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

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Message-ID: <55B19B7A.4030400@huawei.com>
Date:	Fri, 24 Jul 2015 09:57:14 +0800
From:	xiakaixu <xiakaixu@...wei.com>
To:	Alexei Starovoitov <ast@...mgrid.com>
CC:	<davem@...emloft.net>, <acme@...nel.org>, <mingo@...hat.com>,
	<a.p.zijlstra@...llo.nl>, <masami.hiramatsu.pt@...achi.com>,
	<jolsa@...nel.org>, <wangnan0@...wei.com>,
	<linux-kernel@...r.kernel.org>, <pi3orama@....com>,
	<hekuang@...wei.com>
Subject: Re: [PATCH v3 2/3] bpf: Implement function bpf_perf_event_read()
 that get the selected hardware PMU conuter

于 2015/7/24 6:56, Alexei Starovoitov 写道:
> 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@...wei.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?

Yeah, the errno is better.

Thanks!
> 
> 
> .
> 


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