From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754152AbZKHMiW (ORCPT ); Sun, 8 Nov 2009 07:38:22 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753697AbZKHMiV (ORCPT ); Sun, 8 Nov 2009 07:38:21 -0500 Received: from pfepb.post.tele.dk ([195.41.46.236]:53622 "EHLO pfepb.post.tele.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753565AbZKHMiU (ORCPT ); Sun, 8 Nov 2009 07:38:20 -0500 Date: Sun, 8 Nov 2009 13:38:25 +0100 From: Sam Ravnborg To: Ingo Molnar Cc: mingo@redhat.com, hpa@zytor.com, linux-kernel@vger.kernel.org, hare@suse.de, akpm@linux-foundation.org, tglx@linutronix.de, linux-tip-commits@vger.kernel.org Subject: Re: [tip:x86/urgent] x86: Add back _end symbol that is missing from Symbol.map Message-ID: <20091108123825.GA11904@merkur.ravnborg.org> References: <200911041519.nA4FJWEW030164@imap1.linux-foundation.org> <20091108113805.GA11847@merkur.ravnborg.org> <20091108114829.GQ11372@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20091108114829.GQ11372@elte.hu> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Nov 08, 2009 at 12:48:29PM +0100, Ingo Molnar wrote: > > * Sam Ravnborg wrote: > > > On Sun, Nov 08, 2009 at 11:07:12AM +0000, tip-bot for Hannes Reinecke wrote: > > > Commit-ID: d1e4d37b79e944f6351ae38eb1ca7c9f7b506e76 > > > Gitweb: http://git.kernel.org/tip/d1e4d37b79e944f6351ae38eb1ca7c9f7b506e76 > > > Author: Hannes Reinecke > > > AuthorDate: Wed, 4 Nov 2009 07:19:32 -0800 > > > Committer: Ingo Molnar > > > CommitDate: Sun, 8 Nov 2009 12:05:03 +0100 > > > > > > x86: Add back _end symbol that is missing from Symbol.map > > > > > > With 2.6.31 'crash' on x86_64 falls flat on its face as the > > > '_end' symbol is missing from the System.map file. > > > > > > The culprit is commit 091e52c3551d3031343df24b573b770b4c6c72b6, > > > which moved the '_end' symbol into it's own section. Apparently > > > this causes kallsyms to not reference it properly. > > > > > > So do not include _end in it's own section. > > > > > > Signed-off-by: Andrew Morton > > > Cc: Sam Ravnborg > > > Cc: # .31.x > > > LKML-Reference: <200911041519.nA4FJWEW030164@imap1.linux-foundation.org> > > > Signed-off-by: Ingo Molnar > > > > I'm afraid this will break a RELOCTABLE i386 kernel. > > > > We fixed this up some time ago where we had to > > move the symbol definition inside a section > > to prevent the symbol being absolute. > > ah, indeed. So ... the question is then, why did _end disappear from > System.map? I think ld discards zero size sections. No need to keep them around if they are empty. Following patch should fix it up in a better way. I reused most of Hannes changelog. Sam [PATCH] x86: Add back _end symbol that is missing from Symbol.map With 2.6.31 'crash' on x86_64 falls flat on its face as the '_end' symbol is missing from the System.map file. The culprit is commit 091e52c3551d3031343df24b573b770b4c6c72b6, which moved the '_end' symbol into it's own section. The problem is likely that ld discards empty sections. So move the definition of _end into the last section defined. Cc: Hannes Reinecke Cc: Andrew Morton Cc: # .31.x Signed-off-by: Sam Ravnborg diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S index 92929fb..c58a6e3 100644 --- a/arch/x86/kernel/vmlinux.lds.S +++ b/arch/x86/kernel/vmlinux.lds.S @@ -289,9 +289,12 @@ SECTIONS . += 64 * 1024; /* 64k alignment slop space */ *(.brk_reservation) /* areas brk users have reserved */ __brk_limit = .; - } - .end : AT(ADDR(.end) - LOAD_OFFSET) { + /* + * To support RELOCTABLE kernel _end must be inside a section. + * And ld is know to discard empty section so we locate _end in + * last section we define. + */ _end = .; }