From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751010AbXCAMff (ORCPT ); Thu, 1 Mar 2007 07:35:35 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752007AbXCAMfe (ORCPT ); Thu, 1 Mar 2007 07:35:34 -0500 Received: from mail4.hitachi.co.jp ([133.145.228.5]:33463 "EHLO mail4.hitachi.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751010AbXCAMfd (ORCPT ); Thu, 1 Mar 2007 07:35:33 -0500 Message-ID: <45E6C888.4050300@hitachi.com> Date: Thu, 01 Mar 2007 21:35:20 +0900 From: "Kawai, Hidehiro" User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; ja-JP; rv:1.4) Gecko/20030624 Netscape/7.1 (ax) X-Accept-Language: ja MIME-Version: 1.0 To: Markus Gutschke Cc: Andrew Morton , kernel list , Pavel Machek , Robin Holt , dhowells@redhat.com, Alan Cox , Masami Hiramatsu , sugita , Satoshi OSHIMA , "Hideo AOKI@redhat" Subject: Re: [PATCH 0/4] coredump: core dump masking support v3 References: <45D5B2E3.3030607@hitachi.com> <45DFB1C7.1030205@google.com> In-Reply-To: <45DFB1C7.1030205@google.com> Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi, Markus Gutschke wrote: > Kawai, Hidehiro wrote: > >> This patch series is version 3 of the core dump masking feature, >> which provides a per-process flag not to dump anonymous shared >> memory segments. > > I just wanted to remind you that you need to be careful about dumping > the [vdso] segment no matter whether you omit other segments. I didn't > actually try running your patches, and if the kernel doesn't actually > consider this segment anonymous and shared, things might already work > fine as is. Thank you for your advice and sorry for not replying soon. Fortunately, the latest kernel uses VM_ALWAYSDUMP flag to always dump the vdso segment. My patchset doesn't change this behavior. So we don't need to worry about the vdso segment. > As an alternative to your kernel patch, you could achieve the same goal > in user space, by linking my coredumper > http://code.google.com/p/google-coredumper/ into your binaries and > setting up appropriate signal handlers. An equivalent patch for > selectively omitting memory regions would be trivial to add. As far as I can see, google-coredumper has more flexibility. Can google-coredumper satisfy the following requirements easily? Requirements are: (1) a user can change the core dump settings _anytime_ - sometimes want to dump anonymous shared memory segments and sometimes don't want to dump them (2) a user can change the core dump settings of _any processes_ (although permission checks are performed) - in a huge application which forks many processes, a user hopes that some processes dump anonymous shared memory segments and some processes don't dump them And reliability of the core dump feature is also important. > While this > does give you more flexibility, it of course has the drawback of > requiring you to change your applications, so there still is some > benefit in a kernelspace solution. And all the software vendors don't necessarily apply google-coredumper. If the vendor doesn't apply it, the user will be bothered by huge core dumps or the buggy application which remains unfixed. So I believe that in kernel solution is still needed. Thanks, -- Hidehiro Kawai Hitachi, Ltd., Systems Development Laboratory