Re: [PATCH v3] mm/sparsemem: Fix 'mem_section' will never be NULL gcc 12 warning

[kernel test robot <lkp@intel.com>]

Hi Waiman,

I love your patch! Perhaps something to improve:

[auto build test WARNING on hnaz-mm/master]

url:    https://github.com/intel-lab-lkp/linux/commits/Waiman-Long/mm-sparsemem-Fix-mem_section-will-never-be-NULL-gcc-12-warning/20220331-050049
base:   https://github.com/hnaz/linux-mm master
config: arm-randconfig-c024-20220330 (https://download.01.org/0day-ci/archive/20220331/202203312327.XGeCiD5T-lkp@intel.com/config)
compiler: arm-linux-gnueabi-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://github.com/intel-lab-lkp/linux/commit/2098f1d78cde338e81b3ba596ea39f37824e496e
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Waiman-Long/mm-sparsemem-Fix-mem_section-will-never-be-NULL-gcc-12-warning/20220331-050049
        git checkout 2098f1d78cde338e81b3ba596ea39f37824e496e
        # save the config file to linux build tree
        mkdir build_dir
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross O=build_dir ARCH=arm SHELL=/bin/bash security/keys/encrypted-keys/

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 >>):

   In file included from include/linux/gfp.h:6,
                    from include/linux/umh.h:4,
                    from include/linux/kmod.h:9,
                    from include/linux/module.h:17,
                    from security/keys/encrypted-keys/encrypted.c:15:
   security/keys/encrypted-keys/encrypted.c: In function 'derived_key_encrypt.constprop':
>> include/linux/mmzone.h:1432:23: warning: array subscript 32 is outside array bounds of 'struct mem_section[32][1]' [-Warray-bounds]
    1432 |         unsigned long map = section->section_mem_map;
         |                       ^~~
   include/linux/mmzone.h:1390:27: note: while referencing 'mem_section'
    1390 | extern struct mem_section mem_section[NR_SECTION_ROOTS][SECTIONS_PER_ROOT];
         |                           ^~~~~~~~~~~


vim +1432 include/linux/mmzone.h

29751f6991e845 Andy Whitcroft 2005-06-23  1429  
29751f6991e845 Andy Whitcroft 2005-06-23  1430  static inline struct page *__section_mem_map_addr(struct mem_section *section)
29751f6991e845 Andy Whitcroft 2005-06-23  1431  {
29751f6991e845 Andy Whitcroft 2005-06-23 @1432  	unsigned long map = section->section_mem_map;
29751f6991e845 Andy Whitcroft 2005-06-23  1433  	map &= SECTION_MAP_MASK;
29751f6991e845 Andy Whitcroft 2005-06-23  1434  	return (struct page *)map;
29751f6991e845 Andy Whitcroft 2005-06-23  1435  }
29751f6991e845 Andy Whitcroft 2005-06-23  1436  

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