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=-8.3 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_IN_DEF_DKIM_WL 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 A4EF9C43215 for ; Fri, 22 Nov 2019 15:48:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7005B20748 for ; Fri, 22 Nov 2019 15:48:34 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="GNOwZ31n" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727207AbfKVPsd (ORCPT ); Fri, 22 Nov 2019 10:48:33 -0500 Received: from mail-ot1-f67.google.com ([209.85.210.67]:41837 "EHLO mail-ot1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727112AbfKVPsc (ORCPT ); Fri, 22 Nov 2019 10:48:32 -0500 Received: by mail-ot1-f67.google.com with SMTP id 94so6535336oty.8 for ; Fri, 22 Nov 2019 07:48:31 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=VoLw4CussgMLLZxAWl96Nmphb4wWEeXh0ad0ursaGQc=; b=GNOwZ31nRkkRtCObNuW1iTtfgqFs92bLcrWVBnJDrDrWXxmhu5jHB1W3qmVloZkxvv I7lirUZJKHODNPKD8Lnhi1ZLbKVQi7hxFaJzn/8+1mFtnqWsCvgnOwcKT0a6fk0Mla7C lx72owbQ9FRTQQcHSyruPmj48sUfj0BaZnq2eCQ8XSe/1cCVnNtF2jxyft38Pdxbwy+D BsjLNJnCvMgH+MyHNHBALbAnxXC3D5Hk0RwttL4/6f2iEN6bso1fq9MkYaIS8VQwNkNR HrqaQ3hAl2JuwpjiD912NpJ2AAxN7ZNLl0ehoc2hXpCxpqDZWuMounqR9hupqFGVoJC5 3kmw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=VoLw4CussgMLLZxAWl96Nmphb4wWEeXh0ad0ursaGQc=; b=Em+Zc7ODyUc4Cdoo5RF8RkCImUWhO1/+rMSwqZJ418Qg/LqWul4pSm7lJzOfWmROhJ yL5wPQo++riCzDwdYmwM36K5rAncVTxcHnAuw6byIXqQGltBpdMVbR+dyW8nhps3+aU8 hvZhD7HFXiv1qy/8M9xZxuXkMMGIxa7XzhLDwxisYywXWxbWhpEvovzEmeycCHZb9PQY x7xABhCGtiihRYH0Q7P0krboKw6yj4064uH+Dxcc9EyE6mveTf+mWGVQieaKSh14dtlk 8gaV0C9ife53JpYo8aK+t0+lb56k04GJi6JdqCAK5q3Gol0TQjA59/SKqTjwv228LyiB fdTA== X-Gm-Message-State: APjAAAU8txuNFuTFvYUbfu8eWtNJK4UGSvowH2Rfo6ZIm7PgHuwF30I/ QqmpIxLgIanzEkVGGkFgtbgU+Pf0pLkcaAvzRvQDbNDaw4FfTiE0 X-Google-Smtp-Source: APXvYqzm/YERgO6yBcRziIJSES+wmUAc8m20DC+ayxZKVrwIy53nf8oLq6Ni05wdArtcO9BBvTQUv0BZID2e1YEgGdE= X-Received: by 2002:a9d:82e:: with SMTP id 43mr11609145oty.23.1574437711101; Fri, 22 Nov 2019 07:48:31 -0800 (PST) MIME-Version: 1.0 References: <20191120203434.2a0727b3@canb.auug.org.au> <58708908-84a0-0a81-a836-ad97e33dbb62@infradead.org> <20191121183711.w2qnysscwnbxocc4@treble> In-Reply-To: From: Marco Elver Date: Fri, 22 Nov 2019 16:48:20 +0100 Message-ID: Subject: Re: linux-next: Tree for Nov 20 (kcsan + objtool) To: Josh Poimboeuf Cc: Randy Dunlap , Stephen Rothwell , Linux Next Mailing List , Linux Kernel Mailing List , Dmitry Vyukov , "Paul E. McKenney" , Peter Zijlstra Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 21 Nov 2019 at 19:43, Marco Elver wrote: > > On Thu, 21 Nov 2019 at 19:37, Josh Poimboeuf wrote: > > > > On Wed, Nov 20, 2019 at 08:48:41PM +0100, Marco Elver wrote: > > > On Wed, 20 Nov 2019 at 17:18, Randy Dunlap wrote: > > > > > > > > On 11/20/19 1:34 AM, Stephen Rothwell wrote: > > > > > Hi all, > > > > > > > > > > Changes since 20191119: > > > > > > > > > > > > > on x86_64: > > > > > > > > kernel/kcsan/core.o: warning: objtool: kcsan_found_watchpoint()+0xa: call to kcsan_is_enabled() with UACCESS enabled > > > > kernel/kcsan/core.o: warning: objtool: __tsan_read1()+0x13: call to find_watchpoint() with UACCESS enabled > > > > kernel/kcsan/core.o: warning: objtool: __tsan_write1()+0x10: call to find_watchpoint() with UACCESS enabled > > > > kernel/kcsan/core.o: warning: objtool: __tsan_read2()+0x13: call to find_watchpoint() with UACCESS enabled > > > > kernel/kcsan/core.o: warning: objtool: __tsan_write2()+0x10: call to find_watchpoint() with UACCESS enabled > > > > kernel/kcsan/core.o: warning: objtool: __tsan_read4()+0x13: call to find_watchpoint() with UACCESS enabled > > > > kernel/kcsan/core.o: warning: objtool: __tsan_write4()+0x10: call to find_watchpoint() with UACCESS enabled > > > > kernel/kcsan/core.o: warning: objtool: __tsan_read8()+0x13: call to find_watchpoint() with UACCESS enabled > > > > kernel/kcsan/core.o: warning: objtool: __tsan_write8()+0x10: call to find_watchpoint() with UACCESS enabled > > > > kernel/kcsan/core.o: warning: objtool: __tsan_read16()+0x13: call to find_watchpoint() with UACCESS enabled > > > > kernel/kcsan/core.o: warning: objtool: __tsan_write16()+0x10: call to find_watchpoint() with UACCESS enabled > > > > kernel/kcsan/core.o: warning: objtool: __tsan_read_range()+0x13: call to find_watchpoint() with UACCESS enabled > > > > kernel/kcsan/core.o: warning: objtool: __tsan_write_range()+0x10: call to find_watchpoint() with UACCESS enabled > > > > > > > > kernel/trace/trace_branch.o: warning: objtool: ftrace_likely_update()+0x361: call to __stack_chk_fail() with UACCESS enabled > > > > > > > > > > > > Full randconfig file is attached. > > > > > > Thanks. > > > > > > This is due to CONFIG_CC_OPTIMIZE_FOR_SIZE=y. It seems the compiler > > > decides to not even inline small static inline functions. I tried to > > > make this go away by adding __always_inline, but then we're also left > > > with atomic64_try_cmpxchg which never gets inlined. > > > > > > The optimized build simply inlines the small static inline functions. > > > We certainly do not want to add more functions to the objtool > > > whitelist, especially those that are private to KCSAN. > > > > > > We could fix it by either: > > > > > > 1. Adding __always_inline to every function used by the KCSAN runtime > > > outside user_access_save + also fix atomic64_try_cmpxchg > > > (atomic-instrumented.h). > > > > > > 2. Just not compile KCSAN with -Os, i.e. have the Makefile strip -Os > > > and replace it with -O2 for kcsan/core.c. #2 is the simpler option, > > > and would probably make KCSAN more effective even with -Os. Although > > > it might violate the assumption of whoever decided they want both > > > CC_OPTIMIZE_FOR_SIZE and KCSAN. It might also mean that future > > > compilers that have a new inlining algorithm will have the same > > > problem. > > > > > > What do people think is better? > > > > I haven't had a chance to look at this yet, and probably won't be able > > to do so until at least Monday... > > > > Adding PeterZ who's the objtool uaccess expert. > > Thanks. I have a patch which does #1, since it's probably cleaner. I > will send it out soon. > > If there is a better way to resolve this, any suggestions welcome. I have sent a patch which addresses the issue: http://lkml.kernel.org/r/20191122154221.247680-1-elver@google.com It is currently based on the locking/kcsan branch of the tip tree. Thanks, -- Marco