linux-kernel - include/linux/unaligned/be_byteshift.h:26:16: sparse: sparse: cast truncates bits from constant value (7fff becomes ff)

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Date:   Tue, 7 Jul 2020 23:40:17 +0800
From:   kernel test robot <lkp@...el.com>
To:     Luc Van Oostenryck <luc.vanoostenryck@...il.com>
Cc:     kbuild-all@...ts.01.org, linux-kernel@...r.kernel.org,
        Masahiro Yamada <yamada.masahiro@...ionext.com>
Subject: include/linux/unaligned/be_byteshift.h:26:16: sparse: sparse: cast
 truncates bits from constant value (7fff becomes ff)

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   bfe91da29bfad9941d5d703d45e29f0812a20724
commit: 80591e61a0f7e88deaada69844e4a31280c4a38f kbuild: tell sparse about the $ARCH
date:   8 months ago
config: alpha-randconfig-s032-20200707 (attached as .config)
compiler: alpha-linux-gcc (GCC) 9.3.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # apt-get install sparse
        # sparse version: v0.6.2-31-gabbfd661-dirty
        git checkout 80591e61a0f7e88deaada69844e4a31280c4a38f
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' ARCH=alpha 

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


sparse warnings: (new ones prefixed by >>)

   include/linux/unaligned/be_byteshift.h:26:16: sparse: sparse: cast truncates bits from constant value (800 becomes 0)
   include/linux/unaligned/be_byteshift.h:32:30: sparse: sparse: cast truncates bits from constant value (8000000 becomes 0)
   include/linux/unaligned/be_byteshift.h:26:16: sparse: sparse: cast truncates bits from constant value (800 becomes 0)
   include/linux/unaligned/be_byteshift.h:32:30: sparse: sparse: cast truncates bits from constant value (8000000 becomes 0)
>> include/linux/unaligned/be_byteshift.h:26:16: sparse: sparse: cast truncates bits from constant value (7fff becomes ff)
>> include/linux/unaligned/be_byteshift.h:32:30: sparse: sparse: cast truncates bits from constant value (7fffffff becomes ffff)
>> include/linux/unaligned/be_byteshift.h:38:30: sparse: sparse: cast truncates bits from constant value (7fffffffffffffff becomes ffffffff)

vim +26 include/linux/unaligned/be_byteshift.h

064106a91be5e76 Harvey Harrison 2008-04-29  22  
064106a91be5e76 Harvey Harrison 2008-04-29  23  static inline void __put_unaligned_be16(u16 val, u8 *p)
064106a91be5e76 Harvey Harrison 2008-04-29  24  {
064106a91be5e76 Harvey Harrison 2008-04-29  25  	*p++ = val >> 8;
064106a91be5e76 Harvey Harrison 2008-04-29 @26  	*p++ = val;
064106a91be5e76 Harvey Harrison 2008-04-29  27  }
064106a91be5e76 Harvey Harrison 2008-04-29  28  
064106a91be5e76 Harvey Harrison 2008-04-29  29  static inline void __put_unaligned_be32(u32 val, u8 *p)
064106a91be5e76 Harvey Harrison 2008-04-29  30  {
064106a91be5e76 Harvey Harrison 2008-04-29  31  	__put_unaligned_be16(val >> 16, p);
064106a91be5e76 Harvey Harrison 2008-04-29 @32  	__put_unaligned_be16(val, p + 2);
064106a91be5e76 Harvey Harrison 2008-04-29  33  }
064106a91be5e76 Harvey Harrison 2008-04-29  34  
064106a91be5e76 Harvey Harrison 2008-04-29  35  static inline void __put_unaligned_be64(u64 val, u8 *p)
064106a91be5e76 Harvey Harrison 2008-04-29  36  {
064106a91be5e76 Harvey Harrison 2008-04-29  37  	__put_unaligned_be32(val >> 32, p);
064106a91be5e76 Harvey Harrison 2008-04-29 @38  	__put_unaligned_be32(val, p + 4);
064106a91be5e76 Harvey Harrison 2008-04-29  39  }
064106a91be5e76 Harvey Harrison 2008-04-29  40  

:::::: The code at line 26 was first introduced by commit
:::::: 064106a91be5e76cb42c1ddf5d3871e3a1bd2a23 kernel: add common infrastructure for unaligned access

:::::: TO: Harvey Harrison <harvey.harrison@...il.com>
:::::: CC: Linus Torvalds <torvalds@...ux-foundation.org>

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

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