Re: [kbuild-all] Re: arch/powerpc/kernel/signal_32.c:297:2: warning: Value stored to 'msr' is never read [clang-analyzer-deadcode.DeadStores]

[Rong Chen]

On 8/24/21 3:29 PM, Christophe Leroy wrote:
> Le 24/08/2021 à 08:59, Chen, Rong A a écrit :
> > 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 <lkp@xxxxxxxxx>
> > > >
> > > >
> > > > 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

Hi Christophe,

It's my fault, I didn't see it correctly, and I have no idea why 
clang-analyzer reported it as a issue,
we'll double check such warning next time.

Best Regards,
Rong Chen