freebsd-skq/share/man/man9/fetch.9

.\"	$NetBSD: fetch.9,v 1.2 1996/01/09 21:59:24 perry Exp $
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.\" Copyright (c) 1996 Jason R. Thorpe.
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.\" This code is derived from software contributed by Kenneth Stailey.
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.\"	by Jason R. Thorpe.
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.Dd October 21, 2014
.Dt FETCH 9
.Os
.Sh NAME
.Nm fetch ,
.Nm fubyte ,
.Nm fuswintr ,
.Nm fuword ,
.Nm fuword16 ,
.Nm fuword32 ,
.Nm fuword64 ,
.Nm fueword ,
.Nm fueword32 ,
.Nm fueword64
.Nd fetch data from user-space
.Sh SYNOPSIS
.In sys/types.h
.In sys/systm.h
.Ft int
.Fn fubyte "const void *base"
.Ft long
.Fn fuword "const void *base"
.Ft int
.Fn fuword16 "void *base"
.Ft int32_t
.Fn fuword32 "const void *base"
.Ft int64_t
.Fn fuword64 "const void *base"
.Ft long
.Fn fueword "const void *base" "long *val"
.Ft int32_t
.Fn fueword32 "const void *base" "int32_t *val"
.Ft int64_t
.Fn fueword64 "const void *base" "int64_t *val"
.In sys/resourcevar.h
.Ft int
.Fn fuswintr "void *base"
.Sh DESCRIPTION
The
.Nm
functions are designed to copy small amounts of data from user-space
of the current process.
If read is successful, it is performed atomically.
The data read must be naturally aligned.
.Pp
The
.Nm
routines provide the following functionality:
.Bl -tag -width "fueword32()"
.It Fn fubyte
Fetches a byte of data from the user-space address
.Pa base .
The byte read is zero-extended into the results variable.
.It Fn fuword
Fetches a word of data (long) from the user-space address
.Pa base .
.It Fn fuword16
Fetches 16 bits of data from the user-space address
.Pa base .
The half-word read is zero-extended into the results variable.
.It Fn fuword32
Fetches 32 bits of data from the user-space address
.Pa base .
.It Fn fuword64
Fetches 64 bits of data from the user-space address
.Pa base .
.It Fn fuswintr
Fetches a short word of data from the user-space address
.Pa base .
This function is safe to call during an interrupt context.
.It Fn fueword
Fetches a word of data (long) from the user-space address
.Pa base
and stores the result in the variable pointed by
.Pa val .
.It Fn fueword32
Fetches 32 bits of data from the user-space address
.Pa base
and stores the result in the variable pointed by
.Pa val .
.It Fn fueword64
Fetches 64 bits of data from the user-space address
.Pa base
and stores the result in the variable pointed by
.Pa val .
.El
.Pp
The callers of
.Fn fuword ,
.Fn fuword32
and
.Fn fuword64
functions cannot distinguish between -1 read from
userspace and function failure.
.Sh RETURN VALUES
The
.Fn fubyte ,
.Fn fuword ,
.Fn fuword16 ,
.Fn fuword32 ,
.Fn fuword64 ,
and
.Fn fuswintr
functions return the data fetched or -1 on failure.
The
.Fn fueword ,
.Fn fueword32
and
.Fn fueword64
functions return 0 on success and -1 on failure.
.Sh SEE ALSO
.Xr copy 9 ,
.Xr store 9