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tracing, x86: fix constraint for parent variable

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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>
This commit is contained in:
Steven Rostedt 2009-02-10 11:53:23 -05:00
parent 667d241258
commit 966657883f
1 changed files with 4 additions and 5 deletions
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9
arch/x86/kernel/ftrace.c
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@ -468,8 +468,8 @@ 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"
".section .fixup, \"ax\"\n"
@ -479,9 +479,8 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr)
_ASM_EXTABLE(1b, 3b)
_ASM_EXTABLE(2b, 3b)
: [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"
);