qemu/replay/replay-debugging.c
Pavel Dovgalyuk 56357d80fc replay: create temporary snapshot at debugger connection
When record/replay does not uses overlays for storing the snapshots,
user is not capable of issuing reverse debugging commands.
This patch adds creation of the VM snapshot on the temporary
overlay image, when the debugger connects to QEMU.
Therefore the execution can be rewind to the moment
of the debugger connection while debugging the virtual machine.

Signed-off-by: Pavel Dovgalyuk <Pavel.Dovgalyuk@ispras.ru>

--

v6:
 - dropped unused error processing (suggested by Philippe Mathieu-Daudé)
Message-Id: <160174524096.12451.11651270339216758643.stgit@pasha-ThinkPad-X280>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-10-06 08:34:49 +02:00

335 lines
8.2 KiB
C

/*
* replay-debugging.c
*
* Copyright (c) 2010-2020 Institute for System Programming
* of the Russian Academy of Sciences.
*
* This work is licensed under the terms of the GNU GPL, version 2 or later.
* See the COPYING file in the top-level directory.
*
*/
#include "qemu/osdep.h"
#include "qapi/error.h"
#include "sysemu/replay.h"
#include "sysemu/runstate.h"
#include "replay-internal.h"
#include "monitor/hmp.h"
#include "monitor/monitor.h"
#include "qapi/qapi-commands-replay.h"
#include "qapi/qmp/qdict.h"
#include "qemu/timer.h"
#include "block/snapshot.h"
#include "migration/snapshot.h"
static bool replay_is_debugging;
static int64_t replay_last_breakpoint;
static int64_t replay_last_snapshot;
bool replay_running_debug(void)
{
return replay_is_debugging;
}
void hmp_info_replay(Monitor *mon, const QDict *qdict)
{
if (replay_mode == REPLAY_MODE_NONE) {
monitor_printf(mon, "Record/replay is not active\n");
} else {
monitor_printf(mon,
"%s execution '%s': instruction count = %"PRId64"\n",
replay_mode == REPLAY_MODE_RECORD ? "Recording" : "Replaying",
replay_get_filename(), replay_get_current_icount());
}
}
ReplayInfo *qmp_query_replay(Error **errp)
{
ReplayInfo *retval = g_new0(ReplayInfo, 1);
retval->mode = replay_mode;
if (replay_get_filename()) {
retval->filename = g_strdup(replay_get_filename());
retval->has_filename = true;
}
retval->icount = replay_get_current_icount();
return retval;
}
static void replay_break(uint64_t icount, QEMUTimerCB callback, void *opaque)
{
assert(replay_mode == REPLAY_MODE_PLAY);
assert(replay_mutex_locked());
assert(replay_break_icount >= replay_get_current_icount());
assert(callback);
replay_break_icount = icount;
if (replay_break_timer) {
timer_del(replay_break_timer);
}
replay_break_timer = timer_new_ns(QEMU_CLOCK_REALTIME,
callback, opaque);
}
static void replay_delete_break(void)
{
assert(replay_mode == REPLAY_MODE_PLAY);
assert(replay_mutex_locked());
if (replay_break_timer) {
timer_del(replay_break_timer);
timer_free(replay_break_timer);
replay_break_timer = NULL;
}
replay_break_icount = -1ULL;
}
static void replay_stop_vm(void *opaque)
{
vm_stop(RUN_STATE_PAUSED);
replay_delete_break();
}
void qmp_replay_break(int64_t icount, Error **errp)
{
if (replay_mode == REPLAY_MODE_PLAY) {
if (icount >= replay_get_current_icount()) {
replay_break(icount, replay_stop_vm, NULL);
} else {
error_setg(errp,
"cannot set breakpoint at the instruction in the past");
}
} else {
error_setg(errp, "setting the breakpoint is allowed only in play mode");
}
}
void hmp_replay_break(Monitor *mon, const QDict *qdict)
{
int64_t icount = qdict_get_try_int(qdict, "icount", -1LL);
Error *err = NULL;
qmp_replay_break(icount, &err);
if (err) {
error_report_err(err);
return;
}
}
void qmp_replay_delete_break(Error **errp)
{
if (replay_mode == REPLAY_MODE_PLAY) {
replay_delete_break();
} else {
error_setg(errp, "replay breakpoints are allowed only in play mode");
}
}
void hmp_replay_delete_break(Monitor *mon, const QDict *qdict)
{
Error *err = NULL;
qmp_replay_delete_break(&err);
if (err) {
error_report_err(err);
return;
}
}
