1.\" $NetBSD: fetch.9,v 1.2 1996/01/09 21:59:24 perry Exp $ 2.\" 3.\" Copyright (c) 1996 Jason R. Thorpe. 4.\" All rights reserved. 5.\" 6.\" This code is derived from software contributed by Kenneth Stailey. 7.\" 8.\" Redistribution and use in source and binary forms, with or without 9.\" modification, are permitted provided that the following conditions 10.\" are met: 11.\" 1. Redistributions of source code must retain the above copyright 12.\" notice, this list of conditions and the following disclaimer. 13.\" 2. Redistributions in binary form must reproduce the above copyright 14.\" notice, this list of conditions and the following disclaimer in the 15.\" documentation and/or other materials provided with the distribution. 16.\" 3. All advertising materials mentioning features or use of this software 17.\" must display the following acknowledgement: 18.\" This product includes software developed for the NetBSD Project 19.\" by Jason R. Thorpe. 20.\" 4. The name of the author may not be used to endorse or promote products 21.\" derived from this software without specific prior written permission. 22.\" 23.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 24.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 25.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 26.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 27.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 28.\" BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 29.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 30.\" AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 31.\" OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33.\" SUCH DAMAGE. 34.\" 35.Dd June 29, 2026 36.Dt FETCH 9 37.Os 38.Sh NAME 39.Nm fetch , 40.Nm fubyte , 41.Nm fuword , 42.Nm fuword16 , 43.Nm fuword32 , 44.Nm fuword64 , 45.Nm fueptr , 46.Nm fueword , 47.Nm fueword32 , 48.Nm fueword64 49.Nd fetch data from user-space 50.Sh SYNOPSIS 51.In sys/types.h 52.In sys/systm.h 53.Ft int 54.Fn fubyte "volatile const void *base" 55.Ft long 56.Fn fuword "volatile const void *base" 57.Ft int 58.Fn fuword16 "volatile const void *base" 59.Ft int32_t 60.Fn fuword32 "volatile const void *base" 61.Ft int64_t 62.Fn fuword64 "volatile const void *base" 63.Ft int 64.Fn fueptr "volatile const void *base" "intptr_t *val" 65.Ft int 66.Fn fueword "volatile const void *base" "long *val" 67.Ft int 68.Fn fueword32 "volatile const void *base" "int32_t *val" 69.Ft int 70.Fn fueword64 "volatile const void *base" "int64_t *val" 71.Sh DESCRIPTION 72The 73.Nm 74functions are designed to copy small amounts of data from user-space 75of the current process. 76If the user address is naturally aligned, then the operation will be 77performed atomically. 78Otherwise it may fail or be performed non-atomically, depending on 79the platform. 80.Pp 81The 82.Nm 83routines provide the following functionality: 84.Bl -tag -width "fueword32()" 85.It Fn fubyte 86Fetches a byte of data from the user-space address 87.Pa base . 88The byte read is zero-extended into the results variable. 89.It Fn fuword 90Fetches a word of data (long) from the user-space address 91.Pa base . 92.It Fn fuword16 93Fetches 16 bits of data from the user-space address 94.Pa base . 95The half-word read is zero-extended into the results variable. 96.It Fn fuword32 97Fetches 32 bits of data from the user-space address 98.Pa base . 99.It Fn fuword64 100Fetches 64 bits of data from the user-space address 101.Pa base . 102.It Fn fueptr 103Fetches a pointer from the user-space address 104.Pa base 105and stores the result in the variable pointed by 106.Pa val . 107.Fn fueptr 108preserves the provenance of pointers fetched from user-space 109.Pq see Xr memory_model 7 for further information . 110.It Fn fueword 111Fetches a word of data (long) from the user-space address 112.Pa base 113and stores the result in the variable pointed by 114.Pa val . 115.It Fn fueword32 116Fetches 32 bits of data from the user-space address 117.Pa base 118and stores the result in the variable pointed by 119.Pa val . 120.It Fn fueword64 121Fetches 64 bits of data from the user-space address 122.Pa base 123and stores the result in the variable pointed by 124.Pa val . 125.El 126.Pp 127The callers of 128.Fn fuword , 129.Fn fuword32 130and 131.Fn fuword64 132functions cannot distinguish between -1 read from 133userspace and function failure. 134.Sh RETURN VALUES 135The 136.Fn fubyte , 137.Fn fuword , 138.Fn fuword16 , 139.Fn fuword32 , 140and 141.Fn fuword64 142functions return the data fetched or -1 on failure. 143The 144.Fn fueptr , 145.Fn fueword , 146.Fn fueword32 147and 148.Fn fueword64 149functions return 0 on success and -1 on failure. 150.Sh SEE ALSO 151.Xr copy 9 , 152.Xr store 9 153