libdtrace/common/dt_provider.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
 */

/*
 * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

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

#include <sys/types.h>
#include <sys/sysmacros.h>

#include <assert.h>
#include <limits.h>
#include <strings.h>
#include <stdlib.h>
#include <alloca.h>
#include <unistd.h>
#include <errno.h>

#include <dt_provider.h>
#include <dt_module.h>
#include <dt_string.h>
#include <dt_list.h>

static dt_provider_t *
dt_provider_insert(dtrace_hdl_t *dtp, dt_provider_t *pvp, uint_t h)
{
    dt_list_append(&dtp->dt_provlist, pvp);

    pvp->pv_next = dtp->dt_provs[h];
    dtp->dt_provs[h] = pvp;
    dtp->dt_nprovs++;

    return (pvp);
}

dt_provider_t *
dt_provider_lookup(dtrace_hdl_t *dtp, const char *name)
{
    uint_t h = dt_strtab_hash(name, NULL) % dtp->dt_provbuckets;
    dtrace_providerdesc_t desc;
    dt_provider_t *pvp;

    for (pvp = dtp->dt_provs[h]; pvp != NULL; pvp = pvp->pv_next) {
        if (strcmp(pvp->pv_desc.dtvd_name, name) == 0)
            return (pvp);
    }

    if (strisglob(name) || name[0] == '\0') {
        (void) dt_set_errno(dtp, EDT_NOPROV);
        return (NULL);
    }

    bzero(&desc, sizeof (desc));
    (void) strlcpy(desc.dtvd_name, name, DTRACE_PROVNAMELEN);

    if (dt_ioctl(dtp, DTRACEIOC_PROVIDER, &desc) == -1) {
        (void) dt_set_errno(dtp, errno == ESRCH ? EDT_NOPROV : errno);
        return (NULL);
    }

    if ((pvp = dt_provider_create(dtp, name)) == NULL)
        return (NULL); /* dt_errno is set for us */

    bcopy(&desc, &pvp->pv_desc, sizeof (desc));
    pvp->pv_flags |= DT_PROVIDER_IMPL;
    return (pvp);
}

dt_provider_t *
dt_provider_create(dtrace_hdl_t *dtp, const char *name)
{
    dt_provider_t *pvp;

    if ((pvp = dt_zalloc(dtp, sizeof (dt_provider_t))) == NULL)
        return (NULL);

    (void) strlcpy(pvp->pv_desc.dtvd_name, name, DTRACE_PROVNAMELEN);
    pvp->pv_probes = dt_idhash_create(pvp->pv_desc.dtvd_name, NULL, 0, 0);
    pvp->pv_gen = dtp->dt_gen;
    pvp->pv_hdl = dtp;

    if (pvp->pv_probes == NULL) {
        dt_free(dtp, pvp);
        (void) dt_set_errno(dtp, EDT_NOMEM);
        return (NULL);
    }

    pvp->pv_desc.dtvd_attr.dtpa_provider = _dtrace_prvattr;
    pvp->pv_desc.dtvd_attr.dtpa_mod = _dtrace_prvattr;
    pvp->pv_desc.dtvd_attr.dtpa_func = _dtrace_prvattr;
    pvp->pv_desc.dtvd_attr.dtpa_name = _dtrace_prvattr;
    pvp->pv_desc.dtvd_attr.dtpa_args = _dtrace_prvattr;

    return (dt_provider_insert(dtp, pvp,
        dt_strtab_hash(name, NULL) % dtp->dt_provbuckets));
}

void
dt_provider_destroy(dtrace_hdl_t *dtp, dt_provider_t *pvp)
{
    dt_provider_t **pp;
    uint_t h;

    assert(pvp->pv_hdl == dtp);

    h = dt_strtab_hash(pvp->pv_desc.dtvd_name, NULL) % dtp->dt_provbuckets;
    pp = &dtp->dt_provs[h];

    while (*pp != NULL && *pp != pvp)
        pp = &(*pp)->pv_next;

