Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756871AbZIDOMr (ORCPT ); Fri, 4 Sep 2009 10:12:47 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756835AbZIDOMq (ORCPT ); Fri, 4 Sep 2009 10:12:46 -0400 Received: from casper.infradead.org ([85.118.1.10]:40160 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756829AbZIDOMp (ORCPT ); Fri, 4 Sep 2009 10:12:45 -0400 Date: Fri, 4 Sep 2009 07:15:24 -0700 From: Arjan van de Ven To: Ingo Molnar Cc: "H. Peter Anvin" , 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 Subject: Re: [tip:x86/asm] x86/i386: Make sure stack-protector segment base is cache aligned Message-ID: <20090904071524.0a7267ce@infradead.org> In-Reply-To: <20090903211805.GB12566@elte.hu> References: <4AA01893.6000507@goop.org> <4AA02687.9080406@zytor.com> <4AA02B02.7080101@goop.org> <4AA031DE.2070109@zytor.com> <20090903211805.GB12566@elte.hu> Organization: Intel X-Mailer: Claws Mail 3.7.2 (GTK+ 2.14.7; i386-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1379 Lines: 39 On Thu, 3 Sep 2009 23:18:05 +0200 Ingo Molnar wrote: > > * 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 the other issue is that afaik we want the kernel to use the other register than userspace does... -- Arjan van de Ven Intel Open Source Technology Centre For development, discussion and tips for power savings, visit http://www.lesswatts.org -- 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/