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=-5.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 27C66C2D0DB for ; Mon, 20 Jan 2020 11:59:11 +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 F0689208E4 for ; Mon, 20 Jan 2020 11:59:10 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org F0689208E4 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=ispras.ru Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:35126 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1itVi2-00034l-4v for qemu-devel@archiver.kernel.org; Mon, 20 Jan 2020 06:59:10 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:49942) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1itVhM-0002dB-2o for qemu-devel@nongnu.org; Mon, 20 Jan 2020 06:58:29 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1itVhK-0000kW-CZ for qemu-devel@nongnu.org; Mon, 20 Jan 2020 06:58:27 -0500 Received: from mail.ispras.ru ([83.149.199.45]:33844) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1itVhK-0000hu-0w for qemu-devel@nongnu.org; Mon, 20 Jan 2020 06:58:26 -0500 Received: from PASHAISP (unknown [85.142.117.226]) by mail.ispras.ru (Postfix) with ESMTPSA id 990B3725C1; Mon, 20 Jan 2020 14:58:21 +0300 (MSK) From: "Pavel Dovgalyuk" To: =?UTF-8?Q?'Alex_Benn=C3=A9e'?= References: <157709434917.12933.4351155074716553976.stgit@pasha-Precision-3630-Tower> <87o8v3lkq8.fsf@linaro.org> <000f01d5cc5f$cccb90b0$6662b210$@ru> <871rrykmmh.fsf@linaro.org> In-Reply-To: <871rrykmmh.fsf@linaro.org> Subject: RE: [for-5.0 PATCH 00/11] Support for reverse debugging with GDB Date: Mon, 20 Jan 2020 14:58:21 +0300 Message-ID: <002f01d5cf88$eaabfee0$c003fca0$@ru> MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Mailer: Microsoft Office Outlook 12.0 thread-index: AdXNXSokBMQOaR6eS1q6nT2VhQMT/QCKxx1A Content-Language: ru X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 83.149.199.45 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kwolf@redhat.com, peter.maydell@linaro.org, pavel.dovgaluk@ispras.ru, crosthwaite.peter@gmail.com, ciro.santilli@gmail.com, jasowang@redhat.com, quintela@redhat.com, qemu-devel@nongnu.org, armbru@redhat.com, maria.klimushenkova@ispras.ru, mst@redhat.com, kraxel@redhat.com, boost.lists@gmail.com, thomas.dullien@googlemail.com, pbonzini@redhat.com, mreitz@redhat.com, artem.k.pisarenko@gmail.com, dgilbert@redhat.com, rth@twiddle.net Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" > From: Alex Benn=C3=A9e [mailto:alex.bennee@linaro.org] > Pavel Dovgalyuk writes: >=20 > >> From: Alex Benn=C3=A9e [mailto:alex.bennee@linaro.org] > >> Pavel Dovgalyuk writes: > >> > >> > GDB remote protocol supports reverse debugging of the targets. > >> > It includes 'reverse step' and 'reverse continue' operations. > >> > The first one finds the previous step of the execution, > >> > and the second one is intended to stop at the last breakpoint = that > >> > would happen when the program is executed normally. > >> > > >> > Reverse debugging is possible in the replay mode, when at least > >> > one snapshot was created at the record or replay phase. > >> > QEMU can use these snapshots for travelling back in time with = GDB. > >> > > >> > Running the execution in replay mode allows using GDB reverse = debugging > >> > commands: > >> > - reverse-stepi (or rsi): Steps one instruction to the past. > >> > QEMU loads on of the prior snapshots and proceeds to the = desired > >> > instruction forward. When that step is reaches, execution = stops. > >> > - reverse-continue (or rc): Runs execution "backwards". > >> > QEMU tries to find breakpoint or watchpoint by loaded prior = snapshot > >> > and replaying the execution. Then QEMU loads snapshots again = and > >> > replays to the latest breakpoint. When there are no = breakpoints in > >> > the examined section of the execution, QEMU finds one more = snapshot > >> > and tries again. After the first snapshot is processed, = execution > >> > stops at this snapshot. > >> > > >> > The set of patches include the following modifications: > >> > - gdbstub update for reverse debugging support > >> > - functions that automatically perform reverse step and reverse > >> > continue operations > >> > - hmp/qmp commands for manipulating the replay process > >> > - improvement of the snapshotting for saving the execution step > >> > in the snapshot parameters > >> > > >> > The patches are available in the repository: > >> > https://github.com/ispras/qemu/tree/rr-191223 > >> > >> So I tried with your additional patch. Launching QEMU as: > >> > >> ./aarch64-softmmu//qemu-system-aarch64 -monitor none \ > >> -display none -M virt -cpu max -display none \ > >> -semihosting-config enable=3Don \ > >> -kernel ./tests/tcg/aarch64-softmmu/memory \ > >> -icount shift=3D5,rr=3Dreplay,rrfile=3Drecord.bin \ > >> -s -S -d trace:gdbstub\* > >> > >> And gdb: > >> > >> gdb tests/tcg/aarch64-softmmu/memory \ > >> -ex "target remote localhost:1234" > >> > >> I get the following log: > >> > >> (gdb) x/3i $pc > >> =3D> 0x400037b0 <__start>: adr x0, 0x40003000 = > >> 0x400037b4 <__start+4>: msr vbar_el1, x0 > >> 0x400037b8 <__start+8>: adrp x0, 0x40200000 > >> (gdb) p/x $x0 > >> $1 =3D 0x0 > >> (gdb) si > >> 92 msr vbar_el1, x0 > >> (gdb) p/x $x0 > >> $2 =3D 0x40003000 > >> (gdb) rsi > >> warning: Remote failure reply: E14 > >> > >> Program stopped. > >> __start () at = /home/alex.bennee/lsrc/qemu.git/tests/tcg/aarch64/system/boot.S:92 > >> 92 msr vbar_el1, x0 > >> (gdb) p/x $x0 > >> $3 =3D 0x40003000 > >> > >> So it doesn't seem to be working. > > > > That's ok, you'll need at least one VM snapshot available to recover = the initial VM state. > > Try changing the command lines in the following way: > > > > First, create empty.qcow2 which will be used for saving the = snapshots. > > Then record with initial snapshot and attached empty.qcow2: > > > > ./aarch64-softmmu//qemu-system-aarch64 -monitor none \ > > -display none -M virt -cpu max \ > > -kernel ./tests/tcg/aarch64-softmmu/memory \ > > -icount = shift=3D5,rr=3Drecord,rrfile=3Drecord.bin,rrsnapshot=3Dinit \ > > -drive file=3Dempty.qcow2 >=20 > ./aarch64-softmmu//qemu-system-aarch64 -monitor none -display none -M = virt -cpu max -display > none -semihosting-config enable=3Don -kernel = ./tests/tcg/aarch64-softmmu/memory -icount > shift=3D5,rr=3Drecord,rrfile=3Drecord.bin,rrsnapshot=3Dinit -drive = file=3Dempty.qcow2 > qemu-system-aarch64: invalid accelerator kvm > qemu-system-aarch64: falling back to tcg > qemu-system-aarch64: The qcow format used by node '#block163' does not = support live migration > qemu-system-aarch64: Could not create snapshot for icount record It seems that you have some problems with your disk image. Is it qcow2 = or just qcow? > For this testcase semihosting in just a convenient output device (in > lieu of a serial device).=20 I tried this test kernel with your options and everything was ok. > We probably need to come up with a strategy on > how we handle all these devices otherwise we will end up with a random > selection of hardware combinations which work. All correctly implemented virtual hardware should support record/replay. But real semihosting (like file IO) should not, because it provides untracked virtual machine inputs. Pavel Dovgalyuk