NetBSD/lib/libarch/i386/i386_iopl.2

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.\" $NetBSD: i386_iopl.2,v 1.7 1998/02/05 18:45:24 perry Exp $
.\"
.\" Copyright (c) 1996 The NetBSD Foundation, Inc.
.\" All rights reserved.
.\"
.\" This code is derived from software contributed to The NetBSD Foundation
.\" by John T. Kohl and Charles M. Hannum.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
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.\" must display the following acknowledgement:
.\" This product includes software developed by the NetBSD
.\" Foundation, Inc. and its contributors.
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.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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.Dd October 14, 1995
.Dt I386_IOPL 2
.Os NetBSD
.Sh NAME
.Nm i386_iopl
.Nd change the i386 I/O privilege level
.Sh LIBRARY
.Lb libi386
.Sh SYNOPSIS
.Fd #include <sys/types.h>
.Fd #include <machine/sysarch.h>
.Ft int
.Fn i386_iopl "int iopl"
.Sh DESCRIPTION
.Fn i386_iopl
sets the i386 I/O privilege level to the value specified by
.Ar iopl .
This call is restricted to the super-user.
.Sh RETURN VALUES
Upon successful completion,
.Fn i386_iopl
returns 0.
Otherwise, a value of -1 is returned and the global
variable
.Va errno
is set to indicate the error.
.Sh ERRORS
.Fn i386_iopl
will fail if:
.Bl -tag -width [EINVAL]
.It Bq Er EPERM
The caller was not the super-user, or the operation was not permitted at the
current security level.
.El
.Sh SEE ALSO
.Xr i386_set_ioperm 2 ,
.Xr i386_get_ioperm 2 .
.Sh REFERENCES
i386 Microprocessor Programmer's Reference Manual, Intel
.Sh WARNING
You can really hose your machine if you enable user-level I/O and
write to hardware ports without care.