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

[Alexei Starovoitov]

On Fri, Jul 4, 2014 at 8:17 AM, Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote:
> On Wed, Jul 2, 2014 at 7:29 PM, Alexei Starovoitov <ast@xxxxxxxxxxxx> wrote:
>>
>> non-root API:
>>
>> ufd = bpf_create_map(local_map_id,â )
>> bpf_map_update/delete/lookup_elem(ufd,â)
>> ufd = bpf_prog_load(insns)
>> close(ufd)
>>
>> root only API:
>>
>> global_id = bpf_get_id(ufd) // returns either map or prog global id
>> bpf_map_delete(global_map_id)
>> bpf_prog_unload(global_prog_id)
>>
>> Details:
>>
>> ufd = bpf_create_map(local_map_id, ...);
>>
>> local_map_id - process local map_id
>> (this id is used to access maps from eBPF program loaded by this process)
>>
>> ufd - process local file descriptor
>> (used to update/lookup maps from this process)
>>
>> global_map_id = bpf_get_id(ufd)
>> this is root only call to get global_ids and pass them to global events
>> like tracing.
>>
>> global ids will only be seen by root. There is no way for root or non-root
>> to influence id ranges.
>>
>> I think it will be cleaner once I finish fd conversion as a patch.
>
> OK
>
> FWIW, per-process local id maps sound almost equivalent to relocations
> -- the latter could be as simple as an extra nlattr giving a list of
> pairs of (per-eBPF-program id, fd).

I thought about array of such pairs as well, but it felt cleaner to remember
the (per-eBPF-program id, fd) pair in a kernel, instead of asking user
space to keep track of them. Either way I think it's minor. I'll implement
both and see which way is cleaner.

So far I did 3-way enum split in verifier and addressed Namhyung's
and Chema's comments. Updated in the same place:
git://git.kernel.org/pub/scm/linux/kernel/git/ast/bpf master

I'll be traveling next week.
Once I'm done with fd-style interface, I'll post a v2.

Thanks
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