linux-kernel - Re: [PATCH v19 12/19] fprobe: Rewrite fprobe on function-graph tracer

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Message-Id: <20241206080952.512c59cc5ddbf45ef145b5ce@kernel.org>
Date: Fri, 6 Dec 2024 08:09:52 +0900
From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: Alexei Starovoitov <alexei.starovoitov@...il.com>, Florent Revest
 <revest@...omium.org>, linux-trace-kernel@...r.kernel.org, LKML
 <linux-kernel@...r.kernel.org>, Martin KaFai Lau <martin.lau@...ux.dev>,
 bpf <bpf@...r.kernel.org>, Alexei Starovoitov <ast@...nel.org>, Jiri Olsa
 <jolsa@...nel.org>, Alan Maguire <alan.maguire@...cle.com>, Mark Rutland
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 <mathieu.desnoyers@...icios.com>, Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v19 12/19] fprobe: Rewrite fprobe on function-graph
 tracer

On Thu, 5 Dec 2024 13:34:24 -0500
Steven Rostedt <rostedt@...dmis.org> wrote:

> On Mon, 11 Nov 2024 00:51:09 +0900
> "Masami Hiramatsu (Google)" <mhiramat@...nel.org> wrote:
> 
> > diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
> > index 2fc55a1a88aa..91a6382c04bd 100644
> > --- a/kernel/trace/Kconfig
> > +++ b/kernel/trace/Kconfig
> > @@ -307,12 +307,10 @@ config DYNAMIC_FTRACE_WITH_ARGS
> >  
> >  config FPROBE
> >  	bool "Kernel Function Probe (fprobe)"
> > -	depends on FUNCTION_TRACER
> > -	depends on DYNAMIC_FTRACE_WITH_REGS || DYNAMIC_FTRACE_WITH_ARGS
> > -	depends on HAVE_FTRACE_REGS_HAVING_PT_REGS || !HAVE_DYNAMIC_FTRACE_WITH_ARGS
> > -	depends on HAVE_RETHOOK
> > -	select RETHOOK
> > -	default n
> > +	depends on HAVE_FUNCTION_GRAPH_FREGS && HAVE_FTRACE_GRAPH_FUNC
> > +	depends on DYNAMIC_FTRACE_WITH_ARGS
> > +	select FUNCTION_GRAPH_TRACER
> > +	default y
> 
> Please remove the "default y". This will select function graph tracer and
> will not let you to disable it without disabling this.

Good catch! I forgot about the combination's side effect.

> 
> If you really want to tick off Linus, then make an option that selects other
> options "default y" ;-)

Oh, no, I don't want it.

> 
> Can you rebase the series off of v6.13-rc1? There's a minor conflict with
> the riscv Kconfig.

OK, let me update.

Thank you!

> 
> -- Steve
> 
> 
> >  	help
> >  	  This option enables kernel function probe (fprobe) based on ftrace.
> >  	  The fprobe is similar to kprobes, but probes only for kernel function

-- 
Masami Hiramatsu (Google) <mhiramat@...nel.org>