      }

      state->dts_speculations = spec;
      state->dts_nspeculations = (int)nspec;

      for (i = 0; i < nspec; i++) {
            if ((buf = kmem_zalloc(bufsize, KM_NOSLEEP)) == NULL) {
                  rval = ENOMEM;
                  goto err;
            }

            spec[i].dtsp_buffer = buf;
      }

      if (opt[DTRACEOPT_GRABANON] != DTRACEOPT_UNSET) {
            if (dtrace_anon.dta_state == NULL) {
                  rval = ENOENT;
                  goto out;
            }

            if (state->dts_necbs != 0) {
                  rval = EALREADY;
                  goto out;
            }

            state->dts_anon = dtrace_anon_grab();
            ASSERT(state->dts_anon != NULL);
            state = state->dts_anon;

            /*
             * We want "grabanon" to be set in the grabbed state, so we'll
             * copy that option value from the grabbing state into the
             * grabbed state.
             */
            state->dts_options[DTRACEOPT_GRABANON] =
                opt[DTRACEOPT_GRABANON];

            *cpu = dtrace_anon.dta_beganon;

            /*
             * If the anonymous state is active (as it almost certainly
             * is if the anonymous enabling ultimately matched anything),
             * we don't allow any further option processing -- but we
             * don't return failure.
             */
            if (state->dts_activity != DTRACE_ACTIVITY_INACTIVE)
                  goto out;
      }

      if (opt[DTRACEOPT_AGGSIZE] != DTRACEOPT_UNSET &&
          opt[DTRACEOPT_AGGSIZE] != 0) {
            if (state->dts_aggregations == NULL) {
                  /*
                   * We're not going to create an aggregation buffer
                   * because we don't have any ECBs that contain
                   * aggregations -- set this option to 0.
                   */
                  opt[DTRACEOPT_AGGSIZE] = 0;
            } else {
                  /*
                   * If we have an aggregation buffer, we must also have
                   * a buffer to use as scratch.
                   */
                  if (opt[DTRACEOPT_BUFSIZE] == DTRACEOPT_UNSET ||
                      opt[DTRACEOPT_BUFSIZE] < state->dts_needed) {
                        opt[DTRACEOPT_BUFSIZE] = state->dts_needed;
                  }
            }
      }

      if (opt[DTRACEOPT_SPECSIZE] != DTRACEOPT_UNSET &&
          opt[DTRACEOPT_SPECSIZE] != 0) {
            if (!state->dts_speculates) {
                  /*
                   * We're not going to create speculation buffers
                   * because we don't have any ECBs that actually
                   * speculate -- set the speculation size to 0.
                   */
                  opt[DTRACEOPT_SPECSIZE] = 0;
            }
      }

      /*
       * The bare minimum size for any buffer that we're actually going to
       * do anything to is sizeof (uint64_t).
       */
      sz = sizeof (uint64_t);

      if ((state->dts_needed != 0 && opt[DTRACEOPT_BUFSIZE] < sz) ||
          (state->dts_speculates && opt[DTRACEOPT_SPECSIZE] < sz) ||
          (state->dts_aggregations != NULL && opt[DTRACEOPT_AGGSIZE] < sz)) {
            /*
             * A buffer size has been explicitly set to 0 (or to a size
             * that will be adjusted to 0) and we need the space -- we
             * need to return failure.  We return ENOSPC to differentiate
             * it from failing to allocate a buffer due to failure to meet
             * the reserve (for which we return E2BIG).
             */
            rval = ENOSPC;
            goto out;
      }

      if ((rval = dtrace_state_buffers(state)) != 0)
            goto err;

      if ((sz = opt[DTRACEOPT_DYNVARSIZE]) == DTRACEOPT_UNSET)
            sz = dtrace_dstate_defsize;

      do {
            rval = dtrace_dstate_init(&state->dts_vstate.dtvs_dynvars, sz);

            if (rval == 0)
                  break;

            if (opt[DTRACEOPT_BUFRESIZE] == DTRACEOPT_BUFRESIZE_MANUAL)
                  goto err;
      } while (sz >>= 1);

      opt[DTRACEOPT_DYNVARSIZE] = sz;

      if (rval != 0)
            goto err;

      if (opt[DTRACEOPT_STATUSRATE] > dtrace_statusrate_max)
            opt[DTRACEOPT_STATUSRATE] = dtrace_statusrate_max;

      if (opt[DTRACEOPT_CLEANRATE] == 0)
            opt[DTRACEOPT_CLEANRATE] = dtrace_cleanrate_max;

      if (opt[DTRACEOPT_CLEANRATE] < dtrace_cleanrate_min)
            opt[DTRACEOPT_CLEANRATE] = dtrace_cleanrate_min;

      if (opt[DTRACEOPT_CLEANRATE] > dtrace_cleanrate_max)
            opt[DTRACEOPT_CLEANRATE] = dtrace_cleanrate_max;

      state->dts_alive = state->dts_laststatus = dtrace_gethrtime();
#if defined(sun)
      hdlr.cyh_func = (cyc_func_t)dtrace_state_clean;
      hdlr.cyh_arg = state;
      hdlr.cyh_level = CY_LOW_LEVEL;

      when.cyt_when = 0;
      when.cyt_interval = opt[DTRACEOPT_CLEANRATE];

      state->dts_cleaner = cyclic_add(&hdlr, &when);

      hdlr.cyh_func = (cyc_func_t)dtrace_state_deadman;
      hdlr.cyh_arg = state;
      hdlr.cyh_level = CY_LOW_LEVEL;

      when.cyt_when = 0;
      when.cyt_interval = dtrace_deadman_interval;

      state->dts_deadman = cyclic_add(&hdlr, &when);
#else
      callout_reset(&state->dts_cleaner, hz * opt[DTRACEOPT_CLEANRATE] / NANOSEC,
          dtrace_state_clean, state);
      callout_reset(&state->dts_deadman, hz * dtrace_deadman_interval / NANOSEC,
          dtrace_state_deadman, state);
#endif

      state->dts_activity = DTRACE_ACTIVITY_WARMUP;

      /*
       * Now it's time to actually fire the BEGIN probe.  We need to disable
       * interrupts here both to record the CPU on which we fired the BEGIN
       * probe (the data from this CPU will be processed first at user
       * level) and to manually activate the buffer for this CPU.
       */
      cookie = dtrace_interrupt_disable();
      *cpu = curcpu;
      ASSERT(state->dts_buffer[*cpu].dtb_flags & DTRACEBUF_INACTIVE);
      state->dts_buffer[*cpu].dtb_flags &= ~DTRACEBUF_INACTIVE;

      dtrace_probe(dtrace_probeid_begin,
          (uint64_t)(uintptr_t)state, 0, 0, 0, 0);
      dtrace_interrupt_enable(cookie);
      /*
       * We may have had an exit action from a BEGIN probe; only change our
       * state to ACTIVE if we're still in WARMUP.
       */
      ASSERT(state->dts_activity == DTRACE_ACTIVITY_WARMUP ||
          state->dts_activity == DTRACE_ACTIVITY_DRAINING);

      if (state->dts_activity == DTRACE_ACTIVITY_WARMUP)
            state->dts_activity = DTRACE_ACTIVITY_ACTIVE;

      /*
       * Regardless of whether or not now we're in ACTIVE or DRAINING, we
       * want each CPU to transition its principal buffer out of the
       * INACTIVE state.  Doing this assures that no CPU will suddenly begin
       * processing an ECB halfway down a probe's ECB chain; all CPUs will
       * atomically transition from processing none of a state's ECBs to
       * processing all of them.
       */
      dtrace_xcall(DTRACE_CPUALL,
          (dtrace_xcall_t)dtrace_buffer_activate, state);
      goto out;

err:
      dtrace_buffer_free(state->dts_buffer);
      dtrace_buffer_free(state->dts_aggbuffer);

      if ((nspec = state->dts_nspeculations) == 0) {
            ASSERT(state->dts_speculations == NULL);
            goto out;
      }

      spec = state->dts_speculations;
      ASSERT(spec != NULL);

      for (i = 0; i < state->dts_nspeculations; i++) {
            if ((buf = spec[i].dtsp_buffer) == NULL)
                  break;

            dtrace_buffer_free(buf);
            kmem_free(buf, bufsize);
      }

      kmem_free(spec, nspec * sizeof (dtrace_speculation_t));
      state->dts_nspeculations = 0;
      state->dts_speculations = NULL;

out:
      mutex_exit(&dtrace_lock);
      mutex_exit(&cpu_lock);

      return (rval);
}

static int
dtrace_state_stop(dtrace_state_t *state, processorid_t *cpu)
{
      dtrace_icookie_t cookie;

      ASSERT(MUTEX_HELD(&dtrace_lock));

      if (state->dts_activity != DTRACE_ACTIVITY_ACTIVE &&
          state->dts_activity != DTRACE_ACTIVITY_DRAINING)
            return (EINVAL);

      /*
       * We'll set the activity to DTRACE_ACTIVITY_DRAINING, and issue a sync
       * to be sure that every CPU has seen it.  See below for the details
       * on why this is done.
       */
      state->dts_activity = DTRACE_ACTIVITY_DRAINING;
      dtrace_sync();

      /*
       * By this point, it is impossible for any CPU to be still processing
       * with DTRACE_ACTIVITY_ACTIVE.  We can thus set our activity to
       * DTRACE_ACTIVITY_COOLDOWN and know that we're not racing with any
       * other CPU in dtrace_buffer_reserve().  This allows dtrace_probe()
       * and callees to know that the activity is DTRACE_ACTIVITY_COOLDOWN
       * iff we're in the END probe.
       */
      state->dts_activity = DTRACE_ACTIVITY_COOLDOWN;
      dtrace_sync();
      ASSERT(state->dts_activity == DTRACE_ACTIVITY_COOLDOWN);

      /*
       * Finally, we can release the reserve and call the END probe.  We
       * disable interrupts across calling the END probe to allow us to
       * return the CPU on which we actually called the END probe.  This
       * allows user-land to be sure that this CPU's principal buffer is
       * processed last.
       */
      state->dts_reserve = 0;

      cookie = dtrace_interrupt_disable();
      *cpu = curcpu;
      dtrace_probe(dtrace_probeid_end,
          (uint64_t)(uintptr_t)state, 0, 0, 0, 0);
      dtrace_interrupt_enable(cookie);

      state->dts_activity = DTRACE_ACTIVITY_STOPPED;
      dtrace_sync();

      return (0);
}

static int
dtrace_state_option(dtrace_state_t *state, dtrace_optid_t option,
    dtrace_optval_t val)
{
      ASSERT(MUTEX_HELD(&dtrace_lock));

      if (state->dts_activity != DTRACE_ACTIVITY_INACTIVE)
            return (EBUSY);

      if (option >= DTRACEOPT_MAX)
            return (EINVAL);

      if (option != DTRACEOPT_CPU && val < 0)
            return (EINVAL);

      switch (option) {
      case DTRACEOPT_DESTRUCTIVE:
            if (dtrace_destructive_disallow)
                  return (EACCES);

            state->dts_cred.dcr_destructive = 1;
            break;

      case DTRACEOPT_BUFSIZE:
      case DTRACEOPT_DYNVARSIZE:
      case DTRACEOPT_AGGSIZE:
      case DTRACEOPT_SPECSIZE:
      case DTRACEOPT_STRSIZE:
            if (val < 0)
                  return (EINVAL);

            if (val >= LONG_MAX) {
                  /*
                   * If this is an otherwise negative value, set it to
                   * the highest multiple of 128m less than LONG_MAX.
                   * Technically, we're adjusting the size without
                   * regard to the buffer resizing policy, but in fact,
                   * this has no effect -- if we set the buffer size to
                   * ~LONG_MAX and the buffer policy is ultimately set to
                   * be "manual", the buffer allocation is guaranteed to
                   * fail, if only because the allocation requires two
                   * buffers.  (We set the the size to the highest
                   * multiple of 128m because it ensures that the size
                   * will remain a multiple of a megabyte when
                   * repeatedly halved -- all the way down to 15m.)
                   */
                  val = LONG_MAX - (1 << 27) + 1;
            }
      }

      state->dts_options[option] = val;

      return (0);
}

static void
dtrace_state_destroy(dtrace_state_t *state)
{
      dtrace_ecb_t *ecb;
      dtrace_vstate_t *vstate = &state->dts_vstate;
#if defined(sun)
      minor_t minor = getminor(state->dts_dev);
#endif
      int i, bufsize = NCPU * sizeof (dtrace_buffer_t);
      dtrace_speculation_t *spec = state->dts_speculations;
      int nspec = state->dts_nspeculations;
      uint32_t match;

      ASSERT(MUTEX_HELD(&dtrace_lock));
      ASSERT(MUTEX_HELD(&cpu_lock));

      /*
       * First, retract any retained enablings for this state.
       */
      dtrace_enabling_retract(state);
      ASSERT(state->dts_nretained == 0);

      if (state->dts_activity == DTRACE_ACTIVITY_ACTIVE ||
          state->dts_activity == DTRACE_ACTIVITY_DRAINING) {
            /*
             * We have managed to come into dtrace_state_destroy() on a
             * hot enabling -- almost certainly because of a disorderly
             * shutdown of a consumer.  (That is, a consumer that is
             * exiting without having called dtrace_stop().) In this case,
             * we're going to set our activity to be KILLED, and then
             * issue a sync to be sure that everyone is out of probe
             * context before we start blowing away ECBs.
             */
            state->dts_activity = DTRACE_ACTIVITY_KILLED;
            dtrace_sync();
      }

      /*
       * Release the credential hold we took in dtrace_state_create().
       */
      if (state->dts_cred.dcr_cred != NULL)
            crfree(state->dts_cred.dcr_cred);

