netdev - Re: [RESEND PATCH 2/2] ppc: bpf_jit: support MOD operation

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Date:	Mon, 23 Sep 2013 01:13:45 +1000
From:	Matt Evans <matt@...abs.org>
To:	Vladimir Murzin <murzin.v@...il.com>
Cc:	"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"benh@...nel.crashing.org" <benh@...nel.crashing.org>,
	"paulus@...ba.org" <paulus@...ba.org>,
	"edumazet@...gle.com" <edumazet@...gle.com>,
	"dborkman@...hat.com" <dborkman@...hat.com>,
	Vladimir Murzin <murzin.v@...il.com>
Subject: Re: [RESEND PATCH 2/2] ppc: bpf_jit: support MOD operation

Hi Vladimir,

On 21 Sep 2013, at 17:25, Vladimir Murzin <murzin.v@...il.com> wrote:

> commit b6069a9570 (filter: add MOD operation) added generic
> support for modulus operation in BPF.
> 
> This patch brings JIT support for PPC64
> 
> Signed-off-by: Vladimir Murzin <murzin.v@...il.com>
> Acked-by: Matt Evans <matt@...abs.org>

Not this version, though; see below. 

> ---
> arch/powerpc/net/bpf_jit_comp.c | 22 ++++++++++++++++++++++
> 1 file changed, 22 insertions(+)
> 
> diff --git a/arch/powerpc/net/bpf_jit_comp.c b/arch/powerpc/net/bpf_jit_comp.c
> index bf56e33..96f24dc 100644
> --- a/arch/powerpc/net/bpf_jit_comp.c
> +++ b/arch/powerpc/net/bpf_jit_comp.c
> @@ -193,6 +193,28 @@ static int bpf_jit_build_body(struct sk_filter *fp, u32 *image,
>                PPC_MUL(r_A, r_A, r_scratch1);
>            }
>            break;
> +        case BPF_S_ALU_MOD_X: /* A %= X; */
> +            ctx->seen |= SEEN_XREG;
> +            PPC_CMPWI(r_X, 0);
> +            if (ctx->pc_ret0 != -1) {
> +                PPC_BCC(COND_EQ, addrs[ctx->pc_ret0]);
> +            } else {
> +                PPC_BCC_SHORT(COND_NE, (ctx->idx*4)+12);
> +                PPC_LI(r_ret, 0);
> +                PPC_JMP(exit_addr);
> +            }
> +            PPC_DIVWU(r_scratch1, r_A, r_X);
> +            PPC_MUL(r_scratch1, r_X, r_scratch1);
> +            PPC_SUB(r_A, r_A, r_scratch1);
> +            break;
> +        case BPF_S_ALU_MOD_K: /* A %= K; */
> +#define r_scratch2 (r_scratch1 + 1)

Old version of this patch, still?  I had hoped that r_scratch2 would be defined in the header.

> +            PPC_LI32(r_scratch2, K);
> +            PPC_DIVWU(r_scratch1, r_A, r_scratch2);
> +            PPC_MUL(r_scratch1, r_scratch2, r_scratch1);
> +            PPC_SUB(r_A, r_A, r_scratch1);
> +#undef r_scratch2

And remember this guy too.. :)


Matt

> +            break;
>        case BPF_S_ALU_DIV_X: /* A /= X; */
>            ctx->seen |= SEEN_XREG;
>            PPC_CMPWI(r_X, 0);
> -- 
> 1.8.1.5
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