linux-kernel - Re: [PATCH 5/7] tracing: add config option for print arguments in ftrace

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Message-Id: <20240908223048.8bd6961dbc741d971f57b5c2@kernel.org>
Date: Sun, 8 Sep 2024 22:30:48 +0900
From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
To: Zheng Yejian <zhengyejian@...weicloud.com>
Cc: Sven Schnelle <svens@...ux.ibm.com>, Steven Rostedt
 <rostedt@...dmis.org>, Mark Rutland <mark.rutland@....com>, Mathieu
 Desnoyers <mathieu.desnoyers@...icios.com>, linux-kernel@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH 5/7] tracing: add config option for print arguments in
 ftrace

On Fri, 6 Sep 2024 11:36:11 +0800
Zheng Yejian <zhengyejian@...weicloud.com> wrote:

> On 2024/9/4 14:58, Sven Schnelle wrote:
> > Add a config option to disable/enable function argument
> > printing support during runtime.
> > 
> > Signed-off-by: Sven Schnelle <svens@...ux.ibm.com>
> > ---
> >   kernel/trace/Kconfig | 12 ++++++++++++
> >   1 file changed, 12 insertions(+)
> > 
> > diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
> > index 721c3b221048..8b9b6cdf39ac 100644
> > --- a/kernel/trace/Kconfig
> > +++ b/kernel/trace/Kconfig
> > @@ -242,6 +242,18 @@ config FUNCTION_GRAPH_RETVAL
> >   	  enable it via the trace option funcgraph-retval.
> >   	  See Documentation/trace/ftrace.rst
> >   
> > +config FUNCTION_TRACE_ARGS
> > +	bool "Kernel Function Tracer Arguments"
> > +	depends on HAVE_FUNCTION_ARG_ACCESS_API
> > +	depends on DEBUG_INFO_BTF && BPF_SYSCALL
> 
> Nice feature!
> 
> Just a nit, DEBUG_INFO_BTF currently depends on BPF_SYSCALL,
> so BPF_SYSCALL may not be necessary here. This feature
> also doesn't seem to depend on bpf.

Indeed. Sven, you can check the PROBE_EVENTS_BTF_ARGS as
an example.

config PROBE_EVENTS_BTF_ARGS
        depends on HAVE_FUNCTION_ARG_ACCESS_API
        depends on FPROBE_EVENTS || KPROBE_EVENTS
        depends on DEBUG_INFO_BTF && BPF_SYSCALL
        bool "Support BTF function arguments for probe events"

Thank you,

> 
> > +	default n
> > +	help
> > +	  Support recording and printing of function arguments when using
> > +	  the function tracer or function graph tracer. This feature is off
> > +	  by default, and can be enabled via the trace option func-args (for
> > +	  the function tracer) and funcgraph-args (for the function graph
> > +	  tracer).
> > +
> >   config DYNAMIC_FTRACE
> >   	bool "enable/disable function tracing dynamically"
> >   	depends on FUNCTION_TRACER
> 
> -- 
> Thanks,
> Zheng Yejian
> 
> 


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