probe.c

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/*
 * Copyright (c) 2011, 2012, 2013, 2014 The University of Utah
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of
 * the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
 */

#include <stdlib.h>
#include <string.h>
#include <glib.h>

#include "common.h"
#include "log.h"

#include "dwdebug.h"
#include "dwdebug_priv.h"

#include "target_api.h"
#include "target.h"

#include "probe_api.h"
#include "probe.h"

/*
 * Local prototypes.
 */
static void action_finish_handling(struct action *action,
                   struct thread_action_context *tac);

/*
 * If the user doesn't supply pre/post handlers, and the probe has sinks
 * attached to it, we invoke these handlers to pass the event to the
 * sinks.  Users that write their own handlers should call these
 * handlers from within their handler, so that sinks can attach to their
 * handlers if desired.
 */
result_t probe_do_sink_pre_handlers (struct probe *probe,tid_t tid,
                     void *handler_data,struct probe *trigger,
                     struct probe *base) {
    struct probe *ptmp;
    GList *list;
    int retval = 0;
    int rc;

    if (probe->sinks) {
    vdebug(5,LA_PROBE,LF_PROBE,"");
    LOGDUMPPROBE_NL(5,LA_PROBE,LF_PROBE,probe);

    list = probe->sinks;
    while (list) {
        ptmp = (struct probe *)list->data;

        /*
         * Do this stuff regardless of if there's a prehandler or
         * not!  Why?  Because if we do it for the prehandler, we
         * have to do it for the posthandler too.  Since we can't
         * tell if we did it or didn't do it for the prehandler once
         * we get to the posthandler, we ALWAYS have to do it!
         */
        PROBE_SAFE_OP_ARGS(ptmp,values_notify_phase,tid,PHASE_PRE_START);

        /*
         * Signal each of the sinks, IF their threads match (thus a
         * sink can act as a filter on a thread id.
         */
        if (ptmp->pre_handler
        && (ptmp->tid == TID_GLOBAL 
            || ptmp->thread->tid == TID_GLOBAL 
            || ptmp->thread->tid == tid)
        && probe_filter_check(ptmp,tid,probe,0) == 0) {

        vdebug(8,LA_PROBE,LF_PROBE,"running pre handler for ");
        LOGDUMPPROBE_NL(8,LA_PROBE,LF_PROBE,probe);

        rc = ptmp->pre_handler(ptmp,tid,ptmp->handler_data,probe,base);
        if (rc == RESULT_ERROR) {
            probe_disable(ptmp);
            retval |= rc;
        }
        }
        else {
        vdebug(8,LA_PROBE,LF_PROBE,"not running pre handler for ");
        LOGDUMPPROBE(6,LA_PROBE,LF_PROBE,probe);
        vdebugc(8,LA_PROBE,LF_PROBE,"tid %d probe tid %d; sink tid %d\n",
            tid,probe->thread->tid,ptmp->thread->tid);
        }
        

        PROBE_SAFE_OP_ARGS(ptmp,values_notify_phase,tid,PHASE_PRE_END);

        list = g_list_next(list);
    }
    }

    return retval;
}

result_t probe_do_sink_post_handlers(struct probe *probe,tid_t tid,
                     void *handler_data,struct probe *trigger,
                     struct probe *base) {
    struct probe *ptmp;
    GList *list;
    int retval = 0;
    int rc;

    if (probe->sinks) {
    vdebug(5,LA_PROBE,LF_PROBE,"");
    LOGDUMPPROBE_NL(5,LA_PROBE,LF_PROBE,probe);

    list = probe->sinks;
    while (list) {
        ptmp = (struct probe *)list->data;

        PROBE_SAFE_OP_ARGS(ptmp,values_notify_phase,tid,PHASE_POST_START);

        /*
         * Signal each of the sinks, IF their threads match (thus a
         * sink can act as a filter on a thread id.
         */
        if (ptmp->post_handler
        && (ptmp->tid == TID_GLOBAL 
            || ptmp->thread->tid == TID_GLOBAL 
            || ptmp->thread->tid == tid)
        && probe_filter_check(ptmp,tid,probe,1) == 0) {

        vdebug(8,LA_PROBE,LF_PROBE,"running post handler for ");
        LOGDUMPPROBE_NL(8,LA_PROBE,LF_PROBE,probe);

        rc = ptmp->post_handler(ptmp,tid,ptmp->handler_data,probe,base);
        if (rc == RESULT_ERROR) {
            probe_disable(ptmp);
            retval |= rc;
        }
        }
        else {
        vdebug(8,LA_PROBE,LF_PROBE,"not running post handler for ");
        LOGDUMPPROBE(6,LA_PROBE,LF_PROBE,probe);
        vdebugc(8,LA_PROBE,LF_PROBE,"tid %d probe tid %d; sink tid %d\n",
            tid,probe->thread->tid,ptmp->thread->tid);
        }

        PROBE_SAFE_OP_ARGS(ptmp,values_notify_phase,tid,PHASE_POST_END);

        list = g_list_next(list);
    }
    }

    return retval;
}

static struct probepoint *__probepoint_create(struct target *target,ADDR addr,
                          struct memrange *range,
                          probepoint_type_t type,
                          probepoint_style_t style,
                          probepoint_whence_t whence,
                          probepoint_watchsize_t watchsize,
                          struct bsymbol *bsymbol,
                          ADDR symbol_addr) {
    struct probepoint *probepoint;

    probepoint = (struct probepoint *)malloc(sizeof(*probepoint));
    if (!probepoint) {
        verror("failed to allocate a new probepoint");
        return NULL;
    }
    memset(probepoint,0,sizeof(*probepoint));
    
    probepoint->addr = addr;
    probepoint->range = range;
    probepoint->target = target;
    probepoint->thread = NULL;
    probepoint->state = PROBE_DISABLED;

    probepoint->type = type;
    probepoint->style = probepoint->orig_style = style;
    probepoint->whence = whence;
    probepoint->watchsize = watchsize;

    if (bsymbol) {
    probepoint->bsymbol = bsymbol;
    RHOLD(bsymbol,probepoint);
    }
    probepoint->symbol_addr = symbol_addr;
    
    probepoint->debugregnum = -1;

    INIT_LIST_HEAD(&probepoint->probes);
    INIT_LIST_HEAD(&probepoint->simple_actions);
    INIT_LIST_HEAD(&probepoint->ss_actions);
    INIT_LIST_HEAD(&probepoint->complex_actions);

    if (target->ops->instr_can_switch_context) {
    if ((probepoint->can_switch_context = \
         target->ops->instr_can_switch_context(target,addr)) < 0) {
        vwarn("could not determine if instr at 0x%"PRIxADDR" can switch"
          " context; but continuing!\n",addr);
        probepoint->can_switch_context = 0;
    }
    }

    vdebug(5,LA_PROBE,LF_PROBEPOINT,"created ");
    LOGDUMPPROBEPOINT(5,LA_PROBE,LF_PROBEPOINT,probepoint);
    if (probepoint->can_switch_context) {
    vdebugc(5,LA_PROBE,LF_PROBEPOINT," (instr can switch context (0x%x)\n",
           probepoint->can_switch_context);
    }
    else
    vdebugc(5,LA_PROBE,LF_PROBEPOINT,"\n");

    return probepoint;
}

static struct probepoint *probepoint_create_break(struct target *target,
                          ADDR addr,
                          struct memrange *range,
                          probepoint_style_t style,
                          struct bsymbol *bsymbol,
                          ADDR symbol_addr) {
    struct probepoint *probepoint = __probepoint_create(target,addr,range,
                            PROBEPOINT_BREAK,style,
                            PROBEPOINT_EXEC,0,
                            bsymbol,symbol_addr);
    return probepoint;
}

static struct probepoint *probepoint_create_watch(struct target *target,
                          ADDR addr,
                          struct memrange *range,
                          probepoint_style_t style,
                          probepoint_whence_t whence,
                          probepoint_watchsize_t watchsize,
                          struct bsymbol *bsymbol,
                          ADDR symbol_addr) {
    if (style == PROBEPOINT_SW) {
    verror("software watchpoints not supported right now!\n");
    errno = EINVAL;
    return NULL;
    }

    return __probepoint_create(target,addr,range,PROBEPOINT_WATCH,style,
                   whence,watchsize,bsymbol,symbol_addr);
}

static void probepoint_free_internal(struct probepoint *probepoint) {
    struct probe *probe;
    struct probe *ptmp;
    struct action *action;
    struct action *atmp;
    REFCNT trefcnt;

    /* Destroy any actions it might have (probe_free does this too,
     * but this is much more efficient.
     */
    list_for_each_entry_safe(action,atmp,&probepoint->simple_actions,action) {
    action_cancel(action);
    RPUT(action,action,probepoint,trefcnt);
    }
    list_for_each_entry_safe(action,atmp,&probepoint->ss_actions,action) {
    action_cancel(action);
    RPUT(action,action,probepoint,trefcnt);
    }
    list_for_each_entry_safe(action,atmp,&probepoint->complex_actions,action) {
    action_cancel(action);
    RPUT(action,action,probepoint,trefcnt);
    }

    /* Destroy the probes. */
    list_for_each_entry_safe(probe,ptmp,&probepoint->probes,probe) {
    probe->probepoint = NULL;
    if (probe->autofree)
        probe_free(probe,0);
    }
    /* XXX: we could also go *up* the src/sink chain and destroy all the
     * sinks... should we?
     */

    if (probepoint->bsymbol) {
    RPUT(probepoint->bsymbol,bsymbol,probepoint,trefcnt);
    probepoint->bsymbol = NULL;
    }
}

static int __probepoint_remove(struct probepoint *probepoint,int force,
                   int nohashdelete) {
    struct target *target;
    tid_t tid,htid;
    int ret;
    struct thread_probepoint_context *tpc;
    int action_did_obviate = 0;
    int fake = 0;

    target = probepoint->target;

    /* Check if the probepoint has already been inserted; we do not want
     * to backup a previously inserted breakpoint.
     */
    if (probepoint->state == PROBE_DISABLED) {
    /* return success, the probepoint is already removed */
    vdebug(11,LA_PROBE,LF_PROBEPOINT,"");
    LOGDUMPPROBEPOINT(11,LA_PROBE,LF_PROBEPOINT,probepoint);
    vdebugc(11,LA_PROBE,LF_PROBEPOINT," already disabled\n");

        return 0;
    }

    /*
     * If the style is software, and it's a watchpoint, forget it; we
     * don't support that right now.
     */
    if (probepoint->style == PROBEPOINT_SW 
    && probepoint->type == PROBEPOINT_WATCH) {
    verror("no software watchpoint support!\n");
    errno = EINVAL;
    return 1;
    }

    if (!target_is_open(target)) {
    vdebug(8,LA_PROBE,LF_PROBEPOINT,
           "target is not attached; emulating probepoint removal ");
    LOGDUMPPROBEPOINT_NL(8,LA_PROBE,LF_PROBEPOINT,probepoint);
    fake = 1;
    }
    else {
    vdebug(5,LA_PROBE,LF_PROBEPOINT,"removing ");
    LOGDUMPPROBEPOINT_NL(5,LA_PROBE,LF_PROBEPOINT,probepoint);
    }

    /* 
     * If the probepoint is not currently being handled, simply remove
     * it.  Otherwise, we have to handle complex cases!
     */
    if (probepoint->state == PROBE_BP_SET) {
    vdebug(7,LA_PROBE,LF_PROBE,"doing easy removal of ");
    LOGDUMPPROBEPOINT(7,LA_PROBE,LF_PROBE,probepoint);
    vdebugc(7,LA_PROBE,LF_PROBE,"; removing probepoint!\n");
    }
    /*
     * Handle complex stuff :).
     */
    else if (!force && !fake) {
    vwarn("probepoint being handled (state %d); not forcing removal yet!\n",
          probepoint->state);
    errno = EAGAIN;
    return -1;
    }
    else {
    if (probepoint->state == PROBE_ACTION_RUNNING) {
        if (!fake)
        vwarn("forced probepoint removal while it is running action;"
              " trying to clean up normally!\n");
        /* We need to remove the action code, if any, reset the EIP
         * to what it would have been if we had just hit the BP, and
         * then do the normal breakpoint removal.
         */
        tpc = probepoint->tpc;

        if (!fake && target_enable_sw_breakpoint(target,tpc->thread->tid,
                             probepoint->mmod)) {
        verror("could not reenable sw breakpoint to remove action;"
               " badness will probably ensue!\n");
        probepoint->state = PROBE_DISABLED;
        }
        else {
        probepoint->state = PROBE_BP_SET;
        }

        if (tpc->action_obviated_orig)
        action_did_obviate = 1;

        /* NULL these out to be safe. */
        tpc->tac.action = NULL;
        tpc->tac.stepped = 0;
        tpc->action_obviated_orig = 0;
    }
    else if (probepoint->state == PROBE_BP_PREHANDLING) {
        vwarnopt(5,LA_PROBE,LF_PROBEPOINT,
             "force probepoint removal while prehandling it;"
             " trying to clean up normally!\n");
    }
    else if (probepoint->state == PROBE_BP_ACTIONHANDLING) {
        vwarnopt(5,LA_PROBE,LF_PROBEPOINT,
             "force probepoint removal while handling an action;"
             " trying to clean up normally!\n");
    }
    else if (probepoint->state == PROBE_BP_POSTHANDLING) {
        vwarnopt(5,LA_PROBE,LF_PROBEPOINT,
             "force probepoint removal while posthandling it;"
             " trying to clean up normally!\n");
    }
    else if (probepoint->state == PROBE_INSERTING) {
        vwarnopt(5,LA_PROBE,LF_PROBEPOINT,
             "forced probepoint removal while it is inserting;"
             " trying to clean up normally!\n");
        probepoint->state = PROBE_BP_SET;
    }

    /*
     * If we're doing initial BP handling, reset EIP to the
     * probepoint addr; else if we're doing BP handling after the
     * single step, *don't* reset IP, since we already did the
     * original instruction.  UNLESS we were executing an action
     * that obviated the original code control flow -- then we
     * replace the original code below, BUT DO NOT update EIP!
     *
     * Also cancel any singlesteps that (might) be happening!  We
     * don't quite track if we have stepped a thread, so just do it
     * if we *might* have (i.e., if the probepoint is being handled
     * for a thread).
     */
    if (probepoint->state != PROBE_DISABLED) {
        /* Reset EIP to the right thing. */
        if (!target->no_adjust_bp_ip
        && (probepoint->state == PROBE_BP_PREHANDLING 
            || probepoint->state == PROBE_BP_ACTIONHANDLING 
            || probepoint->state == PROBE_ACTION_RUNNING
            || probepoint->state == PROBE_ACTION_DONE)
        && !action_did_obviate
        && probepoint->type != PROBEPOINT_WATCH) {
        /* We still must execute the original instruction. */
        /* BUT NOT for watchpoints!  We do not know anything
         * about the original instruction.
         */
        tid = probepoint->thread->tid;

        if (!fake && target_write_reg(target,tid,
                     target->ipregno,probepoint->addr)) {
            verror("could not reset IP to bp addr 0x%"PRIxADDR" for"
               " forced breakpoint remove; badness will probably"
               " ensue!\n",
               probepoint->addr);
        }
        }

        /* Cancel any executing single step! */
        if (probepoint->tpc) {
        if (target_singlestep_end(target,probepoint->tpc->thread->tid))
            verror("could not stop single stepping target tid %"PRIiTID
               " after failed sstep for breakpoint!\n",
               probepoint->tpc->thread->tid);
        }
    }
    }

    /*
     * If we're going to remove it, do it!
     */

    /*
     * If it's hardware, use the target API to remove it.
     */
    if (probepoint->style == PROBEPOINT_HW) {
    /*
     * XXX: bit of a lie here; if we're detached, we should still
     * try to clean up hw probepoint state somewhere...
     */
    if (!fake && probepoint->debugregnum > -1) {
        htid = probepoint->thread->tid;

        if (probepoint->type == PROBEPOINT_BREAK) {
        if ((ret = target_unset_hw_breakpoint(target,htid,
                              probepoint->debugregnum))) {
            verror("failure while removing hw breakpoint; cannot recover!\n");
        }
        else {
            vdebug(4,LA_PROBE,LF_PROBEPOINT,"removed HW break ");
            LOGDUMPPROBEPOINT_NL(4,LA_PROBE,LF_PROBEPOINT,probepoint);
        }
        }
        else {
        if ((ret = target_unset_hw_watchpoint(target,htid,
                              probepoint->debugregnum))) {
            verror("failure while removing hw watchpoint; cannot recover!\n");
        }
        else {
            vdebug(4,LA_PROBE,LF_PROBEPOINT,"removed HW watch ");
            LOGDUMPPROBEPOINT_NL(4,LA_PROBE,LF_PROBEPOINT,probepoint);
        }
        }
    }
    else 
        ret = 0;

    if (ret) 
        return 1;
    else if (!nohashdelete)
        target_remove_probepoint(target,probepoint->thread,probepoint);

    probepoint->debugregnum = -1;
    }
    /*
     * Otherwise do software.  NB: we might get here twice; so make sure
     * the probepoint is still associated with a thread.  If not, don't
     * try again to remove it from the target.
     */
    else if (probepoint->thread) {
    if (!fake) {
        /* restore the original instruction */
        if (target_remove_sw_breakpoint(target,probepoint->thread->tid,
                        probepoint->mmod)) {
        verror("could not remove SW break at 0x%"PRIxADDR"\n",
               probepoint->addr);
        return 1;
        }

        probepoint->mmod = NULL;

        vdebug(4,LA_PROBE,LF_PROBEPOINT,"removed SW break ");
        LOGDUMPPROBEPOINT_NL(4,LA_PROBE,LF_PROBEPOINT,probepoint);
    }

    if (!nohashdelete)
        target_remove_probepoint(target,probepoint->thread,probepoint);
    }

    probepoint->state = PROBE_DISABLED;

    vdebug(2,LA_PROBE,LF_PROBEPOINT,"removed ");
    LOGDUMPPROBEPOINT_NL(2,LA_PROBE,LF_PROBEPOINT,probepoint);
    /*
     * This is just in case it was registered with PROBEPOINT_FASTEST;
     * we need to make sure if it gets re-registered that we make the
     * choice of FASTEST again at that time.
     *
     * NB: this *must* come after calling target_remove_probepoint!
     */
    if (probepoint->style != probepoint->orig_style) {
    vdebug(2,LA_PROBE,LF_PROBEPOINT,"removed (style was %d; now %d)",
           probepoint->style,probepoint->orig_style);

    probepoint->style = probepoint->orig_style;
    }
    else
    vdebug(2,LA_PROBE,LF_PROBEPOINT,"\n");

    return 0;
}

static void probepoint_free(struct probepoint *probepoint) {
    __probepoint_remove(probepoint,0,0);

    probepoint_free_internal(probepoint);

    vdebug(5,LA_PROBE,LF_PROBEPOINT,"freed ");
    LOGDUMPPROBEPOINT_NL(5,LA_PROBE,LF_PROBEPOINT,probepoint);

    free(probepoint);
}

/* We need this in case the target needs to quickly remove all the
 * probes (i.e., on a signal) -- and in that case, we have to let the
 * target remove the probepoint from its hashtables itself.
 *
 * NB: this *forces* the removal of the probepoint, even if it is being
 * handled, because we are forcing a removal from external.
 */
void probepoint_free_ext(struct probepoint *probepoint) {
    __probepoint_remove(probepoint,1,1);

    probepoint_free_internal(probepoint);

    vdebug(5,LA_PROBE,LF_PROBEPOINT,"freed (ext) ");
    LOGDUMPPROBEPOINT_NL(5,LA_PROBE,LF_PROBEPOINT,probepoint);

    free(probepoint);
}

/*
 * Note: you *must* pass the target_thread whose debug registers need to
 * be written -- that means if TID_GLOBAL means a "real" thread on a
 * target, like Xen, we need to modify the global thread's debug
 * register state.  For the ptrace target, where the TID_GLOBAL thread
 * might be an alias for a real "primary" thread, we need to *not* have
 * the global thread supplied here, but instead the real thread that is
 * being aliased.
 *
 * So, this comment is just to highlight this issue for
 * __probepoint_insert.  In other functions in this probe library, once
 * a probe is inserted, we carefully use the probepoint->thread->tid tid
 * value for making hardware debug register state changes, if the
 * probepoint is hardware.
 */
static int __probepoint_insert(struct probepoint *probepoint,
                   struct target_thread *tthread) {
    struct target *target;
    tid_t tid;
    int ret;
    REG reg;

    target = probepoint->target;
    tid = tthread->tid;

