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: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 101 insertions, 92 deletions

diff --git a/include/linux/filter.h b/include/linux/filter.h
index ed1efab10b8f..4457b383961c 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -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)
 
diff --git a/net/core/filter.c b/net/core/filter.c
index eb020a7d6f55..9aaa05ad8fe3 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -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: