On 7/17/20 5:25 AM, Andy Shevchenko wrote:
> On Thu, Jul 16, 2020 at 11:13 PM kernel test robot <lkp@intel.com> wrote:
>> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-gpio.git ib-for-each-clump
>> head:   3358c938236d6a1be51124fbbb2698e50689d382
>> commit: 3358c938236d6a1be51124fbbb2698e50689d382 [4/4] gpio: xilinx: Utilize generic bitmap_get_value and _set_value.
>> config: alpha-randconfig-s031-20200716 (attached as .config)
>> compiler: alpha-linux-gcc (GCC) 9.3.0
>> reproduce:
>>          wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>>          chmod +x ~/bin/make.cross
>>          # apt-get install sparse
>>          # sparse version: v0.6.2-49-g707c5017-dirty
>>          git checkout 3358c938236d6a1be51124fbbb2698e50689d382
>>          # save the attached .config to linux build tree
>>          COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' ARCH=alpha
>>
>> If you fix the issue, kindly add following tag as appropriate
>> Reported-by: kernel test robot <lkp@intel.com>
>>
>>
>> sparse warnings: (new ones prefixed by >>)
>>
>>>> include/linux/bitmap.h:639:45: sparse: sparse: shift too big (64) for type unsigned long
>>>> include/linux/bitmap.h:639:45: sparse: sparse: shift too big (64) for type unsigned long
>>     include/linux/bitmap.h:594:63: sparse: sparse: shift too big (64) for type unsigned long
>>>> include/linux/bitmap.h:639:45: sparse: sparse: shift too big (64) for type unsigned long
>>>> include/linux/bitmap.h:638:17: sparse: sparse: invalid access past the end of 'old' (8 8)
>> vim +639 include/linux/bitmap.h
>>
>> 169c474fb22d8a5 William Breathitt Gray 2019-12-04  613
>> e77c9b6f35c4bdf Syed Nayyar Waris      2020-06-27  614  /**
>> e77c9b6f35c4bdf Syed Nayyar Waris      2020-06-27  615   * bitmap_set_value - set n-bit value within a memory region
>> e77c9b6f35c4bdf Syed Nayyar Waris      2020-06-27  616   * @map: address to the bitmap memory region
>> e77c9b6f35c4bdf Syed Nayyar Waris      2020-06-27  617   * @value: value of nbits
>> e77c9b6f35c4bdf Syed Nayyar Waris      2020-06-27  618   * @start: bit offset of the n-bit value
>> e77c9b6f35c4bdf Syed Nayyar Waris      2020-06-27  619   * @nbits: size of value in bits
>> e77c9b6f35c4bdf Syed Nayyar Waris      2020-06-27  620   */
>> e77c9b6f35c4bdf Syed Nayyar Waris      2020-06-27  621  static inline void bitmap_set_value(unsigned long *map,
>> e77c9b6f35c4bdf Syed Nayyar Waris      2020-06-27  622                                      unsigned long value,
>> e77c9b6f35c4bdf Syed Nayyar Waris      2020-06-27  623                                      unsigned long start, unsigned long nbits)
>> e77c9b6f35c4bdf Syed Nayyar Waris      2020-06-27  624  {
>> e77c9b6f35c4bdf Syed Nayyar Waris      2020-06-27  625          const size_t index = BIT_WORD(start);
>> e77c9b6f35c4bdf Syed Nayyar Waris      2020-06-27  626          const unsigned long offset = start % BITS_PER_LONG;
>> e77c9b6f35c4bdf Syed Nayyar Waris      2020-06-27  627          const unsigned long ceiling = roundup(start + 1, BITS_PER_LONG);
>> e77c9b6f35c4bdf Syed Nayyar Waris      2020-06-27  628          const unsigned long space = ceiling - start;
> If start == 0:
>    index = 0, offset = 0, ceiling = 64, space = 64
>
>> e77c9b6f35c4bdf Syed Nayyar Waris      2020-06-27  629
>> e77c9b6f35c4bdf Syed Nayyar Waris      2020-06-27  630          value &= GENMASK(nbits - 1, 0);
>> e77c9b6f35c4bdf Syed Nayyar Waris      2020-06-27  631
>> e77c9b6f35c4bdf Syed Nayyar Waris      2020-06-27  632          if (space >= nbits) {
>> e77c9b6f35c4bdf Syed Nayyar Waris      2020-06-27  633                  map[index] &= ~(GENMASK(nbits + offset - 1, offset));
>> e77c9b6f35c4bdf Syed Nayyar Waris      2020-06-27  634                  map[index] |= value << offset;
> if nbits > space...
>
>> e77c9b6f35c4bdf Syed Nayyar Waris      2020-06-27  635          } else {
>> e77c9b6f35c4bdf Syed Nayyar Waris      2020-06-27  636                  map[index] &= ~BITMAP_FIRST_WORD_MASK(start);
>> e77c9b6f35c4bdf Syed Nayyar Waris      2020-06-27  637                  map[index] |= value << offset;
>> e77c9b6f35c4bdf Syed Nayyar Waris      2020-06-27 @638                  map[index + 1] &= ~BITMAP_LAST_WORD_MASK(start + nbits);
>> e77c9b6f35c4bdf Syed Nayyar Waris      2020-06-27 @639                  map[index + 1] |= (value >> space);
> space = 64...
>
>> e77c9b6f35c4bdf Syed Nayyar Waris      2020-06-27  640          }
>> e77c9b6f35c4bdf Syed Nayyar Waris      2020-06-27  641  }
> I don't see the test case for this. Can you provide one?
>
>

Hi Andy,

Sparse doesn't check the if condition, it found the issues related to 
the below two lines
when bitmap_set_value was first time used in this commit.

e77c9b6f35c4bdf Syed Nayyar Waris      2020-06-27 @638                  map[index + 1] &= ~BITMAP_LAST_WORD_MASK(start + nbits);
e77c9b6f35c4bdf Syed Nayyar Waris      2020-06-27 @639                  map[index + 1] |= (value >> space);

Best Regards,
Rong Chen