Commit 9739eef1 authored by Alexei Starovoitov's avatar Alexei Starovoitov Committed by David S. Miller
Browse files

net: filter: make BPF conversion more readable 



Introduce BPF helper macros to define instructions
(similar to old BPF_STMT/BPF_JUMP macros)

Use them while converting classic BPF to internal
and in BPF testsuite later.

Signed-off-by: default avatarAlexei Starovoitov <ast@plumgrid.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 05ab2dae

include/linux/filter.h

+51 −0
Original line number Diff line number Diff line
@@ -79,6 +79,57 @@ enum { 
/* BPF program can access up to 512 bytes of stack space. */

#define MAX_BPF_STACK	512



/* bpf_add|sub|...: a += x, bpf_mov: a = x */

#define BPF_ALU64_REG(op, a, x) \

	((struct sock_filter_int) {BPF_ALU64|BPF_OP(op)|BPF_X, a, x, 0, 0})

#define BPF_ALU32_REG(op, a, x) \

	((struct sock_filter_int) {BPF_ALU|BPF_OP(op)|BPF_X, a, x, 0, 0})



/* bpf_add|sub|...: a += imm, bpf_mov: a = imm */

#define BPF_ALU64_IMM(op, a, imm) \

	((struct sock_filter_int) {BPF_ALU64|BPF_OP(op)|BPF_K, a, 0, 0, imm})

#define BPF_ALU32_IMM(op, a, imm) \

	((struct sock_filter_int) {BPF_ALU|BPF_OP(op)|BPF_K, a, 0, 0, imm})



/* R0 = *(uint *) (skb->data + off) */

#define BPF_LD_ABS(size, off) \

	((struct sock_filter_int) {BPF_LD|BPF_SIZE(size)|BPF_ABS, 0, 0, 0, off})



/* R0 = *(uint *) (skb->data + x + off) */

#define BPF_LD_IND(size, x, off) \

	((struct sock_filter_int) {BPF_LD|BPF_SIZE(size)|BPF_IND, 0, x, 0, off})



/* a = *(uint *) (x + off) */

#define BPF_LDX_MEM(sz, a, x, off) \

	((struct sock_filter_int) {BPF_LDX|BPF_SIZE(sz)|BPF_MEM, a, x, off, 0})



/* if (a 'op' x) goto pc+off */

#define BPF_JMP_REG(op, a, x, off) \

	((struct sock_filter_int) {BPF_JMP|BPF_OP(op)|BPF_X, a, x, off, 0})



/* if (a 'op' imm) goto pc+off */

#define BPF_JMP_IMM(op, a, imm, off) \

	((struct sock_filter_int) {BPF_JMP|BPF_OP(op)|BPF_K, a, 0, off, imm})



#define BPF_EXIT_INSN() \

	((struct sock_filter_int) {BPF_JMP|BPF_EXIT, 0, 0, 0, 0})



static inline int size_to_bpf(int size)

{

	switch (size) {

	case 1:

		return BPF_B;

	case 2:

		return BPF_H;

	case 4:

		return BPF_W;

	case 8:

		return BPF_DW;

	default:

		return -EINVAL;

	}

}



/* Macro to invoke filter function. */

#define SK_RUN_FILTER(filter, ctx)  (*filter->bpf_func)(ctx, filter->insnsi)

net/core/filter.c

+50 −92
Original line number Diff line number Diff line
@@ -668,10 +668,9 @@ static bool convert_bpf_extensions(struct sock_filter *fp, 
	case SKF_AD_OFF + SKF_AD_PROTOCOL:

		BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, protocol) != 2);



		insn->code = BPF_LDX | BPF_MEM | BPF_H;

		insn->a_reg = BPF_REG_A;

		insn->x_reg = BPF_REG_CTX;

		insn->off = offsetof(struct sk_buff, protocol);

		/* A = *(u16 *) (ctx + offsetof(protocol)) */

		*insn = BPF_LDX_MEM(BPF_H, BPF_REG_A, BPF_REG_CTX,

				    offsetof(struct sk_buff, protocol));

		insn++;



		/* A = ntohs(A) [emitting a nop or swap16] */
@@ -681,37 +680,27 @@ static bool convert_bpf_extensions(struct sock_filter *fp, 
		break;



	case SKF_AD_OFF + SKF_AD_PKTTYPE:

		insn->code = BPF_LDX | BPF_MEM | BPF_B;

		insn->a_reg = BPF_REG_A;

		insn->x_reg = BPF_REG_CTX;

		insn->off = pkt_type_offset();

		*insn = BPF_LDX_MEM(BPF_B, BPF_REG_A, BPF_REG_CTX,

				    pkt_type_offset());

		if (insn->off < 0)

			return false;

		insn++;



		insn->code = BPF_ALU | BPF_AND | BPF_K;

		insn->a_reg = BPF_REG_A;

		insn->imm = PKT_TYPE_MAX;

