NetBSD/lib/libarch/i386/i386_iopl.2

.\"	$NetBSD: i386_iopl.2,v 1.6 1997/07/30 23:13:27 jtc Exp $
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.\" Copyright (c) 1996 The NetBSD Foundation, Inc.
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.\" This code is derived from software contributed to The NetBSD Foundation
.\" by John T. Kohl and Charles M. Hannum.
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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 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.