    /* Check if the probepoint has already been inserted; we do not want
     * to backup a previously inserted breakpoint.
     */
    if (probepoint->state != PROBE_DISABLED) {
    /* return success, the probepoint is already being managed */
    vdebug(11,LA_PROBE,LF_PROBEPOINT,"");
    LOGDUMPPROBEPOINT(9,LA_PROBE,LF_PROBEPOINT,probepoint);
    vdebugc(11,LA_PROBE,LF_PROBEPOINT," already inserted\n");

        return 0;
    }

    if (!target_is_open(target)) {
    verror("target %d is not attached!\n",target->id);
    return 1;
    }

    vdebug(5,LA_PROBE,LF_PROBEPOINT,"inserting ");
    LOGDUMPPROBEPOINT_NL(5,LA_PROBE,LF_PROBEPOINT,probepoint);

    probepoint->state = PROBE_INSERTING;

    /*
     * Check to see if there are any hardware resources; use them if so.
     */
    if (probepoint->style == PROBEPOINT_FASTEST) {
    if ((reg = target_get_unused_debug_reg(target,tid)) > -1) {
        probepoint->style = PROBEPOINT_HW;
        probepoint->debugregnum = reg;

        vdebug(3,LA_PROBE,LF_PROBEPOINT,"using HW reg %d for ",reg);
        LOGDUMPPROBEPOINT_NL(3,LA_PROBE,LF_PROBEPOINT,probepoint);
    }
    else {
        probepoint->style = PROBEPOINT_SW;

        vdebug(3,LA_PROBE,LF_PROBEPOINT,"using SW for FASTEST ");
        LOGDUMPPROBEPOINT_NL(3,LA_PROBE,LF_PROBEPOINT,probepoint);
    }
    }
    else if (probepoint->style == PROBEPOINT_HW) {
    if ((reg = target_get_unused_debug_reg(target,tid)) > -1) {
        probepoint->debugregnum = reg;

        vdebug(3,LA_PROBE,LF_PROBEPOINT,"using HW reg %d for ",reg);
        LOGDUMPPROBEPOINT_NL(3,LA_PROBE,LF_PROBEPOINT,probepoint);
    }
    else {
        vwarn("could not get a debug reg!\n");
        errno = ENOMEM;
        probepoint->state = PROBE_DISABLED;
        return 1;
    }
    }

    /*
     * If the style is software, and it's a watchpoint, forget it; we
     * don't support that right now.
     */
    if (probepoint->style == PROBEPOINT_SW 
    && probepoint->type == PROBEPOINT_WATCH) {
    verror("no software watchpoint support!\n");
    errno = EINVAL;
    probepoint->state = PROBE_DISABLED;
    return 1;
    }

    /*
     * If it's hardware, use the target API to insert it.
     */
    if (probepoint->style == PROBEPOINT_HW) {
    if (probepoint->type == PROBEPOINT_BREAK) {
        if ((ret = target_set_hw_breakpoint(target,tid,probepoint->debugregnum,
                        probepoint->addr))) {
        verror("failure inserting hw breakpoint!\n");
        }
        else {
        vdebug(7,LA_PROBE,LF_PROBEPOINT,"inserted hw break at ");
        LOGDUMPPROBEPOINT_NL(7,LA_PROBE,LF_PROBEPOINT,probepoint);
        }
    }
    else {
        if ((ret = target_set_hw_watchpoint(target,tid,probepoint->debugregnum,
                        probepoint->addr,
                        probepoint->whence,
                        probepoint->watchsize))) {
        verror("failure inserting hw watchpoint!\n");
        }
        else {
        vdebug(7,LA_PROBE,LF_PROBEPOINT,"inserted hw watch at ");
        LOGDUMPPROBEPOINT_NL(7,LA_PROBE,LF_PROBEPOINT,probepoint);
        }
    }

    if (ret) {
        probepoint->state = PROBE_DISABLED;
        return 1;
    }
    }
    /* Otherwise do software. */
    else {
    probepoint->mmod = target_insert_sw_breakpoint(target,tthread->tid,
                               probepoint->addr);
    if (!probepoint->mmod) {
        verror("could not insert sw breakpoint at 0x%"PRIxADDR"\n",
           probepoint->addr);
        probepoint->state = PROBE_DISABLED;
        return 1;
    }

    vdebug(3,LA_PROBE,LF_PROBEPOINT,"inserted SW ");
    LOGDUMPPROBEPOINT_NL(3,LA_PROBE,LF_PROBEPOINT,probepoint);
    }

    target_insert_probepoint(target,tthread,probepoint);
    probepoint->state = PROBE_BP_SET;

    vdebug(2,LA_PROBE,LF_PROBEPOINT,"inserted ");
    LOGDUMPPROBEPOINT_NL(2,LA_PROBE,LF_PROBEPOINT,probepoint);

    return 0;
}

struct probe *probe_create(struct target *target,tid_t tid,struct probe_ops *pops,
               const char *name,
               probe_handler_t pre_handler,
               probe_handler_t post_handler,
               void *handler_data,int autofree,int tracked) {
    struct probe *probe;
    struct target_thread *tthread;

    if (!(tthread = target_lookup_thread(target,tid))) {
    verror("thread %"PRIiTID" not loaded yet?\n",tid);
    return NULL;
    }

    probe = (struct probe *)malloc(sizeof(*probe));
    if (!probe) {
        verror("failed to allocate a new probe\n");
        return NULL;
    }
    memset(probe,0,sizeof(*probe));
    probe->id = -1;

    probe->name = (name) ? strdup(name) : NULL;
    probe->pre_handler = pre_handler;
    probe->post_handler = post_handler;
    probe->handler_data = handler_data;
    probe->enabled = 0; // disabled at first
    probe->autofree = autofree;
    probe->tracked = tracked;
    probe->ops = pops;
    probe->tid = tid;

    target_attach_probe(target,tthread,probe);

    if (PROBE_SAFE_OP(probe,init)) {
    verror("probe %s init failed, calling fini!\n",probe->name);
    PROBE_SAFE_OP(probe,fini);
    if (name)
        free(probe->name);
    free(probe);
    return NULL;
    }

    vdebug(5,LA_PROBE,LF_PROBE,"initialized ");
    LOGDUMPPROBE_NL(5,LA_PROBE,LF_PROBE,probe);

    return probe;
}

int probe_free(struct probe *probe,int force) {
    REFCNT trefcnt;
    GList *list;
    struct probe *sink;

    vdebug(5,LA_PROBE,LF_PROBE,"");
    LOGDUMPPROBE_NL(5,LA_PROBE,LF_PROBE,probe);

    if (probe->sinks && !force) {
    vwarnopt(9,LA_TARGET,LF_PROBE,
         "could not free probe %s with sinks remaining!\n",
         probe->name);
    return -1;
    }
    else if (probe->probepoint && !force) {
    vwarnopt(9,LA_TARGET,LF_PROBE,
         "could not free probe %s with probepoint remaining!\n",
         probe->name);
    return -1;
    }
    
    if (probe->sinks) {
    vwarn("forcefully freeing probe %s that had sinks remaining;"
          " removing this source from those sinks!\n",
          probe->name);

    list = probe->sinks;
    while (list) {
        sink = (struct probe *)list->data;

        if (!sink->sources) {
        /* This would be weird, but just ignore it. */
        vwarn("sink probe %s has no sources; although probe %s thinks"
              " it's a source -- BUG!\n",sink->name,probe->name);
        continue;
        }

        sink->sources = g_list_remove(sink->sources,probe);

        if (!sink->sources || g_list_length(sink->sources) == 0) {
        /* Only can call unregistered() if @probe was the last sink. */
        if (PROBE_SAFE_OP(sink,unregistered)) {
            verror("probe %s: unregistered failed!\n",
               sink->name);
        }
        }

        /* NB: we cannot free the sink!  The probe_free() function might
         * call probe_unregister_source*(), so we cannot free a sink we
         * might be freeing -- it might free the source we are
         * freeing in this function right now!  probe_free() can
         * only go downwards.
         */
        //if (sink->autofree) 
        //  return probe_free(sink,force);

        list = g_list_next(list);
    }

    g_list_free(probe->sinks);
    probe->sinks = NULL;
    }

    /* If we still need to unregister, we call probe_unregister, which
     * will call us again if the probe was an autofree probe.  So, if it
     * is an autofree probe, let probe_unregister call us again if it
     * succeeds.  If it fails, and we're forcing the free, do it anyway.
     */
    if (probe->probepoint || probe->sources) {
    if (!probe_unregister(probe,force)) {
        if (probe->autofree)
        return 0;
    }
    else {
        if (force) 
        verror("probe_unregister %s failed, forcing free to continue\n",
               probe->name);
        else {
        verror("probe_unregister %s failed, not forcing!\n",probe->name);
        return -1;
        }
    }
    }

    if (probe->pre_filter) {
    target_nv_filter_free(probe->pre_filter);
    probe->pre_filter = NULL;
    }
    if (probe->post_filter) {
    target_nv_filter_free(probe->post_filter);
    probe->post_filter = NULL;
    }

    if (probe->values) {
    PROBE_SAFE_OP(probe,values_free);
    probe->values = NULL;
    }

    if (PROBE_SAFE_OP(probe,fini)) {
    verror("probe %s fini failed, aborting!\n",probe->name);
    return -1;
    }

    if (probe->target) 
    target_detach_probe(probe->target,probe);

    if (probe->bsymbol) {
    RPUT(probe->bsymbol,bsymbol,probe,trefcnt);
    probe->bsymbol = NULL;
    }

    vdebug(5,LA_PROBE,LF_PROBE,"almost done: ");
    LOGDUMPPROBE_NL(5,LA_PROBE,LF_PROBE,probe);

    if (probe->name)
    free(probe->name);
    free(probe);

    return 0;
}

void probe_rename(struct probe *probe,const char *name) {
    vdebug(5,LA_PROBE,LF_PROBE,"renaming ");
    LOGDUMPPROBE_NL(5,LA_PROBE,LF_PROBE,probe);

    if (probe->name)
    free(probe->name);

    probe->name = (name) ? strdup(name) : NULL;

    vdebugc(5,LA_PROBE,LF_PROBE," to ");
    LOGDUMPPROBE_NL(5,LA_PROBE,LF_PROBE,probe);

}

int probe_hard_disable(struct probe *probe,int force) {
    struct probe *ptmp;
    GList *list;
    GList *list2;
    int anyenabled = 0;
    int rc = 0;

    list = probe->sources;
    while (list) {
    ptmp = (struct probe *)list->data;

    /* Disable recursively *if* the source doesn't have any
     * enabled sinks.
     */
    if (probe_enabled(ptmp)) {
        list2 = ptmp->sinks;
        anyenabled = 0;
        while (list2) {
        if (((struct probe *)(list->data))->enabled) {
            ++anyenabled;
        }
        list2 = g_list_next(list2);
        }
        if (!anyenabled || force) {
        if (force) {
            vdebug(3,LA_PROBE,LF_PROBE,"forcibly hard disabling source probe");
            LOGDUMPPROBE(3,LA_PROBE,LF_PROBE,ptmp);
            vdebug(3,LA_PROBE,LF_PROBE," although it has enabled sink!\n");
        }
        rc += probe_hard_disable(ptmp,force);
        }
        else if (anyenabled) {
        vdebug(3,LA_PROBE,LF_PROBE,"not forcibly hard disabling source probe");
        LOGDUMPPROBE(3,LA_PROBE,LF_PROBE,ptmp);
        vdebug(3,LA_PROBE,LF_PROBE," because it has enabled sink(s)!\n");
        ++rc;
        }
        list = g_list_next(list);
    }
    }

    if (probe_is_base(probe) && __probepoint_remove(probe->probepoint,force,0)) {
    verror("failed to remove probepoint under probe (%d)\n!",force);
    ++rc;
    }

    return rc;
}

int probe_hard_enable(struct probe *probe) {
    struct probe *ptmp;
    GList *list;
    int rc = 0;

    /* Do it for all the sources. */
    list = probe->sources;
    while (list) {
    ptmp = (struct probe *)list->data;

    rc += probe_hard_enable(ptmp);

    list = g_list_next(list);
    }

    /* If we have a probepoint directly underneath, do it. */
    if (probe_is_base(probe) 
    && __probepoint_insert(probe->probepoint,probe->thread)) {
    verror("failed to insert probepoint under probe\n!");
    ++rc;
    }

    return rc;
}

static int __probe_unregister(struct probe *probe,int force,int onlyone) {
    struct probepoint *probepoint = probe->probepoint;
    struct target *target = probe->target;
    target_status_t status;
    struct action *action;
    struct action *tmp;
    struct probe *ptmp;
    GList *list;
    REFCNT trefcnt;

    vdebug(5,LA_PROBE,LF_PROBE,"");
    LOGDUMPPROBE(5,LA_PROBE,LF_PROBE,probe);
    vdebugc(5,LA_PROBE,LF_PROBE,"(force=%d,onlyone=%d)\n",force,onlyone);

    if (probe->sources) 
    vdebug(5,LA_PROBE,LF_PROBE,"detaching probe %s from sources\n",probe->name);

    if (probe->sinks && !force) {
    verror("could not unregister a probe that had sinks remaining!\n");
    return -1;
    }
    else if (probe->sinks) {
    vwarn("forcefully unregistering a probe that had sinks remaining!\n");
    }

    /* Target must be paused (if it is attached!) before we do anything. */
    if (target_is_open(target)) {
    status = target_status(target);
    if (status != TSTATUS_PAUSED && status != TSTATUS_EXITING) {
        verror("target not paused (%d), cannot remove!\n",status);
        errno = EINVAL;
        return -1;
    }
    }

    /* Disable it (and its sources if necessary). */
    if (onlyone) 
    probe_disable_one(probe);
    else 
    probe_disable(probe);

    if (probepoint) {
    /* Remove the probe from the probepoint's list. */
    list_del(&probe->probe);
    probe->probepoint = NULL;

    /* Cancel (and possibly destroy) any actions it might have. */
    list_for_each_entry_safe(action,tmp,&probepoint->simple_actions,action) {
        action_cancel(action);
        RPUT(action,action,probepoint,trefcnt);
    }
    list_for_each_entry_safe(action,tmp,&probepoint->ss_actions,action) {
        action_cancel(action);
        RPUT(action,action,probepoint,trefcnt);
    }
    list_for_each_entry_safe(action,tmp,&probepoint->complex_actions,action) {
        action_cancel(action);
        RPUT(action,action,probepoint,trefcnt);
    }
    }

    /* If we are a source on somebody's sink list, remove ourselves! */
    if (probe->sinks) {
    list = probe->sinks;
    while (list) {
        ptmp = (struct probe *)list->data;
        ptmp->sources = g_list_remove(ptmp->sources,probe);
        list = g_list_next(list);
    }
    probe->sinks = NULL;
    }

    /* Unregister from any sources. */
    if (probe->sources) {
    list = probe->sources;
    while (list) {
    vdebug(5,LA_PROBE,LF_PROBE,"removing source\n");
        ptmp = (struct probe *)list->data;
        /* We MUST get the next ptr before calling the
         * probe_unregister_source* functions, because they will
         * remove our element!
         */
        list = g_list_next(list);
        /* Unregister from the sources, possibly recursively. */
        if (onlyone)
        probe_unregister_source_one(probe,ptmp,force);
        else 
        probe_unregister_source(probe,ptmp,force);
    }
    g_list_free(probe->sources);
    probe->sources = NULL;
    vdebug(5,LA_PROBE,LF_PROBE,"probe sources removed\n");
    }

    if (probe->bsymbol) {
    bsymbol_release(probe->bsymbol);
    probe->bsymbol = NULL;
    }

    /* At this point, the probe is unregistered; what remains is to
     * remove its probepoint, if necessary, and we don't have to wait to
     * let the user know.
     */
    if (PROBE_SAFE_OP(probe,unregistered)) {
    verror("probe '%s': unregistered failed, aborting\n",probe->name);
    return -1;
    }

    /* Free the probe if it is an autofree probe. */
    if (probe->autofree)
    if (probe_free(probe,force))
        verror("could not autofree probe; continuing anyway!\n");

    /* If it's just a source/sink probe, we're done; otherwise, try to
     * remove the probepoint too if no one else is using it.
     */
    if (!probepoint) 
    return 0;

    /* If this is the last probe at this probepoint, remove the
     * probepoint too -- IF possible, or IF forced!
     */
    if (!list_empty(&probepoint->probes)) 
    return 0;

    vdebug(5,LA_PROBE,LF_PROBE,"no more probes at ");
    LOGDUMPPROBEPOINT(5,LA_PROBE,LF_PROBE,probepoint);
    vdebugc(5,LA_PROBE,LF_PROBE,"; removing probepoint!\n");

    if (!__probepoint_remove(probepoint,force,0))
    probepoint_free(probepoint);
    else if (force) {
    verror("probepoint_remove failed, but force freeing!\n");
    target_remove_probepoint(target,probepoint->thread,probepoint);
    probepoint_free(probepoint);
    return -1;
    }
    else {
    verror("probepoint_remove failed; not force freeing!\n");
    return -1;
    }

    return 0;
}

/*
 * Unregisters a probe.
 * Upon successful completion, a value of 0 is returned. Otherwise, a value
 * of -1 is returned and the global integer variable errno is set to indicate 
 * the error.
 */
int probe_unregister(struct probe *probe,int force) {
    return __probe_unregister(probe,force,0);
}

int probe_unregister_one(struct probe *probe,int force) {
    return __probe_unregister(probe,force,1);
}

int probe_unregister_source(struct probe *sink,struct probe *src,int force) {
    target_status_t status;
    struct target *target = sink->target;

    if (!sink->sources) {
    verror("probe %s has no sources!\n",sink->name);
    return -1;
    }

    /* Target must be paused (if attached) before we do anything. */
    if (target_is_open(target)) {
    status = target_status(target);
    if (status != TSTATUS_PAUSED && status != TSTATUS_EXITING) {
        verror("target not paused (%d), cannot remove!\n",status);
        errno = EINVAL;
        return -1;
    }
    }

    sink->sources = g_list_remove(sink->sources,src);
    src->sinks = g_list_remove(src->sinks,sink);

    /* Do it recursively! */
    if (src->autofree && !src->sinks)
    __probe_unregister(src,force,0);

    if (PROBE_SAFE_OP(sink,unregistered)) {
    verror("probe %s: unregistered failed, aborting\n",sink->name);
    return -1;
    }

    /* NB: we cannot free the sink!  The probe_free() function might
     * call probe_unregister_source*(), so we cannot free a sink we
     * might be freeing.  probe_free() can only go downwards.
     */
    //if (sink->autofree) 
    //  return probe_free(sink,force);

    return 0;
}

int probe_unregister_source_one(struct probe *sink,struct probe *src,
                int force) {
    if (!sink->sources) {
    verror("probe %s has no sources!\n",sink->name);
    return -1;
    }

    sink->sources = g_list_remove(sink->sources,src);
    src->sinks = g_list_remove(src->sinks,sink);

    if (PROBE_SAFE_OP(sink,unregistered)) {
    verror("probe %s: unregistered failed, aborting\n",sink->name);
    return -1;
    }

    /* NB: we cannot free the sink!  The probe_free() function might
     * call probe_unregister_source*(), so we cannot free a sink we
     * might be freeing.  probe_free() can only go downwards.
     */
    //if (sink->autofree) 
    //  return probe_free(sink,force);

    return 0;
}

/*
 * This function always frees its probes, BUT the underlying probepoints
 * might fail to be freed.  If so, we return the number of probepoints
 * that failed to free (note that if other probes are attached, those
 * probepoints are not freed and it's not an error).
 */
int probe_unregister_batch(struct target *target,struct probe **probelist,
               int listlen,int force) {
    int i;
    int retval = 0;
    target_status_t status;

    if (!probelist)
    return -1;
    if (!listlen) 
    return 0;

    /* Target must be paused before we do anything. */
    status = target_status(target);
    if (status != TSTATUS_PAUSED && status != TSTATUS_EXITING) {
        verror("target not paused!\n");
    errno = EINVAL;
    return -1;
    }

    for (i = 0; i < listlen; ++i) {
    /* allow sparse lists */
    if (probelist[i] == NULL)
        continue;

    if (__probe_unregister(probelist[i],force,1)) {
        ++retval;
    }
    probelist[i] = NULL;
    }

    return retval;
}

struct probe *__probe_register_addr(struct probe *probe,ADDR addr,
                    struct memrange *range,
                    probepoint_type_t type,
                    probepoint_style_t style,
                    probepoint_whence_t whence,
                    probepoint_watchsize_t watchsize,
                    struct bsymbol *bsymbol,ADDR symbol_addr) {
    struct probepoint *probepoint;
    int created = 0;
    struct target *target = probe->target;
    target_status_t status;
    loctype_t ltrc;
    struct location tloc;
    struct target_location_ctxt *tlctxt;

    if (type == PROBEPOINT_WATCH && style == PROBEPOINT_SW) {
    verror("software watchpoints are unsupported!\n");
    errno = EINVAL;
    goto errout;
    }

    /* Target must be paused before we do anything. */
    status = target_status(target);
    if (status != TSTATUS_PAUSED && status != TSTATUS_EXITING) {
        verror("target not paused (%d)!\n",status);
    errno = EINVAL;
    goto errout;
    }

    /* If the user has associated a bound symbol with this probe
     * registration, try to look up its start addr (and grab the range
     * if we can).
     */
    if (bsymbol) {
    memset(&tloc,0,sizeof(tloc));
    tlctxt = target_location_ctxt_create_from_bsymbol(probe->target,
                              probe->thread->tid,
                              bsymbol);
    ltrc = target_lsymbol_resolve_location(target,tlctxt,bsymbol->lsymbol,0,
                           LOAD_FLAG_NONE,&tloc,NULL,
                           (!range) ? &range : NULL);
    if (ltrc == LOCTYPE_ADDR) 
        symbol_addr = LOCATION_ADDR(&tloc);
    target_location_ctxt_free(tlctxt);
    location_internal_free(&tloc);
    probe->bsymbol = bsymbol;
    RHOLD(bsymbol,probe);
    }

    /* If we don't have a range yet, get it. */
    if (!range) {
    target_find_memory_real(target,addr,NULL,NULL,&range);
    if (!range) {
        verror("could not find range for 0x%"PRIxADDR"\n",addr);
        goto errout;
    }
    }

    /* Create a probepoint if this is a new addr. */
    if ((probepoint = target_lookup_probepoint(target,probe->thread,addr))) {
    /* If the style matches for breakpoints, and if the style,
     * whence, and watchsize match for watchpoints, reuse it!
     */
    if (!((type == PROBEPOINT_BREAK
           && type == probepoint->type
           && ((probepoint->style == PROBEPOINT_HW
            && (style == PROBEPOINT_HW
            || style == PROBEPOINT_FASTEST))
           || (probepoint->style == PROBEPOINT_SW
               && (style == PROBEPOINT_SW
               || style == PROBEPOINT_FASTEST))))
          || (type == PROBEPOINT_WATCH
          && type == probepoint->type
          && style == probepoint->style
          && whence == probepoint->whence
          && watchsize == probepoint->watchsize))) {
        verror("addr 0x%"PRIxADDR" already has a probepoint with different properties!\n",addr);
        errno = EADDRINUSE;
        goto errout;
    }
    }
    else {
        if (type == PROBEPOINT_BREAK) {
        if (!(probepoint = probepoint_create_break(target,addr,range,style,
                               bsymbol,symbol_addr))) {
        verror("could not create breakpoint for 0x%"PRIxADDR"\n",addr);
        goto errout;
        }
    }
    else {
        if (whence == PROBEPOINT_WAUTO) 
        whence = PROBEPOINT_READWRITE;

        if (!(probepoint = probepoint_create_watch(target,addr,range,
                               style,whence,watchsize,
                               bsymbol,symbol_addr))) {
        verror("could not create watchpoint for 0x%"PRIxADDR"\n",addr);
        goto errout;
        }
    }

    created = 1;
    }

    /* Inject the probepoint. */
    if (__probepoint_insert(probepoint,probe->thread)) {
    verror("could not insert probepoint at 0x%"PRIxADDR"\n",addr);
    if (created) 
        probepoint_free(probepoint);
    goto errout;
    }

    list_add_tail(&probe->probe,&probepoint->probes);
    probe->probepoint = probepoint;

    if (PROBE_SAFE_OP(probe,registered)) {
    verror("probe '%s': registered failed, aborting\n",probe->name);
    if (created) 
        probepoint_free(probepoint);
    goto errout;
    }

    if (probe_enable(probe) && created) {
    probepoint_free(probepoint);
    goto errout;
    }

    vdebug(5,LA_PROBE,LF_PROBE,"probe %s attached to ",probe->name);
    LOGDUMPPROBEPOINT(5,LA_PROBE,LF_PROBE,probe->probepoint);
    vdebugc(5,LA_PROBE,LF_PROBE,"\n");

    return probe;

 errout:
    if (bsymbol) {
    bsymbol_release(bsymbol);
    probe->bsymbol = NULL;
    }
    if (probe->autofree)
    probe_free(probe,1);
    return NULL;
}

struct probe *probe_register_addr(struct probe *probe,ADDR addr,
                  probepoint_type_t type,
                  probepoint_style_t style,
                  probepoint_whence_t whence,
                  probepoint_watchsize_t watchsize,
                  struct bsymbol *bsymbol) {
    return __probe_register_addr(probe,addr,NULL,type,style,whence,watchsize,
                 bsymbol,0);
}

struct probe *probe_register_line(struct probe *probe,char *filename,int line,
                  probepoint_style_t style,
                  probepoint_whence_t whence,
                  probepoint_watchsize_t watchsize) {
    struct target *target = probe->target;
    struct memrange *range = NULL;
    ADDR start = 0;
    ADDR alt_start = 0;
    ADDR probeaddr;
    struct bsymbol *bsymbol = NULL;
    struct symbol *symbol;
    struct target_location_ctxt *tlctxt;

    bsymbol = target_lookup_sym_line(target,filename,line,NULL,&probeaddr);
    if (!bsymbol)
    return NULL;
    symbol = lsymbol_last_symbol(bsymbol->lsymbol);

    /* No need to RHOLD(); __probe_register_addr() does it. 
     * IN FACT, we need to release when we exit!
     */

    if (!SYMBOL_IS_FULL(symbol)) {
    verror("cannot probe a partial symbol!\n");
    goto errout;
    }

    if (SYMBOL_IS_FUNC(symbol) || SYMBOL_IS_LABEL(symbol) 
    || SYMBOL_IS_BLOCK(symbol)) {
    tlctxt = target_location_ctxt_create_from_bsymbol(probe->target,
                              probe->thread->tid,
                              bsymbol);
    if (target_lsymbol_resolve_bounds(target,tlctxt,bsymbol->lsymbol,0,
                      &start,NULL,NULL,&alt_start,NULL)) {
        vwarn("could not resolve base addr for symbol %s!\n",
          lsymbol_get_name(bsymbol->lsymbol));
    }
    target_location_ctxt_free(tlctxt);

    target_find_memory_real(target,probeaddr,NULL,NULL,&range);
    if (!range) {
        verror("could not find range for probeaddr 0x%"PRIxADDR"\n",
           probeaddr);
        goto errout;
    }

    probe = __probe_register_addr(probe,probeaddr,range,
                      PROBEPOINT_BREAK,style,whence,watchsize,
                      bsymbol,start);
    }
    else {
    verror("unknown symbol type '%s'!\n",
           SYMBOL_TYPE(bsymbol->lsymbol->symbol->type));
    goto errout;
    }

    bsymbol_release(bsymbol);
    return probe;

 errout:
    if (probe->autofree)
    probe_free(probe,1);
    if (bsymbol)
    bsymbol_release(bsymbol);
    return NULL;
}

struct probe *probe_register_symbol(struct probe *probe,struct bsymbol *bsymbol,
                    probepoint_style_t style,
                    probepoint_whence_t whence,
                    probepoint_watchsize_t watchsize) {
    struct target *target = probe->target;
    struct memrange *range = NULL;
    ADDR start = 0;
    ADDR alt_start = 0;
    ADDR probeaddr = 0;
    unsigned int ssize;
    struct symbol *symbol;
    loctype_t ltrc;
    struct location tloc;
    struct target_location_ctxt *tlctxt = NULL;
    int rc;

    symbol = lsymbol_last_symbol(bsymbol->lsymbol);

    if (!SYMBOL_IS_FULL(symbol)) {
    verror("cannot probe a partial symbol!\n");
    goto errout;
    }

    /* No need to RHOLD(); __probe_register_addr() does it. */

    if (target->ops->probe_register_symbol) {
    rc = target->ops->probe_register_symbol(target,probe->thread->tid,
                        probe,bsymbol,
                        style,whence,watchsize);
    if (rc) {
        verror("could not register probe for symbol '%s' breakpoint!\n",
           bsymbol_get_name(bsymbol));
        goto errout;
    }
    }
    else if (SYMBOL_IS_FUNC(symbol) || SYMBOL_IS_LABEL(symbol) 
    || SYMBOL_IS_BLOCK(symbol)) {
    tlctxt = target_location_ctxt_create_from_bsymbol(probe->target,
                              probe->thread->tid,
                              bsymbol);
    if (target_lsymbol_resolve_bounds(target,tlctxt,bsymbol->lsymbol,0,
                      &start,NULL,NULL,&alt_start,NULL)) {
        verror("could not resolve base addr for symbol %s!\n",
           lsymbol_get_name(bsymbol->lsymbol));
        goto errout;
    }
    else if (alt_start) 
        probeaddr = alt_start;
    else
        probeaddr = start;

    target_location_ctxt_free(tlctxt);
    tlctxt = NULL;

    if (!target_find_memory_real(target,probeaddr,NULL,NULL,&range)) {
        verror("could not find addr 0x%"PRIxADDR"!\n",probeaddr);
        goto errout;
    }

    probe = __probe_register_addr(probe,probeaddr,range,
                      PROBEPOINT_BREAK,style,whence,watchsize,
                      bsymbol,start);
    }
    else if (SYMBOL_IS_VAR(bsymbol->lsymbol->symbol)) {
    if (watchsize == PROBEPOINT_LAUTO) {
        ssize = symbol_type_full_bytesize(symbol_get_datatype(symbol));
        if (ssize <= 0) {
        verror("bad size (%d) for type of %s!\n",
               ssize,bsymbol->lsymbol->symbol->name);
        goto errout;
        }

        watchsize = probepoint_closest_watchsize(ssize);
    }

    memset(&tloc,0,sizeof(tloc));
    tlctxt = target_location_ctxt_create_from_bsymbol(probe->target,
                              probe->thread->tid,
                              bsymbol);
    ltrc = target_lsymbol_resolve_location(target,tlctxt,bsymbol->lsymbol,0,
                           LOAD_FLAG_NONE,&tloc,NULL,&range);
    if (ltrc == LOCTYPE_ADDR) {
        probeaddr = LOCATION_ADDR(&tloc);
        location_internal_free(&tloc);
    }
    else {
        verror("could not resolve base addr for var %s (loctype %s)!\n",
           bsymbol->lsymbol->symbol->name,LOCTYPE(ltrc));
        location_internal_free(&tloc);
        goto errout;
    }

    target_location_ctxt_free(tlctxt);
    tlctxt = NULL;

    if (!target_find_memory_real(target,probeaddr,NULL,NULL,&range)) {
        verror("could not find addr 0x%"PRIxADDR"!\n",probeaddr);
        goto errout;
    }

    probe = __probe_register_addr(probe,probeaddr,range,
                      PROBEPOINT_WATCH,style,whence,watchsize,
                      bsymbol,probeaddr);
    }
    else {
    verror("unknown symbol type '%s'!\n",
           SYMBOL_TYPE(bsymbol->lsymbol->symbol->type));
    goto errout;
    }

    vdebug(5,LA_PROBE,LF_PROBE,"registered probe on %s at 0x%"PRIxADDR"\n",
       bsymbol_get_name(bsymbol),probeaddr);

    return probe;

 errout:
    if (tlctxt)
    target_location_ctxt_free(tlctxt);
    if (probe->autofree)
    probe_free(probe,1);
    return NULL;
}

struct probe *probe_register_source(struct probe *sink,struct probe *src) {
    struct target *target = src->target;
    int held_src_bsymbol = 0;
    REFCNT trefcnt;
    target_status_t status;

    /* XXX: should we do this?  Steal the src's bsymbol if we don't have
     * one!
     */
    if (!sink->bsymbol && src->bsymbol) {
    sink->bsymbol = src->bsymbol;
    RHOLD(src->bsymbol,sink);
    held_src_bsymbol = 1;
    }

    /*
     * Don't do this for now; allow this so we can build overlay probe
     * hierarchies easily.
     */
    /*
    if (sink->target != src->target) {
    verror("sink %s/src %s targets different!\n",sink->name,src->name);
    goto errout;
    }
    */

    /* Target must be paused before we do anything. */
    status = target_status(target);
    if (target_status(target) != TSTATUS_PAUSED && status != TSTATUS_EXITING) {
        verror("target not paused!\n");
    errno = EINVAL;
    goto errout;
    }

    /* Add this sink to the src, and vice versa! */
    sink->sources = g_list_prepend(sink->sources,src);
    src->sinks = g_list_prepend(src->sinks,sink);

    if (PROBE_SAFE_OP(sink,registered)) {
    verror("probe '%s': registered failed, aborting\n",sink->name);
    goto errout;
    }

    /* Enable everybody downstream. */
    if (probe_enable(sink)) {
    verror("failed to enable sink probe '%s', aborting\n",sink->name);
    goto errout;
    }

    return sink;

 errout:
    if (held_src_bsymbol) {
    RPUT(sink->bsymbol,bsymbol,sink,trefcnt);
    sink->bsymbol = NULL;
    }
    if (sink->autofree)
    probe_free(sink,1);
    return NULL;
}

struct probe *probe_register_sources(struct probe *sink,struct probe *src,...) {
    va_list ap;
    struct probe *rc;
    struct probe *tsrc;

    va_start(ap,src);
    while ((tsrc = va_arg(ap,struct probe *))) {
    if (tsrc->target != sink->target) {
        verror("sink %s and src %s targets differ!\n",sink->name,src->name);
        return NULL;
    }
    }
    va_end(ap);

    if (!(rc = probe_register_source(sink,src)))
    return rc;

    va_start(ap,src);
    while ((tsrc = va_arg(ap,struct probe *))) {
    if (!(rc = probe_register_source(sink,tsrc)))
        return rc;
    /*
     * XXX: need to unwind registrations, too, in case of failure,
     * just like for probe batch registration!
     */
    }
    va_end(ap);

    return sink;
}

int probe_register_batch(struct target *target,tid_t tid,
             ADDR *addrlist,int listlen,
             probepoint_type_t type,probepoint_style_t style,
             probepoint_whence_t whence,
             probepoint_watchsize_t watchsize,
             probe_handler_t pre_handler,
             probe_handler_t post_handler,
             void *handler_data,
             struct probe **probelist,
             int failureaction) {
    int i;
    int retval = 0;
    struct probe *probe;
    char *buf;
    target_status_t status;

    if (!probelist)
    return -1;
    if (!listlen) 
    return 0;

    if (type == PROBEPOINT_WATCH && style == PROBEPOINT_SW) {
    verror("software watchpoints are unsupported!\n");
    errno = EINVAL;
    return -1;
    }

