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| author |   Matthias Kaehlcke <mka@chromium.org> | 2017-09-08 16:14:33 -0700 |
|---|---|---|
| committer |   Linus Torvalds <torvalds@linux-foundation.org> | 2017-09-08 18:26:48 -0700 |
| commit | c32ee3d9abd284b4fcaacc250b101f93829c7bae (patch) | |
| tree | 14da37d4c3debe116e378f3de20099babf0de1c3 /include/linux/bitops.h | |
| parent | include: warn for inconsistent endian config definition (diff) | |
| download | linux-dev-c32ee3d9abd284b4fcaacc250b101f93829c7bae.tar.xz linux-dev-c32ee3d9abd284b4fcaacc250b101f93829c7bae.zip | |
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.h | 5 |
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); |