示例#1
0
文件: filter.c 项目: 19Dan01/linux
static u32 convert_skb_access(int skb_field, int dst_reg, int src_reg,
			      struct bpf_insn *insn_buf)
{
	struct bpf_insn *insn = insn_buf;

	switch (skb_field) {
	case SKF_AD_MARK:
		BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, mark) != 4);

		*insn++ = BPF_LDX_MEM(BPF_W, dst_reg, src_reg,
				      offsetof(struct sk_buff, mark));
		break;

	case SKF_AD_PKTTYPE:
		*insn++ = BPF_LDX_MEM(BPF_B, dst_reg, src_reg, PKT_TYPE_OFFSET());
		*insn++ = BPF_ALU32_IMM(BPF_AND, dst_reg, PKT_TYPE_MAX);
#ifdef __BIG_ENDIAN_BITFIELD
		*insn++ = BPF_ALU32_IMM(BPF_RSH, dst_reg, 5);
#endif
		break;

	case SKF_AD_QUEUE:
		BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, queue_mapping) != 2);

		*insn++ = BPF_LDX_MEM(BPF_H, dst_reg, src_reg,
				      offsetof(struct sk_buff, queue_mapping));
		break;

	case SKF_AD_VLAN_TAG:
	case SKF_AD_VLAN_TAG_PRESENT:
		BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, vlan_tci) != 2);
		BUILD_BUG_ON(VLAN_TAG_PRESENT != 0x1000);

		/* dst_reg = *(u16 *) (src_reg + offsetof(vlan_tci)) */
		*insn++ = BPF_LDX_MEM(BPF_H, dst_reg, src_reg,
				      offsetof(struct sk_buff, vlan_tci));
		if (skb_field == SKF_AD_VLAN_TAG) {
			*insn++ = BPF_ALU32_IMM(BPF_AND, dst_reg,
						~VLAN_TAG_PRESENT);
		} else {
			/* dst_reg >>= 12 */
			*insn++ = BPF_ALU32_IMM(BPF_RSH, dst_reg, 12);
			/* dst_reg &= 1 */
			*insn++ = BPF_ALU32_IMM(BPF_AND, dst_reg, 1);
		}
		break;
	}

	return insn - insn_buf;
}
示例#2
0
static bool convert_bpf_extensions(struct sock_filter *fp,
				   struct bpf_insn **insnp)
{
	struct bpf_insn *insn = *insnp;

	switch (fp->k) {
	case SKF_AD_OFF + SKF_AD_PROTOCOL:
		BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, protocol) != 2);

		/* A = *(u16 *) (CTX + offsetof(protocol)) */
		*insn++ = BPF_LDX_MEM(BPF_H, BPF_REG_A, BPF_REG_CTX,
				      offsetof(struct sk_buff, protocol));
		/* A = ntohs(A) [emitting a nop or swap16] */
		*insn = BPF_ENDIAN(BPF_FROM_BE, BPF_REG_A, 16);
		break;

	case SKF_AD_OFF + SKF_AD_PKTTYPE:
		*insn++ = BPF_LDX_MEM(BPF_B, BPF_REG_A, BPF_REG_CTX,
				      PKT_TYPE_OFFSET());
		*insn = BPF_ALU32_IMM(BPF_AND, BPF_REG_A, PKT_TYPE_MAX);
#ifdef __BIG_ENDIAN_BITFIELD
		insn++;
                *insn = BPF_ALU32_IMM(BPF_RSH, BPF_REG_A, 5);
#endif
		break;

	case SKF_AD_OFF + SKF_AD_IFINDEX:
	case SKF_AD_OFF + SKF_AD_HATYPE:
		BUILD_BUG_ON(FIELD_SIZEOF(struct net_device, ifindex) != 4);
		BUILD_BUG_ON(FIELD_SIZEOF(struct net_device, type) != 2);
		BUILD_BUG_ON(bytes_to_bpf_size(FIELD_SIZEOF(struct sk_buff, dev)) < 0);

