linux-kernel - arch/arm64/include/asm/cmpxchg.h:171:1: sparse: sparse: cast truncates bits from constant value (dead00000000eb9f becomes 9f)

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Date:   Sat, 4 Nov 2023 21:00:13 +0800
From:   kernel test robot <lkp@...el.com>
To:     Dave Marchevsky <davemarchevsky@...com>
Cc:     oe-kbuild-all@...ts.linux.dev, linux-kernel@...r.kernel.org,
        Alexei Starovoitov <ast@...nel.org>
Subject: arch/arm64/include/asm/cmpxchg.h:171:1: sparse: sparse: cast
 truncates bits from constant value (dead00000000eb9f becomes 9f)

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   90b0c2b2edd1adff742c621e246562fbefa11b70
commit: c3c510ce431cd99fa10dcd50d995c8e89330ee5b bpf: Add 'owner' field to bpf_{list,rb}_node
date:   4 months ago
config: arm64-randconfig-r122-20231102 (https://download.01.org/0day-ci/archive/20231104/202311042016.s4qMWPT6-lkp@intel.com/config)
compiler: aarch64-linux-gcc (GCC) 13.2.0
reproduce: (https://download.01.org/0day-ci/archive/20231104/202311042016.s4qMWPT6-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@...el.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202311042016.s4qMWPT6-lkp@intel.com/

sparse warnings: (new ones prefixed by >>)
   kernel/bpf/helpers.c: note: in included file (through arch/arm64/include/asm/atomic.h, include/linux/atomic.h, include/asm-generic/bitops/atomic.h, ...):
>> arch/arm64/include/asm/cmpxchg.h:171:1: sparse: sparse: cast truncates bits from constant value (dead00000000eb9f becomes 9f)
>> arch/arm64/include/asm/cmpxchg.h:171:1: sparse: sparse: cast truncates bits from constant value (dead00000000eb9f becomes eb9f)
>> arch/arm64/include/asm/cmpxchg.h:171:1: sparse: sparse: cast truncates bits from constant value (dead00000000eb9f becomes eb9f)
>> arch/arm64/include/asm/cmpxchg.h:171:1: sparse: sparse: cast truncates bits from constant value (dead00000000eb9f becomes 9f)
>> arch/arm64/include/asm/cmpxchg.h:171:1: sparse: sparse: cast truncates bits from constant value (dead00000000eb9f becomes eb9f)
>> arch/arm64/include/asm/cmpxchg.h:171:1: sparse: sparse: cast truncates bits from constant value (dead00000000eb9f becomes eb9f)
   kernel/bpf/helpers.c:2419:18: sparse: sparse: context imbalance in 'bpf_rcu_read_lock' - wrong count at exit
   kernel/bpf/helpers.c:2424:18: sparse: sparse: context imbalance in 'bpf_rcu_read_unlock' - unexpected unlock

vim +171 arch/arm64/include/asm/cmpxchg.h

10b663aef1c247 Catalin Marinas 2012-03-05  167  
305d454aaa292b Will Deacon     2015-10-08  168  __CMPXCHG_GEN()
305d454aaa292b Will Deacon     2015-10-08  169  __CMPXCHG_GEN(_acq)
305d454aaa292b Will Deacon     2015-10-08  170  __CMPXCHG_GEN(_rel)
305d454aaa292b Will Deacon     2015-10-08 @171  __CMPXCHG_GEN(_mb)
10b663aef1c247 Catalin Marinas 2012-03-05  172  

:::::: The code at line 171 was first introduced by commit
:::::: 305d454aaa292be3a09a9d674e6c35f5b4249a13 arm64: atomics: implement native {relaxed, acquire, release} atomics

:::::: TO: Will Deacon <will.deacon@....com>
:::::: CC: Catalin Marinas <catalin.marinas@....com>

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