#include<linux/userfaultfd.h>#ifndef UFFD_USER_MODE_ONLY
// this definition is not available before Linux 5.11. It is provided so
// userfaultfd-sys has the same exports on all kernels
#defineUFFD_USER_MODE_ONLY1#endif#ifndef USERFAULTFD_IOC
// Similarly, the ioctl() for `/dev/userfaultfd` is introduced with Linux 6.1.
#defineUSERFAULTFD_IOC0xAA#endif