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