From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 4319 invoked by alias); 1 Dec 2009 20:21:31 -0000 Received: (qmail 4310 invoked by uid 22791); 1 Dec 2009 20:21:30 -0000 X-SWARE-Spam-Status: No, hits=-2.6 required=5.0 tests=BAYES_00 X-Spam-Check-By: sourceware.org Received: from smarthost01.mail.zen.net.uk (HELO smarthost01.mail.zen.net.uk) (212.23.3.140) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Tue, 01 Dec 2009 20:21:25 +0000 Received: from [82.71.15.62] (helo=[192.168.123.72]) by smarthost01.mail.zen.net.uk with esmtpsa (TLS-1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.63) (envelope-from ) id 1NFZDu-0003vx-D0; Tue, 01 Dec 2009 20:21:22 +0000 Message-ID: <4B157A21.9020603@undo-software.com> Date: Tue, 01 Dec 2009 20:21:00 -0000 From: Greg Law User-Agent: Thunderbird 2.0.0.23 (X11/20090817) MIME-Version: 1.0 To: Jakob Engblom CC: 'Sean Chen' , 'Hui Zhu' , gdb@sourceware.org Subject: Re: System call support in reversible debugging References: <5e81cb500911262231g57f693dwc885576172e016e1@mail.gmail.com> <5e81cb500911270711wb99d531i111d064f05ef03b4@mail.gmail.com> <5e81cb500911270742j546062f2jca7441a912ffad87@mail.gmail.com> <4B10154F.7070902@vmware.com> <5e81cb500911271745t1a119520l4944919d2139e8ae@mail.gmail.com> <4B11607C.7000500@vmware.com> <5e81cb500911300539r52e8be5dva54d32c734978021@mail.gmail.com> <00a701ca7279$f1a03c60$d4e0b520$@com> In-Reply-To: <00a701ca7279$f1a03c60$d4e0b520$@com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 8bit X-Originating-Smarthost01-IP: [82.71.15.62] 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: 2009-12/txt/msg00012.txt.bz2 Ok, I can't resist jumping in :) Jakob Engblom wrote: > >> Hi Michael and Hui, >> >> I am sorry for my late response. >> >> Thanks for your explanation. So we can’t treat the system calls as a >> black box and have to understand the detailed implementation of each >> system call. I think we need to understand every lines of the code in >> the system calls carefully enough, and care about the difference of >> the Linux kernel since the code of system calls might change >> frequently. Do we have any good ways to do it? > > To really do this right, you should use a full-system simulator that lets you > debug OS and user code at the same time, as it is attacking the system at the > hardware/software interface level. It all depends what you want to do. If you want to debug kernel code, then absolutely you need a full system approach, such as Simics or VMware offers. Similarly if you want to debug the whole host. But if you're debugging just a process (i.e. the classic use-case of gdb), you may not want to wind back the state of the entire (virtual) machine. In which case, something like UndoDB or prec is more appropriate. I don't claim either approach is superior. It's a bit like native debugging versus remote debugging. Which one makes most sense all depends on what it is you're trying to debug. Greg -- Greg Law, Undo Software http://undo-software.com/