    /* Target must be paused before we do anything. */
    status = target_status(target);
    if (target_status(target) != TSTATUS_PAUSED && status != TSTATUS_EXITING) {
        verror("target not paused!\n");
    errno = EINVAL;
    return -1;
    }

    for (i = 0; i < listlen; ++i) {
    /* allow sparse lists */
    if (addrlist[i] == 0)
        continue;

    buf = malloc(5+1+16+1);
    sprintf(buf,"probe@%"PRIxADDR,addrlist[i]);
    probe = probe_create(target,tid,NULL,buf,pre_handler,post_handler,
                 handler_data,0,1);

    if (!(probelist[i] = probe_register_addr(probe,addrlist[i],
                         type,style,whence,watchsize,
                         NULL))) {
        if (failureaction == 2) {
        ++retval;
        continue;
        }
        else if (failureaction == 1) {
        ++retval;
        goto errunreg;
        }
        else {
        retval = 1;
        goto out;
        }
    }
    }
    goto out;

 errunreg:
    for (i = 0; i < listlen; ++i) {
    if (addrlist[i] == 0)
        continue;

    if (probelist[i] == NULL)
        continue;

    /* Don't force this unregister.  If there are dangling
     * probepoints, they'll have to get harvested later.  This
     * totally should not happen here though -- the batch
     * registration is like a transaction.
     */
    __probe_unregister(probelist[i],0,1);
    }

 out:
    return retval;
}

probepoint_watchsize_t probepoint_closest_watchsize(int size) {
    if (size <= 1)
    return PROBEPOINT_L0;
    else if (size <= 2)
    return PROBEPOINT_L2;
    else {
#if __WORDSIZE == 64
    if (size <= 4)
        return PROBEPOINT_L4;
    else 
        return PROBEPOINT_L8;
#else
    return PROBEPOINT_L4;
#endif
    }
}

void *probe_summarize(struct probe *probe) {
    if (!probe->ops || !probe->ops->summarize) 
    return NULL;

    return probe->ops->summarize(probe);
}

void *probe_summarize_tid(struct probe *probe,tid_t tid) {
    if (!probe->ops || !probe->ops->summarize_tid) 
    return NULL;

    return probe->ops->summarize_tid(probe,tid);
}

int probe_disable_one(struct probe *probe) {
    probe->enabled = 0;

    if (PROBE_SAFE_OP(probe,disabled)) {
    verror("probe '%s': disabled failed, ignoring\n",probe->name);
    return -1;
    }

    return 0;
}

int probe_disable(struct probe *probe) {
    struct probe *ptmp;
    GList *list;
    GList *list2;
    int anyenabled = 0;
    int retval = 0;

    if (probe_disable_one(probe))
    return -1;

    if (probe->sources) {
    list = probe->sources;
    while (list) {
        ptmp = (struct probe *)list->data;

        /* Disable recursively *if* the source doesn't have any
         * enabled sinks.
         */
        if (probe_enabled(ptmp)) {
        list2 = ptmp->sinks;
        while (list2) {
            if (((struct probe *)(list->data))->enabled) {
            anyenabled = 1;
            break;
            }
            list2 = g_list_next(list2);
        }
        if (!anyenabled)
            retval |= probe_disable(ptmp);
        anyenabled = 0;
        }
        list = g_list_next(list);
    }
    }

    return retval;
}

int probe_enable_one(struct probe *probe) {
    probe->enabled = 1;

    if (PROBE_SAFE_OP(probe,enabled)) {
    verror("probe '%s': enabled failed, disabling!\n",probe->name);
    probe->enabled = 0;
    return -1;
    }

    return 0;
}

int probe_enable(struct probe *probe) {
    struct probe *ptmp;
    GList *list;
    GList *list2;
    int anyenabled = 0;

    if (probe->sources) {
    list = probe->sources;
    while (list) {
        ptmp = (struct probe *)list->data;
        if (!probe_enabled(ptmp))
        probe_enable(ptmp);
        list = g_list_next(list);
    }
    }

    probe->enabled = 1;

    if (PROBE_SAFE_OP(probe,enabled)) {
    verror("probe '%s': enabled failed, disabling\n",probe->name);
    probe->enabled = 0;
    if (probe->sources) {
        list = probe->sources;
        while (list) {
        ptmp = (struct probe *)list->data;

        /* basically do probe_disable, but don't notify probe! */
        if (probe_enabled(ptmp)) {
            list2 = ptmp->sinks;
            while (list2) {
            if (((struct probe *)(list->data))->enabled) {
                anyenabled = 1;
                break;
            }
            list2 = g_list_next(list2);
            }
            if (!anyenabled)
            probe_disable(ptmp);
            anyenabled = 0;
        }
        list = g_list_next(list);
        }
    }
    return -1;
    }

    return 0;
}

/*
 * Indicates whether a probe is enabled or not.
 * Returns a non-zero value if the probe is active, a value of 0 if the 
 * probe is inactive, or a value of -1 if the given handle is invalid.
 */
int probe_enabled(struct probe *probe) {
    return probe->enabled;
}

int probe_is_base(struct probe *probe) {
    return probe->probepoint != NULL;
}

int probe_num_sources(struct probe *probe) {
    if (probe->sources)
    return g_list_length(probe->sources);
    return 0;
}

int probe_num_sinks(struct probe *probe) {
    if (probe->sinks)
    return g_list_length(probe->sinks);
    return 0;
}

char *probe_name(struct probe *probe) {
    return probe->name;
}

struct bsymbol *probe_symbol(struct probe *probe) {
    return probe->bsymbol;
}

struct target*probe_target(struct probe *probe) {
    return probe->target;
}

tid_t probe_tid(struct probe *probe) {
    return probe->thread->tid;
}

void *probe_priv(struct probe *probe) {
    return probe->priv;
}

/*
 * Returns the address the a probe is targeting, or 0 if the probe is a
 * sink without a probepoint.
 */
ADDR probe_addr(struct probe *probe) {
    if (probe->probepoint)
    return probe->probepoint->addr;
    return 0;
}

/*
 * Returns the type of the probe.
 */
probepoint_type_t probe_type(struct probe *probe) {
    return probe->probepoint->type;
}

/*
 * Returns the style of the probe.
 */
probepoint_style_t probe_style(struct probe *probe) {
    return probe->probepoint->style;
}

/*
 * Returns the whence of the probe.
 */
probepoint_whence_t probe_whence(struct probe *probe) {
    return probe->probepoint->whence;
}


static int run_post_handlers(struct target *target,
                 struct target_thread *tthread,
                 struct probepoint *probepoint);
static int setup_post_single_step(struct target *target,
                  struct target_thread *tthread,
                  struct probepoint *probepoint);
static int handle_simple_actions(struct target *target,
                 struct target_thread *tthread,
                 struct probepoint *probepoint);
static int handle_complex_actions(struct target *target,
                  struct target_thread *tthread,
                  struct probepoint *probepoint);

/*
 * Runs and cleans up any simple actions that should happen at this
 * probepoint.  We run all simple actions after the probe prehandlers
 * have been run, but before the singlestep of the probepoint happens.
 */
static int handle_simple_actions(struct target *target,
                 struct target_thread *tthread,
                 struct probepoint *probepoint) {
    struct action *action;
    struct action *taction;
    int retval = 0;
    int rc;
    unsigned long rcb;

    list_for_each_entry_safe(action,taction,&probepoint->simple_actions,action) {
    rc = 0;

    if (!probe_enabled(action->probe)) {
        vdebug(3,LA_PROBE,LF_ACTION,"skipping disabled probe at ");
        LOGDUMPPROBEPOINT(3,LA_PROBE,LF_ACTION,probepoint);
        vdebugc(3,LA_PROBE,LF_ACTION,"\n");
        continue;
    }

    if (action->type == ACTION_REGMOD) {
        rc = target_write_reg(tthread->target,tthread->tid,
                  action->detail.regmod.regnum,
                  action->detail.regmod.regval);
        if (rc)
        vwarn("could not write reg %"PRIiREG"!\n",
              action->detail.regmod.regnum);
        else 
        vdebug(4,LA_PROBE,LF_ACTION,"wrote 0x%"PRIxREGVAL" to %"PRIiREG"\n",
               action->detail.regmod.regval,action->detail.regmod.regnum);
    }
    else if (action->type == ACTION_MEMMOD) {
        rcb = target_write_addr(tthread->target,
                    action->detail.memmod.destaddr,
                    action->detail.memmod.len,
                    (unsigned char *)action->detail.memmod.data);
        if (rcb != action->detail.memmod.len) {
        vwarn("could not write %d bytes to 0x%"PRIxADDR"!\n",
              action->detail.memmod.len,action->detail.memmod.destaddr);
        rc = 1;
        }
        else
        vdebug(4,LA_PROBE,LF_ACTION,"wrote %d bytes to 0x%"PRIxADDR"\n",
               action->detail.memmod.len,action->detail.memmod.destaddr);
    }
    else {
        verror("BUG: unsupported action type %d -- not doing it!\n",
           action->type);
        rc = 1;
    }

    if (rc) {
        ++retval;
        if (action->handler)
        action->handler(action,tthread,action->probe,probepoint,
                MSG_FAILURE,0,action->handler_data);
    }
    else if (action->handler) 
        action->handler(action,tthread,action->probe,probepoint,
                MSG_SUCCESS,0,action->handler_data);


    /* cleanup oneshot actions! */
    action_finish_handling(action,NULL);
    }

    return retval;
}
/*
 * Returns: <0 on error; 0 if not stepping; 1 if stepping.
 */
static int setup_single_step_actions(struct target *target,
                     struct target_thread *tthread,
                     struct probepoint *probepoint,
                     int isbp,int stepping) {
    tid_t tid = tthread->tid;
    struct action *action, *taction;

    /*
     * If we need to do any single step actions, set that up if
     * handle_complex_actions didn't already.  This should be pretty
     * rare, but if some injected code doesn't need single stepping
     * because it "notifies" when it's done via breakpoint, we can
     * save a lot of debug interrupts.
     */
    if (list_empty(&probepoint->ss_actions)) 
    return 0;

    /*
     * If the action was not boosted (i.e. is running at the
     * probepoint), and we're not already single stepping, we need
     * to tell the single step routine that we're stepping at a
     * breakpoint location.
     */
    if (!stepping) {
    vdebug(4,LA_PROBE,LF_PROBEPOINT,"setting up single step actions for ");
    LOGDUMPPROBEPOINT(4,LA_PROBE,LF_PROBEPOINT,probepoint);
    vdebugc(4,LA_PROBE,LF_PROBEPOINT,"\n");

    if (probepoint->style == PROBEPOINT_HW
        && isbp
        && !target->nodisablehwbponss) {
        /*
         * We need to disable the hw breakpoint before we single
         * step because the target can't do it.
         */
        target_disable_hw_breakpoint(target,probepoint->thread->tid,probepoint->debugregnum);
        probepoint->debugregdisabled = 1;
    }

    if (target_singlestep(target,tid,isbp) < 0) {
        verror("could not keep single stepping target!\n");

        if (probepoint->style == PROBEPOINT_HW
        && isbp
        && !target->nodisablehwbponss) {
        /*
         * Reenable the hw breakpoint we just disabled.
         */
        target_enable_hw_breakpoint(target,probepoint->thread->tid,probepoint->debugregnum);
        probepoint->debugregdisabled = 0;
        }

        if (target_singlestep_end(target,tid))
        verror("could not stop single stepping target"
               " after failed sstep!\n");

        /*
         * All we can really do is notify all the single step
         * actions that we had an error, and nuke them, and keep
         * going.
         */
        list_for_each_entry_safe(action,taction,&probepoint->ss_actions,
                     action) {
        if (action->handler) 
            action->handler(action,tthread,action->probe,probepoint,
                    MSG_FAILURE,0,action->handler_data);

        action_finish_handling(action,NULL);
        }

        stepping = -1;
    }
    else {
        vdebug(4,LA_PROBE,LF_PROBEPOINT,"sstep command succeeded for ");
        LOGDUMPPROBEPOINT(4,LA_PROBE,LF_PROBEPOINT,probepoint);
        vdebugc(4,LA_PROBE,LF_PROBEPOINT,"\n");

        stepping = 1;
    }
    }
    else {
    vdebug(4,LA_PROBE,LF_PROBEPOINT,
           "already stepping; building tacs for single step actions for ");
    LOGDUMPPROBEPOINT(4,LA_PROBE,LF_PROBEPOINT,probepoint);
    vdebugc(4,LA_PROBE,LF_PROBEPOINT,"\n");
    }

    /* 
     * If single step init succeeded, let the ss handler take over.
     * Also, take a reference to all the ss_actions actions and
     * place contexts for them on our thread's list.
     */
    if (stepping == 1) {
    list_for_each_entry_safe(action,taction,&probepoint->ss_actions,action) {
        struct thread_action_context *tac = \
        (struct thread_action_context *)calloc(1,sizeof(*tac));
        tac->action = action;
        RHOLD(action,tac);
        tac->stepped = 0;
        INIT_LIST_HEAD(&tac->tac);

        list_add_tail(&tac->tac,&tthread->ss_actions);
    }
    }

    return stepping;
}

static int run_post_handlers(struct target *target,
                 struct target_thread *tthread,
                 struct probepoint *probepoint) {
    int rc;
    int noreinject = 0;
    struct probe *probe;
    int i = 0;

    /*
     * Run post-handlers
     */
    list_for_each_entry(probe,&probepoint->probes,probe) {
    ++i;
    PROBE_SAFE_OP_ARGS(probe,values_notify_phase,tthread->tid,
               PHASE_POST_START);
    if (probe->enabled) {
        if (probe->post_handler) {
        vdebug(4,LA_PROBE,LF_PROBEPOINT,"running post handler at ");
        LOGDUMPPROBEPOINT(4,LA_PROBE,LF_PROBEPOINT,probepoint);
        vdebugc(4,LA_PROBE,LF_PROBEPOINT,"\n");

        rc = probe->post_handler(probe,tthread->tid,probe->handler_data,probe,probe);
        if (rc == RESULT_ERROR) 
            probe_disable(probe);
        else if (rc == RESULT_ABORT) 
            /* don't reinject the probe! */
            noreinject = 1;
        }
        else if (0 && probe->sinks) {
        vdebug(4,LA_PROBE,LF_PROBEPOINT,
               "running default probe sink post_handler at ");
        LOGDUMPPROBEPOINT(4,LA_PROBE,LF_PROBEPOINT,probepoint);
        vdebugc(4,LA_PROBE,LF_PROBEPOINT,"\n");

        probe_do_sink_post_handlers(probe,tthread->tid,NULL,probe,probe);
        }
    }

    PROBE_SAFE_OP_ARGS(probe,values_notify_phase,tthread->tid,PHASE_POST_END);
    }

    if (i > 1 && noreinject) {
    vwarn("cannot skip reinjection of breakpoint because multiple probes present!\n");
    noreinject = 0;
    }

    return noreinject;
}

void probepoint_release(struct target *target,struct target_thread *tthread,
            struct probepoint *probepoint) {
    /* Only release if we owned it! */
    if (probepoint->tpc == tthread->tpc)
    probepoint->tpc = NULL;
}

struct thread_probepoint_context *probepoint_hold(struct target *target,
                          struct target_thread *tthread,
                          struct probepoint *probepoint,
                          struct thread_probepoint_context *tpc) {
    if (probepoint->style == PROBEPOINT_SW
    && probepoint->tpc != NULL
    && probepoint->tpc->thread != tthread)
    return probepoint->tpc;

    probepoint->tpc = tpc;
    return tpc;
}

int probepoint_pause_handling(struct target *target,
                  struct target_thread *tthread,
                  struct probepoint *probepoint,
                  thread_resumeat_t resumeat) {
    if (target->threadctl) {
    vdebug(5,LA_PROBE,LF_PROBEPOINT,
           "pausing thread %"PRIiTID" (%d) until thread %"PRIiTID" finishes"
           " handling ",tthread->tid,resumeat,probepoint->tpc->thread->tid);
    LOGDUMPPROBEPOINT_NL(3,LA_PROBE,LF_PROBEPOINT,probepoint);

    tthread->resumeat = resumeat;
    return 0;
    }

    return -1;
}

static struct thread_probepoint_context *tpc_new(struct target_thread *tthread,
                         struct probepoint *probepoint) {
    struct thread_probepoint_context *tpc = (struct thread_probepoint_context *) \
    calloc(1,sizeof(*tpc));
    tpc->thread = tthread;
    tpc->probepoint = probepoint;

    return tpc;
}

void tpc_free(struct thread_probepoint_context *tpc) {
    free(tpc);
}

/*
 * We will not run a single step of the real instruction in two cases.
 * First, if any complex action obviated the real instruction, we skip
 * the real instruction, and do nothing to EIP.  We just run
 * post-handlers, if there are any.
 * Second, if there are no post-handlers
 *
 * Return <0 on error; 0 if we skipped a sstep because the action
 * obviated it; 1 if we setup a single step; 2 if we "paused" the thread
 * because we couldn't hold the probepoint to do the single step.
 */
static int setup_post_single_step(struct target *target,
                  struct target_thread *tthread,
                  struct probepoint *probepoint) {
    int doit = 0;
    struct probe *probe;
    tid_t tid = tthread->tid;
    struct thread_probepoint_context *tpc = tthread->tpc;
    int noreinject;
    struct thread_probepoint_context *htpc;

    /*
     * We're now handling post stuff at the breakpoint.
     *
     * But, note that we don't change state to POSTHANDLING until we
     * know we're going to single step the real instruction.  If we
     * don't do that, we don't change -- and we only adjust the state of
     * the probepoint if we own the probepoint.  Otherwise we have to
     * pause this thread until we do own it.
     */

    if (tpc->action_obviated_orig) {
    vdebug(4,LA_PROBE,LF_PROBEPOINT,"skipping sstep due to action obviation of ");
    LOGDUMPPROBEPOINT_NL(4,LA_PROBE,LF_PROBEPOINT,probepoint);

    /* Just run the posthandlers; don't single step the orig. */
    noreinject = run_post_handlers(target,tthread,probepoint);

    if (!noreinject) {
        /*
         * If the action was boosted, we have nothing to replace.
         * If it wasn't, when we removed it, we put the BP back in.
         * So don't do anything here, because if the action was
         * boosted, some other thread might hold the probepoint!
         *
         * But, if we had disabled a hw breakpoint, reenable it!
         */
        if (probepoint->style == PROBEPOINT_HW 
        && probepoint->debugregdisabled) {
        /*
         * Enable hardware bp here!
         */
        target_enable_hw_breakpoint(target,probepoint->thread->tid,probepoint->debugregnum);
        probepoint->debugregdisabled = 0;

        probepoint->state = PROBE_BP_SET;
        }
        else if (probepoint->style == PROBEPOINT_SW) {
        target_enable_sw_breakpoint(target,probepoint->thread->tid,
                        probepoint->mmod);

        probepoint->state = PROBE_BP_SET;
        }
    }
    else {
        __probepoint_remove(probepoint,0,0);
    }

    /*
     * Only release our hold on the probepoint if we actually held
     * it; if we had been running a boosted action, we might not
     * hold the probepoint.
     */
    probepoint_release(target,tthread,probepoint);

    return 0;
    }

    /*
     * Now that we've handled the case where an action might have
     * replaced the real instruction, we have to figure out if we should
     * single step the original instruction or not.
     *
     * If we're hardware and there are no enabled probes with
     * post-handlers, single step; otherwise, just proceed.  If we're
     * software, *always* single step after replacing the original
     * instruction.
     */
    if (probepoint->style == PROBEPOINT_HW) {
    list_for_each_entry(probe,&probepoint->probes,probe) {
        if (probe->enabled && (probe->post_handler || probe->sinks)) {
        doit = 1;
        break;
        }
    }

