RE: [tip:x86/mm 1/23] arch/x86/mm/init.c:75:6: warning: no previous prototype for function 'x86_has_pat_wp'

[Li, Philip]

> Subject: Re: [tip:x86/mm 1/23] arch/x86/mm/init.c:75:6: warning: no previous
> prototype for function 'x86_has_pat_wp'
> 
> Masahiro and Philip,
> We're seeing a bunch of -Wmissing-prototypes warnings from 0day bot
> suddenly today.  Did something change on the Kbuild or 0day bot side?
Hi Nick, W=1 was added to make. This leads to extra warnings.

> 
> On Tue, May 19, 2020 at 2:25 PM Nathan Chancellor
> <natechancellor@xxxxxxxxx> wrote:
> >
> > On Tue, May 19, 2020 at 10:55:05PM +0200, Borislav Petkov wrote:
> > > On Wed, May 20, 2020 at 01:51:25AM +0800, kbuild test robot wrote:
> > > > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86/mm
> > > > head:   bd1de2a7aace4d1d312fb1be264b8fafdb706208
> > > > commit: 1f6f655e01adebf5bd5e6c3da2e843c104ded051 [1/23] x86/mm: Add
> a x86_has_pat_wp() helper
> > > > config: x86_64-randconfig-r012-20200519 (attached as .config)
> > > > compiler: clang version 11.0.0 (https://github.com/llvm/llvm-project
> 135b877874fae96b4372c8a3fbfaa8ff44ff86e3)
> > > > reproduce:
> > > >         wget https://raw.githubusercontent.com/intel/lkp-
> tests/master/sbin/make.cross -O ~/bin/make.cross
> > > >         chmod +x ~/bin/make.cross
> > > >         # install x86_64 cross compiling tool for clang build
> > > >         # apt-get install binutils-x86-64-linux-gnu
> > > >         git checkout 1f6f655e01adebf5bd5e6c3da2e843c104ded051
> > > >         # save the attached .config to linux build tree
> > > >         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang
> make.cross ARCH=x86_64
> > > >
> > > > If you fix the issue, kindly add following tag as appropriate
> > > > Reported-by: kbuild test robot <lkp@xxxxxxxxx>
> > > >
> > > > All warnings (new ones prefixed by >>, old ones prefixed by <<):
> > > >
> > > > >> arch/x86/mm/init.c:75:6: warning: no previous prototype for function
> 'x86_has_pat_wp' [-Wmissing-prototypes]
> > > > bool x86_has_pat_wp(void)
> > > > ^
> > >
> > > Triggers with gcc too:
> > >
> > > make W=1 arch/x86/mm/init.o
> > >
> > > ...
> > >
> > > arch/x86/mm/init.c:81:6: warning: no previous prototype for âx86_has_pat_wpâ
> [-Wmissing-prototypes]
> > >    81 | bool x86_has_pat_wp(void)
> > >       |      ^~~~~~~~~~~~~~
> > >
> > >
> > > -Wmissing-prototypes is default off, though, dunno why clang 11 has it
> > > on.
> >
> > It doesn't: https://godbolt.org/z/rU5_5H
> >
> > I assume this is caused by some sort of internal change to the 0day
> > infrastructure (testing W=1?)
> >
> > I cannot see this without adding W=1 to make at the listed commit with
> > the provided config.
> >
> > Cheers,
> > Nathan
> >
> > > Anyway, something for Benni to fix. CCed and leaving the rest for him as
> > > reference.
> > >
> > > > arch/x86/mm/init.c:75:1: note: declare 'static' if the function is not intended
> to be used outside of this translation unit
> > > > bool x86_has_pat_wp(void)
> > > > ^
> > > > static
> > > > arch/x86/mm/init.c:866:13: warning: no previous prototype for function
> 'mem_encrypt_free_decrypted_mem' [-Wmissing-prototypes]
> > > > void __weak mem_encrypt_free_decrypted_mem(void) { }
> > > > ^
> > > > arch/x86/mm/init.c:866:1: note: declare 'static' if the function is not intended
> to be used outside of this translation unit
> > > > void __weak mem_encrypt_free_decrypted_mem(void) { }
> > > > ^
> > > > static
> > > > 2 warnings generated.
> > > >
> > > > vim +/x86_has_pat_wp +75 arch/x86/mm/init.c
> > > >
> > > >     73
> > > >     74      /* Check that the write-protect PAT entry is set for write-protect */
> > > >   > 75      bool x86_has_pat_wp(void)
> > > >     76      {
> > > >     77              return __pte2cachemode_tbl[_PAGE_CACHE_MODE_WP] ==
> _PAGE_CACHE_MODE_WP;
> > > >     78      }
> > > >     79
> > > >
> > > > ---
> > > > 0-DAY CI Kernel Test Service, Intel Corporation
> > > > https://lists.01.org/hyperkitty/list/kbuild-all@xxxxxxxxxxxx
> > >
> > >
> > >
> > > --
> > > Regards/Gruss,
> > >     Boris.
> > >
> > > https://people.kernel.org/tglx/notes-about-netiquette
> > >
> >
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> linux/20200519212541.GA3580016%40ubuntu-s3-xlarge-x86.
> 
> 
> 
> --
> Thanks,
> ~Nick Desaulniers