    assert(*pp != NULL && *pp == pvp);
    *pp = pvp->pv_next;

    dt_list_delete(&dtp->dt_provlist, pvp);
    dtp->dt_nprovs--;

    if (pvp->pv_probes != NULL)
        dt_idhash_destroy(pvp->pv_probes);

    dt_node_link_free(&pvp->pv_nodes);
    dt_free(dtp, pvp->pv_xrefs);
    dt_free(dtp, pvp);
}

int
dt_provider_xref(dtrace_hdl_t *dtp, dt_provider_t *pvp, id_t id)
{
    size_t oldsize = BT_SIZEOFMAP(pvp->pv_xrmax);
    size_t newsize = BT_SIZEOFMAP(dtp->dt_xlatorid);

    assert(id >= 0 && id < dtp->dt_xlatorid);

    if (newsize > oldsize) {
        ulong_t *xrefs = dt_zalloc(dtp, newsize);

        if (xrefs == NULL)
            return (-1);

        bcopy(pvp->pv_xrefs, xrefs, oldsize);
        dt_free(dtp, pvp->pv_xrefs);

        pvp->pv_xrefs = xrefs;
        pvp->pv_xrmax = dtp->dt_xlatorid;
    }

    BT_SET(pvp->pv_xrefs, id);
    return (0);
}

static uint8_t
dt_probe_argmap(dt_node_t *xnp, dt_node_t *nnp)
{
    uint8_t i;

    for (i = 0; nnp != NULL; i++) {
        if (nnp->dn_string != NULL &&
            strcmp(nnp->dn_string, xnp->dn_string) == 0)
            break;
        else
            nnp = nnp->dn_list;
    }

    return (i);
}

static dt_node_t *
dt_probe_alloc_args(dt_provider_t *pvp, int argc)
{
    dt_node_t *args = NULL, *pnp = NULL, *dnp;
    int i;

    for (i = 0; i < argc; i++, pnp = dnp) {
        if ((dnp = dt_node_xalloc(pvp->pv_hdl, DT_NODE_TYPE)) == NULL)
            return (NULL);

        dnp->dn_link = pvp->pv_nodes;
        pvp->pv_nodes = dnp;

        if (args == NULL)
            args = dnp;
        else
            pnp->dn_list = dnp;
    }

    return (args);
}

static size_t
dt_probe_keylen(const dtrace_probedesc_t *pdp)
{
    return (strlen(pdp->dtpd_mod) + 1 +
        strlen(pdp->dtpd_func) + 1 + strlen(pdp->dtpd_name) + 1);
}

static char *
dt_probe_key(const dtrace_probedesc_t *pdp, char *s)
{
    (void) snprintf(s, INT_MAX, "%s:%s:%s",
        pdp->dtpd_mod, pdp->dtpd_func, pdp->dtpd_name);
    return (s);
}

/*
 * If a probe was discovered from the kernel, ask dtrace(7D) for a description
 * of each of its arguments, including native and translated types.
 */
static dt_probe_t *
dt_probe_discover(dt_provider_t *pvp, const dtrace_probedesc_t *pdp)
{
    dtrace_hdl_t *dtp = pvp->pv_hdl;
    char *name = dt_probe_key(pdp, alloca(dt_probe_keylen(pdp)));

    dt_node_t *xargs, *nargs;
    dt_ident_t *idp;
    dt_probe_t *prp;

    dtrace_typeinfo_t dtt;
    int i, nc, xc;

    int adc = _dtrace_argmax;
    dtrace_argdesc_t *adv = alloca(sizeof (dtrace_argdesc_t) * adc);
    dtrace_argdesc_t *adp = adv;

    assert(strcmp(pvp->pv_desc.dtvd_name, pdp->dtpd_provider) == 0);
    assert(pdp->dtpd_id != DTRACE_IDNONE);

    dt_dprintf("discovering probe %s:%s id=%d\n",
        pvp->pv_desc.dtvd_name, name, pdp->dtpd_id);

    for (nc = -1, i = 0; i < adc; i++, adp++) {
        bzero(adp, sizeof (dtrace_argdesc_t));
        adp->dtargd_ndx = i;
        adp->dtargd_id = pdp->dtpd_id;

        if (dt_ioctl(dtp, DTRACEIOC_PROBEARG, adp) != 0) {
            (void) dt_set_errno(dtp, errno);
            return (NULL);
        }

        if (adp->dtargd_ndx == DTRACE_ARGNONE)
            break; /* all argument descs have been retrieved */

        nc = MAX(nc, adp->dtargd_mapping);
    }

    xc = i;
    nc++;