    /*
     * XXX: for now, always force single step even for HW
     * breakpoints, since the Xen VM backend will get stuck in
     * an infinite loop at the breakpoint location.
     *
     * For whatever reason, this does not happen for the Linux
     * userspace process target.  Until we know why, just always
     * single step here.
     */
    doit = 1;

    if (!doit) {
        probepoint->state = PROBE_BP_SET;

        vdebug(4,LA_PROBE,LF_PROBEPOINT,"skipping sstep for HW ");
        LOGDUMPPROBEPOINT(4,LA_PROBE,LF_PROBEPOINT,probepoint);
        vdebugc(4,LA_PROBE,LF_PROBEPOINT,"; no post handlers\n");

        /*
         * Don't run posthandlers because we haven't done the
         * breakpointed instruction!  Well, this is not quite true
         * for watchpoints, but...
         */
    }
    else {
        /* We already own the probepoint because it's hardware. */
        probepoint->state = PROBE_BP_POSTHANDLING;
    }
    }
    /*
     * If we're software, replace the original.
     */
    else if (probepoint->style == PROBEPOINT_SW) {
    if (!target->no_adjust_bp_ip) {
        /* Restore the original instruction. */
        vdebug(4,LA_PROBE,LF_PROBEPOINT,"restoring orig instr for SW ");
        LOGDUMPPROBEPOINT(4,LA_PROBE,LF_PROBEPOINT,probepoint);
        vdebugc(4,LA_PROBE,LF_PROBEPOINT,"\n");
    }

    doit = 1;

    /*
     * Grab hold of the probepoint, since we might have run boosted
     * instructions in the past.  If we can't grab the probepoint,
     * we have to pause this thread until we can grab it.
     */
    if ((htpc = probepoint_hold(target,tthread,probepoint,tpc)) != tpc) {
        if (probepoint_pause_handling(target,tthread,probepoint,
                      THREAD_RESUMEAT_SSR)) {
        verror("thread %"PRIiTID" hit ss when thread %"PRIiTID" already"
               " handling it; target failed to ctl thread!\n",
               tthread->tid,htpc->thread->tid);
        /*
         * There literally is nothing we can do -- we cannot
         * handle this breakpoint interrupt.
         */
        return -1;
        }
        else 
        return 2;
    }
    else {
        /*
         * If we're in BPMODE_STRICT, we have to pause all the other
         * threads.
         */
        if (target->spec->bpmode == THREAD_BPMODE_STRICT) {
        if (target_pause(target)) {
            vwarn("could not pause the target for blocking thread"
              " %"PRIiTID"!\n",tthread->tid);
            return -1;
        }
        target->blocking_thread = tthread;
        }

        if (target_disable_sw_breakpoint(target,probepoint->thread->tid,
                         probepoint->mmod)) {
        verror("could not disable breakpoint before singlestep;"
               " assuming breakpoint is left in place and"
               " skipping single step, but badness will ensue!");

        if (target->blocking_thread == tthread)
            target->blocking_thread = NULL;
        probepoint->state = PROBE_BP_SET;
        probepoint_release(target,tthread,probepoint);
        tpc_free(tthread->tpc);
        tthread->tpc = (struct thread_probepoint_context *) \
            array_list_remove(tthread->tpc_stack);

        return -1;
        }
        else {
        /* We already own it. */
        probepoint->state = PROBE_BP_POSTHANDLING;
        }
    }
    }

    if (!doit) {
    /*
     * Only release our hold on the probepoint if we actually held
     * it; if we had been running a boosted action, we might not
     * hold the probepoint.
     */
    if (probepoint->tpc == tthread->tpc) {
        probepoint->state = PROBE_BP_SET;
        probepoint_release(target,tthread,probepoint);
    }

    return 0;
    }

    /* 
     * Command the single step to happen.  We hold the probepoint now,
     * so we can do anything.
     */
    vdebug(4,LA_PROBE,LF_PROBEPOINT,"doing sstep for ");
    LOGDUMPPROBEPOINT(4,LA_PROBE,LF_PROBEPOINT,probepoint);
    vdebugc(4,LA_PROBE,LF_PROBEPOINT,"\n");

    if (probepoint->style == PROBEPOINT_HW && !target->nodisablehwbponss) {
    /*
     * We need to disable the hw breakpoint before we single
     * step because the target can't do it.
     */
    target_disable_hw_breakpoint(target,probepoint->thread->tid,probepoint->debugregnum);
    probepoint->debugregdisabled = 1;
    }

    if (target_singlestep(target,tid,1) < 0) {
    verror("could not single step target after BP!\n");

    if (target_singlestep_end(target,tid))
        verror("could not stop single stepping target"
           " after failed sstep for breakpoint!\n");

    if (probepoint->style == PROBEPOINT_HW && !target->nodisablehwbponss) {
        /*
         * Reenable the hw breakpoint we just disabled.
         */
        target_enable_hw_breakpoint(target,probepoint->thread->tid,probepoint->debugregnum);
        probepoint->debugregdisabled = 0;
    }

    if (probepoint->style != PROBEPOINT_HW) {
        if (target_enable_sw_breakpoint(target,probepoint->thread->tid,
                        probepoint->mmod)) {
        verror("could not enable sw breakpoint after failed singlestep;"
               " assuming breakpoint is left in place and"
               " skipping single step, but badness will ensue!");
        }
    }

    /*
     * If we were supposed to single step, and it failed,
     * the best we can do is act like the BP is still set.
     */
    if (target->blocking_thread == tthread)
        target->blocking_thread = NULL;
    probepoint->state = PROBE_BP_SET;
    probepoint_release(target,tthread,probepoint);
    tpc_free(tthread->tpc);
    tthread->tpc = (struct thread_probepoint_context *) \
        array_list_remove(tthread->tpc_stack);

    return -1;
    }
    else {
    /* 
     * If single step init succeeded, let the ss handler take
     * over.
     *
     * Don't call target_resume after a successful target_singlestep.
     */
    vdebug(4,LA_PROBE,LF_PROBEPOINT,"sstep command succeeded for ");
    LOGDUMPPROBEPOINT(4,LA_PROBE,LF_PROBEPOINT,probepoint);
    vdebugc(4,LA_PROBE,LF_PROBEPOINT,"\n");

    if (probepoint->can_switch_context) {
        vdebug(4,LA_PROBE,LF_PROBEPOINT,"can_switch_context (%d) -- ",
           probepoint->can_switch_context);
        LOGDUMPPROBEPOINT(4,LA_PROBE,LF_PROBEPOINT,probepoint);
        vdebugc(4,LA_PROBE,LF_PROBEPOINT,"\n");
    }

    return 1;
    }
}

/*
 * In many ways, the goal of this function is to figure out if we need
 * to do a single step after the breakpoint.  There's lots of cases.
 *   * If BP is SW:
 *      - if any actions obviate (replace) the original instruction, do
 *        not single step, just reset the state to BP_SET (AND re-insert
 *        the BP right away) -- unless the
 *        action requires one or more single steps; if so, do them.
 *      - otherwise, replace the original instruction and set state to
 *        BP_HANDLING and single step
 *      - 
 *   * If BP is HW:
 *      - if any actions obviate (replace) the original instruction, do
 *        not single step, just reset the state to BP_SET -- unless the
 *        action requires one or more single steps; if so, do them.
 *      - otherwise, if no enabled probes have post handlers, do not
 *        single step, just reset the state to BP_SET.
 *      - otherwise, set state to BP_HANDLING and single step.
 *
 * NOTE: if we try to single step, we always disable hardware
 * breakpoints first.  If the single step init fails, we re-enable
 * them.  HW breakpoints are re-enabled in the ss handler below once
 * we're sure we don't need to do any more single steps.
 */
result_t probepoint_bp_handler(struct target *target,
                   struct target_thread *tthread,
                   struct probepoint *probepoint,
                   int was_stepping) {
    struct probe *probe;
    REGVAL ipval;
    int doit = 0;
    int rc;
    tid_t tid = tthread->tid;
    struct thread_probepoint_context *tpc, *htpc;
    int stepping = 0;
    struct action *action;
    struct thread_action_context *tac,*ttac;
    int already_ran_prehandlers_for_interrupted = 0;

    vdebug(5,LA_PROBE,LF_PROBEPOINT,"handling bp at ");
    LOGDUMPPROBEPOINT(5,LA_PROBE,LF_PROBEPOINT,probepoint);
    vdebugc(5,LA_PROBE,LF_PROBEPOINT,"\n");

    /*
     * If the thread is already handling this probepoint, the cause is
     * almost certainly that some action we ran recursed, running some
     * code that triggered the breakpoint again.
     *
     * We keep trying to handle it if we can below...
     */
    if (tthread->tpc && tthread->tpc->probepoint == probepoint)
    vwarn("existing thread probepoint same as bp probepoint;"
          " BUG or recursion due to action?\n");

    /*
     * See docs for target_thread::interrupted_ss_probepoint, and for
     * probepoint_interrupted_ss_handler.
     */
    if (tthread->interrupted_ss_probepoint == probepoint) {
    tthread->interrupted_ss_probepoint = NULL;
    already_ran_prehandlers_for_interrupted = 1;
    }

    /*
     * If we were single stepping when we hit the breakpoint, and we hit
     * a hardware breakpoint, we need to fire the single step action
     * handlers off.  If it's a software breakpoint, the trap after the
     * last instruction was allowed to happen before the breakpoint was
     * executed.  But with hardware breakpoints, the single step trap
     * for the instruction preceding the breakpoint, and the breakpoint,
     * seem to happen in the same interrupt.
     */
    if (probepoint->style == PROBEPOINT_HW 
    && was_stepping 
    && !list_empty(&tthread->ss_actions)) {
    list_for_each_entry_safe(tac,ttac,&tthread->ss_actions,tac) {
        action = tac->action;
        ++tac->stepped;

        if (action->steps == -2 
        || (action->steps > 0 && tac->stepped >= action->steps)) {
        if (action->handler)
            action->handler(action,tthread,action->probe,action->probe->probepoint,
                    MSG_SUCCESS,tac->stepped,action->handler_data);

        action_finish_handling(action,tac);

        list_del(&tac->tac);
        free(tac);
        }
        else {
        if (action->handler) 
            action->handler(action,tthread,action->probe,action->probe->probepoint,
                    MSG_STEPPING_AT_BP,tac->stepped,
                    action->handler_data);
        }
    }

    if (list_empty(&tthread->ss_actions)) 
        was_stepping = 0;
    }

    /*
     * Push a new context for handling this probepoint.
     */
    tpc = tpc_new(tthread,probepoint);
    if (tthread->tpc) {
    array_list_append(tthread->tpc_stack,tthread->tpc);

    vdebug(3,LA_PROBE,LF_PROBEPOINT,
           "already handling %d probepoints in thread %d; most recent"
           " (tpc %p) was ",
           array_list_len(tthread->tpc_stack),tthread->tid,tthread->tpc);
    LOGDUMPPROBEPOINT_NL(3,LA_PROBE,LF_PROBEPOINT,tthread->tpc->probepoint);
    }
    tthread->tpc = tpc;

    /*
     * Check: do we need to hold the probepoint?  That depends on:
     *  - is the probepoint software?  hardware probepoints can always
     *    be held, although which tpc the thread is handling may change
     *    (i.e. if we are recursing trhough the same breakpoint again)
     *  - do we have unboosted complex actions?
     *  - do we have need to run the original instruction at the
     *    probepoint?
     * But we can't even answer the second one until we know that the
     * pre-handlers haven't added any actions (which they must be able
     * to do), so we have no choice -- we must hold the breakpoint
     * before handling it at all.  We may be able to release it sooner
     * than we think at the moment, but we can't know.  The only time we
     * can just automatically hold the probepoint is if 
     */
    if ((htpc = probepoint_hold(target,tthread,probepoint,tpc)) != tpc) {
    /*
     * If the BP is in some unset state, it might be being handled
     * for another thread.  If not, we have a bug, because the state
     * is wrong, but we obviously hit the BP so it *is* set and we
     * just "handle" it.
     *
     * If it *is* being handled by another thread -- this could only
     * have happened if this thread hit the BP at about the same
     * time another thread did, but if we have scheduled the single
     * step for the other thread and executed it -- and then the
     * next time the target checked for debug interrupts, it checked
     * this thread first instead of the single-stepping thread.
     *
     * In this case, if we have thread control, we pause this thread
     * until we can handle the breakpoint (i.e., until nothing else
     * is).  Of course, if we have thread control, we assume the
     * thread is already paused (it's at a debug interrupt, after
     * all); we just have to be careful not to unpause it until we
     * have handled its interrupt.
     *
     * If we don't have thread control, there's really nothing we
     * can do.  Sometimes loose mode sucks :).
     */
    if (probepoint->state != PROBE_BP_SET) {
        if (!probepoint->tpc) {
        verror("probepoint state is not BP_SET; BUG!\n");

        probepoint->state = PROBE_BP_SET;
        }
        else if (probepoint_pause_handling(target,tthread,probepoint,
                           THREAD_RESUMEAT_BPH)) {
        verror("thread %"PRIiTID" hit bp when thread %"PRIiTID" already"
               " handling it; target could not pause thread!\n",
               tthread->tid,probepoint->tpc->thread->tid);
        /*
         * There literally is nothing we can do -- we cannot
         * handle this breakpoint interrupt.
         */
        return RESULT_ERROR;
        }
        else 
        return RESULT_SUCCESS;
    }
    }

    /*
     * We own this probepoint now.  BUT, we might still have to pause
     * other threads in the target if we have to adjust the probepoint.
     */

    /* We move into the HANDLING state while we run the pre-handlers. */
    probepoint->state = PROBE_BP_PREHANDLING;

    /*
     * Prepare for handling: save the original ip value in case
     * something bad happens during the pre-handlers.
     */
    errno = 0;
    ipval = target_read_reg(target,tid,target->ipregno);
    if (probepoint->style == PROBEPOINT_SW && errno) {
    verror("could not read EIP to reset it for SW probepoint; skipping!");
    probepoint->state = PROBE_BP_SET;
    probepoint_release(target,tthread,probepoint);
    tpc_free(tthread->tpc);
    tthread->tpc = (struct thread_probepoint_context *) \
        array_list_remove(tthread->tpc_stack);
    return RESULT_ERROR;
    }

    vdebug(5,LA_PROBE,LF_PROBEPOINT,"EIP is 0x%"PRIxREGVAL" at ",ipval);
    LOGDUMPPROBEPOINT(5,LA_PROBE,LF_PROBEPOINT,probepoint);
    vdebugc(5,LA_PROBE,LF_PROBEPOINT,"\n");


    /* If SW bp, reset EIP and write it back *now*, because it's easy
     * here, and then if the user tries to read it, it's "correct".
     */
    if (!target->no_adjust_bp_ip && probepoint->style == PROBEPOINT_SW) {
    ipval -= target->arch->breakpoint_instrs_len;
    errno = 0;
    target_write_reg(target,tid,target->ipregno,ipval);
    if (errno) {
        verror("could not reset EIP before pre handlers; skipping!\n");
        probepoint->state = PROBE_BP_SET;
        probepoint_release(target,tthread,probepoint);
        tpc_free(tthread->tpc);
        tthread->tpc = (struct thread_probepoint_context *) \
        array_list_remove(tthread->tpc_stack);
        return RESULT_ERROR;
    }

    vdebug(4,LA_PROBE,LF_PROBEPOINT,"reset EIP to 0x%"PRIxREGVAL" for SW ",ipval);
    LOGDUMPPROBEPOINT(4,LA_PROBE,LF_PROBEPOINT,probepoint);
    vdebugc(4,LA_PROBE,LF_PROBEPOINT,"\n");
    }

    /*
     * Run pre-handlers if we have encountered our breakpoint for the
     * first time on this pass (which means we should not have an action
     * set!)
     */
    if (!already_ran_prehandlers_for_interrupted) {
    list_for_each_entry(probe,&probepoint->probes,probe) {
        PROBE_SAFE_OP_ARGS(probe,values_notify_phase,tthread->tid,
                   PHASE_PRE_START);

        if (probe->enabled) {
        if (probe->pre_handler) {
            vdebug(4,LA_PROBE,LF_PROBEPOINT,"running pre handler at ");
            LOGDUMPPROBEPOINT(4,LA_PROBE,LF_PROBEPOINT,probepoint);
            vdebugc(4,LA_PROBE,LF_PROBEPOINT,"\n");

            rc = probe->pre_handler(probe,tid,probe->handler_data,probe,probe);
            if (rc == RESULT_ERROR) 
            probe_disable(probe);
        }
        else if (0 && probe->sinks) {
            vdebug(4,LA_PROBE,LF_PROBEPOINT,
               "running default probe sink pre_handler at ");
            LOGDUMPPROBEPOINT(4,LA_PROBE,LF_PROBEPOINT,probepoint);
            vdebugc(4,LA_PROBE,LF_PROBEPOINT,"\n");
            probe_do_sink_pre_handlers(probe,tid,NULL,probe,probe);
        }
        doit = 1;
        }

        PROBE_SAFE_OP_ARGS(probe,values_notify_phase,tthread->tid,
                   PHASE_PRE_END);
    }
    }
    else {
    vdebug(4,LA_PROBE,LF_PROBEPOINT,
           "already ran pre handlers in interrupted thread %"PRIiTID" at ",
           tid);
    LOGDUMPPROBEPOINT(4,LA_PROBE,LF_PROBEPOINT,probepoint);
    vdebugc(4,LA_PROBE,LF_PROBEPOINT,"\n");
    }

    /* Restore ip register if we ran a handler. */
    if (!target->no_adjust_bp_ip && doit) {
    errno = 0;
    target_write_reg(target,tid,target->ipregno,ipval);
    if (errno) {
        verror("could not reset EIP after pre handlers!\n");
        probepoint->state = PROBE_BP_SET;
        probepoint_release(target,tthread,probepoint);
        tpc_free(tthread->tpc);
        tthread->tpc = (struct thread_probepoint_context *) \
        array_list_remove(tthread->tpc_stack);
        return RESULT_ERROR;
    }
        
    vdebug(9,LA_PROBE,LF_PROBEPOINT,
           "ip 0x%"PRIxREGVAL" restored after pre handlers at ",ipval);
    LOGDUMPPROBEPOINT(9,LA_PROBE,LF_PROBEPOINT,probepoint);
    vdebugc(9,LA_PROBE,LF_PROBEPOINT,"\n");
    }

    /* Now we're handling actions. */
    probepoint->state = PROBE_BP_ACTIONHANDLING;