		*insn++ = BPF_LDX_MEM(bytes_to_bpf_size(FIELD_SIZEOF(struct sk_buff, dev)),
				      BPF_REG_TMP, BPF_REG_CTX,
				      offsetof(struct sk_buff, dev));
		/* if (tmp != 0) goto pc + 1 */
		*insn++ = BPF_JMP_IMM(BPF_JNE, BPF_REG_TMP, 0, 1);
		*insn++ = BPF_EXIT_INSN();
		if (fp->k == SKF_AD_OFF + SKF_AD_IFINDEX)
			*insn = BPF_LDX_MEM(BPF_W, BPF_REG_A, BPF_REG_TMP,
					    offsetof(struct net_device, ifindex));
		else
			*insn = BPF_LDX_MEM(BPF_H, BPF_REG_A, BPF_REG_TMP,
					    offsetof(struct net_device, type));
		break;

	case SKF_AD_OFF + SKF_AD_MARK:
		BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, mark) != 4);

		*insn = BPF_LDX_MEM(BPF_W, BPF_REG_A, BPF_REG_CTX,
				    offsetof(struct sk_buff, mark));
		break;

	case SKF_AD_OFF + SKF_AD_RXHASH:
		BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, hash) != 4);

		*insn = BPF_LDX_MEM(BPF_W, BPF_REG_A, BPF_REG_CTX,
				    offsetof(struct sk_buff, hash));
		break;

	case SKF_AD_OFF + SKF_AD_QUEUE:
		BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, queue_mapping) != 2);

		*insn = BPF_LDX_MEM(BPF_H, BPF_REG_A, BPF_REG_CTX,
				    offsetof(struct sk_buff, queue_mapping));
		break;

	case SKF_AD_OFF + SKF_AD_VLAN_TAG:
	case SKF_AD_OFF + SKF_AD_VLAN_TAG_PRESENT:
		BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, vlan_tci) != 2);
		BUILD_BUG_ON(VLAN_TAG_PRESENT != 0x1000);

		/* A = *(u16 *) (CTX + offsetof(vlan_tci)) */
		*insn++ = BPF_LDX_MEM(BPF_H, BPF_REG_A, BPF_REG_CTX,
				      offsetof(struct sk_buff, vlan_tci));
		if (fp->k == SKF_AD_OFF + SKF_AD_VLAN_TAG) {
			*insn = BPF_ALU32_IMM(BPF_AND, BPF_REG_A,
					      ~VLAN_TAG_PRESENT);
		} else {
			/* A >>= 12 */
			*insn++ = BPF_ALU32_IMM(BPF_RSH, BPF_REG_A, 12);
			/* A &= 1 */
			*insn = BPF_ALU32_IMM(BPF_AND, BPF_REG_A, 1);
		}
		break;

	case SKF_AD_OFF + SKF_AD_PAY_OFFSET:
	case SKF_AD_OFF + SKF_AD_NLATTR:
	case SKF_AD_OFF + SKF_AD_NLATTR_NEST:
	case SKF_AD_OFF + SKF_AD_CPU:
	case SKF_AD_OFF + SKF_AD_RANDOM:
		/* arg1 = CTX */
		*insn++ = BPF_MOV64_REG(BPF_REG_ARG1, BPF_REG_CTX);
		/* arg2 = A */
		*insn++ = BPF_MOV64_REG(BPF_REG_ARG2, BPF_REG_A);
		/* arg3 = X */
		*insn++ = BPF_MOV64_REG(BPF_REG_ARG3, BPF_REG_X);
		/* Emit call(arg1=CTX, arg2=A, arg3=X) */
		switch (fp->k) {
		case SKF_AD_OFF + SKF_AD_PAY_OFFSET:
			*insn = BPF_EMIT_CALL(__skb_get_pay_offset);
			break;
		case SKF_AD_OFF + SKF_AD_NLATTR:
			*insn = BPF_EMIT_CALL(__skb_get_nlattr);
			break;
		case SKF_AD_OFF + SKF_AD_NLATTR_NEST:
			*insn = BPF_EMIT_CALL(__skb_get_nlattr_nest);
			break;
		case SKF_AD_OFF + SKF_AD_CPU:
			*insn = BPF_EMIT_CALL(__get_raw_cpu_id);
			break;
		case SKF_AD_OFF + SKF_AD_RANDOM:
			*insn = BPF_EMIT_CALL(__get_random_u32);
			break;
		}
		break;

	case SKF_AD_OFF + SKF_AD_ALU_XOR_X:
		/* A ^= X */
		*insn = BPF_ALU32_REG(BPF_XOR, BPF_REG_A, BPF_REG_X);
		break;

	default:
		/* This is just a dummy call to avoid letting the compiler
		 * evict __bpf_call_base() as an optimization. Placed here
		 * where no-one bothers.
		 */
		BUG_ON(__bpf_call_base(0, 0, 0, 0, 0) != 0);
		return false;
	}
示例#3
0
/* Assemble the body code between the prologue & epilogue. */
static int bpf_jit_build_body(struct bpf_prog *fp, u32 *image,
			      struct codegen_context *ctx,
			      unsigned int *addrs)
{
	const struct sock_filter *filter = fp->insns;
	int flen = fp->len;
	u8 *func;
	unsigned int true_cond;
	int i;

