linux-kernel - arch/alpha/include/asm/xchg.h:234:32: sparse: sparse: cast truncates bits from constant value (eb9f becomes 9f)

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Message-ID: <202311161930.Y0q8E1aT-lkp@intel.com>
Date:   Thu, 16 Nov 2023 20:07:40 +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/alpha/include/asm/xchg.h:234:32: sparse: sparse: cast truncates
 bits from constant value (eb9f becomes 9f)

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   c42d9eeef8e5ba9292eda36fd8e3c11f35ee065c
commit: c3c510ce431cd99fa10dcd50d995c8e89330ee5b bpf: Add 'owner' field to bpf_{list,rb}_node
date:   4 months ago
config: alpha-randconfig-r123-20231116 (https://download.01.org/0day-ci/archive/20231116/202311161930.Y0q8E1aT-lkp@intel.com/config)
compiler: alpha-linux-gcc (GCC) 13.2.0
reproduce: (https://download.01.org/0day-ci/archive/20231116/202311161930.Y0q8E1aT-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/202311161930.Y0q8E1aT-lkp@intel.com/

sparse warnings: (new ones prefixed by >>)
   kernel/bpf/helpers.c: note: in included file (through include/linux/mmzone.h, include/linux/gfp.h, include/linux/umh.h, include/linux/kmod.h, ...):
   include/linux/page-flags.h:240:46: sparse: sparse: self-comparison always evaluates to false
   kernel/bpf/helpers.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 (eb9f becomes 9f)
>> arch/alpha/include/asm/xchg.h:234:32: sparse: sparse: cast truncates bits from constant value (eb9f becomes 9f)
   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 +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://github.com/intel/lkp-tests/wiki