    /*
     * Run the simple actions now.
     */
    if ((rc = handle_simple_actions(target,tthread,probepoint))) 
    vwarn("failed to handle %d simple actions!\n",rc);

    /*
     * Set up complex actions.  The output of the setup is what code we
     * need to place at the breakpoint site; the min single steps before
     * we can replace that code with 1) the original code, if the tmp
     * code does not replace the orig; or 2) the breakpoint again, if
     * the tmp code *does* replace the orig.  Or, it could be nothing.
     *
     * (If the complex action requires more than one single step, we
     * cannot support it unless the target is capable of pausing all
     * other threads (i.e., ensuring that the current thread cannot be
     * preempted).  We need this because we can basically assume that
     * the first single step will not be "interrupted" after a
     * breakpoint unless an interrupt happened to fire at the same time
     * as the breakpoint.  But, we can't assume that N single steps
     * won't be interrupted; if they are, the probepoint is storing
     * per-thread context, and it could get messed up bad.  Plus, the
     * probepoint might have arbitrary code at its location, instead of
     * the breakpoint or original instruction.)
     *
     * If the output is nothing (i.e., no complex actions), we decide if
     * we need to single step (always do for SW; if HW, and no probes
     * are enabled, or none of the enalbed probes have posthandlers, we
     * can skip the SW breakpoint; OR ALSO do if we have one or more
     * single step actions).
     *
     * Then in the ss handler, we have to check what state we're in.
     * First, if we are called with no probepoint, we must be sstep'ing
     * for an sstep action(s).  Otherwise, if probepoint->action is set,
     * we must be sstep'ing a complex action (or on behalf of it).
     * Otherwise, we must just be sstep'ing the original instr under the
     * breakpoint.
     *
     * In the first case, just hanlde the ss_actions list.
     *
     * In the second case, continue sstep'ing if the action requires it;
     * otherwise, either setup another complex action, or replace the
     * underlying code if the action didn't obviate it -- and single
     * step the orig code.  Then put the breakpoint back in.
     *
     * In the third case, just put the breakpoint back in.
     *
     * In all cases, leave single step enabled if there are still
     * ss_actions running for the thread.
     */
    if ((stepping = handle_complex_actions(target,tthread,probepoint)) < 0) 
    vwarn("failed to handle %d complex actions!\n",rc);

    /*
     * If there is a complex action, just setup single step actions (and
     * we might already be single stepping for the complex action).
     * handle_complex_actions also paused all other threads if we needed to.
     */
    if (tpc->tac.action) {
    vdebug(4,LA_PROBE,LF_PROBEPOINT,"setup complex action for ");
    LOGDUMPPROBEPOINT(4,LA_PROBE,LF_PROBEPOINT,probepoint);
    vdebugc(4,LA_PROBE,LF_PROBEPOINT,"\n");

    int _isbp = 0;
    if (!tpc->tac.action->boosted)
        _isbp = 1;

    rc = setup_single_step_actions(target,tthread,probepoint,_isbp,stepping);
    if (rc == 1)
        rc = 0;
    }
    /*
     * Otherwise, if we did not perform a complex action, or if the
     * complex action did not require any single steps, figure out if we
     * should re-execute the original instructions -- and do we boost
     * them or replace them at the breakpoint and single step it.
     */
    else {
    tpc->did_orig_instr = 1;

    vdebug(4,LA_PROBE,LF_PROBEPOINT,"setting up post handling single step for ");
    LOGDUMPPROBEPOINT(4,LA_PROBE,LF_PROBEPOINT,probepoint);
    vdebugc(4,LA_PROBE,LF_PROBEPOINT,"\n");
    rc = setup_post_single_step(target,tthread,probepoint);

    if (rc == 0) {
        /*
         * No single step scheduled, but no error, so we're done
         * handling the probepoint in this thread; pop the stack.
         */
        if (target->blocking_thread == tthread)
        target->blocking_thread = NULL;
        probepoint_release(target,tthread,probepoint);
        tpc_free(tthread->tpc);
        tthread->tpc = (struct thread_probepoint_context *) \
        array_list_remove(tthread->tpc_stack);

        vdebug(5,LA_PROBE,LF_PROBEPOINT,
           "thread %"PRIiTID" skipped orig instruction; clearing tpc!\n",
           tthread->tid);

        /*
         * We need to setup single step actions to happen because we
         * are not stepping yet, and we might need to.
         */
        rc = setup_single_step_actions(target,tthread,probepoint,1,0);
        if (rc == 1) {
        /*
         * Don't call target_resume; we've already called
         * target_singlestep.
         */
        return RESULT_SUCCESS;
        }
    }
    else if (rc == 1) {
        /*
         * If we need to keep single stepping, just let that happen
         * -- it's already been set up (or might have been setup in
         * setup_post_single_step).
         *
         * We need to setup single step actions to happen even if
         * we're already stepping (bookkeeping).
         */
        rc = setup_single_step_actions(target,tthread,probepoint,1,1);

        /*
         * Don't call target_resume; we've already called
         * target_singlestep.
         */
        return RESULT_SUCCESS;
    }
    else if (rc == 2) {
        /* The thread blocked because it could not hold the probepoint. */
        vdebug(5,LA_PROBE,LF_PROBEPOINT,
           "thread %"PRIiTID" blocked before single step; thread"
           " %"PRIiTID" owned probepoint -- BUG!!!\n",
           tthread->tid,probepoint->tpc->thread->tid);
    }
    else if (rc < 0) {
        verror("could not setup single step; badness will probably ensue!\n");
    }
    }

    return RESULT_SUCCESS;
}

/*
 * This function handles single step events.  It broadly handles a few
 * cases.  First, are there pending single step actions; if so, stay in
 * single step mode after we're done.  Second, try to handle any complex
 * actions that might be needing single steps, if there are, let that
 * keep going.  Finally, if we're done with any complex actions, and we
 * still haven't run the original instruction (and if none of hte
 * complex actions obviated (replaced) the original one), we run the
 * original instruction via single step (if necessary -- it might not be
 * necessary if we don't have posthandlers and if the breakpoint is hw,
 * or if the orig instruction was boostable.
 */
result_t probepoint_ss_handler(struct target *target,
                   struct target_thread *tthread,
                   struct probepoint *probepoint) {
    struct thread_action_context *tac,*ttac;
    struct action *action;
    tid_t tid = tthread->tid;
    int rc;
    int handled_ss_actions = 0;
    int keep_stepping = 0;
    struct thread_probepoint_context *tpc = tthread->tpc;
    int noreinject;
    handler_msg_t amsg;
    struct probepoint *aprobepoint;
    REGVAL ipval;

    /*
     * If we had to disable a hw breakpoint before we single stepped it,
     * reenable it now.  If it's a hardware breakpoint, we own it, so
     * that's why we don't check that.
     */
    if (probepoint
    && probepoint->style == PROBEPOINT_HW
    && probepoint->debugregdisabled
    && !target->nodisablehwbponss) {
    /*
     * Reenable the hw breakpoint we just disabled.
     */
    target_enable_hw_breakpoint(target,probepoint->thread->tid,probepoint->debugregnum);
    probepoint->debugregdisabled = 0;
    }

    /*
     * First, if there is no probepoint (or if there is and we have
     * single step actions pending) and if this thread has pending
     * ss_actions.  If one or the other, go through that list, increment
     * the counts, notify the handlers, and remove any ss_actions that
     * are done.  If all are done, end singlestep mode and resume.
     * Otherwise, stay in single step mode.
     */
    if (!list_empty(&tthread->ss_actions)) {
    handled_ss_actions = 1;

    /*
     * If this address is an enalbed breakpiont, we need to send
     * MSG_STEPPING_AT_BP instead.  This covers the software
     * breakpiont case; for the hardware one, see bp_handler.
     */
    amsg = MSG_STEPPING;
    ipval = target_read_reg(target,tthread->tid,target->ipregno);
    aprobepoint = target_lookup_probepoint(target,tthread,ipval);
    if (aprobepoint && aprobepoint->state != PROBE_DISABLED)
        amsg = MSG_STEPPING_AT_BP;

    list_for_each_entry_safe(tac,ttac,&tthread->ss_actions,tac) {
        action = tac->action;
        ++tac->stepped;

        if (action->steps < 0 || tac->stepped < action->steps) {
        if (action->handler) 
            action->handler(action,tthread,action->probe,action->probe->probepoint,
                    amsg,tac->stepped,action->handler_data);
        }
        else {
        if (action->handler) 
            action->handler(action,tthread,action->probe,action->probe->probepoint,
                    MSG_SUCCESS,tac->stepped,action->handler_data);

        action_finish_handling(action,tac);

        list_del(&tac->tac);
        free(tac);
        }
    }

    if (!list_empty(&tthread->ss_actions)) 
        keep_stepping = 1;
    }
    /*
     * If there is no probepoint, we return to the caller without
     * unpausing the target.
     */
    else if (!probepoint) {
    vwarn("thread %"PRIiTID" unexpected single step!\n",tthread->tid);
    return RESULT_ERROR;
    }

    /*
     * If we're done handling actions and the post single step of the
     * original instruction, AND if we were the owners of the
     * probepoint, nuke the tpc state!
     *
     * BUT, we have to check if we should keep single stepping for
     * pending single step actions.
     */
    if (probepoint 
    && probepoint->tpc == tpc
    && probepoint->state == PROBE_BP_POSTHANDLING 
    && tpc->did_orig_instr) {
    noreinject = run_post_handlers(target,tthread,probepoint);

    if (!noreinject) {
        if (probepoint->style == PROBEPOINT_SW) {
        /* Re-inject a breakpoint for the next round */
        if (target_enable_sw_breakpoint(target,probepoint->thread->tid,
                        probepoint->mmod)) {
            verror("could not enable sw breakpoint instrs for bp re-insert, disabling!\n");
            probepoint->state = PROBE_DISABLED;
            return RESULT_ERROR;
        }
        else 
            probepoint->state = PROBE_BP_SET;
        }
        else if (probepoint->debugregdisabled) {
        /*
         * Enable hardware bp here!
         */
        target_enable_hw_breakpoint(target,probepoint->thread->tid,probepoint->debugregnum);
        probepoint->debugregdisabled = 0;

        probepoint->state = PROBE_BP_SET;
        }
        else {
        probepoint->state = PROBE_BP_SET;
        }
    }
    else {
        __probepoint_remove(probepoint,0,0);
    }

    if (target_singlestep_end(target,tid))
        verror("could not stop single stepping target"
           " after failed sstep!\n");

    if (target->blocking_thread == tthread)
        target->blocking_thread = NULL;
    probepoint_release(target,tthread,probepoint);
    tpc_free(tthread->tpc);
    tthread->tpc = (struct thread_probepoint_context *) \
        array_list_remove(tthread->tpc_stack);
    tpc = NULL;

    vdebug(5,LA_PROBE,LF_PROBEPOINT,
           "thread %"PRIiTID" ran orig instruction; cleared tpc!\n",
           tthread->tid);

    if (keep_stepping)
        goto keep_stepping;
    else 
        /* We're done with this, and don't want anything else below. */
        return RESULT_SUCCESS;
    }

    /* 
     * Handle complex actions.  This function does everything it might
     * need; if it leaves an action in tpc->tac.action, we just call
     * target_resume and trust that it did all the setup it needs.
     */
    if (tpc) 
    rc = handle_complex_actions(target,tthread,probepoint);

    /*
     * NOTE: after this giant if stmt, the default return case is
     * RESULT_SUCCESS, unless another return stmt occurs.
     */

    if (tpc && tpc->tac.action) {
    /*
     * If handle_complex_actions left something in tpc->tac.action,
     * we just want to return success and wait and see what happens
     * with the action via future debug expections.
     */
    ;
    }
    /*
     * If we stepped an action first, we might still need to single step
     * the original instruction; do that if so.  Or at least attempt it
     * -- if the action obviated the orig instruction,
     * setup_post_single_step handles that case and does the right things.
     */
    else if (tpc && !tpc->did_orig_instr) {
    vdebug(4,LA_PROBE,LF_PROBEPOINT,"setting up post handling single step for ");
    LOGDUMPPROBEPOINT(4,LA_PROBE,LF_PROBEPOINT,probepoint);
    vdebugc(4,LA_PROBE,LF_PROBEPOINT,"\n");
    rc = setup_post_single_step(target,tthread,probepoint);

    if (rc == 0) {
        /*
         * No single step scheduled, but no error, so we're done
         * handling the probepoint in this thread; pop the stack.
         */
        if (target->blocking_thread == tthread)
        target->blocking_thread = NULL;
        probepoint_release(target,tthread,probepoint);
        tpc_free(tthread->tpc);
        tthread->tpc = (struct thread_probepoint_context *) \
        array_list_remove(tthread->tpc_stack);

        vdebug(5,LA_PROBE,LF_PROBEPOINT,
           "thread %"PRIiTID" skipping orig instruction; clearing tpc!\n",
           tthread->tid);

        /*
         * If we need to keep stepping for single step actions, do
         * that here.
         */
        if (keep_stepping)
        goto keep_stepping;
        /*
        else {
            return RESULT_SUCCESS;
        }
        */
    }
    else if (rc == 1) {
        /* Stepping, so just return without target_resume! */
        tpc->did_orig_instr = 1;
        //return RESULT_SUCCESS;
    }
    else if (rc == 2) {
        /* The thread blocked because it could not hold the probepoint. */
        vdebug(5,LA_PROBE,LF_PROBEPOINT,
           "thread %"PRIiTID" blocked before single step real; thread"
           " %"PRIiTID" owned probepoint\n",
           tthread->tid,probepoint->tpc->thread->tid);
        //return RESULT_SUCCESS;
    }
    else if (rc < 0) {
        verror("could not setup single step; badness will probably ensue!\n");
        //return RESULT_SUCCESS;
    }
    }
    /*
     * If we don't have any complex actions to handle, we might still
     * need to stay in single step mode if any singlestep actions were
     * in progress for this thread.  So check that.
     *
     * The difference between this single step and a single step at the
     * probepoint is that we don't disable hardware breakpoints before
     * single stepping!
     */
    else if (keep_stepping) {
    keep_stepping:
    if (probepoint) {
        vdebug(4,LA_PROBE,LF_PROBEPOINT,"continuing single step for ");
        LOGDUMPPROBEPOINT(4,LA_PROBE,LF_PROBEPOINT,probepoint);
        vdebugc(4,LA_PROBE,LF_PROBEPOINT,"\n");
    }
    else 
        vdebug(4,LA_PROBE,LF_PROBEPOINT,
           "continuing single step after probepoint\n");

    if (target_singlestep(target,tid,0) < 0) {
        verror("could not keep single stepping target!\n");

        if (target_singlestep_end(target,tid))
        verror("could not stop single stepping target"
               " after failed sstep!\n");

        /*
         * All we can really do is notify all the single step
         * actions that we had an error, and nuke them, and keep
         * going.
         */
        list_for_each_entry_safe(tac,ttac,&tthread->ss_actions,tac) {
        if (tac->action->handler) 
            tac->action->handler(tac->action,tthread,tac->action->probe,
                     tac->action->probe->probepoint,
                     MSG_FAILURE,tac->stepped,
                     tac->action->handler_data);

        action_finish_handling(tac->action,tac);

        list_del(&tac->tac);
        free(tac);
        }

        return RESULT_ERROR;
    }
    else {
        /* 
         * If single step init succeeded, let the ss handler take
         * over.
         *
         * Don't call target_resume after a successful target_singlestep.
         */
        if (probepoint) {
        vdebug(4,LA_PROBE,LF_PROBEPOINT,"sstep command succeeded for ");
        LOGDUMPPROBEPOINT(4,LA_PROBE,LF_PROBEPOINT,probepoint);
        vdebugc(4,LA_PROBE,LF_PROBEPOINT,"\n");
        }
        else 
        vdebug(4,LA_PROBE,LF_PROBEPOINT,
               "sstep command succeeded after probepoint\n");
    }
    }
    /*
    else if (tpc->did_orig_instr) {
         *
     * We're totally done with this probepoint.
     *
    rc = 0;
    goto out;
    }
    */
    else if (!probepoint && !tpc && handled_ss_actions && !keep_stepping) {
    vdebug(4,LA_PROBE,LF_PROBEPOINT,
           "finished single step actions after probepoint\n");

    if (target_singlestep_end(target,tid))
        verror("could not stop single stepping target after single step"
           " actions after probepoint!\n");
    }
    else {
    verror("unexpected state!  BUG?\n");
    return RESULT_ERROR;
    }

    return RESULT_SUCCESS;
}

/*
 * This function handles the case where a thread is singlestepping, but
 * it has either stepped into a new context (i.e., user into kernel), or
 * into a different thread.  Initially, we only handle the case where
 * the breakpoint was just hit and the single step setup, but not run.
 * We do not handle the case where a single step action was running.
 *
 * This is much the same as the single step handler, BUT we abort any
 * running actions; we do not continue single stepping; and we unwind
 * all state associated with handling the breakpoint.
 *
 * NB: we cannot read any register state from the thread; another thread
 * or thread context (i.e., kernel instead of user) might have been
 * entered.  We just want to unwind the previous context and fixup the
 * probepoint.
 */
result_t probepoint_interrupted_ss_handler(struct target *target,
                       struct target_thread *tthread,
                       struct probepoint *probepoint) {
    struct thread_action_context *tac,*ttac;
    struct action *action;
    tid_t tid = tthread->tid;
    struct thread_probepoint_context *tpc;

    tpc = tthread->tpc;

    /*
     * If we had to disable a hw breakpoint before we single stepped it,
     * reenable it now.  If it's a hardware breakpoint, we own it, so
     * that's why we don't check that.
     */
    if (probepoint
    && probepoint->style == PROBEPOINT_HW
    && probepoint->debugregdisabled
    && !target->nodisablehwbponss) {
    /*
     * Reenable the hw breakpoint we just disabled.
     */
    target_enable_hw_breakpoint(target,probepoint->thread->tid,probepoint->debugregnum);
    probepoint->debugregdisabled = 0;
    }

