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=-11.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 EF60AC433E0 for ; Fri, 12 Mar 2021 03:39:36 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 7155D64F8E for ; Fri, 12 Mar 2021 03:39:36 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7155D64F8E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id E2FF78D0325; 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a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1615520372; bh=lHfiW1NEp9XSUMcXy/X9S+PfnCdkVuQBQU5g66t4mFc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ngtsOkncEpBDrRVvp1o9eybcnlX7zOe2xboQvEVx9UIAoFGMQUJ9Ot/6xzBiJ4AUV DiG68YpZt8AqSXi2pa7gr1Ov0IazQhj2ibYzeDv5rz9sHJJgWF22wt0HYFk483LFJ0 JKrX7i0VZJexkGVig/YbTsMY2BcynqfS/78wuymslx+df5PfS2bNtG1dohQ1n8dH7X q1abI/Vn1CLND+eisbdUYxW859TFCDCzWZb6bYVz1fc8KFUSw6u7LHQoGKR26BkUK2 Bx5VhtEcHJ3ZRtaWiGRVP2a0Oap/2MlotOnvpQvLlyJm3o0jtdUiz8QHDEdY32VcLa 1axhsumfFhAsw== Date: Thu, 11 Mar 2021 20:39:27 -0700 From: Nathan Chancellor To: Nick Desaulniers Cc: Maximilian Luz , kernel test robot , kbuild-all@lists.01.org, clang-built-linux , Linux Memory Management List , Hans de Goede Subject: Re: [linux-next:master 1430/3917] drivers/platform/surface/surface_aggregator_registry.c:398:25: warning: implicit conversion from 'int' to '__u8' (aka 'unsigned char') changes value from 65535 to 255 Message-ID: <20210312033927.xdxhw57m4lqwxt4p@archlinux-ax161> References: <202103112158.loq4oyJu-lkp@intel.com> <8c252429-5000-0649-c49f-8225d911241b@gmail.com> <20210311185154.6uysryumfho73zlb@archlinux-ax161> <7db15c91-db37-69a4-84b7-6f58cca2ee1b@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: 1ut7s5kwdxp64pxrujrixf6c7aj4bmhs X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 58A74A0000FD Received-SPF: none (kernel.org>: No applicable sender policy available) receiver=imf07; identity=mailfrom; envelope-from=""; helo=mail.kernel.org; client-ip=198.145.29.99 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1615520374-769424 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Mar 11, 2021 at 04:18:59PM -0800, Nick Desaulniers wrote: > On Thu, Mar 11, 2021 at 4:13 PM Maximilian Luz wrote: > > > > On 3/11/21 7:51 PM, Nathan Chancellor wrote: > > > On Thu, Mar 11, 2021 at 02:39:03PM +0100, Maximilian Luz wrote: > > >> On 3/11/21 2:06 PM, kernel test robot wrote: > > >>> tree: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master > > >>> head: 98546348153dee5f8ced572fd6c4690461d20f51 > > >>> commit: 797e78564634275ed4fe6b3f586c4b96eb1d86bc [1430/3917] platform/surface: aggregator_registry: Add base device hub > > >>> config: arm64-randconfig-r026-20210311 (attached as .config) > > >>> compiler: clang version 13.0.0 (https://github.com/llvm/llvm-project 574a9dabc63ba1e7a04c08d4bde2eacd61b44ce1) > > >>> 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 arm64 cross compiling tool for clang build > > >>> # apt-get install binutils-aarch64-linux-gnu > > >>> # https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?id=797e78564634275ed4fe6b3f586c4b96eb1d86bc > > >>> git remote add linux-next https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git > > >>> git fetch --no-tags linux-next master > > >>> git checkout 797e78564634275ed4fe6b3f586c4b96eb1d86bc > > >>> # save the attached .config to linux build tree > > >>> COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=arm64 > > >>> > > >>> If you fix the issue, kindly add following tag as appropriate > > >>> Reported-by: kernel test robot > > >>> > > >>> All warnings (new ones prefixed by >>): > > >>> > > >>> In file included from drivers/platform/surface/surface_aggregator_registry.c:12: > > >>> In file included from include/linux/acpi.h:35: > > >>> In file included from include/acpi/acpi_io.h:7: > > >>> In file included from arch/arm64/include/asm/acpi.h:12: > > >>> include/linux/efi.h:1093:34: warning: passing 1-byte aligned argument to 4-byte aligned parameter 2 of 'get_var' may result in an unaligned pointer access [-Walign-mismatch] > > >>> status = get_var(L"SecureBoot", &EFI_GLOBAL_VARIABLE_GUID, NULL, &size, > > >>> ^ > > >>> include/linux/efi.h:1101:24: warning: passing 1-byte aligned argument to 4-byte aligned parameter 2 of 'get_var' may result in an unaligned pointer access [-Walign-mismatch] > > >>> get_var(L"SetupMode", &EFI_GLOBAL_VARIABLE_GUID, NULL, &size, &setupmode); > > >>> ^ > > >>>>> drivers/platform/surface/surface_aggregator_registry.c:398:25: warning: implicit conversion from 'int' to '__u8' (aka 'unsigned char') changes value from 65535 to 255 [-Wconstant-conversion] > > >>> { SSAM_VDEV(HUB, 0x02, SSAM_ANY_IID, 