tracing, x86: fix constraint for parent variable

The constraint used for retrieving and restoring the parent function
pointer is incorrect. The parent variable is a pointer, and the
address of the pointer is modified by the asm statement and not
the pointer itself. It is incorrect to pass it in as an output
constraint since the asm will never update the pointer.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 4 insertions, 5 deletions

diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index 9d549e4fe880..231bdd3c5b1c 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -488,8 +488,8 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr)
 	 * ignore such a protection.
 	 */
 	asm volatile(
-		"1: " _ASM_MOV " (%[parent_old]), %[old]\n"
-		"2: " _ASM_MOV " %[return_hooker], (%[parent_replaced])\n"
+		"1: " _ASM_MOV " (%[parent]), %[old]\n"
+		"2: " _ASM_MOV " %[return_hooker], (%[parent])\n"
 		"   movl $0, %[faulted]\n"
 		"3:\n"
 
@@ -501,9 +501,8 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr)
 		_ASM_EXTABLE(1b, 4b)
 		_ASM_EXTABLE(2b, 4b)
 
-		: [parent_replaced] "=r" (parent), [old] "=r" (old),
-		  [faulted] "=r" (faulted)
-		: [parent_old] "0" (parent), [return_hooker] "r" (return_hooker)
+		: [old] "=r" (old), [faulted] "=r" (faulted)
+		: [parent] "r" (parent), [return_hooker] "r" (return_hooker)
 		: "memory"
 	);