Commit-ID: 00b4d9a14125f1e51874def2b9de6092e007412d
Gitweb: http://git.kernel.org/tip/00b4d9a14125f1e51874def2b9de6092e007412d
Author: Maxime COQUELIN <maxime.coque...@st.com>
AuthorDate: Thu, 6 Nov 2014 10:54:19 +0100
Committer: Ingo Molnar <mi...@kernel.org>
CommitDate: Sun, 16 Nov 2014 09:55:39 +0100
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.pa...@st.com>
Suggested-by: Rasmus Villemoes <li...@rasmusvillemoes.dk>
Signed-off-by: Maxime Coquelin <maxime.coque...@st.com>
Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org>
Cc: <sta...@vger.kernel.org> # v3.13+
Cc: li...@rasmusvillemoes.dk
Cc: gong.c...@linux.intel.com
Cc: John Sullivan <jsr...@kanargh.force9.co.uk>
Cc: Linus Torvalds <torva...@linux-foundation.org>
Cc: Paul E. McKenney <paul...@linux.vnet.ibm.com>
Cc: Theodore Ts'o <ty...@mit.edu>
Fixes: 10ef6b0dffe4 ("bitops: Introduce a more generic BITMASK macro")
Link:
http://lkml.kernel.org/r/1415267659-10563-1-git-send-email-maxime.coque...@st.com
Signed-off-by: Ingo Molnar <mi...@kernel.org>
---
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);
--
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