From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030825AbWKOSpa (ORCPT ); Wed, 15 Nov 2006 13:45:30 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030853AbWKOSp3 (ORCPT ); Wed, 15 Nov 2006 13:45:29 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:41381 "EHLO mx2.mail.elte.hu") by vger.kernel.org with ESMTP id S1030825AbWKOSpZ (ORCPT ); Wed, 15 Nov 2006 13:45:25 -0500 Date: Wed, 15 Nov 2006 19:44:33 +0100 From: Ingo Molnar To: Jeremy Fitzhardinge Cc: Arjan van de Ven , akpm@osdl.org, ak@suse.de, linux-kernel@vger.kernel.org, Michael.Fetterman@cl.cam.ac.uk, Ian Campbell Subject: Re: i386 PDA patches use of %gs Message-ID: <20061115184433.GB5078@elte.hu> References: <1158046540.2992.5.camel@laptopd505.fenrus.org> <45075829.701@goop.org> <20060913095942.GA10075@elte.hu> <45082F1C.8000003@goop.org> <20061115182613.GA2227@elte.hu> <20061115182915.GA2705@elte.hu> <455B5FB6.7010009@goop.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <455B5FB6.7010009@goop.org> User-Agent: Mutt/1.4.2.2i X-ELTE-SpamScore: -4.4 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-4.4 required=5.9 tests=ALL_TRUSTED,AWL,BAYES_00 autolearn=no SpamAssassin version=3.0.3 -3.3 ALL_TRUSTED Did not pass through any untrusted hosts -2.6 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] 1.5 AWL AWL: From: address is in the auto white-list X-ELTE-VirusStatus: clean Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org * Jeremy Fitzhardinge wrote: > > that loads (and uses) a single selector value for %fs, and doesnt do > > any mixed use as far as i can see. > > I'm not sure what you're getting at. Each loop iteration is analogous > to a user->kernel->user transition with respect to the > save/reload/use/restore pattern on the segment register. In this > case, %fs starts as a null selector, gets reloaded with a non NULL > selector, and then is restored to null. Do you mean some other > mixing? yeah, mixed use: i.e. set up /two/ selector values and load them into %gs and read+write memory through them. It might not change the results, but that's what i meant under 'mixed use'. Ingo