Re: [PATCH v2] net: filter: BPF 'JIT' compiler for PPC64

On Jul 19, 2011, at 2:06 AM, Matt Evans wrote:

On 19/07/11 16:59, Kumar Gala wrote:

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On Jul 18, 2011, at 9:13 PM, Matt Evans wrote:
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An implementation of a code generator for BPF programs to speed up =

packet

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filtering on PPC64, inspired by Eric Dumazet's x86-64 version.
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Filter code is generated as an ABI-compliant function in =

module_alloc()'d mem

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with stackframe & prologue/epilogue generated if required (simple =

filters don't

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need anything more than an li/blr).  The filter's local variables, =

M[], live in

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registers.  Supports all BPF opcodes, although "complicated" loads =

from negative

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packet offsets (e.g. SKF_LL_OFF) are not yet supported.
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There are a couple of further optimisations left for future work; =

many-pass

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assembly with branch-reach reduction and a register allocator to =

push M[]

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variables into volatile registers would improve the code quality =

further.

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This currently supports big-endian 64-bit PowerPC only (but is =

fairly simple

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to port to PPC32 or LE!).
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Enabled in the same way as x86-64:
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	echo 1 > /proc/sys/net/core/bpf_jit_enable
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Or, enabled with extra debug output:
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	echo 2 > /proc/sys/net/core/bpf_jit_enable
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Signed-off-by: Matt Evans <redacted>
---
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V2: Removed some cut/paste woe in setting SEEN_X even on writes.
  Merci for le review, Eric!
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arch/powerpc/Kconfig                  |    1 +
arch/powerpc/Makefile                 |    3 +-
arch/powerpc/include/asm/ppc-opcode.h |   40 ++
arch/powerpc/net/Makefile             |    4 +
arch/powerpc/net/bpf_jit.S            |  138 +++++++

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can we rename to bpf_jit_64.S, since this doesn't work on PPC32.
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arch/powerpc/net/bpf_jit.h            |  227 +++++++++++
arch/powerpc/net/bpf_jit_comp.c       |  690 =

+++++++++++++++++++++++++++++++++

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same here, or split between bpf_jit_comp.c (shared between ppc32 & =

ppc64) and

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bpf_jit_comp_64.c

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A reasonable suggestion -- bpf_jit_64.S certainly.  I think it may not =

be worth

splitting bpf_jit_comp.c until we support both tho?  (I'm thinking
bpf_jit_comp_{32,64}.c would just house the stackframe generation code =

which is

the main difference, plus compile-time switched macros for the odd LD =

vs LWZ.)

If its most 64-bit specific than just go with bpf_jit_comp_64.c for now. =
 We can refactor later.

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Sorry it's not 32bit-friendly just yet (I knew you'd ask, hehe), I've =

postponed

that for when I get a mo :-)

:)