Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932319AbZICVSm (ORCPT ); Thu, 3 Sep 2009 17:18:42 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932278AbZICVSl (ORCPT ); Thu, 3 Sep 2009 17:18:41 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:55062 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755210AbZICVSk (ORCPT ); Thu, 3 Sep 2009 17:18:40 -0400 Date: Thu, 3 Sep 2009 23:18:05 +0200 From: Ingo Molnar To: "H. Peter Anvin" Cc: Jeremy Fitzhardinge , mingo@redhat.com, linux-kernel@vger.kernel.org, jeremy.fitzhardinge@citrix.com, stable@kernel.org, tglx@linutronix.de, linux-tip-commits@vger.kernel.org, Tejun Heo , Arjan van de Ven Subject: Re: [tip:x86/asm] x86/i386: Make sure stack-protector segment base is cache aligned Message-ID: <20090903211805.GB12566@elte.hu> References: <4AA01893.6000507@goop.org> <4AA02687.9080406@zytor.com> <4AA02B02.7080101@goop.org> <4AA031DE.2070109@zytor.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4AA031DE.2070109@zytor.com> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.5 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1032 Lines: 26 * H. Peter Anvin wrote: > On 09/03/2009 01:45 PM, Jeremy Fitzhardinge wrote: > > > > Two problems: > > > > * gcc generates %gs: references for stack-protector, but we use %fs > > for percpu data (because restoring %fs is faster if it's a null > > selector; TLS uses %gs). I guess we could use %fs if > > !CONFIG_CC_STACKPROTECTOR, or %gs if we are using it (though that > > has some fiddly ramifications for things like ptrace). > > Well, by touching two segments we're getting the worst of both > worlds, so at least assuming some significant number of real-world > deployments use CC_STACKPROTECTOR, we really don't want to > pessimize that case too much. Fedora has stackprotector enabled so it's used in a widespread way. Ingo -- 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/