linux-kernel - Re: [PATCH 2/5] ftrace perf: Move exclude_kernel tracepoint check to init event

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Date:	Thu, 10 Mar 2016 09:39:55 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Jiri Olsa <jolsa@...nel.org>
CC:	Steven Rostedt <rostedt@...dmis.org>,
	lkml <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Arnaldo Carvalho de Melo <acme@...nel.org>
Subject: Re: [PATCH 2/5] ftrace perf: Move exclude_kernel tracepoint check to
 init event

On Wed, Mar 09, 2016 at 09:46:42PM +0100, Jiri Olsa wrote:
> We suppress events with attr::exclude_kernel set when
> the event is generated, so following capture will
> give no warning but won't produce any data:
> 
>   $ sudo perf record -e sched:sched_switch:u ls
>   $ sudo /perf script | wc -l
>   0
> 
> Checking the attr::exclude_(kernel|user) at the event
> init time and failing right away for tracepoints from
> uprobes/kprobes and native ones:
> 
>   $ sudo perf record -e sched:sched_switch:u ls
>   Error:
>   The sys_perf_event_open() syscall returned with 22 (Invalid argument) for event (sched:sched_switch).
>   /bin/dmesg may provide additional information.
>   No CONFIG_PERF_EVENTS=y kernel support configured?
> 
>   $ sudo perf record -e probe:sys_read:u ls
>   Error:
>   The sys_perf_event_open() syscall returned with 22 (Invalid argument) for event (probe:sys_read).
>   /bin/dmesg may provide additional information.
>   No CONFIG_PERF_EVENTS=y kernel support configured?
> 
>   $ ./perf record -e probe_ex:main:k ./ex
>   Error:
>   The sys_perf_event_open() syscall returned with 22 (Invalid argument) for event (probe_ex:main).
>   /bin/dmesg may provide additional information.
>   No CONFIG_PERF_EVENTS=y kernel support configured?
> 
> Signed-off-by: Jiri Olsa <jolsa@...nel.org>

Acked-by: Namhyung Kim <namhyung@...nel.org>

Maybe we need to improve the error message later.

Thanks,
Namhyung


> ---
>  kernel/events/core.c            |  5 -----
>  kernel/trace/trace_event_perf.c | 25 +++++++++++++++++++++++++
>  2 files changed, 25 insertions(+), 5 deletions(-)
> 
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index c15fd097af93..ca68fdcf47ce 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -6898,11 +6898,6 @@ static int perf_tp_event_match(struct perf_event *event,
>  {
>  	if (event->hw.state & PERF_HES_STOPPED)
>  		return 0;
> -	/*
> -	 * All tracepoints are from kernel-space.
> -	 */
> -	if (event->attr.exclude_kernel)
> -		return 0;
>  
>  	if (!perf_tp_filter_match(event, data))
>  		return 0;
> diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c
> index a7171ec2c1ca..0a3779bd18a1 100644
> --- a/kernel/trace/trace_event_perf.c
> +++ b/kernel/trace/trace_event_perf.c
> @@ -182,11 +182,36 @@ static void perf_trace_event_close(struct perf_event *p_event)
>  	tp_event->class->reg(tp_event, TRACE_REG_PERF_CLOSE, p_event);
>  }
>  
> +static int perf_trace_event_attr(struct trace_event_call *tp_event,
> +				 struct perf_event *event)
> +{
> +	/*
> +	 * All tracepoints and kprobes are from kernel-space.
> +	 */
> +	if (((tp_event->flags & TRACE_EVENT_FL_TRACEPOINT) ||
> +	     (tp_event->flags & TRACE_EVENT_FL_KPROBE)) &&
> +	     event->attr.exclude_kernel)
> +		return -EINVAL;
> +
> +	/*
> +	 * All uprobes are from user-space.
> +	 */
> +	if ((tp_event->flags & TRACE_EVENT_FL_UPROBE) &&
> +	    event->attr.exclude_user)
> +		return -EINVAL;
> +
> +	return 0;
> +}
> +
>  static int perf_trace_event_init(struct trace_event_call *tp_event,
>  				 struct perf_event *p_event)
>  {
>  	int ret;
>  
> +	ret = perf_trace_event_attr(tp_event, p_event);
> +	if (ret)
> +		return ret;
> +
>  	ret = perf_trace_event_perm(tp_event, p_event);
>  	if (ret)
>  		return ret;
> -- 
> 2.4.3
>