    /*
     * Cancel any single step actions.
     */
    if (!list_empty(&tthread->ss_actions)) {
    list_for_each_entry_safe(tac,ttac,&tthread->ss_actions,tac) {
        action = tac->action;

        if (action->handler)
        action->handler(action,tthread,action->probe,
                action->probe->probepoint,
                MSG_INTERRUPTED,tac->stepped,
                action->handler_data);

        action_finish_handling(action,tac);

        list_del(&tac->tac);
        free(tac);
    }
    }

    /*
     * If we're done handling actions and the post single step of the
     * original instruction, AND if we were the owners of the
     * probepoint, nuke the tpc state!
     *
     * BUT, we have to check if we should keep single stepping for
     * pending single step actions.
     */
    if (probepoint->tpc == tpc) {
    /*
     * Cancel any complex actions.
     */
    if (!list_empty(&probepoint->complex_actions)) {
        list_for_each_entry_safe(tac,ttac,&probepoint->complex_actions,
                     tac) {
        action = tac->action;

        vdebug(5,LA_PROBE,LF_ACTION,
               "finished %d steps; done and removing interrupted"
               " action at ",
               tpc->tac.stepped);
        LOGDUMPPROBEPOINT(5,LA_PROBE,LF_ACTION,probepoint);
        vdebugc(5,LA_PROBE,LF_ACTION,"\n");

        if (action->handler) 
            action->handler(action,tthread,action->probe,
                    action->probe->probepoint,
                    MSG_INTERRUPTED,tac->stepped,
                    action->handler_data);

        action_finish_handling(action,tac);

        list_del(&tac->tac);
        free(tac);
        }
    }

    if (probepoint->style == PROBEPOINT_SW) {
        /* Re-inject a breakpoint for the next round */
        if (target_enable_sw_breakpoint(target,probepoint->thread->tid,
                        probepoint->mmod)) {
        verror("could not enable sw breakpoint instrs for bp re-insert, disabling!\n");
        probepoint->state = PROBE_DISABLED;
        return RESULT_ERROR;
        }
        else 
        probepoint->state = PROBE_BP_SET;
    }
    else if (probepoint->debugregdisabled) {
        /*
         * Enable hardware bp here!
         */
        target_enable_hw_breakpoint(target,probepoint->thread->tid,probepoint->debugregnum);
        probepoint->debugregdisabled = 0;

        probepoint->state = PROBE_BP_SET;
    }
    else {
        probepoint->state = PROBE_BP_SET;
    }

    probepoint_release(target,tthread,probepoint);
    }
    else
    vwarn("thread %"PRIiTID" does not own tpc (thread %"PRIiTID" does);"
          " cannot adjust probepoint state!!\n",
          tid,tpc->thread->tid);

    /* Do this stuff anyway. */
    if (target_singlestep_end(target,tid))
    verror("could not stop single stepping target"
           " after interrupted sstep!\n");

    if (target->blocking_thread == tthread)
    target->blocking_thread = NULL;
    tpc_free(tthread->tpc);
    tthread->tpc = (struct thread_probepoint_context *) \
    array_list_remove(tthread->tpc_stack);
    tpc = NULL;

    /*
     * Save it off so that probepoint_bp_handler will see it when we hit
     * the breakpoint again.
     */
    tthread->interrupted_ss_probepoint = probepoint;

    vdebug(5,LA_PROBE,LF_PROBEPOINT,
       "thread %"PRIiTID" interrupted before running orig instruction;"
       " cleared tpc!\n",
       tthread->tid);

    return RESULT_SUCCESS;
}

/*
 * This function should be called for each thread that has been left
 * paused before target_resume completes; if bp_handler or ss_handler
 * cleared 
 */
result_t probepoint_resumeat_handler(struct target *target,
                     struct target_thread *tthread) {
    struct probepoint *probepoint;
    struct thread_probepoint_context *tpc = tthread->tpc;
    int rc;
    tid_t tid = tthread->tid;
    struct thread_action_context *tac,*ttac;

    switch (tthread->resumeat) {
    case THREAD_RESUMEAT_NONE:
    return RESULT_ERROR;
    case THREAD_RESUMEAT_BPH:
    return probepoint_bp_handler(target,tthread,tthread->tpc->probepoint,0);
    case THREAD_RESUMEAT_SSR:
    return setup_post_single_step(target,tthread,tthread->tpc->probepoint);
    case THREAD_RESUMEAT_NA:
    /*
     * This could have only been interrupted comoing from the ss
     * handler, so we know that if it does not do an action and does
     * not stay in single step, we have to try to do the post single
     * step too (?)
     */
    probepoint = tthread->tpc->probepoint;
    handle_complex_actions(target,tthread,probepoint);
    if (!tpc->tac.action && !tpc->did_orig_instr) {
        vdebug(4,LA_PROBE,LF_PROBEPOINT,"setting up post handling single step for ");
        LOGDUMPPROBEPOINT(4,LA_PROBE,LF_PROBEPOINT,probepoint);
        vdebugc(4,LA_PROBE,LF_PROBEPOINT,"\n");
        rc = setup_post_single_step(target,tthread,probepoint);

        if (rc == 0) {
        /*
         * No single step scheduled, but no error, so we're done
         * handling the probepoint in this thread; pop the stack.
         */
        if (target->blocking_thread == tthread)
            target->blocking_thread = NULL;
        probepoint_release(target,tthread,probepoint);
        tpc_free(tthread->tpc);
        tthread->tpc = (struct thread_probepoint_context *) \
            array_list_remove(tthread->tpc_stack);

        vdebug(5,LA_PROBE,LF_PROBEPOINT,
               "thread %"PRIiTID" skipping orig instruction; clearing tpc!\n",
               tthread->tid);

        }
        else if (rc == 1) {
        /* Stepping, so just return without target_resume! */
        tpc->did_orig_instr = 1;
        //return RESULT_SUCCESS;
        }
        else if (rc == 2) {
        /* The thread blocked because it could not hold the probepoint. */
        vdebug(5,LA_PROBE,LF_PROBEPOINT,
               "thread %"PRIiTID" blocked before single step real; thread"
               " %"PRIiTID" owned probepoint\n",
               tthread->tid,probepoint->tpc->thread->tid);
        //return RESULT_SUCCESS;
        }
        else if (rc < 0) {
        verror("could not setup single step; badness will probably ensue!\n");
        //return RESULT_SUCCESS;
        }
    }
    else if (!tpc->tac.action && !tpc->tac.action->steps 
         && !list_empty(&tthread->ss_actions)) {
        vdebug(4,LA_PROBE,LF_PROBEPOINT,
           "continuing single step after probepoint\n");

        if (target_singlestep(target,tid,0) < 0) {
        verror("could not keep single stepping target!\n");

        if (target_singlestep_end(target,tid))
            verror("could not stop single stepping target"
               " after failed sstep!\n");

        /*
         * All we can really do is notify all the single step
         * actions that we had an error, and nuke them, and keep
         * going.
         */
        list_for_each_entry_safe(tac,ttac,&tthread->ss_actions,tac) {
            if (tac->action->handler) 
            tac->action->handler(tac->action,tthread,
                         tac->action->probe,
                         tac->action->probe->probepoint,
                         MSG_FAILURE,tac->stepped,
                         tac->action->handler_data);

            action_finish_handling(tac->action,tac);

            list_del(&tac->tac);
            free(tac);
        }

        return RESULT_ERROR;
        }
        else {
        /* 
         * If single step init succeeded, let the ss handler take
         * over.
         *
         * Don't call target_resume after a successful target_singlestep.
         */
        vdebug(4,LA_PROBE,LF_PROBEPOINT,"sstep command succeeded for resumeat ");
        LOGDUMPPROBEPOINT(4,LA_PROBE,LF_PROBEPOINT,probepoint);
        vdebugc(4,LA_PROBE,LF_PROBEPOINT,"\n");
        }
    }
    else {
        vdebug(4,LA_PROBE,LF_PROBEPOINT,
           "finished handling after resumeat\n");

        if (target_singlestep_end(target,tid))
        verror("could not stop single stepping target after single step"
               " actions after probepoint!\n");
    }
    return RESULT_SUCCESS;
    case THREAD_RESUMEAT_PH:
    return RESULT_ERROR;
    default:
    return RESULT_ERROR;
    }
}

static int __remove_action(struct target *target,struct probepoint *probepoint,
               struct action *action) {
    /*
     * If it was boosted, it will be removed when the action is destroyed.
     */
    if (action->boosted)
    return 0;

    if (action->type == ACTION_RETURN || action->type == ACTION_CUSTOMCODE) {
    if (probepoint->style == PROBEPOINT_SW) {
        if (target_unchange_sw_breakpoint(target,probepoint->thread->tid,
                          probepoint->mmod)) {
        verror("could not remove action code at the breakpoint;"
               " badness will probably ensue!\n");
        }
        if (target_enable_sw_breakpoint(target,probepoint->thread->tid,
                        probepoint->mmod)) {
        verror("could not reenable the breakpoint;"
               " badness will probably ensue!\n");
        return -1;
        }
    }
    else if (probepoint->mmod) {
        if (target_memmod_release(target,probepoint->thread->tid,
                      probepoint->mmod) < 0) {
        verror("could not remove action code at HW breakpoint;"
               " badness will probably ensue!\n");
        return -1;
        }
        else 
        probepoint->mmod = NULL;
    }
    }

    probepoint->state = PROBE_ACTION_DONE;

    return 0;
}

static int __insert_action(struct target *target,struct target_thread *tthread,
               struct probepoint *probepoint,struct action *action) {
    unsigned int buflen;
    unsigned char *buf;
    REGVAL rval;

    /* Set EIP to the address of our code. */
    if (target_write_reg(target,tthread->tid,target->ipregno,action->start_addr)) {
    verror("could not set EIP to action's first instruction (0x%"PRIxADDR")!\n",
           action->start_addr);
    return -1;
    }

    /*
     * If it was boosted, it was inserted when it was scheduled.
     */
    if (action->boosted)
    return 0;

    if (action->type == ACTION_RETURN) {
    /*
     * If we have executed a prologue: if the prologue contains
     * a save of the frame pointer (0x55), all we have to do is
     * set rsp to rbp, call leaveq, and call retq.
     * If the prologue does not contain a save of the frame
     * pointer, we have to track all modifications to rsp during
     * the prologue, undo them, and call leaveq, and retq.
     */
    if (action->detail.ret.prologue) {
        if (action->detail.ret.prologue_uses_bp) {
        vdebug(3,LA_PROBE,LF_ACTION,
               "setting ESP to EBP and returning (prologue uses EBP) at ");
        LOGDUMPPROBEPOINT(3,LA_PROBE,LF_ACTION,probepoint);
        vdebugc(3,LA_PROBE,LF_ACTION,"\n");

        errno = 0;
        rval = target_read_reg(target,tthread->tid,target->fbregno);
        if (errno) {
            verror("read EBP failed; action failed!\n");
            return -1;
        }

        if (target_write_reg(target,tthread->tid,target->spregno,rval)) {
            verror("set ESP to EBP failed; action failed and badness will ensue!\n");
            return -1;
        }

        buf = target->arch->full_ret_instrs;
        buflen = target->arch->full_ret_instrs_len;
        action->steps = target->arch->full_ret_instr_count;
        }
        else {
        vdebug(3,LA_PROBE,LF_ACTION,
               "undoing prologue ESP changes (%d) and returning at ",
               action->detail.ret.prologue_sp_offset);
        LOGDUMPPROBEPOINT(3,LA_PROBE,LF_ACTION,probepoint);
        vdebugc(3,LA_PROBE,LF_ACTION,"\n");

        errno = 0;
        rval = target_read_reg(target,tthread->tid,target->spregno);
        if (errno) {
            verror("read ESP failed; action failed!\n");
            return -1;
        }

        if (target_write_reg(target,tthread->tid,target->spregno,
                     rval + (REGVAL)-action->detail.ret.prologue_sp_offset)) {
            verror("undoing prologue ESP changes failed; action failed!\n");
            return -1;
        }

        buf = target->arch->ret_instrs;
        buflen = target->arch->ret_instrs_len;
        action->steps = target->arch->ret_instr_count;
        }
    }
    else {
        buf = target->arch->ret_instrs;
        buflen = target->arch->ret_instrs_len;
        action->steps = target->arch->ret_instr_count;
    }
    }
    else if (action->type == ACTION_CUSTOMCODE) {
    buf = action->detail.code.buf;
    buflen = action->detail.code.buflen;
    }
    else {
    verror("cannot handle unknown action type %d!\n",action->type);
    return -1;
    }

    if (probepoint->style == PROBEPOINT_SW) {
    if (target_change_sw_breakpoint(target,probepoint->thread->tid,
                    probepoint->mmod,buf,buflen)) {
        verror("could not insert action code; action failed!\n");
        return -1;
    }
    }
    else {
    if (!probepoint->mmod) {
        probepoint->mmod = target_memmod_create(target,probepoint->thread->tid,
                            probepoint->addr,0,MMT_CODE,
                            buf,buflen,0);
        if (!probepoint->mmod) {
        verror("could not create memmod for HW breakpoint code"
               " at 0x%"PRIxADDR"!\n",probepoint->addr);
        return -1;
        }
    }
    else {
        verror("could not create memmod for HW breakpoint code"
               " at 0x%"PRIxADDR"!\n",probepoint->addr);
        return -1;
    }
    }

    probepoint->state = PROBE_ACTION_RUNNING;

    return 0;
}

struct action *__get_next_complex_action(struct probepoint *probepoint,
                     struct action *current) {
    struct list_head *head = &probepoint->complex_actions;

    if (list_empty(head))
    return NULL;
    else if (!current) 
    return list_entry(head->next,typeof(*current),action);
    else if (current->action.next == head)
    return NULL;
    else
    return list_entry(current->action.next,struct action,action);
}

/*
 * This copies code into the breakpoint as necessary and single steps as
 * necessary, or sets things up to handle boosted instructions if that's
 * what we're doing.  It also handles single step events it has set up.
 * Basically, anything to do with complex actions, it handles.
 *
 * It does setup only; it does not resume the target; only its callers
 * should do that.
 *
 * If we setup a complex action, we are going to have to single step at
 * least one instruction (and maybe more).  If we did not set up an
 * action, we have to replace the original instruction by the real thing
 * and single step -- OR if it was boostable and target supported it, we
 * set EIP to the boosted location, and single step there if necessary,
 * and mess with EIP again afterward (or let the boosted instruction JMP
 * back to the real instruction following the real boosted
 * instruction.and its effects took the place of the original
 * instruction (obviated it), enable single stepping if needed.
 *
 * Returns: <0 on error; 0 if no actions requiring single step were
 * setup; 1 if actions requiring single step were setup (and thus single
 * step mode was enabled).
 */
static int handle_complex_actions(struct target *target,
                  struct target_thread *tthread,
                  struct probepoint *probepoint) {
    struct action *action,*nextaction = NULL;
    struct thread_probepoint_context *tpc;
    tid_t tid = tthread->tid;
    struct thread_action_context *tac,*ttac;
    struct thread_probepoint_context *htpc;

    tpc = tthread->tpc;

    /*
     * If we had paused this thread before handling an action because we
     * needed to hold the probepoint, but couldn't, jump straight to
     * that part.
     */
    if (tthread->resumeat == THREAD_RESUMEAT_NA) {
    action = nextaction = tpc->tac.action;
    goto nextaction;
    }

    /* 
     * If we just arrived here after hitting the breakpoint, reset our
     * state, and try to start an action.
     */
    if (probepoint->tpc == tpc 
    && probepoint->state == PROBE_BP_ACTIONHANDLING) {
    vdebug(5,LA_PROBE,LF_ACTION,
           "resetting actions state after bp hit at ");
    LOGDUMPPROBEPOINT(3,LA_PROBE,LF_ACTION,probepoint);
    vdebugc(5,LA_PROBE,LF_ACTION,"\n");

    tpc->tac.action = NULL;
    tpc->tac.stepped = 0;
    tpc->action_obviated_orig = 0;

    /* 
     * XXX: this could fail bad if whatever the current action
     * points to on the probepoint's list is removed from the list.
     * What to do???
     */
    nextaction = action = __get_next_complex_action(probepoint,NULL);
    if (!action) {
        vdebug(3,LA_PROBE,LF_ACTION,"no actions to run at ");
        LOGDUMPPROBEPOINT(3,LA_PROBE,LF_ACTION,probepoint);
        vdebugc(3,LA_PROBE,LF_ACTION,"\n");

        return 0;
    }
    }
    /*
     * If we need to keep stepping through this action, keep stepping.
     */
    else if (tpc->tac.action && tpc->tac.action->steps) {
    action = tpc->tac.action;
    /*
     * Increment the single step count no matter what.
     */
    ++tpc->tac.stepped;

    if (action->steps < 0 || tpc->tac.stepped < action->steps) {
        vdebug(5,LA_PROBE,LF_ACTION,
           "did %d steps; still more at ",tpc->tac.stepped);
        LOGDUMPPROBEPOINT(5,LA_PROBE,LF_ACTION,probepoint);
        vdebugc(5,LA_PROBE,LF_ACTION,"\n");

        if (action->handler) 
        action->handler(action,tthread,action->probe,probepoint,
                MSG_STEPPING,tpc->tac.stepped,
                action->handler_data);
    }
    else {
        vdebug(5,LA_PROBE,LF_ACTION,
           "finished %d steps; done and removing action at ",
           tpc->tac.stepped);
        LOGDUMPPROBEPOINT(5,LA_PROBE,LF_ACTION,probepoint);
        vdebugc(5,LA_PROBE,LF_ACTION,"\n");
        /*
         * If we know the action is done because it has finished its
         * set amount of single steps, we need to "finish" it:
         */
        if (action->handler) 
        action->handler(action,tthread,action->probe,probepoint,
                MSG_SUCCESS,tpc->tac.stepped,
                action->handler_data);

        __remove_action(target,probepoint,action);

        if (target_singlestep_end(target,tid))
        verror("could not stop single stepping target"
               " after single stepped action!\n");

        /* Grab the next one before we destroy this one. */
        nextaction = __get_next_complex_action(probepoint,action);

        action_finish_handling(action,&tpc->tac);

        action = nextaction;

        if (!nextaction) {
        tpc->tac.action = NULL;
        tpc->tac.stepped = 0;
        }
    }
    }
    /*
     * If we have a current action, but don't need single steps, we
     * don't want to do *anything* -- because we didn't initiate this
     * single step!  In future, we could warn the user...
     */
    else if (tpc->tac.action) {
    vwarn("unexpected single step!\n");
    return 0;
    }
    else if (!tpc->tac.action) {
    vdebug(5,LA_PROBE,LF_ACTION,"no action being handled at ");
    LOGDUMPPROBEPOINT(3,LA_PROBE,LF_ACTION,probepoint);
    vdebugc(5,LA_PROBE,LF_ACTION,"\n");
    return 0;
    }

 nextaction:
    if (nextaction) {
    /*
     * Start this action up!
     */

    /* Clean up state, then setup next action if there is one. */

    if (!nextaction->boosted) {
        /*
         * We need to grab the probepoint before we run this one!
         */
        if ((htpc = probepoint_hold(target,tthread,probepoint,tpc)) != tpc) {
        if (probepoint_pause_handling(target,tthread,probepoint,
                          THREAD_RESUMEAT_NA)) {
            verror("thread %"PRIiTID" hit nextaction when thread %"PRIiTID" already"
               " handling it; target does not support thread ctl!\n",
               tthread->tid,htpc->thread->tid);
            /*
             * There literally is nothing we can do -- we cannot
             * handle this breakpoint interrupt.
             */
            return -1;
        }
        else 
            return 0;
        }

