UFFDIO_COPY(2const) — Linux manual page

UFFDIO_COPY(2const)                                  UFFDIO_COPY(2const)

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

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Linux man-pages 6.9.1          2024-06-17            UFFDIO_COPY(2const)

Pages that refer to this page: ioctl_userfaultfd(2)

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