From patchwork Mon Sep 14 06:07:29 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Pavel Dovgalyuk X-Patchwork-Id: 11772891 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 96745618 for ; Mon, 14 Sep 2020 06:12:08 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 57864206F4 for ; Mon, 14 Sep 2020 06:12:08 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 57864206F4 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=ispras.ru Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Received: from localhost ([::1]:49526 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kHhih-0005Vo-AC for patchwork-qemu-devel@patchwork.kernel.org; Mon, 14 Sep 2020 02:12:07 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:37090) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kHheI-00047P-Bl for qemu-devel@nongnu.org; Mon, 14 Sep 2020 02:07:34 -0400 Received: from mail.ispras.ru ([83.149.199.84]:44992) by eggs.gnu.org with esmtps (TLS1.2:DHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kHheG-0002Qu-2j for qemu-devel@nongnu.org; Mon, 14 Sep 2020 02:07:33 -0400 Received: from [127.0.1.1] (unknown [62.118.151.149]) by mail.ispras.ru (Postfix) with ESMTPSA id 293C140D3BFF; Mon, 14 Sep 2020 06:07:30 +0000 (UTC) Subject: [PATCH v4 11/15] gdbstub: add reverse continue support in replay mode From: Pavel Dovgalyuk To: qemu-devel@nongnu.org Date: Mon, 14 Sep 2020 09:07:29 +0300 Message-ID: <160006364979.31457.720139270521139007.stgit@pasha-ThinkPad-X280> In-Reply-To: <160006358590.31457.16757371597343007847.stgit@pasha-ThinkPad-X280> References: <160006358590.31457.16757371597343007847.stgit@pasha-ThinkPad-X280> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 Received-SPF: pass client-ip=83.149.199.84; envelope-from=pavel.dovgalyuk@ispras.ru; helo=mail.ispras.ru X-detected-operating-system: by eggs.gnu.org: First seen = 2020/09/14 02:06:27 X-ACL-Warn: Detected OS = Linux 3.11 and newer [fuzzy] X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kwolf@redhat.com, wrampazz@redhat.com, pavel.dovgalyuk@ispras.ru, ehabkost@redhat.com, alex.bennee@linaro.org, mtosatti@redhat.com, armbru@redhat.com, mreitz@redhat.com, stefanha@redhat.com, crosa@redhat.com, pbonzini@redhat.com, philmd@redhat.com, zhiwei_liu@c-sky.com, rth@twiddle.net Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" From: Pavel Dovgalyuk 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 --- exec.c | 1 + gdbstub.c | 10 ++++++ include/sysemu/replay.h | 8 +++++ replay/replay-debugging.c | 71 +++++++++++++++++++++++++++++++++++++++++++++ softmmu/cpus.c | 5 +++ stubs/replay.c | 5 +++ 6 files changed, 99 insertions(+), 1 deletion(-) diff --git a/exec.c b/exec.c index 65983738f2..4333dde185 100644 --- a/exec.c +++ b/exec.c @@ -2756,6 +2756,7 @@ void cpu_check_watchpoint(CPUState *cpu, vaddr addr, vaddr len, * 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 79e8ccc050..ac92273018 100644 --- a/gdbstub.c +++ b/gdbstub.c @@ -1907,6 +1907,13 @@ static void handle_backward(GdbCmdContext *gdb_ctx, void *user_ctx) put_packet("E14"); } return; + case 'c': + if (replay_reverse_continue()) { + gdb_continue(); + } else { + put_packet("E14"); + } + return; } } @@ -2161,7 +2168,8 @@ static void handle_query_supported(GdbCmdContext *gdb_ctx, void *user_ctx) } if (replay_mode == REPLAY_MODE_PLAY) { - g_string_append(gdbserver_state.str_buf, ";ReverseStep+"); + g_string_append(gdbserver_state.str_buf, + ";ReverseStep+;ReverseContinue+"); } if (gdb_ctx->num_params && diff --git a/include/sysemu/replay.h b/include/sysemu/replay.h index 13a8123b09..b6cac175c4 100644 --- a/include/sysemu/replay.h +++ b/include/sysemu/replay.h @@ -81,11 +81,19 @@ 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 f7594a88cd..d02d4e0766 100644 --- a/replay/replay-debugging.c +++ b/replay/replay-debugging.c @@ -23,6 +23,8 @@ #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) { @@ -245,3 +247,72 @@ 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_icount(); + 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_icount() != 0) { + replay_seek(replay_get_current_icount() - 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_icount(); + return true; + } + + return false; +} + +void replay_breakpoint(void) +{ + assert(replay_mode == REPLAY_MODE_PLAY); + replay_last_breakpoint = replay_get_current_icount(); +} diff --git a/softmmu/cpus.c b/softmmu/cpus.c index dc72f93bc0..756f268993 100644 --- a/softmmu/cpus.c +++ b/softmmu/cpus.c @@ -1006,6 +1006,11 @@ static void cpu_handle_guest_debug(CPUState *cpu) { if (replay_running_debug()) { 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/stubs/replay.c b/stubs/replay.c index d5b52302e9..45ebe77fb9 100644 --- a/stubs/replay.c +++ b/stubs/replay.c @@ -98,3 +98,8 @@ bool replay_reverse_step(void) { return false; } + +bool replay_reverse_continue(void) +{ + return false; +}