On 9/22/20 2:55 PM, Philippe Mathieu-Daudé wrote:
> Hi Pavel,
>
> On 9/22/20 2:16 PM, Pavel Dovgalyuk wrote:
>> 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.dovgal...@ispras.ru>
>> ---
>> gdbstub.c | 1 +
>> include/sysemu/replay.h | 2 ++
>> replay/replay-debugging.c | 16 ++++++++++++++++
>> 3 files changed, 19 insertions(+)
>>
>> diff --git a/gdbstub.c b/gdbstub.c
>> index ac92273018..f19f98ab1a 100644
>> --- a/gdbstub.c
>> +++ b/gdbstub.c
>> @@ -3321,6 +3321,7 @@ static void gdb_chr_event(void *opaque, QEMUChrEvent
>> event)
>> s->g_cpu = s->c_cpu;
>>
>> vm_stop(RUN_STATE_PAUSED);
>> + replay_gdb_attached();
>> gdb_has_xml = false;
>> break;
>> default:
>> diff --git a/include/sysemu/replay.h b/include/sysemu/replay.h
>> index b6cac175c4..2aa34b8919 100644
>> --- a/include/sysemu/replay.h
>> +++ b/include/sysemu/replay.h
>> @@ -94,6 +94,8 @@ bool replay_reverse_continue(void);
>> bool replay_running_debug(void);
>> /* Called in reverse debugging mode to collect breakpoint information */
>> void replay_breakpoint(void);
>> +/* Called when gdb is attached to gdbstub */
>> +void replay_gdb_attached(void);
>>
>> /* Processing the instructions */
>>
>> diff --git a/replay/replay-debugging.c b/replay/replay-debugging.c
>> index d02d4e0766..bb9110707a 100644
>> --- a/replay/replay-debugging.c
>> +++ b/replay/replay-debugging.c
>> @@ -316,3 +316,19 @@ 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) {
>> + Error *err = NULL;
>> + if (save_snapshot("start_debugging", &err) != 0) {
>> + /* Can't create the snapshot. Continue conventional debugging.
>> */
>
> If you deliberately ignore the error, then use NULL;
> else display the error.
Can be cleaned on top, if Paolo is already OK with this series.
>
>> + error_free(err);
>> + }
>> + }
>> +}
>>
>
