создать файловый дескриптор для обработки ошибок страниц в пользовательском пространстве (create a file descriptor for handling page faults in user space)
Ошибки (баги) (Bugs)
If the UFFD_FEATURE_EVENT_FORK is enabled and a system call from
the fork(2) family is interrupted by a signal or failed, a stale
userfaultfd descriptor might be created. In this case, a
spurious UFFD_EVENT_FORK will be delivered to the userfaultfd
monitor.
