From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr1-f47.google.com (mail-wr1-f47.google.com [209.85.221.47]) by sourceware.org (Postfix) with ESMTPS id BAEFE3858CDA for ; Fri, 10 Mar 2023 17:15:08 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org BAEFE3858CDA Authentication-Results: sourceware.org; dmarc=none (p=none dis=none) header.from=palves.net Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=gmail.com Received: by mail-wr1-f47.google.com with SMTP id h11so5711637wrm.5 for ; Fri, 10 Mar 2023 09:15:08 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1678468507; h=content-transfer-encoding:content-language:in-reply-to:mime-version :user-agent:date:message-id:references:to:subject:from :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=Cbac4+Q+LNJ9ShM5R8FNFDW9RDZniPrpEuWglSaTgNU=; b=uMSSNhxTc4RPZFceC5JTSLO5MSZ2x7i4eTFUGHhvQkjP4bo33ZclQo+7RqwOppkugB BXSeqHqkihAlbuhOW3If+/y4sXd0r3gmJb62AV/kLTSWUiDu86GhaPdr3O1bbhji6HcA 3fZN/EIKQhrdTEVCMJeQzQoiPQmxyQ34utjjrLM+8SHKvrb8flnAYHzY9xUmg0DnnZbJ hgXga0P54eOlahFnNxdeX0mI5rgL5Sx5YtRnpcxHwsgyvvSXdNYMTk/+hrNCe/HyFXso u0LNXUKwclHJDHS/dABmEQZSCAE2BLRS+nGXJ1zpu8YbyUugbIQCD0imbi+eMx6J/kOQ cAcA== X-Gm-Message-State: AO0yUKXOahGoJjB9b6hDiYfeA2utSn+YyOkfns81yzok20t4fnR94Brp bPHJ9E1AntD3Eowqe1pUCXKwFTrwe5k= X-Google-Smtp-Source: AK7set/V2d5SWfIilHZqprOWhet7zC46CdwNLmfsyRIYfb0EiAUaAiHtYKjOWVEf39Ii3c17OUMM0g== X-Received: by 2002:adf:ff92:0:b0:2bf:dcbc:c442 with SMTP id j18-20020adfff92000000b002bfdcbcc442mr2243846wrr.24.1678468507124; Fri, 10 Mar 2023 09:15:07 -0800 (PST) Received: from ?IPv6:2001:8a0:f93c:5900::1fe? ([2001:8a0:f93c:5900::1fe]) by smtp.gmail.com with ESMTPSA id b12-20020adff90c000000b002c71d206329sm287881wrr.55.2023.03.10.09.15.06 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 10 Mar 2023 09:15:06 -0800 (PST) From: Pedro Alves Subject: Re: [PATCH 01/31] displaced step: pass down target_waitstatus instead of gdb_signal To: Andrew Burgess , gdb-patches@sourceware.org References: <20221212203101.1034916-1-pedro@palves.net> <20221212203101.1034916-2-pedro@palves.net> <87fsbnrpss.fsf@redhat.com> Message-ID: Date: Fri, 10 Mar 2023 17:15:00 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 MIME-Version: 1.0 In-Reply-To: <87fsbnrpss.fsf@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-11.0 required=5.0 tests=BAYES_00,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM,GIT_PATCH_0,HEADER_FROM_DIFFERENT_DOMAINS,KAM_DMARC_STATUS,NICE_REPLY_A,RCVD_IN_DNSWL_NONE,RCVD_IN_MSPIKE_H2,SPF_HELO_NONE,SPF_PASS,TXREP autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: On 2023-02-03 10:44 a.m., Andrew Burgess wrote: > Pedro Alves writes: > >> This commit tweaks displaced_step_finish & friends to pass down a >> target_waitstatus instead of a gdb_signal. This needed because a > > missing word: "This IS needed". Fixed. >> @@ -5699,7 +5696,7 @@ handle_inferior_event (struct execution_control_state *ecs) >> has been done. Perform cleanup for parent process here. Note >> that this operation also cleans up the child process for vfork, >> because their pages are shared. */ >> - displaced_step_finish (ecs->event_thread, GDB_SIGNAL_TRAP); >> + displaced_step_finish (ecs->event_thread, ecs->ws); > > This change is interesting. > > If I understand the code correctly, this call will eventually end up in > displaced_step_buffers::finish (displaced-stepping.c), which in turn > calls displaced_step_instruction_executed_successfully. > > Previously, we always passed GDB_SIGNAL_TRAP here, which (if we ignore > the watchpoint check in > displaced_step_instruction_executed_successfully) means that > displaced_step_instruction_executed_successfully would always return > true, and then displaced_step_buffers::finish would call > gdbarch_displaced_step_fixup. > > After this change, we know that esc->ws.kind is either > TARGET_WAITKIND_FORKED or TARGET_WAITKIND_VFORKED, so we know that > displaced_step_instruction_executed_successfully will always return > false, and displaced_step_buffers::finish will no longer call > gdbarch_displaced_step_fixup. > Good