Re: [PATCH v3] x86/boot: Warn on future overlapping memcpy() use

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

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Hi,

[auto build test ERROR on tip/auto-latest]
[cannot apply to tip/x86/core v4.6-rc5 next-20160428]
[if your patch is applied to the wrong git tree, please drop us a note to help improving the system]

url:    https://github.com/0day-ci/linux/commits/Kees-Cook/x86-boot-Warn-on-future-overlapping-memcpy-use/20160429-075026
config: i386-tinyconfig (attached as .config)
reproduce:
        # save the attached .config to linux build tree
        make ARCH=i386 

All error/warnings (new ones prefixed by >>):

   arch/x86/boot/compressed/string.c: In function 'memmove':
>> arch/x86/boot/compressed/string.c:56:10: warning: implicit declaration of function 'memcpy' [-Wimplicit-function-declaration]
      return memcpy(dest, src, n);
             ^
>> arch/x86/boot/compressed/string.c:56:10: warning: return makes pointer from integer without a cast [-Wint-conversion]
   arch/x86/boot/compressed/string.c: At top level:
>> arch/x86/boot/compressed/string.c:65:7: error: conflicting types for 'memcpy'
    void *memcpy(void *dest, const void *src, size_t n)
          ^
   arch/x86/boot/compressed/string.c:56:10: note: previous implicit declaration of 'memcpy' was here
      return memcpy(dest, src, n);
             ^
   arch/x86/boot/compressed/string.c: In function 'memcpy':
>> arch/x86/boot/compressed/string.c:68:3: warning: implicit declaration of function 'warn' [-Wimplicit-function-declaration]
      warn("Avoiding potentially unsafe overlapping memcpy()!");
      ^

vim +/memcpy +65 arch/x86/boot/compressed/string.c

    50	void *memmove(void *dest, const void *src, size_t n)
    51	{
    52		unsigned char *d = dest;
    53		const unsigned char *s = src;
    54	
    55		if (d <= s || d - s >= n)
  > 56			return memcpy(dest, src, n);
    57	
    58		while (n-- > 0)
    59			d[n] = s[n];
    60	
    61		return dest;
    62	}
    63	
    64	/* Detect and warn about potential overlaps, but handle them with memmove. */
  > 65	void *memcpy(void *dest, const void *src, size_t n)
    66	{
    67		if (dest > src && dest - src < n) {
  > 68			warn("Avoiding potentially unsafe overlapping memcpy()!");
    69			return memmove(dest, src, n);
    70		}
    71		return __memcpy(dest, src, n);

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