lib/libtnfctl/probes.c

	probes.c revision 7c478bd95313f5f23a4c958a745db2134aa03244
/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (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 (c) 1994, by Sun Microsytems, Inc.
 */

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

/*
 * Load object and probe discovery in target process.  This file is
 * not exercised for kernel probes.
 */

#ifndef DEBUG
#define NDEBUG  1
#endif

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <stddef.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <assert.h>

#include "tnfctl_int.h"
#include "kernel_int.h"
#include "dbg.h"

/*
 * Defines - Project private interfaces
 */

#define PROBE_SYMBOL    "__tnf_probe_version_1"

/*
 * Typedefs
 */

typedef struct link_args {
    char        *la_probename;
    int     ret_val;
} link_args_t;

typedef struct link_args2 {
    tnfctl_handle_t *la_hndl;
    char        *la_probename;
    objlist_t   *la_obj;
    ulong_t     la_index;
    ulong_t     la_base;
} link_args2_t;

NOTE(SCHEME_PROTECTS_DATA("always automatic", link_args link_args2))

static int per_loadobj(void *, const tnfctl_ind_obj_info_t *, void *);
static objlist_t *loadobj_find(tnfctl_handle_t *,
            const tnfctl_ind_obj_info_t *);
static tnfctl_errcode_t get_num_probes(tnfctl_handle_t *, objlist_t *, int *);
static tnfctl_errcode_t read_probes_in_obj(tnfctl_handle_t *, objlist_t *,
        ulong_t, ulong_t);
static void free_obj_fields(objlist_t *);
static tnfctl_errcode_t count_probes(char *, uintptr_t, void *,
                    tnfctl_elf_search_t *);
static tnfctl_errcode_t read_a_probe(char *, uintptr_t, void *,
                    tnfctl_elf_search_t *);
static tnfctl_errcode_t link_targ_obj_probes(tnfctl_handle_t *, objlist_t *);
static tnfctl_errcode_t unlink_targ_obj_probes(tnfctl_handle_t *, objlist_t *);

/*
 * sync up our library list with that of the run time linker's
 * Returns an event indicating if a dlopen or dlclose happened.
 */
tnfctl_errcode_t
_tnfctl_lmap_update(tnfctl_handle_t *hndl, boolean_t *lmap_ok,
                enum event_op_t *dl_evt)
{
    int     miscstat;
    objlist_t   *cur_obj;

    *lmap_ok = B_TRUE;

    /* reset old and new of current objects */
    for (cur_obj = hndl->objlist; cur_obj; cur_obj = cur_obj->next) {
        cur_obj->old = B_TRUE;
        cur_obj->new = B_FALSE;
    }

    /* read in object list */
    miscstat = hndl->p_obj_iter(hndl->proc_p, per_loadobj, hndl);
    /* reset libs_changed global var to indicated sync up done */
    _tnfctl_libs_changed = B_FALSE;
    if (miscstat) {
        /*
         * for INDIRECT_MODE or INTERNAL_MODE, we should never get
         * called when linkmaps are not consistent, so this is a real
         * error - return without setting lmap_ok.
         */
        if ((hndl->mode == INDIRECT_MODE) ||
                (hndl->mode == INTERNAL_MODE))
            return (TNFCTL_ERR_INTERNAL);

        assert(hndl->mode == DIRECT_MODE);
        /*
         * in DIRECT_MODE:
         * caller needs to call tnfctl_continue on BADLMAPSTATE
         * XXXX - the cast from int to prb_status_t is ok as
         * we know we are in DIRECT_MODE and we are calling our
         * own loadobject iterator function.
         */
        if ((prb_status_t) miscstat == PRB_STATUS_BADLMAPSTATE)
            *lmap_ok = B_FALSE;
        return (_tnfctl_map_to_errcode((prb_status_t) miscstat));
    }

    /*
     * find out about dlopens or dlcloses - In direct mode, there
     * can only be one since we monitor all dl activity.  The dl_evt
     * field is only used by tnfctl_continue().  In proc_service
     * mode or internal mode, the new_probe member indicates new probes
     * correctly.
     */
    *dl_evt = EVT_NONE;
    for (cur_obj = hndl->objlist; cur_obj; cur_obj = cur_obj->next) {
        if (cur_obj->old == B_TRUE) {
            *dl_evt = EVT_CLOSE;
            break;
        }
        if (cur_obj->new == B_TRUE) {
            *dl_evt = EVT_OPEN;
            break;
        }
    }

