From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from simark.ca (simark.ca [158.69.221.121]) by sourceware.org (Postfix) with ESMTPS id ADC93385700A for ; Tue, 25 Oct 2022 13:59:59 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org ADC93385700A Authentication-Results: sourceware.org; dmarc=pass (p=none dis=none) header.from=simark.ca Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=simark.ca Received: from [10.0.0.85] (modemcable162.249-56-74.mc.videotron.ca [74.56.249.162]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by simark.ca (Postfix) with ESMTPSA id 5A7571E0D3; Tue, 25 Oct 2022 09:59:59 -0400 (EDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=simark.ca; s=mail; t=1666706399; bh=UZs42ShSytuX5VbCiJljIE3GtCCs0UtpnY7hWn2wLqA=; h=Date:Subject:From:To:References:In-Reply-To:From; b=JPjZms+bjVNFROoivZwMR13B7SC0HblXDnXhnKf9vmpCNobUBH6pxYWzhbTJ+w1SB 9qHBe/xfGj5n0AP3+KBQLJDjL13JOLPN8Qhdc76LiVv3sjObRgMeenhnl8nsZYzulM FG1i3342E+kCZZLjNkN+NF62TcXguLPCh9wDyaH8= Message-ID: <6975b747-e4fd-ca3c-1b89-d65b51d44d1f@simark.ca> Date: Tue, 25 Oct 2022 09:59:59 -0400 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.3.2 Subject: Re: [PATCH v4 1/2] Change calculation of frame_id by amd64 epilogue unwinder Content-Language: fr From: Simon Marchi To: Bruno Larsen , gdb-patches@sourceware.org References: <20221005103832.3163424-1-blarsen@redhat.com> <20221005103832.3163424-2-blarsen@redhat.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-10.9 required=5.0 tests=BAYES_00,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,GIT_PATCH_0,NICE_REPLY_A,SPF_HELO_PASS,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 10/25/22 09:44, Simon Marchi wrote: > On 10/5/22 06:38, Bruno Larsen via Gdb-patches wrote: >> When GDB is stopped at a ret instruction and no debug information is >> available for unwinding, GDB defaults to the amd64 epilogue unwinder, to >> be able to generate a decent backtrace. However, when calculating the >> frame id, the epilogue unwinder generates information as if the return >> instruction was the whole frame. >> >> This was an issue especially when attempting to reverse debug, as GDB >> would place a step_resume_breakpoint from the epilogue of a function if >> we were to attempt to skip that function, and this breakpoint should >> ideally have the current function's frame_id to avoid other problems >> such as PR record/16678. >> >> This commit changes the frame_id calculation for the amd64 epilogue, >> so that it is always the same as the dwarf2 unwinder's frame_id. >> >> It also adds a test to confirm that the frame_id will be the same, >> regardless of using the epilogue unwinder or not, thanks to Andrew >> Burgess. >> >> Co-Authored-By: Andrew Burgess >> --- >> gdb/amd64-tdep.c | 10 +- >> .../gdb.base/unwind-on-each-insn-foo.c | 22 +++ >> gdb/testsuite/gdb.base/unwind-on-each-insn.c | 25 +++ >> .../gdb.base/unwind-on-each-insn.exp | 154 ++++++++++++++++++/usr/lib/x86_64-linux-gnu/libasan.so.6 >> 4 files changed, 206 insertions(+), 5 deletions(-) >> create mode 100644 gdb/testsuite/gdb.base/unwind-on-each-insn-foo.c >> create mode 100644 gdb/testsuite/gdb.base/unwind-on-each-insn.c >> create mode 100644 gdb/testsuite/gdb.base/unwind-on-each-insn.exp > > Hi Bruno, > > On Ubuntu 22.04, I can get this new test to fail quite reliably with: > > $ taskset -c 1 make check TESTS="gdb.base/unwind-on-each-insn.exp" RUNTESTFLAGS="--target_board=native-gdbserver" > > Can you give it a try? > > Simon Actually, I took the time to look into it, it turns out the problem is simple. Here's a patch below. >From 7090bf701b2f1cca89985ea1b45b0a2e3859e19e Mon Sep 17 00:00:00 2001 From: Simon Marchi Date: Tue, 25 Oct 2022 09:50:56 -0400 Subject: [PATCH] gdb/testsuite: make sure to consume the prompt in gdb.base/unwind-on-each-insn.exp This test fails quite reliably for me when ran as: $ taskset -c 1 make check TESTS="gdb.base/unwind-on-each-insn.exp" RUNTESTFLAGS="--target_board=native-gdbserver" or more simply: $ make check-read1 TESTS="gdb.base/unwind-on-each-insn.exp" The problem is that the that grabs the frame id from "maint print frame-id" does not consume the prompt. Well, it does sometimes due to the trailing .*, but not always. If the prompt is not consumed, the following tests get confused: FAIL: gdb.base/unwind-on-each-insn.exp: gdb_breakpoint: set breakpoint at *foo FAIL: gdb.base/unwind-on-each-insn.exp: disassemble foo FAIL: gdb.base/unwind-on-each-insn.exp: get $sp and frame base in foo: get hexadecimal valueof "$sp" Use -wrap to make gdb_test_multiple consume the prompt. While at it, remove the bit that consumes the command name and do exp_continue, it's not really necessary. And for consistency, do the same changes to the gdb_test_multiple that consumes the stack address, although that one was fine, it did consume the prompt explicitly. Change-Id: I2b7328c8844c7e98921ea494c4c05107162619fc --- gdb/testsuite/gdb.base/unwind-on-each-insn.exp | 12 ++---------- 1 file changed, 2 insertions(+), 10 deletions(-) diff --git a/gdb/testsuite/gdb.base/unwind-on-each-insn.exp b/gdb/testsuite/gdb.base/unwind-on-each-insn.exp index faa6a1a3f064..3b48805cff83 100644 --- a/gdb/testsuite/gdb.base/unwind-on-each-insn.exp +++ b/gdb/testsuite/gdb.base/unwind-on-each-insn.exp @@ -44,11 +44,7 @@ proc get_sp_and_fba { testname } { set fba "" gdb_test_multiple "info frame" "" { - -re "^info frame\r\n" { - exp_continue - } - - -re "^Stack level ${::decimal}, frame at ($::hex):\r\n.*$::gdb_prompt $" { + -re -wrap ".*Stack level ${::decimal}, frame at ($::hex):.*" { set fba $expect_out(1,string) } } @@ -62,11 +58,7 @@ proc get_sp_and_fba { testname } { proc get_fid { } { set fid "" gdb_test_multiple "maint print frame-id" "" { - -re "^maint print frame-id\r\n" { - exp_continue - } - - -re "^frame-id for frame #${::decimal}: (\[^\r\n\]+).*" { + -re -wrap ".*frame-id for frame #${::decimal}: (.*)" { set fid $expect_out(1,string) } } -- 2.38.0