2 files changed, 66 insertions, 0 deletions

diff --git a/share/man/man4/man4.i386/Makefile b/share/man/man4/man4.i386/Makefile
index c0d098fd76d6..bcb17e93f00d 100644
--- a/share/man/man4/man4.i386/Makefile
+++ b/share/man/man4/man4.i386/Makefile
@@ -21,6 +21,7 @@ MLINKS+=	fdc.4 ../fdc.4
 MLINKS+=	fe.4 ../fe.4
 MLINKS+=	ie.4 ../ie.4
 MLINKS+=	is.4 ../is.4
+MLINKS+=	io.4 ../io.4
 MLINKS+=	joy.4 ../joy.4
 MLINKS+=	keyboard.4 ../keyboard.4
 MLINKS+=	labpc.4 ../labpc.4
diff --git a/share/man/man4/man4.i386/io.4 b/share/man/man4/man4.i386/io.4
new file mode 100644
index 000000000000..1a076ff57f60
--- /dev/null
+++ b/share/man/man4/man4.i386/io.4
@@ -0,0 +1,65 @@
+.\"
+.\" Copyright (c) 1996 Joerg Wunsch
+.\"
+.\" All rights reserved.
+.\"
+.\" This program is free software.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\"    notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\"    notice, this list of conditions and the following disclaimer in the
+.\"    documentation and/or other materials provided with the distribution.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR
+.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT,
+.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+.\"
+.\" $Id$
+.\"
+.Dd Jan 1, 1996
+.Dt IO 4 i386
+.Os
+.Sh NAME
+.Nm io
+.Nd I/O privilege file
+.Sh DESCRIPTION
+The special file
+.Nm /dev/io
+is a controlled security hole that allows a process to gain I/O
+privileges
+.Pq which are normally reserved for kernel-internal code .
+Any process that holds a file descriptor on
+.Nm /dev/io
+open will get its
+.Em IOPL
+bits in the flag register set, thus allowing it to perform direct
+I/O operations.  This can be useful in order to write userland
+programs that handle some hardware directly.
+.Pp
+The entire access control is handled by the file access permissions
+of
+.Nm /dev/io ,
+so care should be taken in granting rights for this device.  Note
+that even read/only access will grant the full I/O privileges.
+.Sh FILES
+.Bl -tag -width Pa -compact
+.It Pa /dev/io
+.El
+.Sh SEE ALSO
+.Xr mem 4
+.Sh HISTORY
+The
+.Nm io
+file appeared in
+FreeBSD 1.0.