ioctl_userfaultfd(2)	       System Calls Manual	    ioctl_userfaultfd(2)

NAME
     ioctl_userfaultfd	-  create  a file descriptor for handling page faults in
     user space

LIBRARY
     Standard C library (libc, -lc)

SYNOPSIS
     #include <linux/userfaultfd.h>  /* Definition of UFFD* constants */
     #include <sys/ioctl.h>

     int ioctl(int fd, int op, ...);

DESCRIPTION
     Various ioctl(2) operations can be performed on a userfaultfd object  (cre-
     ated by a call to userfaultfd(2)) using calls of the form:

	 ioctl(fd, op, argp);

     In the above, fd is a file descriptor referring to a userfaultfd object, op
     is	 one  of  the  operations  listed below, and argp is a pointer to a data
     structure that is specific to op.

     The various ioctl(2) operations are described below.  The UFFDIO_API,  UFF-
     DIO_REGISTER,  and UFFDIO_UNREGISTER operations are used to configure user-
     faultfd behavior.	These operations allow the caller to  choose  what  fea-
     tures will be enabled and what kinds of events will be delivered to the ap-
     plication.	  The  remaining  operations are range operations.  These opera-
     tions enable the calling application to resolve page-fault events.

     UFFDIO_API(2const)
     UFFDIO_REGISTER(2const)
     UFFDIO_UNREGISTER(2const)
     UFFDIO_COPY(2const)
     UFFDIO_MOVE(2const)
     UFFDIO_ZEROPAGE(2const)
     UFFDIO_WAKE(2const)
     UFFDIO_WRITEPROTECT(2const)
     UFFDIO_CONTINUE(2const)
     UFFDIO_POISON(2const)

RETURN VALUE
     On success, 0 is returned.	 On error, -1 is returned, and errno is	 set  to
     indicate the error.

ERRORS
     The  following general errors can occur for all of the operations described
     above:

     EFAULT
	    argp does not point to a valid memory address.

     EINVAL
	    (For all operations except UFFDIO_API.)  The userfaultfd object  has
	    not yet been enabled (via the UFFDIO_API operation).

STANDARDS
     Linux.

EXAMPLES
     See userfaultfd(2).

SEE ALSO
     ioctl(2), mmap(2), userfaultfd(2)

     linux.git/Documentation/admin-guide/mm/userfaultfd.rst

Linux man-pages 6.18		   2026-02-08		    ioctl_userfaultfd(2)