    /*
     * reset new_probe field only if there was a dlopen or dlclose
     */
    if (*dl_evt != EVT_NONE) {
        for (cur_obj = hndl->objlist; cur_obj;
                cur_obj = cur_obj->next) {
            cur_obj->new_probe = cur_obj->new;
        }
    }

    return (TNFCTL_ERR_NONE);
}


/*
 * search through all libraries and discover all probes in target
 * This function assumes all objects have been found and marked as
 * appropriate (new, old, or neither)
 */
tnfctl_errcode_t
_tnfctl_find_all_probes(tnfctl_handle_t *hndl)
{
    tnfctl_errcode_t    prexstat;
    int     num_probes, j;
    objlist_t   *cur_obj, *prev_obj, *tmp_obj;
    boolean_t   saw_new_probes = B_FALSE;

    prev_obj = NULL;
    cur_obj = hndl->objlist;
    while (cur_obj) {
        if (cur_obj->old == B_TRUE) {
            /* dlclosed library : stitch out probes in target */

            DBG_TNF_PROBE_3(_tnfctl_find_all_probes_1, "libtnfctl",
                "sunw%verbosity 1; sunw%debug 'lib dlclosed'",
                tnf_opaque, lib_baseaddr, cur_obj->baseaddr,
                tnf_string, lib_name, cur_obj->objname,
                tnf_long, lib_fd, cur_obj->objfd);

            prexstat = unlink_targ_obj_probes(hndl, cur_obj);
            if (prexstat)
                return (prexstat);
            free_obj_fields(cur_obj);
            /* remove this object from linked list */
            tmp_obj = cur_obj;
            cur_obj = cur_obj->next;
            if (prev_obj == NULL)
                hndl->objlist = cur_obj;
            else
                prev_obj->next = cur_obj;
            free(tmp_obj);
            continue;
        }

        if (cur_obj->new == B_TRUE) {
            /* dlopened library : read in probes */
            prexstat = get_num_probes(hndl, cur_obj, &num_probes);
            if (prexstat)
                return (prexstat);
            if (num_probes) {
                saw_new_probes = B_TRUE;
                cur_obj->probes = malloc(num_probes *
                    sizeof (prbctlref_t));
                if (cur_obj->probes == NULL)
                    return (TNFCTL_ERR_ALLOCFAIL);
                prexstat = read_probes_in_obj(hndl, cur_obj,
                    num_probes, hndl->num_probes);
                if (prexstat)
                    return (prexstat);
                cur_obj->min_probe_num = hndl->num_probes;
                /* increment num_probes */
                hndl->num_probes += num_probes;
                cur_obj->probecnt = num_probes;
                prexstat = link_targ_obj_probes(hndl, cur_obj);
                if (prexstat)
                    return (prexstat);
            }
        }
        prev_obj = cur_obj;
        cur_obj = cur_obj->next;
    }

#if 0
    for (cur_obj = hndl->objlist; cur_obj; cur_obj = cur_obj->next) {
            (void) fprintf(stderr, "%s 0x%08x %s fd=%d\n",
                (cur_obj->new) ? "*" : " ",
                cur_obj->baseaddr, cur_obj->objname,
                cur_obj->objfd);
    }
#endif

    /* call create_func for client data if we saw new probes */
    if (saw_new_probes && hndl->create_func) {
        for (cur_obj = hndl->objlist; cur_obj;
                        cur_obj = cur_obj->next) {
            tnfctl_probe_t *probe_handle;

            if (cur_obj->new == B_FALSE)
                continue;
            /* new object */
            for (j = 0; j < cur_obj->probecnt; j++) {
                probe_handle = cur_obj->probes[j].probe_handle;
                probe_handle->client_registered_data =
                    hndl->create_func(hndl, probe_handle);
            }
        }
    }

    return (TNFCTL_ERR_NONE);
}

/*
 * _tnfctl_free_objs_and_probes() - cleans up objects and probes
 */
void
_tnfctl_free_objs_and_probes(tnfctl_handle_t *hndl)
{
    objlist_t *obj, *tmp;

