From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 99053 invoked by alias); 19 Jun 2017 21:56:53 -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 98950 invoked by uid 89); 19 Jun 2017 21:56:52 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-1.9 required=5.0 tests=BAYES_00,SPF_HELO_PASS,T_RP_MATCHES_RCVD autolearn=ham version=3.3.2 spammy=invented 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; Mon, 19 Jun 2017 21:56:42 +0000 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 568155D68D; Mon, 19 Jun 2017 21:56:46 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 568155D68D Authentication-Results: ext-mx10.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx10.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=palves@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com 568155D68D Received: from [127.0.0.1] (ovpn04.gateway.prod.ext.ams2.redhat.com [10.39.146.4]) by smtp.corp.redhat.com (Postfix) with ESMTP id 793F682098; Mon, 19 Jun 2017 21:56:45 +0000 (UTC) Subject: Re: [PATCH 02/25] Adjust the order of 32bit-linux.xml and 32bit-sse.xml in i386/i386-linux.xml To: Simon Marchi References: <1497256916-4958-1-git-send-email-yao.qi@linaro.org> <1497256916-4958-3-git-send-email-yao.qi@linaro.org> <9a60c2a9-09ef-c21a-db18-385105d986a1@redhat.com> <2469fcc8da14028094caf53330145210@polymtl.ca> Cc: Yao Qi , gdb-patches@sourceware.org From: Pedro Alves Message-ID: <7872d3fa-7131-d84c-483d-05eca415ca63@redhat.com> Date: Mon, 19 Jun 2017 21:56:00 -0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 MIME-Version: 1.0 In-Reply-To: <2469fcc8da14028094caf53330145210@polymtl.ca> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-SW-Source: 2017-06/txt/msg00552.txt.bz2 On 06/19/2017 10:48 PM, Simon Marchi wrote: > On 2017-06-19 23:24, Pedro Alves wrote: >> Unless this is a case of a default target description matching >> the layout of targets that predated support for XML descriptions. >> >> Could that be the case here? From: >> >> static void >> i386_linux_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch) >> { >> ... >> if (! tdesc_has_registers (tdesc)) >> tdesc = tdesc_i386_linux; >> ... >> >> ... it may well be. So we need to tread carefully here. The >> order may be required for back compatibility. A deeper audit >> with that in mind is in order. > Do you mean that this might impact backward compatibility with older > gdbservers (or other remotes) that don't send XML target descriptions > and just assume a certain "well-known" register numbering? Yes. It may be easy to check against gdbserver. You'd need to hack it to disable the x86 xml tdesc support, which is a relatively recent addition. [It took a while for the x86 port to support xml tdescs]. The xmlRegisters= qSupported feature had to invented to keep backward compatibility back then. E.g., hack gdb's remote.c:register_remote_support_xml, or gdbserver's linux-x86-low.c:x86_linux_process_qsupported. If, with x86 XML support disabled, before vs after patch the layout of GDB's g/G packet buffer changes, then you have a back compatibility break. Thanks, Pedro Alves