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authorAndy Lutomirski <luto@kernel.org>2015-10-06 03:47:49 +0300
committerIngo Molnar <mingo@kernel.org>2015-10-07 12:34:06 +0300
commita76cf66e948afbaeda8e3ecc861f29c47a026c27 (patch)
treec0d0516f043b138d3172f3324eaf7bc1ed33e928 /arch/x86/include/asm/uaccess.h
parent25a9a924c0c8723ced99179eb639e8c5372a2557 (diff)
downloadlinux-a76cf66e948afbaeda8e3ecc861f29c47a026c27.tar.xz
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 <luto@kernel.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-kernel@vger.kernel.org Link: http://lkml.kernel.org/r/dc37bed7024319c3004d950d57151fca6aeacf97.1444091584.git.luto@kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/include/asm/uaccess.h')
-rw-r--r--arch/x86/include/asm/uaccess.h8
1 files changed, 4 insertions, 4 deletions
diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index a8df874f3e88..3e911c68876e 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 */