	/* Start of epilogue code */
	unsigned int exit_addr = addrs[flen];

	for (i = 0; i < flen; i++) {
		unsigned int K = filter[i].k;
		u16 code = bpf_anc_helper(&filter[i]);

		/*
		 * addrs[] maps a BPF bytecode address into a real offset from
		 * the start of the body code.
		 */
		addrs[i] = ctx->idx * 4;

		switch (code) {
			/*** ALU ops ***/
		case BPF_ALU | BPF_ADD | BPF_X: /* A += X; */
			ctx->seen |= SEEN_XREG;
			PPC_ADD(r_A, r_A, r_X);
			break;
		case BPF_ALU | BPF_ADD | BPF_K: /* A += K; */
			if (!K)
				break;
			PPC_ADDI(r_A, r_A, IMM_L(K));
			if (K >= 32768)
				PPC_ADDIS(r_A, r_A, IMM_HA(K));
			break;
		case BPF_ALU | BPF_SUB | BPF_X: /* A -= X; */
			ctx->seen |= SEEN_XREG;
			PPC_SUB(r_A, r_A, r_X);
			break;
		case BPF_ALU | BPF_SUB | BPF_K: /* A -= K */
			if (!K)
				break;
			PPC_ADDI(r_A, r_A, IMM_L(-K));
			if (K >= 32768)
				PPC_ADDIS(r_A, r_A, IMM_HA(-K));
			break;
		case BPF_ALU | BPF_MUL | BPF_X: /* A *= X; */
			ctx->seen |= SEEN_XREG;
			PPC_MUL(r_A, r_A, r_X);
			break;
		case BPF_ALU | BPF_MUL | BPF_K: /* A *= K */
			if (K < 32768)
				PPC_MULI(r_A, r_A, K);
			else {
				PPC_LI32(r_scratch1, K);
				PPC_MUL(r_A, r_A, r_scratch1);
			}
			break;
		case BPF_ALU | BPF_MOD | BPF_X: /* A %= X; */
		case BPF_ALU | BPF_DIV | BPF_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);
			}
			if (code == (BPF_ALU | BPF_MOD | BPF_X)) {
				PPC_DIVWU(r_scratch1, r_A, r_X);
				PPC_MUL(r_scratch1, r_X, r_scratch1);
				PPC_SUB(r_A, r_A, r_scratch1);
			} else {
				PPC_DIVWU(r_A, r_A, r_X);
			}
			break;
		case BPF_ALU | BPF_MOD | BPF_K: /* A %= K; */
			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);
			break;
		case BPF_ALU | BPF_DIV | BPF_K: /* A /= K */
			if (K == 1)
				break;
			PPC_LI32(r_scratch1, K);
			PPC_DIVWU(r_A, r_A, r_scratch1);
			break;
		case BPF_ALU | BPF_AND | BPF_X:
			ctx->seen |= SEEN_XREG;
			PPC_AND(r_A, r_A, r_X);
			break;
		case BPF_ALU | BPF_AND | BPF_K:
			if (!IMM_H(K))
				PPC_ANDI(r_A, r_A, K);
			else {
				PPC_LI32(r_scratch1, K);
				PPC_AND(r_A, r_A, r_scratch1);
			}
			break;
		case BPF_ALU | BPF_OR | BPF_X:
			ctx->seen |= SEEN_XREG;
			PPC_OR(r_A, r_A, r_X);
			break;
		case BPF_ALU | BPF_OR | BPF_K:
			if (IMM_L(K))
				PPC_ORI(r_A, r_A, IMM_L(K));
			if (K >= 65536)
				PPC_ORIS(r_A, r_A, IMM_H(K));
			break;
		case BPF_ANC | SKF_AD_ALU_XOR_X:
		case BPF_ALU | BPF_XOR | BPF_X: /* A ^= X */
			ctx->seen |= SEEN_XREG;
			PPC_XOR(r_A, r_A, r_X);
			break;
		case BPF_ALU | BPF_XOR | BPF_K: /* A ^= K */
			if (IMM_L(K))
				PPC_XORI(r_A, r_A, IMM_L(K));
			if (K >= 65536)
				PPC_XORIS(r_A, r_A, IMM_H(K));
			break;
		case BPF_ALU | BPF_LSH | BPF_X: /* A <<= X; */
			ctx->seen |= SEEN_XREG;
			PPC_SLW(r_A, r_A, r_X);
			break;
		case BPF_ALU | BPF_LSH | BPF_K:
			if (K == 0)
				break;
			else
				PPC_SLWI(r_A, r_A, K);
			break;
		case BPF_ALU | BPF_RSH | BPF_X: /* A >>= X; */
			ctx->seen |= SEEN_XREG;
			PPC_SRW(r_A, r_A, r_X);
			break;
		case BPF_ALU | BPF_RSH | BPF_K: /* A >>= K; */
			if (K == 0)
				break;
			else
				PPC_SRWI(r_A, r_A, K);
			break;
		case BPF_ALU | BPF_NEG:
			PPC_NEG(r_A, r_A);
			break;
		case BPF_RET | BPF_K:
			PPC_LI32(r_ret, K);
			if (!K) {
				if (ctx->pc_ret0 == -1)
					ctx->pc_ret0 = i;
			}
			/*
			 * If this isn't the very last instruction, branch to
			 * the epilogue if we've stuff to clean up.  Otherwise,
			 * if there's nothing to tidy, just return.  If we /are/
			 * the last instruction, we're about to fall through to
			 * the epilogue to return.
			 */
			if (i != flen - 1) {
				/*
				 * Note: 'seen' is properly valid only on pass
				 * #2.	Both parts of this conditional are the
				 * same instruction size though, meaning the
				 * first pass will still correctly determine the
				 * code size/addresses.
				 */
				if (ctx->seen)
					PPC_JMP(exit_addr);
				else
					PPC_BLR();
			}
			break;
		case BPF_RET | BPF_A:
			PPC_MR(r_ret, r_A);
			if (i != flen - 1) {
				if (ctx->seen)
					PPC_JMP(exit_addr);
				else
					PPC_BLR();
			}
			break;
		case BPF_MISC | BPF_TAX: /* X = A */
			PPC_MR(r_X, r_A);
			break;
		case BPF_MISC | BPF_TXA: /* A = X */
			ctx->seen |= SEEN_XREG;
			PPC_MR(r_A, r_X);
			break;

