142 lines
4.1 KiB
Groff
142 lines
4.1 KiB
Groff
.\" $NetBSD: fetch.9,v 1.2 1996/01/09 21:59:24 perry Exp $
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.\"
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.\" Copyright (c) 1996 Jason R. Thorpe.
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.\" All rights reserved.
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.\"
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.\" This code is derived from software contributed by Kenneth Stailey.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed for the NetBSD Project
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.\" by Jason R. Thorpe.
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.\" 4. The name of the author may not be used to endorse or promote products
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.\" derived from this software without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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.\" BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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.\" AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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.\" OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd January 23, 2020
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.Dt FETCH 9
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.Os
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.Sh NAME
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.Nm fetch ,
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.Nm fubyte ,
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.Nm fuword ,
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.Nm fuword16 ,
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.Nm fuword32 ,
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.Nm fuword64 ,
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.Nm fueword ,
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.Nm fueword32 ,
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.Nm fueword64
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.Nd fetch data from user-space
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.Sh SYNOPSIS
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.In sys/types.h
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.In sys/systm.h
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.Ft int
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.Fn fubyte "volatile const void *base"
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.Ft long
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.Fn fuword "volatile const void *base"
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.Ft int
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.Fn fuword16 "volatile const void *base"
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.Ft int32_t
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.Fn fuword32 "volatile const void *base"
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.Ft int64_t
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.Fn fuword64 "volatile const void *base"
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.Ft int
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.Fn fueword "volatile const void *base" "long *val"
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.Ft int
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.Fn fueword32 "volatile const void *base" "int32_t *val"
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.Ft int
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.Fn fueword64 "volatile const void *base" "int64_t *val"
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.In sys/resourcevar.h
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.Sh DESCRIPTION
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The
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.Nm
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functions are designed to copy small amounts of data from user-space
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of the current process.
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If read is successful, it is performed atomically.
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The data read must be naturally aligned.
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.Pp
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The
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.Nm
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routines provide the following functionality:
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.Bl -tag -width "fueword32()"
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.It Fn fubyte
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Fetches a byte of data from the user-space address
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.Pa base .
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The byte read is zero-extended into the results variable.
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.It Fn fuword
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Fetches a word of data (long) from the user-space address
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.Pa base .
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.It Fn fuword16
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Fetches 16 bits of data from the user-space address
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.Pa base .
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The half-word read is zero-extended into the results variable.
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.It Fn fuword32
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Fetches 32 bits of data from the user-space address
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.Pa base .
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.It Fn fuword64
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Fetches 64 bits of data from the user-space address
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.Pa base .
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.It Fn fueword
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Fetches a word of data (long) from the user-space address
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.Pa base
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and stores the result in the variable pointed by
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.Pa val .
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.It Fn fueword32
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Fetches 32 bits of data from the user-space address
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.Pa base
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and stores the result in the variable pointed by
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.Pa val .
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.It Fn fueword64
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Fetches 64 bits of data from the user-space address
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.Pa base
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and stores the result in the variable pointed by
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.Pa val .
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.El
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.Pp
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The callers of
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.Fn fuword ,
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.Fn fuword32
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and
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.Fn fuword64
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functions cannot distinguish between -1 read from
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userspace and function failure.
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.Sh RETURN VALUES
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The
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.Fn fubyte ,
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.Fn fuword ,
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.Fn fuword16 ,
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.Fn fuword32 ,
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and
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.Fn fuword64
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functions return the data fetched or -1 on failure.
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The
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.Fn fueword ,
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.Fn fueword32
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and
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.Fn fueword64
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functions return 0 on success and -1 on failure.
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.Sh SEE ALSO
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.Xr copy 9 ,
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.Xr store 9
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