From patchwork Wed May 23 06:51:18 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Pavel Dovgalyuk X-Patchwork-Id: 918789 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=2001:4830:134:3::11; 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 [IPv6:2001:4830:134:3::11]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 40rNmM00hhz9s1d for ; Wed, 23 May 2018 17:04:18 +1000 (AEST) Received: from localhost ([::1]:59575 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fLNom-00039W-K1 for incoming@patchwork.ozlabs.org; Wed, 23 May 2018 03:04:16 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50421) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fLNcF-0001wO-PB for qemu-devel@nongnu.org; Wed, 23 May 2018 02:51:20 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fLNcE-0000aY-Bh for qemu-devel@nongnu.org; Wed, 23 May 2018 02:51:19 -0400 Received: from mail.ispras.ru ([83.149.199.45]:36430) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fLNcD-0000aN-Ux for qemu-devel@nongnu.org; Wed, 23 May 2018 02:51:18 -0400 Received: from [127.0.1.1] (unknown [85.142.117.226]) by mail.ispras.ru (Postfix) with ESMTPSA id E8E5A54008A; Wed, 23 May 2018 09:51:16 +0300 (MSK) From: Pavel Dovgalyuk To: qemu-devel@nongnu.org Date: Wed, 23 May 2018 09:51:18 +0300 Message-ID: <20180523065118.26016.11321.stgit@pasha-VirtualBox> In-Reply-To: <20180523064941.26016.74274.stgit@pasha-VirtualBox> References: <20180523064941.26016.74274.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 [fuzzy] X-Received-From: 83.149.199.45 Subject: [Qemu-devel] [PATCH v3 17/19] 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, quintela@redhat.com, ciro.santilli@gmail.com, jasowang@redhat.com, crosthwaite.peter@gmail.com, zuban32s@gmail.com, armbru@redhat.com, maria.klimushenkova@ispras.ru, mst@redhat.com, kraxel@redhat.com, boost.lists@gmail.com, thomas.dullien@googlemail.com, dovgaluk@ispras.ru, mreitz@redhat.com, alex.bennee@linaro.org, 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 | 3 ++ exec.c | 1 + gdbstub.c | 10 ++++++- include/sysemu/replay.h | 6 ++++ replay/replay-debugging.c | 69 +++++++++++++++++++++++++++++++++++++++++++++ stubs/replay.c | 5 +++ 6 files changed, 93 insertions(+), 1 deletion(-) diff --git a/cpus.c b/cpus.c index 01016af..21bd26f 100644 --- a/cpus.c +++ b/cpus.c @@ -1048,6 +1048,9 @@ 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 fd037f8..947207c 100644 --- a/exec.c +++ b/exec.c @@ -2584,6 +2584,7 @@ static void check_watchpoint(int offset, int len, MemTxAttrs attrs, int flags) if (replay_running_debug()) { /* 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 12aac79..7771fc1 100644 --- a/gdbstub.c +++ b/gdbstub.c @@ -1111,6 +1111,14 @@ 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; } @@ -1381,7 +1389,7 @@ static int gdb_handle_packet(GDBState *s, const char *line_buf) pstrcat(buf, sizeof(buf), ";qXfer:features:read+"); } if (replay_mode == REPLAY_MODE_PLAY) { - pstrcat(buf, sizeof(buf), ";ReverseStep+"); + pstrcat(buf, sizeof(buf), ";ReverseStep+;ReverseContinue+"); } put_packet(s, buf); break; diff --git a/include/sysemu/replay.h b/include/sysemu/replay.h index 611eabb..a3113c1 100644 --- a/include/sysemu/replay.h +++ b/include/sysemu/replay.h @@ -78,9 +78,15 @@ void replay_break(int64_t step, QEMUTimerCB callback, void *opaque); Used by gdbstub for backwards debugging. 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 388cf12..edab98e 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) { @@ -216,3 +218,70 @@ bool replay_reverse_step(void) return false; } + +static void replay_continue_end(void) +{ + replay_is_debugging = false; + vm_stop(RUN_STATE_DEBUG); + replay_break(-1LL, NULL, NULL); +} + +static void replay_continue_stop(void *opaque) +{ + Error *err = NULL; + if (replay_last_breakpoint != -1LL) { + replay_seek(replay_last_breakpoint, &err, replay_stop_vm_debug); + 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, &err, replay_continue_stop); + 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, &err, replay_stop_vm_debug); + 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, &err, replay_continue_stop); + 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 b0fba0e..781974e 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; +}