From: Alexei Starovoitov <ast@plumgrid.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: "David S. Miller" <davem@davemloft.net>,
Ingo Molnar <mingo@kernel.org>, Wang Nan <wangnan0@huawei.com>,
He Kuang <hekuang@huawei.com>, Kaixu Xia <xiakaixu@huawei.com>,
Daniel Borkmann <daniel@iogearbox.net>,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 net-next] bpf: fix bpf_perf_event_read() helper
Date: Thu, 22 Oct 2015 08:53:00 -0700 [thread overview]
Message-ID: <5629065C.6020103@plumgrid.com> (raw)
In-Reply-To: <20151022135745.GM3604@twins.programming.kicks-ass.net>
On 10/22/15 6:57 AM, Peter Zijlstra wrote:
> On Wed, Oct 21, 2015 at 03:58:03PM -0700, Alexei Starovoitov wrote:
>> diff --git a/kernel/events/core.c b/kernel/events/core.c
>> index 64754bfecd70..0b6333265872 100644
>> --- a/kernel/events/core.c
>> +++ b/kernel/events/core.c
>> @@ -3258,7 +3258,7 @@ static inline u64 perf_event_count(struct perf_event *event)
>> u64 perf_event_read_local(struct perf_event *event)
>> {
>> unsigned long flags;
>> - u64 val;
>> + u64 val = -EINVAL;
>
> No, you cannot do this, -EINVAL is a valid count value. You simply must
> not call this function on !local events, ever.
agree. Will keep perf_event_read_local() as-is and do all safety
checks on bpf side.
prev parent reply other threads:[~2015-10-22 15:53 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-21 22:58 [PATCH v2 net-next] bpf: fix bpf_perf_event_read() helper Alexei Starovoitov
2015-10-22 4:49 ` Wangnan (F)
2015-10-22 5:00 ` Alexei Starovoitov
2015-10-22 5:30 ` Wangnan (F)
2015-10-22 5:31 ` Wangnan (F)
2015-10-22 6:21 ` Alexei Starovoitov
2015-10-22 7:39 ` Wangnan (F)
2015-10-22 15:51 ` Alexei Starovoitov
2015-10-22 12:30 ` Wangnan (F)
2015-10-22 12:41 ` Peter Zijlstra
2015-10-22 13:57 ` Peter Zijlstra
2015-10-22 15:53 ` Alexei Starovoitov [this message]
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