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=-17.4 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_IN_DEF_DKIM_WL 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 EE1E9C433DF for ; Tue, 18 Aug 2020 18:00:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AD4A920674 for ; Tue, 18 Aug 2020 18:00:21 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="TT3Hlsrs" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726634AbgHRSAU (ORCPT ); Tue, 18 Aug 2020 14:00:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57386 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726552AbgHRSAS (ORCPT ); Tue, 18 Aug 2020 14:00:18 -0400 Received: from mail-pl1-x644.google.com (mail-pl1-x644.google.com [IPv6:2607:f8b0:4864:20::644]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7D79BC061342 for ; Tue, 18 Aug 2020 11:00:14 -0700 (PDT) Received: by mail-pl1-x644.google.com with SMTP id t10so9565150plz.10 for ; Tue, 18 Aug 2020 11:00:14 -0700 (PDT) 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=nyB4pRDJBveesx+DUtW+5ZFcTskYb5n8BU0PlbnfnQk=; b=TT3Hlsrs/mu4UmXylL6i2vWT4k+JLUcPQy0IRWK10ixwQ9fyS+vI5f6d+uD2IXXZut 99X3OASTGInBitChHeiKlVI5wOVCENDYDya36/FbtT554wJijmw4ooB+ZKooD3AjcKgb w6MKTqNMRCGTA3dEtt2eCr/WXTblLpK6Rb2TkfyM/DzcCUvZGTwzSr4PGl2GjXFrhoGH PDfpG64lJbCoStDn2RPM99hNimcioeWRNNRchqnwjTxrLhGbdfKJfyhVb6Ts5/Mpf008 gQ9Ee5zCntT/sLejF/FVfDbLbexG4avEfhBvuNi13cZq4EZM/tI59HJpPZ1of8yIo5zo 6mOw== 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=nyB4pRDJBveesx+DUtW+5ZFcTskYb5n8BU0PlbnfnQk=; b=QfA2Z8TzwaFc93wrQKxKYPpBhUlKAPRPmcFWlrwaJlZ79rR93W23kBojb4v2V5HEkv l+ObUAFEauRjpHeEQ0mVBHEQkVfiuwSUNttu9ADNSvnvwUk33hGVOQpKbyq0dcvNdBYi 2dm1V/hbDp/gZU3KNCHCeVuR9n3kd6jRWIsLaDj9lOokO6QmpuCpM2sjcoXdJCEm2mDC sDbpH1/IkIGSA+S4memy0e5osH9U7wlcfHaDoyn31TamwjNncX8Orzd+WYuRhrgKMMq7 B5nnUGnR4hlusf5vsDB2lue3oG4iLPlzQh6g4xVDodcchSgIzGAcddZgty/33vW9hBvh NuKQ== X-Gm-Message-State: AOAM533fEUXTzPkahb4U2ieGG6UWPXhZtfR3q92ByKfLNmJEMY4x90Ut AMGRrnDpru568Hru56bmhbEqypKIWVt08/AyMpMsdA== X-Google-Smtp-Source: ABdhPJxvC+Goaa7jQZI2Ls91WkQiWwleNdpeUsQ3EPcOTKvrXorm4E3fZCHGEvi7vIDZCxyOO7u0zSwMWNL8i9JW9RE= X-Received: by 2002:a17:90a:3ad1:: with SMTP id b75mr846390pjc.25.1597773612681; Tue, 18 Aug 2020 11:00:12 -0700 (PDT) MIME-Version: 1.0 References: <20200817220212.338670-1-ndesaulniers@google.com> <20200817220212.338670-3-ndesaulniers@google.com> <20200818054428.GA2540870@ubuntu-n2-xlarge-x86> In-Reply-To: <20200818054428.GA2540870@ubuntu-n2-xlarge-x86> From: Nick Desaulniers Date: Tue, 18 Aug 2020 11:00:01 -0700 Message-ID: Subject: Re: [PATCH 2/4] Revert "lib/string.c: implement a basic bcmp" To: Nathan Chancellor Cc: Masahiro Yamada , Andrew Morton , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Michal Marek , Linux Kbuild mailing list , LKML , Kees Cook , Tony Luck , Dmitry Vyukov , Michael Ellerman , Joe Perches , Joel Fernandes , Daniel Axtens , Arvind Sankar , Andy Shevchenko , Alexandru Ardelean , Yury Norov , "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" , "H . Peter Anvin" , Ard Biesheuvel , "Paul E . McKenney" , Daniel Kiper , Bruce Ashfield , Marco Elver , Vamshi K Sthambamkadi , Andi Kleen , Linus Torvalds , =?UTF-8?B?RMOhdmlkIEJvbHZhbnNrw70=?