Commit f04dec93 authored by Steven Rostedt (Google)'s avatar Steven Rostedt (Google)
Browse files

tracing/eprobes: Fix reading of string fields 

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

Link: https://lkml.kernel.org/r/20220820134400.959640191@goodmis.org



Cc: stable@vger.kernel.org
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Tzvetomir Stoyanov <tz.stoyanov@gmail.com>
Cc: Tom Zanussi <zanussi@kernel.org>
Fixes: 7491e2c4 ("tracing: Add a probe that attaches to trace events")
Acked-by: default avatarMasami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent 02333de9

kernel/trace/trace_eprobe.c

+21 −0
Original line number Diff line number Diff line
@@ -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)