    /*
     * Now that we have discovered the number of native and translated
     * arguments from the argument descriptions, allocate a new probe ident
     * and corresponding dt_probe_t and hash it into the provider.
     */
    xargs = dt_probe_alloc_args(pvp, xc);
    nargs = dt_probe_alloc_args(pvp, nc);

    if ((xc != 0 && xargs == NULL) || (nc != 0 && nargs == NULL))
        return (NULL); /* dt_errno is set for us */

    idp = dt_ident_create(name, DT_IDENT_PROBE,
        DT_IDFLG_ORPHAN, pdp->dtpd_id, _dtrace_defattr, 0,
        &dt_idops_probe, NULL, dtp->dt_gen);

    if (idp == NULL) {
        (void) dt_set_errno(dtp, EDT_NOMEM);
        return (NULL);
    }

    if ((prp = dt_probe_create(dtp, idp, 2,
        nargs, nc, xargs, xc)) == NULL) {
        dt_ident_destroy(idp);
        return (NULL);
    }

    dt_probe_declare(pvp, prp);

    /*
     * Once our new dt_probe_t is fully constructed, iterate over the
     * cached argument descriptions and assign types to prp->pr_nargv[]
     * and prp->pr_xargv[] and assign mappings to prp->pr_mapping[].
     */
    for (adp = adv, i = 0; i < xc; i++, adp++) {
        if (dtrace_type_strcompile(dtp,
            adp->dtargd_native, &dtt) != 0) {
            dt_dprintf("failed to resolve input type %s "
                "for %s:%s arg #%d: %s\n", adp->dtargd_native,
                pvp->pv_desc.dtvd_name, name, i + 1,
                dtrace_errmsg(dtp, dtrace_errno(dtp)));

            dtt.dtt_object = NULL;
            dtt.dtt_ctfp = NULL;
            dtt.dtt_type = CTF_ERR;
        } else {
            dt_node_type_assign(prp->pr_nargv[adp->dtargd_mapping],
                dtt.dtt_ctfp, dtt.dtt_type);
        }

        if (dtt.dtt_type != CTF_ERR && (adp->dtargd_xlate[0] == '\0' ||
            strcmp(adp->dtargd_native, adp->dtargd_xlate) == 0)) {
            dt_node_type_propagate(prp->pr_nargv[
                adp->dtargd_mapping], prp->pr_xargv[i]);
        } else if (dtrace_type_strcompile(dtp,
            adp->dtargd_xlate, &dtt) != 0) {
            dt_dprintf("failed to resolve output type %s "
                "for %s:%s arg #%d: %s\n", adp->dtargd_xlate,
                pvp->pv_desc.dtvd_name, name, i + 1,
                dtrace_errmsg(dtp, dtrace_errno(dtp)));

            dtt.dtt_object = NULL;
            dtt.dtt_ctfp = NULL;
            dtt.dtt_type = CTF_ERR;
        } else {
            dt_node_type_assign(prp->pr_xargv[i],
                dtt.dtt_ctfp, dtt.dtt_type);
        }

        prp->pr_mapping[i] = adp->dtargd_mapping;
        prp->pr_argv[i] = dtt;
    }

    return (prp);
}

/*
 * Lookup a probe declaration based on a known provider and full or partially
 * specified module, function, and name.  If the probe is not known to us yet,
 * ask dtrace(7D) to match the description and then cache any useful results.
 */
dt_probe_t *
dt_probe_lookup(dt_provider_t *pvp, const char *s)
{
    dtrace_hdl_t *dtp = pvp->pv_hdl;
    dtrace_probedesc_t pd;
    dt_ident_t *idp;
    size_t keylen;
    char *key;

    if (dtrace_str2desc(dtp, DTRACE_PROBESPEC_NAME, s, &pd) != 0)
        return (NULL); /* dt_errno is set for us */

    keylen = dt_probe_keylen(&pd);
    key = dt_probe_key(&pd, alloca(keylen));

