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[Qemu-devel] [PATCH v13 17/25] gdbstub: add reverse continue support in
From: |
Pavel Dovgalyuk |
Subject: |
[Qemu-devel] [PATCH v13 17/25] gdbstub: add reverse continue support in replay mode |
Date: |
Thu, 21 Feb 2019 14:05:40 +0300 |
User-agent: |
StGit/0.17.1-dirty |
This patch adds support of the reverse continue operation for gdbstub.
Reverse continue finds the last breakpoint that would happen in normal
execution from the beginning to the current moment.
Implementation of the reverse continue replays the execution twice:
to find the breakpoints that were hit and to seek to the last breakpoint.
Reverse continue loads the previous snapshot and tries to find the breakpoint
since that moment. If there are no such breakpoints, it proceeds to
the earlier snapshot, and so on. When no breakpoints or watchpoints were
hit at all, execution stops at the beginning of the replay log.
Signed-off-by: Pavel Dovgalyuk <address@hidden>
---
cpus.c | 5 +++
exec.c | 1 +
gdbstub.c | 10 ++++++
include/sysemu/replay.h | 8 +++++
replay/replay-debugging.c | 71 +++++++++++++++++++++++++++++++++++++++++++++
stubs/replay.c | 5 +++
6 files changed, 99 insertions(+), 1 deletion(-)
diff --git a/cpus.c b/cpus.c
index 408e10cff9..8b85703b31 100644
--- a/cpus.c
+++ b/cpus.c
@@ -1110,6 +1110,11 @@ static void cpu_handle_guest_debug(CPUState *cpu)
cpu->stopped = true;
} else {
if (!cpu->singlestep_enabled) {
+ /*
+ * Report about the breakpoint and
+ * make a single step to skip it
+ */
+ replay_breakpoint();
cpu_single_step(cpu, SSTEP_ENABLE);
} else {
cpu_single_step(cpu, 0);
diff --git a/exec.c b/exec.c
index fa6283d19c..39c8739c08 100644
--- a/exec.c
+++ b/exec.c
@@ -2747,6 +2747,7 @@ static void check_watchpoint(int offset, int len,
MemTxAttrs attrs, int flags)
* Don't process the watchpoints when we are
* in a reverse debugging operation.
*/
+ replay_breakpoint();
return;
}
if (flags == BP_MEM_READ) {
diff --git a/gdbstub.c b/gdbstub.c
index 9f987650ae..6e2dd9371f 100644
--- a/gdbstub.c
+++ b/gdbstub.c
@@ -1444,6 +1444,14 @@ static int gdb_handle_packet(GDBState *s, const char
*line_buf)
put_packet(s, "E14");
break;
}
+ case 'c':
+ if (replay_reverse_continue()) {
+ gdb_continue(s);
+ return RS_IDLE;
+ } else {
+ put_packet(s, "E14");
+ break;
+ }
default:
goto unknown_command;
}
@@ -1754,7 +1762,7 @@ 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+");
+ pstrcat(buf, sizeof(buf), ";ReverseStep+;ReverseContinue+");
}
put_packet(s, buf);
diff --git a/include/sysemu/replay.h b/include/sysemu/replay.h
index 533003f2b0..1d18c9b6ea 100644
--- a/include/sysemu/replay.h
+++ b/include/sysemu/replay.h
@@ -79,11 +79,19 @@ const char *replay_get_filename(void);
* Returns true on success.
*/
bool replay_reverse_step(void);
+/*
+ * Start searching the last breakpoint/watchpoint.
+ * Used by gdbstub for backwards debugging.
+ * Returns true if the process successfully started.
+ */
+bool replay_reverse_continue(void);
/*
* Returns true if replay module is processing
* reverse_continue or reverse_step request
*/
bool replay_running_debug(void);
+/* Called in reverse debugging mode to collect breakpoint information */
+void replay_breakpoint(void);
/* Processing the instructions */
diff --git a/replay/replay-debugging.c b/replay/replay-debugging.c
index 3d94859b8f..abb5fe687f 100644
--- a/replay/replay-debugging.c
+++ b/replay/replay-debugging.c
@@ -22,6 +22,8 @@
#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)
{
@@ -252,3 +254,72 @@ bool replay_reverse_step(void)
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_step();
+ 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_step() != 0) {
+ replay_seek(replay_get_current_step() - 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_step();
+ return true;
+ }
+
+ return false;
+}
+
+void replay_breakpoint(void)
+{
+ assert(replay_mode == REPLAY_MODE_PLAY);
+ replay_last_breakpoint = replay_get_current_step();
+}
diff --git a/stubs/replay.c b/stubs/replay.c
index 521552fa83..ee649726f4 100644
--- a/stubs/replay.c
+++ b/stubs/replay.c
@@ -85,3 +85,8 @@ bool replay_reverse_step(void)
{
return false;
}
+
+bool replay_reverse_continue(void)
+{
+ return false;
+}
- [Qemu-devel] [PATCH v13 08/25] migration: introduce icount field for snapshots, (continued)
- [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, 2019/02/21
- [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 <=
- [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
- [Qemu-devel] [PATCH v13 25/25] icount: clean up cpu_can_io before jumping to the next block, Pavel Dovgalyuk, 2019/02/21