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

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Date:   Mon, 29 Nov 2021 18:56:53 +0100
From:   Sven Schnelle <svens@...ux.ibm.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Yafang Shao <laoar.shao@...il.com>, akpm@...ux-foundation.org,
        netdev@...r.kernel.org, bpf@...r.kernel.org,
        linux-perf-users@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        oliver.sang@...el.com, lkp@...el.com,
        Andrii Nakryiko <andrii@...nel.org>,
        David Hildenbrand <david@...hat.com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>,
        Andrii Nakryiko <andrii.nakryiko@...il.com>,
        Michal Miroslaw <mirq-linux@...e.qmqm.pl>,
        Peter Zijlstra <peterz@...radead.org>,
        Matthew Wilcox <willy@...radead.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Kees Cook <keescook@...omium.org>,
        Petr Mladek <pmladek@...e.com>,
        Tom Zanussi <zanussi@...nel.org>
Subject: Re: [PATCH v2 7/7] tools/testing/selftests/bpf: replace open-coded
 16 with TASK_COMM_LEN

Steven Rostedt <rostedt@...dmis.org> writes:

> On Mon, 29 Nov 2021 11:13:31 +0100
> Sven Schnelle <svens@...ux.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;
>  	}
>