linux-kernel - Re: [PATCH v8 net-next 2/2] net: filter: split filter.h and expose eBPF to user space

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Message-ID: <5400BAB7.80001@redhat.com>
Date:	Fri, 29 Aug 2014 19:39:03 +0200
From:	Daniel Borkmann <dborkman@...hat.com>
To:	Alexei Starovoitov <ast@...mgrid.com>
CC:	"David S. Miller" <davem@...emloft.net>,
	Ingo Molnar <mingo@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andy Lutomirski <luto@...capital.net>,
	Steven Rostedt <rostedt@...dmis.org>,
	Chema Gonzalez <chema@...gle.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Brendan Gregg <brendan.d.gregg@...il.com>,
	Namhyung Kim <namhyung@...nel.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Kees Cook <keescook@...omium.org>, linux-api@...r.kernel.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 net-next 2/2] net: filter: split filter.h and expose
 eBPF to user space

On 08/27/2014 10:37 PM, Alexei Starovoitov wrote:
> allow user space to generate eBPF programs
>
> uapi/linux/bpf.h: eBPF instruction set definition
>
> linux/filter.h: the rest

Very sorry for being late, but just a thought since we're touching user
space headers anyway ...

Wouldn't it be more consistent to have it organized as follows ...

  - uapi/linux/bpf.h    : classic BPF instruction set parts only
  - uapi/linux/ebpf.h   : eBPF instruction set definition (which also
                          includes uapi/linux/bpf.h though)
... and have ...

  - uapi/linux/filter.h : just include uapi/linux/bpf.h but rest is empty

That way, it would be more consistent ...

Old legacy application can stay with linux/filter.h; new applications
based on their needs can choose between linux/{e,}bpf.h and in the kernel,
we can just include linux/ebpf.h.

Right now, it seems, an eBPF user space program would need to include
2 header files in user space (linux/filter.h, linux/bpf.h) which I find
a bit confusing.

If you want, I could also take care of that later, but just thinking out
loudly ...

> This patch only moves macro definitions, but practically it freezes existing
> eBPF instruction set, though new instructions can still be added in the future.
>
> These eBPF definitions cannot go into uapi/linux/filter.h, since the names
> may conflict with existing applications.
>
> Full eBPF ISA description is in Documentation/networking/filter.txt
>
> Signed-off-by: Alexei Starovoitov <ast@...mgrid.com>
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