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

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Date:	Sat, 5 Jul 2014 14:59:07 -0700
From:	Alexei Starovoitov <ast@...mgrid.com>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Ingo Molnar <mingo@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Daniel Borkmann <dborkman@...hat.com>,
	Chema Gonzalez <chema@...gle.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Jiri Olsa <jolsa@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Kees Cook <keescook@...omium.org>,
	Linux API <linux-api@...r.kernel.org>,
	Network Development <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC net-next 03/14] bpf: introduce syscall(BPF, ...) and
 BPF maps

On Fri, Jul 4, 2014 at 8:17 AM, Andy Lutomirski <luto@...capital.net> wrote:
> On Wed, Jul 2, 2014 at 7:29 PM, Alexei Starovoitov <ast@...mgrid.com> wrote:
>>
>> non-root API:
>>
>> ufd = bpf_create_map(local_map_id,… )
>> bpf_map_update/delete/lookup_elem(ufd,…)
>> 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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