    /*
     * If the probe is already declared, then return the dt_probe_t from
     * the existing identifier.  This could come from a static declaration
     * or it could have been cached from an earlier call to this function.
     */
    if ((idp = dt_idhash_lookup(pvp->pv_probes, key)) != NULL)
        return (idp->di_data);

    /*
     * If the probe isn't known, use the probe description computed above
     * to ask dtrace(7D) to find the first matching probe.
     */
    if (dt_ioctl(dtp, DTRACEIOC_PROBEMATCH, &pd) == 0)
        return (dt_probe_discover(pvp, &pd));

    if (errno == ESRCH || errno == EBADF)
        (void) dt_set_errno(dtp, EDT_NOPROBE);
    else
        (void) dt_set_errno(dtp, errno);

    return (NULL);
}

dt_probe_t *
dt_probe_create(dtrace_hdl_t *dtp, dt_ident_t *idp, int protoc,
    dt_node_t *nargs, uint_t nargc, dt_node_t *xargs, uint_t xargc)
{
    dt_module_t *dmp;
    dt_probe_t *prp;
    const char *p;
    uint_t i;

    assert(idp->di_kind == DT_IDENT_PROBE);
    assert(idp->di_data == NULL);

    /*
     * If only a single prototype is given, set xargc/s to nargc/s to
     * simplify subsequent use.  Note that we can have one or both of nargs
     * and xargs be specified but set to NULL, indicating a void prototype.
     */
    if (protoc < 2) {
        assert(xargs == NULL);
        assert(xargc == 0);
        xargs = nargs;
        xargc = nargc;
    }

    if ((prp = dt_alloc(dtp, sizeof (dt_probe_t))) == NULL)
        return (NULL);

    prp->pr_pvp = NULL;
    prp->pr_ident = idp;

    p = strrchr(idp->di_name, ':');
    assert(p != NULL);
    prp->pr_name = p + 1;

    prp->pr_nargs = nargs;
    prp->pr_nargv = dt_alloc(dtp, sizeof (dt_node_t *) * nargc);
    prp->pr_nargc = nargc;
    prp->pr_xargs = xargs;
    prp->pr_xargv = dt_alloc(dtp, sizeof (dt_node_t *) * xargc);
    prp->pr_xargc = xargc;
    prp->pr_mapping = dt_alloc(dtp, sizeof (uint8_t) * xargc);
    prp->pr_inst = NULL;
    prp->pr_argv = dt_alloc(dtp, sizeof (dtrace_typeinfo_t) * xargc);
    prp->pr_argc = xargc;

    if ((prp->pr_nargc != 0 && prp->pr_nargv == NULL) ||
        (prp->pr_xargc != 0 && prp->pr_xargv == NULL) ||
        (prp->pr_xargc != 0 && prp->pr_mapping == NULL) ||
        (prp->pr_argc != 0 && prp->pr_argv == NULL)) {
        dt_probe_destroy(prp);
        return (NULL);
    }

    for (i = 0; i < xargc; i++, xargs = xargs->dn_list) {
        if (xargs->dn_string != NULL)
            prp->pr_mapping[i] = dt_probe_argmap(xargs, nargs);
        else
            prp->pr_mapping[i] = i;

        prp->pr_xargv[i] = xargs;

        if ((dmp = dt_module_lookup_by_ctf(dtp,
            xargs->dn_ctfp)) != NULL)
            prp->pr_argv[i].dtt_object = dmp->dm_name;
        else
            prp->pr_argv[i].dtt_object = NULL;