= , Eli Friedman Content-Type: text/plain; charset="UTF-8" Sender: linux-kbuild-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kbuild@vger.kernel.org On Mon, Aug 17, 2020 at 10:44 PM Nathan Chancellor wrote: > > On Mon, Aug 17, 2020 at 03:02:10PM -0700, Nick Desaulniers wrote: > > This reverts commit 5f074f3e192f10c9fade898b9b3b8812e3d83342. > > > > Use `-fno-builtin-bcmp` instead. > > > > The issue with using `-fno-builtin-*` flags was that they were not > > retained during an LTO link with LLVM. This was fixed in clang-11 by > > https://reviews.llvm.org/D71193 > > (0508c994f0b14144041f2cfd3ba9f9a80f03de08), which is also the minimum > > supported version of clang for LTO. > > > > Signed-off-by: Nick Desaulniers > > --- > > Makefile | 1 + > > include/linux/string.h | 3 --- > > lib/string.c | 20 -------------------- > > 3 files changed, 1 insertion(+), 23 deletions(-) > > > > diff --git a/Makefile b/Makefile > > index 211a1b6f6478..722ff5864275 100644 > > --- a/Makefile > > +++ b/Makefile > > @@ -964,6 +964,7 @@ endif > > # to provide implementations of these routines, then prevent the compiler from > > # emitting calls to what will be undefined symbols. > > KBUILD_CFLAGS += -fno-builtin-stpcpy > > +KBUILD_CFLAGS += -fno-builtin-bcmp > > I personally think that this hunk should be its own patch before this > one then have this patch just be the revert, that way there is no > regression across a bisect (if one were to ever occur) and so the revert > is a straight 'git revert', rather than have something else mixed in > that requires reading the actual changelog text. > > No objections if you disagree though. That's a great idea. I considered it before sending, but I think it would be interesting to divorce the KBUILD changes which can be picked up quickly from the latter changes. Will send a V2. > > > # include additional Makefiles when needed > > include-y := scripts/Makefile.extrawarn > > diff --git a/include/linux/string.h b/include/linux/string.h > > index b1f3894a0a3e..f3bdb74bc230 100644 > > --- a/include/linux/string.h > > +++ b/include/linux/string.h > > @@ -155,9 +155,6 @@ extern void * memscan(void *,int,__kernel_size_t); > > #ifndef __HAVE_ARCH_MEMCMP > > extern int memcmp(const void *,const void *,__kernel_size_t); > > #endif > > -#ifndef __HAVE_ARCH_BCMP > > -extern int bcmp(const void *,const void *,__kernel_size_t); > > -#endif > > #ifndef __HAVE_ARCH_MEMCHR > > extern void * memchr(const void *,int,__kernel_size_t); > > #endif > > diff --git a/lib/string.c b/lib/string.c > > index 6012c385fb31..69328b8353e1 100644 > > --- a/lib/string.c > > +++ b/lib/string.c > > @@ -922,26 +922,6 @@ __visible int memcmp(const void *cs, const void *ct, size_t count) > > EXPORT_SYMBOL(memcmp); > > #endif > > > > -#ifndef __HAVE_ARCH_BCMP > > -/** > > - * bcmp - returns 0 if and only if the buffers have identical contents. > > - * @a: pointer to first buffer. > > - * @b: pointer to second buffer. > > - * @len: size of buffers. > > - * > > - * The sign or magnitude of a non-zero return value has no particular > > - * meaning, and architectures may implement their own more efficient bcmp(). So > > - * while this particular implementation is a simple (tail) call to memcmp, do > > - * not rely on anything but whether the return value is zero or non-zero. > > - */ > > -#undef bcmp > > -int bcmp(const void *a, const void *b, size_t len) > > -{ > > - return memcmp(a, b, len); > > -} > > -EXPORT_SYMBOL(bcmp); > > -#endif > > - > > #ifndef __HAVE_ARCH_MEMSCAN > > /** > > * memscan - Find a character in an area of memory. > > -- > > 2.28.0.220.ged08abb693-goog > > > > Cheers, > Nathan -- Thanks, ~Nick Desaulniers