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[Qemu-devel] [PATCH v13 16/25] gdbstub: add reverse step support in repl
From: |
Pavel Dovgalyuk |
Subject: |
[Qemu-devel] [PATCH v13 16/25] gdbstub: add reverse step support in replay mode |
Date: |
Thu, 21 Feb 2019 14:05:34 +0300 |
User-agent: |
StGit/0.17.1-dirty |
GDB remote protocol supports two reverse debugging commands:
reverse step and reverse continue.
This patch adds support of the first one to the gdbstub.
Reverse step is intended to step one instruction in the backwards
direction. This is not possible in regular execution.
But replayed execution is deterministic, therefore we can load one of
the prior snapshots and proceed to the desired step. It is equivalent
to stepping one instruction back.
There should be at least one snapshot preceding the debugged part of
the replay log.
Signed-off-by: Pavel Dovgalyuk <address@hidden>
---
accel/tcg/translator.c | 1 +
cpus.c | 14 +++++++++++---
exec.c | 7 +++++++
gdbstub.c | 44 +++++++++++++++++++++++++++++++++++++++++---
include/sysemu/replay.h | 11 +++++++++++
replay/replay-debugging.c | 33 +++++++++++++++++++++++++++++++++
stubs/replay.c | 5 +++++
7 files changed, 109 insertions(+), 6 deletions(-)
diff --git a/accel/tcg/translator.c b/accel/tcg/translator.c
index afd0a49ea6..33a543e82f 100644
--- a/accel/tcg/translator.c
+++ b/accel/tcg/translator.c
@@ -17,6 +17,7 @@
#include "exec/gen-icount.h"
#include "exec/log.h"
#include "exec/translator.h"
+#include "sysemu/replay.h"
/* Pairs with tcg_clear_temp_count.
To be called by #TranslatorOps.{translate_insn,tb_stop} if
diff --git a/cpus.c b/cpus.c
index a8910e9c01..408e10cff9 100644
--- a/cpus.c
+++ b/cpus.c
@@ -1104,9 +1104,17 @@ static bool cpu_can_run(CPUState *cpu)
static void cpu_handle_guest_debug(CPUState *cpu)
{
- gdb_set_stop_cpu(cpu);
- qemu_system_debug_request();
- cpu->stopped = true;
+ if (!replay_running_debug()) {
+ gdb_set_stop_cpu(cpu);
+ qemu_system_debug_request();
+ cpu->stopped = true;
+ } else {
+ if (!cpu->singlestep_enabled) {
+ cpu_single_step(cpu, SSTEP_ENABLE);
+ } else {
+ cpu_single_step(cpu, 0);
+ }
+ }
}
#ifdef CONFIG_LINUX
diff --git a/exec.c b/exec.c
index 518064530b..fa6283d19c 100644
--- a/exec.c
+++ b/exec.c
@@ -2742,6 +2742,13 @@ static void check_watchpoint(int offset, int len,
MemTxAttrs attrs, int flags)
QTAILQ_FOREACH(wp, &cpu->watchpoints, entry) {
if (cpu_watchpoint_address_matches(wp, vaddr, len)
&& (wp->flags & flags)) {
+ if (replay_running_debug()) {
+ /*
+ * Don't process the watchpoints when we are
+ * in a reverse debugging operation.
+ */
+ return;
+ }
if (flags == BP_MEM_READ) {
wp->flags |= BP_WATCHPOINT_HIT_READ;
} else {
diff --git a/gdbstub.c b/gdbstub.c
index bc774ae992..9f987650ae 100644
--- a/gdbstub.c
+++ b/gdbstub.c
@@ -39,6 +39,7 @@
#include "sysemu/kvm.h"
#include "exec/semihost.h"
#include "exec/exec-all.h"
+#include "sysemu/replay.h"
#ifdef CONFIG_USER_ONLY
#define GDB_ATTACHED "0"
@@ -344,6 +345,20 @@ typedef struct GDBState {
*/
static int sstep_flags = SSTEP_ENABLE|SSTEP_NOIRQ|SSTEP_NOTIMER;
+/* Retrieves flags for single step mode. */
+static int get_sstep_flags(void)
+{
+ /*
+ * In replay mode all events written into the log should be replayed.
