tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   7ddb58cb0ecae8e8b6181d736a87667cc9ab8389
commit: e5af50a5df571c1d0268b02f924de49b742c990f arm64: kasan: mte: move GCR_EL1 switch to task switch when KASAN disabled
date:   5 weeks ago
config: arm64-buildonly-randconfig-r006-20211104 (attached as .config)
compiler: aarch64-linux-gcc (GCC) 11.2.0
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
        # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=e5af50a5df571c1d0268b02f924de49b742c990f
        git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
        git fetch --no-tags linus master
        git checkout e5af50a5df571c1d0268b02f924de49b742c990f
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross ARCH=arm64 

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

All warnings (new ones prefixed by >>):

>> arch/arm64/kernel/mte.c:197:13: warning: no previous prototype for 'kasan_hw_tags_enable' [-Wmissing-prototypes]
     197 | void __init kasan_hw_tags_enable(struct alt_instr *alt, __le32 *origptr,
         |             ^~~~~~~~~~~~~~~~~~~~


vim +/kasan_hw_tags_enable +197 arch/arm64/kernel/mte.c

   196	
 > 197	void __init kasan_hw_tags_enable(struct alt_instr *alt, __le32 *origptr,
   198					 __le32 *updptr, int nr_inst)
   199	{
   200		BUG_ON(nr_inst != 1); /* Branch -> NOP */
   201	
   202		if (kasan_hw_tags_enabled())
   203			*updptr = cpu_to_le32(aarch64_insn_gen_nop());
   204	}
   205	

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