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
Theuiomove()
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.