queue-4.9/0012-bitops-avoid-integer-overflow-in-GENMASK-_ULL.patch

   1 From a2783e3dab88b3062ed1612187b90c7fc36d67a9 Mon Sep 17 00:00:00 2001
   2 From: Matthias Kaehlcke <mka@chromium.org>
   3 Date: Fri, 8 Sep 2017 16:14:33 -0700
   4 Subject: [PATCH 12/76] bitops: avoid integer overflow in GENMASK(_ULL)
   5
   6 commit c32ee3d9abd284b4fcaacc250b101f93829c7bae upstream.
   7
   8 GENMASK(_ULL) performs a left-shift of ~0UL(L), which technically
   9 results in an integer overflow.  clang raises a warning if the overflow
  10 occurs in a preprocessor expression.  Clear the low-order bits through a
  11 substraction instead of the left-shift to avoid the overflow.
  12
  13 (akpm: no change in .text size in my testing)
  14
  15 Link: http://lkml.kernel.org/r/20170803212020.24939-1-mka@chromium.org
  16 Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
  17 Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
  18 Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
  19 Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
  20 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  21 ---
  22  include/linux/bitops.h | 5 +++--
  23  1 file changed, 3 insertions(+), 2 deletions(-)
  24
  25 diff --git a/include/linux/bitops.h b/include/linux/bitops.h
  26 index a83c822c35c2..8fbe259b197c 100644
  27 --- a/include/linux/bitops.h
  28 +++ b/include/linux/bitops.h
  29 @@ -19,10 +19,11 @@
  30   * GENMASK_ULL(39, 21) gives us the 64bit vector 0x000000ffffe00000.
  31   */
  32  #define GENMASK(h, l) \
  33 -       (((~0UL) << (l)) & (~0UL >> (BITS_PER_LONG - 1 - (h))))
  34 +       (((~0UL) - (1UL << (l)) + 1) & (~0UL >> (BITS_PER_LONG - 1 - (h))))
  35
  36  #define GENMASK_ULL(h, l) \
  37 -       (((~0ULL) << (l)) & (~0ULL >> (BITS_PER_LONG_LONG - 1 - (h))))
  38 +       (((~0ULL) - (1ULL << (l)) + 1) & \
  39 +        (~0ULL >> (BITS_PER_LONG_LONG - 1 - (h))))
  40
  41  extern unsigned int __sw_hweight8(unsigned int w);
  42  extern unsigned int __sw_hweight16(unsigned int w);
  43 --
  44 2.21.0
  45