			/*** Constant loads/M[] access ***/
		case BPF_LD | BPF_IMM: /* A = K */
			PPC_LI32(r_A, K);
			break;
		case BPF_LDX | BPF_IMM: /* X = K */
			PPC_LI32(r_X, K);
			break;
		case BPF_LD | BPF_MEM: /* A = mem[K] */
			PPC_MR(r_A, r_M + (K & 0xf));
			ctx->seen |= SEEN_MEM | (1<<(K & 0xf));
			break;
		case BPF_LDX | BPF_MEM: /* X = mem[K] */
			PPC_MR(r_X, r_M + (K & 0xf));
			ctx->seen |= SEEN_MEM | (1<<(K & 0xf));
			break;
		case BPF_ST: /* mem[K] = A */
			PPC_MR(r_M + (K & 0xf), r_A);
			ctx->seen |= SEEN_MEM | (1<<(K & 0xf));
			break;
		case BPF_STX: /* mem[K] = X */
			PPC_MR(r_M + (K & 0xf), r_X);
			ctx->seen |= SEEN_XREG | SEEN_MEM | (1<<(K & 0xf));
			break;
		case BPF_LD | BPF_W | BPF_LEN: /*	A = skb->len; */
			BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, len) != 4);
			PPC_LWZ_OFFS(r_A, r_skb, offsetof(struct sk_buff, len));
			break;
		case BPF_LDX | BPF_W | BPF_LEN: /* X = skb->len; */
			PPC_LWZ_OFFS(r_X, r_skb, offsetof(struct sk_buff, len));
			break;