      /*
       * Now we can safely disable and destroy any enabled probes.  Because
       * any DTRACE_PRIV_KERNEL probes may actually be slowing our progress
       * (especially if they're all enabled), we take two passes through the
       * ECBs:  in the first, we disable just DTRACE_PRIV_KERNEL probes, and
       * in the second we disable whatever is left over.
       */
      for (match = DTRACE_PRIV_KERNEL; ; match = 0) {
            for (i = 0; i < state->dts_necbs; i++) {
                  if ((ecb = state->dts_ecbs[i]) == NULL)
                        continue;

                  if (match && ecb->dte_probe != NULL) {
                        dtrace_probe_t *probe = ecb->dte_probe;
                        dtrace_provider_t *prov = probe->dtpr_provider;

                        if (!(prov->dtpv_priv.dtpp_flags & match))
                              continue;
                  }

                  dtrace_ecb_disable(ecb);
                  dtrace_ecb_destroy(ecb);
            }

            if (!match)
                  break;
      }

      /*
       * Before we free the buffers, perform one more sync to assure that
       * every CPU is out of probe context.
       */
      dtrace_sync();

      dtrace_buffer_free(state->dts_buffer);
      dtrace_buffer_free(state->dts_aggbuffer);

      for (i = 0; i < nspec; i++)
            dtrace_buffer_free(spec[i].dtsp_buffer);

#if defined(sun)
      if (state->dts_cleaner != CYCLIC_NONE)
            cyclic_remove(state->dts_cleaner);

      if (state->dts_deadman != CYCLIC_NONE)
            cyclic_remove(state->dts_deadman);
#else
      callout_stop(&state->dts_cleaner);
      callout_drain(&state->dts_cleaner);
      callout_stop(&state->dts_deadman);
      callout_drain(&state->dts_deadman);
#endif

      dtrace_dstate_fini(&vstate->dtvs_dynvars);
      dtrace_vstate_fini(vstate);
      if (state->dts_ecbs != NULL)
            kmem_free(state->dts_ecbs, state->dts_necbs * sizeof (dtrace_ecb_t *));

      if (state->dts_aggregations != NULL) {
#ifdef DEBUG
            for (i = 0; i < state->dts_naggregations; i++)
                  ASSERT(state->dts_aggregations[i] == NULL);
#endif
            ASSERT(state->dts_naggregations > 0);
            kmem_free(state->dts_aggregations,
                state->dts_naggregations * sizeof (dtrace_aggregation_t *));
      }

      kmem_free(state->dts_buffer, bufsize);
      kmem_free(state->dts_aggbuffer, bufsize);

      for (i = 0; i < nspec; i++)
            kmem_free(spec[i].dtsp_buffer, bufsize);

      if (spec != NULL)
            kmem_free(spec, nspec * sizeof (dtrace_speculation_t));

      dtrace_format_destroy(state);

      if (state->dts_aggid_arena != NULL) {
#if defined(sun)
            vmem_destroy(state->dts_aggid_arena);
#else
            delete_unrhdr(state->dts_aggid_arena);
#endif
            state->dts_aggid_arena = NULL;
      }
#if defined(sun)
      ddi_soft_state_free(dtrace_softstate, minor);
      vmem_free(dtrace_minor, (void *)(uintptr_t)minor, 1);
#endif
}

/*
 * DTrace Anonymous Enabling Functions
 */
static dtrace_state_t *
dtrace_anon_grab(void)
{
      dtrace_state_t *state;

      ASSERT(MUTEX_HELD(&dtrace_lock));

      if ((state = dtrace_anon.dta_state) == NULL) {
            ASSERT(dtrace_anon.dta_enabling == NULL);
            return (NULL);
      }

      ASSERT(dtrace_anon.dta_enabling != NULL);
      ASSERT(dtrace_retained != NULL);

      dtrace_enabling_destroy(dtrace_anon.dta_enabling);
      dtrace_anon.dta_enabling = NULL;
      dtrace_anon.dta_state = NULL;

      return (state);
}

static void
dtrace_anon_property(void)
{
      int i, rv;
      dtrace_state_t *state;
      dof_hdr_t *dof;
      char c[32];       /* enough for "dof-data-" + digits */

      ASSERT(MUTEX_HELD(&dtrace_lock));
      ASSERT(MUTEX_HELD(&cpu_lock));

      for (i = 0; ; i++) {
            (void) snprintf(c, sizeof (c), "dof-data-%d", i);

            dtrace_err_verbose = 1;

            if ((dof = dtrace_dof_property(c)) == NULL) {
                  dtrace_err_verbose = 0;
                  break;
            }

#if defined(sun)
            /*
             * We want to create anonymous state, so we need to transition
             * the kernel debugger to indicate that DTrace is active.  If
             * this fails (e.g. because the debugger has modified text in
             * some way), we won't continue with the processing.
             */
            if (kdi_dtrace_set(KDI_DTSET_DTRACE_ACTIVATE) != 0) {
                  cmn_err(CE_NOTE, "kernel debugger active; anonymous "
                      "enabling ignored.");
                  dtrace_dof_destroy(dof);
                  break;
            }
#endif

            /*
             * If we haven't allocated an anonymous state, we'll do so now.
             */
            if ((state = dtrace_anon.dta_state) == NULL) {
#if defined(sun)
                  state = dtrace_state_create(NULL, NULL);
#else
                  state = dtrace_state_create(NULL);
#endif
                  dtrace_anon.dta_state = state;

                  if (state == NULL) {
                        /*
                         * This basically shouldn't happen:  the only
                         * failure mode from dtrace_state_create() is a
                         * failure of ddi_soft_state_zalloc() that
                         * itself should never happen.  Still, the
                         * interface allows for a failure mode, and
                         * we want to fail as gracefully as possible:
                         * we'll emit an error message and cease
                         * processing anonymous state in this case.
                         */
                        cmn_err(CE_WARN, "failed to create "
                            "anonymous state");
                        dtrace_dof_destroy(dof);
                        break;
                  }
            }

            rv = dtrace_dof_slurp(dof, &state->dts_vstate, CRED(),
                &dtrace_anon.dta_enabling, 0, B_TRUE);

            if (rv == 0)
                  rv = dtrace_dof_options(dof, state);

            dtrace_err_verbose = 0;
            dtrace_dof_destroy(dof);

            if (rv != 0) {
                  /*
                   * This is malformed DOF; chuck any anonymous state
                   * that we created.
                   */
                  ASSERT(dtrace_anon.dta_enabling == NULL);
                  dtrace_state_destroy(state);
                  dtrace_anon.dta_state = NULL;
                  break;
            }

            ASSERT(dtrace_anon.dta_enabling != NULL);
      }

      if (dtrace_anon.dta_enabling != NULL) {
            int rval;

            /*
             * dtrace_enabling_retain() can only fail because we are
             * trying to retain more enablings than are allowed -- but
             * we only have one anonymous enabling, and we are guaranteed
             * to be allowed at least one retained enabling; we assert
             * that dtrace_enabling_retain() returns success.
             */
            rval = dtrace_enabling_retain(dtrace_anon.dta_enabling);
            ASSERT(rval == 0);

            dtrace_enabling_dump(dtrace_anon.dta_enabling);
      }
}

#if defined(sun)
/*
 * DTrace Helper Functions
 */
static void
dtrace_helper_trace(dtrace_helper_action_t *helper,
    dtrace_mstate_t *mstate, dtrace_vstate_t *vstate, int where)
{
      uint32_t size, next, nnext, i;
      dtrace_helptrace_t *ent;
      uint16_t flags = cpu_core[curcpu].cpuc_dtrace_flags;

      if (!dtrace_helptrace_enabled)
            return;

      ASSERT(vstate->dtvs_nlocals <= dtrace_helptrace_nlocals);

      /*
       * What would a tracing framework be without its own tracing
       * framework?  (Well, a hell of a lot simpler, for starters...)
       */
      size = sizeof (dtrace_helptrace_t) + dtrace_helptrace_nlocals *
          sizeof (uint64_t) - sizeof (uint64_t);

      /*
       * Iterate until we can allocate a slot in the trace buffer.
       */
      do {
            next = dtrace_helptrace_next;

            if (next + size < dtrace_helptrace_bufsize) {
                  nnext = next + size;
            } else {
                  nnext = size;
            }
      } while (dtrace_cas32(&dtrace_helptrace_next, next, nnext) != next);

      /*
       * We have our slot; fill it in.
       */
      if (nnext == size)
            next = 0;

      ent = (dtrace_helptrace_t *)&dtrace_helptrace_buffer[next];
      ent->dtht_helper = helper;
      ent->dtht_where = where;
      ent->dtht_nlocals = vstate->dtvs_nlocals;

      ent->dtht_fltoffs = (mstate->dtms_present & DTRACE_MSTATE_FLTOFFS) ?
          mstate->dtms_fltoffs : -1;
      ent->dtht_fault = DTRACE_FLAGS2FLT(flags);
      ent->dtht_illval = cpu_core[curcpu].cpuc_dtrace_illval;

      for (i = 0; i < vstate->dtvs_nlocals; i++) {
            dtrace_statvar_t *svar;

            if ((svar = vstate->dtvs_locals[i]) == NULL)
                  continue;

            ASSERT(svar->dtsv_size >= NCPU * sizeof (uint64_t));
            ent->dtht_locals[i] =
                ((uint64_t *)(uintptr_t)svar->dtsv_data)[curcpu];
      }
}
#endif

#if defined(sun)
static uint64_t
dtrace_helper(int which, dtrace_mstate_t *mstate,
    dtrace_state_t *state, uint64_t arg0, uint64_t arg1)
{
      uint16_t *flags = &cpu_core[curcpu].cpuc_dtrace_flags;
      uint64_t sarg0 = mstate->dtms_arg[0];
      uint64_t sarg1 = mstate->dtms_arg[1];
      uint64_t rval;
      dtrace_helpers_t *helpers = curproc->p_dtrace_helpers;
      dtrace_helper_action_t *helper;
      dtrace_vstate_t *vstate;
      dtrace_difo_t *pred;
      int i, trace = dtrace_helptrace_enabled;

      ASSERT(which >= 0 && which < DTRACE_NHELPER_ACTIONS);

      if (helpers == NULL)
            return (0);

      if ((helper = helpers->dthps_actions[which]) == NULL)
            return (0);

      vstate = &helpers->dthps_vstate;
      mstate->dtms_arg[0] = arg0;
      mstate->dtms_arg[1] = arg1;

      /*
       * Now iterate over each helper.  If its predicate evaluates to 'true',
       * we'll call the corresponding actions.  Note that the below calls
       * to dtrace_dif_emulate() may set faults in machine state.  This is
       * okay:  our caller (the outer dtrace_dif_emulate()) will simply plow
       * the stored DIF offset with its own (which is the desired behavior).
       * Also, note the calls to dtrace_dif_emulate() may allocate scratch
       * from machine state; this is okay, too.
       */
      for (; helper != NULL; helper = helper->dtha_next) {
            if ((pred = helper->dtha_predicate) != NULL) {
                  if (trace)
                        dtrace_helper_trace(helper, mstate, vstate, 0);

                  if (!dtrace_dif_emulate(pred, mstate, vstate, state))
                        goto next;

                  if (*flags & CPU_DTRACE_FAULT)
                        goto err;
            }

            for (i = 0; i < helper->dtha_nactions; i++) {
                  if (trace)
                        dtrace_helper_trace(helper,
                            mstate, vstate, i + 1);

                  rval = dtrace_dif_emulate(helper->dtha_actions[i],
                      mstate, vstate, state);

                  if (*flags & CPU_DTRACE_FAULT)
                        goto err;
            }

next:
            if (trace)
                  dtrace_helper_trace(helper, mstate, vstate,
                      DTRACE_HELPTRACE_NEXT);
      }

      if (trace)
            dtrace_helper_trace(helper, mstate, vstate,
                DTRACE_HELPTRACE_DONE);

      /*
       * Restore the arg0 that we saved upon entry.
       */
      mstate->dtms_arg[0] = sarg0;
      mstate->dtms_arg[1] = sarg1;

      return (rval);

err:
      if (trace)
            dtrace_helper_trace(helper, mstate, vstate,
                DTRACE_HELPTRACE_ERR);

      /*
       * Restore the arg0 that we saved upon entry.
       */
      mstate->dtms_arg[0] = sarg0;
      mstate->dtms_arg[1] = sarg1;

      return (0);
}

static void
dtrace_helper_action_destroy(dtrace_helper_action_t *helper,
    dtrace_vstate_t *vstate)
{
      int i;

      if (helper->dtha_predicate != NULL)
            dtrace_difo_release(helper->dtha_predicate, vstate);

      for (i = 0; i < helper->dtha_nactions; i++) {
            ASSERT(helper->dtha_actions[i] != NULL);
            dtrace_difo_release(helper->dtha_actions[i], vstate);
      }

      kmem_free(helper->dtha_actions,
          helper->dtha_nactions * sizeof (dtrace_difo_t *));
      kmem_free(helper, sizeof (dtrace_helper_action_t));
}

static int
dtrace_helper_destroygen(int gen)
{
      proc_t *p = curproc;
      dtrace_helpers_t *help = p->p_dtrace_helpers;
      dtrace_vstate_t *vstate;
      int i;

      ASSERT(MUTEX_HELD(&dtrace_lock));

      if (help == NULL || gen > help->dthps_generation)
            return (EINVAL);

      vstate = &help->dthps_vstate;

      for (i = 0; i < DTRACE_NHELPER_ACTIONS; i++) {
            dtrace_helper_action_t *last = NULL, *h, *next;

            for (h = help->dthps_actions[i]; h != NULL; h = next) {
                  next = h->dtha_next;

                  if (h->dtha_generation == gen) {
                        if (last != NULL) {
                              last->dtha_next = next;
                        } else {
                              help->dthps_actions[i] = next;
                        }

