linux-kernel - arch/alpha/include/asm/xchg.h:234:32: sparse: sparse: cast truncates bits from constant value (ffffffffe0f510cc becomes cc)

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Date:   Wed, 19 Oct 2022 03:48:33 +0800
From:   kernel test robot <lkp@...el.com>
To:     Gao Xiang <hsiangkao@...ux.alibaba.com>
Cc:     kbuild-all@...ts.01.org, linux-kernel@...r.kernel.org,
        Yue Hu <huyue2@...lpad.com>, Chao Yu <yuchao0@...wei.com>,
        Chao Yu <chao@...nel.org>
Subject: arch/alpha/include/asm/xchg.h:234:32: 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:   aae703b02f92bde9264366c545e87cec451de471
commit: 2f44013e39984c127c6efedf70e6b5f4e9dcf315 erofs: fix pcluster use-after-free on UP platforms
date:   6 weeks ago
config: alpha-randconfig-s031-20221018
compiler: alpha-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=alpha SHELL=/bin/bash fs/erofs/

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

sparse warnings: (new ones prefixed by >>)
   fs/erofs/utils.c: note: in included file (through arch/alpha/include/asm/cmpxchg.h, arch/alpha/include/asm/atomic.h, include/linux/atomic.h, ...):
>> arch/alpha/include/asm/xchg.h:234:32: sparse: sparse: cast truncates bits from constant value (ffffffffe0f510cc becomes cc)
>> arch/alpha/include/asm/xchg.h:236:32: sparse: sparse: cast truncates bits from constant value (ffffffffe0f510cc becomes 10cc)
--
   fs/erofs/zdata.c: note: in included file (through arch/alpha/include/asm/cmpxchg.h, arch/alpha/include/asm/atomic.h, include/linux/atomic.h, ...):
>> arch/alpha/include/asm/xchg.h:234:32: sparse: sparse: cast truncates bits from constant value (ffffffffe0f510cc becomes cc)
>> arch/alpha/include/asm/xchg.h:236:32: sparse: sparse: cast truncates bits from constant value (ffffffffe0f510cc becomes 10cc)
   arch/alpha/include/asm/xchg.h:234:32: sparse: sparse: cast truncates bits from constant value (5f0ecafe becomes fe)
   arch/alpha/include/asm/xchg.h:236:32: sparse: sparse: cast truncates bits from constant value (5f0ecafe becomes cafe)
   arch/alpha/include/asm/xchg.h:234:32: sparse: sparse: cast truncates bits from constant value (5f0ecafe becomes fe)
   arch/alpha/include/asm/xchg.h:234:32: sparse: sparse: cast truncates bits from constant value (5f0edead becomes ad)
   arch/alpha/include/asm/xchg.h:236:32: sparse: sparse: cast truncates bits from constant value (5f0ecafe becomes cafe)
   arch/alpha/include/asm/xchg.h:236:32: sparse: sparse: cast truncates bits from constant value (5f0edead becomes dead)

vim +234 arch/alpha/include/asm/xchg.h

a6209d6d71f2ab Ivan Kokshaysky 2009-03-31  227  
a6209d6d71f2ab Ivan Kokshaysky 2009-03-31  228  static __always_inline unsigned long
a6209d6d71f2ab Ivan Kokshaysky 2009-03-31  229  ____cmpxchg(, volatile void *ptr, unsigned long old, unsigned long new,
a6209d6d71f2ab Ivan Kokshaysky 2009-03-31  230  	      int size)
a6209d6d71f2ab Ivan Kokshaysky 2009-03-31  231  {
a6209d6d71f2ab Ivan Kokshaysky 2009-03-31  232  	switch (size) {
a6209d6d71f2ab Ivan Kokshaysky 2009-03-31  233  		case 1:
a6209d6d71f2ab Ivan Kokshaysky 2009-03-31 @234  			return ____cmpxchg(_u8, ptr, old, new);
a6209d6d71f2ab Ivan Kokshaysky 2009-03-31  235  		case 2:
a6209d6d71f2ab Ivan Kokshaysky 2009-03-31 @236  			return ____cmpxchg(_u16, ptr, old, new);
a6209d6d71f2ab Ivan Kokshaysky 2009-03-31  237  		case 4:
a6209d6d71f2ab Ivan Kokshaysky 2009-03-31  238  			return ____cmpxchg(_u32, ptr, old, new);
a6209d6d71f2ab Ivan Kokshaysky 2009-03-31  239  		case 8:
a6209d6d71f2ab Ivan Kokshaysky 2009-03-31  240  			return ____cmpxchg(_u64, ptr, old, new);
a6209d6d71f2ab Ivan Kokshaysky 2009-03-31  241  	}
a6209d6d71f2ab Ivan Kokshaysky 2009-03-31  242  	__cmpxchg_called_with_bad_pointer();
a6209d6d71f2ab Ivan Kokshaysky 2009-03-31  243  	return old;
a6209d6d71f2ab Ivan Kokshaysky 2009-03-31  244  }
a6209d6d71f2ab Ivan Kokshaysky 2009-03-31  245  

:::::: The code at line 234 was first introduced by commit
:::::: a6209d6d71f2ab8c63cc1587ef65490d83022baf alpha: xchg/cmpxchg cleanup and fixes

:::::: TO: Ivan Kokshaysky <ink@...assic.park.msu.ru>
:::::: CC: Linus Torvalds <torvalds@...ux-foundation.org>

-- 
0-DAY CI Kernel Test Service
https://01.org/lkp

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