    NOTE(NO_COMPETING_THREADS_NOW)
    obj = hndl->objlist;
    while (obj) {
        free_obj_fields(obj);
        tmp = obj;
        obj = obj->next;
        free(tmp);
    }
    hndl->objlist = NULL;
    NOTE(COMPETING_THREADS_NOW)
}

/*
 * Free members of objlist_t
 */
static void
free_obj_fields(objlist_t *obj)
{
    int i;
    prbctlref_t *probe_p;

    for (i = 0; i < obj->probecnt; i++) {
        probe_p = &(obj->probes[i]);
        if (probe_p->attr_string)
            free(probe_p->attr_string);
        if (probe_p->probe_handle)
            probe_p->probe_handle->valid = B_FALSE;
    }
    if (obj->probes)
        free(obj->probes);
    obj->probecnt = 0;
    if (obj->objname)
        free(obj->objname);
    if (obj->objfd != -1)
        close(obj->objfd);
}

/*
 * _tnfctl_probes_traverse() - iterate over all probes by calling the
 * callback function supplied.
 */
tnfctl_errcode_t
_tnfctl_probes_traverse(tnfctl_handle_t *hndl,
    _tnfctl_traverse_probe_func_t func_p, void *calldata_p)
{
    tnfctl_errcode_t    prexstat;
    boolean_t   release_lock;
    objlist_t   *obj;
    int     j;

    /*LINTED statement has no consequent: else*/
    LOCK_SYNC(hndl, prexstat, release_lock);

    for (obj = hndl->objlist; obj; obj = obj->next) {
        for (j = 0; j < obj->probecnt; j++) {
            prexstat = (*func_p) (hndl, &(obj->probes[j]),
                            calldata_p);
            if (prexstat) {
                /*LINTED statement has no consequent: else*/
                UNLOCK(hndl, release_lock);
                return (prexstat);
            }
        }
    }

    /*LINTED statement has no consequent: else*/
    UNLOCK(hndl, release_lock);

    return (TNFCTL_ERR_NONE);
}

/*
 * function that is called by loadobject iterator function for every
 * loadobject.  If a new loadobject, add it to to our list.
 */
static int
per_loadobj(void *proc_p, const tnfctl_ind_obj_info_t *obj, void *cd)
{
    tnfctl_handle_t *hndl = cd;
    objlist_t   *entry_p, *cur_p, *next_p;

    if (entry_p = loadobj_find(hndl, obj)) {
        /* loadobject already exists */
        entry_p->old = B_FALSE;
        /* no need to close the objfd because iterator func will */

        /* successful return */
        return (0);
    }

    /* add new loadobject */
    entry_p = calloc(1, sizeof (objlist_t));

    entry_p->old = B_FALSE;
    entry_p->new = B_TRUE;
    entry_p->new_probe = B_TRUE;
    entry_p->objname = strdup(obj->objname);
    if (entry_p->objname == NULL)
        return (1);
    entry_p->baseaddr = obj->text_base;
    /* may have to actually open the fd */
    if (obj->objfd == -1) {
        entry_p->objfd = open(obj->objname, O_RDONLY);
        if (entry_p->objfd == -1)
            return (1);
    } else {
        /* dup the fd because iterator function will close it */
        entry_p->objfd = dup(obj->objfd);
        if (entry_p->objfd == -1)
            return (1);
    }

    entry_p->min_probe_num = 0;
    entry_p->probecnt = 0;
    entry_p->probes = NULL;
    entry_p->next = NULL;

    if (hndl->objlist == NULL) {
        hndl->objlist = entry_p;
    } else {
        /* add to end of list */
        next_p = hndl->objlist;
        while (next_p) {
            cur_p = next_p;
            next_p = next_p->next;
        }
        /* cur_p now points to last element on list */
        cur_p->next = entry_p;
    }

    return (0);
}

/*
 * check if this loadobject already exists in our linked list.
 */
static objlist_t *
loadobj_find(tnfctl_handle_t *hndl, const tnfctl_ind_obj_info_t *this_obj)
{
    objlist_t *obj;

    for (obj = hndl->objlist; obj; obj = obj->next) {
        if (obj->baseaddr == this_obj->text_base)
            return (obj);
    }
    return (NULL);
}

