NAME

UFFDIO_COPY - atomically copy a continuous memory chunk into the userfault registered range

LIBRARY

Standard C library (libc, -lc)

SYNOPSIS

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

int ioctl(int fd, UFFDIO_COPY, struct uffdio_copy *argp);

#include <linux/userfaultfd.h>

struct uffdio_copy {
    __u64  dst;   /* Destination of copy */
    __u64  src;   /* Source of copy */
    __u64  len;   /* Number of bytes to copy */
    __u64  mode;  /* Flags controlling behavior of copy */
    __s64  copy;  /* Number of bytes copied, or negated error */
};

DESCRIPTION

Atomically copy a continuous memory chunk into the userfault registered range and optionally wake up the blocked thread.

The following value may be bitwise ORed in mode to change the behavior of the UFFDIO_COPY operation:

UFFDIO_COPY_MODE_DONTWAKE

Do not wake up the thread that waits for page-fault resolution

UFFDIO_COPY_MODE_WP

Copy the page with read-only permission. This allows the user to trap the next write to the page, which will block and generate another write-protect userfault message. This is used only when both UFFDIO_REGISTER_MODE_MISSING and UFFDIO_REGISTER_MODE_WP modes are enabled for the registered range.

The copy field is used by the kernel to return the number of bytes that was actually copied, or an error (a negated errno-style value). The copy field is output-only; it is not read by the UFFDIO_COPY operation.

RETURN VALUE

On success, 0 is returned. In this case, the entire area was copied.

On error, -1 is returned and errno is set to indicate the error.

ERRORS

EAGAIN

The number of bytes copied (i.e., the value returned in the copy field) does not equal the value that was specified in the len field.

EINVAL

Either dst or len was not a multiple of the system page size, or the range specified by src and len or dst and len was invalid.

EINVAL

An invalid bit was specified in the mode field.

ENOENT (since Linux 4.11)

The faulting process has changed its virtual memory layout simultaneously with an outstanding UFFDIO_COPY operation.

ENOSPC (from Linux 4.11 until Linux 4.13)

The faulting process has exited at the time of a UFFDIO_COPY operation.

ESRCH (since Linux 4.13)

The faulting process has exited at the time of a UFFDIO_COPY operation.

STANDARDS

Linux.

HISTORY

Linux 4.3.

EXAMPLES

See userfaultfd(2).

SEE ALSO

ioctl(2), ioctl_userfaultfd(2), userfaultfd(2)

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