Re: [PATCH v3 perf, bpf-next 1/4] perf, bpf: Introduce PERF_RECORD_BPF_EVENT

From: Song Liu
Date: Wed Dec 12 2018 - 13:56:57 EST

> On Dec 12, 2018, at 10:05 AM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> On Wed, Dec 12, 2018 at 05:09:17PM +0000, Song Liu wrote:
>>> And while this tracks the bpf kallsyms, it does not do all kallsyms.
>>> .... Oooh, I see the problem, everybody is doing their own custom
>>> kallsym_{add,del}() thing, instead of having that in generic code :-(
>>> This, for example, doesn't track module load/unload nor ftrace
>>> trampolines, even though both affect kallsyms.
>> I think we can use PERF_RECORD_MMAP(or MMAP2) for module load/unload.
>> That could be separate sets of patches.
> So I would actually like to move bpf_lock/bpf_kallsyms/bpf_tree +
> bpf_prog_kallsyms_*() + __bpf_address_lookup() into kernel/kallsyms.c
> and also have ftrace use that.
> Because currently the ftrace stuff is otherwise invisible.
> A generic kallsym register/unregister for any JIT.

I guess this is _not_ a requirement for this patchset? BPF program has
special data (id, sub_id, tag) that we need PERF_RECORD_BPF_EVENT. So
this patchset should be orthogonal to the generic kallsym framework?