/*
 * find the number of probes in a loadobject
 */
static tnfctl_errcode_t
get_num_probes(tnfctl_handle_t *hndl, objlist_t *obj, int *num_probes)
{
    tnfctl_errcode_t    prexstat;
    link_args_t largs;
    tnfctl_elf_search_t search_info;

    DBG_TNF_PROBE_0(get_num_probes_1, "libtnfctl", "sunw%verbosity 1");

    largs.la_probename = PROBE_SYMBOL;
    largs.ret_val = 0;

    search_info.section_func = _tnfctl_traverse_rela;
    search_info.record_func = count_probes;
    search_info.record_data = &largs;

    prexstat = _tnfctl_traverse_object(obj->objfd, obj->baseaddr,
                        &search_info);
    if (prexstat)
        return (prexstat);

    DBG_TNF_PROBE_2(get_num_probes_2, "libtnfctl", "sunw%verbosity 1",
            tnf_long, num_probes, largs.ret_val,
            tnf_string, obj_name, obj->objname);

    *num_probes = largs.ret_val;
    return (TNFCTL_ERR_NONE);
}

/*
 * discover all probes in a loadobject and read it into our array.
 */
static tnfctl_errcode_t
read_probes_in_obj(tnfctl_handle_t *hndl, objlist_t *obj, ulong_t num_probes,
            ulong_t probe_base_num)
{
    tnfctl_errcode_t    prexstat;
    link_args2_t    largs2;
    tnfctl_elf_search_t search_info;

    DBG_TNF_PROBE_0(read_probes_in_obj_1, "libtnfctl", "sunw%verbosity 2");

    largs2.la_hndl = hndl;
    largs2.la_probename = PROBE_SYMBOL;
    largs2.la_obj = obj;
    largs2.la_index = 0;
    largs2.la_base = probe_base_num;

    search_info.section_func = _tnfctl_traverse_rela;
    search_info.record_func = read_a_probe;
    search_info.record_data = &largs2;

    prexstat = _tnfctl_traverse_object(obj->objfd, obj->baseaddr,
                        &search_info);
    if (prexstat)
        return (prexstat);

    return (TNFCTL_ERR_NONE);
}

/*
 * checks if this relocation entry is a probe and if so,
 * increments a counter for every probe seen
 */
/*ARGSUSED*/
static tnfctl_errcode_t
count_probes(char *name, uintptr_t addr, void *rel_entry,
    tnfctl_elf_search_t * search_info_p)
{
    link_args_t *largs_p = (link_args_t *) search_info_p->record_data;

    if (strcmp(name, largs_p->la_probename) == 0) {
        largs_p->ret_val++;
    }
    return (TNFCTL_ERR_NONE);
}

/*
 * checks if this relocation entry is a probe and if so, reads in info
 * on this probe
 */
/*ARGSUSED*/
static tnfctl_errcode_t
read_a_probe(char *name, uintptr_t addr, void *rel_entry,
    tnfctl_elf_search_t * search_info_p)
{
    link_args2_t    *largs2_p = (link_args2_t *) search_info_p->record_data;
    ulong_t     index = largs2_p->la_index;
    prbctlref_t *prbctl_p;
    tnfctl_handle_t *hndl = largs2_p->la_hndl;
    tnfctl_errcode_t    prexstat;
    int     miscstat;
    uintptr_t   attrs;

    assert((hndl->mode == INTERNAL_MODE) ?
        (MUTEX_HELD(&_tnfctl_lmap_lock)) : 1);

    if (strcmp(name, largs2_p->la_probename) != 0)
        return (TNFCTL_ERR_NONE);

    /* found a probe */
    prbctl_p = &(largs2_p->la_obj->probes[index]);
    prbctl_p->addr = addr;
    prbctl_p->probe_id = largs2_p->la_base + index;
    prbctl_p->obj = largs2_p->la_obj;
    largs2_p->la_index++;

    /* read in probe structure */
    miscstat = hndl->p_read(hndl->proc_p, addr,
        &prbctl_p->wrkprbctl, sizeof (prbctl_p->wrkprbctl));
    if (miscstat) {
        DBG((void) fprintf(stderr,
            "read_a_probe: read from target failed: %d\n",
            miscstat));
        return (TNFCTL_ERR_INTERNAL);
    }

