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From:   Florent Revest <revest@chromium.org>
Date:   Wed, 9 Aug 2023 12:29:13 +0200
Message-ID: <CABRcYmJpA7tWk7pNxMy-44aoT9fFByQY3kGiEfKDbOe9WPkmNg@mail.gmail.com>
Subject: Re: [RFC PATCH v2 2/6] tracing: Expose ftrace_regs regardless of CONFIG_FUNCTION_TRACER
To:     "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc:     Alexei Starovoitov <alexei.starovoitov@gmail.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        linux-trace-kernel@vger.kernel.org,
        LKML <linux-kernel@vger.kernel.org>,
        Martin KaFai Lau <martin.lau@linux.dev>,
        bpf <bpf@vger.kernel.org>, Sven Schnelle <svens@linux.ibm.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Jiri Olsa <jolsa@kernel.org>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Alan Maguire <alan.maguire@oracle.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>
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On Mon, Aug 7, 2023 at 8:48=E2=80=AFAM Masami Hiramatsu (Google)
<mhiramat@kernel.org> 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 i=
nt 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 funct=
ion

nit: disables*

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

I wonder if we should make things simpler with:

#if defined(HAVE_PT_REGS_COMPAT_FTRACE_REGS) || !defined(CONFIG_FUNCTION_TR=
ACER)

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 ?