On Fri, 19 Aug 2022 21:40:38 -0400 Steven Rostedt rostedt@goodmis.org wrote:

From: "Steven Rostedt (Google)" rostedt@goodmis.org

Currently when an event probe (eprobe) hooks to a string field, it does not display it as a string, but instead as a number. This makes the field rather useless. Handle the different kinds of strings, dynamic, static, relational/dynamic etc.

Now when a string field is used, the ":string" type can be used to display it:

echo "e:sw sched/sched_switch comm=$next_comm:string" > dynamic_events

Really nice!

Acked-by: Masami Hiramatsu (Google) mhiramat@kernel.org

Thank you!

Cc: stable@vger.kernel.org Fixes: 7491e2c44278 ("tracing: Add a probe that attaches to trace events") Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org

---

kernel/trace/trace_eprobe.c | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+)

diff --git a/kernel/trace/trace_eprobe.c b/kernel/trace/trace_eprobe.c index 550671985fd1..a1d3423ab74f 100644 --- a/kernel/trace/trace_eprobe.c +++ b/kernel/trace/trace_eprobe.c @@ -311,6 +311,27 @@ static unsigned long get_event_field(struct fetch_insn *code, void *rec) addr = rec + field->offset;

• if (is_string_field(field)) {

• switch (field->filter_type) {
  

• case FILTER_DYN_STRING:
  

• 	val = (unsigned long)(rec + (*(unsigned int *)addr & 0xffff));
  

• 	break;
  

• case FILTER_RDYN_STRING:
  

• 	val = (unsigned long)(addr + (*(unsigned int *)addr & 0xffff));
  

• 	break;
  

• case FILTER_STATIC_STRING:
  

• 	val = (unsigned long)addr;
  

• 	break;
  

• case FILTER_PTR_STRING:
  

• 	val = (unsigned long)(*(char *)addr);
  

• 	break;
  

• default:
  

• 	WARN_ON_ONCE(1);
  

• 	return 0;
  

• }
  

• return val;
  

• }
• switch (field->size) { case 1: if (field->is_signed)

-- 2.35.1