                        dtrace_helper_action_destroy(h, vstate);
                  } else {
                        last = h;
                  }
            }
      }

      /*
       * Interate until we've cleared out all helper providers with the
       * given generation number.
       */
      for (;;) {
            dtrace_helper_provider_t *prov;

            /*
             * Look for a helper provider with the right generation. We
             * have to start back at the beginning of the list each time
             * because we drop dtrace_lock. It's unlikely that we'll make
             * more than two passes.
             */
            for (i = 0; i < help->dthps_nprovs; i++) {
                  prov = help->dthps_provs[i];

                  if (prov->dthp_generation == gen)
                        break;
            }

            /*
             * If there were no matches, we're done.
             */
            if (i == help->dthps_nprovs)
                  break;

            /*
             * Move the last helper provider into this slot.
             */
            help->dthps_nprovs--;
            help->dthps_provs[i] = help->dthps_provs[help->dthps_nprovs];
            help->dthps_provs[help->dthps_nprovs] = NULL;

            mutex_exit(&dtrace_lock);

            /*
             * If we have a meta provider, remove this helper provider.
             */
            mutex_enter(&dtrace_meta_lock);
            if (dtrace_meta_pid != NULL) {
                  ASSERT(dtrace_deferred_pid == NULL);
                  dtrace_helper_provider_remove(&prov->dthp_prov,
                      p->p_pid);
            }
            mutex_exit(&dtrace_meta_lock);

            dtrace_helper_provider_destroy(prov);

            mutex_enter(&dtrace_lock);
      }

      return (0);
}
#endif

#if defined(sun)
static int
dtrace_helper_validate(dtrace_helper_action_t *helper)
{
      int err = 0, i;
      dtrace_difo_t *dp;

      if ((dp = helper->dtha_predicate) != NULL)
            err += dtrace_difo_validate_helper(dp);

      for (i = 0; i < helper->dtha_nactions; i++)
            err += dtrace_difo_validate_helper(helper->dtha_actions[i]);

      return (err == 0);
}
#endif

#if defined(sun)
static int
dtrace_helper_action_add(int which, dtrace_ecbdesc_t *ep)
{
      dtrace_helpers_t *help;
      dtrace_helper_action_t *helper, *last;
      dtrace_actdesc_t *act;
      dtrace_vstate_t *vstate;
      dtrace_predicate_t *pred;
      int count = 0, nactions = 0, i;

      if (which < 0 || which >= DTRACE_NHELPER_ACTIONS)
            return (EINVAL);

      help = curproc->p_dtrace_helpers;
      last = help->dthps_actions[which];
      vstate = &help->dthps_vstate;

      for (count = 0; last != NULL; last = last->dtha_next) {
            count++;
            if (last->dtha_next == NULL)
                  break;
      }

      /*
       * If we already have dtrace_helper_actions_max helper actions for this
       * helper action type, we'll refuse to add a new one.
       */
      if (count >= dtrace_helper_actions_max)
            return (ENOSPC);

      helper = kmem_zalloc(sizeof (dtrace_helper_action_t), KM_SLEEP);
      helper->dtha_generation = help->dthps_generation;

      if ((pred = ep->dted_pred.dtpdd_predicate) != NULL) {
            ASSERT(pred->dtp_difo != NULL);
            dtrace_difo_hold(pred->dtp_difo);
            helper->dtha_predicate = pred->dtp_difo;
      }

      for (act = ep->dted_action; act != NULL; act = act->dtad_next) {
            if (act->dtad_kind != DTRACEACT_DIFEXPR)
                  goto err;

            if (act->dtad_difo == NULL)
                  goto err;

            nactions++;
      }

      helper->dtha_actions = kmem_zalloc(sizeof (dtrace_difo_t *) *
          (helper->dtha_nactions = nactions), KM_SLEEP);

      for (act = ep->dted_action, i = 0; act != NULL; act = act->dtad_next) {
            dtrace_difo_hold(act->dtad_difo);
            helper->dtha_actions[i++] = act->dtad_difo;
      }

      if (!dtrace_helper_validate(helper))
            goto err;

      if (last == NULL) {
            help->dthps_actions[which] = helper;
      } else {
            last->dtha_next = helper;
      }

      if (vstate->dtvs_nlocals > dtrace_helptrace_nlocals) {
            dtrace_helptrace_nlocals = vstate->dtvs_nlocals;
            dtrace_helptrace_next = 0;
      }

      return (0);
err:
      dtrace_helper_action_destroy(helper, vstate);
      return (EINVAL);
}

static void
dtrace_helper_provider_register(proc_t *p, dtrace_helpers_t *help,
    dof_helper_t *dofhp)
{
      ASSERT(MUTEX_NOT_HELD(&dtrace_lock));

      mutex_enter(&dtrace_meta_lock);
      mutex_enter(&dtrace_lock);

      if (!dtrace_attached() || dtrace_meta_pid == NULL) {
            /*
             * If the dtrace module is loaded but not attached, or if
             * there aren't isn't a meta provider registered to deal with
             * these provider descriptions, we need to postpone creating
             * the actual providers until later.
             */

            if (help->dthps_next == NULL && help->dthps_prev == NULL &&
                dtrace_deferred_pid != help) {
                  help->dthps_deferred = 1;
                  help->dthps_pid = p->p_pid;
                  help->dthps_next = dtrace_deferred_pid;
                  help->dthps_prev = NULL;
                  if (dtrace_deferred_pid != NULL)
                        dtrace_deferred_pid->dthps_prev = help;
                  dtrace_deferred_pid = help;
            }

            mutex_exit(&dtrace_lock);

      } else if (dofhp != NULL) {
            /*
             * If the dtrace module is loaded and we have a particular
             * helper provider description, pass that off to the
             * meta provider.
             */

            mutex_exit(&dtrace_lock);

            dtrace_helper_provide(dofhp, p->p_pid);

      } else {
            /*
             * Otherwise, just pass all the helper provider descriptions
             * off to the meta provider.
             */

            int i;
            mutex_exit(&dtrace_lock);

            for (i = 0; i < help->dthps_nprovs; i++) {
                  dtrace_helper_provide(&help->dthps_provs[i]->dthp_prov,
                      p->p_pid);
            }
      }

      mutex_exit(&dtrace_meta_lock);
}

static int
dtrace_helper_provider_add(dof_helper_t *dofhp, int gen)
{
      dtrace_helpers_t *help;
      dtrace_helper_provider_t *hprov, **tmp_provs;
      uint_t tmp_maxprovs, i;

      ASSERT(MUTEX_HELD(&dtrace_lock));

      help = curproc->p_dtrace_helpers;
      ASSERT(help != NULL);

      /*
       * If we already have dtrace_helper_providers_max helper providers,
       * we're refuse to add a new one.
       */
      if (help->dthps_nprovs >= dtrace_helper_providers_max)
            return (ENOSPC);

      /*
       * Check to make sure this isn't a duplicate.
       */
      for (i = 0; i < help->dthps_nprovs; i++) {
            if (dofhp->dofhp_addr ==
                help->dthps_provs[i]->dthp_prov.dofhp_addr)
                  return (EALREADY);
      }

      hprov = kmem_zalloc(sizeof (dtrace_helper_provider_t), KM_SLEEP);
      hprov->dthp_prov = *dofhp;
      hprov->dthp_ref = 1;
      hprov->dthp_generation = gen;

      /*
       * Allocate a bigger table for helper providers if it's already full.
       */
      if (help->dthps_maxprovs == help->dthps_nprovs) {
            tmp_maxprovs = help->dthps_maxprovs;
            tmp_provs = help->dthps_provs;

            if (help->dthps_maxprovs == 0)
                  help->dthps_maxprovs = 2;
            else
                  help->dthps_maxprovs *= 2;
            if (help->dthps_maxprovs > dtrace_helper_providers_max)
                  help->dthps_maxprovs = dtrace_helper_providers_max;

            ASSERT(tmp_maxprovs < help->dthps_maxprovs);

            help->dthps_provs = kmem_zalloc(help->dthps_maxprovs *
                sizeof (dtrace_helper_provider_t *), KM_SLEEP);

            if (tmp_provs != NULL) {
                  bcopy(tmp_provs, help->dthps_provs, tmp_maxprovs *
                      sizeof (dtrace_helper_provider_t *));
                  kmem_free(tmp_provs, tmp_maxprovs *
                      sizeof (dtrace_helper_provider_t *));
            }
      }

      help->dthps_provs[help->dthps_nprovs] = hprov;
      help->dthps_nprovs++;

      return (0);
}

static void
dtrace_helper_provider_destroy(dtrace_helper_provider_t *hprov)
{
      mutex_enter(&dtrace_lock);

      if (--hprov->dthp_ref == 0) {
            dof_hdr_t *dof;
            mutex_exit(&dtrace_lock);
            dof = (dof_hdr_t *)(uintptr_t)hprov->dthp_prov.dofhp_dof;
            dtrace_dof_destroy(dof);
            kmem_free(hprov, sizeof (dtrace_helper_provider_t));
      } else {
            mutex_exit(&dtrace_lock);
      }
}

static int
dtrace_helper_provider_validate(dof_hdr_t *dof, dof_sec_t *sec)
{
      uintptr_t daddr = (uintptr_t)dof;
      dof_sec_t *str_sec, *prb_sec, *arg_sec, *off_sec, *enoff_sec;
      dof_provider_t *provider;
      dof_probe_t *probe;
      uint8_t *arg;
      char *strtab, *typestr;
      dof_stridx_t typeidx;
      size_t typesz;
      uint_t nprobes, j, k;

      ASSERT(sec->dofs_type == DOF_SECT_PROVIDER);

      if (sec->dofs_offset & (sizeof (uint_t) - 1)) {
            dtrace_dof_error(dof, "misaligned section offset");
            return (-1);
      }

      /*
       * The section needs to be large enough to contain the DOF provider
       * structure appropriate for the given version.
       */
      if (sec->dofs_size <
          ((dof->dofh_ident[DOF_ID_VERSION] == DOF_VERSION_1) ?
          offsetof(dof_provider_t, dofpv_prenoffs) :
          sizeof (dof_provider_t))) {
            dtrace_dof_error(dof, "provider section too small");
            return (-1);
      }

      provider = (dof_provider_t *)(uintptr_t)(daddr + sec->dofs_offset);
      str_sec = dtrace_dof_sect(dof, DOF_SECT_STRTAB, provider->dofpv_strtab);
      prb_sec = dtrace_dof_sect(dof, DOF_SECT_PROBES, provider->dofpv_probes);
      arg_sec = dtrace_dof_sect(dof, DOF_SECT_PRARGS, provider->dofpv_prargs);
      off_sec = dtrace_dof_sect(dof, DOF_SECT_PROFFS, provider->dofpv_proffs);

      if (str_sec == NULL || prb_sec == NULL ||
          arg_sec == NULL || off_sec == NULL)
            return (-1);

      enoff_sec = NULL;

      if (dof->dofh_ident[DOF_ID_VERSION] != DOF_VERSION_1 &&
          provider->dofpv_prenoffs != DOF_SECT_NONE &&
          (enoff_sec = dtrace_dof_sect(dof, DOF_SECT_PRENOFFS,
          provider->dofpv_prenoffs)) == NULL)
            return (-1);

      strtab = (char *)(uintptr_t)(daddr + str_sec->dofs_offset);

      if (provider->dofpv_name >= str_sec->dofs_size ||
          strlen(strtab + provider->dofpv_name) >= DTRACE_PROVNAMELEN) {
            dtrace_dof_error(dof, "invalid provider name");
            return (-1);
      }

      if (prb_sec->dofs_entsize == 0 ||
          prb_sec->dofs_entsize > prb_sec->dofs_size) {
            dtrace_dof_error(dof, "invalid entry size");
            return (-1);
      }

      if (prb_sec->dofs_entsize & (sizeof (uintptr_t) - 1)) {
            dtrace_dof_error(dof, "misaligned entry size");
            return (-1);
      }

      if (off_sec->dofs_entsize != sizeof (uint32_t)) {
            dtrace_dof_error(dof, "invalid entry size");
            return (-1);
      }

      if (off_sec->dofs_offset & (sizeof (uint32_t) - 1)) {
            dtrace_dof_error(dof, "misaligned section offset");
            return (-1);
      }

      if (arg_sec->dofs_entsize != sizeof (uint8_t)) {
            dtrace_dof_error(dof, "invalid entry size");
            return (-1);
      }

      arg = (uint8_t *)(uintptr_t)(daddr + arg_sec->dofs_offset);

      nprobes = prb_sec->dofs_size / prb_sec->dofs_entsize;

      /*
       * Take a pass through the probes to check for errors.
       */
      for (j = 0; j < nprobes; j++) {
            probe = (dof_probe_t *)(uintptr_t)(daddr +
                prb_sec->dofs_offset + j * prb_sec->dofs_entsize);

            if (probe->dofpr_func >= str_sec->dofs_size) {
                  dtrace_dof_error(dof, "invalid function name");
                  return (-1);
            }

            if (strlen(strtab + probe->dofpr_func) >= DTRACE_FUNCNAMELEN) {
                  dtrace_dof_error(dof, "function name too long");
                  return (-1);
            }

            if (probe->dofpr_name >= str_sec->dofs_size ||
                strlen(strtab + probe->dofpr_name) >= DTRACE_NAMELEN) {
                  dtrace_dof_error(dof, "invalid probe name");
                  return (-1);
            }