		*insn = BPF_ALU32_IMM(BPF_AND, BPF_REG_A, PKT_TYPE_MAX);

		break;



	case SKF_AD_OFF + SKF_AD_IFINDEX:

	case SKF_AD_OFF + SKF_AD_HATYPE:

		if (FIELD_SIZEOF(struct sk_buff, dev) == 8)

			insn->code = BPF_LDX | BPF_MEM | BPF_DW;

		else

			insn->code = BPF_LDX | BPF_MEM | BPF_W;

		insn->a_reg = BPF_REG_TMP;

		insn->x_reg = BPF_REG_CTX;

		insn->off = offsetof(struct sk_buff, dev);

		*insn = BPF_LDX_MEM(size_to_bpf(FIELD_SIZEOF(struct sk_buff, dev)),

				    BPF_REG_TMP, BPF_REG_CTX,

				    offsetof(struct sk_buff, dev));

		insn++;



		insn->code = BPF_JMP | BPF_JNE | BPF_K;

		insn->a_reg = BPF_REG_TMP;

		insn->imm = 0;

		insn->off = 1;

		/* if (tmp != 0) goto pc+1 */

		*insn = BPF_JMP_IMM(BPF_JNE, BPF_REG_TMP, 0, 1);

		insn++;



		insn->code = BPF_JMP | BPF_EXIT;

		*insn = BPF_EXIT_INSN();

		insn++;



		BUILD_BUG_ON(FIELD_SIZEOF(struct net_device, ifindex) != 4);
@@ -732,55 +721,45 @@ static bool convert_bpf_extensions(struct sock_filter *fp, 
	case SKF_AD_OFF + SKF_AD_MARK:

		BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, mark) != 4);



		insn->code = BPF_LDX | BPF_MEM | BPF_W;

		insn->a_reg = BPF_REG_A;

		insn->x_reg = BPF_REG_CTX;

		insn->off = offsetof(struct sk_buff, mark);

		*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->code = BPF_LDX | BPF_MEM | BPF_W;

		insn->a_reg = BPF_REG_A;

		insn->x_reg = BPF_REG_CTX;

		insn->off = offsetof(struct sk_buff, hash);

		*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->code = BPF_LDX | BPF_MEM | BPF_H;

		insn->a_reg = BPF_REG_A;

		insn->x_reg = BPF_REG_CTX;

		insn->off = offsetof(struct sk_buff, queue_mapping);

		*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);



		insn->code = BPF_LDX | BPF_MEM | BPF_H;

		insn->a_reg = BPF_REG_A;

		insn->x_reg = BPF_REG_CTX;

		insn->off = offsetof(struct sk_buff, vlan_tci);

		/* A = *(u16 *) (ctx + offsetof(vlan_tci)) */

		*insn = BPF_LDX_MEM(BPF_H, BPF_REG_A, BPF_REG_CTX,

				    offsetof(struct sk_buff, vlan_tci));

		insn++;



		BUILD_BUG_ON(VLAN_TAG_PRESENT != 0x1000);



		if (fp->k == SKF_AD_OFF + SKF_AD_VLAN_TAG) {

			insn->code = BPF_ALU | BPF_AND | BPF_K;

			insn->a_reg = BPF_REG_A;

			insn->imm = ~VLAN_TAG_PRESENT;

			*insn = BPF_ALU32_IMM(BPF_AND, BPF_REG_A,

					      ~VLAN_TAG_PRESENT);

		} else {

			insn->code = BPF_ALU | BPF_RSH | BPF_K;

			insn->a_reg = BPF_REG_A;

			insn->imm = 12;

			/* A >>= 12 */

			*insn = BPF_ALU32_IMM(BPF_RSH, BPF_REG_A, 12);

			insn++;



			insn->code = BPF_ALU | BPF_AND | BPF_K;

			insn->a_reg = BPF_REG_A;

			insn->imm = 1;

			/* A &= 1 */

			*insn = BPF_ALU32_IMM(BPF_AND, BPF_REG_A, 1);

		}

		break;
@@ -790,21 +769,15 @@ static bool convert_bpf_extensions(struct sock_filter *fp, 
	case SKF_AD_OFF + SKF_AD_CPU:

	case SKF_AD_OFF + SKF_AD_RANDOM:

		/* arg1 = ctx */

		insn->code = BPF_ALU64 | BPF_MOV | BPF_X;

		insn->a_reg = BPF_REG_ARG1;

		insn->x_reg = BPF_REG_CTX;

		*insn = BPF_ALU64_REG(BPF_MOV, BPF_REG_ARG1, BPF_REG_CTX);

		insn++;



		/* arg2 = A */

		insn->code = BPF_ALU64 | BPF_MOV | BPF_X;

		insn->a_reg = BPF_REG_ARG2;

		insn->x_reg = BPF_REG_A;

		*insn = BPF_ALU64_REG(BPF_MOV, BPF_REG_ARG2, BPF_REG_A);

		insn++;



		/* arg3 = X */

		insn->code = BPF_ALU64 | BPF_MOV | BPF_X;

		insn->a_reg = BPF_REG_ARG3;

		insn->x_reg = BPF_REG_X;

