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Commit 352affc3 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Greg Kroah-Hartman
Browse files

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



[ Upstream commit bff8c3848e071d387d8b0784dc91fa49cd563774 ]

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: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
Link: https://lore.kernel.org/r/20211110101324.950210584@infradead.org


Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 0a0fbbd6

include/linux/bitfield.h

+18 −1
Original line number Diff line number Diff line
@@ -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))); \