        prp->pr_argv[i].dtt_ctfp = xargs->dn_ctfp;
        prp->pr_argv[i].dtt_type = xargs->dn_type;
    }

    for (i = 0; i < nargc; i++, nargs = nargs->dn_list)
        prp->pr_nargv[i] = nargs;

    idp->di_data = prp;
    return (prp);
}

void
dt_probe_declare(dt_provider_t *pvp, dt_probe_t *prp)
{
    assert(prp->pr_ident->di_kind == DT_IDENT_PROBE);
    assert(prp->pr_ident->di_data == prp);
    assert(prp->pr_pvp == NULL);

    if (prp->pr_xargs != prp->pr_nargs)
        pvp->pv_flags &= ~DT_PROVIDER_INTF;

    prp->pr_pvp = pvp;
    dt_idhash_xinsert(pvp->pv_probes, prp->pr_ident);
}

void
dt_probe_destroy(dt_probe_t *prp)
{
    dt_probe_instance_t *pip, *pip_next;
    dtrace_hdl_t *dtp;

    if (prp->pr_pvp != NULL)
        dtp = prp->pr_pvp->pv_hdl;
    else
        dtp = yypcb->pcb_hdl;

    dt_node_list_free(&prp->pr_nargs);
    dt_node_list_free(&prp->pr_xargs);

    dt_free(dtp, prp->pr_nargv);
    dt_free(dtp, prp->pr_xargv);

    for (pip = prp->pr_inst; pip != NULL; pip = pip_next) {
        pip_next = pip->pi_next;
        dt_free(dtp, pip->pi_offs);
        dt_free(dtp, pip->pi_enoffs);
        dt_free(dtp, pip);
    }

    dt_free(dtp, prp->pr_mapping);
    dt_free(dtp, prp->pr_argv);
    dt_free(dtp, prp);
}

int
dt_probe_define(dt_provider_t *pvp, dt_probe_t *prp,
    const char *fname, const char *rname, uint32_t offset, int isenabled)
{
    dtrace_hdl_t *dtp = pvp->pv_hdl;
    dt_probe_instance_t *pip;
    uint32_t **offs;
    uint_t *noffs, *maxoffs;

    assert(fname != NULL);

    for (pip = prp->pr_inst; pip != NULL; pip = pip->pi_next) {
        if (strcmp(pip->pi_fname, fname) == 0 &&
            ((rname == NULL && pip->pi_rname[0] == '\0') ||
            (rname != NULL && strcmp(pip->pi_rname, rname)) == 0))
            break;
    }

    if (pip == NULL) {
        if ((pip = dt_zalloc(dtp, sizeof (*pip))) == NULL)
            return (-1);

        if ((pip->pi_offs = dt_zalloc(dtp,
            sizeof (uint32_t))) == NULL) {
            dt_free(dtp, pip);
            return (-1);
        }

        if ((pip->pi_enoffs = dt_zalloc(dtp,
            sizeof (uint32_t))) == NULL) {
            dt_free(dtp, pip->pi_offs);
            dt_free(dtp, pip);
            return (-1);
        }

        (void) strlcpy(pip->pi_fname, fname, sizeof (pip->pi_fname));
        if (rname != NULL) {
            if (strlen(rname) + 1 > sizeof (pip->pi_rname)) {
                dt_free(dtp, pip->pi_offs);
                dt_free(dtp, pip);
                return (dt_set_errno(dtp, EDT_COMPILER));
            }
            (void) strcpy(pip->pi_rname, rname);
        }

        pip->pi_noffs = 0;
        pip->pi_maxoffs = 1;
        pip->pi_nenoffs = 0;
        pip->pi_maxenoffs = 1;

        pip->pi_next = prp->pr_inst;

        prp->pr_inst = pip;
    }

    if (isenabled) {
        offs = &pip->pi_enoffs;
        noffs = &pip->pi_nenoffs;
        maxoffs = &pip->pi_maxenoffs;
    } else {
        offs = &pip->pi_offs;
        noffs = &pip->pi_noffs;
        maxoffs = &pip->pi_maxoffs;
    }

