From owner-freebsd-hackers@FreeBSD.ORG Thu Dec 8 17:53:39 2011 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id C4902106564A; Thu, 8 Dec 2011 17:53:39 +0000 (UTC) (envelope-from nwhitehorn@freebsd.org) Received: from agogare.doit.wisc.edu (agogare.doit.wisc.edu [144.92.197.211]) by mx1.freebsd.org (Postfix) with ESMTP id 944268FC0C; Thu, 8 Dec 2011 17:53:39 +0000 (UTC) MIME-version: 1.0 Content-transfer-encoding: 7BIT Content-type: text/plain; CHARSET=US-ASCII; format=flowed Received: from avs-daemon.smtpauth2.wiscmail.wisc.edu by smtpauth2.wiscmail.wisc.edu (Sun Java(tm) System Messaging Server 7u2-7.05 32bit (built Jul 30 2009)) id <0LVW008189LEY900@smtpauth2.wiscmail.wisc.edu>; Thu, 08 Dec 2011 10:53:38 -0600 (CST) Received: from anacreon.physics.wisc.edu (anacreon.physics.wisc.edu [128.104.160.176]) by smtpauth2.wiscmail.wisc.edu (Sun Java(tm) System Messaging Server 7u2-7.05 32bit (built Jul 30 2009)) with ESMTPSA id <0LVW006RG9L9BI00@smtpauth2.wiscmail.wisc.edu>; Thu, 08 Dec 2011 10:53:33 -0600 (CST) Date: Thu, 08 Dec 2011 10:53:32 -0600 From: Nathan Whitehorn In-reply-to: <20111208090159.GA1924@cq1> To: Piotr Nowak Message-id: <4EE0EB8C.7050800@freebsd.org> X-Spam-Report: AuthenticatedSender=yes, SenderIP=128.104.160.176 X-Spam-PmxInfo: Server=avs-9, Version=5.6.1.2065439, Antispam-Engine: 2.7.2.376379, Antispam-Data: 2011.12.8.164215, SenderIP=128.104.160.176 References: <20111119100150.GA1560@reks> <20111208090159.GA1924@cq1> User-Agent: Mozilla/5.0 (X11; U; FreeBSD powerpc; en-US; rv:1.9.2.22) Gecko/20110913 Thunderbird/3.1.14 Cc: Rafal Jaworowski , Gleb Kurtsou , mdf@freebsd.org, Arnaud Lacombe , freebsd-hackers@freebsd.org Subject: Re: gcc 4.2 miscompilation with -O2 -fno-omit-frame-pointer on amd64 X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 08 Dec 2011 17:53:39 -0000 On 12/08/11 03:01, Piotr Nowak wrote: > We're working on PowerPC target using GCC 4.2.1 > and FreeBSD 6.1. It seems like we have similar > problem. In our case GCC sometimes very unfortunately > optimize code with -fno-omit-frame-pointer. > > Example shown below covers file sys/powerc/booke/pmap.c > and function pmap_kenter. If we disassemble kernel binary > we have: > > c019998c: 4b ec 6a ed bl c0060478<_mtx_unlock_spin_flags> > c0199990: 81 61 00 00 lwz r11,0(r1) > c0199994: 80 0b 00 04 lwz r0,4(r11) > c0199998: 7d 61 5b 78 mr r1,r11 > c019999c: 82 ab ff d4 lwz r21,-44(r11) > c01999a0: 7c 08 03 a6 mtlr r0 > c01999a4: 82 cb ff d8 lwz r22,-40(r11) > c01999a8: 82 eb ff dc lwz r23,-36(r11) > c01999ac: 83 0b ff e0 lwz r24,-32(r11) > c01999b0: 83 2b ff e4 lwz r25,-28(r11) > c01999b4: 83 4b ff e8 lwz r26,-24(r11) > c01999b8: 83 6b ff ec lwz r27,-20(r11) > > As you can see stack pointer on R1 is being updated > before stashed data were pulled off stack. (mr r1,r11) > As a result of this we have chance to get crash when > any interrupt hit shortly after stack pointer update. > The interrupt prologue will override not yet pulled off > pmap_kenter function data. > > The problem occures only with -fno-omit-frame-pointer > and not every branch returns are beeing corrupted. > > Do you think this issue may be somehow related to yours? > Are there any patches/solutions to fix it? Should we turn off -fno-omit-frame-frame-pointer on PPC then? It's enabled in default kernel builds. -Nathan