From nobody Sat Sep 27 11:46:55 2025 Delivered-To: importer@patchew.org Received-SPF: pass (zoho.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Authentication-Results: mx.zohomail.com; spf=pass (zoho.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1547037060905187.07024779945561; Wed, 9 Jan 2019 04:31:00 -0800 (PST) Received: from localhost ([127.0.0.1]:50802 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ghD0d-0001Ca-G4 for importer@patchew.org; Wed, 09 Jan 2019 07:30:59 -0500 Received: from eggs.gnu.org ([209.51.188.92]:33570) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ghCjG-0004BP-1W for qemu-devel@nongnu.org; Wed, 09 Jan 2019 07:13:03 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ghCjE-00023A-LE for qemu-devel@nongnu.org; Wed, 09 Jan 2019 07:13:02 -0500 Received: from mail.ispras.ru ([83.149.199.45]:37376) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ghCjE-00022V-5L for qemu-devel@nongnu.org; Wed, 09 Jan 2019 07:13:00 -0500 Received: from [127.0.1.1] (unknown [85.142.117.226]) by mail.ispras.ru (Postfix) with ESMTPSA id A095954006A; Wed, 9 Jan 2019 15:12:58 +0300 (MSK) From: Pavel Dovgalyuk To: qemu-devel@nongnu.org Date: Wed, 09 Jan 2019 15:12:58 +0300 Message-ID: <154703597852.13472.17361215039546459735.stgit@pasha-VirtualBox> In-Reply-To: <154703587757.13472.3898702635363120794.stgit@pasha-VirtualBox> References: <154703587757.13472.3898702635363120794.stgit@pasha-VirtualBox> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x X-Received-From: 83.149.199.45 Subject: [Qemu-devel] [PATCH v9 17/21] gdbstub: add reverse continue support in replay mode X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kwolf@redhat.com, peter.maydell@linaro.org, war2jordan@live.com, pavel.dovgaluk@ispras.ru, pbonzini@redhat.com, crosthwaite.peter@gmail.com, ciro.santilli@gmail.com, jasowang@redhat.com, quintela@redhat.com, armbru@redhat.com, mreitz@redhat.com, alex.bennee@linaro.org, maria.klimushenkova@ispras.ru, mst@redhat.com, kraxel@redhat.com, boost.lists@gmail.com, thomas.dullien@googlemail.com, dovgaluk@ispras.ru, artem.k.pisarenko@gmail.com, dgilbert@redhat.com, rth@twiddle.net Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" 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 breakpoi= nt 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 --- 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 013341c..6ef0992 100644 --- a/cpus.c +++ b/cpus.c @@ -1110,6 +1110,11 @@ static void cpu_handle_guest_debug(CPUState *cpu) cpu->stopped =3D 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 10f2927..4278fcb 100644 --- a/exec.c +++ b/exec.c @@ -2744,6 +2744,7 @@ static void check_watchpoint(int offset, int len, Mem= TxAttrs attrs, int flags) * Don't process the watchpoints when we are * in a reverse debugging operation. */ + replay_breakpoint(); return; } if (flags =3D=3D BP_MEM_READ) { diff --git a/gdbstub.c b/gdbstub.c index 442187d..60176d5 100644 --- a/gdbstub.c +++ b/gdbstub.c @@ -1463,6 +1463,14 @@ 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; } @@ -1773,7 +1781,7 @@ static int gdb_handle_packet(GDBState *s, const char = *line_buf) pstrcat(buf, sizeof(buf), ";multiprocess+"); =20 if (replay_mode =3D=3D REPLAY_MODE_PLAY) { - pstrcat(buf, sizeof(buf), ";ReverseStep+"); + pstrcat(buf, sizeof(buf), ";ReverseStep+;ReverseContinue+"= ); } =20 put_packet(s, buf); diff --git a/include/sysemu/replay.h b/include/sysemu/replay.h index b0e2309..5baf10a 100644 --- a/include/sysemu/replay.h +++ b/include/sysemu/replay.h @@ -81,10 +81,18 @@ const char *replay_get_filename(void); */ 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); =20 /* Processing the instructions */ =20 diff --git a/replay/replay-debugging.c b/replay/replay-debugging.c index dfade54..98300ae 100644 --- a/replay/replay-debugging.c +++ b/replay/replay-debugging.c @@ -22,6 +22,8 @@ #include "migration/snapshot.h" =20 static bool replay_is_debugging; +static int64_t replay_last_breakpoint; +static int64_t replay_last_snapshot; =20 bool replay_running_debug(void) { @@ -249,3 +251,72 @@ bool replay_reverse_step(void) =20 return false; } + +static void replay_continue_end(void) +{ + replay_is_debugging =3D false; + vm_stop(RUN_STATE_DEBUG); + replay_break(-1LL, NULL, NULL); +} + +static void replay_continue_stop(void *opaque) +{ + Error *err =3D NULL; + if (replay_last_breakpoint !=3D -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 !=3D 0) { + replay_seek(replay_last_snapshot - 1, replay_continue_stop, &err); + if (err) { + error_free(err); + replay_continue_end(); + } + replay_last_snapshot =3D 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 =3D NULL; + + assert(replay_mode =3D=3D REPLAY_MODE_PLAY); + + if (replay_get_current_step() !=3D 0) { + replay_seek(replay_get_current_step() - 1, replay_continue_stop, &= err); + if (err) { + error_free(err); + return false; + } + replay_last_breakpoint =3D -1LL; + replay_is_debugging =3D true; + replay_last_snapshot =3D replay_get_current_step(); + return true; + } + + return false; +} + +void replay_breakpoint(void) +{ + assert(replay_mode =3D=3D REPLAY_MODE_PLAY); + replay_last_breakpoint =3D replay_get_current_step(); +} diff --git a/stubs/replay.c b/stubs/replay.c index 521552f..ee64972 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; +}