Re: [PATCH v3 2/3] bpf: Implement function bpf_perf_event_read() that get the selected hardware PMU conuter

[Alexei Starovoitov <ast@plumgrid.com>]

On 7/23/15 2:42 AM, Kaixu Xia wrote:
> According to the perf_event_map_fd and index, the function
> bpf_perf_event_read() can convert the corresponding map
> value to the pointer to struct perf_event and return the
> Hardware PMU counter value.
>
> Signed-off-by: Kaixu Xia <xiakaixu@huawei.com>
...
> +static u64 bpf_perf_event_read(u64 r1, u64 index, u64 r3, u64 r4, u64 r5)
> +{
> +	struct bpf_map *map = (struct bpf_map *) (unsigned long) r1;
> +	struct bpf_array *array = container_of(map, struct bpf_array, map);
> +	struct perf_event *event;
> +
> +	if (index >= array->map.max_entries)
> +		return -E2BIG;
> +
> +	event = array->events[index];
> +	if (!event)
> +		return -EBADF;

probably ENOENT makes more sense here.

> +
> +	if (event->state != PERF_EVENT_STATE_ACTIVE)
> +		return -ENOENT;

and -EINVAL here?