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=-11.6 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 77099C4338F for ; Tue, 24 Aug 2021 06:59:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5F51061357 for ; Tue, 24 Aug 2021 06:59:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233360AbhHXHAT (ORCPT ); Tue, 24 Aug 2021 03:00:19 -0400 Received: from mga03.intel.com ([134.134.136.65]:29331 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231292AbhHXHAN (ORCPT ); Tue, 24 Aug 2021 03:00:13 -0400 X-IronPort-AV: E=McAfee;i="6200,9189,10085"; a="217277454" X-IronPort-AV: E=Sophos;i="5.84,346,1620716400"; d="scan'208";a="217277454" Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by orsmga103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 23 Aug 2021 23:59:28 -0700 X-IronPort-AV: E=Sophos;i="5.84,346,1620716400"; d="scan'208";a="526502052" Received: from rongch2-mobl.ccr.corp.intel.com (HELO [10.249.172.62]) ([10.249.172.62]) by fmsmga003-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 23 Aug 2021 23:59:26 -0700 Subject: Re: [kbuild-all] Re: arch/powerpc/kernel/signal_32.c:297:2: warning: Value stored to 'msr' is never read [clang-analyzer-deadcode.DeadStores] To: Christophe Leroy , kernel test robot Cc: clang-built-linux@googlegroups.com, kbuild-all@lists.01.org, linux-kernel@vger.kernel.org, Michael Ellerman References: <202108231827.N9VUIKbD-lkp@intel.com> <3db8de6e-a971-be9f-19eb-e7d95faf2870@csgroup.eu> From: "Chen, Rong A" Message-ID: <7955eec5-c1d7-e0d7-280a-138d96b2daa9@intel.com> Date: Tue, 24 Aug 2021 14:59:24 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Firefox/78.0 Thunderbird/78.12.0 MIME-Version: 1.0 In-Reply-To: <3db8de6e-a971-be9f-19eb-e7d95faf2870@csgroup.eu> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 8/23/2021 10:35 PM, Christophe Leroy wrote: > > > Le 23/08/2021 à 12:59, kernel test robot a écrit : >> tree: >> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master >> head:   e22ce8eb631bdc47a4a4ea7ecf4e4ba499db4f93 >> commit: ef75e73182949a94bde169a774de1b62ae21fbbc powerpc/signal32: >> Transform save_user_regs() and save_tm_user_regs() in 'unsafe' version >> date:   9 months ago >> config: powerpc-randconfig-c003-20210821 (attached as .config) >> compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project >> d9c5613e856cf2addfbf892fc4c1ce9ef9feceaa) >> 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 powerpc cross compiling tool for clang build >>          # apt-get install binutils-powerpc-linux-gnu >>          # >> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ef75e73182949a94bde169a774de1b62ae21fbbc >> >>          git remote add linus >> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git >>          git fetch --no-tags linus master >>          git checkout ef75e73182949a94bde169a774de1b62ae21fbbc >>          # save the attached .config to linux build tree >>          COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross >> ARCH=powerpc clang-analyzer >> >> If you fix the issue, kindly add following tag as appropriate >> Reported-by: kernel test robot >> >> >> clang-analyzer warnings: (new ones prefixed by >>) >>             ^ >>>> arch/powerpc/kernel/signal_32.c:297:2: warning: Value stored to >>>> 'msr' is never read [clang-analyzer-deadcode.DeadStores] >>             msr &= ~MSR_VSX; >>             ^      ~~~~~~~~ >>     arch/powerpc/kernel/signal_32.c:297:2: note: Value stored to 'msr' >> is never read >>             msr &= ~MSR_VSX; >>             ^      ~~~~~~~~ > > > This is wrong. > > msr is used at line 326: > > ef75e73182949a arch/powerpc/kernel/signal_32.c Christophe Leroy > 2020-08-18  326 unsafe_put_user(msr, &frame->mc_gregs[PT_MSR], failed); Hi Christophe, The