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replay: create temporary snapshot at debugger connection

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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>
This commit is contained in:
Pavel Dovgalyuk 2020-10-03 20:14:01 +03:00 committed by Paolo Bonzini
parent 9a608af3c0
commit 56357d80fc
3 changed files with 17 additions and 0 deletions
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1
gdbstub.c
View File

@ -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:

2
include/sysemu/replay.h
View File

@ -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 */

14
replay/replay-debugging.c
View File

@ -318,3 +318,17 @@ 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. */
}
}
}