+ * That is why NOIRQ flag is removed in this mode.
+ */
+ if (replay_mode != REPLAY_MODE_NONE) {
+ return SSTEP_ENABLE;
+ } else {
+ return sstep_flags;
+ }
+}
+
static GDBState *gdbserver_state;
bool gdb_has_xml;
@@ -434,7 +449,7 @@ static int gdb_continue_partial(GDBState *s, char
*newstates)
CPU_FOREACH(cpu) {
if (newstates[cpu->cpu_index] == 's') {
trace_gdbstub_op_stepping(cpu->cpu_index);
- cpu_single_step(cpu, sstep_flags);
+ cpu_single_step(cpu, get_sstep_flags());
}
}
s->running_state = 1;
@@ -453,7 +468,7 @@ static int gdb_continue_partial(GDBState *s, char
*newstates)
break; /* nothing to do here */
case 's':
trace_gdbstub_op_stepping(cpu->cpu_index);
- cpu_single_step(cpu, sstep_flags);
+ cpu_single_step(cpu, get_sstep_flags());
cpu_resume(cpu);
flag = 1;
break;
@@ -1414,9 +1429,28 @@ static int gdb_handle_packet(GDBState *s, const char
*line_buf)
addr = strtoull(p, (char **)&p, 16);
gdb_set_cpu_pc(s, addr);
}
- cpu_single_step(s->c_cpu, sstep_flags);
+ cpu_single_step(s->c_cpu, get_sstep_flags());
gdb_continue(s);
return RS_IDLE;
+ case 'b':
+ /* Backward debugging commands */
+ if (replay_mode == REPLAY_MODE_PLAY) {
+ switch (*p) {
+ case 's':
+ if (replay_reverse_step()) {
+ gdb_continue(s);
+ return RS_IDLE;
+ } else {
+ put_packet(s, "E14");
+ break;
+ }
+ default:
+ goto unknown_command;
+ }
+ } else {
+ put_packet(s, "E22");
+ }
+ goto unknown_command;
case 'F':
{
target_ulong ret;
@@ -1719,6 +1753,10 @@ static int gdb_handle_packet(GDBState *s, const char
*line_buf)
}
pstrcat(buf, sizeof(buf), ";multiprocess+");
+ if (replay_mode == REPLAY_MODE_PLAY) {
+ pstrcat(buf, sizeof(buf), ";ReverseStep+");
+ }
+
put_packet(s, buf);
break;
}
diff --git a/include/sysemu/replay.h b/include/sysemu/replay.h
index d7e859d915..533003f2b0 100644
--- a/include/sysemu/replay.h
+++ b/include/sysemu/replay.h
@@ -73,6 +73,17 @@ void replay_finish(void);
void replay_add_blocker(Error *reason);
/* Returns name of the replay log file */
const char *replay_get_filename(void);
+/*
+ * Start making one step in backward direction.
+ * Used by gdbstub for backwards debugging.
+ * Returns true on success.