catch! I was tweaking the change to address your comment, and was coming to the conclusion that what I really wanted was this: static bool displaced_step_instruction_executed_successfully (gdbarch *arch, const target_waitstatus &status) { if (status.kind () == TARGET_WAITKIND_STOPPED && status.sig () != GDB_SIGNAL_TRAP) return false; /* All other waitkinds can only happen if the instruction fully executed. For example, a fork, or a syscall entry can only happen if the syscall instruction actually executed. */ (the comment is new) And then, I remembered, I actually wrote that early if like that originally, and I changed it in response to this review: https://inbox.sourceware.org/gdb-patches/44f74af8-248b-1af8-3612-980c08607bf4@simark.ca/ The review was totally right, it was my response that was misguided. But I'm confused because I am pretty sure that I wrote a reply to that message, saying that I did not intend to change the behavior, so I'd "fix" it. I can't find it in my outbox either, I guess I erroneously canceled my email window instead of sending the message... Anyhow, looks like I made it worse while trying to address Simon's comment. :-P So I think I should go back to what I had, like before, and my response to Simon should have been instead: - yes, the change is intended. If we stopped for an event other than TARGET_WAITKIND_STOPPED, like for instance, TARGET_WAITKIND_FORKED, TARGET_WAITKIND_SYSCALL_ENTRY, then it must be that the instruction executed successfully, otherwise the syscall wouldn't have triggered. > What I don't understand well enough is what this actually means for a > running inferior. > > It's odd because the comment in infrun.c (just above your change) > indicates that to get to this point the displaced step must have > completed successfully, while after this change, the new code path in > displaced_step_buffers::finish indicates we believe the displaced step > didn't complete successfully: > > /* Since the instruction didn't complete, all we can do is relocate the > PC. */ > > Do you know if any of our test cases hit this path? > I know that you posted a series for this, which I plan to take a good look at (I actually planned on doing that earlier this week, but I had a couple major distractions, sorry). WDYT of the version below? >From 0ccfd6822ef83eddb48c6f7bf21533858f177bc9 Mon Sep 17 00:00:00 2001 From: Pedro Alves Date: Tue, 22 Jun 2021 15:42:51 +0100 Subject: [PATCH] displaced step: pass down target_waitstatus instead of gdb_signal This commit tweaks displaced_step_finish & friends to pass down a target_waitstatus instead of a gdb_signal. This is needed because a patch later in the series will want to make displaced_step_buffers::finish handle TARGET_WAITKIND_THREAD_EXITED. It also helps with the TARGET_WAITKIND_THREAD_CLONED patch later in the series. Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=27338 Change-Id: I4c5d338647b028071bc498c4e47063795a2db4c0 --- gdb/displaced-stepping.c | 16 +++++++++++----- gdb/displaced-stepping.h | 2 +- gdb/gdbarch-gen.h | 4 ++-- gdb/gdbarch.c | 4 ++-- gdb/gdbarch_components.py | 2 +- gdb/infrun.c | 17 +++++++---------- gdb/linux-tdep.c | 5 +++-- gdb/linux-tdep.h | 2 +- gdb/rs6000-tdep.c | 4 ++-- 9 files changed, 30 insertions(+), 26 deletions(-) diff --git a/gdb/displaced-stepping.c b/gdb/displaced-stepping.c index 06b32a80f6a..08ae1ce4397 100644 --- a/gdb/displaced-stepping.c +++ b/gdb/displaced-stepping.c @@ -192,12 +192,18 @@ write_memory_ptid (ptid_t ptid, CORE_ADDR memaddr, } static bool -displaced_step_instruction_executed_successfully (gdbarch *arch, - gdb_signal signal) +displaced_step_instruction_executed_successfully + (gdbarch *arch, const target_waitstatus &status) { - if (signal != GDB_SIGNAL_TRAP) + if (status.kind () == TARGET_WAITKIND_STOPPED + && status.sig () != GDB_SIGNAL_TRAP) return false; + /* All other (thread event) waitkinds can only happen if the + instruction fully executed. For example, a fork, or a syscall + entry can only happen if the syscall instruction actually + executed. */ + if (target_stopped_by_watchpoint ()) { if (gdbarch_have_nonsteppable_watchpoint (arch) @@ -210,7 +216,7 @@ displaced_step_instruction_executed_successfully (gdbarch *arch, displaced_step_finish_status displaced_step_buffers::finish (gdbarch *arch, thread_info *thread, - gdb_signal sig) + const target_waitstatus &status) { gdb_assert (thread->displaced_step_state.in_progress ()); @@ -256,7 +262,7 @@ displaced_step_buffers::finish (gdbarch *arch, thread_info *thread, regcache *rc = get_thread_regcache (thread); bool instruction_executed_successfully - = displaced_step_instruction_executed_successfully (arch, sig); + = displaced_step_instruction_executed_successfully (arch, status); if (instruction_executed_successfully) { diff --git a/gdb/displaced-stepping.h b/gdb/displaced-stepping.h index e154927ad92..d2c3fc1b2b4 100644 --- a/gdb/displaced-stepping.h +++ b/gdb/displaced-stepping.h @@ -168,7 +168,7 @@ struct displaced_step_buffers CORE_ADDR &displaced_pc); displaced_step_finish_status finish (gdbarch *arch, thread_info *thread, - gdb_signal sig); + const target_waitstatus &status); const displaced_step_copy_insn_closure * copy_insn_closure_by_addr (CORE_ADDR addr); diff --git a/gdb/gdbarch-gen.h b/gdb/gdbarch-gen.h index ddb97f60315..5805dcb75ef 100644 --- a/gdb/gdbarch-gen.h +++ b/gdb/gdbarch-gen.h @@ -1103,8 +1103,8 @@ extern void set_gdbarch_displaced_step_prepare (struct gdbarch *gdbarch, gdbarch /* Clean up after a displaced step of THREAD. */ -typedef displaced_step_finish_status (gdbarch_displaced_step_finish_ftype) (struct gdbarch *gdbarch, thread_info *thread, gdb_signal sig); -extern displaced_step_finish_status gdbarch_displaced_step_finish (struct gdbarch *gdbarch, thread_info *thread, gdb_signal sig); +typedef displaced_step_finish_status (gdbarch_displaced_step_finish_ftype) (struct gdbarch *gdbarch, thread_info *thread, const target_waitstatus &ws); +extern displaced_step_finish_status gdbarch_displaced_step_finish (struct gdbarch *gdbarch, thread_info *thread, const target_waitstatus &ws); extern void set_gdbarch_displaced_step_finish (struct gdbarch *gdbarch, gdbarch_displaced_step_finish_ftype *displaced_step_finish); /* Return the closure associated to the displaced step buffer that is at ADDR. */ diff --git a/gdb/gdbarch.c b/gdb/gdbarch.c index 7e4e34d5aca..0b122a86055 100644 --- a/gdb/gdbarch.c +++ b/gdb/gdbarch.c @@ -4096,13 +4096,13 @@ set_gdbarch_displaced_step_prepare (struct gdbarch *gdbarch, } displaced_step_finish_status -gdbarch_displaced_step_finish (struct gdbarch *gdbarch, thread_info *thread, gdb_signal sig) +gdbarch_displaced_step_finish (struct gdbarch *gdbarch, thread_info *thread, const target_waitstatus &ws) { gdb_assert (gdbarch != NULL); gdb_assert (gdbarch->displaced_step_finish != NULL); if (gdbarch_debug >= 2) gdb_printf (gdb_stdlog, "gdbarch_displaced_step_finish called\n"); - return gdbarch->displaced_step_finish (gdbarch, thread, sig); + return gdbarch->displaced_step_finish (gdbarch, thread, ws); } void diff --git a/gdb/gdbarch_components.py b/gdb/gdbarch_components.py index caa65c334ec..8d72bff347e 100644 --- a/gdb/gdbarch_components.py +++ b/gdb/gdbarch_components.py @@ -1878,7 +1878,7 @@ Clean up after a displaced step of THREAD. """, type="displaced_step_finish_status", name="displaced_step_finish", - params=[("thread_info *", "thread"), ("gdb_signal", "sig")], + params=[("thread_info *", "thread"), ("const target_waitstatus &", "ws")], predefault="NULL", invalid="(! gdbarch->displaced_step_finish) != (! gdbarch->displaced_step_prepare)", ) diff --git a/gdb/infrun.c b/gdb/infrun.c index ab77300f1ff..99f2a8e039d 100644 --- a/gdb/infrun.c +++ b/gdb/infrun.c @@ -1895,7 +1895,8 @@ displaced_step_prepare (thread_info *thread) DISPLACED_STEP_FINISH_STATUS_OK as well. */ static displaced_step_finish_status -displaced_step_finish (thread_info *event_thread, enum gdb_signal signal) +displaced_step_finish (thread_info *event_thread, + const target_waitstatus &event_status) { displaced_step_thread_state *displaced = &event_thread->displaced_step_state; @@ -1917,7 +1918,7 @@ displaced_step_finish (thread_info *event_thread, enum gdb_signal signal) /* Do the fixup, and release the resources acquired to do the displaced step. */ return gdbarch_displaced_step_finish (displaced->get_original_gdbarch (), - event_thread, signal); + event_thread, event_status); } /* Data to be passed around while handling an event. This data is @@ -5122,7 +5123,7 @@ handle_one (const wait_one_event &event) /* We caught the event that we intended to catch, so there's no event to save as pending. */ - if (displaced_step_finish (t, GDB_SIGNAL_0) + if (displaced_step_finish (t, event.ws) == DISPLACED_STEP_FINISH_STATUS_NOT_EXECUTED) { /* Add it back to the step-over queue. */ @@ -5137,7 +5138,6 @@ handle_one (const wait_one_event &event) } else { - enum gdb_signal sig; struct regcache *regcache; infrun_debug_printf @@ -5148,10 +5148,7 @@ handle_one (const wait_one_event &event) /* Record for later. */ save_waitstatus (t, event.ws); - sig = (event.ws.kind () == TARGET_WAITKIND_STOPPED - ? event.ws.sig () : GDB_SIGNAL_0); - - if (displaced_step_finish (t, sig) + if (displaced_step_finish (t, event.ws) == DISPLACED_STEP_FINISH_STATUS_NOT_EXECUTED) { /* Add it back to the step-over queue. */ @@ -5753,7 +5750,7 @@ handle_inferior_event (struct execution_control_state *ecs) has been done. Perform cleanup for parent process here. Note that this operation also cleans up the child process for vfork, because their pages are shared. */ - displaced_step_finish (ecs->event_thread, GDB_SIGNAL_TRAP); + displaced_step_finish (ecs->event_thread, ecs->ws); /* Start a new step-over in another thread if there's one that needs it. */ start_step_over (); @@ -6118,7 +6115,7 @@ resumed_thread_with_pending_status (struct thread_info *tp, static int finish_step_over (struct execution_control_state *ecs) { - displaced_step_finish (ecs->event_thread, ecs->event_thread->stop_signal ()); + displaced_step_finish (ecs->event_thread, ecs->ws); bool had_step_over_info = step_over_info_valid_p (); diff --git a/gdb/linux-tdep.c b/gdb/linux-tdep.c index e6ce13a1c67..036ea9f931d 100644 --- a/gdb/linux-tdep.c +++ b/gdb/linux-tdep.c @@ -2621,13 +2621,14 @@ linux_displaced_step_prepare (gdbarch *arch, thread_info *thread, /* See linux-tdep.h. */ displaced_step_finish_status -linux_displaced_step_finish (gdbarch *arch, thread_info *thread, gdb_signal sig) +linux_displaced_step_finish (gdbarch *arch, thread_info *thread, + const target_waitstatus &status) { linux_info *per_inferior = get_linux_inferior_data (thread->inf); gdb_assert (per_inferior->disp_step_bufs.has_value ()); - return per_inferior->disp_step_bufs->finish (arch, thread, sig); + return per_inferior->disp_step_bufs->finish (arch, thread, status); } /* See linux-tdep.h. */ diff --git a/gdb/linux-tdep.h b/gdb/linux-tdep.h index 16e1b806b26..e09a6ef32b1 100644 --- a/gdb/linux-tdep.h +++ b/gdb/linux-tdep.h @@ -72,7 +72,7 @@ extern displaced_step_prepare_status linux_displaced_step_prepare /* Implementation of gdbarch_displaced_step_finish. */ extern displaced_step_finish_status linux_displaced_step_finish - (gdbarch *arch, thread_info *thread, gdb_signal sig); + (gdbarch *arch, thread_info *thread, const target_waitstatus &status); /* Implementation of gdbarch_displaced_step_copy_insn_closure_by_addr. */ diff --git a/gdb/rs6000-tdep.c b/gdb/rs6000-tdep.c index 104515de030..f9bbc435184 100644 --- a/gdb/rs6000-tdep.c +++ b/gdb/rs6000-tdep.c @@ -1088,13 +1088,13 @@ ppc_displaced_step_prepare (gdbarch *arch, thread_info *thread, static displaced_step_finish_status ppc_displaced_step_finish (gdbarch *arch, thread_info *thread, - gdb_signal sig) + const target_waitstatus &status) { ppc_inferior_data *per_inferior = get_ppc_per_inferior (thread->inf); gdb_assert (per_inferior->disp_step_buf.has_value ()); - return per_inferior->disp_step_buf->finish (arch, thread, sig); + return per_inferior->disp_step_buf->finish (arch, thread, status); } /* Implementation of gdbarch_displaced_step_restore_all_in_ptid. */ base-commit: 2562954ede66f32bff7d985e752b8052c2ae5775 -- 2.36.0