Ejemplo n.º 1
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; */
			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_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_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 {
				/*
				 * Exit, returning 0; first pass hits here
				 * (longer worst-case code size).
				 */
				PPC_BCC_SHORT(COND_NE, (ctx->idx*4)+12);
				PPC_LI(r_ret, 0);
				PPC_JMP(exit_addr);
			}
			PPC_DIVWU(r_A, r_A, r_X);
			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:
			PPC_LD_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);
			}
			BUILD_BUG_ON(FIELD_SIZEOF(struct net_device,
						  ifindex) != 4);
			PPC_LWZ_OFFS(r_A, r_scratch1,
				     offsetof(struct net_device, ifindex));
			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_CPU:
#ifdef CONFIG_SMP
			/*
			 * PACA ptr is r13:
			 * raw_smp_processor_id() = local_paca->paca_index
			 */
			BUILD_BUG_ON(FIELD_SIZEOF(struct paca_struct,
						  paca_index) != 2);
			PPC_LHZ_OFFS(r_A, 13,
				     offsetof(struct paca_struct, paca_index));
#else
			PPC_LI(r_A, 0);
#endif
			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_LI64(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_LI64(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;
}
Ejemplo n.º 2
0
/* Assemble the body code between the prologue & epilogue. */
static int bpf_jit_build_body(struct sk_filter *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;

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

		switch (filter[i].code) {
			/*** ALU ops ***/
		case BPF_S_ALU_ADD_X: /* A += X; */
			ctx->seen |= SEEN_XREG;
			PPC_ADD(r_A, r_A, r_X);
			break;
		case BPF_S_ALU_ADD_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_S_ALU_SUB_X: /* A -= X; */
			ctx->seen |= SEEN_XREG;
			PPC_SUB(r_A, r_A, r_X);
			break;
		case BPF_S_ALU_SUB_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_S_ALU_MUL_X: /* A *= X; */
			ctx->seen |= SEEN_XREG;
			PPC_MUL(r_A, r_A, r_X);
			break;
		case BPF_S_ALU_MUL_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_S_ALU_DIV_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 {
				/*
				 * Exit, returning 0; first pass hits here
				 * (longer worst-case code size).
				 */
				PPC_BCC_SHORT(COND_NE, (ctx->idx*4)+12);
				PPC_LI(r_ret, 0);
				PPC_JMP(exit_addr);
			}
			PPC_DIVWU(r_A, r_A, r_X);
			break;
		case BPF_S_ALU_DIV_K: /* A = reciprocal_divide(A, K); */
			PPC_LI32(r_scratch1, K);
			/* Top 32 bits of 64bit result -> A */
			PPC_MULHWU(r_A, r_A, r_scratch1);
			break;
		case BPF_S_ALU_AND_X:
			ctx->seen |= SEEN_XREG;
			PPC_AND(r_A, r_A, r_X);
			break;
		case BPF_S_ALU_AND_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_S_ALU_OR_X:
			ctx->seen |= SEEN_XREG;
			PPC_OR(r_A, r_A, r_X);
			break;
		case BPF_S_ALU_OR_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_S_ALU_LSH_X: /* A <<= X; */
			ctx->seen |= SEEN_XREG;
			PPC_SLW(r_A, r_A, r_X);
			break;
		case BPF_S_ALU_LSH_K:
			if (K == 0)
				break;
			else
				PPC_SLWI(r_A, r_A, K);
			break;
		case BPF_S_ALU_RSH_X: /* A >>= X; */
			ctx->seen |= SEEN_XREG;
			PPC_SRW(r_A, r_A, r_X);
			break;
		case BPF_S_ALU_RSH_K: /* A >>= K; */
			if (K == 0)
				break;
			else
				PPC_SRWI(r_A, r_A, K);
			break;
		case BPF_S_ALU_NEG:
			PPC_NEG(r_A, r_A);
			break;
		case BPF_S_RET_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_S_RET_A:
			PPC_MR(r_ret, r_A);
			if (i != flen - 1) {
				if (ctx->seen)
					PPC_JMP(exit_addr);
				else
					PPC_BLR();
			}
			break;
		case BPF_S_MISC_TAX: /* X = A */
			PPC_MR(r_X, r_A);
			break;
		case BPF_S_MISC_TXA: /* A = X */
			ctx->seen |= SEEN_XREG;
			PPC_MR(r_A, r_X);
			break;

			/*** Constant loads/M[] access ***/
		case BPF_S_LD_IMM: /* A = K */
			PPC_LI32(r_A, K);
			break;
		case BPF_S_LDX_IMM: /* X = K */
			PPC_LI32(r_X, K);
			break;
		case BPF_S_LD_MEM: /* A = mem[K] */
			PPC_MR(r_A, r_M + (K & 0xf));
			ctx->seen |= SEEN_MEM | (1<<(K & 0xf));
			break;
		case BPF_S_LDX_MEM: /* X = mem[K] */
			PPC_MR(r_X, r_M + (K & 0xf));
			ctx->seen |= SEEN_MEM | (1<<(K & 0xf));
			break;
		case BPF_S_ST: /* mem[K] = A */
			PPC_MR(r_M + (K & 0xf), r_A);
			ctx->seen |= SEEN_MEM | (1<<(K & 0xf));
			break;
		case BPF_S_STX: /* mem[K] = X */
			PPC_MR(r_M + (K & 0xf), r_X);
			ctx->seen |= SEEN_XREG | SEEN_MEM | (1<<(K & 0xf));
			break;
		case BPF_S_LD_W_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_S_LDX_W_LEN: /* X = skb->len; */
			PPC_LWZ_OFFS(r_X, r_skb, offsetof(struct sk_buff, len));
			break;

