From: Peter Zijlstra <peterz@infradead.org>
To: Martin KaFai Lau <kafai@fb.com>
Cc: Florian Lehner <dev@der-flo.net>,
bpf@vger.kernel.org, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org, ast@kernel.org,
daniel@iogearbox.net, andrii@kernel.org,
john.fastabend@gmail.com, mingo@redhat.com, acme@kernel.org
Subject: Re: [FIX bpf,perf] bpf,perf: return EOPNOTSUPP for bpf handler on PERF_COUNT_SW_DUMMY
Date: Tue, 17 Nov 2020 08:53:34 +0100 [thread overview]
Message-ID: <20201117075334.GJ3121392@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20201116210209.skeolnndx3gk2xav@kafai-mbp.dhcp.thefacebook.com>
On Mon, Nov 16, 2020 at 01:02:09PM -0800, Martin KaFai Lau wrote:
> On Mon, Nov 16, 2020 at 07:37:52PM +0100, Florian Lehner wrote:
> > bpf handlers for perf events other than tracepoints, kprobes or uprobes
> > are attached to the overflow_handler of the perf event.
> >
> > Perf events of type software/dummy are placeholder events. So when
> > attaching a bpf handle to an overflow_handler of such an event, the bpf
> > handler will not be triggered.
> >
> > This fix returns the error EOPNOTSUPP to indicate that attaching a bpf
> > handler to a perf event of type software/dummy is not supported.
> >
> > Signed-off-by: Florian Lehner <dev@der-flo.net>
> It is missing a Fixes tag.
I don't think it actually fixes anything. worse it could break things.
Atatching a bpf filter to a dummy event is pointless, but harmless. We
allow it now, disallowing it will break whatever programs out there are
doing harmless silly things.
I really don't see the point of this patch. It grows the kernel code for
absolutely no distinguishable benefit.
next prev parent reply other threads:[~2020-11-17 7:54 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-16 18:37 [FIX bpf,perf] bpf,perf: return EOPNOTSUPP for bpf handler on PERF_COUNT_SW_DUMMY Florian Lehner
2020-11-16 21:02 ` Martin KaFai Lau
2020-11-17 7:53 ` Peter Zijlstra [this message]
2020-11-17 15:39 ` Florian Lehner
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