    /*
     * dereference the attrs (read it into our address space only for
     * working copy)
     */
    attrs = (uintptr_t) prbctl_p->wrkprbctl.attrs;
    prexstat = _tnfctl_readstr_targ(hndl, attrs, &prbctl_p->attr_string);
    if (prexstat) {
        DBG((void) fprintf(stderr,
            "read_a_probe: _tnfctl_readstr_targ (attrs) failed: %s\n",
                tnfctl_strerror(prexstat)));
        return (prexstat);
    }

    DBG_TNF_PROBE_1(read_a_probe_2, "libtnfctl",
        "sunw%verbosity 1; sunw%debug 'found a probe'",
        tnf_string, probe, prbctl_p->attr_string);

    /* create probe handle */
    prbctl_p->probe_handle = calloc(1, sizeof (tnfctl_probe_t));
    if (prbctl_p->probe_handle == NULL)
        return (TNFCTL_ERR_ALLOCFAIL);
    prbctl_p->probe_handle->valid = B_TRUE;
    prbctl_p->probe_handle->probe_p = prbctl_p;
    /* link in probe handle into chain off tnfctl_handle_t */
    prbctl_p->probe_handle->next = hndl->probe_handle_list_head;
    hndl->probe_handle_list_head = prbctl_p->probe_handle;

    /*
     * if this is a "virgin" probe, set up probe to initial state
     * REMIND: Could defer this target write till we link the probes
     * together in target process in link_targ_obj_probes() i.e.
     * do the "write" only once.
     */
    if (prbctl_p->wrkprbctl.commit_func == NULL) {
        prbctl_p->wrkprbctl.probe_func =
                (tnf_probe_func_t) hndl->endfunc;
        prbctl_p->wrkprbctl.commit_func =
                (tnf_probe_func_t) hndl->commitfunc;
        prbctl_p->wrkprbctl.alloc_func =
                (tnf_probe_alloc_func_t) hndl->allocfunc;
        /*
         * update the probe in target to its initial state
         * Since the probe is disabled, it is ok to write it one
         * write command as opposed to updating each word individually
         */
        miscstat = hndl->p_write(hndl->proc_p, addr,
            &prbctl_p->wrkprbctl, sizeof (prbctl_p->wrkprbctl));
        if (miscstat)
            return (TNFCTL_ERR_INTERNAL);
    }

    return (TNFCTL_ERR_NONE);
}

/*
 * Link all the probes in a linked list in the target image in specified
 * object.  Also, link probes from previous object and next object into
 * this list.  The only
 * reason this is needed is because internally in the process,
 * tnf_probe_notify() that is called from libthread walks through all
 * probes substituting the test function
 * REMIND: find a way that we don't have to walk through probes internally.
 */
static tnfctl_errcode_t
link_targ_obj_probes(tnfctl_handle_t *hndl, objlist_t *cur)
{
    int i;
    prbctlref_t *probe_p;
    tnf_probe_control_t *next_probe;
    int miscstat;
    objlist_t *cur_tmp, *prev_w_probes, *next_w_probes;
    uintptr_t next_addr;

    /* find previous object that has probes */
    prev_w_probes = NULL;
    cur_tmp = hndl->objlist;
    while (cur_tmp != cur) {
        if (cur_tmp->probecnt != 0)
            prev_w_probes = cur_tmp;
        cur_tmp = cur_tmp->next;
    }

    /* find next object with probes */
    next_w_probes = NULL;
    cur_tmp = cur->next;
    while (cur_tmp != NULL) {
        if (cur_tmp->probecnt != 0)
            next_w_probes = cur_tmp;
        cur_tmp = cur_tmp->next;
    }

    /* link probes (except for last one) in order */
    for (i = 0; i < (cur->probecnt - 1); i++) {
        probe_p = &(cur->probes[i]);
        next_probe = (tnf_probe_control_t *) cur->probes[i+1].addr;
        probe_p->wrkprbctl.next = next_probe;
        miscstat = hndl->p_write(hndl->proc_p, probe_p->addr +
                offsetof(struct tnf_probe_control, next),
                &next_probe, sizeof (next_probe));
        if (miscstat)
            return (TNFCTL_ERR_INTERNAL);
    }

    next_probe = (tnf_probe_control_t *) cur->probes[0].addr;
    if (prev_w_probes == NULL) {
        /* adding as first object in list */
        next_addr = hndl->probelist_head;
    } else {
        probe_p = &(prev_w_probes->probes[prev_w_probes->probecnt - 1]);
        probe_p->wrkprbctl.next = next_probe;
        next_addr = probe_p->addr +
                offsetof(struct tnf_probe_control, next);
    }

