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authorJosh Poimboeuf <jpoimboe@redhat.com>2020-04-06 20:09:43 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2020-04-07 10:43:42 -0700
commitf80ac98a641a03097cbc9fdfd4b6a41a8dd3b7ae (patch)
tree50d8821dc2475f01828f2467707a6572e89e8a0e
parent6680125ea5a2a5a69eeb8f7dcd89d0a1d23998ce (diff)
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>
-rw-r--r--include/linux/bitops.h4
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;