UIOMOVE(9)

UIOMOVE(9) | Kernel Developer's Manual | UIOMOVE(9)

# NAME

`uiomove` —
move data described by a struct uio

# SYNOPSIS

`#include <sys/systm.h>`

int
`uiomove`(void *buf, size_t n, struct uio *uio);

# DESCRIPTION

The `uiomove`() function copies up to n bytes between the kernel-space address pointed to by buf and the addresses described by uio, which may be in user-space or kernel-space.

The uio argument is a pointer to a struct uio as defined by `<sys/uio.h>`:

    struct uio {
    	struct	iovec *uio_iov;
    	int	uio_iovcnt;
    	off_t	uio_offset;
    	size_t	uio_resid;
    	enum	uio_rw uio_rw;
    	struct	vmspace *uio_vmspace;
    };

A struct uio typically describes data in motion. Several of the fields described below reflect that expectation.

uio_iov
  Pointer to array of I/O vectors to be processed. The struct iovec is defined to be:

      struct iovec {
      	void	*iov_base;
      	size_t	 iov_len;
      };

  The members in the struct iovec should only be initialized. These are:

  iov_base
    The address for a range of memory to or from which data is transferred.
  iov_len
    The number of bytes of data to be transferred to or from the range of memory starting at iov_base.
uio_iovcnt
  The number of I/O vectors in the uio_iov array.
uio_offset
  An offset into the corresponding object.
uio_resid
  The amount of space described by the structure; notionally, the amount of data remaining to be transferred.
uio_rw
  A flag indicating whether data should be read into the space (UIO_READ) or written from the space (UIO_WRITE).
uio_vmspace
  A pointer to the address space which is being transferred to or from.

The value of uio->uio_rw controls whether `uiomove`() copies data from buf to uio or vice versa.

The lesser of n or uio->uio_resid bytes are copied.

`uiomove`() changes fields of the structure pointed to by uio, such that uio->uio_resid is decremented by the amount of data moved, uio->uio_offset is incremented by the same amount, and the array of iovecs is adjusted to point that much farther into the region described. This allows multiple calls to `uiomove`() to easily be used to fill or drain the region of data.

# RETURN VALUES

Upon successful completion, `uiomove`() returns 0. If a bad address is encountered, `EFAULT` is returned.

# SEE ALSO

copy(9), ufetch(9), ustore(9)

April 26, 2010 | NetBSD 9.5