linux-kernel - arch/parisc/include/asm/cmpxchg.h:75:61: sparse: sparse: cast truncates bits from constant value (e0f510cc becomes cc)

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Message-ID: <202008210829.KVwn7Xeh%lkp@intel.com>
Date:   Fri, 21 Aug 2020 08:57:32 +0800
From:   kernel test robot <lkp@...el.com>
To:     Liam Beguin <liambeguin@...il.com>
Cc:     kbuild-all@...ts.01.org, linux-kernel@...r.kernel.org,
        Helge Deller <deller@....de>
Subject: arch/parisc/include/asm/cmpxchg.h:75:61: sparse: sparse: cast
 truncates bits from constant value (e0f510cc becomes cc)

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   da2968ff879b9e74688cdc658f646971991d2c56
commit: b344d6a83d01c52fddbefa6b3b4764da5b1022a0 parisc: add support for cmpxchg on u8 pointers
date:   4 weeks ago
config: parisc-randconfig-s032-20200820 (attached as .config)
compiler: hppa-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: v0.6.2-191-g10164920-dirty
        git checkout b344d6a83d01c52fddbefa6b3b4764da5b1022a0
        # 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=parisc 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@...el.com>


sparse warnings: (new ones prefixed by >>)

   fs/erofs/utils.c: note: in included file (through arch/parisc/include/asm/atomic.h, include/linux/atomic.h, arch/parisc/include/asm/bitops.h, ...):
>> arch/parisc/include/asm/cmpxchg.h:75:61: sparse: sparse: cast truncates bits from constant value (e0f510cc becomes cc)
--
   fs/erofs/zdata.c: note: in included file (through arch/parisc/include/asm/atomic.h, include/linux/atomic.h, arch/parisc/include/asm/bitops.h, ...):
>> arch/parisc/include/asm/cmpxchg.h:75:61: sparse: sparse: cast truncates bits from constant value (e0f510cc becomes cc)
   arch/parisc/include/asm/cmpxchg.h:75:52: sparse: sparse: cast truncates bits from constant value (5f0ecafe becomes fe)
   arch/parisc/include/asm/cmpxchg.h:75:52: sparse: sparse: cast truncates bits from constant value (5f0ecafe becomes fe)
   arch/parisc/include/asm/cmpxchg.h:75:61: sparse: sparse: cast truncates bits from constant value (5f0edead becomes ad)

# https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b344d6a83d01c52fddbefa6b3b4764da5b1022a0
git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
git fetch --no-tags linus master
git checkout b344d6a83d01c52fddbefa6b3b4764da5b1022a0
vim +75 arch/parisc/include/asm/cmpxchg.h

    64	
    65	/* don't worry...optimizer will get rid of most of this */
    66	static inline unsigned long
    67	__cmpxchg(volatile void *ptr, unsigned long old, unsigned long new_, int size)
    68	{
    69		switch (size) {
    70	#ifdef CONFIG_64BIT
    71		case 8: return __cmpxchg_u64((u64 *)ptr, old, new_);
    72	#endif
    73		case 4: return __cmpxchg_u32((unsigned int *)ptr,
    74					     (unsigned int)old, (unsigned int)new_);
  > 75		case 1: return __cmpxchg_u8((u8 *)ptr, (u8)old, (u8)new_);
    76		}
    77		__cmpxchg_called_with_bad_pointer();
    78		return old;
    79	}
    80	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

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