static int check_ptr_to_map_access(struct bpf_verifier_env *env,
				   struct bpf_reg_state *regs,
				   int regno, int off, int size,
				   enum bpf_access_type atype,
				   int value_regno)
{
	struct bpf_reg_state *reg = regs + regno;
	struct bpf_map *map = reg->map_ptr;
	const struct btf_type *t;
	const char *tname;
	u32 btf_id;
	int ret;

	if (!btf_vmlinux) {
		verbose(env, "map_ptr access not supported without CONFIG_DEBUG_INFO_BTF\n");
		return -ENOTSUPP;
	}

	if (!map->ops->map_btf_id || !*map->ops->map_btf_id) {
		verbose(env, "map_ptr access not supported for map type %d\n",
			map->map_type);
		return -ENOTSUPP;
	}

	t = btf_type_by_id(btf_vmlinux, *map->ops->map_btf_id);
	tname = btf_name_by_offset(btf_vmlinux, t->name_off);

	if (!env->allow_ptr_to_map_access) {
		verbose(env,
			"%s access is allowed only to CAP_PERFMON and CAP_SYS_ADMIN\n",
			tname);
		return -EPERM;
	}

	if (off < 0) {
		verbose(env, "R%d is %s invalid negative access: off=%d\n",
			regno, tname, off);
		return -EACCES;
	}

	if (atype != BPF_READ) {
		verbose(env, "only read from %s is supported\n", tname);
		return -EACCES;
	}

	ret = btf_struct_access(&env->log, btf_vmlinux, t, off, size, atype, &btf_id);
	if (ret < 0)
		return ret;

	if (value_regno >= 0)
		mark_btf_ld_reg(env, regs, value_regno, ret, btf_vmlinux, btf_id);

	return 0;
}