    if (*noffs == *maxoffs) {
        uint_t new_max = *maxoffs * 2;
        uint32_t *new_offs = dt_alloc(dtp, sizeof (uint32_t) * new_max);

        if (new_offs == NULL)
            return (-1);

        bcopy(*offs, new_offs, sizeof (uint32_t) * *maxoffs);

        dt_free(dtp, *offs);
        *maxoffs = new_max;
        *offs = new_offs;
    }

    dt_dprintf("defined probe %s %s:%s %s() +0x%x (%s)\n",
        isenabled ? "(is-enabled)" : "",
        pvp->pv_desc.dtvd_name, prp->pr_ident->di_name, fname, offset,
        rname != NULL ? rname : fname);

    assert(*noffs < *maxoffs);
    (*offs)[(*noffs)++] = offset;

    return (0);
}

/*
 * Lookup the dynamic translator type tag for the specified probe argument and
 * assign the type to the specified node.  If the type is not yet defined, add
 * it to the "D" module's type container as a typedef for an unknown type.
 */
dt_node_t *
dt_probe_tag(dt_probe_t *prp, uint_t argn, dt_node_t *dnp)
{
    dtrace_hdl_t *dtp = prp->pr_pvp->pv_hdl;
    dtrace_typeinfo_t dtt;
    size_t len;
    char *tag;

    len = snprintf(NULL, 0, "__dtrace_%s___%s_arg%u",
        prp->pr_pvp->pv_desc.dtvd_name, prp->pr_name, argn);

    tag = alloca(len + 1);

    (void) snprintf(tag, len + 1, "__dtrace_%s___%s_arg%u",
        prp->pr_pvp->pv_desc.dtvd_name, prp->pr_name, argn);

    if (dtrace_lookup_by_type(dtp, DTRACE_OBJ_DDEFS, tag, &dtt) != 0) {
        dtt.dtt_object = DTRACE_OBJ_DDEFS;
        dtt.dtt_ctfp = DT_DYN_CTFP(dtp);
        dtt.dtt_type = ctf_add_typedef(DT_DYN_CTFP(dtp),
            CTF_ADD_ROOT, tag, DT_DYN_TYPE(dtp));

        if (dtt.dtt_type == CTF_ERR ||
            ctf_update(dtt.dtt_ctfp) == CTF_ERR) {
            xyerror(D_UNKNOWN, "cannot define type %s: %s\n",
                tag, ctf_errmsg(ctf_errno(dtt.dtt_ctfp)));
        }
    }

    bzero(dnp, sizeof (dt_node_t));
    dnp->dn_kind = DT_NODE_TYPE;

    dt_node_type_assign(dnp, dtt.dtt_ctfp, dtt.dtt_type);
    dt_node_attr_assign(dnp, _dtrace_defattr);

    return (dnp);
}

/*ARGSUSED*/
static int
dt_probe_desc(dtrace_hdl_t *dtp, const dtrace_probedesc_t *pdp, void *arg)
{
    if (((dtrace_probedesc_t *)arg)->dtpd_id == DTRACE_IDNONE) {
        bcopy(pdp, arg, sizeof (dtrace_probedesc_t));
        return (0);
    }

    return (1);
}

dt_probe_t *
dt_probe_info(dtrace_hdl_t *dtp,
    const dtrace_probedesc_t *pdp, dtrace_probeinfo_t *pip)
{
    int m_is_glob = pdp->dtpd_mod[0] == '\0' || strisglob(pdp->dtpd_mod);
    int f_is_glob = pdp->dtpd_func[0] == '\0' || strisglob(pdp->dtpd_func);
    int n_is_glob = pdp->dtpd_name[0] == '\0' || strisglob(pdp->dtpd_name);

    dt_probe_t *prp = NULL;
    const dtrace_pattr_t *pap;
    dt_provider_t *pvp;
    dt_ident_t *idp;

