Re: [kbuild-all] Re: [gpio:ib-for-each-clump 4/4] include/linux/bitmap.h:639:45: sparse: sparse: shift too big (64) for type unsigned long

Rong Chen <rong.a.chen@xxxxxxxxx> · Fri, 17 Jul 2020 15:14:46 +0800

On 7/17/20 5:25 AM, Andy Shevchenko wrote:
On Thu, Jul 16, 2020 at 11:13 PM kernel test robot <lkp@xxxxxxxxx> 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@xxxxxxxxx>

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