0x00) }, > > >>> ~ ^~~~~~~~~~~~ > > >> > > >> This is a false positive: > > >> > > >>> include/linux/surface_aggregator/device.h:71:23: note: expanded from macro 'SSAM_ANY_IID' > > >>> #define SSAM_ANY_IID 0xffff > > >>> ^~~~~~ > > >> > > >> Here, clang complains that the input is SSAM_ANY_ID. That is a special > > >> value which has special considerations below. The SSAM_DEVICE() and > > >> thus SSAM_VDEV() macros are intended to only allow either __u8 or > > >> SSAM_ANY_ID as input in this place. > > >> > > >>> include/linux/surface_aggregator/device.h:126:63: note: expanded from macro 'SSAM_VDEV' > > >>> SSAM_DEVICE(SSAM_DOMAIN_VIRTUAL, SSAM_VIRTUAL_TC_##cat, tid, iid, fun) > > >>> ^~~ > > >>> include/linux/surface_aggregator/device.h:102:41: note: expanded from macro 'SSAM_DEVICE' > > >>> .instance = ((iid) != SSAM_ANY_IID) ? (iid) : 0, \ > > >>> ^~~ > > >> > > >> Here is the special handling for SSAM_ANY_ID. So there is an implicit > > >> conversion from iid, which may be __u8, to int (i.e. the type of > > >> SSAM_ANY_ID), but there is at no point any implicit conversion of > > >> SSAM_ANY_ID to __u8, as clang alleges. > > > > > > Looks like we are getting bit by https://llvm.org/pr38789 here (also > > > tracked at https://github.com/ClangBuiltLinux/linux/issues/92). > > > > Thanks for the links! Looks like this is the same issue. > > > > >> Is there any way to silence this warning in particular without > > >> suppressing it (e.g. by explicit casting) when users of this macro > > >> _actually_ input any non-u8 and non-SSAM_ANY_ID value as iid, > > >> leading to an _actual_ implicit value-changing cast? > > > > > > This has been worked around once before, commit b27aca2e555f ("soc: > > > rockchip: work around clang warning"). I am not sure of another way to > > > silence the warning in specific instances like you described aside from > > > just fixing clang (which is obviously the correct solution) so that we > > > will get real warnings. > > > > > > Unfortunately, the patch that is linked in the LLVM PR above does not > > > appear to fix this instance. > > > > So what's the way forward here? Ignore this warning for now and wait for > > the clang team to fix it or find a workaround? > > I think we should fix this on the Clang side; having your additional > test case will help us refine the initial approach. Not the highest > priority for us as this was found via randconfig; if it was something > that showed up for defconfigs for every arch that would help us > reprioritize but at the moment we have a lot of higher priority work. > Either way, I appreciate the effort looking into this 0day bot > warning! Just for the record, this is visible with a regular all{mod,yes}config build but it is just one warning so I tend to agree that it is not the highest priority. Cheers, Nathan > > > > The best workaround I can come up with is setting the match_flags > > parameter directly as macro argument, which would be a bit more verbose > > and feel slightly less clean, but would do the trick. > > > > Also note that any changes to those macros would have to be synchronized > > with a couple of patches which are still out to non-pdx86 trees, so if > > we're working around this it's best to do this as soon as possible. > > Specifically talking to Hans here, as those patches all have a > > dependency on stuff that's only in the pdx86 tree right now. I.e. > > getting the workaround in before setting up a tag for those dependencies > > would simplify things. > > > > Regards, > > Max > > > > > Cheers, > > > Nathan > > > > > >> I believe GCC does get this right and only emits a warning if a > > >> non-u8 _and_ non-SSAM_ANY_ID value is input. > > >> > > >> Regards, > > >> Max > > >> > > >>> 3 warnings generated. > > >>> > > >>> > > >>> vim +398 drivers/platform/surface/surface_aggregator_registry.c > > >>> > > >>> 396 > > >>> 397 static const struct ssam_device_id ssam_base_hub_match[] = { > > >>> > 398 { SSAM_VDEV(HUB, 0x02, SSAM_ANY_IID, 0x00) }, > > >>> 399 { }, > > >>> 400 }; > > >>> 401 > > >>> > > >>> --- > > >>> 0-DAY CI Kernel Test Service, Intel Corporation > > >>> https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org > > >>> > > >> > > > > -- > > You received this message because you are subscribed to the Google Groups "Clang Built Linux" group. > > To unsubscribe from this group and stop receiving emails from it, send an email to clang-built-linux+unsubscribe@googlegroups.com. > > To view this discussion on the web visit https://groups.google.com/d/msgid/clang-built-linux/7db15c91-db37-69a4-84b7-6f58cca2ee1b%40gmail.com. > > > > -- > Thanks, > ~Nick Desaulniers >