Messages in this thread Patch in this message | | | From | Maxime COQUELIN <> | Subject | [PATCH v3] bitops: Fix shift overflow in GENMASK macros | Date | Tue, 4 Nov 2014 11:58:17 +0100 |
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On some 32 bits architectures, including x86, GENMASK(31, 0) returns 0 instead of the expected ~0UL.
This is the same on some 64 bits architectures with GENMASK_ULL(63, 0).
This is due to an overflow in the shift operand, 1 << 32 for GENMASK, 1 << 64 for GENMASK_ULL.
Fixes: 10ef6b0dffe404bcc54e94cb2ca1a5b18445a66b Cc: <stable@vger.kernel.org> #v3.13+ Reported-by: Eric Paire <eric.paire@st.com> Suggested-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Maxime Coquelin <maxime.coquelin@st.com> --- include/linux/bitops.h | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/include/linux/bitops.h b/include/linux/bitops.h index be5fd38..c2ce66c 100644 --- a/include/linux/bitops.h +++ b/include/linux/bitops.h @@ -18,8 +18,11 @@ * position @h. For example * GENMASK_ULL(39, 21) gives us the 64bit vector 0x000000ffffe00000. */ -#define GENMASK(h, l) (((U32_C(1) << ((h) - (l) + 1)) - 1) << (l)) -#define GENMASK_ULL(h, l) (((U64_C(1) << ((h) - (l) + 1)) - 1) << (l)) +#define GENMASK(h, l) \ + ((~0UL >> (BITS_PER_LONG - ((h) - (l) + 1))) << (l)) + +#define GENMASK_ULL(h, l) \ + ((~0ULL >> (BITS_PER_LONG_LONG - ((h) - (l) + 1))) << (l)) extern unsigned int __sw_hweight8(unsigned int w); extern unsigned int __sw_hweight16(unsigned int w); -- 1.9.1
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