UFFDIO_WRITEPROTECT(2const)                        UFFDIO_WRITEPROTECT(2const)

NAME
       UFFDIO_WRITEPROTECT - write-protect or write-unprotect a userfaultfd-
       registered memory 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_WRITEPROTECT, ...);

       #include <linux/userfaultfd.h>

       struct uffdio_writeprotect {
           struct uffdio_range  range;  /* Range to change write permission*/
           __u64                mode;   /* Mode to change write permission */
       };

DESCRIPTION
       Write-protect or write-unprotect a userfaultfd-registered memory range
       registered with mode UFFDIO_REGISTER_MODE_WP.

       There are two mode bits that are supported in this structure:

       UFFDIO_WRITEPROTECT_MODE_WP
              When this mode bit is set, the ioctl will be a write-protect
              operation upon the memory range specified by range.  Otherwise
              it will be a write-unprotect operation upon the specified range,
              which can be used to resolve a userfaultfd write-protect page
              fault.

       UFFDIO_WRITEPROTECT_MODE_DONTWAKE
              When this mode bit is set, do not wake up any thread that waits
              for page-fault resolution after the operation.  This can be
              specified only if UFFDIO_WRITEPROTECT_MODE_WP is not specified.

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

ERRORS
       EINVAL The start or the len field of the ufdio_range structure was not
              a multiple of the system page size; or len was zero; or the
              specified range was otherwise invalid.

       EAGAIN The process was interrupted; retry this call.

       ENOENT The range specified in range is not valid.  For example, the
              virtual address does not exist, or not registered with
              userfaultfd write-protect mode.

       EFAULT Encountered a generic fault during processing.

STANDARDS
       Linux.

HISTORY
       Linux 5.7.

EXAMPLES
       See userfaultfd(2).

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

       Documentation/admin-guide/mm/userfaultfd.rst in the Linux kernel source
       tree

Linux man-pages 6.19              2026-02-08       UFFDIO_WRITEPROTECT(2const)