linux-kernel - Re: [FIX bpf,perf] bpf,perf: return EOPNOTSUPP for bpf handler on PERF_COUNT_SW

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Date:   Mon, 16 Nov 2020 13:02:09 -0800
From:   Martin KaFai Lau <kafai@...com>
To:     Florian Lehner <dev@...-flo.net>
CC:     <bpf@...r.kernel.org>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <ast@...nel.org>,
        <daniel@...earbox.net>, <andrii@...nel.org>,
        <john.fastabend@...il.com>, <peterz@...radead.org>,
        <mingo@...hat.com>, <acme@...nel.org>
Subject: Re: [FIX bpf,perf] bpf,perf: return EOPNOTSUPP for bpf handler on
 PERF_COUNT_SW_DUMMY

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@...-flo.net>
It is missing a Fixes tag.