| From | Kamal Mostafa <> | Subject | [PATCH 3.13.y-ckt 104/121] bitops: Fix shift overflow in GENMASK macros | Date | Tue, 2 Dec 2014 11:19:43 -0800 |
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3.13.11-ckt12 -stable review patch. If anyone has any objections, please let me know.
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From: Maxime COQUELIN <maxime.coquelin@st.com>
commit 00b4d9a14125f1e51874def2b9de6092e007412d upstream.
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 <eric.paire@st.com> Suggested-by: Rasmus Villemoes <linux@rasmusvillemoes.dk> Signed-off-by: Maxime Coquelin <maxime.coquelin@st.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: linux@rasmusvillemoes.dk Cc: gong.chen@linux.intel.com Cc: John Sullivan <jsrhbz@kanargh.force9.co.uk> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Theodore Ts'o <tytso@mit.edu> 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 <mingo@kernel.org> Signed-off-by: Kamal Mostafa <kamal@canonical.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..5d858e0 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); -- 1.9.1
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