From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 23998 invoked by alias); 26 Oct 2009 08:02:25 -0000 Received: (qmail 23679 invoked by uid 22791); 26 Oct 2009 08:02:23 -0000 X-SWARE-Spam-Status: No, hits=-2.1 required=5.0 tests=AWL,BAYES_00 X-Spam-Check-By: sourceware.org Received: from dns.vtab.com (HELO oden.vtab.com) (62.20.90.195) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Mon, 26 Oct 2009 08:02:19 +0000 Received: from oden.vtab.com (oden.vtab.com [127.0.0.1]) by oden.vtab.com (Postfix) with ESMTP id 4BF5326EF17; Mon, 26 Oct 2009 09:02:17 +0100 (CET) Received: from polhem (c83-253-31-27.bredband.comhem.se [83.253.31.27]) (using TLSv1 with cipher AES128-SHA (128/128 bits)) (No client certificate requested) by oden.vtab.com (Postfix) with ESMTP id 23B5426EF0E; Mon, 26 Oct 2009 09:02:17 +0100 (CET) From: "Jakob Engblom" To: "'Michael Snyder'" , "'Marc Khouzam'" Cc: "'Hui Zhu'" , References: <4ADA4BD8.6080800@vmware.com> <4ADCAD14.3080407@vmware.com> <4ADE1824.8090701@vmware.com> In-Reply-To: <4ADE1824.8090701@vmware.com> Subject: RE: [FYI] tutorial for process record and reverse debugging Date: Mon, 26 Oct 2009 08:06:00 -0000 Message-ID: <00a201ca5612$a38198e0$ea84caa0$@com> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable X-IsSubscribed: yes Mailing-List: contact gdb-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-owner@sourceware.org X-SW-Source: 2009-10/txt/msg00373.txt.bz2 > >> b) Truncate the existing log at the point where I am, and > >> start appending to the prefix? > > > > I never thought of this case. I see now that for non-deterministic > > executions this could have value. >=20 > Not just that, though. This is also what happens if we > change a memory or register value, eg. a variable that > controls a conditional branch. We auto-delete the trailing > part of the execution log, because now we're going to go > forward in a different direction. This is pretty useful, actually. We have done that in Simics for a long ti= me, go back in time, and delete the recording of activity, to take a different = path. You can use it to "undo" mistakes (it is pretty funny to sit on a target console, type "rm -rf /*", see the system implode... and then go back and j= ust undo the delete, delete the recording, and move on with an intact file syst= em).=20 You can use it to systematically explore system behavior, such as going bac= k and changing program inputs, hardware latencies, or other controllable aspects.= It is neat for fault injection: go back, chagnge value or register or delete a network packet, and then compare the results.=20=20 Best regards, /jakob _______________________________________________________ Jakob Engblom, PhD, Technical Marketing Manager Virtutech=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 Direct: +46= 8 690 07 47=A0=A0=A0 Drottningholmsv=E4gen 22=A0=A0=A0=A0=A0 Mobile: +46 709 242 646=A0=A0 11243 Stockholm=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 Web:=A0=A0=A0 www.virtu= tech.com=A0 Sweden ________________________________________________________ =A0=20 So yes, it is something that is pretty useful.