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

On 2016/04/01 08:34PM, Daniel Borkmann wrote:

On 04/01/2016 08:10 PM, Alexei Starovoitov wrote:

quoted

On 4/1/16 2:58 AM, Naveen N. Rao wrote:

quoted

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 <redacted>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <redacted>
Cc: Alexei Starovoitov <redacted>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Ananth N Mavinakayanahalli <redacted>
Signed-off-by: Naveen N. Rao <redacted>
---
 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

...

quoted

-#ifdef CONFIG_PPC64
+#if defined(CONFIG_PPC64) && (!defined(_CALL_ELF) || _CALL_ELF != 2)

impressive stuff!

+1, awesome to see another one!

Thanks!

quoted

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 ?

Yes, there are 2 ABIs: ppc64 (ABIv1) -- big endian and the recently 
introduced ppc64le (ABIv2) which is currently only little endian. There 
is also ppc32...

Good suggestion about using a macro. I will put out a patch for that.

quoted

Will there ever be v3 ?

Hope not! ;)

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.

Sure. I will make that change.

quoted

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?

I initially thought this has to go through the powerpc tree. I don't 
really have a preference and I'll allow the maintainers to take a call 
on that. I do however need a review of the JIT code from Michael
Ellerman/Paul Mackerras.


- Naveen