From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754690Ab1G0NAW (ORCPT ); Wed, 27 Jul 2011 09:00:22 -0400 Received: from mtagate3.uk.ibm.com ([194.196.100.163]:59705 "EHLO mtagate3.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754171Ab1G0M6R (ORCPT ); Wed, 27 Jul 2011 08:58:17 -0400 Message-Id: <20110727125807.695225427@linux.vnet.ibm.com> User-Agent: quilt/0.48-1 Date: Wed, 27 Jul 2011 14:55:06 +0200 From: Michael Holzheu To: vgoyal@redhat.com Cc: ebiederm@xmission.com, mahesh@linux.vnet.ibm.com, hbabu@us.ibm.com, oomichi@mxs.nes.nec.co.jp, horms@verge.net.au, schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org Subject: [patch v2 02/10] kdump: Make kimage_load_crash_segment() weak References: <20110727125504.491183728@linux.vnet.ibm.com> Content-Disposition: inline; filename=s390-kdump-common-load_crash_segment.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Michael Holzheu On s390 we do not create page tables at all for the crashkernel memory. This requires a s390 specific version for kimage_load_crash_segment(). Therefore this patch declares this function as "__weak". The s390 version is very simple. It just copies the kexec segment to real memory without using page tables: int kimage_load_crash_segment(struct kimage *image, struct kexec_segment *segment) { return copy_from_user_real((void *) segment->mem, segment->buf, segment->bufsz); } There are two main advantages of not creating page tables for the crashkernel memory: a) It saves memory. We have scenarios in mind, where crashkernel memory can be very large and saving page table space is important. b) We protect the crashkernel memory from being overwritten. Signed-off-by: Michael Holzheu --- kernel/kexec.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/kernel/kexec.c +++ b/kernel/kexec.c @@ -842,8 +842,8 @@ out: return result; } -static int kimage_load_crash_segment(struct kimage *image, - struct kexec_segment *segment) +int __weak kimage_load_crash_segment(struct kimage *image, + struct kexec_segment *segment) { /* For crash dumps kernels we simply copy the data from * user space to it's destination.