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).

SEE ALSO

       ioctl(2), ioctl_userfaultfd(2), userfaultfd(2)

       linux.git/Documentation/admin-guide/mm/userfaultfd.rst