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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:     "Chen, Rong A" <rong.a.chen@intel.com>,
        kernel test robot <lkp@intel.com>
Cc:     clang-built-linux@googlegroups.com, kbuild-all@lists.01.org,
        linux-kernel@vger.kernel.org, Michael Ellerman <mpe@ellerman.id.au>
References: <202108231827.N9VUIKbD-lkp@intel.com>
 <3db8de6e-a971-be9f-19eb-e7d95faf2870@csgroup.eu>
 <7955eec5-c1d7-e0d7-280a-138d96b2daa9@intel.com>
From:   Christophe Leroy <christophe.leroy@csgroup.eu>
Message-ID: <79754a11-fa14-756a-fc30-5cb139a286b6@csgroup.eu>
Date:   Tue, 24 Aug 2021 09:29:26 +0200
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Le 24/08/2021 ? 08:59, Chen, Rong A a ?crit?:
> 
> 
> On 8/23/2021 10:35 PM, Christophe Leroy wrote:
>>
>>
>> Le 23/08/2021 ? 12:59, kernel test robot a ?crit?:
>>> 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 <lkp@intel.com>
>>>
>>>
>>> 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.


No no, the 'unsafe_put_user(msr, &frame->mc_gregs[PT_MSR], failed) ' at line 326 is not under 
CONFIG_VSX as far as I can see.


Christophe