From: Daniel Borkmann <dborkman@redhat•com>
To: Alexei Starovoitov <ast@plumgrid•com>
Cc: "David S. Miller" <davem@davemloft•net>,
Ingo Molnar <mingo@kernel•org>, Will Drewry <wad@chromium•org>,
Steven Rostedt <rostedt@goodmis•org>,
Peter Zijlstra <a.p.zijlstra@chello•nl>,
"H. Peter Anvin" <hpa@zytor•com>,
Hagen Paul Pfeifer <hagen@jauu•net>,
Jesse Gross <jesse@nicira•com>,
Thomas Gleixner <tglx@linutronix•de>,
Masami Hiramatsu <masami.hiramatsu.pt@hitachi•com>,
Tom Zanussi <tom.zanussi@linux•intel.com>,
Jovi Zhangwei <jovi.zhangwei@gmail•com>,
Eric Dumazet <edumazet@google•com>,
Linus Torvalds <torvalds@linux-foundation•org>,
Andrew Morton <akpm@linux-foundation•org>,
Frederic Weisbecker <fweisbec@gmail•com>,
Arnaldo Carvalho de Melo <acme@infradead•org>,
Pekka Enberg <penberg@iki•fi>,
Arjan van de Ven <arjan@infradead•org>,
Christoph Hellwig <hch@infradead•org>,
linux-kernel@vger•kernel.org, netdev@vger•kernel.org
Subject: Re: [PATCH v4 net-next 1/3] Extended BPF interpreter and converter
Date: Tue, 04 Mar 2014 19:23:16 +0100 [thread overview]
Message-ID: <53161A14.3060405@redhat.com> (raw)
In-Reply-To: <CAMEtUuwzo9JdcHdUvSOecmK5QD=5vcRLEE3DsLth=mxXnPOocw@mail.gmail.com>
On 03/04/2014 06:09 PM, Alexei Starovoitov wrote:
> On Tue, Mar 4, 2014 at 1:59 AM, Daniel Borkmann <dborkman@redhat•com> wrote:
...
>> Hmm, so the case statement is about BPF_RET | BPF_A and BPF_RET | BPF_K
>> but BPF_RET | BPF_X is not mentioned. However, in BPF_SRC(fp->code)
>> selection you fall back to BPF_X if it doesn't equal BPF_K? Is that
>> correct? And, you probably also need to handle BPF_RET | BPF_X ?
>
> :) that design choice of original BPF always puzzled me.
> BPF_A macro only used in one insn: BPF_RET + BPF_A
> and all other insns use BPF_K and BPF_X
> and though comment in uapi/filter.h says "ret - BPF_K and BPF_X also apply"
> this is not true, since sk_chk_filter() only allows ret+a and ret+k
> libpcap is equally confused. It never generates ret+x, but has few
> places in the code
> that can recognize it. I guess that's an artifact of distant past.
Good point, ret+a and ret+k are main users anyway, though we could fix
that limitation actually. ;)
> epbf has only one RET insn that takes register R0 and returns it.
> That is similar to real CPU 'ret' insn and done to make epbf easier
> to generate from gcc/llvm point of view.
> ebpf jit converts 'ret' into 'leave; ret' on x86_64.
>
> so original bpf+k and bpf+a are converted into 'mov r0, [a or k]; ret r0'
>
> btw, if there is interest I can put ebpf testsuite into tools/net/
Yes, please. Would be great if you can place the test suite under:
tools/testing/selftests/net/bpf/
I believe some stuff there could get its own folder e.g. "packet"
for PF_PACKET test cases etc, so that we can easily arrange them.
next prev parent reply other threads:[~2014-03-04 18:23 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-03-04 5:18 [PATCH v4 net-next 0/3] Extended BPF, converter, seccomp, doc Alexei Starovoitov
2014-03-04 5:18 ` [PATCH v4 net-next 1/3] Extended BPF interpreter and converter Alexei Starovoitov
2014-03-04 9:59 ` Daniel Borkmann
2014-03-04 17:09 ` Alexei Starovoitov
2014-03-04 18:23 ` Daniel Borkmann [this message]
2014-03-04 14:28 ` Hagen Paul Pfeifer
2014-03-04 17:53 ` Alexei Starovoitov
2014-03-04 18:31 ` Daniel Borkmann
2014-03-04 5:18 ` [PATCH v4 net-next 2/3] RFC: convert seccomp to use extended BPF Alexei Starovoitov
2014-03-04 5:18 ` [PATCH v4 net-next 3/3] Extended BPF documentation Alexei Starovoitov
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