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SubjectRe: [PATCH v2 08/13] powerpc/ftrace: Prepare PPC64's ftrace_caller() for CONFIG_DYNAMIC_FTRACE_WITH_ARGS
Hi Christophe,
Thanks for your work enabling DYNAMIC_FTRACE_WITH_ARGS on powerpc. Sorry
for the late review on this series, but I have a few comments below.


Christophe Leroy wrote:
> In order to implement CONFIG_DYNAMIC_FTRACE_WITH_ARGS, change ftrace_caller()
> to handle LIVEPATCH the same way as frace_caller_regs().
>
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
> .../powerpc/kernel/trace/ftrace_64_mprofile.S | 25 ++++++++++++++-----
> 1 file changed, 19 insertions(+), 6 deletions(-)

I think we also need to save r1 into pt_regs so that the stack pointer
is available in the callbacks.

Other than that, a few minor nits below...

>
> diff --git a/arch/powerpc/kernel/trace/ftrace_64_mprofile.S b/arch/powerpc/kernel/trace/ftrace_64_mprofile.S
> index d636fc755f60..f6f787819273 100644
> --- a/arch/powerpc/kernel/trace/ftrace_64_mprofile.S
> +++ b/arch/powerpc/kernel/trace/ftrace_64_mprofile.S
> @@ -172,14 +172,19 @@ _GLOBAL(ftrace_caller)
> addi r3, r3, function_trace_op@toc@l
> ld r5, 0(r3)
>
> +#ifdef CONFIG_LIVEPATCH_64
> + SAVE_GPR(14, r1)
> + mr r14,r7 /* remember old NIP */
^ add a space
> +#endif

Please add a blank line here, to match the formatting for the rest of
this file.

> /* Calculate ip from nip-4 into r3 for call below */
> subi r3, r7, MCOUNT_INSN_SIZE
>
> /* Put the original return address in r4 as parent_ip */
> + std r0, _LINK(r1)
> mr r4, r0
>
> - /* Set pt_regs to NULL */
> - li r6, 0
> + /* Load &pt_regs in r6 for call below */
> + addi r6, r1 ,STACK_FRAME_OVERHEAD
^^ incorrect spacing
>
> /* ftrace_call(r3, r4, r5, r6) */
> .globl ftrace_call
> @@ -189,6 +194,10 @@ ftrace_call:
>
> ld r3, _NIP(r1)
> mtctr r3

Another blank line here.

> +#ifdef CONFIG_LIVEPATCH_64
> + cmpd r14, r3 /* has NIP been altered? */
> + REST_GPR(14, r1)
> +#endif
>
> /* Restore gprs */
> REST_GPRS(3, 10, r1)
> @@ -196,13 +205,17 @@ ftrace_call:
> /* Restore callee's TOC */
> ld r2, 24(r1)
>
> + /* Restore possibly modified LR */
> + ld r0, _LINK(r1)
> + mtlr r0
> +
> /* Pop our stack frame */
> addi r1, r1, SWITCH_FRAME_SIZE
>
> - /* Reload original LR */
> - ld r0, LRSAVE(r1)
> - mtlr r0
> -
> +#ifdef CONFIG_LIVEPATCH_64
> + /* Based on the cmpd above, if the NIP was altered handle livepatch */
> + bne- livepatch_handler
> +#endif

Here too.

> /* Handle function_graph or go back */
> b ftrace_caller_common
>


- Naveen

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