    /*
     * Attempt to lookup the probe in our existing cache for this provider.
     * If none is found and an explicit probe ID was specified, discover
     * that specific probe and cache its description and arguments.
     */
    if ((pvp = dt_provider_lookup(dtp, pdp->dtpd_provider)) != NULL) {
        size_t keylen = dt_probe_keylen(pdp);
        char *key = dt_probe_key(pdp, alloca(keylen));

        if ((idp = dt_idhash_lookup(pvp->pv_probes, key)) != NULL)
            prp = idp->di_data;
        else if (pdp->dtpd_id != DTRACE_IDNONE)
            prp = dt_probe_discover(pvp, pdp);
    }

    /*
     * If no probe was found in our cache, convert the caller's partial
     * probe description into a fully-formed matching probe description by
     * iterating over up to at most two probes that match 'pdp'.  We then
     * call dt_probe_discover() on the resulting probe identifier.
     */
    if (prp == NULL) {
        dtrace_probedesc_t pd;
        int m;

        bzero(&pd, sizeof (pd));
        pd.dtpd_id = DTRACE_IDNONE;

        /*
         * Call dtrace_probe_iter() to find matching probes.  Our
         * dt_probe_desc() callback will produce the following results:
         *
         * m < 0 dtrace_probe_iter() found zero matches (or failed).
         * m > 0 dtrace_probe_iter() found more than one match.
         * m = 0 dtrace_probe_iter() found exactly one match.
         */
        if ((m = dtrace_probe_iter(dtp, pdp, dt_probe_desc, &pd)) < 0)
            return (NULL); /* dt_errno is set for us */

        if ((pvp = dt_provider_lookup(dtp, pd.dtpd_provider)) == NULL)
            return (NULL); /* dt_errno is set for us */

        /*
         * If more than one probe was matched, then do not report probe
         * information if either of the following conditions is true:
         *
         * (a) The Arguments Data stability of the matched provider is
         *  less than Evolving.
         *
         * (b) Any description component that is at least Evolving is
         *  empty or is specified using a globbing expression.
         *
         * These conditions imply that providers that provide Evolving
         * or better Arguments Data stability must guarantee that all
         * probes with identical field names in a field of Evolving or
         * better Name stability have identical argument signatures.
         */
        if (m > 0) {
            if (pvp->pv_desc.dtvd_attr.dtpa_args.dtat_data <
                DTRACE_STABILITY_EVOLVING) {
                (void) dt_set_errno(dtp, EDT_UNSTABLE);
                return (NULL);
            }


            if (pvp->pv_desc.dtvd_attr.dtpa_mod.dtat_name >=
                DTRACE_STABILITY_EVOLVING && m_is_glob) {
                (void) dt_set_errno(dtp, EDT_UNSTABLE);
                return (NULL);
            }

            if (pvp->pv_desc.dtvd_attr.dtpa_func.dtat_name >=
                DTRACE_STABILITY_EVOLVING && f_is_glob) {
                (void) dt_set_errno(dtp, EDT_UNSTABLE);
                return (NULL);
            }

            if (pvp->pv_desc.dtvd_attr.dtpa_name.dtat_name >=
                DTRACE_STABILITY_EVOLVING && n_is_glob) {
                (void) dt_set_errno(dtp, EDT_UNSTABLE);
                return (NULL);
            }
        }

        /*
         * If we matched a probe exported by dtrace(7D), then discover
         * the real attributes.  Otherwise grab the static declaration.
         */
        if (pd.dtpd_id != DTRACE_IDNONE)
            prp = dt_probe_discover(pvp, &pd);
        else
            prp = dt_probe_lookup(pvp, pd.dtpd_name);

        if (prp == NULL)
            return (NULL); /* dt_errno is set for us */
    }

    assert(pvp != NULL && prp != NULL);

