Subject: Re: [RFC PATCH 6/6] ppc: ebpf/jit: Implement JIT compiler for extended BPF

From: Daniel Borkmann <[email-masked]>
Date: Fri, 01 Apr 2016 20:34:57 +0200

On 04/01/2016 08:10 PM, Alexei Starovoitov wrote:
> On 4/1/16 2:58 AM, Naveen N. Rao wrote:
>> PPC64 eBPF JIT compiler. Works for both ABIv1 and ABIv2.
>>
>> Enable with:
>> echo 1 > /proc/sys/net/core/bpf_jit_enable
>> or
>> echo 2 > /proc/sys/net/core/bpf_jit_enable
>>
>> ... to see the generated JIT code. This can further be processed with
>> tools/net/bpf_jit_disasm.
>>
>> With CONFIG_TEST_BPF=m and 'modprobe test_bpf':
>> test_bpf: Summary: 291 PASSED, 0 FAILED, [234/283 JIT'ed]
>>
>> ... on both ppc64 BE and LE.
>>
>> The details of the approach are documented through various comments in
>> the code, as are the TODOs. Some of the prominent TODOs include
>> implementing BPF tail calls and skb loads.
>>
>> Cc: Matt Evans <[email-masked]>
>> Cc: Michael Ellerman <[email-masked]>
>> Cc: Paul Mackerras <[email-masked]>
>> Cc: Alexei Starovoitov <[email-masked]>
>> Cc: "David S. Miller" <[email-masked]>
>> Cc: Ananth N Mavinakayanahalli <[email-masked]>
>> Signed-off-by: Naveen N. Rao <[email-masked]>
>> ---
>>   arch/powerpc/include/asm/ppc-opcode.h |  19 +-
>>   arch/powerpc/net/Makefile             |   4 +
>>   arch/powerpc/net/bpf_jit.h            |  66 ++-
>>   arch/powerpc/net/bpf_jit64.h          |  58 +++
>>   arch/powerpc/net/bpf_jit_comp64.c     | 828 ++++++++++++++++++++++++++++++++++
>>   5 files changed, 973 insertions(+), 2 deletions(-)
>>   create mode 100644 arch/powerpc/net/bpf_jit64.h
>>   create mode 100644 arch/powerpc/net/bpf_jit_comp64.c
> ...
>> -#ifdef CONFIG_PPC64
>> +#if defined(CONFIG_PPC64) && (!defined(_CALL_ELF) || _CALL_ELF != 2)
>
> impressive stuff!

+1, awesome to see another one!

> Everything nicely documented. Could you add few words for the above
> condition as well ?
> Or may be a new macro, since it occurs many times?
> What are these _CALL_ELF == 2 and != 2 conditions mean? ppc ABIs ?
> Will there ever be v3 ?

Minor TODO would also be to convert to use bpf_jit_binary_alloc() and
bpf_jit_binary_free() API for the image, which is done by other eBPF
jits, too.

> So far most of the bpf jits were going via net-next tree, but if
> in this case no changes to the core is necessary then I guess it's fine
> to do it via powerpc tree. What's your plan?
>