When replaying a trace, it is possible to go from shutdown to running
with a reverse-debugging step. This can be useful if the problem being
debugged triggers a reset or shutdown.
This can be tested by making a recording of a machine that shuts down,
then using -action shutdown=pause when replaying it. Continuing to the
end of the trace then reverse-stepping in gdb crashes due to invalid
runstate transition.
Just permitting the transition seems to be all that's necessary for
reverse-debugging to work well in such a state.
Reviewed-by: Pavel Dovgalyuk <Pavel.Dovgalyuk@ispras.ru>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
include/sysemu/runstate.h | 1 +
replay/replay.c | 2 ++
system/runstate.c | 31 ++++++++++++++++++++++++++++---
3 files changed, 31 insertions(+), 3 deletions(-)
diff --git a/include/sysemu/runstate.h b/include/sysemu/runstate.h
index 0117d243c4..fe25eed3c0 100644
--- a/include/sysemu/runstate.h
+++ b/include/sysemu/runstate.h
@@ -9,6 +9,7 @@ void runstate_set(RunState new_state);
RunState runstate_get(void);
bool runstate_is_running(void);
bool runstate_needs_reset(void);
+void runstate_replay_enable(void);
typedef void VMChangeStateHandler(void *opaque, bool running, RunState state);
diff --git a/replay/replay.c b/replay/replay.c
index a2c576c16e..b8564a4813 100644
--- a/replay/replay.c
+++ b/replay/replay.c
@@ -385,6 +385,8 @@ static void replay_enable(const char *fname, int mode)
replay_fetch_data_kind();
}
+ runstate_replay_enable();
+
replay_init_events();
}
diff --git a/system/runstate.c b/system/runstate.c
index d6ab860eca..8f9ee034de 100644
--- a/system/runstate.c
+++ b/system/runstate.c
@@ -182,6 +182,12 @@ static const RunStateTransition runstate_transitions_def[] = {
{ RUN_STATE__MAX, RUN_STATE__MAX },
};
+static const RunStateTransition replay_play_runstate_transitions_def[] = {
+ { RUN_STATE_SHUTDOWN, RUN_STATE_RUNNING},
+
+ { RUN_STATE__MAX, RUN_STATE__MAX },
+};
+
static bool runstate_valid_transitions[RUN_STATE__MAX][RUN_STATE__MAX];
bool runstate_check(RunState state)
@@ -189,14 +195,33 @@ bool runstate_check(RunState state)
return current_run_state == state;
}
-static void runstate_init(void)
+static void transitions_set_valid(const RunStateTransition *rst)
{
const RunStateTransition *p;
- memset(&runstate_valid_transitions, 0, sizeof(runstate_valid_transitions));
- for (p = &runstate_transitions_def[0]; p->from != RUN_STATE__MAX; p++) {
+ for (p = rst; p->from != RUN_STATE__MAX; p++) {
runstate_valid_transitions[p->from][p->to] = true;
}
+}
+
+void runstate_replay_enable(void)
+{
+ assert(replay_mode != REPLAY_MODE_NONE);
+
+ if (replay_mode == REPLAY_MODE_PLAY) {
+ /*
+ * When reverse-debugging, it is possible to move state from
+ * shutdown to running.
+ */
+ transitions_set_valid(&replay_play_runstate_transitions_def[0]);
+ }
+}
+
+static void runstate_init(void)
+{
+ memset(&runstate_valid_transitions, 0, sizeof(runstate_valid_transitions));
+
+ transitions_set_valid(&runstate_transitions_def[0]);
qemu_mutex_init(&vmstop_lock);
}
--
2.42.0