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

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Date:	Tue, 19 Jul 2011 01:59:17 -0500
From:	Kumar Gala <galak@...nel.crashing.org>
To:	Matt Evans <matt@...abs.org>
Cc:	linuxppc-dev@...ts.ozlabs.org, netdev@...r.kernel.org
Subject: Re: [PATCH v2] net: filter: BPF 'JIT' compiler for PPC64


On Jul 18, 2011, at 9:13 PM, Matt Evans wrote:

> An implementation of a code generator for BPF programs to speed up packet
> filtering on PPC64, inspired by Eric Dumazet's x86-64 version.
> 
> Filter code is generated as an ABI-compliant function in module_alloc()'d mem
> with stackframe & prologue/epilogue generated if required (simple filters don't
> need anything more than an li/blr).  The filter's local variables, M[], live in
> registers.  Supports all BPF opcodes, although "complicated" loads from negative
> packet offsets (e.g. SKF_LL_OFF) are not yet supported.
> 
> There are a couple of further optimisations left for future work; many-pass
> assembly with branch-reach reduction and a register allocator to push M[]
> variables into volatile registers would improve the code quality further.
> 
> This currently supports big-endian 64-bit PowerPC only (but is fairly simple
> to port to PPC32 or LE!).
> 
> Enabled in the same way as x86-64:
> 
> 	echo 1 > /proc/sys/net/core/bpf_jit_enable
> 
> Or, enabled with extra debug output:
> 
> 	echo 2 > /proc/sys/net/core/bpf_jit_enable
> 
> Signed-off-by: Matt Evans <matt@...abs.org>
> ---
> 
> V2: Removed some cut/paste woe in setting SEEN_X even on writes.
>    Merci for le review, Eric!
> 
> 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 +++++++

can we rename to bpf_jit_64.S, since this doesn't work on PPC32.

> arch/powerpc/net/bpf_jit.h            |  227 +++++++++++
> arch/powerpc/net/bpf_jit_comp.c       |  690 +++++++++++++++++++++++++++++++++

same here, or split between bpf_jit_comp.c (shared between ppc32 & ppc64) and bpf_jit_comp_64.c

- k

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