From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 3550 invoked by alias); 30 Nov 2009 12:27:14 -0000 Received: (qmail 3541 invoked by uid 22791); 30 Nov 2009 12:27:13 -0000 X-SWARE-Spam-Status: No, hits=-1.7 required=5.0 tests=AWL,BAYES_00,SARE_MSGID_LONG40,SPF_PASS X-Spam-Check-By: sourceware.org Received: from mail-pw0-f49.google.com (HELO mail-pw0-f49.google.com) (209.85.160.49) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Mon, 30 Nov 2009 12:27:07 +0000 Received: by pwi1 with SMTP id 1so2034554pwi.8 for ; Mon, 30 Nov 2009 04:27:05 -0800 (PST) MIME-Version: 1.0 Received: by 10.143.26.31 with SMTP id d31mr445027wfj.269.1259584025281; Mon, 30 Nov 2009 04:27:05 -0800 (PST) In-Reply-To: <4B11607C.7000500@vmware.com> 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> Date: Mon, 30 Nov 2009 16:03:00 -0000 Message-ID: Subject: Re: System call support in reversible debugging From: Hui Zhu To: =?UTF-8?Q?Michael_Snyder_=3Cmsnyder=40vmware=2Ecom=3E=EF=BC=8CSean_Chen?= Cc: "gdb@sourceware.org" 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: 2009-11/txt/msg00214.txt.bz2 Cool! I think your explain is very clear. Thanks. :) Hui On Sun, Nov 29, 2009 at 01:40, Michael Snyder wrote: > Sean Chen wrote: >> >> On Sat, Nov 28, 2009 at 2:07 AM, Michael Snyder >> wrote: >>> >>> These are two separate questions. =A0I think the one you started with >>> is can gdb record a system call, and the answer is "yes". >>> >>> >>> The issue with mmap has a lot of history, and rather than try to >>> explain it, I urge you to look up the threads which have "mmap" >>> or "sbrk" in the title) and read them. >>> >>> >> >> Thanks for the explanation. That is very kind of you. >> >> I am confused about the first question. How does gdb record the system >> call instructions? You know, they are in the kernel space? It seems >> that I must have made a mistake somewhere. Please help to clarify. >> >> Thanks in advance. > > Sean, > > I wish I understood this better -- maybe Hui will explain it more. > > As I understand it, each system call is recorded as if it were a > single instruction. =A0Instead of 'tracing' into the system code, > we know the specific side effects for each system call, and for > instance if the syscall will write to a buffer we take a snapshot > of that buffer first. > > Michael > >