Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757041Ab3EXRGC (ORCPT ); Fri, 24 May 2013 13:06:02 -0400 Received: from mx1.redhat.com ([209.132.183.28]:51106 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756996Ab3EXRGA (ORCPT ); Fri, 24 May 2013 13:06:00 -0400 Date: Fri, 24 May 2013 13:05:07 -0400 From: Vivek Goyal To: Michael Holzheu Cc: HATAYAMA Daisuke , Jan Willeke , Martin Schwidefsky , Heiko Carstens , linux-kernel@vger.kernel.org, kexec@lists.infradead.org, Andrew Morton , "Eric W. Biederman" Subject: Re: [PATCH 0/2] kdump/mmap: Fix mmap of /proc/vmcore for s390 Message-ID: <20130524170507.GG18218@redhat.com> References: <1369400889-11064-1-git-send-email-holzheu@linux.vnet.ibm.com> <20130524143644.GD18218@redhat.com> <20130524170626.2ac06efe@holzheu> <20130524152849.GF18218@redhat.com> <20130524184653.52d75b5f@holzheu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130524184653.52d75b5f@holzheu> 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 Content-Length: 1557 Lines: 37 On Fri, May 24, 2013 at 06:46:53PM +0200, Michael Holzheu wrote: > On Fri, 24 May 2013 11:28:49 -0400 > Vivek Goyal wrote: > > > On Fri, May 24, 2013 at 05:06:26PM +0200, Michael Holzheu wrote: > > [snip] > > > As /proc/vmcore is the most used and useful interface, I prefer that > > we swap memory and put that info in elf headers. For /dev/oldme, I > > don't mind if we leave it as it is. If somebody really cares, then > > I guess we need to write a new command line option which /dev/mem > > can parse and which tells it about swaps so that /dev/oldmem can > > map things correctly. (This is better than hardcoding things). > > Besides of the potential /dev/oldmem issue, I still do not understand > the option of doing the swap in the elf header. Looks like I missed > here a fundamental design point of kdump :( > > Is that done by specifying different virtual and physical addresses in > the ELF header? Nope. We keep the virtual to physical address mapping same. We just modify the p_offset in PT_LOAD elf header to represent where actually the memory is present physically. And when /proc/vmcore reads the data, it reads it from p_offset. IOW, p_offset and p_paddr will be different for swapped memory but should be same for memory which has not been swapped. Thanks Vivek -- 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/