[joro:sev-es-kexec 1/12] kernel/kexec.c:198:13: warning: no previous prototype for function 'arch_kexec_supported'

[kernel test robot]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/joro/linux.git sev-es-kexec
head:   3467dc3cdbe65c619cd9b5c8db47da63b0655300
commit: 4eeabbfae0a6163e935a6462acc02fe4f17d3680 [1/12] kexec: Allow architecture code to opt-out at runtime
config: powerpc-randconfig-r005-20210702 (attached as .config)
compiler: clang version 13.0.0 (https://github.com/llvm/llvm-project 9eb613b2de3163686b1a4bd1160f15ac56a4b083)
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/joro/linux.git/commit/?id=4eeabbfae0a6163e935a6462acc02fe4f17d3680
        git remote add joro https://git.kernel.org/pub/scm/linux/kernel/git/joro/linux.git
        git fetch --no-tags joro sev-es-kexec
        git checkout 4eeabbfae0a6163e935a6462acc02fe4f17d3680
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=powerpc 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@xxxxxxxxx>

All warnings (new ones prefixed by >>):

   In file included from kernel/kexec.c:10:
   In file included from include/linux/mm.h:9:
   In file included from include/linux/mmdebug.h:5:
   In file included from include/linux/bug.h:5:
   In file included from arch/powerpc/include/asm/bug.h:109:
   In file included from include/asm-generic/bug.h:20:
   In file included from include/linux/kernel.h:12:
   In file included from include/linux/bitops.h:32:
   In file included from arch/powerpc/include/asm/bitops.h:62:
   arch/powerpc/include/asm/barrier.h:49:9: warning: '__lwsync' macro redefined [-Wmacro-redefined]
   #define __lwsync()      __asm__ __volatile__ (stringify_in_c(LWSYNC) : : :"memory")
           ^
   <built-in>:308:9: note: previous definition is here
   #define __lwsync __builtin_ppc_lwsync
           ^
>> kernel/kexec.c:198:13: warning: no previous prototype for function 'arch_kexec_supported' [-Wmissing-prototypes]
   bool __weak arch_kexec_supported(void)
               ^
   kernel/kexec.c:198:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
   bool __weak arch_kexec_supported(void)
   ^
   static 
   2 warnings generated.


vim +/arch_kexec_supported +198 kernel/kexec.c

   176	
   177	/*
   178	 * Exec Kernel system call: for obvious reasons only root may call it.
   179	 *
   180	 * This call breaks up into three pieces.
   181	 * - A generic part which loads the new kernel from the current
   182	 *   address space, and very carefully places the data in the
   183	 *   allocated pages.
   184	 *
   185	 * - A generic part that interacts with the kernel and tells all of
   186	 *   the devices to shut down.  Preventing on-going dmas, and placing
   187	 *   the devices in a consistent state so a later kernel can
   188	 *   reinitialize them.
   189	 *
   190	 * - A machine specific part that includes the syscall number
   191	 *   and then copies the image to it's final destination.  And
   192	 *   jumps into the image at entry.
   193	 *
   194	 * kexec does not sync, or unmount filesystems so if you need
   195	 * that to happen you need to do that yourself.
   196	 */
   197	
 > 198	bool __weak arch_kexec_supported(void)
   199	{
   200		return true;
   201	}
   202	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@xxxxxxxxxxxx

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