static int check_pseudo_btf_id(struct bpf_verifier_env *env,
			       struct bpf_insn *insn,
			       struct bpf_insn_aux_data *aux)
{
	const struct btf_var_secinfo *vsi;
	const struct btf_type *datasec;
	struct btf_mod_pair *btf_mod;
	const struct btf_type *t;
	const char *sym_name;
	bool percpu = false;
	u32 type, id = insn->imm;
	struct btf *btf;
	s32 datasec_id;
	u64 addr;
	int i, btf_fd, err;

	btf_fd = insn[1].imm;
	if (btf_fd) {
		btf = btf_get_by_fd(btf_fd);
		if (IS_ERR(btf)) {
			verbose(env, "invalid module BTF object FD specified.\n");
			return -EINVAL;
		}
	} else {
		if (!btf_vmlinux) {
			verbose(env, "kernel is missing BTF, make sure CONFIG_DEBUG_INFO_BTF=y is specified in Kconfig.\n");
			return -EINVAL;
		}
		btf = btf_vmlinux;
		btf_get(btf);
	}

	t = btf_type_by_id(btf, id);
	if (!t) {
		verbose(env, "ldimm64 insn specifies invalid btf_id %d.\n", id);
		err = -ENOENT;
		goto err_put;
	}

	if (!btf_type_is_var(t)) {
		verbose(env, "pseudo btf_id %d in ldimm64 isn't KIND_VAR.\n", id);
		err = -EINVAL;
		goto err_put;
	}

	sym_name = btf_name_by_offset(btf, t->name_off);
	addr = kallsyms_lookup_name(sym_name);
	if (!addr) {
		verbose(env, "ldimm64 failed to find the address for kernel symbol '%s'.\n",
			sym_name);
		err = -ENOENT;
		goto err_put;
	}

	datasec_id = find_btf_percpu_datasec(btf);
	if (datasec_id > 0) {
		datasec = btf_type_by_id(btf, datasec_id);
		for_each_vsi(i, datasec, vsi) {
			if (vsi->type == id) {
				percpu = true;
				break;
			}
		}
	}

	insn[0].imm = (u32)addr;
	insn[1].imm = addr >> 32;

	type = t->type;
	t = btf_type_skip_modifiers(btf, type, NULL);
	if (percpu) {
		aux->btf_var.reg_type = PTR_TO_PERCPU_BTF_ID;
		aux->btf_var.btf = btf;
		aux->btf_var.btf_id = type;
	} else if (!btf_type_is_struct(t)) {
		const struct btf_type *ret;
		const char *tname;
		u32 tsize;

		/* resolve the type size of ksym. */
		ret = btf_resolve_size(btf, t, &tsize);
		if (IS_ERR(ret)) {
			tname = btf_name_by_offset(btf, t->name_off);
			verbose(env, "ldimm64 unable to resolve the size of type '%s': %ld\n",
				tname, PTR_ERR(ret));
			err = -EINVAL;
			goto err_put;
		}
		aux->btf_var.reg_type = PTR_TO_MEM | MEM_RDONLY;
		aux->btf_var.mem_size = tsize;
	} else {
		aux->btf_var.reg_type = PTR_TO_BTF_ID;
		aux->btf_var.btf = btf;
		aux->btf_var.btf_id = type;
	}

	/* check whether we recorded this BTF (and maybe module) already */
	for (i = 0; i < env->used_btf_cnt; i++) {
		if (env->used_btfs[i].btf == btf) {
			btf_put(btf);
			return 0;
		}
	}

	if (env->used_btf_cnt >= MAX_USED_BTFS) {
		err = -E2BIG;
		goto err_put;
	}

	btf_mod = &env->used_btfs[env->used_btf_cnt];
	btf_mod->btf = btf;
	btf_mod->module = NULL;

	/* if we reference variables from kernel module, bump its refcount */
	if (btf_is_module(btf)) {
		btf_mod->module = btf_try_get_module(btf);
		if (!btf_mod->module) {
			err = -ENXIO;
			goto err_put;
		}
	}

	env->used_btf_cnt++;

	return 0;
err_put:
	btf_put(btf);
	return err;
}