			/*** Ancillary info loads ***/
		case BPF_ANC | SKF_AD_PROTOCOL: /* A = ntohs(skb->protocol); */
			BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff,
						  protocol) != 2);
			PPC_NTOHS_OFFS(r_A, r_skb, offsetof(struct sk_buff,
							    protocol));
			break;
		case BPF_ANC | SKF_AD_IFINDEX:
		case BPF_ANC | SKF_AD_HATYPE:
			BUILD_BUG_ON(FIELD_SIZEOF(struct net_device,
						ifindex) != 4);
			BUILD_BUG_ON(FIELD_SIZEOF(struct net_device,
						type) != 2);
			PPC_LL_OFFS(r_scratch1, r_skb, offsetof(struct sk_buff,
								dev));
			PPC_CMPDI(r_scratch1, 0);
			if (ctx->pc_ret0 != -1) {
				PPC_BCC(COND_EQ, addrs[ctx->pc_ret0]);
			} else {
				/* Exit, returning 0; first pass hits here. */
				PPC_BCC_SHORT(COND_NE, ctx->idx * 4 + 12);
				PPC_LI(r_ret, 0);
				PPC_JMP(exit_addr);
			}
			if (code == (BPF_ANC | SKF_AD_IFINDEX)) {
				PPC_LWZ_OFFS(r_A, r_scratch1,
				     offsetof(struct net_device, ifindex));
			} else {
				PPC_LHZ_OFFS(r_A, r_scratch1,
				     offsetof(struct net_device, type));
			}

			break;
		case BPF_ANC | SKF_AD_MARK:
			BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, mark) != 4);
			PPC_LWZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
							  mark));
			break;
		case BPF_ANC | SKF_AD_RXHASH:
			BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, hash) != 4);
			PPC_LWZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
							  hash));
			break;
		case BPF_ANC | SKF_AD_VLAN_TAG:
		case BPF_ANC | SKF_AD_VLAN_TAG_PRESENT:
			BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, vlan_tci) != 2);
			BUILD_BUG_ON(VLAN_TAG_PRESENT != 0x1000);

			PPC_LHZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
							  vlan_tci));
			if (code == (BPF_ANC | SKF_AD_VLAN_TAG)) {
				PPC_ANDI(r_A, r_A, ~VLAN_TAG_PRESENT);
			} else {
				PPC_ANDI(r_A, r_A, VLAN_TAG_PRESENT);
				PPC_SRWI(r_A, r_A, 12);
			}
			break;
		case BPF_ANC | SKF_AD_QUEUE:
			BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff,
						  queue_mapping) != 2);
			PPC_LHZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
							  queue_mapping));
			break;
		case BPF_ANC | SKF_AD_PKTTYPE:
			PPC_LBZ_OFFS(r_A, r_skb, PKT_TYPE_OFFSET());
			PPC_ANDI(r_A, r_A, PKT_TYPE_MAX);
			PPC_SRWI(r_A, r_A, 5);
			break;
		case BPF_ANC | SKF_AD_CPU:
			PPC_BPF_LOAD_CPU(r_A);
			break;
			/*** Absolute loads from packet header/data ***/
		case BPF_LD | BPF_W | BPF_ABS:
			func = CHOOSE_LOAD_FUNC(K, sk_load_word);
			goto common_load;
		case BPF_LD | BPF_H | BPF_ABS:
			func = CHOOSE_LOAD_FUNC(K, sk_load_half);
			goto common_load;
		case BPF_LD | BPF_B | BPF_ABS:
			func = CHOOSE_LOAD_FUNC(K, sk_load_byte);
		common_load:
			/* Load from [K]. */
			ctx->seen |= SEEN_DATAREF;
			PPC_FUNC_ADDR(r_scratch1, func);
			PPC_MTLR(r_scratch1);
			PPC_LI32(r_addr, K);
			PPC_BLRL();
			/*
			 * Helper returns 'lt' condition on error, and an
			 * appropriate return value in r3
			 */
			PPC_BCC(COND_LT, exit_addr);
			break;

