linux-kernel - arch/powerpc/include/asm/cmpxchg.h:626:47: sparse: sparse: cast truncates bits from constant value (5deadbeef000eb9f becomes f000eb9f)

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Message-ID: <202311072357.a2ejf6Jb-lkp@intel.com>
Date:   Wed, 8 Nov 2023 00:19:26 +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/powerpc/include/asm/cmpxchg.h:626:47: sparse: sparse: cast
 truncates bits from constant value (5deadbeef000eb9f becomes f000eb9f)

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   be3ca57cfb777ad820c6659d52e60bbdd36bf5ff
commit: c3c510ce431cd99fa10dcd50d995c8e89330ee5b bpf: Add 'owner' field to bpf_{list,rb}_node
date:   4 months ago
config: powerpc64-randconfig-r113-20231107 (https://download.01.org/0day-ci/archive/20231107/202311072357.a2ejf6Jb-lkp@intel.com/config)
compiler: powerpc64-linux-gcc (GCC) 13.2.0
reproduce: (https://download.01.org/0day-ci/archive/20231107/202311072357.a2ejf6Jb-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/202311072357.a2ejf6Jb-lkp@intel.com/

sparse warnings: (new ones prefixed by >>)
   kernel/bpf/helpers.c: note: in included file (through arch/powerpc/include/asm/pgtable-be-types.h, arch/powerpc/include/asm/page.h, arch/powerpc/include/asm/mmu.h, ...):
>> arch/powerpc/include/asm/cmpxchg.h:626:47: sparse: sparse: cast truncates bits from constant value (5deadbeef000eb9f becomes f000eb9f)
   arch/powerpc/include/asm/cmpxchg.h:628:48: sparse: sparse: cast truncates bits from constant value (5deadbeef000eb9f becomes f000eb9f)
>> arch/powerpc/include/asm/cmpxchg.h:626:47: sparse: sparse: cast truncates bits from constant value (5deadbeef000eb9f becomes f000eb9f)
   arch/powerpc/include/asm/cmpxchg.h:628:48: sparse: sparse: cast truncates bits from constant value (5deadbeef000eb9f becomes f000eb9f)
   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 +626 arch/powerpc/include/asm/cmpxchg.h

ae3a197e3d0bfe3 David Howells    2012-03-28  619  
ae3a197e3d0bfe3 David Howells    2012-03-28  620  static __always_inline unsigned long
da58b23cb976ab8 Michael Ellerman 2016-11-24  621  __cmpxchg(volatile void *ptr, unsigned long old, unsigned long new,
ae3a197e3d0bfe3 David Howells    2012-03-28  622  	  unsigned int size)
ae3a197e3d0bfe3 David Howells    2012-03-28  623  {
ae3a197e3d0bfe3 David Howells    2012-03-28  624  	switch (size) {
d0563a1297e234e Pan Xinhui       2016-04-27  625  	case 1:
d0563a1297e234e Pan Xinhui       2016-04-27 @626  		return __cmpxchg_u8(ptr, old, new);
d0563a1297e234e Pan Xinhui       2016-04-27  627  	case 2:
d0563a1297e234e Pan Xinhui       2016-04-27  628  		return __cmpxchg_u16(ptr, old, new);
ae3a197e3d0bfe3 David Howells    2012-03-28  629  	case 4:
ae3a197e3d0bfe3 David Howells    2012-03-28  630  		return __cmpxchg_u32(ptr, old, new);
ae3a197e3d0bfe3 David Howells    2012-03-28  631  #ifdef CONFIG_PPC64
ae3a197e3d0bfe3 David Howells    2012-03-28  632  	case 8:
ae3a197e3d0bfe3 David Howells    2012-03-28  633  		return __cmpxchg_u64(ptr, old, new);
ae3a197e3d0bfe3 David Howells    2012-03-28  634  #endif
ae3a197e3d0bfe3 David Howells    2012-03-28  635  	}
10d8b1480e6966b pan xinhui       2016-02-23  636  	BUILD_BUG_ON_MSG(1, "Unsupported size for __cmpxchg");
ae3a197e3d0bfe3 David Howells    2012-03-28  637  	return old;
ae3a197e3d0bfe3 David Howells    2012-03-28  638  }
ae3a197e3d0bfe3 David Howells    2012-03-28  639  

:::::: The code at line 626 was first introduced by commit
:::::: d0563a1297e234ed37f6b51c2e9321accebd1839 powerpc: Implement {cmp}xchg for u8 and u16

:::::: TO: Pan Xinhui <xinhui.pan@...ux.vnet.ibm.com>
:::::: CC: Michael Ellerman <mpe@...erman.id.au>

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