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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4C5B7C352A1 for ; Wed, 7 Dec 2022 18:36:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229545AbiLGSgX (ORCPT ); Wed, 7 Dec 2022 13:36:23 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48238 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229522AbiLGSgU (ORCPT ); Wed, 7 Dec 2022 13:36:20 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CDB9EBC98 for ; Wed, 7 Dec 2022 10:36:19 -0800 (PST) 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 dfw.source.kernel.org (Postfix) with ESMTPS id 521DB61BB9 for ; Wed, 7 Dec 2022 18:36:19 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 47F1DC43145; Wed, 7 Dec 2022 18:36:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1670438178; bh=mBPLiRISW0j7Pl/OFYZmohWGPJReABYEkzxR6WmqBYQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ufwhSZjyJJnVTmUA5mtv98p92WGFST+2vs82VtZpd7+fCCG1+/Vry1VOEeJv5LrL6 s+4/DnwX5i1Aufmq6qwZyVqovM81GDv364cZ+EWEWEJ9hkbiWakMiBOPL7O1Bgq88T Qy14j78uPCARrtjS45C0rjlwxUA//owOI9KNAZWzOn12GMPxfsu39TOxU/UWxI5McC 6nUARdPjKBdrTN3UdiJBHZ5i4/JRSCYL9K/uagQi7OuAFSdH0/JUjkvgeig6ESNQ0h uKyI51XVu++KNHqi99Vi0OyuJsUYM0KLgrpTiCMSQz7310gCgBtCoMESs/tfppqjdm mcC8RVNUVCh1g== Date: Wed, 7 Dec 2022 11:36:16 -0700 From: Nathan Chancellor To: Mikhail Zhilkin Cc: Miquel Raynal , kernel test robot , llvm@lists.linux.dev, oe-kbuild-all@lists.linux.dev, linux-kernel@vger.kernel.org, NOGUCHI Hiroshi Subject: Re: ld.lld: error: undefined symbol: __udivdi3 Message-ID: References: <202212010140.pIueEBNb-lkp@intel.com> <20221201091610.524f7786@xps-13> <20221201171331.42f05097@xps-13> <4999a9ee-ba08-6e4c-a1d1-074687f82d5e@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <4999a9ee-ba08-6e4c-a1d1-074687f82d5e@gmail.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Dec 07, 2022 at 09:32:41PM +0300, Mikhail Zhilkin wrote: > Hi Nathan, > > On 12/6/2022 8:03 PM, Nathan Chancellor wrote: > > > Hi Mikhail, > > > > First and foremost, apologies for the delay in my response! > > > > On Thu, Dec 01, 2022 at 09:39:22PM +0300, Mikhail Zhilkin wrote: > >> Hi Miquèl, Nathan, > >> > >> On 12/1/2022 7:13 PM, Miquel Raynal wrote: > >>> Hi Nathan, > >>> > >>> nathan@kernel.org wrote on Thu, 1 Dec 2022 09:00:57 -0700: > >>> > >>>> On Thu, Dec 01, 2022 at 09:16:10AM +0100, Miquel Raynal wrote: > >>>>> Hi Mikhail, Hiroshi, > >>>>> > >>>>> lkp@intel.com wrote on Thu, 1 Dec 2022 01:46:36 +0800: > >>>>> > >>>>>> tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master > >>>>>> head: 01f856ae6d0ca5ad0505b79bf2d22d7ca439b2a1 > >>>>>> commit: 9b78ef0c7997052e9eaa0f7a4513d546fa17358c mtd: parsers: add support for Sercomm partitions > >>>>>> date: 6 months ago > >>>>>> config: mips-randconfig-r033-20221128 > >>>>>> compiler: clang version 16.0.0 (https://github.com/llvm/llvm-project 6e4cea55f0d1104408b26ac574566a0e4de48036) > >>>>>> reproduce (this is a W=1 build): > >>>>>> wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross > >>>>>> chmod +x ~/bin/make.cross > >>>>>> # install mips cross compiling tool for clang build > >>>>>> # apt-get install binutils-mipsel-linux-gnu > >>>>>> # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=9b78ef0c7997052e9eaa0f7a4513d546fa17358c > >>>>>> git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git > >>>>>> git fetch --no-tags linus master > >>>>>> git checkout 9b78ef0c7997052e9eaa0f7a4513d546fa17358c > >>>>>> # save the config file > >>>>>> mkdir build_dir && cp config build_dir/.config > >>>>>> COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=mips SHELL=/bin/bash > >>>>>> > >>>>>> If you fix the issue, kindly add following tag where applicable > >>>>>> | Reported-by: kernel test robot > >>>>>> > >>>>>> All errors (new ones prefixed by >>): > >>>>>> > >>>>>>>> ld.lld: error: undefined symbol: __udivdi3 > >>>>>> >>> referenced by scpart.c > >>>>>> >>> mtd/parsers/scpart.o:(scpart_parse) in archive drivers/built-in.a > >>>>>> > >>>>> Can you please try to reproduce this with a mips toolchain as advised > >>>>> and send a fix? > >>>> For what it's worth, this is likely our bug: > >>>> > >>>> https://github.com/ClangBuiltLinux/linux/issues/1635 > >>>> > >>>> It sounds like there are some merged LLVM patches that should help but I > >>>> guess not based on this report... > >>> Ah, yeah, thanks a lot for the share. > >>> > >>> Cheers, Miquèl > >> I could reproduce the issue and found that reference to __udivdi3 > >> appears in this function: > >> > >> static uint32_t scpart_desc_is_valid(struct sc_part_desc *pdesc) > >> { > >> return ((pdesc->part_id != 0xffffffffUL) && > >> (pdesc->part_offs != 0xffffffffUL) && > >> (pdesc->part_bytes != 0xffffffffUL)); > >> } > >> > >> There is no LLVM compiler error if: > >> > >> static uint32_t scpart_desc_is_valid(struct sc_part_desc *pdesc) > >> { > >> return (0); > >> } > >> > >> Currently I have no ideas where does __udivdi3 come from, because > >> there's no division here. Should I try to rewrite somehow the function > >> to avoid the error? > >> I would greatly appreciate any ideas. > > I do not think it is that function that is causing the problem. Making > > it return zero just causes the code generation to change enough to avoid > > this issue. > > > > Based on the previous analysis and reduction [1], LLVM is transforming > > the for loop in scpart_scan_partmap() into division; you can verify this > > by commenting it out some way then rebuilding and running 'readelf -s' > > to look for __udivdi3. > > > > Arnd suggested working around this problem by making offs a 32-bit type, > > as it is already bounded by ->erasesize, which appears to be a 32-bit > > value from what I can tell. Making a change like so appears to resolve > > the issue for me but I am not sure if that has any other implications. > > > > diff --git a/drivers/mtd/parsers/scpart.c b/drivers/mtd/parsers/scpart.c > > index 02601bb33de4..6e5e11c37078 100644 > > --- a/drivers/mtd/parsers/scpart.c > > +++ b/drivers/mtd/parsers/scpart.c > > @@ -50,7 +50,7 @@ static int scpart_scan_partmap(struct mtd_info *master, loff_t partmap_offs, > > int cnt = 0; > > int res = 0; > > int res2; > > - loff_t offs; > > + uint32_t offs; > > size_t retlen; > > struct sc_part_desc *pdesc = NULL; > > struct sc_part_desc *tmpdesc; > > > > [1]: https://github.com/ClangBuiltLinux/linux/issues/1635 > > Many thanks for your time and very clear explanation! > > I've made compile and run tests. It seems that have the working > workaround and I'm going to send the patch. After analyzing the code, I > don't expect any other implications. > > Who should I add to Suggested-by of the patch: You or maybe Arndt? I think Arnd should be the suggested-by on that patch, you should be able to get his info from either MAINTAINERS or git log. Thanks for taking a look and sending a patch! Cheers, Nathan