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SubjectRe: [PATCH v2 11/13] powerpc/ftrace: directly call of function graph tracer by ftrace caller
Christophe Leroy wrote:
> Modify function graph tracer to be handled directly by the standard
> ftrace caller.
>
> This is made possible as powerpc now supports
> CONFIG_DYNAMIC_FTRACE_WITH_ARGS.
>
> This change simplifies the call of function graph ftrace.
>
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
> arch/powerpc/include/asm/ftrace.h | 6 ++
> arch/powerpc/kernel/trace/ftrace.c | 11 ++++
> arch/powerpc/kernel/trace/ftrace_32.S | 53 +--------------
> .../powerpc/kernel/trace/ftrace_64_mprofile.S | 64 +------------------
> 4 files changed, 20 insertions(+), 114 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/ftrace.h b/arch/powerpc/include/asm/ftrace.h
> index 45c3d6f11daa..70b457097098 100644
> --- a/arch/powerpc/include/asm/ftrace.h
> +++ b/arch/powerpc/include/asm/ftrace.h
> @@ -38,6 +38,12 @@ static __always_inline void ftrace_instruction_pointer_set(struct ftrace_regs *f
> {
> regs_set_return_ip(&fregs->regs, ip);
> }
> +
> +struct ftrace_ops;
> +
> +#define ftrace_graph_func ftrace_graph_func
> +void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
> + struct ftrace_ops *op, struct ftrace_regs *fregs);
> #endif
> #endif /* __ASSEMBLY__ */
>
> diff --git a/arch/powerpc/kernel/trace/ftrace.c b/arch/powerpc/kernel/trace/ftrace.c
> index ce673764cb69..74a176e394ef 100644
> --- a/arch/powerpc/kernel/trace/ftrace.c
> +++ b/arch/powerpc/kernel/trace/ftrace.c
> @@ -917,6 +917,9 @@ static int ftrace_modify_ftrace_graph_caller(bool enable)
> unsigned long stub = (unsigned long)(&ftrace_graph_stub);
> ppc_inst_t old, new;
>
> + if (IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_ARGS))
> + return 0;
> +
> old = ftrace_call_replace(ip, enable ? stub : addr, 0);
> new = ftrace_call_replace(ip, enable ? addr : stub, 0);
>
> @@ -955,6 +958,14 @@ unsigned long prepare_ftrace_return(unsigned long parent, unsigned long ip,
> out:
> return parent;
> }

For x86, commit 0c0593b45c9b4e ("x86/ftrace: Make function graph use
ftrace directly") also adds recursion check before the call to
function_graph_enter() in prepare_ftrace_return(). Do we need that on
powerpc as well?


- Naveen

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