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=-7.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS, 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 9A1E2C7618B for ; Wed, 24 Jul 2019 12:55:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 79368218B8 for ; Wed, 24 Jul 2019 12:55:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727215AbfGXMz3 (ORCPT ); Wed, 24 Jul 2019 08:55:29 -0400 Received: from mx1.redhat.com ([209.132.183.28]:53240 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726550AbfGXMz2 (ORCPT ); Wed, 24 Jul 2019 08:55:28 -0400 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 56E84300C72E; Wed, 24 Jul 2019 12:55:28 +0000 (UTC) Received: from treble (ovpn-122-90.rdu2.redhat.com [10.10.122.90]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 490975D9DE; Wed, 24 Jul 2019 12:55:27 +0000 (UTC) Date: Wed, 24 Jul 2019 07:55:25 -0500 From: Josh Poimboeuf To: Peter Zijlstra Cc: Thomas Gleixner , LKML , Nick Desaulniers , Nathan Chancellor , clang-built-linux , x86@kernel.org, Arnd Bergmann , Sedat Dilek , Linus Torvalds Subject: Re: x86 - clang / objtool status Message-ID: <20190724125525.kgybu3nnpvwlcz2c@treble> References: <20190724023946.yxsz5im22fz4zxrn@treble> <20190724074732.GJ3402@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20190724074732.GJ3402@hirez.programming.kicks-ass.net> User-Agent: NeoMutt/20180716 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.45]); Wed, 24 Jul 2019 12:55:28 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 24, 2019 at 09:47:32AM +0200, Peter Zijlstra wrote: > On Tue, Jul 23, 2019 at 09:43:24PM -0500, Josh Poimboeuf wrote: > > On Thu, Jul 18, 2019 at 10:40:09PM +0200, Thomas Gleixner wrote: > > > > > drivers/gpu/drm/i915/gem/i915_gem_execbuffer.o: warning: objtool: .altinstr_replacement+0x86: redundant UACCESS disable > > > > Looking at this one, I think I agree with objtool. > > > > PeterZ, Linus, I know y'all discussed this code a few months ago. > > > > __copy_from_user() already does a CLAC in its error path. So isn't the > > user_access_end() redundant for the __copy_from_user() error path? > > Hmm, is this a result of your c705cecc8431 ("objtool: Track original function across branches") ? > > I'm thinking it might've 'overlooked' the CLAC in the error path before > (because it didn't have a related function) and now it sees it and > worries about it. > > Then again, I'm not seeing this warning on my GCC builds; so what's > happening? According to the github issue[1] my patch doesn't fix the warning with Clang. So questions remain: a) what is objtool actually warning about? b) why doesn't objtool detect the case I found? I can look at it later, post-meetings. [1] https://github.com/ClangBuiltLinux/linux/issues/617 -- Josh