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| author |   Josh Poimboeuf <jpoimboe@redhat.com> | 2020-04-06 20:09:43 -0700 |
|---|---|---|
| committer |   Linus Torvalds <torvalds@linux-foundation.org> | 2020-04-07 10:43:42 -0700 |
| commit | f80ac98a641a03097cbc9fdfd4b6a41a8dd3b7ae (patch) | |
| tree | 50d8821dc2475f01828f2467707a6572e89e8a0e /include/linux/bitops.h | |
| parent | MAINTAINERS: list the section entries in the preferred order (diff) | |
| download | wireguard-linux-f80ac98a641a03097cbc9fdfd4b6a41a8dd3b7ae.tar.xz wireguard-linux-f80ac98a641a03097cbc9fdfd4b6a41a8dd3b7ae.zip | |
bitops: always inline sign extension helpers
With CONFIG_CC_OPTIMIZE_FOR_SIZE, objtool reports:
drivers/gpu/drm/i915/gem/i915_gem_execbuffer.o: warning: objtool: i915_gem_execbuffer2_ioctl()+0x5b7: call to gen8_canonical_addr() with UACCESS enabled
This means i915_gem_execbuffer2_ioctl() is calling gen8_canonical_addr()
from the user_access_begin/end critical region (i.e, with SMAP disabled).
While it's probably harmless in this case, in general we like to avoid
extra function calls in SMAP-disabled regions because it can open up
inadvertent security holes.
Fix the warning by changing the sign extension helpers to __always_inline.
This convinces GCC to inline gen8_canonical_addr().
The sign extension functions are trivial anyway, so it makes sense to
always inline them. With my test optimize-for-size-based config, this
actually shrinks the text size of i915_gem_execbuffer.o by 45 bytes -- and
no change for vmlinux.
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Link: http://lkml.kernel.org/r/740179324b2b18b750b16295c48357f00b5fa9ed.1582982020.git.jpoimboe@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/bitops.h')
| -rw-r--r-- | include/linux/bitops.h | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/include/linux/bitops.h b/include/linux/bitops.h index 47f54b459c26..9acf654f0b19 100644 --- a/include/linux/bitops.h +++ b/include/linux/bitops.h @@ -162,7 +162,7 @@ static inline __u8 ror8(__u8 word, unsigned int shift) * * This is safe to use for 16- and 8-bit types as well. */ -static inline __s32 sign_extend32(__u32 value, int index) +static __always_inline __s32 sign_extend32(__u32 value, int index) { __u8 shift = 31 - index; return (__s32)(value << shift) >> shift; @@ -173,7 +173,7 @@ static inline __s32 sign_extend32(__u32 value, int index) * @value: value to sign extend * @index: 0 based bit index (0<=index<64) to sign bit */ -static inline __s64 sign_extend64(__u64 value, int index) +static __always_inline __s64 sign_extend64(__u64 value, int index) { __u8 shift = 63 - index; return (__s64)(value << shift) >> shift; |