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>
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@ -488,8 +488,8 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr)
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* ignore such a protection.
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*/
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asm volatile(
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"1: " _ASM_MOV " (%[parent_old]), %[old]\n"
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"2: " _ASM_MOV " %[return_hooker], (%[parent_replaced])\n"
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"1: " _ASM_MOV " (%[parent]), %[old]\n"
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"2: " _ASM_MOV " %[return_hooker], (%[parent])\n"
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" movl $0, %[faulted]\n"
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"3:\n"
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@ -501,9 +501,8 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr)
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_ASM_EXTABLE(1b, 4b)
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_ASM_EXTABLE(2b, 4b)
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: [parent_replaced] "=r" (parent), [old] "=r" (old),
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[faulted] "=r" (faulted)
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: [parent_old] "0" (parent), [return_hooker] "r" (return_hooker)
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: [old] "=r" (old), [faulted] "=r" (faulted)
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: [parent] "r" (parent), [return_hooker] "r" (return_hooker)
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: "memory"
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);
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