From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 121649 invoked by alias); 5 Mar 2015 20:57:52 -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 121632 invoked by uid 89); 5 Mar 2015 20:57:51 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-3.9 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, 05 Mar 2015 20:57:50 +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 t25Kvnjl013477 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL) for ; Thu, 5 Mar 2015 15:57:49 -0500 Received: from host1.jankratochvil.net ([10.40.204.26]) by int-mx13.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id t25KvjOm032090 (version=TLSv1/SSLv3 cipher=AES256-SHA bits=256 verify=NO); Thu, 5 Mar 2015 15:57:48 -0500 Date: Thu, 05 Mar 2015 20:57:00 -0000 From: Jan Kratochvil To: Sergio Durigan Junior Cc: GDB Patches , Pedro Alves , Oleg Nesterov Subject: Re: [PATCH] Improve corefile generation by using /proc/PID/coredump_filter (PR corefile/16902) Message-ID: <20150305205744.GA13165@host1.jankratochvil.net> References: <878ufc9kau.fsf@redhat.com> <20150305154827.GA9441@host1.jankratochvil.net> <87zj7r5fpz.fsf@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87zj7r5fpz.fsf@redhat.com> User-Agent: Mutt/1.5.23 (2014-03-12) X-IsSubscribed: yes X-SW-Source: 2015-03/txt/msg00165.txt.bz2 On Thu, 05 Mar 2015 21:52:56 +0100, Sergio Durigan Junior wrote: > On Thursday, March 05 2015, Jan Kratochvil wrote: > > On Thu, 05 Mar 2015 04:48:09 +0100, Sergio Durigan Junior wrote: > >> With Oleg's help, we could improve the current algorithm for determining > >> whether a memory mapping is anonymous/file-backed, private/shared. GDB > >> now also respects the MADV_DONTDUMP flag and does not dump the memory > > > > s/does not dump/does dump/ > > No, it doesn't dump. MADV_DONTDUMP activates the "dd" flag in VmFlags, > and the patch looks for it and, if it finds the flag, it doesn't mark > the memory mapping to be dumped. However, GDB will create the section > header in the corefile. Sorry, I meesed it up even more. For MADV_DONTDUMP you are right, FSF GDB dumps MADV_DONTDUMP memory, kernel does not and with this patch GDB will not. What I wanted to say was: > >> mapping marked as so, and won't try to dump "[vsyscall]" or "[vdso]" s/won't try/will try/ this one. > >> mappings as before (just like the Linux kernel). > > > > Currently it also tries to dump [vvar] (by default rules) but that is > > unreadable for some reason, causing: > > warning: Memory read failed for corefile section, 8192 bytes at 0x7ffff6ceb000. > > ^^^^^^^^^^^^^^ > > Saved corefile /tmp/1j > > (gdb) _ > > # grep 7ffff6ceb000 /proc/$p/maps > > 7ffff6ceb000-7ffff6ced000 r--p 00000000 00:00 0 [vvar] > > ^^^^^^^^^^^^ ^^^^ > > > > I do not know what [vvar] is good for and why it cannot be read. > > I totally forgot about this, even though we discussed it before. Sorry; > I am sending a new version of the patch which addresses this issue. It would be good to get a reply from a kernel aware person what does it mean before such patch gets accepted. It can be also just a Linux kernel bug. Jan