From mboxrd@z Thu Jan  1 00:00:00 1970
From: Alexei Starovoitov <ast@fb.com>
Subject: Re: [PATCH bpf-next 1/3] perf/core: introduce
 perf_event_mmap_bpf_prog
Date: Thu, 20 Sep 2018 00:53:02 +0000
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Cc: "David S . Miller" <davem@davemloft.net>,
        "daniel@iogearbox.net" <daniel@iogearbox.net>,
        "peterz@infradead.org" <peterz@infradead.org>,
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To: Song Liu <songliubraving@fb.com>,
        Alexei Starovoitov <ast@kernel.org>
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On 9/19/18 4:30 PM, Song Liu wrote:
>
>
>> On Sep 19, 2018, at 3:39 PM, Alexei Starovoitov <ast@kernel.org> wrote:
>>
>> introduce perf_event_mmap_bpf_prog() helper to emit RECORD_MMAP events
>> into perf ring buffer.
>> It's used by bpf load/unload logic to notify user space of addresses
>> and names of JITed bpf programs.
>>
>> Note that event->mmap.pid =3D=3D -1 is an existing indicator of kernel e=
vent.
>> In addition use event->mmap.tid =3D=3D BPF_FS_MAGIC to indicate bpf rela=
ted
>> RECORD_MMAP event.
>>
>> Alternatively it's possible to introduce new 'enum perf_event_type' comm=
and
>> specificially for bpf prog load/unload, but existing RECORD_MMAP
>> is very close, so the choice made by this patch is to extend it.
>>
>> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
>
> Acked-by: Song Liu <songliubraving@fb.com>
>
> I guess we should also use this for kernel modules load/unload?

yes. that's possible.
There is similar issue with modules today that get unloaded
before 'perf report'.
Synthetic record_mmap for modules that perf emits into perf.data
has filename=3D=3Dmodule_name. It solves typical use case though.
We can extend record_mmap further and let kernel emit them
for module load/unload.
Some new magic for 'tid' would be necessary.