Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761246AbYGBFOe (ORCPT ); Wed, 2 Jul 2008 01:14:34 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752801AbYGBFO0 (ORCPT ); Wed, 2 Jul 2008 01:14:26 -0400 Received: from wx-out-0506.google.com ([66.249.82.227]:60509 "EHLO wx-out-0506.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752799AbYGBFOZ (ORCPT ); Wed, 2 Jul 2008 01:14:25 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=googlemail.com; s=gamma; h=message-id:date:from:to:subject:cc:in-reply-to:mime-version :content-type:content-transfer-encoding:content-disposition :references; b=v4Uza7PKKwd+y0+P+VGJyoNxWnWbe8t/VD9cbwmhHIFAJjcDHGiPrOgAkaZRw/RMVF okIkQqpMwEE+fsP6OzwGzsl5OC32/TykJ9fDxcqkS0T3n/vC31sJMb4Zmz0HUgeuJtSZ AeR5RFXF49sOaN5YDObxrXsPD1IAeA4NAgxZ0= Message-ID: Date: Wed, 2 Jul 2008 07:14:22 +0200 From: "Michael Kerrisk" To: "Bron Gondwana" Subject: Re: mmap'ed memory in core files ? Cc: "Michael Kerrisk" , "Philippe De Muyter" , linux-kernel@vger.kernel.org, robm@fastmail.fm In-Reply-To: <20080701214423.GA29875@brong.net> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <20080701132149.GA32510@frolo.macqel> <517f3f820807011116g6ce1b3e1qf166070f7a4c523f@mail.gmail.com> <20080701214423.GA29875@brong.net> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2292 Lines: 48 On Tue, Jul 1, 2008 at 11:44 PM, Bron Gondwana wrote: > On Tue, Jul 01, 2008 at 08:16:11PM +0200, Michael Kerrisk wrote: >> On 7/1/08, Philippe De Muyter wrote: >> > Hello everybody, >> > >> > I develop video acquisition software using the video1394 interface. >> > The images grabbed by the camera and iee1394 bus are kept in kernel >> > memory and made available to the user program through a mmap call done >> > in the libdc1394 library : >> > >> > dma_ring_buffer= mmap(0, vmmap.nb_buffers * vmmap.buf_size, >> > PROT_READ|PROT_WRITE,MAP_SHARED, craw->capture.dma_fd, 0); >> > >> > Sometimes, my program crashes and produces a core file :) It seems to >> > me that the core file does not contain the mmap'ed memory and hence >> > I cannot replay my program with the same image for debugging purpose. >> > >> > Is it possible to configure the kernel through /proc, or through the mmap >> > system call to have that mmapped segment in the core file, or do I need >> > to modify the kernel itself to obtain the behaviour I want ? If I >> > need to modify the kernel, can some kind soul provide me some pointers ? >> >> >> Have a look at the section "Controlling which mappings are written to >> the core dump" in a recent core.5 man page: >> http://www.kernel.org/doc/man-pages/online/pages/man5/core.5.html > > Interesting (and somewhat off topic to your conversation here) - it > appears that when dumping mappings, the kernel ignores the maximum > core size set with "limit". > > This is particularly interesting on a 64 bit kernel where a bug in > your code causes you to try to read something about 2Gb into your > alleged mmaped file (actual size ~500 bytes) and the segfault causes > a coredump. Do you have a ssimple example program for this? -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ man-pages online: http://www.kernel.org/doc/man-pages/online_pages.html Found a bug? http://www.kernel.org/doc/man-pages/reporting_bugs.html -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/