From 00b4d9a14125f1e51874def2b9de6092e007412d Mon Sep 17 00:00:00 2001 From: Maxime COQUELIN Date: Thu, 6 Nov 2014 10:54:19 +0100 Subject: [PATCH] bitops: Fix shift overflow in GENMASK macros 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. Reported-by: Eric Paire Suggested-by: Rasmus Villemoes Signed-off-by: Maxime Coquelin Signed-off-by: Peter Zijlstra (Intel) Cc: # v3.13+ Cc: linux@rasmusvillemoes.dk Cc: gong.chen@linux.intel.com Cc: John Sullivan Cc: Linus Torvalds Cc: Paul E. McKenney Cc: Theodore Ts'o Fixes: 10ef6b0dffe4 ("bitops: Introduce a more generic BITMASK macro") Link: http://lkml.kernel.org/r/1415267659-10563-1-git-send-email-maxime.coquelin@st.com Signed-off-by: Ingo Molnar --- 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 be5fd38bd5a0..5d858e02997f 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) << (l)) & (~0UL >> (BITS_PER_LONG - 1 - (h)))) + +#define GENMASK_ULL(h, l) \ + (((~0ULL) << (l)) & (~0ULL >> (BITS_PER_LONG_LONG - 1 - (h)))) extern unsigned int __sw_hweight8(unsigned int w); extern unsigned int __sw_hweight16(unsigned int w);