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

From: Alexei Starovoitov <[email-masked]>
Date: Fri, 1 Apr 2016 11:10:53 -0700

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!
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 ?

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?