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SubjectRe: [PATCH 2/2] MIPS: mcount: Fix selfpc address for static trace
On Mon, 22 Sep 2014 14:32:59 +0100
Markos Chandras <markos.chandras@imgtec.com> wrote:

> According to Documentation/trace/ftrace-design.txt, the selfpc
> should be the return address minus the mcount overhead (8 bytes).
> This brings static trace in line with the dynamic trace regarding
> the selfpc argument to the tracing function.
>
> This also removes the magic number '8' with the proper
> MCOUNT_INSN_SIZE.

I could also update the generic code to handle delay slots.

-- Steve

>
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Cc: linux-kernel@vger.kernel.org
> Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
> ---
> arch/mips/kernel/mcount.S | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/mips/kernel/mcount.S b/arch/mips/kernel/mcount.S
> index 2f7c734771f4..3af48b7c7a47 100644
> --- a/arch/mips/kernel/mcount.S
> +++ b/arch/mips/kernel/mcount.S
> @@ -79,7 +79,7 @@ _mcount:
> PTR_S MCOUNT_RA_ADDRESS_REG, PT_R12(sp)
> #endif
>
> - PTR_SUBU a0, ra, 8 /* arg1: self address */
> + PTR_SUBU a0, ra, MCOUNT_INSN_SIZE /* arg1: self address */
> PTR_LA t1, _stext
> sltu t2, a0, t1 /* t2 = (a0 < _stext) */
> PTR_LA t1, _etext
> @@ -138,7 +138,7 @@ NESTED(_mcount, PT_SIZE, ra)
> static_trace:
> MCOUNT_SAVE_REGS
>
> - move a0, ra /* arg1: self return address */
> + PTR_SUBU a0, ra, MCOUNT_INSN_SIZE /* arg1: self address */
> jalr t2 /* (1) call *ftrace_trace_function */
> move a1, AT /* arg2: parent's return address */
>



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