From patchwork Tue Sep 29 11:02:02 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Pavel Dovgalyuk X-Patchwork-Id: 1373310 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) 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=fail (p=none dis=none) header.from=ispras.ru 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 ozlabs.org (Postfix) with ESMTPS id 4C0xZP64zkz9sTh for ; Tue, 29 Sep 2020 21:13:01 +1000 (AEST) Received: from localhost ([::1]:39150 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kNDZ5-0007ld-SW for incoming@patchwork.ozlabs.org; Tue, 29 Sep 2020 07:12:59 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:56888) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kNDOa-0003Sg-A7 for qemu-devel@nongnu.org; Tue, 29 Sep 2020 07:02:09 -0400 Received: from mail.ispras.ru ([83.149.199.84]:35236) by eggs.gnu.org with esmtps (TLS1.2:DHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kNDOW-0002fw-RT for qemu-devel@nongnu.org; Tue, 29 Sep 2020 07:02:07 -0400 Received: from [127.0.1.1] (unknown [62.118.151.149]) by mail.ispras.ru (Postfix) with ESMTPSA id E3DB840F9AAE; Tue, 29 Sep 2020 11:02:02 +0000 (UTC) Subject: [PATCH v6 10/14] gdbstub: add reverse step support in replay mode From: Pavel Dovgalyuk To: qemu-devel@nongnu.org Date: Tue, 29 Sep 2020 14:02:02 +0300 Message-ID: <160137732259.31007.5735475002586923857.stgit@pasha-ThinkPad-X280> In-Reply-To: <160137726426.31007.12061315974029139983.stgit@pasha-ThinkPad-X280> References: <160137726426.31007.12061315974029139983.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 = 2020/09/29 07:01:05 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+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" From: Pavel Dovgalyuk GDB remote protocol supports two reverse debugging commands: reverse step and reverse continue. This patch adds support of the first one to the gdbstub. Reverse step is intended to step one instruction in the backwards direction. This is not possible in regular execution. But replayed execution is deterministic, therefore we can load one of the prior snapshots and proceed to the desired step. It is equivalent to stepping one instruction back. There should be at least one snapshot preceding the debugged part of the replay log. Signed-off-by: Pavel Dovgalyuk Reviewed-by: Alex Bennée --- v4 changes: - inverted condition in cpu_handle_guest_debug (suggested by Alex Bennée) --- accel/tcg/translator.c | 1 + exec.c | 7 ++++++ gdbstub.c | 55 +++++++++++++++++++++++++++++++++++++++++++-- include/sysemu/replay.h | 11 +++++++++ replay/replay-debugging.c | 33 +++++++++++++++++++++++++++ softmmu/cpus.c | 14 +++++++++-- stubs/replay.c | 5 ++++ 7 files changed, 121 insertions(+), 5 deletions(-) diff --git a/accel/tcg/translator.c b/accel/tcg/translator.c index 603d17ff83..fb1e19c585 100644 --- a/accel/tcg/translator.c +++ b/accel/tcg/translator.c @@ -17,6 +17,7 @@ #include "exec/log.h" #include "exec/translator.h" #include "exec/plugin-gen.h" +#include "sysemu/replay.h" /* Pairs with tcg_clear_temp_count. To be called by #TranslatorOps.{translate_insn,tb_stop} if diff --git a/exec.c b/exec.c index 3f5deb35ff..10267f7ed0 100644 --- a/exec.c +++ b/exec.c @@ -2752,6 +2752,13 @@ void cpu_check_watchpoint(CPUState *cpu, vaddr addr, vaddr len, QTAILQ_FOREACH(wp, &cpu->watchpoints, entry) { if (watchpoint_address_matches(wp, addr, len) && (wp->flags & flags)) { + if (replay_running_debug()) { + /* + * Don't process the watchpoints when we are + * in a reverse debugging operation. + */ + return; + } if (flags == BP_MEM_READ) { wp->flags |= BP_WATCHPOINT_HIT_READ; } else { diff --git a/gdbstub.c b/gdbstub.c index 9dfb6e4142..79e8ccc050 100644 --- a/gdbstub.c +++ b/gdbstub.c @@ -51,6 +51,7 @@ #include "sysemu/runstate.h" #include "hw/semihosting/semihost.h" #include "exec/exec-all.h" +#include "sysemu/replay.h" #ifdef CONFIG_USER_ONLY #define GDB_ATTACHED "0" @@ -375,6 +376,20 @@ typedef struct GDBState { */ static int sstep_flags = SSTEP_ENABLE|SSTEP_NOIRQ|SSTEP_NOTIMER; +/* Retrieves flags for single step mode. */ +static int get_sstep_flags(void) +{ + /* + * In replay mode all events written into the log should be replayed. + * That is why NOIRQ flag is removed in this mode. + */ + if (replay_mode != REPLAY_MODE_NONE) { + return SSTEP_ENABLE; + } else { + return sstep_flags; + } +} + static GDBState