[tip:locking/rcuref 2/2] include/asm-generic/cmpxchg-local.h:30:42: sparse: sparse: cast truncates bits from constant value (e0000000 becomes 0)

From: kernel test robot
Date: Mon Apr 03 2023 - 00:10:09 EST

tree: https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git locking/rcuref
head: ee1ee6db07795d9637bc5e8993a8ddcf886541ef
commit: ee1ee6db07795d9637bc5e8993a8ddcf886541ef [2/2] atomics: Provide rcuref - scalable reference counting
config: nios2-randconfig-s042-20230402 (https://download.01.org/0day-ci/archive/20230403/202304031213.U9LRonKm-lkp@xxxxxxxxx/config)
compiler: nios2-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/tip/tip.git/commit/?id=ee1ee6db07795d9637bc5e8993a8ddcf886541ef
git remote add tip https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git
git fetch --no-tags tip locking/rcuref
git checkout ee1ee6db07795d9637bc5e8993a8ddcf886541ef
# save the config file
mkdir build_dir && cp config build_dir/.config
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' O=build_dir ARCH=nios2 olddefconfig
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' O=build_dir ARCH=nios2 SHELL=/bin/bash

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@xxxxxxxxx>
| Link: https://lore.kernel.org/oe-kbuild-all/202304031213.U9LRonKm-lkp@xxxxxxxxx/

sparse warnings: (new ones prefixed by >>)
lib/rcuref.c: note: in included file (through include/asm-generic/cmpxchg.h, arch/nios2/include/generated/asm/cmpxchg.h, include/asm-generic/atomic.h, ...):
>> include/asm-generic/cmpxchg-local.h:30:42: sparse: sparse: cast truncates bits from constant value (e0000000 becomes 0)
include/asm-generic/cmpxchg-local.h:34:44: sparse: sparse: cast truncates bits from constant value (e0000000 becomes 0)

vim +30 include/asm-generic/cmpxchg-local.h

068fbad288a2c1 Mathieu Desnoyers 2008-02-07 7
aa93685afbefa0 Behan Webster 2012-11-20 8 extern unsigned long wrong_size_cmpxchg(volatile void *ptr)
aa93685afbefa0 Behan Webster 2012-11-20 9 __noreturn;
068fbad288a2c1 Mathieu Desnoyers 2008-02-07 10
068fbad288a2c1 Mathieu Desnoyers 2008-02-07 11 /*
068fbad288a2c1 Mathieu Desnoyers 2008-02-07 12 * Generic version of __cmpxchg_local (disables interrupts). Takes an unsigned
068fbad288a2c1 Mathieu Desnoyers 2008-02-07 13 * long parameter, supporting various types of architectures.
068fbad288a2c1 Mathieu Desnoyers 2008-02-07 14 */
6988631bdfddce Mark Rutland 2021-05-25 15 static inline unsigned long __generic_cmpxchg_local(volatile void *ptr,
068fbad288a2c1 Mathieu Desnoyers 2008-02-07 16 unsigned long old, unsigned long new, int size)
068fbad288a2c1 Mathieu Desnoyers 2008-02-07 17 {
068fbad288a2c1 Mathieu Desnoyers 2008-02-07 18 unsigned long flags, prev;
068fbad288a2c1 Mathieu Desnoyers 2008-02-07 19
068fbad288a2c1 Mathieu Desnoyers 2008-02-07 20 /*
068fbad288a2c1 Mathieu Desnoyers 2008-02-07 21 * Sanity checking, compile-time.
068fbad288a2c1 Mathieu Desnoyers 2008-02-07 22 */
068fbad288a2c1 Mathieu Desnoyers 2008-02-07 23 if (size == 8 && sizeof(unsigned long) != 8)
068fbad288a2c1 Mathieu Desnoyers 2008-02-07 24 wrong_size_cmpxchg(ptr);
068fbad288a2c1 Mathieu Desnoyers 2008-02-07 25
5042afe7fe3239 Ingo Molnar 2009-07-03 26 raw_local_irq_save(flags);
068fbad288a2c1 Mathieu Desnoyers 2008-02-07 27 switch (size) {
068fbad288a2c1 Mathieu Desnoyers 2008-02-07 28 case 1: prev = *(u8 *)ptr;
6246541522845a Matt Evans 2023-02-01 29 if (prev == (u8)old)
068fbad288a2c1 Mathieu Desnoyers 2008-02-07 @30 *(u8 *)ptr = (u8)new;
068fbad288a2c1 Mathieu Desnoyers 2008-02-07 31 break;
068fbad288a2c1 Mathieu Desnoyers 2008-02-07 32 case 2: prev = *(u16 *)ptr;
6246541522845a Matt Evans 2023-02-01 33 if (prev == (u16)old)
068fbad288a2c1 Mathieu Desnoyers 2008-02-07 34 *(u16 *)ptr = (u16)new;
068fbad288a2c1 Mathieu Desnoyers 2008-02-07 35 break;
068fbad288a2c1 Mathieu Desnoyers 2008-02-07 36 case 4: prev = *(u32 *)ptr;
6246541522845a Matt Evans 2023-02-01 37 if (prev == (u32)old)
068fbad288a2c1 Mathieu Desnoyers 2008-02-07 38 *(u32 *)ptr = (u32)new;
068fbad288a2c1 Mathieu Desnoyers 2008-02-07 39 break;
068fbad288a2c1 Mathieu Desnoyers 2008-02-07 40 case 8: prev = *(u64 *)ptr;
068fbad288a2c1 Mathieu Desnoyers 2008-02-07 41 if (prev == old)
068fbad288a2c1 Mathieu Desnoyers 2008-02-07 42 *(u64 *)ptr = (u64)new;
068fbad288a2c1 Mathieu Desnoyers 2008-02-07 43 break;
068fbad288a2c1 Mathieu Desnoyers 2008-02-07 44 default:
068fbad288a2c1 Mathieu Desnoyers 2008-02-07 45 wrong_size_cmpxchg(ptr);
068fbad288a2c1 Mathieu Desnoyers 2008-02-07 46 }
5042afe7fe3239 Ingo Molnar 2009-07-03 47 raw_local_irq_restore(flags);
068fbad288a2c1 Mathieu Desnoyers 2008-02-07 48 return prev;
068fbad288a2c1 Mathieu Desnoyers 2008-02-07 49 }
068fbad288a2c1 Mathieu Desnoyers 2008-02-07 50

:::::: The code at line 30 was first introduced by commit
:::::: 068fbad288a2c18b75b0425fb56d241f018a1cb5 Add cmpxchg_local to asm-generic for per cpu atomic operations

:::::: TO: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxx>
:::::: CC: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxxxxxxxx>

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