[PATCH] Revert "x86/uaccess: Add stack frame output operand in get_user() inline asm"

[Matthias Kaehlcke]

Commit f05058c4d652 supposedly "forces a stack frame to be created before
the inline asm code if CONFIG_FRAME_POINTER is enabled by listing the
stack pointer as an output operand for the get_user() inline assembly
statement.". This doesn't work as intended, at least with gcc v4.9.2 and
x86-64 the generated code is exactly the same with and without the patch.
However clang adds an extra instruction that adjusts %rsp, which ends up
causing double faults all over the place.

Signed-off-by: Matthias Kaehlcke <mka@xxxxxxxxxxxx>
---
 arch/x86/include/asm/uaccess.h | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index 476ea27f490b..9ec2beab73df 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -161,11 +161,10 @@ __typeof__(__builtin_choose_expr(sizeof(x) > sizeof(0UL), 0ULL, 0UL))
 ({									\
 	int __ret_gu;							\
 	register __inttype(*(ptr)) __val_gu asm("%"_ASM_DX);		\
-	register void *__sp asm(_ASM_SP);				\
 	__chk_user_ptr(ptr);						\
 	might_fault();							\
-	asm volatile("call __get_user_%P4"				\
-		     : "=a" (__ret_gu), "=r" (__val_gu), "+r" (__sp)	\
+	asm volatile("call __get_user_%P3"				\
+		     : "=a" (__ret_gu), "=r" (__val_gu)			\
 		     : "0" (ptr), "i" (sizeof(*(ptr))));		\
 	(x) = (__force __typeof__(*(ptr))) __val_gu;			\
 	__builtin_expect(__ret_gu, 0);					\
-- 
2.13.2.932.g7449e964c-goog