Re: [PATCH bpf-next 1/5] net: checksum: move from32to16() to generic header

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

Hi Puranjay,

kernel test robot noticed the following build warnings:

[auto build test WARNING on bpf-next/master]

url:    https://github.com/intel-lab-lkp/linux/commits/Puranjay-Mohan/net-checksum-move-from32to16-to-generic-header/20241021-202707
base:   https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git master
patch link:    https://lore.kernel.org/r/20241021122112.101513-2-puranjay%40kernel.org
patch subject: [PATCH bpf-next 1/5] net: checksum: move from32to16() to generic header
config: x86_64-randconfig-122-20241022 (https://download.01.org/0day-ci/archive/20241022/202410222149.3FVJFYYy-lkp@intel.com/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20241022/202410222149.3FVJFYYy-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/202410222149.3FVJFYYy-lkp@intel.com/

sparse warnings: (new ones prefixed by >>)
>> lib/checksum.c:84:34: sparse: sparse: incorrect type in argument 1 (different base types) @@     expected restricted __wsum [usertype] sum @@     got unsigned int [assigned] result @@
   lib/checksum.c:84:34: sparse:     expected restricted __wsum [usertype] sum
   lib/checksum.c:84:34: sparse:     got unsigned int [assigned] result
>> lib/checksum.c:84:16: sparse: sparse: incorrect type in assignment (different base types) @@     expected unsigned int [assigned] result @@     got restricted __sum16 @@
   lib/checksum.c:84:16: sparse:     expected unsigned int [assigned] result
   lib/checksum.c:84:16: sparse:     got restricted __sum16

vim +84 lib/checksum.c

    35	
    36	#ifndef do_csum
    37	static unsigned int do_csum(const unsigned char *buff, int len)
    38	{
    39		int odd;
    40		unsigned int result = 0;
    41	
    42		if (len <= 0)
    43			goto out;
    44		odd = 1 & (unsigned long) buff;
    45		if (odd) {
    46	#ifdef __LITTLE_ENDIAN
    47			result += (*buff << 8);
    48	#else
    49			result = *buff;
    50	#endif
    51			len--;
    52			buff++;
    53		}
    54		if (len >= 2) {
    55			if (2 & (unsigned long) buff) {
    56				result += *(unsigned short *) buff;
    57				len -= 2;
    58				buff += 2;
    59			}
    60			if (len >= 4) {
    61				const unsigned char *end = buff + ((unsigned)len & ~3);
    62				unsigned int carry = 0;
    63				do {
    64					unsigned int w = *(unsigned int *) buff;
    65					buff += 4;
    66					result += carry;
    67					result += w;
    68					carry = (w > result);
    69				} while (buff < end);
    70				result += carry;
    71				result = (result & 0xffff) + (result >> 16);
    72			}
    73			if (len & 2) {
    74				result += *(unsigned short *) buff;
    75				buff += 2;
    76			}
    77		}
    78		if (len & 1)
    79	#ifdef __LITTLE_ENDIAN
    80			result += *buff;
    81	#else
    82			result += (*buff << 8);
    83	#endif
  > 84		result = csum_from32to16(result);
    85		if (odd)
    86			result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
    87	out:
    88		return result;
    89	}
    90	#endif
    91	

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