Commit-ID: a76cf66e948afbaeda8e3ecc861f29c47a026c27
Gitweb: http://git.kernel.org/tip/a76cf66e948afbaeda8e3ecc861f29c47a026c27
Author: Andy Lutomirski <[email protected]>
AuthorDate: Mon, 5 Oct 2015 17:47:49 -0700
Committer: Ingo Molnar <[email protected]>
CommitDate: Wed, 7 Oct 2015 11:34:06 +0200
x86/uaccess: Tell the compiler that uaccess is unlikely to fault
GCC doesn't realize that get_user(), put_user(), and their __
variants are unlikely to fail. Tell it.
I noticed this while playing with the C entry code.
Before:
text data bss dec filename
21828763 5194760 1277952 28301475 vmlinux.baseline
After:
text data bss dec filename
21828379 5194760 1277952 28301091 vmlinux.new
The generated code shrunk by 384 bytes.
Signed-off-by: Andy Lutomirski <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Brian Gerst <[email protected]>
Cc: Denys Vlasenko <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Link:
http://lkml.kernel.org/r/dc37bed7024319c3004d950d57151fca6aeacf97.1444091584.git.l...@kernel.org
Signed-off-by: Ingo Molnar <[email protected]>
---
arch/x86/include/asm/uaccess.h | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index a8df874..3e911c6 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -182,7 +182,7 @@ __typeof__(__builtin_choose_expr(sizeof(x) > sizeof(0UL),
0ULL, 0UL))
: "=a" (__ret_gu), "=r" (__val_gu) \
: "0" (ptr), "i" (sizeof(*(ptr)))); \
(x) = (__force __typeof__(*(ptr))) __val_gu; \
- __ret_gu; \
+ __builtin_expect(__ret_gu, 0); \
})
#define __put_user_x(size, x, ptr, __ret_pu) \
@@ -278,7 +278,7 @@ extern void __put_user_8(void);
__put_user_x(X, __pu_val, ptr, __ret_pu); \
break; \
} \
- __ret_pu; \
+ __builtin_expect(__ret_pu, 0); \
})
#define __put_user_size(x, ptr, size, retval, errret) \
@@ -401,7 +401,7 @@ do {
\
({ \
int __pu_err; \
__put_user_size((x), (ptr), (size), __pu_err, -EFAULT); \
- __pu_err; \
+ __builtin_expect(__pu_err, 0); \
})
#define __get_user_nocheck(x, ptr, size) \
@@ -410,7 +410,7 @@ do {
\
unsigned long __gu_val; \
__get_user_size(__gu_val, (ptr), (size), __gu_err, -EFAULT); \
(x) = (__force __typeof__(*(ptr)))__gu_val; \
- __gu_err; \
+ __builtin_expect(__gu_err, 0); \
})
/* FIXME: this hack is definitely wrong -AK */
--
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