            /*
             * The offset count must not wrap the index, and the offsets
             * must also not overflow the section's data.
             */
            if (probe->dofpr_offidx + probe->dofpr_noffs <
                probe->dofpr_offidx ||
                (probe->dofpr_offidx + probe->dofpr_noffs) *
                off_sec->dofs_entsize > off_sec->dofs_size) {
                  dtrace_dof_error(dof, "invalid probe offset");
                  return (-1);
            }

            if (dof->dofh_ident[DOF_ID_VERSION] != DOF_VERSION_1) {
                  /*
                   * If there's no is-enabled offset section, make sure
                   * there aren't any is-enabled offsets. Otherwise
                   * perform the same checks as for probe offsets
                   * (immediately above).
                   */
                  if (enoff_sec == NULL) {
                        if (probe->dofpr_enoffidx != 0 ||
                            probe->dofpr_nenoffs != 0) {
                              dtrace_dof_error(dof, "is-enabled "
                                  "offsets with null section");
                              return (-1);
                        }
                  } else if (probe->dofpr_enoffidx +
                      probe->dofpr_nenoffs < probe->dofpr_enoffidx ||
                      (probe->dofpr_enoffidx + probe->dofpr_nenoffs) *
                      enoff_sec->dofs_entsize > enoff_sec->dofs_size) {
                        dtrace_dof_error(dof, "invalid is-enabled "
                            "offset");
                        return (-1);
                  }

                  if (probe->dofpr_noffs + probe->dofpr_nenoffs == 0) {
                        dtrace_dof_error(dof, "zero probe and "
                            "is-enabled offsets");
                        return (-1);
                  }
            } else if (probe->dofpr_noffs == 0) {
                  dtrace_dof_error(dof, "zero probe offsets");
                  return (-1);
            }

            if (probe->dofpr_argidx + probe->dofpr_xargc <
                probe->dofpr_argidx ||
                (probe->dofpr_argidx + probe->dofpr_xargc) *
                arg_sec->dofs_entsize > arg_sec->dofs_size) {
                  dtrace_dof_error(dof, "invalid args");
                  return (-1);
            }

            typeidx = probe->dofpr_nargv;
            typestr = strtab + probe->dofpr_nargv;
            for (k = 0; k < probe->dofpr_nargc; k++) {
                  if (typeidx >= str_sec->dofs_size) {
                        dtrace_dof_error(dof, "bad "
                            "native argument type");
                        return (-1);
                  }

                  typesz = strlen(typestr) + 1;
                  if (typesz > DTRACE_ARGTYPELEN) {
                        dtrace_dof_error(dof, "native "
                            "argument type too long");
                        return (-1);
                  }
                  typeidx += typesz;
                  typestr += typesz;
            }

            typeidx = probe->dofpr_xargv;
            typestr = strtab + probe->dofpr_xargv;
            for (k = 0; k < probe->dofpr_xargc; k++) {
                  if (arg[probe->dofpr_argidx + k] > probe->dofpr_nargc) {
                        dtrace_dof_error(dof, "bad "
                            "native argument index");
                        return (-1);
                  }

                  if (typeidx >= str_sec->dofs_size) {
                        dtrace_dof_error(dof, "bad "
                            "translated argument type");
                        return (-1);
                  }

                  typesz = strlen(typestr) + 1;
                  if (typesz > DTRACE_ARGTYPELEN) {
                        dtrace_dof_error(dof, "translated argument "
                            "type too long");
                        return (-1);
                  }

                  typeidx += typesz;
                  typestr += typesz;
            }
      }

      return (0);
}

static int
dtrace_helper_slurp(dof_hdr_t *dof, dof_helper_t *dhp)
{
      dtrace_helpers_t *help;
      dtrace_vstate_t *vstate;
      dtrace_enabling_t *enab = NULL;
      int i, gen, rv, nhelpers = 0, nprovs = 0, destroy = 1;
      uintptr_t daddr = (uintptr_t)dof;

      ASSERT(MUTEX_HELD(&dtrace_lock));

      if ((help = curproc->p_dtrace_helpers) == NULL)
            help = dtrace_helpers_create(curproc);

      vstate = &help->dthps_vstate;

      if ((rv = dtrace_dof_slurp(dof, vstate, NULL, &enab,
          dhp != NULL ? dhp->dofhp_addr : 0, B_FALSE)) != 0) {
            dtrace_dof_destroy(dof);
            return (rv);
      }

      /*
       * Look for helper providers and validate their descriptions.
       */
      if (dhp != NULL) {
            for (i = 0; i < dof->dofh_secnum; i++) {
                  dof_sec_t *sec = (dof_sec_t *)(uintptr_t)(daddr +
                      dof->dofh_secoff + i * dof->dofh_secsize);

                  if (sec->dofs_type != DOF_SECT_PROVIDER)
                        continue;

                  if (dtrace_helper_provider_validate(dof, sec) != 0) {
                        dtrace_enabling_destroy(enab);
                        dtrace_dof_destroy(dof);
                        return (-1);
                  }

                  nprovs++;
            }
      }

      /*
       * Now we need to walk through the ECB descriptions in the enabling.
       */
      for (i = 0; i < enab->dten_ndesc; i++) {
            dtrace_ecbdesc_t *ep = enab->dten_desc[i];
            dtrace_probedesc_t *desc = &ep->dted_probe;

            if (strcmp(desc->dtpd_provider, "dtrace") != 0)
                  continue;

            if (strcmp(desc->dtpd_mod, "helper") != 0)
                  continue;

            if (strcmp(desc->dtpd_func, "ustack") != 0)
                  continue;

            if ((rv = dtrace_helper_action_add(DTRACE_HELPER_ACTION_USTACK,
                ep)) != 0) {
                  /*
                   * Adding this helper action failed -- we are now going
                   * to rip out the entire generation and return failure.
                   */
                  (void) dtrace_helper_destroygen(help->dthps_generation);
                  dtrace_enabling_destroy(enab);
                  dtrace_dof_destroy(dof);
                  return (-1);
            }

            nhelpers++;
      }

      if (nhelpers < enab->dten_ndesc)
            dtrace_dof_error(dof, "unmatched helpers");

      gen = help->dthps_generation++;
      dtrace_enabling_destroy(enab);

      if (dhp != NULL && nprovs > 0) {
            dhp->dofhp_dof = (uint64_t)(uintptr_t)dof;
            if (dtrace_helper_provider_add(dhp, gen) == 0) {
                  mutex_exit(&dtrace_lock);
                  dtrace_helper_provider_register(curproc, help, dhp);
                  mutex_enter(&dtrace_lock);

                  destroy = 0;
            }
      }

      if (destroy)
            dtrace_dof_destroy(dof);

      return (gen);
}

static dtrace_helpers_t *
dtrace_helpers_create(proc_t *p)
{
      dtrace_helpers_t *help;

      ASSERT(MUTEX_HELD(&dtrace_lock));
      ASSERT(p->p_dtrace_helpers == NULL);

      help = kmem_zalloc(sizeof (dtrace_helpers_t), KM_SLEEP);
      help->dthps_actions = kmem_zalloc(sizeof (dtrace_helper_action_t *) *
          DTRACE_NHELPER_ACTIONS, KM_SLEEP);

      p->p_dtrace_helpers = help;
      dtrace_helpers++;

      return (help);
}

static void
dtrace_helpers_destroy(void)
{
      dtrace_helpers_t *help;
      dtrace_vstate_t *vstate;
      proc_t *p = curproc;
      int i;

      mutex_enter(&dtrace_lock);

      ASSERT(p->p_dtrace_helpers != NULL);
      ASSERT(dtrace_helpers > 0);

      help = p->p_dtrace_helpers;
      vstate = &help->dthps_vstate;

      /*
       * We're now going to lose the help from this process.
       */
      p->p_dtrace_helpers = NULL;
      dtrace_sync();

      /*
       * Destory the helper actions.
       */
      for (i = 0; i < DTRACE_NHELPER_ACTIONS; i++) {
            dtrace_helper_action_t *h, *next;

            for (h = help->dthps_actions[i]; h != NULL; h = next) {
                  next = h->dtha_next;
                  dtrace_helper_action_destroy(h, vstate);
                  h = next;
            }
      }

      mutex_exit(&dtrace_lock);

      /*
       * Destroy the helper providers.
       */
      if (help->dthps_maxprovs > 0) {
            mutex_enter(&dtrace_meta_lock);
            if (dtrace_meta_pid != NULL) {
                  ASSERT(dtrace_deferred_pid == NULL);

                  for (i = 0; i < help->dthps_nprovs; i++) {
                        dtrace_helper_provider_remove(
                            &help->dthps_provs[i]->dthp_prov, p->p_pid);
                  }
            } else {
                  mutex_enter(&dtrace_lock);
                  ASSERT(help->dthps_deferred == 0 ||
                      help->dthps_next != NULL ||
                      help->dthps_prev != NULL ||
                      help == dtrace_deferred_pid);

                  /*
                   * Remove the helper from the deferred list.
                   */
                  if (help->dthps_next != NULL)
                        help->dthps_next->dthps_prev = help->dthps_prev;
                  if (help->dthps_prev != NULL)
                        help->dthps_prev->dthps_next = help->dthps_next;
                  if (dtrace_deferred_pid == help) {
                        dtrace_deferred_pid = help->dthps_next;
                        ASSERT(help->dthps_prev == NULL);
                  }

                  mutex_exit(&dtrace_lock);
            }

            mutex_exit(&dtrace_meta_lock);

            for (i = 0; i < help->dthps_nprovs; i++) {
                  dtrace_helper_provider_destroy(help->dthps_provs[i]);
            }

            kmem_free(help->dthps_provs, help->dthps_maxprovs *
                sizeof (dtrace_helper_provider_t *));
      }

      mutex_enter(&dtrace_lock);

      dtrace_vstate_fini(&help->dthps_vstate);
      kmem_free(help->dthps_actions,
          sizeof (dtrace_helper_action_t *) * DTRACE_NHELPER_ACTIONS);
      kmem_free(help, sizeof (dtrace_helpers_t));

      --dtrace_helpers;
      mutex_exit(&dtrace_lock);
}

static void
dtrace_helpers_duplicate(proc_t *from, proc_t *to)
{
      dtrace_helpers_t *help, *newhelp;
      dtrace_helper_action_t *helper, *new, *last;
      dtrace_difo_t *dp;
      dtrace_vstate_t *vstate;
      int i, j, sz, hasprovs = 0;

      mutex_enter(&dtrace_lock);
      ASSERT(from->p_dtrace_helpers != NULL);
      ASSERT(dtrace_helpers > 0);

      help = from->p_dtrace_helpers;
      newhelp = dtrace_helpers_create(to);
      ASSERT(to->p_dtrace_helpers != NULL);

      newhelp->dthps_generation = help->dthps_generation;
      vstate = &newhelp->dthps_vstate;

      /*
       * Duplicate the helper actions.
       */
      for (i = 0; i < DTRACE_NHELPER_ACTIONS; i++) {
            if ((helper = help->dthps_actions[i]) == NULL)
                  continue;

            for (last = NULL; helper != NULL; helper = helper->dtha_next) {
                  new = kmem_zalloc(sizeof (dtrace_helper_action_t),
                      KM_SLEEP);
                  new->dtha_generation = helper->dtha_generation;

                  if ((dp = helper->dtha_predicate) != NULL) {
                        dp = dtrace_difo_duplicate(dp, vstate);
                        new->dtha_predicate = dp;
                  }

                  new->dtha_nactions = helper->dtha_nactions;
                  sz = sizeof (dtrace_difo_t *) * new->dtha_nactions;
                  new->dtha_actions = kmem_alloc(sz, KM_SLEEP);

                  for (j = 0; j < new->dtha_nactions; j++) {
                        dtrace_difo_t *dp = helper->dtha_actions[j];

                        ASSERT(dp != NULL);
                        dp = dtrace_difo_duplicate(dp, vstate);
                        new->dtha_actions[j] = dp;
                  }

                  if (last != NULL) {
                        last->dtha_next = new;
                  } else {
                        newhelp->dthps_actions[i] = new;
                  }

                  last = new;
            }
      }

      /*
       * Duplicate the helper providers and register them with the
       * DTrace framework.
       */
      if (help->dthps_nprovs > 0) {
            newhelp->dthps_nprovs = help->dthps_nprovs;
            newhelp->dthps_maxprovs = help->dthps_nprovs;
            newhelp->dthps_provs = kmem_alloc(newhelp->dthps_nprovs *
                sizeof (dtrace_helper_provider_t *), KM_SLEEP);
            for (i = 0; i < newhelp->dthps_nprovs; i++) {
                  newhelp->dthps_provs[i] = help->dthps_provs[i];
                  newhelp->dthps_provs[i]->dthp_ref++;
            }

            hasprovs = 1;
      }

      mutex_exit(&dtrace_lock);

      if (hasprovs)
            dtrace_helper_provider_register(to, newhelp, NULL);
}
#endif

#if defined(sun)
/*
 * DTrace Hook Functions
 */
static void
dtrace_module_loaded(modctl_t *ctl)
{
      dtrace_provider_t *prv;

      mutex_enter(&dtrace_provider_lock);
      mutex_enter(&mod_lock);

      ASSERT(ctl->mod_busy);

      /*
       * We're going to call each providers per-module provide operation
       * specifying only this module.
       */
      for (prv = dtrace_provider; prv != NULL; prv = prv->dtpv_next)
            prv->dtpv_pops.dtps_provide_module(prv->dtpv_arg, ctl);

      mutex_exit(&mod_lock);
      mutex_exit(&dtrace_provider_lock);

