Messages in this thread | | | Subject | Re: [PATCH v7 net-next 1/3] filter: add Extended BPF interpreter and converter | From | Eric Dumazet <> | Date | Sun, 09 Mar 2014 07:49:34 -0700 |
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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.
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