return 0;
}
+/* fixup insn->imm field of bpf_call instructions
+ * and inline eligible helpers as explicit sequence of BPF instructions
+ *
+ * this function is called after eBPF program passed verification
+ */
+static int fixup_bpf_calls(struct bpf_verifier_env *env)
+{
+ struct bpf_prog *prog = env->prog;
+ struct bpf_insn *insn = prog->insnsi;
+ const struct bpf_func_proto *fn;
+ const int insn_cnt = prog->len;
+ struct bpf_insn insn_buf[16];
+ struct bpf_prog *new_prog;
+ struct bpf_map *map_ptr;
+ int i, cnt, delta = 0;
+
+ for (i = 0; i < insn_cnt; i++, insn++) {
+ if (insn->code != (BPF_JMP | BPF_CALL))
+ continue;
+
+ if (insn->imm == BPF_FUNC_get_route_realm)
+ prog->dst_needed = 1;
+ if (insn->imm == BPF_FUNC_get_prandom_u32)
+ bpf_user_rnd_init_once();
+ if (insn->imm == BPF_FUNC_xdp_adjust_head)
+ prog->xdp_adjust_head = 1;
+ if (insn->imm == BPF_FUNC_tail_call) {
++ /* If we tail call into other programs, we
++ * cannot make any assumptions since they can
++ * be replaced dynamically during runtime in
++ * the program array.
++ */
++ prog->cb_access = 1;
++ prog->xdp_adjust_head = 1;
++
+ /* mark bpf_tail_call as different opcode to avoid
+ * conditional branch in the interpeter for every normal
+ * call and to prevent accidental JITing by JIT compiler
+ * that doesn't support bpf_tail_call yet
+ */
+ insn->imm = 0;
+ insn->code |= BPF_X;
+ continue;
+ }
+
+ if (ebpf_jit_enabled() && insn->imm == BPF_FUNC_map_lookup_elem) {
+ map_ptr = env->insn_aux_data[i + delta].map_ptr;
+ if (map_ptr == BPF_MAP_PTR_POISON ||
+ !map_ptr->ops->map_gen_lookup)
+ goto patch_call_imm;
+
+ cnt = map_ptr->ops->map_gen_lookup(map_ptr, insn_buf);
+ if (cnt == 0 || cnt >= ARRAY_SIZE(insn_buf)) {
+ verbose("bpf verifier is misconfigured\n");
+ return -EINVAL;
+ }
+
+ new_prog = bpf_patch_insn_data(env, i + delta, insn_buf,
+ cnt);
+ if (!new_prog)
+ return -ENOMEM;
+
+ delta += cnt - 1;
+
+ /* keep walking new program and skip insns we just inserted */
+ env->prog = prog = new_prog;
+ insn = new_prog->insnsi + i + delta;
+ continue;
+ }
+
+patch_call_imm:
+ fn = prog->aux->ops->get_func_proto(insn->imm);
+ /* all functions that have prototype and verifier allowed
+ * programs to call them, must be real in-kernel functions
+ */
+ if (!fn->func) {
+ verbose("kernel subsystem misconfigured func %s#%d\n",
+ func_id_name(insn->imm), insn->imm);
+ return -EFAULT;
+ }
+ insn->imm = fn->func - __bpf_call_base;
+ }
+
+ return 0;
+}
+
static void free_states(struct bpf_verifier_env *env)
{
struct bpf_verifier_state_list *sl, *sln;