gdbserver_state; static void init_gdbserver_state(void) @@ -501,7 +516,7 @@ static int gdb_continue_partial(char *newstates) break; /* nothing to do here */ case 's': trace_gdbstub_op_stepping(cpu->cpu_index); - cpu_single_step(cpu, sstep_flags); + cpu_single_step(cpu, get_sstep_flags()); cpu_resume(cpu); flag = 1; break; @@ -1874,10 +1889,31 @@ static void handle_step(GdbCmdContext *gdb_ctx, void *user_ctx) gdb_set_cpu_pc((target_ulong)gdb_ctx->params[0].val_ull); } - cpu_single_step(gdbserver_state.c_cpu, sstep_flags); + cpu_single_step(gdbserver_state.c_cpu, get_sstep_flags()); gdb_continue(); } +static void handle_backward(GdbCmdContext *gdb_ctx, void *user_ctx) +{ + if (replay_mode != REPLAY_MODE_PLAY) { + put_packet("E22"); + } + if (gdb_ctx->num_params == 1) { + switch (gdb_ctx->params[0].opcode) { + case 's': + if (replay_reverse_step()) { + gdb_continue(); + } else { + put_packet("E14"); + } + return; + } + } + + /* Default invalid command */ + put_packet(""); +} + static void handle_v_cont_query(GdbCmdContext *gdb_ctx, void *user_ctx) { put_packet("vCont;c;C;s;S"); @@ -2124,6 +2160,10 @@ static void handle_query_supported(GdbCmdContext *gdb_ctx, void *user_ctx) g_string_append(gdbserver_state.str_buf, ";qXfer:features:read+"); } + if (replay_mode == REPLAY_MODE_PLAY) { + g_string_append(gdbserver_state.str_buf, ";ReverseStep+"); + } + if (gdb_ctx->num_params && strstr(gdb_ctx->params[0].data, "multiprocess+")) { gdbserver_state.multiprocess = true; @@ -2460,6 +2500,17 @@ static int gdb_handle_packet(const char *line_buf) cmd_parser = &step_cmd_desc; } break; + case 'b': + { + static const GdbCmdParseEntry backward_cmd_desc = { + .handler = handle_backward, + .cmd = "b", + .cmd_startswith = 1, + .schema = "o0" + }; + cmd_parser = &backward_cmd_desc; + } + break; case 'F': { static const GdbCmdParseEntry file_io_cmd_desc = { diff --git a/include/sysemu/replay.h b/include/sysemu/replay.h index 239c01e7df..13a8123b09 100644 --- a/include/sysemu/replay.h +++ b/include/sysemu/replay.h @@ -75,6 +75,17 @@ void replay_finish(void); void replay_add_blocker(Error *reason); /* Returns name of the replay log file */ const char *replay_get_filename(void); +/* + * Start making one step in backward direction. + * Used by gdbstub for backwards debugging. + * Returns true on success. + */ +bool replay_reverse_step(void); +/* + * Returns true if replay module is processing + * reverse_continue or reverse_step request + */ +bool replay_running_debug(void); /* Processing the instructions */ diff --git a/replay/replay-debugging.c b/replay/replay-debugging.c index e1fe6b8661..f7594a88cd 100644 --- a/replay/replay-debugging.c +++ b/replay/replay-debugging.c @@ -22,6 +22,13 @@ #include "block/snapshot.h" #include "migration/snapshot.h" +static bool replay_is_debugging; + +bool replay_running_debug(void) +{ + return replay_is_debugging; +} + void hmp_info_replay(Monitor *mon, const QDict *qdict) { if (replay_mode == REPLAY_MODE_NONE) { @@ -212,3 +219,29 @@ void hmp_replay_seek(Monitor *mon, const QDict *qdict) return; } } + +static void replay_stop_vm_debug(void *opaque) +{ + replay_is_debugging = false; + vm_stop(RUN_STATE_DEBUG); + replay_delete_break(); +} + +bool replay_reverse_step(void) +{ + Error *err = NULL; + + assert(replay_mode == REPLAY_MODE_PLAY); + + if (replay_get_current_icount() != 0) { + replay_seek(replay_get_current_icount() - 1, replay_stop_vm_debug, &err); + if (err) { + error_free(err); + return false; + } + replay_is_debugging = true; + return true; + } + + return false; +} diff --git a/softmmu/cpus.c b/softmmu/cpus.c index ac8940d52e..1fa9c4c1de 100644 --- a/softmmu/cpus.c +++ b/softmmu/cpus.c @@ -1004,9 +1004,17 @@ static bool cpu_can_run(CPUState *cpu) static void cpu_handle_guest_debug(CPUState *cpu) { - gdb_set_stop_cpu(cpu); - qemu_system_debug_request(); - cpu->stopped = true; + if (replay_running_debug()) { + if (!cpu->singlestep_enabled) { + cpu_single_step(cpu, SSTEP_ENABLE); + } else { + cpu_single_step(cpu, 0); + } + } else { + gdb_set_stop_cpu(cpu); + qemu_system_debug_request(); + cpu->stopped = true; + } } #ifdef CONFIG_LINUX diff --git a/stubs/replay.c b/stubs/replay.c index eacb366aa8..d5b52302e9 100644 --- a/stubs/replay.c +++ b/stubs/replay.c @@ -93,3 +93,8 @@ uint64_t replay_get_current_icount(void) { return 0; } + +bool replay_reverse_step(void) +{ + return false; +}