      /*
       * If we have any retained enablings, we need to match against them.
       * Enabling probes requires that cpu_lock be held, and we cannot hold
       * cpu_lock here -- it is legal for cpu_lock to be held when loading a
       * module.  (In particular, this happens when loading scheduling
       * classes.)  So if we have any retained enablings, we need to dispatch
       * our task queue to do the match for us.
       */
      mutex_enter(&dtrace_lock);

      if (dtrace_retained == NULL) {
            mutex_exit(&dtrace_lock);
            return;
      }

      (void) taskq_dispatch(dtrace_taskq,
          (task_func_t *)dtrace_enabling_matchall, NULL, TQ_SLEEP);

      mutex_exit(&dtrace_lock);

      /*
       * And now, for a little heuristic sleaze:  in general, we want to
       * match modules as soon as they load.  However, we cannot guarantee
       * this, because it would lead us to the lock ordering violation
       * outlined above.  The common case, of course, is that cpu_lock is
       * _not_ held -- so we delay here for a clock tick, hoping that that's
       * long enough for the task queue to do its work.  If it's not, it's
       * not a serious problem -- it just means that the module that we
       * just loaded may not be immediately instrumentable.
       */
      delay(1);
}

static void
dtrace_module_unloaded(modctl_t *ctl)
{
      dtrace_probe_t template, *probe, *first, *next;
      dtrace_provider_t *prov;

      template.dtpr_mod = ctl->mod_modname;

      mutex_enter(&dtrace_provider_lock);
      mutex_enter(&mod_lock);
      mutex_enter(&dtrace_lock);

      if (dtrace_bymod == NULL) {
            /*
             * The DTrace module is loaded (obviously) but not attached;
             * we don't have any work to do.
             */
            mutex_exit(&dtrace_provider_lock);
            mutex_exit(&mod_lock);
            mutex_exit(&dtrace_lock);
            return;
      }

      for (probe = first = dtrace_hash_lookup(dtrace_bymod, &template);
          probe != NULL; probe = probe->dtpr_nextmod) {
            if (probe->dtpr_ecb != NULL) {
                  mutex_exit(&dtrace_provider_lock);
                  mutex_exit(&mod_lock);
                  mutex_exit(&dtrace_lock);

                  /*
                   * This shouldn't _actually_ be possible -- we're
                   * unloading a module that has an enabled probe in it.
                   * (It's normally up to the provider to make sure that
                   * this can't happen.)  However, because dtps_enable()
                   * doesn't have a failure mode, there can be an
                   * enable/unload race.  Upshot:  we don't want to
                   * assert, but we're not going to disable the
                   * probe, either.
                   */
                  if (dtrace_err_verbose) {
                        cmn_err(CE_WARN, "unloaded module '%s' had "
                            "enabled probes", ctl->mod_modname);
                  }

                  return;
            }
      }

      probe = first;

      for (first = NULL; probe != NULL; probe = next) {
            ASSERT(dtrace_probes[probe->dtpr_id - 1] == probe);

            dtrace_probes[probe->dtpr_id - 1] = NULL;

            next = probe->dtpr_nextmod;
            dtrace_hash_remove(dtrace_bymod, probe);
            dtrace_hash_remove(dtrace_byfunc, probe);
            dtrace_hash_remove(dtrace_byname, probe);

            if (first == NULL) {
                  first = probe;
                  probe->dtpr_nextmod = NULL;
            } else {
                  probe->dtpr_nextmod = first;
                  first = probe;
            }
      }

      /*
       * We've removed all of the module's probes from the hash chains and
       * from the probe array.  Now issue a dtrace_sync() to be sure that
       * everyone has cleared out from any probe array processing.
       */
      dtrace_sync();

      for (probe = first; probe != NULL; probe = first) {
            first = probe->dtpr_nextmod;
            prov = probe->dtpr_provider;
            prov->dtpv_pops.dtps_destroy(prov->dtpv_arg, probe->dtpr_id,
                probe->dtpr_arg);
            kmem_free(probe->dtpr_mod, strlen(probe->dtpr_mod) + 1);
            kmem_free(probe->dtpr_func, strlen(probe->dtpr_func) + 1);
            kmem_free(probe->dtpr_name, strlen(probe->dtpr_name) + 1);
            vmem_free(dtrace_arena, (void *)(uintptr_t)probe->dtpr_id, 1);
            kmem_free(probe, sizeof (dtrace_probe_t));
      }

      mutex_exit(&dtrace_lock);
      mutex_exit(&mod_lock);
      mutex_exit(&dtrace_provider_lock);
}

static void
dtrace_suspend(void)
{
      dtrace_probe_foreach(offsetof(dtrace_pops_t, dtps_suspend));
}

static void
dtrace_resume(void)
{
      dtrace_probe_foreach(offsetof(dtrace_pops_t, dtps_resume));
}
#endif

static int
dtrace_cpu_setup(cpu_setup_t what, processorid_t cpu)
{
      ASSERT(MUTEX_HELD(&cpu_lock));
      mutex_enter(&dtrace_lock);

      switch (what) {
      case CPU_CONFIG: {
            dtrace_state_t *state;
            dtrace_optval_t *opt, rs, c;

            /*
             * For now, we only allocate a new buffer for anonymous state.
             */
            if ((state = dtrace_anon.dta_state) == NULL)
                  break;

            if (state->dts_activity != DTRACE_ACTIVITY_ACTIVE)
                  break;

            opt = state->dts_options;
            c = opt[DTRACEOPT_CPU];

            if (c != DTRACE_CPUALL && c != DTRACEOPT_UNSET && c != cpu)
                  break;

            /*
             * Regardless of what the actual policy is, we're going to
             * temporarily set our resize policy to be manual.  We're
             * also going to temporarily set our CPU option to denote
             * the newly configured CPU.
             */
            rs = opt[DTRACEOPT_BUFRESIZE];
            opt[DTRACEOPT_BUFRESIZE] = DTRACEOPT_BUFRESIZE_MANUAL;
            opt[DTRACEOPT_CPU] = (dtrace_optval_t)cpu;

            (void) dtrace_state_buffers(state);

            opt[DTRACEOPT_BUFRESIZE] = rs;
            opt[DTRACEOPT_CPU] = c;

            break;
      }

      case CPU_UNCONFIG:
            /*
             * We don't free the buffer in the CPU_UNCONFIG case.  (The
             * buffer will be freed when the consumer exits.)
             */
            break;

      default:
            break;
      }

      mutex_exit(&dtrace_lock);
      return (0);
}

#if defined(sun)
static void
dtrace_cpu_setup_initial(processorid_t cpu)
{
      (void) dtrace_cpu_setup(CPU_CONFIG, cpu);
}
#endif

static void
dtrace_toxrange_add(uintptr_t base, uintptr_t limit)
{
      if (dtrace_toxranges >= dtrace_toxranges_max) {
            int osize, nsize;
            dtrace_toxrange_t *range;

            osize = dtrace_toxranges_max * sizeof (dtrace_toxrange_t);

            if (osize == 0) {
                  ASSERT(dtrace_toxrange == NULL);
                  ASSERT(dtrace_toxranges_max == 0);
                  dtrace_toxranges_max = 1;
            } else {
                  dtrace_toxranges_max <<= 1;
            }

            nsize = dtrace_toxranges_max * sizeof (dtrace_toxrange_t);
            range = kmem_zalloc(nsize, KM_SLEEP);

            if (dtrace_toxrange != NULL) {
                  ASSERT(osize != 0);
                  bcopy(dtrace_toxrange, range, osize);
                  kmem_free(dtrace_toxrange, osize);
            }

            dtrace_toxrange = range;
      }

      ASSERT(dtrace_toxrange[dtrace_toxranges].dtt_base == 0);
      ASSERT(dtrace_toxrange[dtrace_toxranges].dtt_limit == 0);

      dtrace_toxrange[dtrace_toxranges].dtt_base = base;
      dtrace_toxrange[dtrace_toxranges].dtt_limit = limit;
      dtrace_toxranges++;
}

/*
 * DTrace Driver Cookbook Functions
 */
#if defined(sun)
/*ARGSUSED*/
static int
dtrace_attach(dev_info_t *devi, ddi_attach_cmd_t cmd)
{
      dtrace_provider_id_t id;
      dtrace_state_t *state = NULL;
      dtrace_enabling_t *enab;

      mutex_enter(&cpu_lock);
      mutex_enter(&dtrace_provider_lock);
      mutex_enter(&dtrace_lock);

      if (ddi_soft_state_init(&dtrace_softstate,
          sizeof (dtrace_state_t), 0) != 0) {
            cmn_err(CE_NOTE, "/dev/dtrace failed to initialize soft state");
            mutex_exit(&cpu_lock);
            mutex_exit(&dtrace_provider_lock);
            mutex_exit(&dtrace_lock);
            return (DDI_FAILURE);
      }

      if (ddi_create_minor_node(devi, DTRACEMNR_DTRACE, S_IFCHR,
          DTRACEMNRN_DTRACE, DDI_PSEUDO, NULL) == DDI_FAILURE ||
          ddi_create_minor_node(devi, DTRACEMNR_HELPER, S_IFCHR,
          DTRACEMNRN_HELPER, DDI_PSEUDO, NULL) == DDI_FAILURE) {
            cmn_err(CE_NOTE, "/dev/dtrace couldn't create minor nodes");
            ddi_remove_minor_node(devi, NULL);
            ddi_soft_state_fini(&dtrace_softstate);
            mutex_exit(&cpu_lock);
            mutex_exit(&dtrace_provider_lock);
            mutex_exit(&dtrace_lock);
            return (DDI_FAILURE);
      }

      ddi_report_dev(devi);
      dtrace_devi = devi;

      dtrace_modload = dtrace_module_loaded;
      dtrace_modunload = dtrace_module_unloaded;
      dtrace_cpu_init = dtrace_cpu_setup_initial;
      dtrace_helpers_cleanup = dtrace_helpers_destroy;
      dtrace_helpers_fork = dtrace_helpers_duplicate;
      dtrace_cpustart_init = dtrace_suspend;
      dtrace_cpustart_fini = dtrace_resume;
      dtrace_debugger_init = dtrace_suspend;
      dtrace_debugger_fini = dtrace_resume;

      register_cpu_setup_func((cpu_setup_func_t *)dtrace_cpu_setup, NULL);

      ASSERT(MUTEX_HELD(&cpu_lock));

      dtrace_arena = vmem_create("dtrace", (void *)1, UINT32_MAX, 1,
          NULL, NULL, NULL, 0, VM_SLEEP | VMC_IDENTIFIER);
      dtrace_minor = vmem_create("dtrace_minor", (void *)DTRACEMNRN_CLONE,
          UINT32_MAX - DTRACEMNRN_CLONE, 1, NULL, NULL, NULL, 0,
          VM_SLEEP | VMC_IDENTIFIER);
      dtrace_taskq = taskq_create("dtrace_taskq", 1, maxclsyspri,
          1, INT_MAX, 0);

      dtrace_state_cache = kmem_cache_create("dtrace_state_cache",
          sizeof (dtrace_dstate_percpu_t) * NCPU, DTRACE_STATE_ALIGN,
          NULL, NULL, NULL, NULL, NULL, 0);

      ASSERT(MUTEX_HELD(&cpu_lock));
      dtrace_bymod = dtrace_hash_create(offsetof(dtrace_probe_t, dtpr_mod),
          offsetof(dtrace_probe_t, dtpr_nextmod),
          offsetof(dtrace_probe_t, dtpr_prevmod));

      dtrace_byfunc = dtrace_hash_create(offsetof(dtrace_probe_t, dtpr_func),
          offsetof(dtrace_probe_t, dtpr_nextfunc),
          offsetof(dtrace_probe_t, dtpr_prevfunc));

      dtrace_byname = dtrace_hash_create(offsetof(dtrace_probe_t, dtpr_name),
          offsetof(dtrace_probe_t, dtpr_nextname),
          offsetof(dtrace_probe_t, dtpr_prevname));

      if (dtrace_retain_max < 1) {
            cmn_err(CE_WARN, "illegal value (%lu) for dtrace_retain_max; "
                "setting to 1", dtrace_retain_max);
            dtrace_retain_max = 1;
      }

      /*
       * Now discover our toxic ranges.
       */
      dtrace_toxic_ranges(dtrace_toxrange_add);

      /*
       * Before we register ourselves as a provider to our own framework,
       * we would like to assert that dtrace_provider is NULL -- but that's
       * not true if we were loaded as a dependency of a DTrace provider.
       * Once we've registered, we can assert that dtrace_provider is our
       * pseudo provider.
       */
      (void) dtrace_register("dtrace", &dtrace_provider_attr,
          DTRACE_PRIV_NONE, 0, &dtrace_provider_ops, NULL, &id);

      ASSERT(dtrace_provider != NULL);
      ASSERT((dtrace_provider_id_t)dtrace_provider == id);

      dtrace_probeid_begin = dtrace_probe_create((dtrace_provider_id_t)
          dtrace_provider, NULL, NULL, "BEGIN", 0, NULL);
      dtrace_probeid_end = dtrace_probe_create((dtrace_provider_id_t)
          dtrace_provider, NULL, NULL, "END", 0, NULL);
      dtrace_probeid_error = dtrace_probe_create((dtrace_provider_id_t)
          dtrace_provider, NULL, NULL, "ERROR", 1, NULL);

      dtrace_anon_property();
      mutex_exit(&cpu_lock);

      /*
       * If DTrace helper tracing is enabled, we need to allocate the
       * trace buffer and initialize the values.
       */
      if (dtrace_helptrace_enabled) {
            ASSERT(dtrace_helptrace_buffer == NULL);
            dtrace_helptrace_buffer =
                kmem_zalloc(dtrace_helptrace_bufsize, KM_SLEEP);
            dtrace_helptrace_next = 0;
      }

