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 X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 63FAEC2D0DB for ; Mon, 20 Jan 2020 15:36:25 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 387A221D7E for ; Mon, 20 Jan 2020 15:36:25 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 387A221D7E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linaro.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:38762 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1itZ6G-0000yA-FE for qemu-devel@archiver.kernel.org; Mon, 20 Jan 2020 10:36:24 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:50950) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1itZ5X-0000Eh-Iy for qemu-devel@nongnu.org; Mon, 20 Jan 2020 10:35:43 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1itZ5T-0001KT-R4 for qemu-devel@nongnu.org; Mon, 20 Jan 2020 10:35:39 -0500 Received: from indium.canonical.com ([91.189.90.7]:46226) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1itZ5T-0001Jo-L3 for qemu-devel@nongnu.org; Mon, 20 Jan 2020 10:35:35 -0500 Received: from loganberry.canonical.com ([91.189.90.37]) by indium.canonical.com with esmtp (Exim 4.86_2 #2 (Debian)) id 1itZ5R-00077e-SX for ; Mon, 20 Jan 2020 15:35:33 +0000 Received: from loganberry.canonical.com (localhost [127.0.0.1]) by loganberry.canonical.com (Postfix) with ESMTP id D55B02E80CD for ; Mon, 20 Jan 2020 15:35:33 +0000 (UTC) MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Date: Mon, 20 Jan 2020 15:26:28 -0000 From: Peter Maydell To: qemu-devel@nongnu.org X-Launchpad-Notification-Type: bug X-Launchpad-Bug: product=qemu; status=New; importance=Undecided; assignee=None; X-Launchpad-Bug-Tags: arm gcc9.2 segfault X-Launchpad-Bug-Information-Type: Public X-Launchpad-Bug-Private: no X-Launchpad-Bug-Security-Vulnerability: no X-Launchpad-Bug-Commenters: fgodeh pmaydell X-Launchpad-Bug-Reporter: Fabian Godehardt (fgodeh) X-Launchpad-Bug-Modifier: Peter Maydell (pmaydell) References: <157666594314.15384.3778802807711797985.malonedeb@wampee.canonical.com> Message-Id: <157953398861.24612.16671820632562065829.malone@chaenomeles.canonical.com> Subject: [Bug 1856837] Re: qemu 4.2.0 arm segmentation fault with gcc 9.2 X-Launchpad-Message-Rationale: Subscriber (QEMU) @qemu-devel-ml X-Launchpad-Message-For: qemu-devel-ml Precedence: bulk X-Generated-By: Launchpad (canonical.com); Revision="f1052173880d8dae43faa7c2fc45da1b42227143"; Instance="production-secrets-lazr.conf" X-Launchpad-Hash: 1783b07db55f9fcb9987db49b9190eb4124d351f X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 91.189.90.7 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Bug 1856837 <1856837@bugs.launchpad.net> Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" At the point of the segfault, QEMU is correctly delivering a segfault to the guest because it has attempted to dereference a NULL pointer. You can see this if you run QEMU with the '-g 1234' option and connect an arm-aware gdb to it: (gdb) disas $pc-32,$pc+32 Dump of assembler code from 0x2bf24c to 0x2bf28c: 0x002bf24c: ldr r4, [r0, #296] ; 0x128 0x002bf250: mov r6, r1 0x002bf254: add r8, r0, #40 ; 0x28 0x002bf258: mov r5, #0 0x002bf25c: b 0x2bf268 0x002bf260: cmp r5, r6 0x002bf264: bge 0x2bf2d4 0x002bf268: mov r12, r4 =3D> 0x002bf26c: ldr r4, [r4] 0x002bf270: ldr r3, [r12, #12] 0x002bf274: tst r3, #512 ; 0x200 0x002bf278: bne 0x2bf2c0 0x002bf27c: tst r3, #1024 ; 0x400 0x002bf280: ubfx r1, r3, #11, #1 0x002bf284: bne 0x2bf2c0 0x002bf288: tst r3, #2048 ; 0x800 End of assembler dump. (gdb) print /x $r4 $3 =3D 0x0 It looks like this is in the middle of somebody's garbage collector (the elf symbol is _ZN2v88internal10PagedSpace14AdvanceSweeperEi). The next step would be to find out what was going on in the run-up to that that resulted in the NULL pointer. That's a bit of guest-level debugging work that would be much easier with the source code. If you can debug where something unexpected happens to the guest that would probably help -- this is likely to be a much longer piece of debugging than I'm afraid I have time to do. -- = You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1856837 Title: qemu 4.2.0 arm segmentation fault with gcc 9.2 Status in QEMU: New Bug description: As discussed with f4bug yesterday on IRC here comes the bug description. I'm building/configured qemu-4.2.0 on an x86_64 (gcc (Debian 6.3.0-18+deb9u1) 6.3.0 20170516) with target-list "arm-softmmu,arm- linux-user" and debug enabled. I use the arm-linux-user variant, "qemu-arm". Then i'm trying to cross-compile (arm gcc) an old version of googles v8 (as i need this version of the lib for binary compatibility) which uses qemu during build. It worked with gcc 5.4.0 but not with 9.2.0. I also tried with 6.5.0, 7.4.0 and 8.3.0 but those are also causing the same segmentation fault. The executed command wich breaks qemu is: qemu-arm /tmp/build/out/arm.release/mksnapshot.arm --log-snapshot- positions --logfile /tmp/build/out/arm.release/obj.host/v8_snapshot/geni/snapshot.log --random-seed 314159265 /tmp/build/out/arm.release/obj.host/v8_snap The printed error message is: ARMv7=3D1 VFP3=3D1 VFP32DREGS=3D1 NEON=3D0 SUDIV=3D0 UNALIGNED_ACCESSES= =3D1 MOVW_MOVT_IMMEDIATE_LOADS=3D0 USE_EABI_HARDFLOAT=3D1 qemu: uncaught target signal 11 (Segmentation fault) - core dumped Calling qemu with gdb gives the following information: Thread 1 "qemu-arm" received signal SIGSEGV, Segmentation fault. 0x0000555555d63d11 in static_code_gen_buffer () and (gdb) bt #0 0x0000555555d63d11 in static_code_gen_buffer () #1 0x0000555555628d58 in cpu_tb_exec (itb=3D, cpu=3D0x55= 5557c33930) at = /tmp/build/qemu/accel/tcg/cpu-exec.c:172 #2 cpu_loop_exec_tb (tb_exit=3D, last_tb=3D, tb=3D, = cpu=3D0x555557c33930) at /tmp/build/qemu/accel/tcg/cpu-exec.c:618 #3 cpu_exec (cpu=3Dcpu@entry=3D0x555557c2b660) at /tmp/build/qemu/accel= /tcg/cpu-exec.c:731 #4 0x0000555555661578 in cpu_loop (env=3D0x555557c33930) at /tmp/build/= qemu/linux-user/arm/cpu_loop.c:219 #5 0x00005555555d6d76 in main (argc=3D, argv=3D, envp=3D) at /tmp/build/qemu/linux-user/main.c:865 Calling qemu-arm with debug switch "-d in_asm,int,op_opt" shows the log in the attached file. Thanks for any hints! Fabian To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1856837/+subscriptions