- if (seen_ld_abs) {
- /* r9d : skb->len - skb->data_len (headlen)
- * r10 : skb->data
- */
- if (is_imm8(offsetof(struct sk_buff, len)))
- /* mov %r9d, off8(%rdi) */
- EMIT4(0x44, 0x8b, 0x4f,
- offsetof(struct sk_buff, len));
- else
- /* mov %r9d, off32(%rdi) */
- EMIT3_off32(0x44, 0x8b, 0x8f,
- offsetof(struct sk_buff, len));
-
- if (is_imm8(offsetof(struct sk_buff, data_len)))
- /* sub %r9d, off8(%rdi) */
- EMIT4(0x44, 0x2b, 0x4f,
- offsetof(struct sk_buff, data_len));
- else
- EMIT3_off32(0x44, 0x2b, 0x8f,
- offsetof(struct sk_buff, data_len));
-
- if (is_imm8(offsetof(struct sk_buff, data)))
- /* mov %r10, off8(%rdi) */
- EMIT4(0x4c, 0x8b, 0x57,
- offsetof(struct sk_buff, data));
- else
- /* mov %r10, off32(%rdi) */
- EMIT3_off32(0x4c, 0x8b, 0x97,
- offsetof(struct sk_buff, data));
- }
+ /* clear tail_cnt: mov qword ptr [rbp-X], rax */
+ EMIT3_off32(0x48, 0x89, 0x85, -STACKSIZE + 32);
+
+ BUILD_BUG_ON(cnt != PROLOGUE_SIZE);
+ *pprog = prog;
+}
+
+/* generate the following code:
+ * ... bpf_tail_call(void *ctx, struct bpf_array *array, u64 index) ...
+ * if (index >= array->map.max_entries)
+ * goto out;
+ * if (++tail_call_cnt > MAX_TAIL_CALL_CNT)
+ * goto out;
+ * prog = array->ptrs[index];
+ * if (prog == NULL)
+ * goto out;
+ * goto *(prog->bpf_func + prologue_size);
+ * out:
+ */
+static void emit_bpf_tail_call(u8 **pprog)
+{
+ u8 *prog = *pprog;
+ int label1, label2, label3;
+ int cnt = 0;
+
+ /* rdi - pointer to ctx
+ * rsi - pointer to bpf_array
+ * rdx - index in bpf_array
+ */
+
+ /* if (index >= array->map.max_entries)
+ * goto out;
+ */
+ EMIT4(0x48, 0x8B, 0x46, /* mov rax, qword ptr [rsi + 16] */
+ offsetof(struct bpf_array, map.max_entries));
+ EMIT3(0x48, 0x39, 0xD0); /* cmp rax, rdx */
+#define OFFSET1 47 /* number of bytes to jump */
+ EMIT2(X86_JBE, OFFSET1); /* jbe out */
+ label1 = cnt;
+
+ /* if (tail_call_cnt > MAX_TAIL_CALL_CNT)
+ * goto out;
+ */
+ EMIT2_off32(0x8B, 0x85, -STACKSIZE + 36); /* mov eax, dword ptr [rbp - 516] */
+ EMIT3(0x83, 0xF8, MAX_TAIL_CALL_CNT); /* cmp eax, MAX_TAIL_CALL_CNT */
+#define OFFSET2 36
+ EMIT2(X86_JA, OFFSET2); /* ja out */
+ label2 = cnt;
+ EMIT3(0x83, 0xC0, 0x01); /* add eax, 1 */
+ EMIT2_off32(0x89, 0x85, -STACKSIZE + 36); /* mov dword ptr [rbp - 516], eax */
+
+ /* prog = array->ptrs[index]; */
+ EMIT4_off32(0x48, 0x8D, 0x84, 0xD6, /* lea rax, [rsi + rdx * 8 + offsetof(...)] */
+ offsetof(struct bpf_array, ptrs));
+ EMIT3(0x48, 0x8B, 0x00); /* mov rax, qword ptr [rax] */
+
+ /* if (prog == NULL)
+ * goto out;
+ */
+ EMIT4(0x48, 0x83, 0xF8, 0x00); /* cmp rax, 0 */
+#define OFFSET3 10
+ EMIT2(X86_JE, OFFSET3); /* je out */
+ label3 = cnt;
+
+ /* goto *(prog->bpf_func + prologue_size); */
+ EMIT4(0x48, 0x8B, 0x40, /* mov rax, qword ptr [rax + 32] */
+ offsetof(struct bpf_prog, bpf_func));
+ EMIT4(0x48, 0x83, 0xC0, PROLOGUE_SIZE); /* add rax, prologue_size */
+
+ /* now we're ready to jump into next BPF program
+ * rdi == ctx (1st arg)
+ * rax == prog->bpf_func + prologue_size
+ */
+ EMIT2(0xFF, 0xE0); /* jmp rax */
+
+ /* out: */
+ BUILD_BUG_ON(cnt - label1 != OFFSET1);
+ BUILD_BUG_ON(cnt - label2 != OFFSET2);
+ BUILD_BUG_ON(cnt - label3 != OFFSET3);
+ *pprog = prog;
+}
+
+
+static void emit_load_skb_data_hlen(u8 **pprog)
+{
+ u8 *prog = *pprog;
+ int cnt = 0;
+
+ /* r9d = skb->len - skb->data_len (headlen)
+ * r10 = skb->data
+ */
+ /* mov %r9d, off32(%rdi) */
+ EMIT3_off32(0x44, 0x8b, 0x8f, offsetof(struct sk_buff, len));
+
+ /* sub %r9d, off32(%rdi) */
+ EMIT3_off32(0x44, 0x2b, 0x8f, offsetof(struct sk_buff, data_len));
+
+ /* mov %r10, off32(%rdi) */
+ EMIT3_off32(0x4c, 0x8b, 0x97, offsetof(struct sk_buff, data));
+ *pprog = prog;
+}
+
+static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
+ int oldproglen, struct jit_context *ctx)
+{
+ struct bpf_insn *insn = bpf_prog->insnsi;
+ int insn_cnt = bpf_prog->len;
+ bool seen_ld_abs = ctx->seen_ld_abs | (oldproglen == 0);
+ bool seen_exit = false;
+ u8 temp[BPF_MAX_INSN_SIZE + BPF_INSN_SAFETY];
+ int i, cnt = 0;
+ int proglen = 0;
+ u8 *prog = temp;
+
+ emit_prologue(&prog);
+
+ if (seen_ld_abs)
+ emit_load_skb_data_hlen(&prog);