From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 26296 invoked by alias); 2 Dec 2009 17:16:38 -0000 Received: (qmail 26287 invoked by uid 22791); 2 Dec 2009 17:16:37 -0000 X-SWARE-Spam-Status: No, hits=-2.1 required=5.0 tests=AWL,BAYES_00 X-Spam-Check-By: sourceware.org Received: from vtab.com (HELO oden.vtab.com) (62.20.90.195) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Wed, 02 Dec 2009 17:16:24 +0000 Received: from oden.vtab.com (oden.vtab.com [127.0.0.1]) by oden.vtab.com (Postfix) with ESMTP id A8F9626EEC8; Wed, 2 Dec 2009 18:16:19 +0100 (CET) Received: from polhem (unknown [62.20.90.206]) (using TLSv1 with cipher AES128-SHA (128/128 bits)) (No client certificate requested) by oden.vtab.com (Postfix) with ESMTP id 6259926EF07; Wed, 2 Dec 2009 18:16:19 +0100 (CET) From: "Jakob Engblom" To: "'Greg Law'" Cc: "'Sean Chen'" , "'Hui Zhu'" , 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> <4B157A21.9020603@undo-software.com> In-Reply-To: <4B157A21.9020603@undo-software.com> Subject: RE: System call support in reversible debugging Date: Wed, 02 Dec 2009 17:16:00 -0000 Message-ID: <003201ca7373$29b6f590$7d24e0b0$@com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit 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: 2009-12/txt/msg00015.txt.bz2 > >> 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. Couldn't agree more. The full-system approach is a bit more gnarly, but it gives you more insight. It depends on the problem. /jakob