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=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,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 06AC1C4742C for ; Sat, 14 Nov 2020 00:50:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BC9922225E for ; Sat, 14 Nov 2020 00:50:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725885AbgKNAuq (ORCPT ); Fri, 13 Nov 2020 19:50:46 -0500 Received: from gate.crashing.org ([63.228.1.57]:38907 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725866AbgKNAuq (ORCPT ); Fri, 13 Nov 2020 19:50:46 -0500 Received: from gate.crashing.org (localhost.localdomain [127.0.0.1]) by gate.crashing.org (8.14.1/8.14.1) with ESMTP id 0AE0hL3I007474; Fri, 13 Nov 2020 18:43:21 -0600 Received: (from segher@localhost) by gate.crashing.org (8.14.1/8.14.1/Submit) id 0AE0hIMX007471; Fri, 13 Nov 2020 18:43:18 -0600 X-Authentication-Warning: gate.crashing.org: segher set sender to segher@kernel.crashing.org using -f Date: Fri, 13 Nov 2020 18:43:18 -0600 From: Segher Boessenkool To: Nick Desaulniers Cc: Alexandre Chartre , kbuild-all@lists.01.org, clang-built-linux , linux-toolchains@vger.kernel.org, kernel test robot , Arvind Sankar , Ard Biesheuvel , Miguel Ojeda , Peter Zijlstra , Linus Torvalds , Kees Cook Subject: Re: [RFC][PATCH 21/24] x86/entry: Disable stack-protector for IST entry C handlers Message-ID: <20201114004318.GY2672@gate.crashing.org> References: <20201109144425.270789-22-alexandre.chartre@oracle.com> <202011131552.4kvOb9Id-lkp@intel.com> <20201113234701.GV2672@gate.crashing.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.3i Precedence: bulk List-ID: X-Mailing-List: linux-toolchains@vger.kernel.org On Fri, Nov 13, 2020 at 04:11:41PM -0800, Nick Desaulniers wrote: > On Fri, Nov 13, 2020 at 3:49 PM Segher Boessenkool > wrote: > > On Fri, Nov 13, 2020 at 10:59:26AM -0800, Nick Desaulniers wrote: > > > The `optimize` attribute is both non-portable across toolchains (hence > > > this warning) > > > > Like *all* GCC extensions. > > > > > and a little quirky in GCC. > > > > How so? Don't spread FUD please, say what *is* wrong, then people can > > decide for themselves whether they want it or not. > > Spread FUD? Ard literally sent TO YOU: > https://lore.kernel.org/lkml/CAMj1kXHxX+u5-cN0v3SLdqZTSiKsWsFOvc2SC5=-ScaUZOu8Ng@mail.gmail.com/, > and it was referenced again in > https://lore.kernel.org/lkml/20201028081123.GT2628@hirez.programming.kicks-ass.net/. > > Was it FUD when Ard sent it to you? He didn't say "this option is a little quirky". He simply quoted our wiki entry for it, which says "use this only for debugging" (just like the user documentation btw). The FAQ also goes on to explain the attribute is very hard to use, it is not obvious at all what flags you can and cannot set, it's a user interface disaster. It explains what is bad with it, it doesn't just say "ooh I don't understand it, do not use it". (It does say "no one really understands it, do not use it", there is that ;-) ) Segher