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net: filter: make BPF conversion more readable

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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: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Alexei Starovoitov 2014-05-08 14:10:51 -07:00 committed by David S. Miller
parent 05ab2dae65
commit 9739eef13c
2 changed files with 101 additions and 92 deletions
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51
include/linux/filter.h
View File

@ -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)

142
net/core/filter.c
View File

@ -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: