netdev - Re: [PATCH 0/2] bpf: context casting for tail call and gtrace prog type

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Message-ID: <20190226061823.f7hfs7yojfuycqmg@ast-mbp.dhcp.thefacebook.com>
Date:   Mon, 25 Feb 2019 22:18:25 -0800
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Kris Van Hees <kris.van.hees@...cle.com>
Cc:     netdev@...r.kernel.org, bpf@...r.kernel.org, daniel@...earbox.net
Subject: Re: [PATCH 0/2] bpf: context casting for tail call and gtrace prog
 type

On Mon, Feb 25, 2019 at 07:54:13AM -0800, Kris Van Hees wrote:
> 
> The goal is to further extend the BPF_PROG_TYPE_GTRACE implementation to
> support what tracers commonly need, and I am also looking at ways to further
> extend this model to allow more tracer-specific features as well without the
> need for adding a BPF program types for every tracer.

It seems by themselves the patches don't provide any new functionality,
but instead look like plumbing to call external code.
This is no-go.
There were several attempts to do so in the past, so we documented it here:
Documentation/bpf/bpf_design_QA.rst
Q: New functionality via kernel modules?
----------------------------------------
Q: Can BPF functionality such as new program or map types, new
helpers, etc be added out of kernel module code?

A: NO.

The answer is still the same.