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

Alexei Starovoitov
2015-07-23T22:57:02Z

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?