linux-kernel - arch/sparc/include/asm/cmpxchg_64.h:161:55: sparse: sparse: cast truncates bits from constant value (ffffffffe0f510cc becomes cc)

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Date:   Sun, 16 Apr 2023 10:48:36 +0800
From:   kernel test robot <lkp@...el.com>
To:     Gao Xiang <hsiangkao@...ux.alibaba.com>
Cc:     oe-kbuild-all@...ts.linux.dev, linux-kernel@...r.kernel.org,
        Yue Hu <huyue2@...lpad.com>, Chao Yu <yuchao0@...wei.com>,
        Chao Yu <chao@...nel.org>
Subject: arch/sparc/include/asm/cmpxchg_64.h:161:55: sparse: sparse: cast
 truncates bits from constant value (ffffffffe0f510cc becomes cc)

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   a7a55e27ad72fb0dc9281d6211cffeebef8dde65
commit: 2f44013e39984c127c6efedf70e6b5f4e9dcf315 erofs: fix pcluster use-after-free on UP platforms
date:   7 months ago
config: sparc64-randconfig-s051-20230416 (https://download.01.org/0day-ci/archive/20230416/202304161045.XaIBg23J-lkp@intel.com/config)
compiler: sparc64-linux-gcc (GCC) 12.1.0
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: v0.6.4-39-gce1a6720-dirty
        # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=2f44013e39984c127c6efedf70e6b5f4e9dcf315
        git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
        git fetch --no-tags linus master
        git checkout 2f44013e39984c127c6efedf70e6b5f4e9dcf315
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' O=build_dir ARCH=sparc64 olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' O=build_dir ARCH=sparc64 SHELL=/bin/bash fs/erofs/

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@...el.com>
| Link: https://lore.kernel.org/oe-kbuild-all/202304161045.XaIBg23J-lkp@intel.com/

sparse warnings: (new ones prefixed by >>)
   fs/erofs/utils.c: note: in included file (through arch/sparc/include/asm/cmpxchg.h, arch/sparc/include/asm/atomic_64.h, arch/sparc/include/asm/atomic.h, ...):
>> arch/sparc/include/asm/cmpxchg_64.h:161:55: sparse: sparse: cast truncates bits from constant value (ffffffffe0f510cc becomes cc)
--
   fs/erofs/zdata.c: note: in included file (through arch/sparc/include/asm/cmpxchg.h, arch/sparc/include/asm/atomic_64.h, arch/sparc/include/asm/atomic.h, ...):
>> arch/sparc/include/asm/cmpxchg_64.h:161:55: sparse: sparse: cast truncates bits from constant value (ffffffffe0f510cc becomes cc)
   arch/sparc/include/asm/cmpxchg_64.h:161:50: sparse: sparse: cast truncates bits from constant value (5f0ecafe becomes fe)
   arch/sparc/include/asm/cmpxchg_64.h:161:50: sparse: sparse: cast truncates bits from constant value (5f0ecafe becomes fe)
   arch/sparc/include/asm/cmpxchg_64.h:161:55: sparse: sparse: cast truncates bits from constant value (5f0edead becomes ad)

vim +161 arch/sparc/include/asm/cmpxchg_64.h

d550bbd40c0e10 David Howells 2012-03-28  155  
d550bbd40c0e10 David Howells 2012-03-28  156  static inline unsigned long
d550bbd40c0e10 David Howells 2012-03-28  157  __cmpxchg(volatile void *ptr, unsigned long old, unsigned long new, int size)
d550bbd40c0e10 David Howells 2012-03-28  158  {
d550bbd40c0e10 David Howells 2012-03-28  159  	switch (size) {
a12ee2349312d7 Babu Moger    2017-05-24  160  		case 1:
a12ee2349312d7 Babu Moger    2017-05-24 @161  			return __cmpxchg_u8(ptr, old, new);
d550bbd40c0e10 David Howells 2012-03-28  162  		case 4:
d550bbd40c0e10 David Howells 2012-03-28  163  			return __cmpxchg_u32(ptr, old, new);
d550bbd40c0e10 David Howells 2012-03-28  164  		case 8:
d550bbd40c0e10 David Howells 2012-03-28  165  			return __cmpxchg_u64(ptr, old, new);
d550bbd40c0e10 David Howells 2012-03-28  166  	}
d550bbd40c0e10 David Howells 2012-03-28  167  	__cmpxchg_called_with_bad_pointer();
d550bbd40c0e10 David Howells 2012-03-28  168  	return old;
d550bbd40c0e10 David Howells 2012-03-28  169  }
d550bbd40c0e10 David Howells 2012-03-28  170  

:::::: The code at line 161 was first introduced by commit
:::::: a12ee2349312d7112b9b7c6ac2e70c5ec2ca334e arch/sparc: Introduce cmpxchg_u8 SPARC

:::::: TO: Babu Moger <babu.moger@...cle.com>
:::::: CC: David S. Miller <davem@...emloft.net>

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests