From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mx1.redhat.com ([209.132.183.28]) by merlin.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1UIhPQ-0006ld-Qi for kexec@lists.infradead.org; Thu, 21 Mar 2013 15:28:05 +0000 Date: Thu, 21 Mar 2013 11:27:51 -0400 From: Vivek Goyal Subject: Re: [PATCH v3 18/21] vmcore: check if vmcore objects satify mmap()'s page-size boundary requirement Message-ID: <20130321152751.GK3934@redhat.com> References: <8738vp75cy.fsf@xmission.com> <20130321.151428.393714972.d.hatayama@jp.fujitsu.com> <87ip4l1d1q.fsf@xmission.com> <20130321.154650.424925595.d.hatayama@jp.fujitsu.com> <87a9pxz0wv.fsf@xmission.com> <20130321152124.GJ3934@redhat.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20130321152124.GJ3934@redhat.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: "Eric W. Biederman" Cc: kexec@lists.infradead.org, heiko.carstens@de.ibm.com, linux-kernel@vger.kernel.org, lisa.mitchell@hp.com, HATAYAMA Daisuke , kumagai-atsushi@mxc.nes.nec.co.jp, zhangyanfei@cn.fujitsu.com, akpm@linux-foundation.org, cpw@sgi.com On Thu, Mar 21, 2013 at 11:21:24AM -0400, Vivek Goyal wrote: [..] > So if starting or end address of PT_LOAD header is not aligned, why > not we simply allocate a page. Copy the relevant data from old memory, > fill rest with zero. That way mmap and read view will be same. There > will be no surprises w.r.t reading old kernel memory beyond what's > specified by the headers. Copying from old memory might spring surprises w.r.t hw poisoned pages. I guess we will have to disable MCE, read page, enable it back or something like that to take care of these issues. In the past we have recommended makedumpfile to be careful, look at struct pages and make sure we are not reading poisoned pages. But vmcore itself is reading old memory and can run into this issue too. Thanks Vivek _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932811Ab3CUP2J (ORCPT ); Thu, 21 Mar 2013 11:28:09 -0400 Received: from mx1.redhat.com ([209.132.183.28]:44132 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932229Ab3CUP2H (ORCPT ); Thu, 21 Mar 2013 11:28:07 -0400 Date: Thu, 21 Mar 2013 11:27:51 -0400 From: Vivek Goyal To: "Eric W. Biederman" Cc: HATAYAMA Daisuke , cpw@sgi.com, kumagai-atsushi@mxc.nes.nec.co.jp, lisa.mitchell@hp.com, heiko.carstens@de.ibm.com, akpm@linux-foundation.org, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, zhangyanfei@cn.fujitsu.com Subject: Re: [PATCH v3 18/21] vmcore: check if vmcore objects satify mmap()'s page-size boundary requirement Message-ID: <20130321152751.GK3934@redhat.com> References: <8738vp75cy.fsf@xmission.com> <20130321.151428.393714972.d.hatayama@jp.fujitsu.com> <87ip4l1d1q.fsf@xmission.com> <20130321.154650.424925595.d.hatayama@jp.fujitsu.com> <87a9pxz0wv.fsf@xmission.com> <20130321152124.GJ3934@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130321152124.GJ3934@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 21, 2013 at 11:21:24AM -0400, Vivek Goyal wrote: [..] > So if starting or end address of PT_LOAD header is not aligned, why > not we simply allocate a page. Copy the relevant data from old memory, > fill rest with zero. That way mmap and read view will be same. There > will be no surprises w.r.t reading old kernel memory beyond what's > specified by the headers. Copying from old memory might spring surprises w.r.t hw poisoned pages. I guess we will have to disable MCE, read page, enable it back or something like that to take care of these issues. In the past we have recommended makedumpfile to be careful, look at struct pages and make sure we are not reading poisoned pages. But vmcore itself is reading old memory and can run into this issue too. Thanks Vivek