From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 17038 invoked by alias); 16 Sep 2016 15:43:52 -0000 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 Received: (qmail 17022 invoked by uid 89); 16 Sep 2016 15:43:52 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-4.2 required=5.0 tests=BAYES_00,RP_MATCHES_RCVD,SPF_HELO_PASS autolearn=ham version=3.3.2 spammy= 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 ESMTP; Fri, 16 Sep 2016 15:43:51 +0000 Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id F183CC05AA70; Fri, 16 Sep 2016 15:43:49 +0000 (UTC) Received: from [127.0.0.1] (ovpn01.gateway.prod.ext.ams2.redhat.com [10.39.146.11]) by int-mx10.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id u8GFhml3000540; Fri, 16 Sep 2016 11:43:49 -0400 Subject: Re: [PATCH 0/6] S390: Watchpoint enhancements and hardware breakpoints To: Ulrich Weigand References: <20160916124323.AE052FE999@oc8523832656.ibm.com> Cc: Andreas Arnez , gdb-patches@sourceware.org From: Pedro Alves Message-ID: Date: Fri, 16 Sep 2016 15:43:00 -0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.2.0 MIME-Version: 1.0 In-Reply-To: <20160916124323.AE052FE999@oc8523832656.ibm.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-SW-Source: 2016-09/txt/msg00181.txt.bz2 On 09/16/2016 01:43 PM, Ulrich Weigand wrote: > Pedro Alves wrote: >> I'm curious on the need to disable hw breakpoints when single-stepping. > > This is more of a hardware restriction than a GDB issue. The problem is > that s390 hardware doesn't really have a separate hardware single-step > feature; to implement ptrace single-stepping, the kernel uses the s390 > hardware breakpoint feature (in effect, enabling hardware breakpoints > on the full address space, which will hit on the next instruction that > is executed). > > This use of the feature by kernel single-stepping can conflict with > explicit use of the same feature by GDB; that's why it is better to > not attempt such explicit use while at the same time also requesting > kernel single-stepping. I see. Thanks for the clarification. A comment to the effect in the code would be nice. Maybe it's there and I missed it. I have no further comments on the series. LGTM. Thanks, Pedro Alves