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

[Daniel Borkmann]

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 <matt@xxxxxxxxxx>
> > Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
> > Cc: Paul Mackerras <paulus@xxxxxxxxx>
> > Cc: Alexei Starovoitov <ast@xxxxxx>
> > Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
> > Cc: Ananth N Mavinakayanahalli <ananth@xxxxxxxxxx>
> > Signed-off-by: Naveen N. Rao <naveen.n.rao@xxxxxxxxxxxxxxxxxx>
> > ---
> >   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?