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

On Wed, Dec 12, 2018 at 06:56:11PM +0000, Song Liu wrote:

quoted

On Dec 12, 2018, at 10:05 AM, Peter Zijlstra [off-list ref] wrote:

On Wed, Dec 12, 2018 at 05:09:17PM +0000, Song Liu wrote:

quoted

quoted

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?

Well, it is a question of ABI. I don't like mixing the kallsym updates
with the BPF updates.