.\"	$OpenBSD: i386_get_ioperm.2,v 1.12 2004/03/12 17:56:06 jmc Exp $
.\"	$NetBSD: i386_get_ioperm.2,v 1.3 1996/02/27 22:57:17 jtc 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.
.\"
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.\"    must display the following acknowledgement:
.\"	   This product includes software developed by the NetBSD
.\"	   Foundation, Inc. and its contributors.
.\" 4. Neither the name of The NetBSD Foundation nor the names of its
.\"    contributors may be used to endorse or promote products derived
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.Dd October 14, 1995
.Dt I386_GET_IOPERM 2 i386
.Os
.Sh NAME
.Nm i386_get_ioperm ,
.Nm i386_set_ioperm
.Nd manage i386 per-process I/O permission bitmap
.Sh SYNOPSIS
.Fd #include <sys/types.h>
.Fd #include <machine/sysarch.h>
.Ft int
.Fn i386_get_ioperm "u_long *iomap"
.Ft int
.Fn i386_set_ioperm "u_long *iomap"
.Sh DESCRIPTION
.Fn i386_get_ioperm
copies the current I/O permission bitmap into the memory referenced by
.Fa iomap .
.Pp
.Fn i386_set_ioperm
sets the I/O permission bitmap from the data pointed to by
.Fa iomap .
This call is restricted to the superuser.
.Pp
The permission bitmap contains 1024 bits in 32 longwords.
If bit
.Va n
is clear in the bitmap, then access is granted to I/O port
.Va n .
If bit
.Va n
is set in the bitmap, then an attempt to access I/O port
.Va n
results in delivery of a
.Dv SIGBUS
signal unless the process's I/O permission level would grant I/O access.
.Pp
.Sy Note:
Code using the
.Fn i386_get_ioperm
and
.Fn i386_set_ioperm
functions must be compiled using
.Cm -li386 .
.Sh RETURN VALUES
Upon successful completion,
.Fn i386_get_ioperm
and
.Fn i386_set_ioperm
return 0.
Otherwise, a value of \-1 is returned and the global variable
.Va errno
is set to indicate the error.
.Sh ERRORS
.Fn i386_get_ioperm
and
.Fn i386_set_ioperm
will fail if:
.Bl -tag -width [EINVAL]
.It Bq Er EFAULT
.Fa iomap
points outside the process's allocated address space.
.It Bq Er EPERM
The caller was not the superuser.
.El
.Sh SEE ALSO
.Xr i386_iopl 2
.Rs
.%A Intel
.%T i386 Microprocessor Programmer's Reference Manual
.Re
.Sh WARNING
You can really hose your machine if you enable user-level I/O and
write to hardware ports without care.
.Sh BUGS
The bitmap should really cover 65536 bits, but that's just too big for
allocation in a kernel structure.
If you need access to ports beyond 1024, use
.Xr i386_iopl 2 .