      /*
       * If there are already providers, we must ask them to provide their
       * probes, and then match any anonymous enabling against them.  Note
       * that there should be no other retained enablings at this time:
       * the only retained enablings at this time should be the anonymous
       * enabling.
       */
      if (dtrace_anon.dta_enabling != NULL) {
            ASSERT(dtrace_retained == dtrace_anon.dta_enabling);

            dtrace_enabling_provide(NULL);
            state = dtrace_anon.dta_state;

            /*
             * We couldn't hold cpu_lock across the above call to
             * dtrace_enabling_provide(), but we must hold it to actually
             * enable the probes.  We have to drop all of our locks, pick
             * up cpu_lock, and regain our locks before matching the
             * retained anonymous enabling.
             */
            mutex_exit(&dtrace_lock);
            mutex_exit(&dtrace_provider_lock);

            mutex_enter(&cpu_lock);
            mutex_enter(&dtrace_provider_lock);
            mutex_enter(&dtrace_lock);

            if ((enab = dtrace_anon.dta_enabling) != NULL)
                  (void) dtrace_enabling_match(enab, NULL);

            mutex_exit(&cpu_lock);
      }

      mutex_exit(&dtrace_lock);
      mutex_exit(&dtrace_provider_lock);

      if (state != NULL) {
            /*
             * If we created any anonymous state, set it going now.
             */
            (void) dtrace_state_go(state, &dtrace_anon.dta_beganon);
      }

      return (DDI_SUCCESS);
}
#endif

#if !defined(sun)
#if __FreeBSD_version >= 800039
static void
dtrace_dtr(void *data __unused)
{
}
#endif
#endif

/*ARGSUSED*/
static int
#if defined(sun)
dtrace_open(dev_t *devp, int flag, int otyp, cred_t *cred_p)
#else
dtrace_open(struct cdev *dev, int oflags, int devtype, struct thread *td)
#endif
{
      dtrace_state_t *state;
      uint32_t priv;
      uid_t uid;
      zoneid_t zoneid;

#if defined(sun)
      if (getminor(*devp) == DTRACEMNRN_HELPER)
            return (0);

      /*
       * If this wasn't an open with the "helper" minor, then it must be
       * the "dtrace" minor.
       */
      ASSERT(getminor(*devp) == DTRACEMNRN_DTRACE);
#else
      cred_t *cred_p = NULL;

#if __FreeBSD_version < 800039
      /*
       * The first minor device is the one that is cloned so there is
       * nothing more to do here.
       */
      if (dev2unit(dev) == 0)
            return 0;

      /*
       * Devices are cloned, so if the DTrace state has already
       * been allocated, that means this device belongs to a
       * different client. Each client should open '/dev/dtrace'
       * to get a cloned device.
       */
      if (dev->si_drv1 != NULL)
            return (EBUSY);
#endif

      cred_p = dev->si_cred;
#endif

      /*
       * If no DTRACE_PRIV_* bits are set in the credential, then the
       * caller lacks sufficient permission to do anything with DTrace.
       */
      dtrace_cred2priv(cred_p, &priv, &uid, &zoneid);
      if (priv == DTRACE_PRIV_NONE) {
#if !defined(sun)
#if __FreeBSD_version < 800039
            /* Destroy the cloned device. */
                destroy_dev(dev);
#endif
#endif

            return (EACCES);
      }

      /*
       * Ask all providers to provide all their probes.
       */
      mutex_enter(&dtrace_provider_lock);
      dtrace_probe_provide(NULL, NULL);
      mutex_exit(&dtrace_provider_lock);

      mutex_enter(&cpu_lock);
      mutex_enter(&dtrace_lock);
      dtrace_opens++;
      dtrace_membar_producer();

#if defined(sun)
      /*
       * If the kernel debugger is active (that is, if the kernel debugger
       * modified text in some way), we won't allow the open.
       */
      if (kdi_dtrace_set(KDI_DTSET_DTRACE_ACTIVATE) != 0) {
            dtrace_opens--;
            mutex_exit(&cpu_lock);
            mutex_exit(&dtrace_lock);
            return (EBUSY);
      }

      state = dtrace_state_create(devp, cred_p);
#else
      state = dtrace_state_create(dev);
#if __FreeBSD_version < 800039
      dev->si_drv1 = state;
#else
      devfs_set_cdevpriv(state, dtrace_dtr);
#endif
#endif

      mutex_exit(&cpu_lock);

      if (state == NULL) {
#if defined(sun)
            if (--dtrace_opens == 0)
                  (void) kdi_dtrace_set(KDI_DTSET_DTRACE_DEACTIVATE);
#else
            --dtrace_opens;
#endif
            mutex_exit(&dtrace_lock);
#if !defined(sun)
#if __FreeBSD_version < 800039
            /* Destroy the cloned device. */
                destroy_dev(dev);
#endif
#endif
            return (EAGAIN);
      }

      mutex_exit(&dtrace_lock);

      return (0);
}

/*ARGSUSED*/
static int
#if defined(sun)
dtrace_close(dev_t dev, int flag, int otyp, cred_t *cred_p)
#else
dtrace_close(struct cdev *dev, int flags, int fmt __unused, struct thread *td)
#endif
{
#if defined(sun)
      minor_t minor = getminor(dev);
      dtrace_state_t *state;

      if (minor == DTRACEMNRN_HELPER)
            return (0);

      state = ddi_get_soft_state(dtrace_softstate, minor);
#else
#if __FreeBSD_version < 800039
      dtrace_state_t *state = dev->si_drv1;

      /* Check if this is not a cloned device. */
      if (dev2unit(dev) == 0)
            return (0);
#else
      dtrace_state_t *state;
      devfs_get_cdevpriv((void **) &state);
#endif

#endif

      mutex_enter(&cpu_lock);
      mutex_enter(&dtrace_lock);

      if (state != NULL) {
            if (state->dts_anon) {
                  /*
                   * There is anonymous state. Destroy that first.
                   */
                  ASSERT(dtrace_anon.dta_state == NULL);
                  dtrace_state_destroy(state->dts_anon);
            }

            dtrace_state_destroy(state);

#if !defined(sun)
            kmem_free(state, 0);
#if __FreeBSD_version < 800039
            dev->si_drv1 = NULL;
#else
            devfs_clear_cdevpriv();
#endif
#endif
      }

      ASSERT(dtrace_opens > 0);
#if defined(sun)
      if (--dtrace_opens == 0)
            (void) kdi_dtrace_set(KDI_DTSET_DTRACE_DEACTIVATE);
#else
      --dtrace_opens;
#endif

      mutex_exit(&dtrace_lock);
      mutex_exit(&cpu_lock);

#if __FreeBSD_version < 800039
      /* Schedule this cloned device to be destroyed. */
      destroy_dev_sched(dev);
#endif

      return (0);
}

#if defined(sun)
/*ARGSUSED*/
static int
dtrace_ioctl_helper(int cmd, intptr_t arg, int *rv)
{
      int rval;
      dof_helper_t help, *dhp = NULL;

      switch (cmd) {
      case DTRACEHIOC_ADDDOF:
            if (copyin((void *)arg, &help, sizeof (help)) != 0) {
                  dtrace_dof_error(NULL, "failed to copyin DOF helper");
                  return (EFAULT);
            }

            dhp = &help;
            arg = (intptr_t)help.dofhp_dof;
            /*FALLTHROUGH*/

      case DTRACEHIOC_ADD: {
            dof_hdr_t *dof = dtrace_dof_copyin(arg, &rval);

            if (dof == NULL)
                  return (rval);

            mutex_enter(&dtrace_lock);

            /*
             * dtrace_helper_slurp() takes responsibility for the dof --
             * it may free it now or it may save it and free it later.
             */
            if ((rval = dtrace_helper_slurp(dof, dhp)) != -1) {
                  *rv = rval;
                  rval = 0;
            } else {
                  rval = EINVAL;
            }

            mutex_exit(&dtrace_lock);
            return (rval);
      }

      case DTRACEHIOC_REMOVE: {
            mutex_enter(&dtrace_lock);
            rval = dtrace_helper_destroygen(arg);
            mutex_exit(&dtrace_lock);

            return (rval);
      }

      default:
            break;
      }

      return (ENOTTY);
}

/*ARGSUSED*/
static int
dtrace_ioctl(dev_t dev, int cmd, intptr_t arg, int md, cred_t *cr, int *rv)
{
      minor_t minor = getminor(dev);
      dtrace_state_t *state;
      int rval;

      if (minor == DTRACEMNRN_HELPER)
            return (dtrace_ioctl_helper(cmd, arg, rv));

      state = ddi_get_soft_state(dtrace_softstate, minor);

      if (state->dts_anon) {
            ASSERT(dtrace_anon.dta_state == NULL);
            state = state->dts_anon;
      }

      switch (cmd) {
      case DTRACEIOC_PROVIDER: {
            dtrace_providerdesc_t pvd;
            dtrace_provider_t *pvp;

            if (copyin((void *)arg, &pvd, sizeof (pvd)) != 0)
                  return (EFAULT);

            pvd.dtvd_name[DTRACE_PROVNAMELEN - 1] = '\0';
            mutex_enter(&dtrace_provider_lock);

            for (pvp = dtrace_provider; pvp != NULL; pvp = pvp->dtpv_next) {
                  if (strcmp(pvp->dtpv_name, pvd.dtvd_name) == 0)
                        break;
            }

            mutex_exit(&dtrace_provider_lock);

            if (pvp == NULL)
                  return (ESRCH);

            bcopy(&pvp->dtpv_priv, &pvd.dtvd_priv, sizeof (dtrace_ppriv_t));
            bcopy(&pvp->dtpv_attr, &pvd.dtvd_attr, sizeof (dtrace_pattr_t));

            if (copyout(&pvd, (void *)arg, sizeof (pvd)) != 0)
                  return (EFAULT);

            return (0);
      }

      case DTRACEIOC_EPROBE: {
            dtrace_eprobedesc_t epdesc;
            dtrace_ecb_t *ecb;
            dtrace_action_t *act;
            void *buf;
            size_t size;
            uintptr_t dest;
            int nrecs;

            if (copyin((void *)arg, &epdesc, sizeof (epdesc)) != 0)
                  return (EFAULT);

            mutex_enter(&dtrace_lock);

            if ((ecb = dtrace_epid2ecb(state, epdesc.dtepd_epid)) == NULL) {
                  mutex_exit(&dtrace_lock);
                  return (EINVAL);
            }

            if (ecb->dte_probe == NULL) {
                  mutex_exit(&dtrace_lock);
                  return (EINVAL);
            }

            epdesc.dtepd_probeid = ecb->dte_probe->dtpr_id;
            epdesc.dtepd_uarg = ecb->dte_uarg;
            epdesc.dtepd_size = ecb->dte_size;

            nrecs = epdesc.dtepd_nrecs;
            epdesc.dtepd_nrecs = 0;
            for (act = ecb->dte_action; act != NULL; act = act->dta_next) {
                  if (DTRACEACT_ISAGG(act->dta_kind) || act->dta_intuple)
                        continue;

                  epdesc.dtepd_nrecs++;
            }

            /*
             * Now that we have the size, we need to allocate a temporary
             * buffer in which to store the complete description.  We need
             * the temporary buffer to be able to drop dtrace_lock()
             * across the copyout(), below.
             */
            size = sizeof (dtrace_eprobedesc_t) +
                (epdesc.dtepd_nrecs * sizeof (dtrace_recdesc_t));

            buf = kmem_alloc(size, KM_SLEEP);
            dest = (uintptr_t)buf;

            bcopy(&epdesc, (void *)dest, sizeof (epdesc));
            dest += offsetof(dtrace_eprobedesc_t, dtepd_rec[0]);

            for (act = ecb->dte_action; act != NULL; act = act->dta_next) {
                  if (DTRACEACT_ISAGG(act->dta_kind) || act->dta_intuple)
                        continue;

                  if (nrecs-- == 0)
                        break;

                  bcopy(&act->dta_rec, (void *)dest,
                      sizeof (dtrace_recdesc_t));
                  dest += sizeof (dtrace_recdesc_t);
            }

            mutex_exit(&dtrace_lock);

            if (copyout(buf, (void *)arg, dest - (uintptr_t)buf) != 0) {
                  kmem_free(buf, size);
                  return (EFAULT);
            }

            kmem_free(buf, size);
            return (0);
      }

      case DTRACEIOC_AGGDESC: {
            dtrace_aggdesc_t aggdesc;
            dtrace_action_t *act;
            dtrace_aggregation_t *agg;
            int nrecs;
            uint32_t offs;
            dtrace_recdesc_t *lrec;
            void *buf;
            size_t size;
            uintptr_t dest;

            if (copyin((void *)arg, &aggdesc, sizeof (aggdesc)) != 0)
                  return (EFAULT);

            mutex_enter(&dtrace_lock);

            if ((agg = dtrace_aggid2agg(state, aggdesc.dtagd_id)) == NULL) {
                  mutex_exit(&dtrace_lock);
                  return (EINVAL);
            }

            aggdesc.dtagd_epid = agg->dtag_ecb->dte_epid;

            nrecs = aggdesc.dtagd_nrecs;
            aggdesc.dtagd_nrecs = 0;

            offs = agg->dtag_base;
            lrec = &agg->dtag_action.dta_rec;
            aggdesc.dtagd_size = lrec->dtrd_offset + lrec->dtrd_size - offs;

            for (act = agg->dtag_first; ; act = act->dta_next) {
                  ASSERT(act->dta_intuple ||
                      DTRACEACT_ISAGG(act->dta_kind));

