создать файловый дескриптор для обработки ошибок страниц в пользовательском пространстве (create a file descriptor for handling page faults in user space)
Примечание (Note)
The userfaultfd mechanism can be used as an alternative to
traditional user-space paging techniques based on the use of the
SIGSEGV signal and mmap(2). It can also be used to implement
lazy restore for checkpoint/restore mechanisms, as well as post-
copy migration to allow (nearly) uninterrupted execution when
transferring virtual machines and Linux containers from one host
to another.
