Le mardi 19 juillet 2011 à 12:13 +1000, Matt Evans a écrit :
> 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 <m...@ozlabs.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 +++++++
> arch/powerpc/net/bpf_jit.h | 227 +++++++++++
> arch/powerpc/net/bpf_jit_comp.c | 690
> +++++++++++++++++++++++++++++++++
> 7 files changed, 1102 insertions(+), 1 deletions(-)
>
> + case BPF_S_ANC_CPU:
> +#ifdef CONFIG_SMP
> + /*
> + * PACA ptr is r13:
> + * raw_smp_processor_id() = local_paca->paca_index
> + */
This could break if one day linux supports more than 65536 cpus :)
> + PPC_LHZ_OFFS(r_A, 13,
> + offsetof(struct paca_struct, paca_index));
> +#else
> + PPC_LI(r_A, 0);
> +#endif
> + break;
> +
> +
> + case BPF_S_LDX_B_MSH:
> + /*
> + * x86 version drops packet (RET 0) when K<0, whereas
> + * interpreter does allow K<0 (__load_pointer, special
> + * ancillary data).
> + */
Hmm, thanks I'll take a look at this.
> + func = sk_load_byte_msh;
> + goto common_load;
> + break;
> +
> + /*** Jump and branches ***/
> + default:
> + /* The filter contains something cruel & unusual.
> + * We don't handle it, but also there shouldn't be
> + * anything missing from our list.
> + */
> + pr_err("BPF filter opcode %04x (@%d) unsupported\n",
> + filter[i].code, i);
You should at least ratelimit this message ?
On x86_64 I chose to silently fall back to interpretor for a "complex
filter" or "unsupported opcode".
> + return -ENOTSUPP;
> + }
> +
> + }
> + /* Set end-of-body-code address for exit. */
> + addrs[i] = ctx->idx * 4;
> +
> + return 0;
> +}
> +
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