From patchwork Wed Sep 12 08:19:28 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Pavel Dovgalyuk X-Patchwork-Id: 10597097 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 8CA3417DF for ; Wed, 12 Sep 2018 08:39:36 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 7A4ED29722 for ; Wed, 12 Sep 2018 08:39:36 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 6AAA829724; Wed, 12 Sep 2018 08:39:36 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id CDB8429724 for ; Wed, 12 Sep 2018 08:39:35 +0000 (UTC) Received: from localhost ([::1]:35137 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1g00gR-0008Tg-3x for patchwork-qemu-devel@patchwork.kernel.org; Wed, 12 Sep 2018 04:39:35 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:47555) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1g00N1-0001H5-CH for qemu-devel@nongnu.org; Wed, 12 Sep 2018 04:19:32 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1g00N0-0000j7-8a for qemu-devel@nongnu.org; Wed, 12 Sep 2018 04:19:31 -0400 Received: from mail.ispras.ru ([83.149.199.45]:56054) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1g00Mz-0000iY-R7 for qemu-devel@nongnu.org; Wed, 12 Sep 2018 04:19:30 -0400 Received: from [127.0.1.1] (unknown [85.142.117.226]) by mail.ispras.ru (Postfix) with ESMTPSA id E8A0F54008B; Wed, 12 Sep 2018 11:19:28 +0300 (MSK) From: Pavel Dovgalyuk To: qemu-devel@nongnu.org Date: Wed, 12 Sep 2018 11:19:28 +0300 Message-ID: <20180912081928.3228.10445.stgit@pasha-VirtualBox> In-Reply-To: <20180912081747.3228.21861.stgit@pasha-VirtualBox> References: <20180912081747.3228.21861.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 v6 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, 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+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" X-Virus-Scanned: ClamAV using ClamSMTP 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 09248dd..f31a70a 100644 --- a/cpus.c +++ b/cpus.c @@ -1090,6 +1090,9 @@ 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 eedddba..02d71b8 100644 --- a/exec.c +++ b/exec.c @@ -2741,6 +2741,7 @@ 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 fa108f4..ecdc0b2 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 55a272a..c1646b0 100644 --- a/include/sysemu/replay.h +++ b/include/sysemu/replay.h @@ -80,9 +80,15 @@ 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 a49d91e..81434d8 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 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; +}