usage is under CONFIG_VSX, the test config (powerpc-randconfig-c003-20210821) didn't enable it which triggered this warning. Best Regards, Rong Chen > > > > > >>     arch/powerpc/kernel/signal_32.c:765:16: warning: Value stored to >> 'msr' during its initialization is never read >> [clang-analyzer-deadcode.DeadStores] >>             unsigned long msr = regs->msr; >>                           ^~~   ~~~~~~~~~ >>     arch/powerpc/kernel/signal_32.c:765:16: note: Value stored to >> 'msr' during its initialization is never read >>             unsigned long msr = regs->msr; >>                           ^~~   ~~~~~~~~~ >>     arch/powerpc/kernel/signal_32.c:869:16: warning: Value stored to >> 'msr' during its initialization is never read >> [clang-analyzer-deadcode.DeadStores] >>             unsigned long msr = regs->msr; >>                           ^~~   ~~~~~~~~~ >>     arch/powerpc/kernel/signal_32.c:869:16: note: Value stored to >> 'msr' during its initialization is never read >>             unsigned long msr = regs->msr; >>                           ^~~   ~~~~~~~~~ >> >> vim +/msr +297 arch/powerpc/kernel/signal_32.c >> >> 968c4fccd1bb8b arch/powerpc/kernel/signal_32.c Christophe Leroy >> 2020-08-18  262 >> ef75e73182949a arch/powerpc/kernel/signal_32.c Christophe Leroy >> 2020-08-18  263  static int save_user_regs_unsafe(struct pt_regs >> *regs, struct mcontext __user *frame, >> 8d33001dd650b8 arch/powerpc/kernel/signal_32.c Christophe Leroy >> 2020-08-18  264                   struct mcontext __user *tm_frame, >> int ctx_has_vsx_region) >> ^1da177e4c3f41 arch/ppc64/kernel/signal32.c    Linus Torvalds >> 2005-04-16  265  { >> 9e7511861c4f8d arch/powerpc/kernel/signal_32.c Michael Neuling >> 2008-06-25  266      unsigned long msr = regs->msr; >> 9e7511861c4f8d arch/powerpc/kernel/signal_32.c Michael Neuling >> 2008-06-25  267 >> c6e6771b87d4e3 arch/powerpc/kernel/signal_32.c Michael Neuling >> 2008-06-25  268      /* save general registers */ >> ef75e73182949a arch/powerpc/kernel/signal_32.c Christophe Leroy >> 2020-08-18  269      unsafe_save_general_regs(regs, frame, failed); >> ^1da177e4c3f41 arch/ppc64/kernel/signal32.c    Linus Torvalds >> 2005-04-16  270 >> ^1da177e4c3f41 arch/ppc64/kernel/signal32.c    Linus Torvalds >> 2005-04-16  271  #ifdef CONFIG_ALTIVEC >> ^1da177e4c3f41 arch/ppc64/kernel/signal32.c    Linus Torvalds >> 2005-04-16  272      /* save altivec registers */ >> ^1da177e4c3f41 arch/ppc64/kernel/signal32.c    Linus Torvalds >> 2005-04-16  273      if (current->thread.used_vr) { >> ef75e73182949a arch/powerpc/kernel/signal_32.c Christophe Leroy >> 2020-08-18  274          unsafe_copy_to_user(&frame->mc_vregs, >> ¤t->thread.vr_state, >> ef75e73182949a arch/powerpc/kernel/signal_32.c Christophe Leroy >> 2020-08-18  275                      ELF_NVRREG * sizeof(vector128), >> failed); >> ^1da177e4c3f41 arch/ppc64/kernel/signal32.c    Linus Torvalds >> 2005-04-16  276          /* set MSR_VEC in the saved MSR value to >> indicate that >> ^1da177e4c3f41 arch/ppc64/kernel/signal32.c    Linus Torvalds >> 2005-04-16  277             frame->mc_vregs contains valid data */ >> 9e7511861c4f8d arch/powerpc/kernel/signal_32.c Michael Neuling >> 2008-06-25  278          msr |= MSR_VEC; >> ^1da177e4c3f41 arch/ppc64/kernel/signal32.c    Linus Torvalds >> 2005-04-16  279      } >> ^1da177e4c3f41 arch/ppc64/kernel/signal32.c    Linus Torvalds >> 2005-04-16  280      /* else assert((regs->msr & MSR_VEC) == 0) */ >> ^1da177e4c3f41 arch/ppc64/kernel/signal32.c    Linus Torvalds >> 2005-04-16  281 >> ^1da177e4c3f41 arch/ppc64/kernel/signal32.c    Linus Torvalds >> 2005-04-16  282      /* We always copy to/from vrsave, it's 0 if we >> don't have or don't >> ^1da177e4c3f41 