1.\" $NetBSD: uiomove.9,v 1.17 2010/04/26 07:51:36 jruoho Exp $ 2.\" 3.\" Copyright (c) 1996 The NetBSD Foundation, Inc. 4.\" All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 15.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 16.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 17.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 18.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 19.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 20.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 21.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 22.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 23.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 24.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 25.\" POSSIBILITY OF SUCH DAMAGE. 26.\" 27.Dd April 26, 2010 28.Dt UIOMOVE 9 29.Os 30.Sh NAME 31.Nm uiomove 32.Nd move data described by a struct uio 33.Sh SYNOPSIS 34.In sys/systm.h 35.Ft int 36.Fn uiomove "void *buf" "size_t n" "struct uio *uio" 37.Sh DESCRIPTION 38The 39.Fn uiomove 40function copies up to 41.Fa n 42bytes between the kernel-space address pointed 43to by 44.Fa buf 45and the addresses described by 46.Fa uio , 47which may be in user-space or kernel-space. 48.Pp 49The 50.Fa uio 51argument is a pointer to a 52.Va struct uio 53as defined by 54.In sys/uio.h : 55.Bd -literal -offset indent 56struct uio { 57 struct iovec *uio_iov; 58 int uio_iovcnt; 59 off_t uio_offset; 60 size_t uio_resid; 61 enum uio_rw uio_rw; 62 struct vmspace *uio_vmspace; 63}; 64.Ed 65.Pp 66A 67.Va struct uio 68typically describes data in motion. 69Several of the fields described below reflect that expectation. 70.Pp 71.Bl -tag -width "uio_vmspace " 72.It Va uio_iov 73Pointer to array of 74.Tn I/O 75vectors to be processed. 76The 77.Va struct iovec 78is defined to be: 79.Bd -literal -offset indent 80struct iovec { 81 void *iov_base; 82 size_t iov_len; 83}; 84.Ed 85.Pp 86The members in the 87.Va struct iovec 88should only be initialized. 89These are: 90.Bl -tag -width "*iov_base " -offset indent 91.It Va iov_base 92The address for a range of memory to or from which data is transferred. 93.It Va iov_len 94The number of bytes of data to be transferred to 95or from the range of memory starting at 96.Va iov_base . 97.El 98.It Va uio_iovcnt 99The number of 100.Tn I/O 101vectors in the 102.Va uio_iov 103array. 104.It Va uio_offset 105An offset into the corresponding object. 106.It Va uio_resid 107The amount of space described by the structure; notionally, the amount 108of data remaining to be transferred. 109.It Va uio_rw 110A flag indicating whether data should be read into the space 111(UIO_READ) or written from the space (UIO_WRITE). 112.It Va uio_vmspace 113A pointer to the address space which is being transferred to or from. 114.El 115.Pp 116The value of 117.Va uio-\*[Gt]uio_rw 118controls whether 119.Fn uiomove 120copies data from 121.Fa buf 122to 123.Fa uio 124or vice versa. 125.Pp 126The lesser of 127.Fa n 128or 129.Va uio-\*[Gt]uio_resid 130bytes are copied. 131.Pp 132.Fn uiomove 133changes fields of the structure pointed to by 134.Fa uio , 135such that 136.Va uio-\*[Gt]uio_resid 137is decremented by the amount of data moved, 138.Va uio-\*[Gt]uio_offset 139is incremented by the same amount, and the array of iovecs is adjusted 140to point that much farther into the region described. 141This allows multiple calls to 142.Fn uiomove 143to easily be used to fill or drain the region of data. 144.Sh RETURN VALUES 145Upon successful completion, 146.Fn uiomove 147returns 0. 148If a bad address is encountered, 149.Er EFAULT 150is returned. 151.Sh SEE ALSO 152.Xr copy 9 , 153.Xr fetch 9 , 154.Xr store 9 155