102 lines
3.3 KiB
Groff
102 lines
3.3 KiB
Groff
.\" $NetBSD: fetch.9,v 1.5 1997/11/11 10:07:10 mrg 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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.Dd Jan 7, 1996
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.Dt FETCH 9
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.Os NetBSD
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.Sh NAME
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.Nm fetch ,
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.Nm fubyte ,
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.Nm fuibyte ,
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.Nm fusword ,
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.Nm fuswintr ,
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.Nm fuword ,
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.Nm fuiword
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.Nd fetch data from user-space
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.Sh SYNOPSIS
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.Fd #include <sys/types.h>
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.Fd #include <sys/systm.h>
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.Ft int
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.Fn fubyte "void *base"
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.Ft int
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.Fn fusword "void *base"
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.Ft int
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.Fn fuswintr "void *base"
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.Ft int
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.Fn fuword "void *base"
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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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.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 "fuswintr()"
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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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.Fa base .
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.It Fn fusword
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Fetches a short word of data from the user-space address
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.Fa base .
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.It Fn fuswintr
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Fetches a short word of data from the user-space address
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.Fa base .
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This function is safe to call during an interrupt context.
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.It Fn fuword
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Fetches a word of data from the user-space address
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.Fa base .
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.El
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.Sh RETURN VALUES
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The
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.Nm
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functions return the data fetched or -1 on failure.
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Note that these functions all do "unsigned" access, and
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therefore will never sign extend byte or short values.
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This prevents ambiguity with the error return value
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for all functions except
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.Fn fuword .
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.Sh BUGS
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.Pp
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The function
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.Fn fuword
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has no way to unambiguously signal an error, because the
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data it reads might legetimately be the same as the -1
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used to indicate an error. The other functions do not
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have this problem because the unsigned values returned
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by those can never match the -1 error return value.
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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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