UFFDIO_ZEROPAGE(2const)

NAME

UFFDIO_ZEROPAGE - zero out a memory range registered with userfaultfd

LIBRARY

Standard C library (libc, -lc)

SYNOPSIS

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

int ioctl(int fd, UFFDIO_ZEROPAGE, struct uffdio_zeropage *argp);

#include <linux/userfaultfd.h>

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

DESCRIPTION

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.

STANDARDS

Linux.

HISTORY

Linux 4.3.

EXAMPLES

See userfaultfd(2).