From patchwork Wed Sep 12 08:19:22 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Pavel Dovgalyuk X-Patchwork-Id: 10597093 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 F29B114DB for ; Wed, 12 Sep 2018 08:37:17 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id DF9E52968F for ; Wed, 12 Sep 2018 08:37:17 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id D254329993; Wed, 12 Sep 2018 08:37:17 +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 2E84D2968F for ; Wed, 12 Sep 2018 08:37:17 +0000 (UTC) Received: from localhost ([::1]:35131 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1g00eC-0007ZQ-1o for patchwork-qemu-devel@patchwork.kernel.org; Wed, 12 Sep 2018 04:37:16 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:47509) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1g00Mz-0001FG-Lm for qemu-devel@nongnu.org; Wed, 12 Sep 2018 04:19:30 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1g00Mv-0000fN-Ny for qemu-devel@nongnu.org; Wed, 12 Sep 2018 04:19:29 -0400 Received: from mail.ispras.ru ([83.149.199.45]:56032) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1g00Mv-0000eE-9f for qemu-devel@nongnu.org; Wed, 12 Sep 2018 04:19:25 -0400 Received: from [127.0.1.1] (unknown [85.142.117.226]) by mail.ispras.ru (Postfix) with ESMTPSA id 476CF5400AD; Wed, 12 Sep 2018 11:19:23 +0300 (MSK) From: Pavel Dovgalyuk To: qemu-devel@nongnu.org Date: Wed, 12 Sep 2018 11:19:22 +0300 Message-ID: <20180912081922.3228.36913.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 16/25] gdbstub: add reverse step 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 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 --- accel/tcg/translator.c | 1 + cpus.c | 14 +++++++++++--- exec.c | 5 +++++ gdbstub.c | 42 +++++++++++++++++++++++++++++++++++++++--- include/sysemu/replay.h | 7 +++++++ replay/replay-debugging.c | 33 +++++++++++++++++++++++++++++++++ stubs/replay.c | 5 +++++ 7 files changed, 101 insertions(+), 6 deletions(-) diff --git a/accel/tcg/translator.c b/accel/tcg/translator.c index afd0a49..33a543e 100644 --- a/accel/tcg/translator.c +++ b/accel/tcg/translator.c @@ -17,6 +17,7 @@ #include "exec/gen-icount.h" #include "exec/log.h" #include "exec/translator.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 0ce5640..09248dd 100644 --- a/cpus.c +++ b/cpus.c @@ -1084,9 +1084,17 @@ 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 6826c83..eedddba 100644 --- a/exec.c +++ b/exec.c @@ -2738,6 +2738,11 @@ static void check_watchpoint(int offset, int len, MemTxAttrs attrs, int flags) QTAILQ_FOREACH(wp, &cpu->watchpoints, entry) { if (cpu_watchpoint_address_matches(wp, vaddr, 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 d6ab950..fa108f4 100644 --- a/gdbstub.c +++ b/gdbstub.c @@ -39,6 +39,7 @@ #include "sysemu/kvm.h" #include "exec/semihost.h" #include "exec/exec-all.h" +#include "sysemu/replay.h" #ifdef CONFIG_USER_ONLY #define GDB_ATTACHED "0" @@ -334,6 +335,19 @@ 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; bool gdb_has_xml; @@ -424,7 +438,7 @@ static int gdb_continue_partial(GDBState *s, char *newstates) CPU_FOREACH(cpu) { if (newstates[cpu->cpu_index] == 's') { trace_gdbstub_op_stepping(cpu->cpu_index); - cpu_single_step(cpu, sstep_flags); + cpu_single_step(cpu, get_sstep_flags()); } } s->running_state = 1; @@ -443,7 +457,7 @@ static int gdb_continue_partial(GDBState *s, 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; @@ -1082,9 +1096,28 @@ static int gdb_handle_packet(GDBState *s, const char *line_buf) addr = strtoull(p, (char **)&p, 16); gdb_set_cpu_pc(s, addr); } - cpu_single_step(s->c_cpu, sstep_flags); + cpu_single_step(s->c_cpu, get_sstep_flags()); gdb_continue(s); return RS_IDLE; + case 'b': + /* Backward debugging commands */ + if (replay_mode == REPLAY_MODE_PLAY) { + switch (*p) { + case 's': + if (replay_reverse_step()) { + gdb_continue(s); + return RS_IDLE; + } else { + put_packet(s, "E14"); + break; + } + default: + goto unknown_command; + } + } else { + put_packet(s, "E22"); + } + goto unknown_command; case 'F': { target_ulong ret; @@ -1347,6 +1380,9 @@ static int gdb_handle_packet(GDBState *s, const char *line_buf) if (cc->gdb_core_xml_file != NULL) { pstrcat(buf, sizeof(buf), ";qXfer:features:read+"); } + if (replay_mode == REPLAY_MODE_PLAY) { + pstrcat(buf, sizeof(buf), ";ReverseStep+"); + } put_packet(s, buf); break; } diff --git a/include/sysemu/replay.h b/include/sysemu/replay.h index 7a4890d..55a272a 100644 --- a/include/sysemu/replay.h +++ b/include/sysemu/replay.h @@ -76,6 +76,13 @@ const char *replay_get_filename(void); /*! Sets breakpoint at the specified step. If step = -1LL the existing breakpoint is removed. */ void replay_break(int64_t step, QEMUTimerCB callback, void *opaque); +/*! 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 e605ee0..a49d91e 100644 --- a/replay/replay-debugging.c +++ b/replay/replay-debugging.c @@ -21,6 +21,13 @@ #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) { @@ -183,3 +190,29 @@ 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_break(-1LL, NULL, NULL); +} + +bool replay_reverse_step(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_stop_vm_debug); + 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 4ac6078..521552f 100644 --- a/stubs/replay.c +++ b/stubs/replay.c @@ -80,3 +80,8 @@ void replay_mutex_lock(void) void replay_mutex_unlock(void) { } + +bool replay_reverse_step(void) +{ + return false; +}