RE: [PATCH RFC net-next 07/14] bpf: expand BPF syscall with program load/unload

From: Alexei Starovoitov

On Fri, Jun 27, 2014 at 5:19 PM, Andy Lutomirski [off-list ref] wrote:

quoted

On Fri, Jun 27, 2014 at 5:05 PM, Alexei Starovoitov [off-list ref] wrote:

quoted

eBPF programs are safe run-to-completion functions with load/unload
methods from userspace similar to kernel modules.

User space API:

- load eBPF program
  prog_id = bpf_prog_load(int prog_id, bpf_prog_type, struct nlattr *prog, int len)

  where 'prog' is a sequence of sections (currently TEXT and LICENSE)
  TEXT - array of eBPF instructions
  LICENSE - GPL compatible
+
+       err = -EINVAL;
+       /* look for mandatory license string */
+       if (!tb[BPF_PROG_LICENSE])
+               goto free_attr;
+
+       /* eBPF programs must be GPL compatible */
+       if (!license_is_gpl_compatible(nla_data(tb[BPF_PROG_LICENSE])))
+               goto free_attr;

Seriously?  My mind boggles.

Yes. Quite a bit of logic can fit into one eBPF program. I don't think it's wise
to leave this door open for abuse. This check makes it clear that if you
write a program in C, the source code must be available.

That seems utterly extreme.
Loadable kernel modules don't have to be GPL.

I can imagine that some people might not want to load code for which
they don't have the source - but in that case they probably want to
compile it themselves anyway.

I don't want to have to put a gpl licence on random pieces of test
code I might happen to write for my own use.

	David