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=-10.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham 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 E7082C43461 for ; Tue, 8 Sep 2020 22:25:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AA2032067C for ; Tue, 8 Sep 2020 22:25:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729738AbgIHWZa convert rfc822-to-8bit (ORCPT ); Tue, 8 Sep 2020 18:25:30 -0400 Received: from jabberwock.ucw.cz ([46.255.230.98]:59576 "EHLO jabberwock.ucw.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728620AbgIHWZ3 (ORCPT ); Tue, 8 Sep 2020 18:25:29 -0400 Received: by jabberwock.ucw.cz (Postfix, from userid 1017) id D96C01C0B87; Wed, 9 Sep 2020 00:25:25 +0200 (CEST) Date: Wed, 9 Sep 2020 00:25:24 +0200 From: Pavel Machek To: Sedat Dilek Cc: Segher Boessenkool , Arvind Sankar , Thomas Gleixner , Nick Desaulniers , "Paul E. McKenney" , Ingo Molnar , Arnd Bergmann , Borislav Petkov , "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" , "H. Peter Anvin" , "Kirill A. Shutemov" , Zhenzhong Duan , Kees Cook , Peter Zijlstra , Juergen Gross , Andy Lutomirski , Andrew Cooper , LKML , clang-built-linux , Will Deacon , Linus Torvalds , Miguel Ojeda Subject: Re: [PATCH] x86: work around clang IAS bug referencing __force_order Message-ID: <20200908222524.GE1005@bug> References: <875z9dioll.fsf@nanos.tec.linutronix.de> <20200820130641.GA536306@rani.riverdale.lan> <87zh6ohm03.fsf@nanos.tec.linutronix.de> <20200821230435.GA56974@rani.riverdale.lan> <87eenzqzmr.fsf@nanos.tec.linutronix.de> <20200822035552.GA104886@rani.riverdale.lan> <20200822084133.GL28786@gate.crashing.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: 8BIT In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat 2020-08-22 11:51:56, Sedat Dilek wrote: > On Sat, Aug 22, 2020 at 11:23 AM Sedat Dilek wrote: > > > > On Sat, Aug 22, 2020 at 10:42 AM Segher Boessenkool > > wrote: > > > > > > Hi Arvind, > > > > > > On Fri, Aug 21, 2020 at 11:55:52PM -0400, Arvind Sankar wrote: > > > > Cc Segher. > > > > > > > > Segher, we were looking at gcc PR82602, where IRA could reorder volatile > > > > asm's (reported on ARM). The fix was backported to gcc-6. > > > > > > I know ;-) > > > > > > > Do you know if > > > > there is any reason the problem couldn't occur on x86 on older gcc > > > > without the fix? > > > > > > No, I see no particular reason, at least GCC 5 seems vulnerable. (The > > > GCC 5 release branch was closed at the time this bug report was made, > > > already). There is no reason I see why it would work on x86 but fail > > > elsewhere, either. > > > > > > > [1] says: > > > > Current Minimal Requirements > > ... > > ====================== =============== ======================================== > > Program Minimal version Command to check the version > > ====================== =============== ======================================== > > GNU C 4.9 gcc --version > > > > - Sedat - > > > > [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/changes.rst#n32 > > [ CC Miguel Ojeda (Compiler Attributes maintainer) ] > > There exist gcc-4.8 and gcc-4.9 for Debian/jessie where EOL was June > 30, 2020 (see [1] and [2]). > > In the latest available version "4.9.2-10+deb8u1" I see no PR82602 was > backported (see [3] and [4]). > > I am asking myself who is using such ancient compilers? > Recently, I threw away GCC-8 from my Debian system. I do have 4.9.2 on some systems. They work well, and are likely to compile significantly faster than newer ones. Please don't break them. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html