From patchwork Fri Jun 26 10:20:37 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Pavel Dovgalyuk X-Patchwork-Id: 11627633 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 0ADAE913 for ; Fri, 26 Jun 2020 13:46:05 +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 DE7F7207D8 for ; Fri, 26 Jun 2020 13:46:04 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DE7F7207D8 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]:40716 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1joog8-0002ry-42 for patchwork-qemu-devel@patchwork.kernel.org; Fri, 26 Jun 2020 09:46:04 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:38424) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jolTN-0000N2-2d for qemu-devel@nongnu.org; Fri, 26 Jun 2020 06:20:41 -0400 Received: from mail.ispras.ru ([83.149.199.84]:59494) by eggs.gnu.org with esmtps (TLS1.2:DHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jolTL-0000RQ-1A for qemu-devel@nongnu.org; Fri, 26 Jun 2020 06:20:40 -0400 Received: from [127.0.1.1] (unknown [62.118.151.149]) by mail.ispras.ru (Postfix) with ESMTPSA id 4E7EC4089F08; Fri, 26 Jun 2020 10:20:37 +0000 (UTC) Subject: [PATCH 10/13] gdbstub: add reverse step support in replay mode From: Pavel Dovgalyuk To: qemu-devel@nongnu.org Date: Fri, 26 Jun 2020 13:20:37 +0300 Message-ID: <159316683702.10508.7973844299019522260.stgit@pasha-ThinkPad-X280> In-Reply-To: <159316678008.10508.6615172353109944370.stgit@pasha-ThinkPad-X280> References: <159316678008.10508.6615172353109944370.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 = 2020/06/26 06:19:41 X-ACL-Warn: Detected OS = Linux 3.11 and newer 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=_AUTOLEARN X-Spam_action: no action X-Mailman-Approved-At: Fri, 26 Jun 2020 09:41:37 -0400 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 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 --- 0 files changed 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/cpus.c b/cpus.c index 41d1c5099f..35381ea941 100644 --- a/cpus.c +++ b/cpus.c @@ -1100,9 +1100,17 @@ 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()) { + gdb_set_stop_cpu(cpu); + qemu_system_debug_request(); + cpu->stopped = true; + } else { + if (!cpu->singlestep_enabled) { + cpu_single_step(cpu, SSTEP_ENABLE); + } else { + cpu_single_step(cpu, 0); + } + } } #ifdef CONFIG_LINUX diff --git a/exec.c b/exec.c index d6712fba7e..4bde79ea3b 100644 --- a/exec.c +++ b/exec.c @@ -2720,6 +2720,13 @@ 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 6950fd243f..a81b3b5fb8 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 cfd0221692..aa3ca040e2 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) { @@ -219,3 +226,29 @@ 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/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; +}