                  /*
                   * If this action has a record size of zero, it
                   * denotes an argument to the aggregating action.
                   * Because the presence of this record doesn't (or
                   * shouldn't) affect the way the data is interpreted,
                   * we don't copy it out to save user-level the
                   * confusion of dealing with a zero-length record.
                   */
                  if (act->dta_rec.dtrd_size == 0) {
                        ASSERT(agg->dtag_hasarg);
                        continue;
                  }

                  aggdesc.dtagd_nrecs++;

                  if (act == &agg->dtag_action)
                        break;
            }

            /*
             * Now that we have the size, we need to allocate a temporary
             * buffer in which to store the complete description.  We need
             * the temporary buffer to be able to drop dtrace_lock()
             * across the copyout(), below.
             */
            size = sizeof (dtrace_aggdesc_t) +
                (aggdesc.dtagd_nrecs * sizeof (dtrace_recdesc_t));

            buf = kmem_alloc(size, KM_SLEEP);
            dest = (uintptr_t)buf;

            bcopy(&aggdesc, (void *)dest, sizeof (aggdesc));
            dest += offsetof(dtrace_aggdesc_t, dtagd_rec[0]);

            for (act = agg->dtag_first; ; act = act->dta_next) {
                  dtrace_recdesc_t rec = act->dta_rec;

                  /*
                   * See the comment in the above loop for why we pass
                   * over zero-length records.
                   */
                  if (rec.dtrd_size == 0) {
                        ASSERT(agg->dtag_hasarg);
                        continue;
                  }

                  if (nrecs-- == 0)
                        break;

                  rec.dtrd_offset -= offs;
                  bcopy(&rec, (void *)dest, sizeof (rec));
                  dest += sizeof (dtrace_recdesc_t);

                  if (act == &agg->dtag_action)
                        break;
            }

            mutex_exit(&dtrace_lock);

            if (copyout(buf, (void *)arg, dest - (uintptr_t)buf) != 0) {
                  kmem_free(buf, size);
                  return (EFAULT);
            }

            kmem_free(buf, size);
            return (0);
      }

      case DTRACEIOC_ENABLE: {
            dof_hdr_t *dof;
            dtrace_enabling_t *enab = NULL;
            dtrace_vstate_t *vstate;
            int err = 0;

            *rv = 0;

            /*
             * If a NULL argument has been passed, we take this as our
             * cue to reevaluate our enablings.
             */
            if (arg == NULL) {
                  dtrace_enabling_matchall();

                  return (0);
            }

            if ((dof = dtrace_dof_copyin(arg, &rval)) == NULL)
                  return (rval);

            mutex_enter(&cpu_lock);
            mutex_enter(&dtrace_lock);
            vstate = &state->dts_vstate;

            if (state->dts_activity != DTRACE_ACTIVITY_INACTIVE) {
                  mutex_exit(&dtrace_lock);
                  mutex_exit(&cpu_lock);
                  dtrace_dof_destroy(dof);
                  return (EBUSY);
            }

            if (dtrace_dof_slurp(dof, vstate, cr, &enab, 0, B_TRUE) != 0) {
                  mutex_exit(&dtrace_lock);
                  mutex_exit(&cpu_lock);
                  dtrace_dof_destroy(dof);
                  return (EINVAL);
            }

            if ((rval = dtrace_dof_options(dof, state)) != 0) {
                  dtrace_enabling_destroy(enab);
                  mutex_exit(&dtrace_lock);
                  mutex_exit(&cpu_lock);
                  dtrace_dof_destroy(dof);
                  return (rval);
            }

            if ((err = dtrace_enabling_match(enab, rv)) == 0) {
                  err = dtrace_enabling_retain(enab);
            } else {
                  dtrace_enabling_destroy(enab);
            }

            mutex_exit(&cpu_lock);
            mutex_exit(&dtrace_lock);
            dtrace_dof_destroy(dof);

            return (err);
      }

      case DTRACEIOC_REPLICATE: {
            dtrace_repldesc_t desc;
            dtrace_probedesc_t *match = &desc.dtrpd_match;
            dtrace_probedesc_t *create = &desc.dtrpd_create;
            int err;

            if (copyin((void *)arg, &desc, sizeof (desc)) != 0)
                  return (EFAULT);

            match->dtpd_provider[DTRACE_PROVNAMELEN - 1] = '\0';
            match->dtpd_mod[DTRACE_MODNAMELEN - 1] = '\0';
            match->dtpd_func[DTRACE_FUNCNAMELEN - 1] = '\0';
            match->dtpd_name[DTRACE_NAMELEN - 1] = '\0';

            create->dtpd_provider[DTRACE_PROVNAMELEN - 1] = '\0';
            create->dtpd_mod[DTRACE_MODNAMELEN - 1] = '\0';
            create->dtpd_func[DTRACE_FUNCNAMELEN - 1] = '\0';
            create->dtpd_name[DTRACE_NAMELEN - 1] = '\0';

            mutex_enter(&dtrace_lock);
            err = dtrace_enabling_replicate(state, match, create);
            mutex_exit(&dtrace_lock);

            return (err);
      }

      case DTRACEIOC_PROBEMATCH:
      case DTRACEIOC_PROBES: {
            dtrace_probe_t *probe = NULL;
            dtrace_probedesc_t desc;
            dtrace_probekey_t pkey;
            dtrace_id_t i;
            int m = 0;
            uint32_t priv;
            uid_t uid;
            zoneid_t zoneid;

            if (copyin((void *)arg, &desc, sizeof (desc)) != 0)
                  return (EFAULT);

            desc.dtpd_provider[DTRACE_PROVNAMELEN - 1] = '\0';
            desc.dtpd_mod[DTRACE_MODNAMELEN - 1] = '\0';
            desc.dtpd_func[DTRACE_FUNCNAMELEN - 1] = '\0';
            desc.dtpd_name[DTRACE_NAMELEN - 1] = '\0';

            /*
             * Before we attempt to match this probe, we want to give
             * all providers the opportunity to provide it.
             */
            if (desc.dtpd_id == DTRACE_IDNONE) {
                  mutex_enter(&dtrace_provider_lock);
                  dtrace_probe_provide(&desc, NULL);
                  mutex_exit(&dtrace_provider_lock);
                  desc.dtpd_id++;
            }

            if (cmd == DTRACEIOC_PROBEMATCH)  {
                  dtrace_probekey(&desc, &pkey);
                  pkey.dtpk_id = DTRACE_IDNONE;
            }

            dtrace_cred2priv(cr, &priv, &uid, &zoneid);

            mutex_enter(&dtrace_lock);

            if (cmd == DTRACEIOC_PROBEMATCH) {
                  for (i = desc.dtpd_id; i <= dtrace_nprobes; i++) {
                        if ((probe = dtrace_probes[i - 1]) != NULL &&
                            (m = dtrace_match_probe(probe, &pkey,
                            priv, uid, zoneid)) != 0)
                              break;
                  }

                  if (m < 0) {
                        mutex_exit(&dtrace_lock);
                        return (EINVAL);
                  }

            } else {
                  for (i = desc.dtpd_id; i <= dtrace_nprobes; i++) {
                        if ((probe = dtrace_probes[i - 1]) != NULL &&
                            dtrace_match_priv(probe, priv, uid, zoneid))
                              break;
                  }
            }

            if (probe == NULL) {
                  mutex_exit(&dtrace_lock);
                  return (ESRCH);
            }

            dtrace_probe_description(probe, &desc);
            mutex_exit(&dtrace_lock);

            if (copyout(&desc, (void *)arg, sizeof (desc)) != 0)
                  return (EFAULT);

            return (0);
      }

      case DTRACEIOC_PROBEARG: {
            dtrace_argdesc_t desc;
            dtrace_probe_t *probe;
            dtrace_provider_t *prov;

            if (copyin((void *)arg, &desc, sizeof (desc)) != 0)
                  return (EFAULT);

            if (desc.dtargd_id == DTRACE_IDNONE)
                  return (EINVAL);

            if (desc.dtargd_ndx == DTRACE_ARGNONE)
                  return (EINVAL);

            mutex_enter(&dtrace_provider_lock);
            mutex_enter(&mod_lock);
            mutex_enter(&dtrace_lock);

            if (desc.dtargd_id > dtrace_nprobes) {
                  mutex_exit(&dtrace_lock);
                  mutex_exit(&mod_lock);
                  mutex_exit(&dtrace_provider_lock);
                  return (EINVAL);
            }

            if ((probe = dtrace_probes[desc.dtargd_id - 1]) == NULL) {
                  mutex_exit(&dtrace_lock);
                  mutex_exit(&mod_lock);
                  mutex_exit(&dtrace_provider_lock);
                  return (EINVAL);
            }

            mutex_exit(&dtrace_lock);

            prov = probe->dtpr_provider;

            if (prov->dtpv_pops.dtps_getargdesc == NULL) {
                  /*
                   * There isn't any typed information for this probe.
                   * Set the argument number to DTRACE_ARGNONE.
                   */
                  desc.dtargd_ndx = DTRACE_ARGNONE;
            } else {
                  desc.dtargd_native[0] = '\0';
                  desc.dtargd_xlate[0] = '\0';
                  desc.dtargd_mapping = desc.dtargd_ndx;

                  prov->dtpv_pops.dtps_getargdesc(prov->dtpv_arg,
                      probe->dtpr_id, probe->dtpr_arg, &desc);
            }

            mutex_exit(&mod_lock);
            mutex_exit(&dtrace_provider_lock);

            if (copyout(&desc, (void *)arg, sizeof (desc)) != 0)
                  return (EFAULT);

            return (0);
      }

      case DTRACEIOC_GO: {
            processorid_t cpuid;
            rval = dtrace_state_go(state, &cpuid);

            if (rval != 0)
                  return (rval);

            if (copyout(&cpuid, (void *)arg, sizeof (cpuid)) != 0)
                  return (EFAULT);

            return (0);
      }

      case DTRACEIOC_STOP: {
            processorid_t cpuid;

            mutex_enter(&dtrace_lock);
            rval = dtrace_state_stop(state, &cpuid);
            mutex_exit(&dtrace_lock);

            if (rval != 0)
                  return (rval);

            if (copyout(&cpuid, (void *)arg, sizeof (cpuid)) != 0)
                  return (EFAULT);

            return (0);
      }

      case DTRACEIOC_DOFGET: {
            dof_hdr_t hdr, *dof;
            uint64_t len;

            if (copyin((void *)arg, &hdr, sizeof (hdr)) != 0)
                  return (EFAULT);

            mutex_enter(&dtrace_lock);
            dof = dtrace_dof_create(state);
            mutex_exit(&dtrace_lock);

            len = MIN(hdr.dofh_loadsz, dof->dofh_loadsz);
            rval = copyout(dof, (void *)arg, len);
            dtrace_dof_destroy(dof);

            return (rval == 0 ? 0 : EFAULT);
      }

      case DTRACEIOC_AGGSNAP:
      case DTRACEIOC_BUFSNAP: {
            dtrace_bufdesc_t desc;
            caddr_t cached;
            dtrace_buffer_t *buf;

            if (copyin((void *)arg, &desc, sizeof (desc)) != 0)
                  return (EFAULT);

            if (desc.dtbd_cpu < 0 || desc.dtbd_cpu >= NCPU)
                  return (EINVAL);

            mutex_enter(&dtrace_lock);

            if (cmd == DTRACEIOC_BUFSNAP) {
                  buf = &state->dts_buffer[desc.dtbd_cpu];
            } else {
                  buf = &state->dts_aggbuffer[desc.dtbd_cpu];
            }

            if (buf->dtb_flags & (DTRACEBUF_RING | DTRACEBUF_FILL)) {
                  size_t sz = buf->dtb_offset;

                  if (state->dts_activity != DTRACE_ACTIVITY_STOPPED) {
                        mutex_exit(&dtrace_lock);
                        return (EBUSY);
                  }

                  /*
                   * If this buffer has already been consumed, we're
                   * going to indicate that there's nothing left here
                   * to consume.
                   */
                  if (buf->dtb_flags & DTRACEBUF_CONSUMED) {
                        mutex_exit(&dtrace_lock);

                        desc.dtbd_size = 0;
                        desc.dtbd_drops = 0;
                        desc.dtbd_errors = 0;
                        desc.dtbd_oldest = 0;
                        sz = sizeof (desc);

                        if (copyout(&desc, (void *)arg, sz) != 0)
                              return (EFAULT);

                        return (0);
                  }

                  /*
                   * If this is a ring buffer that has wrapped, we want
                   * to copy the whole thing out.
                   */
                  if (buf->dtb_flags & DTRACEBUF_WRAPPED) {
                        dtrace_buffer_polish(buf);
                        sz = buf->dtb_size;
                  }

                  if (copyout(buf->dtb_tomax, desc.dtbd_data, sz) != 0) {
                        mutex_exit(&dtrace_lock);
                        return (EFAULT);
                  }

                  desc.dtbd_size = sz;
                  desc.dtbd_drops = buf->dtb_drops;
                  desc.dtbd_errors = buf->dtb_errors;
                  desc.dtbd_oldest = buf->dtb_xamot_offset;

                  mutex_exit(&dtrace_lock);

                  if (copyout(&desc, (void *)arg, sizeof (desc)) != 0)
                        return (EFAULT);

                  buf->dtb_flags |= DTRACEBUF_CONSUMED;

                  return (0);
            }

            if (buf->dtb_tomax == NULL) {
                  ASSERT(buf->dtb_xamot == NULL);
                  mutex_exit(&dtrace_lock);
                  return (ENOENT);
            }

            cached = buf->dtb_tomax;
            ASSERT(!(buf->dtb_flags & DTRACEBUF_NOSWITCH));

            dtrace_xcall(desc.dtbd_cpu,
                (dtrace_xcall_t)dtrace_buffer_switch, buf);

            state->dts_errors += buf->dtb_xamot_errors;

