From patchwork Thu Feb 21 11:05:40 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Pavel Dovgalyuk X-Patchwork-Id: 1046065 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (mailfrom) smtp.mailfrom=nongnu.org (client-ip=209.51.188.17; helo=lists.gnu.org; envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org; receiver=) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=ispras.ru Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 444sLy4590z9s5c for ; Thu, 21 Feb 2019 22:14:50 +1100 (AEDT) Received: from localhost ([127.0.0.1]:58395 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gwmJU-00086b-GC for incoming@patchwork.ozlabs.org; Thu, 21 Feb 2019 06:14:48 -0500 Received: from eggs.gnu.org ([209.51.188.92]:34233) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gwmAk-0000h4-9v for qemu-devel@nongnu.org; Thu, 21 Feb 2019 06:05:51 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gwmAi-0005Z6-JR for qemu-devel@nongnu.org; Thu, 21 Feb 2019 06:05:46 -0500 Received: from mail.ispras.ru ([83.149.199.45]:36202) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gwmAi-0005Sq-5f for qemu-devel@nongnu.org; Thu, 21 Feb 2019 06:05:44 -0500 Received: from [127.0.1.1] (unknown [85.142.117.226]) by mail.ispras.ru (Postfix) with ESMTPSA id BCE06540094; Thu, 21 Feb 2019 14:05:37 +0300 (MSK) From: Pavel Dovgalyuk To: qemu-devel@nongnu.org Date: Thu, 21 Feb 2019 14:05:40 +0300 Message-ID: <155074714022.32129.15580139450448277004.stgit@pasha-VirtualBox> In-Reply-To: <155074704329.32129.17530905097298071558.stgit@pasha-VirtualBox> References: <155074704329.32129.17530905097298071558.stgit@pasha-VirtualBox> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x X-Received-From: 83.149.199.45 Subject: [Qemu-devel] [PATCH v13 17/25] 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+incoming=patchwork.ozlabs.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 breakpoint 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 408e10cff9..8b85703b31 100644 --- a/cpus.c +++ b/cpus.c @@ -1110,6 +1110,11 @@ static void cpu_handle_guest_debug(CPUState *cpu) cpu->stopped = 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 fa6283d19c..39c8739c08 100644 --- a/exec.c +++ b/exec.c @@ -2747,6 +2747,7 @@ static void check_watchpoint(int offset, int len, MemTxAttrs attrs, int flags) * Don't process the watchpoints when we are * in a reverse debugging operation. */ + replay_breakpoint(); return; } if (flags == BP_MEM_READ) { diff --git a/gdbstub.c b/gdbstub.c index 9f987650ae..6e2dd9371f 100644 --- a/gdbstub.c +++ b/gdbstub.c @@ -1444,6 +1444,14 @@ 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; } @@ -1754,7 +1762,7 @@ static int gdb_handle_packet(GDBState *s, const char *line_buf) pstrcat(buf, sizeof(buf), ";multiprocess+"); if (replay_mode == REPLAY_MODE_PLAY) { - pstrcat(buf, sizeof(buf), ";ReverseStep+"); + pstrcat(buf, sizeof(buf), ";ReverseStep+;ReverseContinue+"); } put_packet(s, buf); diff --git a/include/sysemu/replay.h b/include/sysemu/replay.h index 533003f2b0..1d18c9b6ea 100644 --- a/include/sysemu/replay.h +++ b/include/sysemu/replay.h @@ -79,11 +79,19 @@ const char *replay_get_filename(void); * Returns true on success. */ 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); /* Processing the instructions */ diff --git a/replay/replay-debugging.c b/replay/replay-debugging.c index 3d94859b8f..abb5fe687f 100644 --- a/replay/replay-debugging.c +++ b/replay/replay-debugging.c @@ -22,6 +22,8 @@ #include "migration/snapshot.h" static bool replay_is_debugging; +static int64_t replay_last_breakpoint; +static int64_t replay_last_snapshot; bool replay_running_debug(void) { @@ -252,3 +254,72 @@ bool replay_reverse_step(void) return false; } + +static void replay_continue_end(void) +{ + replay_is_debugging = false; + vm_stop(RUN_STATE_DEBUG); + replay_delete_break(); +} + +static void replay_continue_stop(void *opaque) +{ + Error *err = NULL; + if (replay_last_breakpoint != -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 != 0) { + replay_seek(replay_last_snapshot - 1, replay_continue_stop, &err); + if (err) { + error_free(err); + replay_continue_end(); + } + replay_last_snapshot = 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 = NULL; + + assert(replay_mode == REPLAY_MODE_PLAY); + + if (replay_get_current_step() != 0) { + replay_seek(replay_get_current_step() - 1, replay_continue_stop, &err); + if (err) { + error_free(err); + return false; + } + replay_last_breakpoint = -1LL; + replay_is_debugging = true; + replay_last_snapshot = replay_get_current_step(); + return true; + } + + return false; +} + +void replay_breakpoint(void) +{ + assert(replay_mode == REPLAY_MODE_PLAY); + replay_last_breakpoint = replay_get_current_step(); +} diff --git a/stubs/replay.c b/stubs/replay.c index 521552fa83..ee649726f4 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; +}