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authorMatthias Kaehlcke <mka@chromium.org>2017-09-08 16:14:33 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2017-09-08 18:26:48 -0700
commitc32ee3d9abd284b4fcaacc250b101f93829c7bae (patch)
tree14da37d4c3debe116e378f3de20099babf0de1c3 /include/linux/bitops.h
parente9ef073a0796e46c24f037237291efe56fc28ad9 (diff)
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@chromium.org Signed-off-by: Matthias Kaehlcke <mka@chromium.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/bitops.h')
-rw-r--r--include/linux/bitops.h5
1 files changed, 3 insertions, 2 deletions
diff --git a/include/linux/bitops.h b/include/linux/bitops.h
index a83c822c35c2..8fbe259b197c 100644
--- a/include/linux/bitops.h
+++ b/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);