        /*
         * If the action requires more than one single step, has
         * more than one instruction, and we're in the right BPMODE,
         * we have to pause all the other threads.
         */
        if (target->spec->bpmode == THREAD_BPMODE_STRICT
        || (target->spec->bpmode == THREAD_BPMODE_SEMI_STRICT
            && (action->steps > 1
            || (action->type == ACTION_CUSTOMCODE 
                && action->detail.code.instr_count > 1)))) {
        if (target_pause(target)) {
            vwarn("could not pause the target for blocking thread"
              " %"PRIiTID"!\n",tthread->tid);
            return -1;
        }
        target->blocking_thread = tthread;
        }
        else {
        if (target->blocking_thread == tthread)
            target->blocking_thread = NULL;
        }

        probepoint->state = PROBE_ACTION_RUNNING;
    }
    else {
        if (target->blocking_thread == tthread)
        target->blocking_thread = NULL;
    }

    __insert_action(target,tthread,probepoint,nextaction);

    tpc->tac.action = nextaction;

    tpc->action_obviated_orig |= nextaction->obviates;

    action = nextaction;
    }

    /*
     * Single step if the current action needs it.
     */
    if (tpc->tac.action && tpc->tac.action->steps) {
    vdebug(4,LA_PROBE,LF_PROBEPOINT,"single step for action at ");
    LOGDUMPPROBEPOINT(4,LA_PROBE,LF_PROBEPOINT,probepoint);
    vdebugc(4,LA_PROBE,LF_PROBEPOINT,"\n");

    int _isbp = 0;
    if (!tpc->tac.action->boosted && !tpc->tac.stepped) 
        _isbp = 1;

    if (probepoint->style == PROBEPOINT_HW
        && _isbp
        && !target->nodisablehwbponss) {
        /*
         * We need to disable the hw breakpoint before we single
         * step because the target can't do it.
         */
        target_disable_hw_breakpoint(target,probepoint->thread->tid,probepoint->debugregnum);
        probepoint->debugregdisabled = 1;
    }

    if (target_singlestep(target,tid,_isbp) < 0) {
        verror("could not keep single stepping target!\n");

        if (probepoint->style == PROBEPOINT_HW
        && _isbp
        && !target->nodisablehwbponss) {
        /*
         * Reenable the hw breakpoint we just disabled.
         */
        target_enable_hw_breakpoint(target,probepoint->thread->tid,probepoint->debugregnum);
        probepoint->debugregdisabled = 0;
        }

        if (target_singlestep_end(target,tid))
        verror("could not stop single stepping target"
               " after failed sstep!\n");

        /*
         * All we can really do is notify all the single step
         * actions that we had an error, and nuke them, and keep
         * going.
         */
        list_for_each_entry_safe(tac,ttac,&tthread->ss_actions,tac) {
        if (tac->action->handler) 
            tac->action->handler(tac->action,tthread,tac->action->probe,
                     action->probe->probepoint,
                     MSG_FAILURE,tac->stepped,
                     tac->action->handler_data);

        action_finish_handling(action,tac);

        list_del(&tac->tac);
        free(tac);
        }

        return -1;
    }
    else {
        /* 
         * If single step init succeeded, let the ss handler take
         * over.
         *
         * Don't call target_resume after a successful target_singlestep.
         */
        vdebug(4,LA_PROBE,LF_PROBEPOINT,"sstep command succeeded for action at ");
        LOGDUMPPROBEPOINT(4,LA_PROBE,LF_PROBEPOINT,probepoint);
        vdebugc(4,LA_PROBE,LF_PROBEPOINT,"\n");

        return 0;
    }

    return 1;
    }
    else if (tpc->tac.action) {
    vdebug(4,LA_PROBE,LF_PROBEPOINT,"NOT single stepping for action at ");
    LOGDUMPPROBEPOINT(4,LA_PROBE,LF_PROBEPOINT,probepoint);
    vdebugc(4,LA_PROBE,LF_PROBEPOINT,"\n");
    }

    return 0;
}

/* 
 * Schedules an action to occur, given a probe handler.  Actions can
 * only occur when a domain is paused after a probe breakpoint has been
 * hit.  Actions can be scheduled prior to beginning probing, or they
 * can be scheduled at probe handler runtime.
 *
 * Some actions may preclude others in the future.  For instance, a
 * return action depends greatly on the body of the called function NOT
 * being executed at all, so that %eax may be set and a 'ret'
 * instruction executed (so it's immediately after the 'call'
 * instruction; there is no state to clean up, etc.  Allowing a custom
 * code action prior to a return action might change the validity of
 * this assumption.
 *
 * But for now, the only restriction is
 *   - one return action per handle, and it will be performed after
 *     execution of the pre handler.
 *
 * Actions do not have priorities; they are executed in the order scheduled.
 */
int action_sched(struct probe *probe,struct action *action,
         action_whence_t whence,
         action_handler_t handler,void *handler_data) {
    struct action *lpc;
    unsigned char *code;
    unsigned int code_len = 0;
    struct probepoint *probepoint;
    struct target *target;
    int i;
    struct array_list *idata_list;
    struct inst_data *idata;

    if (action->probe != NULL) {
    verror("action already associated with probe!\n");
    return -1;
    }

    if (!probe->probepoint) {
    errno = EINVAL;
    verror("probe not attached to a probepoint!\n");
    return -1;
    }

    if (whence != ACTION_ONESHOT && whence != ACTION_REPEATPRE
    && whence != ACTION_REPEATPOST) {
    verror("unknown whence %d for action\n",whence);
    errno = EINVAL;
    return -1;
    }

    probepoint = probe->probepoint;
    target = probepoint->target;

    /*
     * If it's boosted, it's already set.
     */
    if (!action->boosted)
    action->start_addr = probepoint->addr;

    if (action->type == ACTION_REGMOD || action->type == ACTION_MEMMOD) {
    list_add_tail(&action->action,&probe->probepoint->simple_actions);
    }
    /* right now you can always enable singlestep actions */
    else if (action->type == ACTION_SINGLESTEP) {
    list_add_tail(&action->action,&probe->probepoint->ss_actions);
    }
    /* only allow one return action per probepoint */
    else if (action->type == ACTION_RETURN) {
    list_for_each_entry(lpc,&probe->probepoint->complex_actions,action) {
        if (lpc->type == ACTION_RETURN) {
        verror("probepoint already has return action\n");
        return -1;
        }
        else if (lpc->type == ACTION_CUSTOMCODE) {
        verror("probepoint already has customcode action\n");
        return -1;
        }
    }

    /* Try to disassemble and setup return from the prologue. */
    if (probepoint->symbol_addr 
        && probepoint->symbol_addr != probepoint->addr) {
        if (probepoint->symbol_addr > probepoint->addr) {
        vwarn("probepoint symbol addr < probepoint addr -- bad\n");
        }
        else {
        action->detail.ret.prologue = 1;

        /* Read the prologue; if the first byte is 0x55, we're
         * using frame pointers and we don't need to analyze the
         * prologue to watch the stack grow so we can undo it.
         * Otherwise, read the stack growth during the prologue
         * so we can undo it during a return.
         */
        code_len = probepoint->addr - probepoint->symbol_addr;
        code = (unsigned char *)malloc(code_len);
        memset(code,0,code_len);

        if (!target_read_addr(target,probepoint->symbol_addr,
                      code_len,code)) {
            vwarn("could not read prologue code; skipping disasm!\n");
            free(code);
            code = NULL;
        }
        else {
            /*
             * Check both for first instruction 0x55; any
             * instruction 0x55 (to catch functions that callq
             * elsewhere as their first instr); and disasm the
             * prologue to see %sp delta .  Then we can pick
             * which method we can use later.
             */

            /*
             * Don't require the first instruction to be 0x55
             * (push %ebp); look for it at any point in the
             * function!  We could also look for 0xc9 (leave).
             */
            if (*code == 0x55)
            action->detail.ret.prologue_uses_bp = 1;
            else if (disasm_generic(target,code,code_len,
                        &idata_list,1) == 0) {
            for (i = 0; i < array_list_len(idata_list); ++i) {
                idata = (struct inst_data *) \
                array_list_item(idata_list,i);
                if (idata->type == 0x55) {
                action->detail.ret.prologue_uses_bp = 1;
                break;
                }
            }
            if (idata_list)
                array_list_deep_free(idata_list);
            }
            else {
            vwarnopt(8,LA_PROBE,LF_ACTION,
                 "could not disassemble code in range"
                 "0x%"PRIxADDR"-0x%"PRIxADDR
                 " for function %s!\n",
                 probepoint->symbol_addr,probepoint->addr,
                 probepoint->bsymbol ? probepoint->bsymbol->lsymbol->symbol->name : "<UNKNOWN>");
            }

            if (action->detail.ret.prologue_uses_bp) {
            vdebug(3,LA_PROBE,LF_ACTION,
                   "function %s: pushes EBP (can leave; ret)\n",
                   probepoint->bsymbol ? probepoint->bsymbol->lsymbol->symbol->name : "<UNKNOWN>");
            }
#ifdef ENABLE_DISTORM

            /*
             * Ok, now disasm the prologue.
             */
            if (disasm_get_prologue_stack_size(target,code,code_len,
                               &action->detail.ret.prologue_sp_offset)) {
            verror("could not disassemble function prologue"
                   " to track stack growth for return action!\n");
            }
            else {
            action->detail.ret.prologue_has_sp_offset = 1;

            vdebug(3,LA_PROBE,LF_ACTION,
                   "disassembled prologue for function %s: sp moved %d\n",
                   probepoint->bsymbol ? probepoint->bsymbol->lsymbol->symbol->name : "<UNKNOWN>",
                   action->detail.ret.prologue_sp_offset);
            }
#else
            {
            verror("disasm support disabled; cannot check prologue"
                   " to unwind stack frame function %s!\n",
                   probepoint->bsymbol          \
                       ? probepoint->bsymbol->lsymbol->symbol->name \
                       : "<UNKNOWN>");
            }
#endif

            /* Clean up. */
            free(code);
            code = NULL;
        }
        }
    }

    /*
     * First check is redundant due to check in target_open, but
     * in case that goes away, it's here too.
     */
    if (target->spec->bpmode == THREAD_BPMODE_STRICT && !target->threadctl) {
        verror("cannot do return on strict target without threadctl!\n");
        errno = ENOTSUP;
        return -1;
    }
    else if (action->detail.ret.prologue && action->detail.ret.prologue_uses_bp
         && !action->boosted
         && !target->threadctl
         && target->arch->full_ret_instr_count > 1
         && target->spec->bpmode == THREAD_BPMODE_SEMI_STRICT) {
        if (action->detail.ret.prologue_has_sp_offset) {
        vdebug(8,LA_PROBE,LF_ACTION,
               "cannot use multi-instr full return; but can use SP"
               " adjustment and single-instr return\n");

        action->detail.ret.prologue_uses_bp = 0;
        }
        else {
        verror("cannot do non-boosted, multi-instruction return"
               " on strict target without threadctl!\n");
        errno = ENOTSUP;
        return -1;
        }
    }

    /*
     * We do not need to manually boost return instructions; if the
     * target supported it and had room, these are added to the
     * target when we attach.  BUT, return instructions ALWAYS must
     * be single stepped, because otherwise we don't know when we're
     * done returning (and thus can't call action handlers,
     * probepoint post handlers, garbage collect anything, etc).
     */

    list_add_tail(&action->action,&probe->probepoint->complex_actions);
    }
    /* only allow one customcode action per probepoint */
    else if (action->type == ACTION_CUSTOMCODE) {

    /*
     * For now, we always boost custom code so that it doesn't
     * interfere with the handling of the probepoint.  So, we
     * assemble our code buf according to the flags, copy in the
     * user's code, and end the code frag with a special breakpoint
     * probepoint so that we know when we're done with the custom
     * code.
     *
     * We have to assemble the code buf before we ask the target for
     * space from its boostable memory (if there is any -- there
     * might not be, or might not be enough).
     */

    list_for_each_entry(lpc,&probe->probepoint->complex_actions,action) {
        if (lpc->type == ACTION_RETURN) {
        verror("probepoint already has return action\n");
        return -1;
        }
        else if (lpc->type == ACTION_CUSTOMCODE) {
        verror("probepoint already has customcode action\n");
        return -1;
        }
    }

    /* XXX: this check should really let 1-instr actions go through */
    if ((target->spec->bpmode == THREAD_BPMODE_STRICT 
         || target->spec->bpmode == THREAD_BPMODE_SEMI_STRICT)
        && !action->boosted
        && !target->threadctl) {
        verror("cannot do return on strict target without threadctl!\n");
        errno = ENOTSUP;
        return -1;
    }

    list_add_tail(&action->action,&probe->probepoint->complex_actions);
    }

    /*
     * Ok, we're safe; memo-ize all the sched info into the action struct.
     */
    action->whence = whence;

    action->handler = handler;
    action->handler_data = handler_data;

    action->probe = probe;

    target_attach_action(target,action);

    RHOLD(action,probe);

    return 0;
}

/*
void __action_cancel_in_thread(struct target_thread *tthread,
                   struct action *action) {
    int i;
    struct thread_probepoint_context *tpc;

    if (!array_list_len(tthread->tpc_stack))
    return;

    for (i = 0; i < array_list_len(tthread->tpc_stack); ++i) {
    tpc = (struct thread_probepoint_context *) \
        array_list_item(tthread->tpc_stack,i);

    if (tpc->tac.action == action) {
        if (!action->isboosted) 
        vwarn("canceling a non-boosted action running in"
              " thread %"PRIiTID"; badness!!!\n",tthread->tid);

        // We have to mark it as canceled
        tpc->tac.canceled = 1;
        tpc->tac.nextaction = \
        __get_next_complex_action(action->probe->probepoint,action);

        action_release(action);
    }
    }

    // XXX: but we still have the problem of what happens when an
    //     action still has code at the breakpoint
}
*/

/*
 * Cancel an action.
 */
int action_cancel(struct action *action) {
    REFCNT trefcnt;

    if (!action->probe) {
    verror("cannot cancel action not associated with a probe!\n");
    return 1;
    }

    /*
     * XXX: this is bad, but correct.  We have to check all threads and
     * make sure that this action is not the one they are currently
     * executing; if so, we have to go mark the
     * thread_probepoint_context that was holding it as deleted, and
     * "release" the action manually.  I guess this means that actions
     * don't really need refcnting...
     */
    /*
    target = action->probe->probepoint->target;
    

    if (action->probe 
    && action->probe->probepoint
    && action->probe->probepoint->action == action) {
    verror("cannot cancel a currently-running action!\n");
    return 1;
    }
    */

    action->handler = NULL;
    action->handler_data = NULL;

    list_del(&action->action);
    action->probe = NULL;

    target_detach_action(action->target,action);

    RPUT(action,action,probe->probepoint,trefcnt);

    return 0;
}

/*
 * High-level actions that require little ASM knowledge.
 */
struct action *action_return(REGVAL retval) {
    struct action *action;

    action = (struct action *)calloc(1,sizeof(struct action));
    if (!action) {
    verror("could not malloc action: %s\n",strerror(errno));
    return NULL;
    }

    action->type = ACTION_RETURN;
    action->whence = ACTION_UNSCHED;
    INIT_LIST_HEAD(&action->action);

    action->detail.ret.retval = retval;

    action->obviates = 1;

    RHOLD(action,action);

    return action;
}

/*
 * Low-level actions that require little ASM knowledge, and may or may
 * not be permitted.
 */
struct action *action_singlestep(int nsteps) {
    struct action *action;

    if (nsteps == 0 || (nsteps < 0 && nsteps != SINGLESTEP_INFINITE 
                       && nsteps != SINGLESTEP_NEXTBP)) {
    errno = EINVAL;
    return NULL;
    }

    action = (struct action *)calloc(1,sizeof(struct action));
    if (!action) {
    verror("could not malloc action: %s\n",strerror(errno));
    return NULL;
    }

    action->type = ACTION_SINGLESTEP;
    action->whence = ACTION_UNSCHED;
    INIT_LIST_HEAD(&action->action);

    action->steps = nsteps;

    RHOLD(action,action);

    return action;
}

struct action *action_code(char *buf,uint32_t buflen,action_flag_t flags) {
    struct action *action;

    action = (struct action *)calloc(1,sizeof(struct action));
    if (!action) {
    verror("could not malloc action: %s\n",strerror(errno));
    return NULL;
    }

    action->type = ACTION_CUSTOMCODE;
    action->whence = ACTION_UNSCHED;
    INIT_LIST_HEAD(&action->action);

    action->detail.code.buf = malloc(buflen);
    memcpy(action->detail.code.buf,buf,buflen);
    action->detail.code.buflen = buflen;
    action->detail.code.flags = flags;

    RHOLD(action,action);

    return action;
}

struct action *action_regmod(REG regnum,REGVAL regval) {
    struct action *action;

    action = (struct action *)calloc(1,sizeof(struct action));
    if (!action) {
    verror("could not malloc action: %s\n",strerror(errno));
    return NULL;
    }

    action->type = ACTION_REGMOD;
    action->whence = ACTION_UNSCHED;
    INIT_LIST_HEAD(&action->action);

    action->detail.regmod.regnum = regnum;
    action->detail.regmod.regval = regval;

    RHOLD(action,action);

    return action;
}

struct action *action_memmod(ADDR dest,char *data,uint32_t len) {
    struct action *action;

    action = (struct action *)calloc(1,sizeof(struct action));
    if (!action) {
    verror("could not malloc action: %s\n",strerror(errno));
    return NULL;
    }

    action->type = ACTION_MEMMOD;
    action->whence = ACTION_UNSCHED;
    INIT_LIST_HEAD(&action->action);

    action->detail.memmod.destaddr = dest;
    action->detail.memmod.data = malloc(len);
    memcpy(action->detail.memmod.data,data,len);
    action->detail.memmod.len = len;

    RHOLD(action,action);

    return action;
}

REFCNT action_release(struct action *action) {
    REFCNT refcnt;
    RPUT(action,action,action,refcnt);
    return refcnt;
}

static void action_finish_handling(struct action *action,
                   struct thread_action_context *tac) {
    REFCNT trefcnt;

    /*
     * If the action is oneshot, cancel it.
     */
    if (action->whence == ACTION_ONESHOT) {
    if (tac)
        RPUT(action,action,tac,trefcnt);

    action_cancel(action);
    }
}

/*
 * Destroy an action (and cancel it first if necessary!).
 */
REFCNT action_free(struct action *action,int force) {
    int retval = action->refcnt;

    if (action->probe) {
    if (action_cancel(action)) {
        verror("could not cancel action; cannot destroy!\n");
        return 1;
    }
    }

    if (retval) {
    if (!force) {
        vwarn("cannot free action (%d refs)!\n",retval);
        return retval;
    }
    else {
        verror("forced free action (%d refs)\n",retval);
    }
    }

    if (action->type == ACTION_CUSTOMCODE
    && action->detail.code.buf) {
    free(action->detail.code.buf);
    }
    else if (action->type == ACTION_MEMMOD
         && action->detail.memmod.len) {
    free(action->detail.memmod.data);
    }

    free(action);

    return retval;
}