From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 4169 invoked by alias); 22 Jul 2011 16:02:56 -0000 Received: (qmail 4159 invoked by uid 22791); 22 Jul 2011 16:02:55 -0000 X-SWARE-Spam-Status: No, hits=-1.2 required=5.0 tests=AWL,BAYES_00,RCVD_IN_DNSWL_NONE X-Spam-Check-By: sourceware.org Received: from mailrelay003.isp.belgacom.be (HELO mailrelay003.isp.belgacom.be) (195.238.6.53) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Fri, 22 Jul 2011 16:02:40 +0000 X-Belgacom-Dynamic: yes X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: Av0EAECdKU5tgH6w/2dsb2JhbABTihqdLHiIfAK7CA6FUl8Eo08 Received: from 176.126-128-109.adsl-dyn.isp.belgacom.be (HELO soleil) ([109.128.126.176]) by relay.skynet.be with SMTP; 22 Jul 2011 18:02:39 +0200 Message-ID: From: "Philippe Waroquiers" To: "Pedro Alves" , Cc: References: <201106090059.42380.pedro@codesourcery.com> <201107211712.26443.pedro@codesourcery.com> Subject: Re: x86 watchpoints bug (Re: ping: Re: PATCH : allow to set length of hw watchpoints (e.g. for Valgrind gdbserver)) Date: Fri, 22 Jul 2011 16:40:00 -0000 MIME-Version: 1.0 Content-Type: text/plain; format=flowed; charset="iso-8859-15"; reply-type=original Content-Transfer-Encoding: 7bit X-IsSubscribed: yes Mailing-List: contact gdb-patches-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sourceware.org X-SW-Source: 2011-07/txt/msg00622.txt.bz2 > I think nothing else changed in the patch. I looked at the new patch and re-tested on f12/x86 and debian5/amd64, using 7.3. Behaviour looks ok to me regarding the handling of debug registers. (note I tested with the patch allowing to change the remote hw watchpoint length, which I believe could be committed soon : FSF papers ok, waiting for a user now). During the testing, I however found something else slightly strange. With reference to the previous s.c test program, watching a string length 1000 is ok at the start (handled as a sw breakpoint), but this watchpoint cannot be disabled then re-enabled: (gdb) watch s1000 Hardware watchpoint 1: s1000 (gdb) start <<<<<<<<<<<<<<<<<<<<<<<<<< this runs slowly as s1000 is sw-watched Temporary breakpoint 2 at 0x400480: file s.c, line 22. Starting program: /home/philippe/gdb/s Error in re-setting breakpoint 1: Expression cannot be implemented with read/access watchpoint. Error in re-setting breakpoint 1: Expression cannot be implemented with read/access watchpoint. Error in re-setting breakpoint 1: Expression cannot be implemented with read/access watchpoint. Temporary breakpoint 2, main () at s.c:22 22 char * p = s1000; (gdb) dis 1 (gdb) ena 1 Cannot enable watchpoint 1: Expression cannot be implemented with read/access watchpoint. (gdb) At this point, if the watchpoint is deleted then re-created, then the watchpoint is again 'sw-accepted'. Note that this looks to be a regression in 7.3.50.20110722-cvs, as I do not see the same problem on 7.2. This regression is not linked with the DR patch (occurs both with the patched/non patched 7.3.50). So, in summary: * the patch for the i386 debug register fix looks ok. The following strange behaviours/bugs have still to be fixed or looked at: * handling of duplicate locations across disabled breakpoints (resulting in wrongly duplicated z packets and/or missing active debug registers in native) * watch s1000 then run then disable then enable impossible There was also a 'nice to have' which could be looked at: * ensure that the insertion of watchpoint is done using the order of breakpoints (so as to not have a new watchpoint causing an error/rejection on a previously accepted watchpoint). Thanks for all the work Philippe