linux-kernel - Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY maps trace data output when perf sampling

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Message-ID: <20151021134951.GH3604@twins.programming.kicks-ass.net>
Date:	Wed, 21 Oct 2015 15:49:51 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	"Wangnan (F)" <wangnan0@...wei.com>
Cc:	Alexei Starovoitov <ast@...mgrid.com>,
	xiakaixu <xiakaixu@...wei.com>, davem@...emloft.net,
	acme@...nel.org, mingo@...hat.com, masami.hiramatsu.pt@...achi.com,
	jolsa@...nel.org, daniel@...earbox.net,
	linux-kernel@...r.kernel.org, pi3orama@....com, hekuang@...wei.com,
	netdev@...r.kernel.org
Subject: Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY
 maps trace data output when perf sampling

On Wed, Oct 21, 2015 at 09:42:12PM +0800, Wangnan (F) wrote:
> How can an eBPF program access a !local event:
> 
> when creating perf event array we don't care which perf event
> is for which CPU, so perf program can access any perf event in
> that array.

So what is stopping the eBPF thing from calling perf_event_read_local()
on a !local event and triggering a kernel splat?

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