            /*
             * If the buffers did not actually switch, then the cross call
             * did not take place -- presumably because the given CPU is
             * not in the ready set.  If this is the case, we'll return
             * ENOENT.
             */
            if (buf->dtb_tomax == cached) {
                  ASSERT(buf->dtb_xamot != cached);
                  mutex_exit(&dtrace_lock);
                  return (ENOENT);
            }

            ASSERT(cached == buf->dtb_xamot);

            /*
             * We have our snapshot; now copy it out.
             */
            if (copyout(buf->dtb_xamot, desc.dtbd_data,
                buf->dtb_xamot_offset) != 0) {
                  mutex_exit(&dtrace_lock);
                  return (EFAULT);
            }

            desc.dtbd_size = buf->dtb_xamot_offset;
            desc.dtbd_drops = buf->dtb_xamot_drops;
            desc.dtbd_errors = buf->dtb_xamot_errors;
            desc.dtbd_oldest = 0;

            mutex_exit(&dtrace_lock);

            /*
             * Finally, copy out the buffer description.
             */
            if (copyout(&desc, (void *)arg, sizeof (desc)) != 0)
                  return (EFAULT);

            return (0);
      }

      case DTRACEIOC_CONF: {
            dtrace_conf_t conf;

            bzero(&conf, sizeof (conf));
            conf.dtc_difversion = DIF_VERSION;
            conf.dtc_difintregs = DIF_DIR_NREGS;
            conf.dtc_diftupregs = DIF_DTR_NREGS;
            conf.dtc_ctfmodel = CTF_MODEL_NATIVE;

            if (copyout(&conf, (void *)arg, sizeof (conf)) != 0)
                  return (EFAULT);

            return (0);
      }

      case DTRACEIOC_STATUS: {
            dtrace_status_t stat;
            dtrace_dstate_t *dstate;
            int i, j;
            uint64_t nerrs;

            /*
             * See the comment in dtrace_state_deadman() for the reason
             * for setting dts_laststatus to INT64_MAX before setting
             * it to the correct value.
             */
            state->dts_laststatus = INT64_MAX;
            dtrace_membar_producer();
            state->dts_laststatus = dtrace_gethrtime();

            bzero(&stat, sizeof (stat));

            mutex_enter(&dtrace_lock);

            if (state->dts_activity == DTRACE_ACTIVITY_INACTIVE) {
                  mutex_exit(&dtrace_lock);
                  return (ENOENT);
            }

            if (state->dts_activity == DTRACE_ACTIVITY_DRAINING)
                  stat.dtst_exiting = 1;

            nerrs = state->dts_errors;
            dstate = &state->dts_vstate.dtvs_dynvars;

            for (i = 0; i < NCPU; i++) {
                  dtrace_dstate_percpu_t *dcpu = &dstate->dtds_percpu[i];

                  stat.dtst_dyndrops += dcpu->dtdsc_drops;
                  stat.dtst_dyndrops_dirty += dcpu->dtdsc_dirty_drops;
                  stat.dtst_dyndrops_rinsing += dcpu->dtdsc_rinsing_drops;

                  if (state->dts_buffer[i].dtb_flags & DTRACEBUF_FULL)
                        stat.dtst_filled++;

                  nerrs += state->dts_buffer[i].dtb_errors;

                  for (j = 0; j < state->dts_nspeculations; j++) {
                        dtrace_speculation_t *spec;
                        dtrace_buffer_t *buf;

                        spec = &state->dts_speculations[j];
                        buf = &spec->dtsp_buffer[i];
                        stat.dtst_specdrops += buf->dtb_xamot_drops;
                  }
            }

            stat.dtst_specdrops_busy = state->dts_speculations_busy;
            stat.dtst_specdrops_unavail = state->dts_speculations_unavail;
            stat.dtst_stkstroverflows = state->dts_stkstroverflows;
            stat.dtst_dblerrors = state->dts_dblerrors;
            stat.dtst_killed =
                (state->dts_activity == DTRACE_ACTIVITY_KILLED);
            stat.dtst_errors = nerrs;

            mutex_exit(&dtrace_lock);

            if (copyout(&stat, (void *)arg, sizeof (stat)) != 0)
                  return (EFAULT);

            return (0);
      }

      case DTRACEIOC_FORMAT: {
            dtrace_fmtdesc_t fmt;
            char *str;
            int len;

            if (copyin((void *)arg, &fmt, sizeof (fmt)) != 0)
                  return (EFAULT);

            mutex_enter(&dtrace_lock);

            if (fmt.dtfd_format == 0 ||
                fmt.dtfd_format > state->dts_nformats) {
                  mutex_exit(&dtrace_lock);
                  return (EINVAL);
            }

            /*
             * Format strings are allocated contiguously and they are
             * never freed; if a format index is less than the number
             * of formats, we can assert that the format map is non-NULL
             * and that the format for the specified index is non-NULL.
             */
            ASSERT(state->dts_formats != NULL);
            str = state->dts_formats[fmt.dtfd_format - 1];
            ASSERT(str != NULL);

            len = strlen(str) + 1;

            if (len > fmt.dtfd_length) {
                  fmt.dtfd_length = len;

                  if (copyout(&fmt, (void *)arg, sizeof (fmt)) != 0) {
                        mutex_exit(&dtrace_lock);
                        return (EINVAL);
                  }
            } else {
                  if (copyout(str, fmt.dtfd_string, len) != 0) {
                        mutex_exit(&dtrace_lock);
                        return (EINVAL);
                  }
            }

            mutex_exit(&dtrace_lock);
            return (0);
      }

      default:
            break;
      }

      return (ENOTTY);
}

/*ARGSUSED*/
static int
dtrace_detach(dev_info_t *dip, ddi_detach_cmd_t cmd)
{
      dtrace_state_t *state;

      switch (cmd) {
      case DDI_DETACH:
            break;

      case DDI_SUSPEND:
            return (DDI_SUCCESS);

      default:
            return (DDI_FAILURE);
      }

      mutex_enter(&cpu_lock);
      mutex_enter(&dtrace_provider_lock);
      mutex_enter(&dtrace_lock);

      ASSERT(dtrace_opens == 0);

      if (dtrace_helpers > 0) {
            mutex_exit(&dtrace_provider_lock);
            mutex_exit(&dtrace_lock);
            mutex_exit(&cpu_lock);
            return (DDI_FAILURE);
      }

      if (dtrace_unregister((dtrace_provider_id_t)dtrace_provider) != 0) {
            mutex_exit(&dtrace_provider_lock);
            mutex_exit(&dtrace_lock);
            mutex_exit(&cpu_lock);
            return (DDI_FAILURE);
      }

      dtrace_provider = NULL;

      if ((state = dtrace_anon_grab()) != NULL) {
            /*
             * If there were ECBs on this state, the provider should
             * have not been allowed to detach; assert that there is
             * none.
             */
            ASSERT(state->dts_necbs == 0);
            dtrace_state_destroy(state);

            /*
             * If we're being detached with anonymous state, we need to
             * indicate to the kernel debugger that DTrace is now inactive.
             */
            (void) kdi_dtrace_set(KDI_DTSET_DTRACE_DEACTIVATE);
      }

      bzero(&dtrace_anon, sizeof (dtrace_anon_t));
      unregister_cpu_setup_func((cpu_setup_func_t *)dtrace_cpu_setup, NULL);
      dtrace_cpu_init = NULL;
      dtrace_helpers_cleanup = NULL;
      dtrace_helpers_fork = NULL;
      dtrace_cpustart_init = NULL;
      dtrace_cpustart_fini = NULL;
      dtrace_debugger_init = NULL;
      dtrace_debugger_fini = NULL;
      dtrace_modload = NULL;
      dtrace_modunload = NULL;

      mutex_exit(&cpu_lock);

      if (dtrace_helptrace_enabled) {
            kmem_free(dtrace_helptrace_buffer, dtrace_helptrace_bufsize);
            dtrace_helptrace_buffer = NULL;
      }

      kmem_free(dtrace_probes, dtrace_nprobes * sizeof (dtrace_probe_t *));
      dtrace_probes = NULL;
      dtrace_nprobes = 0;

      dtrace_hash_destroy(dtrace_bymod);
      dtrace_hash_destroy(dtrace_byfunc);
      dtrace_hash_destroy(dtrace_byname);
      dtrace_bymod = NULL;
      dtrace_byfunc = NULL;
      dtrace_byname = NULL;

      kmem_cache_destroy(dtrace_state_cache);
      vmem_destroy(dtrace_minor);
      vmem_destroy(dtrace_arena);

      if (dtrace_toxrange != NULL) {
            kmem_free(dtrace_toxrange,
                dtrace_toxranges_max * sizeof (dtrace_toxrange_t));
            dtrace_toxrange = NULL;
            dtrace_toxranges = 0;
            dtrace_toxranges_max = 0;
      }

      ddi_remove_minor_node(dtrace_devi, NULL);
      dtrace_devi = NULL;

      ddi_soft_state_fini(&dtrace_softstate);

      ASSERT(dtrace_vtime_references == 0);
      ASSERT(dtrace_opens == 0);
      ASSERT(dtrace_retained == NULL);

      mutex_exit(&dtrace_lock);
      mutex_exit(&dtrace_provider_lock);

      /*
       * We don't destroy the task queue until after we have dropped our
       * locks (taskq_destroy() may block on running tasks).  To prevent
       * attempting to do work after we have effectively detached but before
       * the task queue has been destroyed, all tasks dispatched via the
       * task queue must check that DTrace is still attached before
       * performing any operation.
       */
      taskq_destroy(dtrace_taskq);
      dtrace_taskq = NULL;

      return (DDI_SUCCESS);
}
#endif

#if defined(sun)
/*ARGSUSED*/
static int
dtrace_info(dev_info_t *dip, ddi_info_cmd_t infocmd, void *arg, void **result)
{
      int error;

      switch (infocmd) {
      case DDI_INFO_DEVT2DEVINFO:
            *result = (void *)dtrace_devi;
            error = DDI_SUCCESS;
            break;
      case DDI_INFO_DEVT2INSTANCE:
            *result = (void *)0;
            error = DDI_SUCCESS;
            break;
      default:
            error = DDI_FAILURE;
      }
      return (error);
}
#endif

#if defined(sun)
static struct cb_ops dtrace_cb_ops = {
      dtrace_open,            /* open */
      dtrace_close,           /* close */
      nulldev,          /* strategy */
      nulldev,          /* print */
      nodev,                  /* dump */
      nodev,                  /* read */
      nodev,                  /* write */
      dtrace_ioctl,           /* ioctl */
      nodev,                  /* devmap */
      nodev,                  /* mmap */
      nodev,                  /* segmap */
      nochpoll,         /* poll */
      ddi_prop_op,            /* cb_prop_op */
      0,                /* streamtab  */
      D_NEW | D_MP            /* Driver compatibility flag */
};

static struct dev_ops dtrace_ops = {
      DEVO_REV,         /* devo_rev */
      0,                /* refcnt */
      dtrace_info,            /* get_dev_info */
      nulldev,          /* identify */
      nulldev,          /* probe */
      dtrace_attach,          /* attach */
      dtrace_detach,          /* detach */
      nodev,                  /* reset */
      &dtrace_cb_ops,         /* driver operations */
      NULL,             /* bus operations */
      nodev             /* dev power */
};

static struct modldrv modldrv = {
      &mod_driverops,         /* module type (this is a pseudo driver) */
      "Dynamic Tracing",      /* name of module */
      &dtrace_ops,            /* driver ops */
};

static struct modlinkage modlinkage = {
      MODREV_1,
      (void *)&modldrv,
      NULL
};

int
_init(void)
{
      return (mod_install(&modlinkage));
}

int
_info(struct modinfo *modinfop)
{
      return (mod_info(&modlinkage, modinfop));
}

int
_fini(void)
{
      return (mod_remove(&modlinkage));
}
#else

static d_ioctl_t  dtrace_ioctl;
static void       dtrace_load(void *);
static int        dtrace_unload(void);
#if __FreeBSD_version < 800039
static void       dtrace_clone(void *, struct ucred *, char *, int , struct cdev **);
static struct clonedevs *dtrace_clones;         /* Ptr to the array of cloned devices. */
static eventhandler_tag eh_tag;                 /* Event handler tag. */
#else
static struct cdev      *dtrace_dev;
#endif

void dtrace_invop_init(void);
void dtrace_invop_uninit(void);

static struct cdevsw dtrace_cdevsw = {
      .d_version  = D_VERSION,
      .d_flags    = D_TRACKCLOSE | D_NEEDMINOR,
      .d_close    = dtrace_close,
      .d_ioctl    = dtrace_ioctl,
      .d_open           = dtrace_open,
      .d_name           = "dtrace",
};

#include <dtrace_anon.c>
#if __FreeBSD_version < 800039
#include <dtrace_clone.c>
#endif
#include <dtrace_ioctl.c>
#include <dtrace_load.c>
#include <dtrace_modevent.c>
#include <dtrace_sysctl.c>
#include <dtrace_unload.c>
#include <dtrace_vtime.c>
#include <dtrace_hacks.c>
#include <dtrace_isa.c>

SYSINIT(dtrace_load, SI_SUB_DTRACE, SI_ORDER_FIRST, dtrace_load, NULL);
SYSUNINIT(dtrace_unload, SI_SUB_DTRACE, SI_ORDER_FIRST, dtrace_unload, NULL);
SYSINIT(dtrace_anon_init, SI_SUB_DTRACE_ANON, SI_ORDER_FIRST, dtrace_anon_init, NULL);

DEV_MODULE(dtrace, dtrace_modevent, NULL);
MODULE_VERSION(dtrace, 1);
MODULE_DEPEND(dtrace, cyclic, 1, 1, 1);
MODULE_DEPEND(dtrace, opensolaris, 1, 1, 1);
#endif

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