From fda8458bd3a9cb3108ba2f09921b6e3eee0d1bf3 Mon Sep 17 00:00:00 2001 From: Pavel Dovgalyuk Date: Sat, 3 Oct 2020 20:13:43 +0300 Subject: gdbstub: add reverse step support in replay mode MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Reviewed-by: Alex Bennée -- v4 changes: - inverted condition in cpu_handle_guest_debug (suggested by Alex Bennée) Message-Id: <160174522341.12451.1498758422543765253.stgit@pasha-ThinkPad-X280> Signed-off-by: Paolo Bonzini --- replay/replay-debugging.c | 34 ++++++++++++++++++++++++++++++++++ 1 file changed, 34 insertions(+) (limited to 'replay/replay-debugging.c') diff --git a/replay/replay-debugging.c b/replay/replay-debugging.c index e1fe6b8661..1e1dec0295 100644 --- a/replay/replay-debugging.c +++ b/replay/replay-debugging.c @@ -22,6 +22,13 @@ #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) { @@ -212,3 +219,30 @@ 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_icount() != 0) { + replay_seek(replay_get_current_icount() - 1, + replay_stop_vm_debug, &err); + if (err) { + error_free(err); + return false; + } + replay_is_debugging = true; + return true; + } + + return false; +} -- cgit v1.2.3