			/*** Ancillary info loads ***/

			/* None of the BPF_S_ANC* codes appear to be passed by
			 * sk_chk_filter().  The interpreter and the x86 BPF
			 * compiler implement them so we do too -- they may be
			 * planted in future.
			 */
		case BPF_S_ANC_PROTOCOL: /* A = ntohs(skb->protocol); */
			BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff,
						  protocol) != 2);
			PPC_LHZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
							  protocol));
			/* ntohs is a NOP with BE loads. */
			break;
		case BPF_S_ANC_IFINDEX:
			PPC_LD_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);
			}
			BUILD_BUG_ON(FIELD_SIZEOF(struct net_device,
						  ifindex) != 4);
			PPC_LWZ_OFFS(r_A, r_scratch1,
				     offsetof(struct net_device, ifindex));
			break;
		case BPF_S_ANC_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_S_ANC_RXHASH:
			BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, rxhash) != 4);
			PPC_LWZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
							  rxhash));
			break;
		case BPF_S_ANC_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_S_ANC_CPU:
#ifdef CONFIG_SMP
			/*
			 * PACA ptr is r13:
			 * raw_smp_processor_id() = local_paca->paca_index
			 */
			BUILD_BUG_ON(FIELD_SIZEOF(struct paca_struct,
						  paca_index) != 2);
			PPC_LHZ_OFFS(r_A, 13,
				     offsetof(struct paca_struct, paca_index));
#else
			PPC_LI(r_A, 0);
#endif
			break;

			/*** Absolute loads from packet header/data ***/
		case BPF_S_LD_W_ABS:
			func = sk_load_word;
			goto common_load;
		case BPF_S_LD_H_ABS:
			func = sk_load_half;
			goto common_load;
		case BPF_S_LD_B_ABS:
			func = sk_load_byte;
		common_load:
			/*
			 * Load from [K].  Reference with the (negative)
			 * SKF_NET_OFF/SKF_LL_OFF offsets is unsupported.
			 */
			ctx->seen |= SEEN_DATAREF;
			if ((int)K < 0)
				return -ENOTSUPP;
			PPC_LI64(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_S_LD_W_IND:
			func = sk_load_word;
			goto common_load_ind;
		case BPF_S_LD_H_IND:
			func = sk_load_half;
			goto common_load_ind;
		case BPF_S_LD_B_IND:
			func = sk_load_byte;
		common_load_ind:
			/*
			 * Load from [X + K].  Negative offsets are tested for
			 * in the helper functions, and result in a 'ret 0'.
			 */
			ctx->seen |= SEEN_DATAREF | SEEN_XREG;
			PPC_LI64(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_S_LDX_B_MSH:
			/*
			 * x86 version drops packet (RET 0) when K<0, whereas
			 * interpreter does allow K<0 (__load_pointer, special
			 * ancillary data).  common_load returns ENOTSUPP if K<0,
			 * so we fall back to interpreter & filter works.
			 */
			func = sk_load_byte_msh;
			goto common_load;
			break;

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

		case BPF_S_JMP_JGT_K:
		case BPF_S_JMP_JGT_X:
			true_cond = COND_GT;
			goto cond_branch;
		case BPF_S_JMP_JGE_K:
		case BPF_S_JMP_JGE_X:
			true_cond = COND_GE;
			goto cond_branch;
		case BPF_S_JMP_JEQ_K:
		case BPF_S_JMP_JEQ_X:
			true_cond = COND_EQ;
			goto cond_branch;
		case BPF_S_JMP_JSET_K:
		case BPF_S_JMP_JSET_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 (filter[i].code) {
			case BPF_S_JMP_JGT_X:
			case BPF_S_JMP_JGE_X:
			case BPF_S_JMP_JEQ_X:
				ctx->seen |= SEEN_XREG;
				PPC_CMPLW(r_A, r_X);
				break;
			case BPF_S_JMP_JSET_X:
				ctx->seen |= SEEN_XREG;
				PPC_AND_DOT(r_scratch1, r_A, r_X);
				break;
			case BPF_S_JMP_JEQ_K:
			case BPF_S_JMP_JGT_K:
			case BPF_S_JMP_JGE_K:
				if (K < 32768)
					PPC_CMPLWI(r_A, K);
				else {
					PPC_LI32(r_scratch1, K);
					PPC_CMPLW(r_A, r_scratch1);
				}
				break;
			case BPF_S_JMP_JSET_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;
}