Hi Tom,
On Fri, 9 Oct 2020 10:17:07 -0500
Tom Zanussi <zanu...@kernel.org> wrote:
> For synthetic event dynamic fields, the type contains "__data_loc",
> which is basically an internal part of the type which is only meant to
> be displayed in the format, not in the event description itself, which
> is confusing to users since they can't use __data_loc on the
> command-line to define an event field, which printing it would lead
> them to believe.
>
> So filter it out from the description, while leaving it in the type.
>
OK, I confirmed this removes __data_loc from synth_events interface.
However, I also found another issue.
/sys/kernel/debug/tracing # echo "myevent char str[]; int v" >>
synthetic_events
/sys/kernel/debug/tracing # cat synthetic_events
myevent char[]; str; int v
It seems that the type "char[]" includes ";" as a type, this results
/sys/kernel/debug/tracing # cat events/synthetic/myevent/format
name: myevent
ID: 1220
format:
field:unsigned short common_type; offset:0; size:2;
signed:0;
field:unsigned char common_flags; offset:2; size:1;
signed:0;
field:unsigned char common_preempt_count; offset:3; size:1;
signed:0;
field:int common_pid; offset:4; size:4; signed:1;
field:__data_loc char[]; str; offset:8; size:8; signed:1;
field:int v; offset:16; size:4; signed:1;
print fmt: "str=%.*s, v=%d", __get_str(str), REC->v
As you can see, the field type has ";" in format file too. This will prevent
parsing event information correctly.
I also try to remove ";" as below, it seems to work correctly.
/sys/kernel/debug/tracing # echo "myevent char[] str; int v" >>
synthetic_events
/sys/kernel/debug/tracing # cat events/synthetic/myevent/format
name: myevent
ID: 1221
format:
field:unsigned short common_type; offset:0; size:2;
signed:0;
field:unsigned char common_flags; offset:2; size:1;
signed:0;
field:unsigned char common_preempt_count; offset:3; size:1;
signed:0;
field:int common_pid; offset:4; size:4; signed:1;
field:__data_loc char[] str; offset:8; size:8; signed:1;
field:int v; offset:16; size:4; signed:1;
print fmt: "str=%.*s, v=%d", __get_str(str), REC->v
Thank you,
> Reported-by: Masami Hiramatsu <mhira...@kernel.org>
> Signed-off-by: Tom Zanussi <zanu...@kernel.org>
> ---
> kernel/trace/trace_events_synth.c | 10 +++++++++-
> 1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/trace/trace_events_synth.c
> b/kernel/trace/trace_events_synth.c
> index 3b2dcc42b8ee..b19e2f4159ab 100644
> --- a/kernel/trace/trace_events_synth.c
> +++ b/kernel/trace/trace_events_synth.c
> @@ -1867,14 +1867,22 @@ static int __synth_event_show(struct seq_file *m,
> struct synth_event *event)
> {
> struct synth_field *field;
> unsigned int i;
> + char *type, *t;
>
> seq_printf(m, "%s\t", event->name);
>
> for (i = 0; i < event->n_fields; i++) {
> field = event->fields[i];
>
> + type = field->type;
> + t = strstr(type, "__data_loc");
> + if (t) { /* __data_loc belongs in format but not event desc */
> + t += sizeof("__data_loc");
> + type = t;
> + }
> +
> /* parameter values */
> - seq_printf(m, "%s %s%s", field->type, field->name,
> + seq_printf(m, "%s %s%s", type, field->name,
> i == event->n_fields - 1 ? "" : "; ");
> }
>
> --
> 2.17.1
>
--
Masami Hiramatsu <mhira...@kernel.org>