			/*** Indirect loads from packet header/data ***/
		case BPF_LD | BPF_W | BPF_IND:
			func = sk_load_word;
			goto common_load_ind;
		case BPF_LD | BPF_H | BPF_IND:
			func = sk_load_half;
			goto common_load_ind;
		case BPF_LD | BPF_B | BPF_IND:
			func = sk_load_byte;
		common_load_ind:
			/*
			 * Load from [X + K].  Negative offsets are tested for
			 * in the helper functions.
			 */
			ctx->seen |= SEEN_DATAREF | SEEN_XREG;
			PPC_FUNC_ADDR(r_scratch1, func);
			PPC_MTLR(r_scratch1);
			PPC_ADDI(r_addr, r_X, IMM_L(K));
			if (K >= 32768)
				PPC_ADDIS(r_addr, r_addr, IMM_HA(K));
			PPC_BLRL();
			/* If error, cr0.LT set */
			PPC_BCC(COND_LT, exit_addr);
			break;

		case BPF_LDX | BPF_B | BPF_MSH:
			func = CHOOSE_LOAD_FUNC(K, sk_load_byte_msh);
			goto common_load;
			break;

			/*** Jump and branches ***/
		case BPF_JMP | BPF_JA:
			if (K != 0)
				PPC_JMP(addrs[i + 1 + K]);
			break;

		case BPF_JMP | BPF_JGT | BPF_K:
		case BPF_JMP | BPF_JGT | BPF_X:
			true_cond = COND_GT;
			goto cond_branch;
		case BPF_JMP | BPF_JGE | BPF_K:
		case BPF_JMP | BPF_JGE | BPF_X:
			true_cond = COND_GE;
			goto cond_branch;
		case BPF_JMP | BPF_JEQ | BPF_K:
		case BPF_JMP | BPF_JEQ | BPF_X:
			true_cond = COND_EQ;
			goto cond_branch;
		case BPF_JMP | BPF_JSET | BPF_K:
		case BPF_JMP | BPF_JSET | BPF_X:
			true_cond = COND_NE;
			/* Fall through */
		cond_branch:
			/* same targets, can avoid doing the test :) */
			if (filter[i].jt == filter[i].jf) {
				if (filter[i].jt > 0)
					PPC_JMP(addrs[i + 1 + filter[i].jt]);
				break;
			}

			switch (code) {
			case BPF_JMP | BPF_JGT | BPF_X:
			case BPF_JMP | BPF_JGE | BPF_X:
			case BPF_JMP | BPF_JEQ | BPF_X:
				ctx->seen |= SEEN_XREG;
				PPC_CMPLW(r_A, r_X);
				break;
			case BPF_JMP | BPF_JSET | BPF_X:
				ctx->seen |= SEEN_XREG;
				PPC_AND_DOT(r_scratch1, r_A, r_X);
				break;
			case BPF_JMP | BPF_JEQ | BPF_K:
			case BPF_JMP | BPF_JGT | BPF_K:
			case BPF_JMP | BPF_JGE | BPF_K:
				if (K < 32768)
					PPC_CMPLWI(r_A, K);
				else {
					PPC_LI32(r_scratch1, K);
					PPC_CMPLW(r_A, r_scratch1);
				}
				break;
			case BPF_JMP | BPF_JSET | BPF_K:
				if (K < 32768)
					/* PPC_ANDI is /only/ dot-form */
					PPC_ANDI(r_scratch1, r_A, K);
				else {
					PPC_LI32(r_scratch1, K);
					PPC_AND_DOT(r_scratch1, r_A,
						    r_scratch1);
				}
				break;
			}
			/* Sometimes branches are constructed "backward", with
			 * the false path being the branch and true path being
			 * a fallthrough to the next instruction.
			 */
			if (filter[i].jt == 0)
				/* Swap the sense of the branch */
				PPC_BCC(true_cond ^ COND_CMP_TRUE,
					addrs[i + 1 + filter[i].jf]);
			else {
				PPC_BCC(true_cond, addrs[i + 1 + filter[i].jt]);
				if (filter[i].jf != 0)
					PPC_JMP(addrs[i + 1 + filter[i].jf]);
			}
			break;
		default:
			/* The filter contains something cruel & unusual.
			 * We don't handle it, but also there shouldn't be
			 * anything missing from our list.
			 */
			if (printk_ratelimit())
				pr_err("BPF filter opcode %04x (@%d) unsupported\n",
				       filter[i].code, i);
			return -ENOTSUPP;
		}

	}
	/* Set end-of-body-code address for exit. */
	addrs[i] = ctx->idx * 4;

	return 0;
}