Re: [PATCH v2 7/7] tools/testing/selftests/bpf: replace open-coded 16 with TASK_COMM_LEN

[Sven Schnelle <svens@linux.ibm.com>]

Steven Rostedt <rostedt@goodmis.org> writes:

> On Mon, 29 Nov 2021 11:13:31 +0100
> Sven Schnelle <svens@linux.ibm.com> wrote:
>
>
>> This breaks the trigger-field-variable-support.tc from the ftrace test
>> suite at least on s390:
>> 
>> echo
>> 'hist:keys=next_comm:wakeup_lat=common_timestamp.usecs-$ts0:onmatch(sched.sched_waking).wakeup_latency($wakeup_lat,next_pid,sched.sched_waking.prio,next_comm)
>> if next_comm=="ping"'
>> linux/tools/testing/selftests/ftrace/test.d/trigger/inter-event/trigger-field-variable-support.tc: line 15: echo: write error: Invalid argument
>> 
>> I added a debugging line into check_synth_field():
>> 
>> [   44.091037] field->size 16, hist_field->size 16, field->is_signed 1, hist_field->is_signed 0
>> 
>> Note the difference in the signed field.
>
> That should not break on strings.
>
> Does this fix it (if you keep the patch)?

It does. Thanks!

> -- Steve
>
> diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
> index 9555b8e1d1e3..319f9c8ca7e7 100644
> --- a/kernel/trace/trace_events_hist.c
> +++ b/kernel/trace/trace_events_hist.c
> @@ -3757,7 +3757,7 @@ static int check_synth_field(struct synth_event *event,
>  
>  	if (strcmp(field->type, hist_field->type) != 0) {
>  		if (field->size != hist_field->size ||
> -		    field->is_signed != hist_field->is_signed)
> +		    (!field->is_string && field->is_signed != hist_field->is_signed))
>  			return -EINVAL;
>  	}
>