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

[Masami Hiramatsu (Google) <mhiramat@kernel.org>]

On Mon, 09 Sep 2024 10:16:55 +0200
Sven Schnelle <svens@linux.ibm.com> wrote:

> Masami Hiramatsu (Google) <mhiramat@kernel.org> writes:
> 
> > On Fri, 6 Sep 2024 11:36:11 +0800
> > Zheng Yejian <zhengyejian@huaweicloud.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@linux.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"
> 
> Now i'm confused - Zheng wrote that DEBUG_INFO_BTF depends on
> BPF_SYSCALL. I just verified that. So i could just remove BPF_SYSCALL
> from the dependencies - but your example also has BPF_SYSCALL listed.

Ah, sorry for confusion. In this case, just need DEBUG_INFO_BTF.
Hmm, I think I also need to remove BPF_SYSCALL.

Thanks,

> 
> Regards
> Sven


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