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

On Fri, 6 Sep 2024 11:36:11 +0800
Zheng Yejian [off-list ref] wrote:

On 2024/9/4 14:58, Sven Schnelle wrote:

quoted

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"

Thank you,

quoted

+	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) [off-list ref]