From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 87285 invoked by alias); 17 Mar 2015 19:03:17 -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 87275 invoked by uid 89); 17 Mar 2015 19:03:16 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-2.0 required=5.0 tests=AWL,BAYES_00,SPF_HELO_PASS,SPF_PASS,T_RP_MATCHES_RCVD 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; Tue, 17 Mar 2015 19:03:06 +0000 Received: from int-mx11.intmail.prod.int.phx2.redhat.com (int-mx11.intmail.prod.int.phx2.redhat.com [10.5.11.24]) by mx1.redhat.com (Postfix) with ESMTPS id 14983C63E3; Tue, 17 Mar 2015 19:03:05 +0000 (UTC) Received: from [127.0.0.1] (ovpn01.gateway.prod.ext.ams2.redhat.com [10.39.146.11]) by int-mx11.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id t2HJ33GW026204; Tue, 17 Mar 2015 15:03:04 -0400 Message-ID: <55087A67.1070403@redhat.com> Date: Tue, 17 Mar 2015 19:03:00 -0000 From: Pedro Alves User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.5.0 MIME-Version: 1.0 To: Ulrich Weigand CC: Wei-cheng Wang , gdb-patches@sourceware.org Subject: Re: [PATCH 1/2] Fast tracepoint for powerpc64le References: <201503171812.t2HICbPn030976@d06av02.portsmouth.uk.ibm.com> In-Reply-To: <201503171812.t2HICbPn030976@d06av02.portsmouth.uk.ibm.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-SW-Source: 2015-03/txt/msg00500.txt.bz2 On 03/17/2015 06:12 PM, Ulrich Weigand wrote: > Pedro Alves wrote: >> On 02/27/2015 07:52 PM, Ulrich Weigand wrote: >>> So I guess there's two ways to fix this. One would be to change >>> gdbserver to work more like GDB here. This would involve removing >>> the descriptor->code address conversion in remote.c, and instead >>> performing the conversion in gdbserver's thread_db_enable_reporting. >>> Now, there is no gdbarch_convert_from_func_ptr_addr in gdbserver, >>> so a similar mechanism would have to be invented there. (I guess >>> this would mean a new target hook.) Fortunately, the only platform >>> that uses function descriptors *and* supports libthread_db debugging >>> in gdbserver is ppc64-linux, so we'd only have to add that new >>> mechanim on this platform. >> >> Note sure about this one, ppc64_convert_from_func_ptr_addr wants to >> get at the bfd/binary's unrelocated sections. We'd have to teach >> gdbserver to read the binary. > > That's probably not necessary. The reason the GDB implementation > does it that way is that it needs to work under various different > circumstances, like when debugging a core file, or before the > dynamic linker has relocated an executable. For the gdbserver > implementation, we should never need to handle such conditions, > so we are able to simply read the target address from memory. > Maybe not cores today, but why doesn't gdbserver have to handle the case of connecting before the executable has been relocated? I also wonder about all the break-interp.exp corner cases. >> (Note for testing: __nptl_create_event will only be used >> on old kernels without PTRACE_EVENT_CLONE, unless you hack the >> code to force usage.) > > I wonder why Wei-cheng noticed the problem then ... I think he is seeing the problem with the function symbol look ups gdbserver's tracepoints module does (tracepoint_look_up_symbols), and that in that case he needs to get the function descriptor instead of the start of code address? From your previous explanation I understand that the __nptl_create_event breakpoint (when used) is set correctly because what gdbserver needs in that case is the start of code address, which is what remote.c returns. Thanks, Pedro Alves