UFFDIO_ZEROPAGE2const

Usage

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

struct uffdio_zeropage {
    struct uffdio_range  range;
    __u64                mode;      /* Flags controlling behavior */
    __s64                zeropage;  /* Number of bytes zeroed */
};

Library

Standard C library (libc, -lc)

Overview

Zero out a memory range registered with userfaultfd.

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

UFFDIO_ZEROPAGE_MODE_DONTWAKE

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

The zeropage field is used by the kernel to return the number of bytes that was actually zeroed, or an error in the same manner as UFFDIO_COPY. If the value returned in the zeropage field doesn't match the value that was specified in range.len, the operation fails with the error EAGAIN. The zeropage field is output-only; it is not read by the UFFDIO_ZEROPAGE operation.

Return value

This ioctl(2) operation returns 0 on success. In this case, the entire area was zeroed. On error, -1 is returned and errno is set to indicate the error.

Errors

EAGAIN

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

EINVAL

Either range.start or range.len was not a multiple of the system page size; or range.len was zero; or the range specified was invalid.

EINVAL

An invalid bit was specified in the mode field.

ESRCH (since Linux 4.13)

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

Examples

See userfaultfd(2).