From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 8168 invoked by alias); 5 Sep 2014 00:28:42 -0000 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 Received: (qmail 8157 invoked by uid 89); 5 Sep 2014 00:28:42 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-2.8 required=5.0 tests=AWL,BAYES_00,RP_MATCHES_RCVD,SPF_HELO_PASS,SPF_PASS autolearn=ham version=3.3.2 X-HELO: mx1.redhat.com Received: from mx1.redhat.com (HELO mx1.redhat.com) (209.132.183.28) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with (AES256-GCM-SHA384 encrypted) ESMTPS; Fri, 05 Sep 2014 00:28:40 +0000 Received: from int-mx13.intmail.prod.int.phx2.redhat.com (int-mx13.intmail.prod.int.phx2.redhat.com [10.5.11.26]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id s850SZCD020299 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Thu, 4 Sep 2014 20:28:35 -0400 Received: from [127.0.0.1] (ovpn01.gateway.prod.ext.ams2.redhat.com [10.39.146.11]) by int-mx13.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id s850SW1x009620; Thu, 4 Sep 2014 20:28:33 -0400 Message-ID: <540903B0.3000009@redhat.com> Date: Fri, 05 Sep 2014 00:28:00 -0000 From: Pedro Alves User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.7.0 MIME-Version: 1.0 To: Gareth McMullin , Joel Brobecker CC: gdb@sourceware.org Subject: Re: question about ARM watchpoints References: <20140901085743.GG4981@adacore.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-SW-Source: 2014-09/txt/msg00014.txt.bz2 On 09/04/2014 11:36 PM, Gareth McMullin wrote: > Hi > > On Mon, Sep 1, 2014 at 8:57 PM, Joel Brobecker wrote: >> Everything works pretty well, except that we noticed that GDB stops >> 2 instructions after the variable update, rather than at the next >> instruction. > > I get the same behaviour on the Black Magic Probe on ARMv7-M. > The DWT halts the core on the instruction after the address match. > >> The question then becomes: Is QEMU behaving correctly, in which >> case we should be modifying GDB, or is QEMU signaling GDB too >> late, in which case we should be fixing QEMU? > > What QEMU is doing is the same as the hardware DWT block, so I'd > say this is the correct behaviour. The fix should be in GDB. Working > around this in QEMU would leave all hardware based implementations > broken. So sounds like this line should be skipped on ARMv7-M: arm-tdep.c: set_gdbarch_have_nonsteppable_watchpoint (gdbarch, 1); Could you try removing it? But then I wonder why we never heard of this before. Are there ARMv7-M's that behave differently? And what about ARMv6-M ? Thanks, Pedro Alves