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bitfield.h: Fix "type of reg too small for mask" test

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[ Upstream commit bff8c3848e ]

The test: 'mask > (typeof(_reg))~0ull' only works correctly when both
sides are unsigned, consider:

 - 0xff000000 vs (int)~0ull
 - 0x000000ff vs (int)~0ull

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lore.kernel.org/r/20211110101324.950210584@infradead.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Peter Zijlstra 2021-11-10 11:01:03 +01:00 • committed by Justin Hammond
parent a4dda0e9d9
commit 1e08ae5a59
1 changed files with 18 additions and 1 deletions
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19
include/linux/bitfield.h
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@ -41,6 +41,22 @@
#define __bf_shf(x) (__builtin_ffsll(x) - 1)
#define __scalar_type_to_unsigned_cases(type) \
unsigned type: (unsigned type)0, \
signed type: (unsigned type)0
#define __unsigned_scalar_typeof(x) typeof( \
_Generic((x), \
char: (unsigned char)0, \
__scalar_type_to_unsigned_cases(char), \
__scalar_type_to_unsigned_cases(short), \
__scalar_type_to_unsigned_cases(int), \
__scalar_type_to_unsigned_cases(long), \
__scalar_type_to_unsigned_cases(long long), \
default: (x)))
#define __bf_cast_unsigned(type, x) ((__unsigned_scalar_typeof(type))(x))
#define __BF_FIELD_CHECK(_mask, _reg, _val, _pfx) \
({ \
BUILD_BUG_ON_MSG(!__builtin_constant_p(_mask), \
@ -49,7 +65,8 @@
BUILD_BUG_ON_MSG(__builtin_constant_p(_val) ? \
~((_mask) >> __bf_shf(_mask)) & (_val) : 0, \
_pfx "value too large for the field"); \
BUILD_BUG_ON_MSG((_mask) > (typeof(_reg))~0ull, \
BUILD_BUG_ON_MSG(__bf_cast_unsigned(_mask, _mask) > \
__bf_cast_unsigned(_reg, ~0ull), \
_pfx "type of reg too small for mask"); \
__BUILD_BUG_ON_NOT_POWER_OF_2((_mask) + \
(1ULL << __bf_shf(_mask))); \