Re: [PATCH 5/5] perf tools: Enhance parsing events tracepoint error output

[Namhyung Kim <namhyung@kernel.org>]

On Mon, Sep 07, 2015 at 10:38:07AM +0200, Jiri Olsa wrote:
> Enhancing parsing events tracepoint error output. Adding
> more verbose output when the tracepoint is not found or
> the tracing event path cannot be access.
> 
>   $ sudo perf record -e sched:sched_krava ls
>   event syntax error: 'sched:sched_krava'
>                        \___ unknown tracepoint
> 
>   Error:  File /sys/kernel/debug/tracing//tracing/events/sched/sched_krava not found.
>   Hint:   Perhaps this kernel misses some CONFIG_ setting to enable this feature?.
> 
>   Run 'perf list' for a list of valid events
>   ...
> 
>   $ perf record -e sched:sched_krava ls
>   event syntax error: 'sched:sched_krava'
>                        \___ can't access trace events
> 
>   Error:  No permissions to read /sys/kernel/debug/tracing//tracing/events/sched/sched_krava
>   Hint:   Try 'sudo mount -o remount,mode=755 /sys/kernel/debug'

What about tracefs?  On my system, tracefs is mounted on
/sys/kernel/debug/tracing thus I cannot access trace events after
remounting debugfs with mode=755.

Also, IIRC tracepoint events adds PERF_SAMPLE_RAW bit automatically,
and it requires perf_event_paranoid being -1 for non-root user, right?

Thanks,
Namhyung