On Sat, 2014-03-08 at 15:15 -0800, Alexei Starovoitov wrote:
> + if (BPF_SRC(fp->code) == BPF_K &&
> + (int)fp->k < 0) {
> + /* extended BPF immediates are signed,
> + * zero extend immediate into tmp register
> + * and use it in compare insn
> + */
> + insn->code = BPF_ALU | BPF_MOV | BPF_K;
> + insn->a_reg = 2;
> + insn->imm = fp->k;
> + insn++;
> +
> + insn->a_reg = 6;
> + insn->x_reg = 2;
> + bpf_src = BPF_X;
> + } else {
> + insn->a_reg = 6;
> + insn->x_reg = 7;
> + insn->imm = fp->k;
> + bpf_src = BPF_SRC(fp->code);
> + }
> + /* common case where 'jump_false' is next insn */
> + if (fp->jf == 0) {
> + insn->code = BPF_JMP | BPF_OP(fp->code) |
> + bpf_src;
> + tgt = i + fp->jt + 1;
> + EMIT_JMP;
> + break;
> + }
> + /* convert JEQ into JNE when 'jump_true' is next insn */
> + if (fp->jt == 0 && BPF_OP(fp->code) == BPF_JEQ) {
> + insn->code = BPF_JMP | BPF_JNE | bpf_src;
> + tgt = i + fp->jf + 1;
> + EMIT_JMP;
> + break;
> + }
> + /* other jumps are mapped into two insns: Jxx and JA */
> + tgt = i + fp->jt + 1;
> + insn->code = BPF_JMP | BPF_OP(fp->code) | bpf_src;
> + EMIT_JMP;
> +
> + insn++;
> + insn->code = BPF_JMP | BPF_JA;
> + tgt = i + fp->jf + 1;
> + EMIT_JMP;
> + break;
> +
> + /* ldxb 4*([14]&0xf) is remaped into 3 insns */
> + case BPF_LDX | BPF_MSH | BPF_B:
> + insn->code = BPF_LD | BPF_ABS | BPF_B;
> + insn->a_reg = 7;
> + insn->imm = fp->k;
> +
> + insn++;
> + insn->code = BPF_ALU | BPF_AND | BPF_K;
> + insn->a_reg = 7;
> + insn->imm = 0xf;
> +
> + insn++;
> + insn->code = BPF_ALU | BPF_LSH | BPF_K;
> + insn->a_reg = 7;
> + insn->imm = 2;
> + break;
> +
> + /* RET_K, RET_A are remaped into 2 insns */
> + case BPF_RET | BPF_A:
> + case BPF_RET | BPF_K:
> + insn->code = BPF_ALU | BPF_MOV |
> + (BPF_RVAL(fp->code) == BPF_K ? BPF_K : BPF_X);
> + insn->a_reg = 0;
> + insn->x_reg = 6;
> + insn->imm = fp->k;
> +
> + insn++;
> + insn->code = BPF_RET | BPF_K;
> + break;
What the hell is this ?
All this magical values, like 2, 6, 7, 10.
I am afraid nobody will be able to read this but you.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
