[jgunthorpe:iommufd 7/13] include/linux/overflow.h:66:22: warning: comparison of distinct pointer types lacks a cast

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

tree:   https://github.com/jgunthorpe/linux iommufd
head:   fc388f906088fe5f5f2db6a36931e00124f52042
commit: 1af524ce30ddf820ec974c8635d3299caefc72ed [7/13] iommufd: Data structure to provide IOVA to PFN mapping
config: arc-allyesconfig (https://download.01.org/0day-ci/archive/20220413/202204132034.dp2f42wp-lkp@intel.com/config)
compiler: arceb-elf-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/jgunthorpe/linux/commit/1af524ce30ddf820ec974c8635d3299caefc72ed
        git remote add jgunthorpe https://github.com/jgunthorpe/linux
        git fetch --no-tags jgunthorpe iommufd
        git checkout 1af524ce30ddf820ec974c8635d3299caefc72ed
        # 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=arc SHELL=/bin/bash drivers/iommu/iommufd/

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 arch/arc/include/asm/bug.h:30,
                    from include/linux/bug.h:5,
                    from include/linux/cpumask.h:14,
                    from include/linux/smp.h:13,
                    from include/linux/lockdep.h:14,
                    from drivers/iommu/iommufd/io_pagetable.c:11:
   drivers/iommu/iommufd/io_pagetable.c: In function 'iopt_unaccess_pages':
>> include/linux/overflow.h:66:22: warning: comparison of distinct pointer types lacks a cast
      66 |         (void) (&__a == &__b);                  \
         |                      ^~
   include/asm-generic/bug.h:121:32: note: in definition of macro 'WARN_ON'
     121 |         int __ret_warn_on = !!(condition);                              \
         |                                ^~~~~~~~~
   drivers/iommu/iommufd/io_pagetable.c:486:21: note: in expansion of macro 'check_add_overflow'
     486 |             WARN_ON(check_add_overflow(iova, length - 1, &last_iova)))
         |                     ^~~~~~~~~~~~~~~~~~


vim +66 include/linux/overflow.h

9b80e4c4ddaca35 Kees Cook        2020-08-12  53  
f0907827a8a9152 Rasmus Villemoes 2018-05-08  54  /*
f0907827a8a9152 Rasmus Villemoes 2018-05-08  55   * For simplicity and code hygiene, the fallback code below insists on
f0907827a8a9152 Rasmus Villemoes 2018-05-08  56   * a, b and *d having the same type (similar to the min() and max()
f0907827a8a9152 Rasmus Villemoes 2018-05-08  57   * macros), whereas gcc's type-generic overflow checkers accept
f0907827a8a9152 Rasmus Villemoes 2018-05-08  58   * different types. Hence we don't just make check_add_overflow an
f0907827a8a9152 Rasmus Villemoes 2018-05-08  59   * alias for __builtin_add_overflow, but add type checks similar to
f0907827a8a9152 Rasmus Villemoes 2018-05-08  60   * below.
f0907827a8a9152 Rasmus Villemoes 2018-05-08  61   */
9b80e4c4ddaca35 Kees Cook        2020-08-12  62  #define check_add_overflow(a, b, d) __must_check_overflow(({	\
f0907827a8a9152 Rasmus Villemoes 2018-05-08  63  	typeof(a) __a = (a);			\
f0907827a8a9152 Rasmus Villemoes 2018-05-08  64  	typeof(b) __b = (b);			\
f0907827a8a9152 Rasmus Villemoes 2018-05-08  65  	typeof(d) __d = (d);			\
f0907827a8a9152 Rasmus Villemoes 2018-05-08 @66  	(void) (&__a == &__b);			\
f0907827a8a9152 Rasmus Villemoes 2018-05-08  67  	(void) (&__a == __d);			\
f0907827a8a9152 Rasmus Villemoes 2018-05-08  68  	__builtin_add_overflow(__a, __b, __d);	\
9b80e4c4ddaca35 Kees Cook        2020-08-12  69  }))
f0907827a8a9152 Rasmus Villemoes 2018-05-08  70  

:::::: The code at line 66 was first introduced by commit
:::::: f0907827a8a9152aedac2833ed1b674a7b2a44f2 compiler.h: enable builtin overflow checkers and add fallback code

:::::: TO: Rasmus Villemoes <linux@rasmusvillemoes.dk>
:::::: CC: Kees Cook <keescook@chromium.org>

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