Re: [PATCH 1/3] tracing/kprobe: Add PERF_EVENT_IOC_QUERY_KPROBE ioctl

[Song Liu <liu.song.a23@gmail.com>]

On Tue, Aug 6, 2019 at 4:41 PM Daniel Xu <dxu@dxuuu.xyz> wrote:
>
> It's useful to know kprobe's nmissed and nhit stats. For example with
> tracing tools, it's important to know when events may have been lost.
> There is currently no way to get that information from the perf API.
> This patch adds a new ioctl that lets users query this information.
> ---

[...]
> +
>  /*
>   * Ioctls that can be done on a perf event fd:
>   */
> @@ -462,6 +484,7 @@ struct perf_event_query_bpf {
>  #define PERF_EVENT_IOC_PAUSE_OUTPUT            _IOW('$', 9, __u32)
>  #define PERF_EVENT_IOC_QUERY_BPF               _IOWR('$', 10, struct perf_event_query_bpf *)
>  #define PERF_EVENT_IOC_MODIFY_ATTRIBUTES       _IOW('$', 11, struct perf_event_attr *)
> +#define PERF_EVENT_IOC_QUERY_KPROBE            _IOWR('$', 12, struct perf_event_query_kprobe *)

This should be _IOR().

[...]
> diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> index 9d483ad9bb6c..5449182f3056 100644
> --- a/kernel/trace/trace_kprobe.c
> +++ b/kernel/trace/trace_kprobe.c
> @@ -196,6 +196,31 @@ bool trace_kprobe_error_injectable(struct trace_event_call *call)
>         return within_error_injection_list(trace_kprobe_address(tk));
>  }
>
> +int perf_event_query_kprobe(struct perf_event *event, void __user *info)

I think perf_kprobe_event_query() would be a better name, especially that we
have struct perf_event_query_kprobe.

Thanks,
Song