The patch titled
Subject: bitops: avoid integer overflow in GENMASK(_ULL)
has been added to the -mm tree. Its filename is
bitops-avoid-integer-overflow-in-genmask_ull.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/bitops-avoid-integer-overflow-in-genmask_ull.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/bitops-avoid-integer-overflow-in-genmask_ull.patch
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------------------------------------------------------
From: Matthias Kaehlcke <mka@xxxxxxxxxxxx>
Subject: bitops: avoid integer overflow in GENMASK(_ULL)
GENMASK(_ULL) performs a left-shift of ~0UL(L), which technically results
in an integer overflow. clang raises a warning if the overflow occurs in
a preprocessor expression. Clear the low-order bits through a
substraction instead of the left-shift to avoid the overflow.
(akpm: no change in .text size in my testing)
Link: http://lkml.kernel.org/r/20170803212020.24939-1-mka@xxxxxxxxxxxx
Signed-off-by: Matthias Kaehlcke <mka@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/bitops.h | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff -puN include/linux/bitops.h~bitops-avoid-integer-overflow-in-genmask_ull include/linux/bitops.h
--- a/include/linux/bitops.h~bitops-avoid-integer-overflow-in-genmask_ull
+++ a/include/linux/bitops.h
@@ -19,10 +19,11 @@
* GENMASK_ULL(39, 21) gives us the 64bit vector 0x000000ffffe00000.
*/
#define GENMASK(h, l) \
- (((~0UL) << (l)) & (~0UL >> (BITS_PER_LONG - 1 - (h))))
+ (((~0UL) - (1UL << (l)) + 1) & (~0UL >> (BITS_PER_LONG - 1 - (h))))
#define GENMASK_ULL(h, l) \
- (((~0ULL) << (l)) & (~0ULL >> (BITS_PER_LONG_LONG - 1 - (h))))
+ (((~0ULL) - (1ULL << (l)) + 1) & \
+ (~0ULL >> (BITS_PER_LONG_LONG - 1 - (h))))
extern unsigned int __sw_hweight8(unsigned int w);
extern unsigned int __sw_hweight16(unsigned int w);
_
Patches currently in -mm which might be from mka@xxxxxxxxxxxx are
mm-memcontrol-use-int-for-event-state-parameter-in-several-functions.patch
mm-memcontrol-use-int-for-event-state-parameter-in-several-functions-v2.patch
bitops-avoid-integer-overflow-in-genmask_ull.patch
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