.\" $NetBSD: uiomove.9,v 1.18.8.2 2019/09/05 08:19:41 martin Exp $ .\" .\" Copyright (c) 1996 The NetBSD Foundation, Inc. .\" All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" .\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS .\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED .\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR .\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS .\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR .\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF .\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS .\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN .\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE .\" POSSIBILITY OF SUCH DAMAGE. .\" .Dd April 26, 2010 .Dt UIOMOVE 9 .Os .Sh NAME .Nm uiomove .Nd move data described by a struct uio .Sh SYNOPSIS .In sys/systm.h .Ft int .Fn uiomove "void *buf" "size_t n" "struct uio *uio" .Sh DESCRIPTION The .Fn uiomove function copies up to .Fa n bytes between the kernel-space address pointed to by .Fa buf and the addresses described by .Fa uio , which may be in user-space or kernel-space. .Pp The .Fa uio argument is a pointer to a .Va struct uio as defined by .In sys/uio.h : .Bd -literal -offset indent 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; }; .Ed .Pp A .Va struct uio typically describes data in motion. Several of the fields described below reflect that expectation. .Bl -tag -width "uio_vmspace " .It Va uio_iov Pointer to array of .Tn I/O vectors to be processed. The .Va struct iovec is defined to be: .Bd -literal -offset indent struct iovec { void *iov_base; size_t iov_len; }; .Ed .Pp The members in the .Va struct iovec should only be initialized. These are: .Bl -tag -width "*iov_base " -offset indent .It Va iov_base The address for a range of memory to or from which data is transferred. .It Va iov_len The number of bytes of data to be transferred to or from the range of memory starting at .Va iov_base . .El .It Va uio_iovcnt The number of .Tn I/O vectors in the .Va uio_iov array. .It Va uio_offset An offset into the corresponding object. .It Va uio_resid The amount of space described by the structure; notionally, the amount of data remaining to be transferred. .It Va uio_rw A flag indicating whether data should be read into the space (UIO_READ) or written from the space (UIO_WRITE). .It Va uio_vmspace A pointer to the address space which is being transferred to or from. .El .Pp The value of .Va uio->uio_rw controls whether .Fn uiomove copies data from .Fa buf to .Fa uio or vice versa. .Pp The lesser of .Fa n or .Va uio->uio_resid bytes are copied. .Pp .Fn uiomove changes fields of the structure pointed to by .Fa uio , such that .Va uio->uio_resid is decremented by the amount of data moved, .Va 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 .Fn uiomove to easily be used to fill or drain the region of data. .Sh RETURN VALUES Upon successful completion, .Fn uiomove returns 0. If a bad address is encountered, .Er EFAULT is returned. .Sh SEE ALSO .Xr copy 9 , .Xr ufetch 9 , .Xr ustore 9