[PATCH 5.10 085/105] bitfield.h: Fix "type of reg too small for mask" test
From: Greg Kroah-Hartman
Date: Wed Jul 27 2022 - 12:55:56 EST
From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
[ 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: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Reviewed-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20211110101324.950210584@xxxxxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
include/linux/bitfield.h | 19 ++++++++++++++++++-
1 file changed, 18 insertions(+), 1 deletion(-)
diff --git a/include/linux/bitfield.h b/include/linux/bitfield.h
index 4e035aca6f7e..6093fa6db260 100644
--- a/include/linux/bitfield.h
+++ b/include/linux/bitfield.h
@@ -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))); \
--
2.35.1