[PATCH] arm: bpf_jit: support MOD operation

[murzin.v@gmail.com (Vladimir Murzin)]

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On Wed, Aug 28, 2013 at 02:52:32AM +0400, Vladimir Murzin wrote:
> commit b6069a9570 (filter: add MOD operation) added generic
> support for modulus operation in BPF.
> 
> This patch brings JIT support for ARM.
> 
> Signed-off-by: Vladimir Murzin <murzin.v@gmail.com>
> ---
>  arch/arm/net/bpf_jit_32.c | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/arch/arm/net/bpf_jit_32.c b/arch/arm/net/bpf_jit_32.c
> index f50d223..0bfff55 100644
> --- a/arch/arm/net/bpf_jit_32.c
> +++ b/arch/arm/net/bpf_jit_32.c
> @@ -636,6 +636,24 @@ load_ind:
>  			update_on_xread(ctx);
>  			emit(ARM_MUL(r_A, r_A, r_X), ctx);
>  			break;
> +		case BPF_S_ALU_MOD_X: /* A %= X; */
> +			update_on_xread(ctx);
> +			emit(ARM_CMP_I(r_X, 0), ctx);
> +			emit_err_ret(ARM_COND_EQ, ctx);
> +			emit_udiv(r_scratch, r_A, r_X, ctx);
> +			emit(ARM_MUL(r_scratch, r_X, r_scratch), ctx);
> +			emit(ARM_SUB_R(r_A, r_A, r_scratch), ctx);
> +			break;
> +		case BPF_S_ALU_MOD_K: /* A %= K; */
> +			/*
> +			 * reuse ARM_R1 as the temp register - it should be safe
> +			 * as soon as udiv may touch it too.
> +			 */
> +			emit_mov_i(ARM_R1, k, ctx);
> +			emit_udiv(r_scratch, r_A, ARM_R1, ctx);
> +			emit(ARM_MUL(r_scratch, ARM_R1, r_scratch), ctx);
> +			emit(ARM_SUB_R(r_A, r_A, r_scratch), ctx);
> +			break;
>  		case BPF_S_ALU_DIV_K:
>  			/* current k == reciprocal_value(userspace k) */
>  			emit_mov_i(r_scratch, k, ctx);
> -- 
> 1.8.1.5
>