    /*
     * Compute the probe description attributes by taking the minimum of
     * the attributes of the specified fields.  If no provider is specified
     * or a glob pattern is used for the provider, use Unstable attributes.
     */
    if (pdp->dtpd_provider[0] == '\0' || strisglob(pdp->dtpd_provider))
        pap = &_dtrace_prvdesc;
    else
        pap = &pvp->pv_desc.dtvd_attr;

    pip->dtp_attr = pap->dtpa_provider;

    if (!m_is_glob)
        pip->dtp_attr = dt_attr_min(pip->dtp_attr, pap->dtpa_mod);
    if (!f_is_glob)
        pip->dtp_attr = dt_attr_min(pip->dtp_attr, pap->dtpa_func);
    if (!n_is_glob)
        pip->dtp_attr = dt_attr_min(pip->dtp_attr, pap->dtpa_name);

    pip->dtp_arga = pap->dtpa_args;
    pip->dtp_argv = prp->pr_argv;
    pip->dtp_argc = prp->pr_argc;

    return (prp);
}

int
dtrace_probe_info(dtrace_hdl_t *dtp,
    const dtrace_probedesc_t *pdp, dtrace_probeinfo_t *pip)
{
    return (dt_probe_info(dtp, pdp, pip) != NULL ? 0 : -1);
}

/*ARGSUSED*/
static int
dt_probe_iter(dt_idhash_t *ihp, dt_ident_t *idp, dt_probe_iter_t *pit)
{
    const dt_probe_t *prp = idp->di_data;

    if (!dt_gmatch(prp->pr_name, pit->pit_pat))
        return (0); /* continue on and examine next probe in hash */

    (void) strlcpy(pit->pit_desc.dtpd_name, prp->pr_name, DTRACE_NAMELEN);
    pit->pit_desc.dtpd_id = idp->di_id;
    pit->pit_matches++;

    return (pit->pit_func(pit->pit_hdl, &pit->pit_desc, pit->pit_arg));
}

int
dtrace_probe_iter(dtrace_hdl_t *dtp,
    const dtrace_probedesc_t *pdp, dtrace_probe_f *func, void *arg)
{
    const char *provider = pdp ? pdp->dtpd_provider : NULL;
    dtrace_id_t id = DTRACE_IDNONE;

    dtrace_probedesc_t pd;
    dt_probe_iter_t pit;
    int cmd, rv;

    bzero(&pit, sizeof (pit));
    pit.pit_hdl = dtp;
    pit.pit_func = func;
    pit.pit_arg = arg;
    pit.pit_pat = pdp ? pdp->dtpd_name : NULL;

    for (pit.pit_pvp = dt_list_next(&dtp->dt_provlist);
        pit.pit_pvp != NULL; pit.pit_pvp = dt_list_next(pit.pit_pvp)) {

        if (pit.pit_pvp->pv_flags & DT_PROVIDER_IMPL)
            continue; /* we'll get these later using dt_ioctl() */

        if (!dt_gmatch(pit.pit_pvp->pv_desc.dtvd_name, provider))
            continue;

        (void) strlcpy(pit.pit_desc.dtpd_provider,
            pit.pit_pvp->pv_desc.dtvd_name, DTRACE_PROVNAMELEN);

        if ((rv = dt_idhash_iter(pit.pit_pvp->pv_probes,
            (dt_idhash_f *)dt_probe_iter, &pit)) != 0)
            return (rv);
    }

    if (pdp != NULL)
        cmd = DTRACEIOC_PROBEMATCH;
    else
        cmd = DTRACEIOC_PROBES;

    for (;;) {
        if (pdp != NULL)
            bcopy(pdp, &pd, sizeof (pd));

        pd.dtpd_id = id;

        if (dt_ioctl(dtp, cmd, &pd) != 0)
            break;
        else if ((rv = func(dtp, &pd, arg)) != 0)
            return (rv);

        pit.pit_matches++;
        id = pd.dtpd_id + 1;
    }

    switch (errno) {
    case ESRCH:
    case EBADF:
        return (pit.pit_matches ? 0 : dt_set_errno(dtp, EDT_NOPROBE));
    case EINVAL:
        return (dt_set_errno(dtp, EDT_BADPGLOB));
    default:
        return (dt_set_errno(dtp, errno));
    }
}