+ */
+bool replay_reverse_step(void);
+/*
+ * Returns true if replay module is processing
+ * reverse_continue or reverse_step request
+ */
+bool replay_running_debug(void);
/* Processing the instructions */
diff --git a/replay/replay-debugging.c b/replay/replay-debugging.c
index e3821ab1ba..3d94859b8f 100644
--- a/replay/replay-debugging.c
+++ b/replay/replay-debugging.c
@@ -21,6 +21,13 @@
#include "block/snapshot.h"
#include "migration/snapshot.h"
+static bool replay_is_debugging;
+
+bool replay_running_debug(void)
+{
+ return replay_is_debugging;
+}
+
void hmp_info_replay(Monitor *mon, const QDict *qdict)
{
if (replay_mode == REPLAY_MODE_NONE) {
@@ -219,3 +226,29 @@ void hmp_replay_seek(Monitor *mon, const QDict *qdict)
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_step() != 0) {
+ replay_seek(replay_get_current_step() - 1, replay_stop_vm_debug, &err);
+ if (err) {
+ error_free(err);
+ return false;
+ }
+ replay_is_debugging = true;
+ return true;
+ }
+
+ return false;
+}
diff --git a/stubs/replay.c b/stubs/replay.c
index 4ac607895d..521552fa83 100644
--- a/stubs/replay.c
+++ b/stubs/replay.c
@@ -80,3 +80,8 @@ void replay_mutex_lock(void)
void replay_mutex_unlock(void)
{
}
+
+bool replay_reverse_step(void)
+{
+ return false;
+}
- [Qemu-devel] [PATCH v13 05/25] replay: don't drain/flush bdrv queue while RR is working, (continued)
- [Qemu-devel] [PATCH v13 05/25] replay: don't drain/flush bdrv queue while RR is working, Pavel Dovgalyuk, 2019/02/21
- [Qemu-devel] [PATCH v13 04/25] replay: update docs for record/replay with block devices, Pavel Dovgalyuk, 2019/02/21
- [Qemu-devel] [PATCH v13 06/25] replay: finish record/replay before closing the disks, Pavel Dovgalyuk, 2019/02/21
- [Qemu-devel] [PATCH v13 09/25] replay: provide an accessor for rr filename, Pavel Dovgalyuk, 2019/02/21
- [Qemu-devel] [PATCH v13 08/25] migration: introduce icount field for snapshots, Pavel Dovgalyuk, 2019/02/21
- [Qemu-devel] [PATCH v13 07/25] qcow2: introduce icount field for snapshots, Pavel Dovgalyuk, 2019/02/21
- [Qemu-devel] [PATCH v13 10/25] qapi: introduce replay.json for record/replay-related stuff, Pavel Dovgalyuk, 2019/02/21
- [Qemu-devel] [PATCH v13 11/25] replay: introduce info hmp/qmp command, Pavel Dovgalyuk, 2019/02/21
- [Qemu-devel] [PATCH v13 12/25] replay: introduce breakpoint at the specified step, Pavel Dovgalyuk, 2019/02/21
- [Qemu-devel] [PATCH v13 13/25] replay: implement replay-seek command, Pavel Dovgalyuk, 2019/02/21
- [Qemu-devel] [PATCH v13 16/25] gdbstub: add reverse step support in replay mode,
Pavel Dovgalyuk <=
- [Qemu-devel] [PATCH v13 14/25] replay: refine replay-time module, Pavel Dovgalyuk, 2019/02/21
- [Qemu-devel] [PATCH v13 18/25] replay: describe reverse debugging in docs/replay.txt, Pavel Dovgalyuk, 2019/02/21
- [Qemu-devel] [PATCH v13 15/25] replay: flush rr queue before loading the vmstate, Pavel Dovgalyuk, 2019/02/21
- [Qemu-devel] [PATCH v13 17/25] gdbstub: add reverse continue support in replay mode, Pavel Dovgalyuk, 2019/02/21
- [Qemu-devel] [PATCH v13 19/25] replay: add BH oneshot event for block layer, Pavel Dovgalyuk, 2019/02/21
- [Qemu-devel] [PATCH v13 20/25] replay: init rtc after enabling the replay, Pavel Dovgalyuk, 2019/02/21
- [Qemu-devel] [PATCH v13 21/25] replay: document development rules, Pavel Dovgalyuk, 2019/02/21
- [Qemu-devel] [PATCH v13 22/25] util/qemu-timer: refactor deadline calculation for external timers, Pavel Dovgalyuk, 2019/02/21
- [Qemu-devel] [PATCH v13 23/25] replay: fix replay shutdown, Pavel Dovgalyuk, 2019/02/21
- [Qemu-devel] [PATCH v13 24/25] replay: rename step-related variables and functions, Pavel Dovgalyuk, 2019/02/21