Re: [PATCH RFC v3 1/2] mm: Add personality flag to limit address to 47 bits

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

Hi Charlie,

[This is a private test report for your RFC patch.]
kernel test robot noticed the following build warnings:

[auto build test WARNING on 5be63fc19fcaa4c236b307420483578a56986a37]

url:    https://github.com/intel-lab-lkp/linux/commits/Charlie-Jenkins/mm-Add-personality-flag-to-limit-address-to-47-bits/20240906-052121
base:   5be63fc19fcaa4c236b307420483578a56986a37
patch link:    https://lore.kernel.org/r/20240905-patches-below_hint_mmap-v3-1-3cd5564efbbb%40rivosinc.com
patch subject: [PATCH RFC v3 1/2] mm: Add personality flag to limit address to 47 bits
config: i386-defconfig (https://download.01.org/0day-ci/archive/20240909/202409090150.Po6fKG3u-lkp@intel.com/config)
compiler: clang version 18.1.5 (https://github.com/llvm/llvm-project 617a15a9eac96088ae5e9134248d8236e34b91b1)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240909/202409090150.Po6fKG3u-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202409090150.Po6fKG3u-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> mm/mmap.c:1770:44: warning: shift count >= width of type [-Wshift-count-overflow]
    1770 |                 info->high_limit = MIN(info->high_limit, BIT(47) - 1);
         |                                    ~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~
   include/vdso/bits.h:7:26: note: expanded from macro 'BIT'
       7 | #define BIT(nr)                 (UL(1) << (nr))
         |                                        ^
   include/linux/minmax.h:329:30: note: expanded from macro 'MIN'
     329 | #define MIN(a,b) __cmp(min,a,b)
         |                  ~~~~~~~~~~~~^~
   include/linux/minmax.h:90:45: note: expanded from macro '__cmp'
      90 | #define __cmp(op, x, y) ((x) __cmp_op_##op (y) ? (x) : (y))
         |                                             ^
>> mm/mmap.c:1770:44: warning: shift count >= width of type [-Wshift-count-overflow]
    1770 |                 info->high_limit = MIN(info->high_limit, BIT(47) - 1);
         |                                    ~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~
   include/vdso/bits.h:7:26: note: expanded from macro 'BIT'
       7 | #define BIT(nr)                 (UL(1) << (nr))
         |                                        ^
   include/linux/minmax.h:329:30: note: expanded from macro 'MIN'
     329 | #define MIN(a,b) __cmp(min,a,b)
         |                  ~~~~~~~~~~~~^~
   include/linux/minmax.h:90:57: note: expanded from macro '__cmp'
      90 | #define __cmp(op, x, y) ((x) __cmp_op_##op (y) ? (x) : (y))
         |                                                         ^
   2 warnings generated.


vim +1770 mm/mmap.c

  1755	
  1756	/*
  1757	 * Search for an unmapped address range.
  1758	 *
  1759	 * We are looking for a range that:
  1760	 * - does not intersect with any VMA;
  1761	 * - is contained within the [low_limit, high_limit) interval;
  1762	 * - is at least the desired size.
  1763	 * - satisfies (begin_addr & align_mask) == (align_offset & align_mask)
  1764	 */
  1765	unsigned long vm_unmapped_area(struct vm_unmapped_area_info *info)
  1766	{
  1767		unsigned long addr;
  1768	
  1769		if (current->personality & ADDR_LIMIT_47BIT)
> 1770			info->high_limit = MIN(info->high_limit, BIT(47) - 1);
  1771	
  1772		if (info->flags & VM_UNMAPPED_AREA_TOPDOWN)
  1773			addr = unmapped_area_topdown(info);
  1774		else
  1775			addr = unmapped_area(info);
  1776	
  1777		trace_vm_unmapped_area(addr, info);
  1778		return addr;
  1779	}
  1780	

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