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=-5.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, 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 86555C33C9E for ; Fri, 17 Jan 2020 17:41:18 +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 4D94B206D5 for ; Fri, 17 Jan 2020 17:41:18 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="f4rlt56r" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4D94B206D5 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]:60984 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1isVcT-0007ab-Ej for qemu-devel@archiver.kernel.org; Fri, 17 Jan 2020 12:41:17 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:54640) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1isVbP-00071K-FO for qemu-devel@nongnu.org; Fri, 17 Jan 2020 12:40:13 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1isVbN-0002KC-Pp for qemu-devel@nongnu.org; Fri, 17 Jan 2020 12:40:11 -0500 Received: from mail-wm1-x342.google.com ([2a00:1450:4864:20::342]:51433) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1isVbN-0002JO-HL for qemu-devel@nongnu.org; Fri, 17 Jan 2020 12:40:09 -0500 Received: by mail-wm1-x342.google.com with SMTP id d73so8253684wmd.1 for ; Fri, 17 Jan 2020 09:40:09 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=references:user-agent:from:to:cc:subject:in-reply-to:date :message-id:mime-version:content-transfer-encoding; bh=GG/2yOwLVaV+NUVQmSrEYPITPWV6B/NHd3Qy4LJRUb4=; b=f4rlt56rpuNi2WjjVN2ntDSRO9D5KwW2V7NgCDjFMaobrXfPV8acAqs2kgZHbvbsbr +w0iiCWHZl4uPz3c1j4FuAev5Ol69fVTlwhp+eVWRxGRgorTLcOeQ7pCp+u89sSid43z is0r+pAE5aZ9Mv8PXtpVUfvBFP/NgbBxVhk0+Sd85xX0FO2hnmv9at0Cg/M3b3snz6xO BhyMFuNqHhSXRFiYxDPN7tGRaSHbk2ddxJ/comcqE2Amk6yhtUtLTJdW5aBC6RduDMup QMUDVweq1jccCIBwQrargC8bfB9sPQJwiYLwuzYy8QXsqIYZhygh45nljP9IBe2Xy1Py RxkA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:references:user-agent:from:to:cc:subject :in-reply-to:date:message-id:mime-version:content-transfer-encoding; bh=GG/2yOwLVaV+NUVQmSrEYPITPWV6B/NHd3Qy4LJRUb4=; b=sRcDhZR+tsMllAw8YES9jZlLUxQGP1OCMZzhf5tsCX5n35AgKj8Uu7hmKsDiekCdIx wEqTnpANzoi/4bdj9jREvh2aeIepJgIAuRp5Cmi70g8czaH9fLCam8p+xHPonENHFi9k FyZPSIs3KygVbYgWDuPtP/2prrXZLvqOjncFiuXuYvG+dhaR/NJqygVKMiK16i5YTEfB 0WIvWpMrS0UWJ66fx8OBOFKau8osQiGnEs5McuP+PD6LZkINc++HbLqEvASCbgUWnIwa unzz3scEu8HB/vKV0rZjqJKImMSCB9ZPSlGs8/2xPV2B8p8jlLjxeSzvAhLMvAuHM8A4 oqJA== X-Gm-Message-State: APjAAAViqtJsMSt5VzbK3i1ieC3xng/nsfKEbg8qStoekhP9iIP6NSTw txFKxVeeHyFEBEMr202LlOb/hw== X-Google-Smtp-Source: APXvYqxfI1+cs4atV0QYx3OYg2xVrwa6VxEd10jrDVnoNG6yUID15K1wOG+jhQtzVoryw7r6TOeqKw== X-Received: by 2002:a1c:cc11:: with SMTP id h17mr5688217wmb.19.1579282808465; Fri, 17 Jan 2020 09:40:08 -0800 (PST) Received: from zen.linaroharston ([51.148.130.216]) by smtp.gmail.com with ESMTPSA id p17sm34860891wrx.20.2020.01.17.09.40.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 17 Jan 2020 09:40:07 -0800 (PST) Received: from zen (localhost [127.0.0.1]) by zen.linaroharston (Postfix) with ESMTP id 612491FF87; Fri, 17 Jan 2020 17:40:06 +0000 (GMT) References: <157709434917.12933.4351155074716553976.stgit@pasha-Precision-3630-Tower> <87o8v3lkq8.fsf@linaro.org> <000f01d5cc5f$cccb90b0$6662b210$@ru> User-agent: mu4e 1.3.6; emacs 28.0.50 From: Alex =?utf-8?Q?Benn=C3=A9e?= To: Pavel Dovgalyuk Subject: Re: [for-5.0 PATCH 00/11] Support for reverse debugging with GDB In-reply-to: <000f01d5cc5f$cccb90b0$6662b210$@ru> Date: Fri, 17 Jan 2020 17:40:06 +0000 Message-ID: <871rrykmmh.fsf@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 2a00:1450:4864:20::342 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" Pavel Dovgalyuk writes: >> From: Alex Benn=C3=A9e [mailto:alex.bennee@linaro.org] >> Pavel Dovgalyuk writes: >>=20 >> > 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 >>=20 >> So I tried with your additional patch. Launching QEMU as: >>=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=3Dreplay,rrfile=3Drecord.bin \ >> -s -S -d trace:gdbstub\* >>=20 >> And gdb: >>=20 >> gdb tests/tcg/aarch64-softmmu/memory \ >> -ex "target remote localhost:1234" >>=20 >> I get the following log: >>=20 >> (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 >>=20 >> 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 >>=20 >> 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 ./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,rr= snapshot=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 supp= ort live migration qemu-system-aarch64: Could not create snapshot for icount record I don't know if this is down to the current state of the tree but I haven't been able to get it working. > > After that you can replay the execution with the support of reverse debug= ging: > > ./aarch64-softmmu//qemu-system-aarch64 -monitor none \ > -display none -M virt -cpu max \ > -kernel ./tests/tcg/aarch64-softmmu/memory \ > -icount shift=3D5,rr=3Dreplay,rrfile=3Drecord.bin,rrsnapshot=3Dinit= \ > -drive file=3Dempty.qcow2 > > I removed "-semihosting-config enable=3Don", because I'm not sure what is= it for. > It may break the replay, because there is no implementation of > semihosting input record/replay. For this testcase semihosting in just a convenient output device (in lieu of a serial device). 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. > > Pavel Dovgalyuk --=20 Alex Benn=C3=A9e