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.\" Written by Mike Rapoport <rppt@linux.vnet.ibm.com>
.\" Copyright 2016, Michael Kerrisk <mtk.manpages@gmail.com>
.\" Copyright 2024, Alejandro Colomar <alx@kernel.org>
.\"
.\" SPDX-License-Identifier: Linux-man-pages-copyleft
.\"
.TH ioctl_userfaultfd 2 2024-06-14 "Linux man-pages 6.9.1"
.SH NAME
ioctl_userfaultfd \- create a file descriptor for handling page faults in user
space
.SH LIBRARY
Standard C library
.RI ( libc ", " \-lc )
.SH SYNOPSIS
.nf
.BR "#include <linux/userfaultfd.h>" "  /* Definition of " UFFD* " constants */"
.B #include <sys/ioctl.h>
.P
.BI "int ioctl(int " fd ", int " op ", ...);"
.fi
.SH DESCRIPTION
Various
.BR ioctl (2)
operations can be performed on a userfaultfd object (created by a call to
.BR userfaultfd (2))
using calls of the form:
.P
.in +4n
.EX
ioctl(fd, op, argp);
.EE
.in
.P
In the above,
.I fd
is a file descriptor referring to a userfaultfd object,
.I op
is one of the operations listed below, and
.I argp
is a pointer to a data structure that is specific to
.IR op .
.P
The various
.BR ioctl (2)
operations are described below.
The
.BR UFFDIO_API ,
.BR UFFDIO_REGISTER ,
and
.B UFFDIO_UNREGISTER
operations are used to
.I configure
userfaultfd behavior.
These operations allow the caller to choose what features will be enabled and
what kinds of events will be delivered to the application.
The remaining operations are
.I range
operations.
These operations enable the calling application to resolve page-fault
events.
.\"
.TP
.BR UFFDIO_API (2const)
.TQ
.BR UFFDIO_REGISTER (2const)
.TQ
.BR UFFDIO_UNREGISTER (2const)
.TQ
.BR UFFDIO_COPY (2const)
.TQ
.BR UFFDIO_ZEROPAGE (2const)
.TQ
.BR UFFDIO_WAKE (2const)
.TQ
.BR UFFDIO_WRITEPROTECT (2const)
.TQ
.BR UFFDIO_CONTINUE (2const)
.TQ
.BR UFFDIO_POISON (2const)
.SH RETURN VALUE
On success,
0 is returned.
On error,
\-1 is returned, and
.I errno
is set to indicate the error.
.SH ERRORS
The following general errors can occur for all of the
operations described above:
.TP
.B EFAULT
.I argp
does not point to a valid memory address.
.TP
.B EINVAL
(For all operations except
.BR UFFDIO_API .)
The userfaultfd object has not yet been enabled (via the
.B UFFDIO_API
operation).
.SH STANDARDS
Linux.
.SH EXAMPLES
See
.BR userfaultfd (2).
.SH SEE ALSO
.BR ioctl (2),
.BR mmap (2),
.BR userfaultfd (2)
.P
.I linux.git/\:Documentation/\:admin\-guide/\:mm/\:userfaultfd.rst