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=-5.5 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 9E9DDC433DF for ; Thu, 14 May 2020 13:14:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6E868206DA for ; Thu, 14 May 2020 13:14:34 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="iZ8lBoHl" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727123AbgENNOd (ORCPT ); Thu, 14 May 2020 09:14:33 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51892 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1726056AbgENNOd (ORCPT ); Thu, 14 May 2020 09:14:33 -0400 Received: from merlin.infradead.org (unknown [IPv6:2001:8b0:10b:1231::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BF76BC061A0C for ; Thu, 14 May 2020 06:14:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=K4yRXfBE6Kumf0RteQ59RKHAoo/xaI0w9/3Qtk/InMg=; b=iZ8lBoHlXLdkxFqPbB/Agxm8ix 31/ut5izgfIci1Z70gYmMDgmrpmqo7bvkQdNZaTS+FKx+uN+3eayh5YxRN8tJOGrdm+xCzHCymb2b iWNd5G2YghcIsXBKQnEnd1WF3KiRD6blxpU1RkU+oOU7P4oXp/zA+1ufUCBZPoKeKlLHy169l3Rub j4H6OTw1LGWREw324FnMstFtyTIHx8PuOx+jHEGO1uoFwJNlp6N4Q3Ewj9Xbg3n97c46FEVl17AHJ 6L18sdVhZCWMztkJ2SQUakG+kWhZMFsiuR2yJv3Q9MtxpEWHCekEizukILUqkFNkeZJVUaGdY1Bv+ I6v+h4sA==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jZDgj-0007lq-OX; Thu, 14 May 2020 13:14:13 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 556163007CD; Thu, 14 May 2020 15:14:12 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 3C7E4213C8B61; Thu, 14 May 2020 15:14:12 +0200 (CEST) Date: Thu, 14 May 2020 15:14:12 +0200 From: Peter Zijlstra To: Marco Elver Cc: Will Deacon , LKML , Thomas Gleixner , "Paul E. McKenney" , Ingo Molnar , Dmitry Vyukov Subject: Re: [PATCH v5 00/18] Rework READ_ONCE() to improve codegen Message-ID: <20200514131412.GP2957@hirez.programming.kicks-ass.net> References: <20200513123243.GO2957@hirez.programming.kicks-ass.net> <20200513124021.GB20278@willie-the-truck> <20200513132440.GN2978@hirez.programming.kicks-ass.net> <20200514112142.GV2978@hirez.programming.kicks-ass.net> <20200514120104.GD4280@willie-the-truck> <20200514122735.GW2978@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 14, 2020 at 03:07:08PM +0200, Marco Elver wrote: > On Thu, 14 May 2020 at 14:27, Peter Zijlstra wrote: > > > > On Thu, May 14, 2020 at 01:01:04PM +0100, Will Deacon wrote: > > > > > > +#if __has_feature(undefined_sanitizer) > > > > > > Hmm, this might want to be __has_feature(undefined_behavior_sanitizer) > > > (and damn is that hard for a Brit to type out!) > > > > (I know right, it should be behaviour, dammit!) > > > > I tried without the condition, eg.: > > > > +#define __no_sanitize_undefined \ > > + __attribute__((no_sanitize("undefined"))) > > > > and it still generated UBSAN gunk. > > Which ubsan calls are left? I'm trying to reproduce. To be more precise, the patches were on top of: git://git.kernel.org/pub/scm/linux/kernel/git/tglx/devel.git entry-v5-the-rest $ grep ubsan poke_int3_handler-clang10.asm 0074 74: R_X86_64_PLT32 __ubsan_handle_load_invalid_value-0x4 0083 83: R_X86_64_PLT32 __ubsan_handle_load_invalid_value-0x4 01c5 1c5: R_X86_64_PLT32 __ubsan_handle_builtin_unreachable-0x4 I think the config was defconfig_x86-64 inspired with KASAN+UBSAN enabled. So I build with: touch arch/x86/kernel/alterantive.c; make CC=clang-10 V=1 O=defconfig-build/ arch/x86/kernel/alterantive.o And then dump the output with: ./objdump-func.sh defconfig-build/arch/x86/kernel/alterantive.o poke_int3_handler $ # cat objdump-func.sh #!/bin/bash objdump -dr $1 | awk "/^\$/ { P=0; } /$2[^>]*>:\$/ { P=1; O=strtonum(\"0x\" \$1); } { if (P) { o=strtonum(\"0x\" \$1); printf(\"%04x \", o-O); print \$0; } }" Hope that is enough to reproduce.