From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 109766 invoked by alias); 12 Mar 2015 16:28:22 -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 109752 invoked by uid 89); 12 Mar 2015 16:28:21 -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; Thu, 12 Mar 2015 16:28:20 +0000 Received: from int-mx14.intmail.prod.int.phx2.redhat.com (int-mx14.intmail.prod.int.phx2.redhat.com [10.5.11.27]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id t2CGSJAa018733 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL) for ; Thu, 12 Mar 2015 12:28:19 -0400 Received: from [127.0.0.1] (ovpn01.gateway.prod.ext.ams2.redhat.com [10.39.146.11]) by int-mx14.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id t2CGSGUK021039; Thu, 12 Mar 2015 12:28:17 -0400 Message-ID: <5501BEA0.70804@redhat.com> Date: Thu, 12 Mar 2015 16:28:00 -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: Oleg Nesterov CC: Jan Kratochvil , Sergio Durigan Junior , GDB Patches Subject: Re: [PATCH] Improve corefile generation by using /proc/PID/coredump_filter (PR corefile/16902) References: <878ufc9kau.fsf@redhat.com> <20150305154827.GA9441@host1.jankratochvil.net> <87zj7r5fpz.fsf@redhat.com> <20150305205744.GA13165@host1.jankratochvil.net> <20150311200052.GA22654@redhat.com> <20150312150024.GA4817@redhat.com> <5501B48B.7060802@redhat.com> <20150312160551.GA8144@redhat.com> In-Reply-To: <20150312160551.GA8144@redhat.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-SW-Source: 2015-03/txt/msg00348.txt.bz2 On 03/12/2015 04:05 PM, Oleg Nesterov wrote: > On 03/12, Pedro Alves wrote: >> >> On 03/12/2015 03:00 PM, Oleg Nesterov wrote: >> >>> However. If (for any reason) you decide to dump this region, gdb can >>> look into /proc/self/maps, find its own "vvar" mapping, and simply read >>> this memory. Unlike "vdso", "vvar" has the same content for every process. >> >> Actually it can't: GDB may well be dumping the memory of >> a process running on another machine (through gdbserver). > > Yes, thanks for correcting me... > > I do not know if gdb can ask gdbserver to read its own memory, but even if > it can this doesn't look like a nice solution. Not currently, it can't. > > Just curious... I know that gdb can execute the code on behalf of the traced > process, so perhaps it can force the tracee to memcpy() its "vvar" memory. > Can this work with gdbserver? Again, I do not think this hack can make any > sense. I am just curious. Yes, that can work. But it's horrible. :-) If the user is dumping the process's core, it's likely because the traced process is already in a not-so-good / corrupted state. Forcing it to run more code may make things worse. > At least (I hope) this mapping doesn't look "important" from debugging pov, > perhaps gdb should ignore it. Lets see what Andy thinks, Agreed, let's hear what Andy says. > but I bet it is > very unlikely that the kernel will be changed to allow the access to this > vma. Thanks, Pedro Alves