UFFDIO_REGISTER(2const) UFFDIO_REGISTER(2const)
NAME
UFFDIO_REGISTER - register a memory address range with the userfaultfd
object
LIBRARY
Standard C library (libc, -lc)
SYNOPSIS
#include <linux/userfaultfd.h> /* Definition of UFFD* constants */
#include <sys/ioctl.h>
int ioctl(int fd, UFFDIO_REGISTER, struct uffdio_register *argp);
#include <linux/userfaultfd.h>
struct uffdio_range {
__u64 start; /* Start of range */
__u64 len; /* Length of range (bytes) */
};
struct uffdio_register {
struct uffdio_range range;
__u64 mode; /* Desired mode of operation (input) */
__u64 ioctls; /* Available ioctl()s (output) */
};
DESCRIPTION
Register a memory address range with the userfaultfd object. The pages
in the range must be “compatible”. Please refer to the list of register
modes below for the compatible memory backends for each mode.
The argp->range field defines a memory range starting at
argp->range.start and continuing for argp->range.len bytes that should
be handled by the userfaultfd.
The argp->mode field defines the mode of operation desired for this mem-
ory region. The following values may be bitwise ORed to set the user-
faultfd mode for the specified range:
UFFDIO_REGISTER_MODE_MISSING
Track page faults on missing pages. Since Linux 4.3, only pri-
vate anonymous ranges are compatible. Since Linux 4.11,
hugetlbfs and shared memory ranges are also compatible.
UFFDIO_REGISTER_MODE_WP
Track page faults on write-protected pages. Since Linux 5.7,
only private anonymous ranges are compatible.
UFFDIO_REGISTER_MODE_MINOR
Track minor page faults. Since Linux 5.13, only hugetlbfs ranges
are compatible. Since Linux 5.14, compatibility with shmem
ranges was added.
If the operation is successful, the kernel modifies the argp->ioctls
bit-mask field to indicate which ioctl(2) operations are available for
the specified range. This returned bit mask can contain the following
bits:
1 << _UFFDIO_COPY
The UFFDIO_COPY operation is supported.
1 << _UFFDIO_WAKE
The UFFDIO_WAKE operation is supported.
1 << _UFFDIO_WRITEPROTECT
The UFFDIO_WRITEPROTECT operation is supported.
1 << _UFFDIO_ZEROPAGE
The UFFDIO_ZEROPAGE operation is supported.
1 << _UFFDIO_CONTINUE
The UFFDIO_CONTINUE operation is supported.
1 << _UFFDIO_POISON
The UFFDIO_POISON operation is supported.
RETURN VALUE
On success, 0 is returned. On error, -1 is returned and errno is set to
indicate the error.
ERRORS
EBUSY A mapping in the specified range is registered with another user-
faultfd object.
EFAULT argp refers to an address that is outside the calling process's
accessible address space.
EINVAL An invalid or unsupported bit was specified in the mode field; or
the mode field was zero.
EINVAL There is no mapping in the specified address range.
EINVAL range.start or range.len is not a multiple of the system page
size; or, range.len is zero; or these fields are otherwise in-
valid.
EINVAL There as an incompatible mapping in the specified address range.
STANDARDS
Linux.
HISTORY
Linux 4.3.
EXAMPLES
See userfaultfd(2).
SEE ALSO
ioctl(2), ioctl_userfaultfd(2), UFFDIO_UNREGISTER(2const), user-
faultfd(2)
linux.git/Documentation/admin-guide/mm/userfaultfd.rst
Linux man-pages 6.9.1 2024-06-17 UFFDIO_REGISTER(2const)
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