Re: [PATCH RFC net-next 03/14] bpf: introduce syscall(BPF, ...) and BPF maps

On Fri, Jun 27, 2014 at 11:25 PM, Andy Lutomirski [off-list ref] wrote:

On Fri, Jun 27, 2014 at 10:55 PM, Alexei Starovoitov [off-list ref] wrote:

quoted

On Fri, Jun 27, 2014 at 5:16 PM, Andy Lutomirski [off-list ref] wrote:

quoted

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

quoted

BPF syscall is a demux for different BPF releated commands.

'maps' is a generic storage of different types for sharing data between kernel
and userspace.

The maps can be created/deleted from user space via BPF syscall:
- create a map with given id, type and attributes
  map_id = bpf_map_create(int map_id, map_type, struct nlattr *attr, int len)
  returns positive map id or negative error

- delete map with given map id
  err = bpf_map_delete(int map_id)
  returns zero or negative error

What's the scope of "id"?  How is it secured?

the map and program id space is global and it's cap_sys_admin only.
There is no pressing need to do it with per-user limits.
So the whole thing is root only for now.

Hmm.  This may be unpleasant if you ever want to support non-root or
namespaced operation.

I think it will be easy to extend it per namespace when we lift
root-only restriction. It will be seamless without user api changes.

How hard would it be to give these things fds?

you mean programs/maps auto-terminate when creator process
exits? I thought about it and it's appealing at first glance, but
doesn't fit the model of existing tracepoint events which are global.
The programs attached to events need to live without 'daemon'
hanging around. Therefore I picked 'kernel module'- like method.