Commit 00b4d9a1 authored Nov 06, 2014 by Maxime COQUELIN Committed by Ingo Molnar Nov 16, 2014

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 <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: <stable@vger.kernel.org> # v3.13+
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: 10ef6b0d ("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>

parent 206c5f60

include/linux/bitops.h

+5 −2

Original line number	Diff line number	Diff line
		@@ -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);

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