Index for Section 9r

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uiomove(9r)
NAME
  uiomove - General: Moves data between user and system virtual space

SYNOPSIS
  #include <sys/uio.h>

  int uiomove(
	  caddr_t kern_buf,
	  int nbytes,
	  struct uio *uio );

ARGUMENTS
  kern_buf
      Specifies a pointer to the kernel buffer in system virtual space.

  nbytes
      Specifies the number of bytes of data to be moved.

  uio Specifies a pointer to a uio structure.  This structure describes the
      current position within a logical user buffer in user virtual space.

DESCRIPTION
  The uiomove routine moves data between user and system virtual space. Data
  can be moved in either direction. Accessibility to the logical user buffer
  is verified before the move is made. Accessibility to the kernel buffer is
  always assumed.

  The kernel buffer must always be of sufficient size to accommodate the
  data. It cannot be less than the number of bytes requested to be moved.
  Data corruption or a system panic may result if this condition occurs.

  The size of the logical user buffer, as described by the uio structure, may
  be less than, equal to, or greater than the number of bytes requested. The
  number of bytes actually moved is truncated whenever this size is not
  sufficient to fulfill a request. In all other cases, only the bytes
  requested are moved.

  Normally there is no need for kernel modules to set up uio structures or
  worry about their composition or content. The uio structures are usually
  set up externally to kernel modules.	Their addresses are passed in through
  the dsent table as arguments to module read and write routines.  The user
  logical buffers they describe are accessed only by routines external to the
  module, for example, uiomove. The external uio structures are quite often
  updated by such accesses.

  The uiomove routine always updates the uio structure to reflect the number
  of bytes actually moved.  The structure continues to describe the current
  position within the logical user buffer. The structure members that are
  subject to change are listed in the SIDE EFFECTS section.

NOTES
  You can also use the uiomove routine to move data only within system
  virtual space. In such cases, you still specify a pointer to a uio
  structure. However, in these cases, the structure describes a logical
  buffer in system virtual space.

SIDE EFFECTS
  The uiomove routine can update the following members of the uio structure:

  uio_iov
      Specifies the address of the current logical buffer segment.

  uio_iovcnt
      Specifies the number of remaining logical buffer segments.

  uio_resid
      Specifies the size of the remaining logical buffer.

  uio_offset
      Specifies the current offset into the full logical buffer.

  The uiomove routine can update the following members of uio_iov (the
  logical buffer segment descriptor vector):

  iov_base
	  Specifies the address of the current byte within the current
	  logical buffer segment.

  iov_len Specifies the remaining size of the current segment.

RETURN VALUES
  Upon successfully moving the data, the uiomove routine returns the value 0
  (zero). This action implies that the user virtual space described by the
  uio structure is accessible.	Otherwise, uiomove returns the error value
  EFAULT, indicating an inability to fully access the user virtual space from
  within the context of the current process. A partial move may have occurred
  before the logical user buffer became inaccessible. The uio structure is
  appropriately updated to reflect such partial moves.

  The EFAULT return value is suitable for placement in the u_error member of
  the user structure. Following failure of a system call, this member
  contains the error code automatically returned in errno to the current
  process.  Kernel module writers should explicitly set this value when it is
  returned and disallow the requested operation. This setting lets the
  current process determine the appropriate reason (``bad address'') why its
  request could not be satisfied.

SEE ALSO
  Routines: copyin(9r), copyout(9r), fubyte(9r), subyte(9r)

  Data Structures: uio(9s)

Index for Section 9r

Alphabetical listing for U

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