From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 33301C77B71 for ; Sun, 16 Apr 2023 01:50:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229720AbjDPBuj (ORCPT ); Sat, 15 Apr 2023 21:50:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39568 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229462AbjDPBuj (ORCPT ); Sat, 15 Apr 2023 21:50:39 -0400 Received: from mail-pl1-x634.google.com (mail-pl1-x634.google.com [IPv6:2607:f8b0:4864:20::634]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C2A3426AA for ; Sat, 15 Apr 2023 18:50:36 -0700 (PDT) Received: by mail-pl1-x634.google.com with SMTP id kh6so20670167plb.0 for ; Sat, 15 Apr 2023 18:50:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20221208; t=1681609836; x=1684201836; h=content-transfer-encoding:in-reply-to:mime-version:user-agent:date :message-id:from:references:to:subject:from:to:cc:subject:date :message-id:reply-to; bh=MfQruGuTktcF0O700FviyelL+2PT0e6zLn+5QxJc614=; b=bdW41sjwdjCK8JF2jd5yJMU+zH4hqrStaLoTJ+5Xxguo37OOCBQhj1JB9YsRxwuMpJ WVDaZXWyCnAtGdGiXhU269EOfyNgHEoPiiTghOjuIwqdZdh9H7K5HRNeAPmJzkhtd/+i WX3tt+oHLdqHCTuXr0FVid0nZme+PdNZc7IFLS623L9rs+rpi3oelkSx1e8U/Ljs30fd Eaz+t1MlBZ/hV6jkIx1rF3euNm+jqU7eu/EDU2qBSTrXaZIiifkTaANuArxuJhizZkLG d1E2FajkBx+OvefbRErUZ5Nov7B0mHjH9fr7Bttf0cTAjgBJZQgfvkihg6JF6HN7NtdE NQxA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1681609836; x=1684201836; h=content-transfer-encoding:in-reply-to:mime-version:user-agent:date :message-id:from:references:to:subject:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=MfQruGuTktcF0O700FviyelL+2PT0e6zLn+5QxJc614=; b=TvFNy14DzL9MqDRqRIjArHAiW7qPtILPMOrp/oEyxHJ5nRJR7Z3zTpJ/kSJDkAS0HC T6ZrXJA+o421BEdpuyLATObCT9LeCIifPJMs8ABqnbUgqspXwRMScIxpDyGNtaTAy6gH e7FMsLvRaUGq+DVy2wMH/jfyViOPWuiQp40ITyjMV5HSWHdWRiSEenJaCdnGMEWnl/oH 1TAaWt5I8ke0MLqEsohTJk65jdyxezLzxV2A+3FKQi0MMsfUqLHQv9VRvS1+olyOgkXn Jj7C6UHL6XOBm3nzX6+zapyP7QyYjvnNWDhMfoR2qATjQO1yxlSXQY2dhFWSt66H8kFv A2Qw== X-Gm-Message-State: AAQBX9emq3KVWweOxXPM2vwyYW0n6oyJQwryfvebPIxRf0h7j0ieTYsL RbaPlPnZkT9Xnjz6oMw3s09L3Giw5K4= X-Google-Smtp-Source: AKy350aVfnQMihOWVoNrWVOEm2IXgx30lh/3eXK3X4jd4NFyCbd0MCsZntmYMVyjnZuEs9oolPsYPg== X-Received: by 2002:a17:902:e391:b0:1a4:f295:32fa with SMTP id g17-20020a170902e39100b001a4f29532famr7233966ple.15.1681609835639; Sat, 15 Apr 2023 18:50:35 -0700 (PDT) Received: from [10.1.1.24] (222-154-151-112-fibre.sparkbb.co.nz. [222.154.151.112]) by smtp.gmail.com with ESMTPSA id c3-20020a170902724300b0019cad2de86bsm5170829pll.156.2023.04.15.18.50.32 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Sat, 15 Apr 2023 18:50:35 -0700 (PDT) Subject: Re: core dump analysis, was Re: stack smashing detected To: Finn Thain , debian-68k@lists.debian.org, linux-m68k@lists.linux-m68k.org References: <4a9c1d0d-07aa-792e-921f-237d5a30fc44.ref@yahoo.com> <37da2ca2-dd99-8417-7cae-a88e2e7fc1b6@yahoo.com> <30a1be59-a1fd-f882-1072-c7db8734b1f1@gmail.com> <39f79c2d-e803-d7b1-078f-8757ca9b1238@yahoo.com> <040ad66a-71dd-001b-0446-36cbd6547b37@yahoo.com> <5b9d64bb-2adc-20a2-f596-f99bf255b5cc@linux-m68k.org> <56bd9a33-c58a-58e0-3956-e63c61abe5fe@yahoo.com> <1725f7c1-2084-a404-653d-9e9f8bbe961c@linux-m68k.org> <19d1f2ac-67dd-5415-b64a-1e1b4451f01e@linux-m68k.org> <87zg7rap45.fsf@igel.home> <5a5588ca-81c3-3f4c-fd43-c95e90b27939@linux-m68k.org> <67f6bc5f-e1fc-64b9-cb3c-1698cf4daf51@gmail.com> <9eea635f-c947-eae7-09fa-d39f00d91532@linux-m68k.org> <3dfea52a-b09e-517a-c3ca-4b559a3d9ce4@gmail.com> <23ddfd2a-1123-45ae-866d-158d45e23ba2@linux-m68k.org> <2f241963-44cd-3196-b39e-9c2d63cda1d3@linux-m68k.org> From: Michael Schmitz Message-ID: <60109ace-4e55-29da-86d9-35e931b11134@gmail.com> Date: Sun, 16 Apr 2023 13:50:29 +1200 User-Agent: Mozilla/5.0 (X11; Linux ppc; rv:45.0) Gecko/20100101 Icedove/45.4.0 MIME-Version: 1.0 In-Reply-To: <2f241963-44cd-3196-b39e-9c2d63cda1d3@linux-m68k.org> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-m68k@vger.kernel.org Hi Finn, Am 14.04.2023 um 21:30 schrieb Finn Thain: > Would signal delivery erase any of the memory immediately below the USP? > If so, it would erase those old stack frames, which would give some > indication of the timing of signal delivery. The signal stack is set up immediately below USP, from my reading of signal.c:setup_frame(). Old stack frames will be overwritten. > > If I run dash under gdb under QEMU, I can break on entry to onsig() and > find the signal frame on the stack. But when I examine stack memory from > the core dump, I can't find 0x70774e40 (i.e. moveq __NR_sigreturn,%d0 ; > trap #0) which the kernel puts on the stack in my QEMU experiments. As I understand this, the call to sys_sigreturn() removes both this code (signal trampoline IIRC) and the signal stack. At that point, the kernel signal handler (which in turn calls onsig()) has already been run. Again as far as I understand, the core dump happens on process exit. Stack smashing is detected and process exit is forced only at exit from __wait3() or __wait4_time64(), and those would have only been woken by receiving a signal. Both signal delivery and removal of signal stack by sys_sigreturn() must have happened before return from the wait syscalls. Cheers, Michael > That suggests that no signal was delivered... and yet gotsigchld == 1 at > the time of the coredump, after having been initialized by waitproc() > prior to calling __wait3(). So the signal handler onsig() must have > executed during __wait3() or __wait4_time64(). I can't explain this.