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SubjectRe: [PATCH v2] ftrace/x86: Load ftrace_ops in parameter not the variable holding it
(2013/11/14 5:20), Steven Rostedt wrote:
>
> Function tracing callbacks expect to have the ftrace_ops that registered it
> passed to them, not the address of the variable that holds the ftrace_ops
> that registered it.
>
> Use a mov instead of a lea to store the ftrace_ops into the parameter
> of the function tracing callback.

I see, function_trace_op is just a pointer to an actual ftrace_ops. :)
And I have ensured this change doesn't affect ftrace-kprobes since
it doesn't use this parameter.

> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>

Thank you,

> ---
> arch/x86/kernel/entry_32.S | 4 ++--
> arch/x86/kernel/entry_64.S | 2 +-
> 2 files changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S
> index f0dcb0c..15a569a 100644
> --- a/arch/x86/kernel/entry_32.S
> +++ b/arch/x86/kernel/entry_32.S
> @@ -1085,7 +1085,7 @@ ENTRY(ftrace_caller)
> pushl $0 /* Pass NULL as regs pointer */
> movl 4*4(%esp), %eax
> movl 0x4(%ebp), %edx
> - leal function_trace_op, %ecx
> + movl function_trace_op, %ecx
> subl $MCOUNT_INSN_SIZE, %eax
>
> .globl ftrace_call
> @@ -1143,7 +1143,7 @@ ENTRY(ftrace_regs_caller)
> movl 12*4(%esp), %eax /* Load ip (1st parameter) */
> subl $MCOUNT_INSN_SIZE, %eax /* Adjust ip */
> movl 0x4(%ebp), %edx /* Load parent ip (2nd parameter) */
> - leal function_trace_op, %ecx /* Save ftrace_pos in 3rd parameter */
> + movl function_trace_op, %ecx /* Save ftrace_pos in 3rd parameter */
> pushl %esp /* Save pt_regs as 4th parameter */
>
> GLOBAL(ftrace_regs_call)
> diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
> index b077f4c..9ce2567 100644
> --- a/arch/x86/kernel/entry_64.S
> +++ b/arch/x86/kernel/entry_64.S
> @@ -88,7 +88,7 @@ END(function_hook)
> MCOUNT_SAVE_FRAME \skip
>
> /* Load the ftrace_ops into the 3rd parameter */
> - leaq function_trace_op, %rdx
> + movq function_trace_op(%rip), %rdx
>
> /* Load ip into the first parameter */
> movq RIP(%rsp), %rdi
>


--
Masami HIRAMATSU
IT Management Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com




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