arch/ppc64/kernel/signal32.c    Linus Torvalds >> 2005-04-16  283       * use altivec. Since VSCR only contains 32 bits >> saved in the least >> ^1da177e4c3f41 arch/ppc64/kernel/signal32.c    Linus Torvalds >> 2005-04-16  284       * significant bits of a vector, we "cheat" and >> stuff VRSAVE in the >> ^1da177e4c3f41 arch/ppc64/kernel/signal32.c    Linus Torvalds >> 2005-04-16  285       * most significant bits of that same vector. --BenH >> 408a7e08b2112f arch/powerpc/kernel/signal_32.c Paul Mackerras >> 2013-08-05  286       * Note that the current VRSAVE value is in the >> SPR at this point. >> ^1da177e4c3f41 arch/ppc64/kernel/signal32.c    Linus Torvalds >> 2005-04-16  287       */ >> ef75e73182949a arch/powerpc/kernel/signal_32.c Christophe Leroy >> 2020-08-18  288      unsafe_put_user(current->thread.vrsave, (u32 >> __user *)&frame->mc_vregs[32], >> ef75e73182949a arch/powerpc/kernel/signal_32.c Christophe Leroy >> 2020-08-18  289              failed); >> ^1da177e4c3f41 arch/ppc64/kernel/signal32.c    Linus Torvalds >> 2005-04-16  290  #endif /* CONFIG_ALTIVEC */ >> ef75e73182949a arch/powerpc/kernel/signal_32.c Christophe Leroy >> 2020-08-18  291      unsafe_copy_fpr_to_user(&frame->mc_fregs, >> current, failed); >> ec67ad82814bee arch/powerpc/kernel/signal_32.c Michael Neuling >> 2013-11-25  292 >> ec67ad82814bee arch/powerpc/kernel/signal_32.c Michael Neuling >> 2013-11-25  293      /* >> ec67ad82814bee arch/powerpc/kernel/signal_32.c Michael Neuling >> 2013-11-25  294       * Clear the MSR VSX bit to indicate there is no >> valid state attached >> ec67ad82814bee arch/powerpc/kernel/signal_32.c Michael Neuling >> 2013-11-25  295       * to this context, except in the specific case >> below where we set it. >> ec67ad82814bee arch/powerpc/kernel/signal_32.c Michael Neuling >> 2013-11-25  296       */ >> ec67ad82814bee arch/powerpc/kernel/signal_32.c Michael Neuling >> 2013-11-25 @297      msr &= ~MSR_VSX; >> 6a274c08f2f4df arch/powerpc/kernel/signal_32.c Michael Neuling >> 2008-07-02  298  #ifdef CONFIG_VSX >> ce48b2100785e5 arch/powerpc/kernel/signal_32.c Michael Neuling >> 2008-06-25  299      /* >> ce48b2100785e5 arch/powerpc/kernel/signal_32.c Michael Neuling >> 2008-06-25  300       * Copy VSR 0-31 upper half from thread_struct to >> local >> ce48b2100785e5 arch/powerpc/kernel/signal_32.c Michael Neuling >> 2008-06-25  301       * buffer, then write that to userspace.  Also >> set MSR_VSX in >> ce48b2100785e5 arch/powerpc/kernel/signal_32.c Michael Neuling >> 2008-06-25  302       * the saved MSR value to indicate that >> frame->mc_vregs >> ce48b2100785e5 arch/powerpc/kernel/signal_32.c Michael Neuling >> 2008-06-25  303       * contains valid data >> ce48b2100785e5 arch/powerpc/kernel/signal_32.c Michael Neuling >> 2008-06-25  304       */ >> 16c29d180becc5 arch/powerpc/kernel/signal_32.c Michael Neuling >> 2008-10-23  305      if (current->thread.used_vsr && >> ctx_has_vsx_region) { >> ef75e73182949a arch/powerpc/kernel/signal_32.c Christophe Leroy >> 2020-08-18  306          unsafe_copy_vsx_to_user(&frame->mc_vsregs, >> current, failed); >> ce48b2100785e5 arch/powerpc/kernel/signal_32.c Michael Neuling >> 2008-06-25  307          msr |= MSR_VSX; >> ec67ad82814bee arch/powerpc/kernel/signal_32.c Michael Neuling >> 2013-11-25  308      } >> c6e6771b87d4e3 arch/powerpc/kernel/signal_32.c Michael Neuling >> 2008-06-25  309  #endif /* CONFIG_VSX */ >> 81e7009ea46c95 arch/powerpc/kernel/signal_32.c Stephen Rothwell >> 2005-10-18  310  #ifdef CONFIG_SPE >> 81e7009ea46c95 arch/powerpc/kernel/signal_32.c Stephen Rothwell >> 2005-10-18  311      /* save spe registers */ >> 81e7009ea46c95 arch/powerpc/kernel/signal_32.c Stephen Rothwell >> 2005-10-18  312      if (current->thread.used_spe) { >> ef75e73182949a arch/powerpc/kernel/signal_32.c Christophe Leroy >> 2020-08-18  313          unsafe_copy_to_user(&frame->mc_vregs, >> current->thread.evr, >> ef75e73182949a arch/powerpc/kernel/signal_32.c Christophe Leroy >> 2020-08-18  314                      ELF_NEVRREG * sizeof(u32), failed); >> 81e7009ea46c95 arch/powerpc/kernel/signal_32.c Stephen Rothwell >> 2005-10-18  315          /* set MSR_SPE in the saved MSR value to >> indicate that >> 81e7009ea46c95 arch/powerpc/kernel/signal_32.c Stephen Rothwell >> 2005-10-18  316             frame->mc_vregs contains valid data */ >> 9e7511861c4f8d arch/powerpc/kernel/signal_32.c Michael Neuling >> 2008-06-25  317          msr |= MSR_SPE; >> 81e7009ea46c95 arch/powerpc/kernel/signal_32.c Stephen Rothwell >> 2005-10-18  318      } >> 81e7009ea46c95 arch/powerpc/kernel/signal_32.c Stephen Rothwell >> 2005-10-18  319      /* else assert((regs->msr & MSR_SPE) == 0) */ >> 81e7009ea46c95 arch/powerpc/kernel/signal_32.c Stephen Rothwell >> 2005-10-18  320 >> 81e7009ea46c95 arch/powerpc/kernel/signal_32.c Stephen Rothwell >> 2005-10-18  321      /* We always copy to/from spefscr */ >> ef75e73182949a arch/powerpc/kernel/signal_32.c Christophe Leroy >> 2020-08-18  322      unsafe_put_user(current->thread.spefscr, >> ef75e73182949a arch/powerpc/kernel/signal_32.c Christophe Leroy >> 2020-08-18  323              (u32 __user *)&frame->mc_vregs + >> ELF_NEVRREG, failed); >> 81e7009ea46c95 arch/powerpc/kernel/signal_32.c Stephen Rothwell >> 2005-10-18  324  #endif /* CONFIG_SPE */ >> 81e7009ea46c95 arch/powerpc/kernel/signal_32.c Stephen Rothwell >> 2005-10-18  325 >> ef75e73182949a arch/powerpc/kernel/signal_32.c Christophe Leroy >> 2020-08-18  326      unsafe_put_user(msr, &frame->mc_gregs[PT_MSR], >> failed); >> ef75e73182949a arch/powerpc/kernel/signal_32.c Christophe Leroy >> 2020-08-18  327 >> 1d25f11fdbcc53 arch/powerpc/kernel/signal_32.c Michael Neuling >> 2013-06-09  328      /* We need to write 0 the MSR top 32 bits in the >> tm frame so that we >> 1d25f11fdbcc53 arch/powerpc/kernel/signal_32.c Michael Neuling >> 2013-06-09  329       * can check it on the restore to see if TM is >> active >> 1d25f11fdbcc53 arch/powerpc/kernel/signal_32.c Michael Neuling >> 2013-06-09  330       */ >> ef75e73182949a arch/powerpc/kernel/signal_32.c Christophe Leroy >> 2020-08-18  331      if (tm_frame) >> ef75e73182949a arch/powerpc/kernel/signal_32.c Christophe Leroy >> 2020-08-18  332          unsafe_put_user(0, >> &tm_frame->mc_gregs[PT_MSR], failed); >> 1d25f11fdbcc53 arch/powerpc/kernel/signal_32.c Michael Neuling >> 2013-06-09  333 >> ^1da177e4c3f41 arch/ppc64/kernel/signal32.c    Linus Torvalds >> 2005-04-16  334      return 0; >> ef75e73182949a arch/powerpc/kernel/signal_32.c Christophe Leroy >> 2020-08-18  335 >> ef75e73182949a arch/powerpc/kernel/signal_32.c Christophe Leroy >> 2020-08-18  336  failed: >> ef75e73182949a arch/powerpc/kernel/signal_32.c Christophe Leroy >> 2020-08-18  337      return 1; >> ^1da177e4c3f41 arch/ppc64/kernel/signal32.c    Linus Torvalds >> 2005-04-16  338  } >> ^1da177e4c3f41 arch/ppc64/kernel/signal32.c    Linus Torvalds >> 2005-04-16  339 >> >> :::::: The code at line 297 was first introduced by commit >> :::::: ec67ad82814bee92251fd963bf01c7a173856555 powerpc/signals: >> Improved mark VSX not saved with small contexts fix >> >> :::::: TO: Michael Neuling >> :::::: CC: Benjamin Herrenschmidt >> >> --- >> 0-DAY CI Kernel Test Service, Intel Corporation >> https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org >> > _______________________________________________ > kbuild-all mailing list -- kbuild-all@lists.01.org > To unsubscribe send an email to kbuild-all-leave@lists.01.org