From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, TVD_SUBJ_WIPE_DEBT,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 77C59C43461 for ; Thu, 10 Sep 2020 17:29:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3F30D20C09 for ; Thu, 10 Sep 2020 17:29:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727826AbgIJR3c (ORCPT ); Thu, 10 Sep 2020 13:29:32 -0400 Received: from gate.crashing.org ([63.228.1.57]:45363 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726996AbgIJRYJ (ORCPT ); Thu, 10 Sep 2020 13:24:09 -0400 Received: from gate.crashing.org (localhost.localdomain [127.0.0.1]) by gate.crashing.org (8.14.1/8.14.1) with ESMTP id 08AHFhOX006110; Thu, 10 Sep 2020 12:15:43 -0500 Received: (from segher@localhost) by gate.crashing.org (8.14.1/8.14.1/Submit) id 08AHFgui006109; Thu, 10 Sep 2020 12:15:42 -0500 X-Authentication-Warning: gate.crashing.org: segher set sender to segher@kernel.crashing.org using -f Date: Thu, 10 Sep 2020 12:15:42 -0500 From: Segher Boessenkool To: David Laight Cc: "'Christophe Leroy'" , "'Linus Torvalds'" , linux-arch , Kees Cook , the arch/x86 maintainers , Nick Desaulniers , Linux Kernel Mailing List , Alexey Dobriyan , Luis Chamberlain , Al Viro , linux-fsdevel , linuxppc-dev , Christoph Hellwig Subject: Re: remove the last set_fs() in common code, and remove it for x86 and powerpc v3 Message-ID: <20200910171542.GL28786@gate.crashing.org> References: <20200903142803.GM1236603@ZenIV.linux.org.uk> <20200909184001.GB28786@gate.crashing.org> <3beb8b019e4a4f7b81fdb1bc68bd1e2d@AcuMS.aculab.com> <186a62fc-042c-d6ab-e7dc-e61b18945498@csgroup.eu> <59a64e9a210847b59f70f9bd2d02b5c3@AcuMS.aculab.com> <5050b43687c84515a49b345174a98822@AcuMS.aculab.com> <20200910152030.GJ28786@gate.crashing.org> <18fdbaeacba349a0a8bf7568f709e991@AcuMS.aculab.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <18fdbaeacba349a0a8bf7568f709e991@AcuMS.aculab.com> User-Agent: Mutt/1.4.2.3i Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 10, 2020 at 03:31:53PM +0000, David Laight wrote: > > > asm volatile ("" : "+r" (eax)); > > > // So here eax must contain the value set by the "xxxxx" instructions. > > > > No, the register eax will contain the value of the eax variable. In the > > asm; it might well be there before or after the asm as well, but none of > > that is guaranteed. > > Perhaps not 'guaranteed', but very unlikely to be wrong. > It doesn't give gcc much scope for not generating the desired code. Wanna bet? :-) Correct is correct. Anything else is not. Segher