static char *replay_find_nearest_snapshot(int64_t icount,
int64_t *snapshot_icount)
{
BlockDriverState *bs;
QEMUSnapshotInfo *sn_tab;
QEMUSnapshotInfo *nearest = NULL;
char *ret = NULL;
int nb_sns, i;
AioContext *aio_context;
*snapshot_icount = -1;
bs = bdrv_all_find_vmstate_bs();
if (!bs) {
goto fail;
}
aio_context = bdrv_get_aio_context(bs);
aio_context_acquire(aio_context);
nb_sns = bdrv_snapshot_list(bs, &sn_tab);
aio_context_release(aio_context);
for (i = 0; i < nb_sns; i++) {
if (bdrv_all_find_snapshot(sn_tab[i].name, &bs) == 0) {
if (sn_tab[i].icount != -1ULL
&& sn_tab[i].icount <= icount
&& (!nearest || nearest->icount < sn_tab[i].icount)) {
nearest = &sn_tab[i];
}
}
}
if (nearest) {
ret = g_strdup(nearest->name);
*snapshot_icount = nearest->icount;
}
g_free(sn_tab);
fail:
return ret;
}
static void replay_seek(int64_t icount, QEMUTimerCB callback, Error **errp)
{
char *snapshot = NULL;
int64_t snapshot_icount;
if (replay_mode != REPLAY_MODE_PLAY) {
error_setg(errp, "replay must be enabled to seek");
return;
}
snapshot = replay_find_nearest_snapshot(icount, &snapshot_icount);
if (snapshot) {
if (icount < replay_get_current_icount()
|| replay_get_current_icount() < snapshot_icount) {
vm_stop(RUN_STATE_RESTORE_VM);
load_snapshot(snapshot, errp);
}
g_free(snapshot);
}
if (replay_get_current_icount() <= icount) {
replay_break(icount, callback, NULL);
vm_start();
} else {
error_setg(errp, "cannot seek to the specified instruction count");
}
}
void qmp_replay_seek(int64_t icount, Error **errp)
{
replay_seek(icount, replay_stop_vm, errp);
}
void hmp_replay_seek(Monitor *mon, const QDict *qdict)
{
int64_t icount = qdict_get_try_int(qdict, "icount", -1LL);
Error *err = NULL;
qmp_replay_seek(icount, &err);
if (err) {
error_report_err(err);
return;
}
}
static void replay_stop_vm_debug(void *opaque)
{
replay_is_debugging = false;
vm_stop(RUN_STATE_DEBUG);
replay_delete_break();
}
bool replay_reverse_step(void)
{
Error *err = NULL;
assert(replay_mode == REPLAY_MODE_PLAY);
if (replay_get_current_icount() != 0) {
replay_seek(replay_get_current_icount() - 1,
replay_stop_vm_debug, &err);
if (err) {
error_free(err);
return false;
}
replay_is_debugging = true;
return true;
}
return false;
}
static void replay_continue_end(void)
{
replay_is_debugging = false;
vm_stop(RUN_STATE_DEBUG);
replay_delete_break();
}
static void replay_continue_stop(void *opaque)
{
Error *err = NULL;
if (replay_last_breakpoint != -1LL) {
replay_seek(replay_last_breakpoint, replay_stop_vm_debug, &err);
if (err) {
error_free(err);
replay_continue_end();
}
return;
}
/*
* No breakpoints since the last snapshot.
* Find previous snapshot and try again.
*/
if (replay_last_snapshot != 0) {
replay_seek(replay_last_snapshot - 1, replay_continue_stop, &err);
if (err) {
error_free(err);
replay_continue_end();
}
replay_last_snapshot = replay_get_current_icount();
return;
} else {
/* Seek to the very first step */
replay_seek(0, replay_stop_vm_debug, &err);
if (err) {
error_free(err);
replay_continue_end();
}
return;
}
replay_continue_end();
}
bool replay_reverse_continue(void)
{
Error *err = NULL;
assert(replay_mode == REPLAY_MODE_PLAY);
if (replay_get_current_icount() != 0) {
replay_seek(replay_get_current_icount() - 1,
replay_continue_stop, &err);
if (err) {
error_free(err);
return false;
}
replay_last_breakpoint = -1LL;
replay_is_debugging = true;
replay_last_snapshot = replay_get_current_icount();
return true;
}
return false;
}
void replay_breakpoint(void)
{
assert(replay_mode == REPLAY_MODE_PLAY);
replay_last_breakpoint = replay_get_current_icount();
}
void replay_gdb_attached(void)
{
/*
* Create VM snapshot on temporary overlay to allow reverse
* debugging even if snapshots were not enabled.
*/
if (replay_mode == REPLAY_MODE_PLAY
&& !replay_snapshot) {
if (save_snapshot("start_debugging", NULL) != 0) {
/* Can't create the snapshot. Continue conventional debugging. */
}
}
}