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 Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 3528EC433EF for ; Tue, 7 Dec 2021 04:49:46 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4J7SWr3xfPz2ymc for ; Tue, 7 Dec 2021 15:49:44 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20201202 header.b=RbQ3ZQHA; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=kernel.org (client-ip=2604:1380:40e1:4800::1; helo=sin.source.kernel.org; envelope-from=nathan@kernel.org; receiver=) Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20201202 header.b=RbQ3ZQHA; dkim-atps=neutral Received: from sin.source.kernel.org (sin.source.kernel.org [IPv6:2604:1380:40e1:4800::1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4J7SW35hHZz2xsk for ; Tue, 7 Dec 2021 15:49:03 +1100 (AEDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by sin.source.kernel.org (Postfix) with ESMTPS id 14979CE1986; Tue, 7 Dec 2021 04:49:00 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 21BF7C341C3; Tue, 7 Dec 2021 04:48:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1638852538; bh=kWUuj+zOg/J02GtTQgtuWReq1jyPVZsr2EvNQ5UNSHs=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=RbQ3ZQHALMekthGD2NZcluVBv3lEnakzWAdlJnF5qWF29VlNcYtdEw7H2wkkY+pRC JkLeNqvcujhOIiMjFFEktBOpyRk44ayhVRRCfyeiyDwHjTINSINNeRrdlHffISLn81 fCT/0J3X3C/FWksXbgcNJdRL1cvfnZxt2lA2sWhltmnpMeRVNIG+iaJEQ17BWeQxUa MCBIgdfE3Y42+LgFyKEJOHmpLezftQeQy9QYH09ZJLBDrI6tewkO5+UP6UoOSyioRz akcipFJEuzvHo8HOZS380dYgS/Mwui83HW6miCZdBvvDybrNUBkgwG6uGzb1peuID3 /bbGD9YmsmRwg== Date: Mon, 6 Dec 2021 21:48:52 -0700 From: Nathan Chancellor To: Michael Ellerman Subject: Re: [PATCH v5 5/5] powerpc/inst: Optimise copy_inst_from_kernel_nofault() Message-ID: References: <0d5b12183d5176dd702d29ad94c39c384e51c78f.1638208156.git.christophe.leroy@csgroup.eu> <202111300652.0yDBNvyJ-lkp@intel.com> <87a6hlq408.fsf@mpe.ellerman.id.au> <87o85tnkzt.fsf@mpe.ellerman.id.au> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <87o85tnkzt.fsf@mpe.ellerman.id.au> X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kbuild-all@lists.01.org, kernel test robot , llvm@lists.linux.dev, Nick Desaulniers , linux-kernel@vger.kernel.org, Paul Mackerras , Bill Wendling , linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Tue, Dec 07, 2021 at 02:37:26PM +1100, Michael Ellerman wrote: > Bill Wendling writes: > > On Tue, Nov 30, 2021 at 10:38 AM Bill Wendling wrote: > >> On Tue, Nov 30, 2021 at 10:17 AM Nathan Chancellor wrote: > >> > On Tue, Nov 30, 2021 at 10:25:43PM +1100, Michael Ellerman wrote: > >> > > Christophe Leroy writes: > >> > > > Le 29/11/2021 à 23:55, kernel test robot a écrit : > ... > >> > > >> All warnings (new ones prefixed by >>): > >> > > >> > >> > > >> In file included from arch/powerpc/kernel/asm-offsets.c:71: > >> > > >> In file included from arch/powerpc/kernel/../xmon/xmon_bpts.h:7: > >> > > >>>> arch/powerpc/include/asm/inst.h:165:20: warning: variable 'val' is uninitialized when used here [-Wuninitialized] > >> > > >> *inst = ppc_inst(val); > >> > > >> ^~~ > >> > > >> arch/powerpc/include/asm/inst.h:53:22: note: expanded from macro 'ppc_inst' > >> > > >> #define ppc_inst(x) (x) > >> > > >> ^ > >> > > >> arch/powerpc/include/asm/inst.h:155:18: note: initialize the variable 'val' to silence this warning > >> > > >> unsigned int val, suffix; > >> > > >> ^ > >> > > >> = 0 > >> > > > > >> > > > I can't understand what's wrong here. > ... > >> > > > > >> > > > I see no possibility, no alternative path where val wouldn't be set. The > >> > > > asm clearly has *addr as an output param so it is always set. > >> > > > >> > > I guess clang can't convince itself of that? > ... > >> > > >> > It certainly looks like there is something wrong with how clang is > >> > tracking the initialization of the variable because it looks to me like > >> > val is only used in the fallthrough path, which happens after it is > >> > initialized via lwz. Perhaps something is wrong with the logic of > >> > https://reviews.llvm.org/D71314? I've added Bill to CC (LLVM issues are > >> > being migrated from Bugzilla to GitHub Issues right now so I cannot file > >> > this upstream at the moment). > >> > > >> If I remove the casts of "val" the warning doesn't appear. I suspect > >> that when I wrote that patch I forgot to remove those when checking. > >> #include "Captain_Picard_facepalm.h" > >> > >> I'll look into it. > >> > > Small retraction. It's the "*()&val" that's the issue. (I.e. the "*&") > > I guess for now I'll just squash this in as a workaround? > > > diff --git a/arch/powerpc/include/asm/inst.h b/arch/powerpc/include/asm/inst.h > index 631436f3f5c3..5b591c51fec9 100644 > --- a/arch/powerpc/include/asm/inst.h > +++ b/arch/powerpc/include/asm/inst.h > @@ -157,6 +157,9 @@ static inline int copy_inst_from_kernel_nofault(ppc_inst_t *inst, u32 *src) > if (unlikely(!is_kernel_addr((unsigned long)src))) > return -ERANGE; Could we add a version check to this and a link to our bug tracker: /* https://github.com/ClangBuiltLinux/linux/issues/1521 */ #if defined(CONFIG_CC_IS_CLANG) && CONFIG_CLANG_VERSION < 140000 > +#ifdef CONFIG_CC_IS_CLANG > + val = suffix = 0; > +#endif > __get_kernel_nofault(&val, src, u32, Efault); > if (IS_ENABLED(CONFIG_PPC64) && get_op(val) == OP_PREFIX) { > __get_kernel_nofault(&suffix, src + 1, u32, Efault); > > > > cheers