Re: [RFC PATCH v2 2/6] tracing: Expose ftrace_regs regardless of CONFIG_FUNCTION_TRACER

[Florent Revest]

On Mon, Aug 7, 2023 at 8:48 AM Masami Hiramatsu (Google)
<mhiramat@xxxxxxxxxx> wrote:
> diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
> index ce156c7704ee..3fb94a1a2461 100644
> --- a/include/linux/ftrace.h
> +++ b/include/linux/ftrace.h
> @@ -112,11 +112,11 @@ static inline int ftrace_mod_get_kallsym(unsigned int symnum, unsigned long *val
>  }
>  #endif
>
> -#ifdef CONFIG_FUNCTION_TRACER
> -
> -extern int ftrace_enabled;
> -
> -#ifndef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS
> +/*
> + * If the architecture doesn't support FTRACE_WITH_ARGS or disable function

nit: disables*

> + * tracer, define the default(pt_regs compatible) ftrace_regs.
> + */
> +#if !defined(CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS) || !defined(CONFIG_FUNCTION_TRACER)

I wonder if we should make things simpler with:

#if defined(HAVE_PT_REGS_COMPAT_FTRACE_REGS) || !defined(CONFIG_FUNCTION_TRACER)

And remove the ftrace_regs definitions that are copy-pastes of this
block in arch specific headers. Then we can enforce in a single point
that HAVE_PT_REGS_COMPAT_FTRACE_REGS holds.

Maybe that's a question for Steven ?