On Fri, 19 Aug 2022 21:40:38 -0400
Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:
> From: "Steven Rostedt (Google)" <rostedt@xxxxxxxxxxx>
>
> 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@xxxxxxxxxx>
Thank you!
>
> Cc: stable@xxxxxxxxxxxxxxx
> Fixes: 7491e2c44278 ("tracing: Add a probe that attaches to trace events")
> Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
> ---
> 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
--
Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