		*insn = BPF_ALU64_REG(BPF_MOV, BPF_REG_ARG3, BPF_REG_X);

		insn++;



		/* Emit call(ctx, arg2=A, arg3=X) */
@@ -829,9 +802,8 @@ static bool convert_bpf_extensions(struct sock_filter *fp, 
		break;



	case SKF_AD_OFF + SKF_AD_ALU_XOR_X:

		insn->code = BPF_ALU | BPF_XOR | BPF_X;

		insn->a_reg = BPF_REG_A;

		insn->x_reg = BPF_REG_X;

		/* A ^= X */

		*insn = BPF_ALU32_REG(BPF_XOR, BPF_REG_A, BPF_REG_X);

		break;



	default:
@@ -897,9 +869,7 @@ do_pass: 
	fp = prog;



	if (new_insn) {

		new_insn->code = BPF_ALU64 | BPF_MOV | BPF_X;

		new_insn->a_reg = BPF_REG_CTX;

		new_insn->x_reg = BPF_REG_ARG1;

		*new_insn = BPF_ALU64_REG(BPF_MOV, BPF_REG_CTX, BPF_REG_ARG1);

	}

	new_insn++;
@@ -1027,34 +997,28 @@ do_pass: 


		/* ldxb 4 * ([14] & 0xf) is remaped into 6 insns. */

		case BPF_LDX | BPF_MSH | BPF_B:

			insn->code = BPF_ALU64 | BPF_MOV | BPF_X;

			insn->a_reg = BPF_REG_TMP;

			insn->x_reg = BPF_REG_A;

			/* tmp = A */

			*insn = BPF_ALU64_REG(BPF_MOV, BPF_REG_TMP, BPF_REG_A);

			insn++;



			insn->code = BPF_LD | BPF_ABS | BPF_B;

			insn->a_reg = BPF_REG_A;

			insn->imm = fp->k;

			/* A = R0 = *(u8 *) (skb->data + K) */

			*insn = BPF_LD_ABS(BPF_B, fp->k);

			insn++;



			insn->code = BPF_ALU | BPF_AND | BPF_K;

			insn->a_reg = BPF_REG_A;

			insn->imm = 0xf;

			/* A &= 0xf */

			*insn = BPF_ALU32_IMM(BPF_AND, BPF_REG_A, 0xf);

			insn++;



			insn->code = BPF_ALU | BPF_LSH | BPF_K;

			insn->a_reg = BPF_REG_A;

			insn->imm = 2;

			/* A <<= 2 */

			*insn = BPF_ALU32_IMM(BPF_LSH, BPF_REG_A, 2);

			insn++;



			insn->code = BPF_ALU64 | BPF_MOV | BPF_X;

			insn->a_reg = BPF_REG_X;

			insn->x_reg = BPF_REG_A;

			/* X = A */

			*insn = BPF_ALU64_REG(BPF_MOV, BPF_REG_X, BPF_REG_A);

			insn++;



			insn->code = BPF_ALU64 | BPF_MOV | BPF_X;

			insn->a_reg = BPF_REG_A;

			insn->x_reg = BPF_REG_TMP;

			/* A = tmp */

			*insn = BPF_ALU64_REG(BPF_MOV, BPF_REG_A, BPF_REG_TMP);

			break;



		/* RET_K, RET_A are remaped into 2 insns. */
@@ -1068,7 +1032,7 @@ do_pass: 
			insn->imm = fp->k;

			insn++;



			insn->code = BPF_JMP | BPF_EXIT;

			*insn = BPF_EXIT_INSN();

			break;



		/* Store to stack. */
@@ -1102,16 +1066,12 @@ do_pass: 


		/* X = A */

		case BPF_MISC | BPF_TAX:

			insn->code = BPF_ALU64 | BPF_MOV | BPF_X;

			insn->a_reg = BPF_REG_X;

			insn->x_reg = BPF_REG_A;

			*insn = BPF_ALU64_REG(BPF_MOV, BPF_REG_X, BPF_REG_A);

			break;



		/* A = X */

		case BPF_MISC | BPF_TXA:

			insn->code = BPF_ALU64 | BPF_MOV | BPF_X;

			insn->a_reg = BPF_REG_A;

			insn->x_reg = BPF_REG_X;

			*insn = BPF_ALU64_REG(BPF_MOV, BPF_REG_A, BPF_REG_X);

			break;



		/* A = skb->len or X = skb->len */
@@ -1126,10 +1086,8 @@ do_pass: 


		/* access seccomp_data fields */

		case BPF_LDX | BPF_ABS | BPF_W:

			insn->code = BPF_LDX | BPF_MEM | BPF_W;

			insn->a_reg = BPF_REG_A;

			insn->x_reg = BPF_REG_CTX;

			insn->off = fp->k;

			/* A = *(u32 *) (ctx + K) */

			*insn = BPF_LDX_MEM(BPF_W, BPF_REG_A, BPF_REG_CTX, fp->k);

			break;



		default:

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