    /* point next_addr to first probe in this object */
    miscstat = hndl->p_write(hndl->proc_p, next_addr,
            &next_probe, sizeof (next_probe));
    if (miscstat)
        return (TNFCTL_ERR_INTERNAL);

    /* link last probe in object */
    if (next_w_probes == NULL)
        next_probe = NULL;
    else {
        next_probe = (tnf_probe_control_t *)
                next_w_probes->probes[0].addr;
    }
    probe_p = &(cur->probes[cur->probecnt - 1]);
    probe_p->wrkprbctl.next = next_probe;
    miscstat = hndl->p_write(hndl->proc_p, probe_p->addr +
            offsetof(struct tnf_probe_control, next),
            &next_probe, sizeof (next_probe));
    if (miscstat)
        return (TNFCTL_ERR_INTERNAL);
    return (TNFCTL_ERR_NONE);
}

/*
 * An object has been closed.  Stitch probes around this object in
 * target image.
 */
static tnfctl_errcode_t
unlink_targ_obj_probes(tnfctl_handle_t *hndl, objlist_t *cur)
{
    prbctlref_t *probe_p;
    tnf_probe_control_t *next_probe;
    int miscstat;
    objlist_t *cur_tmp, *prev_w_probes, *next_w_probes;
    uintptr_t next_addr;

    /* find previous object that has probes */
    prev_w_probes = NULL;
    cur_tmp = hndl->objlist;
    while (cur_tmp != cur) {
        if (cur_tmp->probecnt != 0)
            prev_w_probes = cur_tmp;
        cur_tmp = cur_tmp->next;
    }

    /* find next object with probes */
    next_w_probes = NULL;
    cur_tmp = cur->next;
    while (cur_tmp != NULL) {
        if (cur_tmp->probecnt != 0)
            next_w_probes = cur_tmp;
        cur_tmp = cur_tmp->next;
    }

    if (next_w_probes == NULL)
        next_probe = NULL;
    else {
        next_probe = (tnf_probe_control_t *)
                next_w_probes->probes[0].addr;
    }

    if (prev_w_probes == NULL) {
        /* removing first object in list */
        next_addr = hndl->probelist_head;
    } else {
        probe_p = &(prev_w_probes->probes[prev_w_probes->probecnt - 1]);
        probe_p->wrkprbctl.next = next_probe;
        next_addr = probe_p->addr +
                offsetof(struct tnf_probe_control, next);
    }

    /* point next_addr to next_probe */
    miscstat = hndl->p_write(hndl->proc_p, next_addr,
            &next_probe, sizeof (next_probe));
    if (miscstat)
        return (TNFCTL_ERR_INTERNAL);
    return (TNFCTL_ERR_NONE);
}

/*
 * _tnfctl_flush_a_probe() - write a changed probe into the target process'
 * address space.
 */
tnfctl_errcode_t
_tnfctl_flush_a_probe(tnfctl_handle_t *hndl, prbctlref_t *ref_p, size_t offset,
            size_t size)
{
    tnfctl_errcode_t    prexstat;
    int         miscstat;

    /*
     * For internal control:
     * There is *no race* for finding the test function (between the time
     * we call find_test_func() and the time we assign it to a probe),
     * because tnfctl_internal_open() cannot be called from an init section
     * (look at man page of tnfctl_internal_open()).  And, after the init
     * section of libthread has run, we will always use the MT test
     * function.
     */

    if (hndl->mode == KERNEL_MODE) {
        prexstat = _tnfctl_prbk_flush(hndl, ref_p);
        if (prexstat)
            return (prexstat);
    } else {
        miscstat = hndl->p_write(hndl->proc_p,
            ref_p->addr + offset,
            ((char *)&(ref_p->wrkprbctl)) + offset, size);
        if (miscstat)
            return (TNFCTL_ERR_INTERNAL);
    }

    return (TNFCTL_ERR_NONE);
}