freebsd-skq/share/man/man4/io.4

.\"
.\" 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.
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.\" $FreeBSD$
.\"
.Dd October 3, 2004
.Dt IO 4 i386
.Os
.Sh NAME
.Nm io
.Nd I/O privilege file
.Sh SYNOPSIS
.Cd "device io"
.Sh DESCRIPTION
The special file
.Pa /dev/io
is a controlled security hole that allows a process to gain I/O
privileges
(which are normally reserved for kernel-internal code).
Any process that holds a file descriptor on
.Pa /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.
Note that even read-only access will grant the full I/O privileges.
.Pp
In addition to any file access permissions on
.Pa /dev/io ,
the kernel enforces that only the super-user may open this device.
.Sh FILES
.Bl -tag -width Pa -compact
.It Pa /dev/io
.El
.Sh SEE ALSO
.Xr i386_get_ioperm 2 ,
.Xr i386_set_ioperm 2 ,
.Xr mem 4
.Sh HISTORY
The
.Nm
file appeared in
.Fx 1.0 .
Document the /dev/io security hole. 1996-01-01 11:01:13 +00:00			`.\"`
			`.\" 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.`
			`.\"`
$Id$ -> $FreeBSD$ 1999-08-28 00:22:10 +00:00			`.\" $FreeBSD$`
Document the /dev/io security hole. 1996-01-01 11:01:13 +00:00			`.\"`
Add a SYNOPSIS section for io(4), mem(4), or random(4), since they are now optional devices. MFC after: 1 week 2004-10-03 13:14:20 +00:00			`.Dd October 3, 2004`
Document the /dev/io security hole. 1996-01-01 11:01:13 +00:00			`.Dt IO 4 i386`
			`.Os`
			`.Sh NAME`
			`.Nm io`
			`.Nd I/O privilege file`
Add a SYNOPSIS section for io(4), mem(4), or random(4), since they are now optional devices. MFC after: 1 week 2004-10-03 13:14:20 +00:00			`.Sh SYNOPSIS`
			`.Cd "device io"`
Document the /dev/io security hole. 1996-01-01 11:01:13 +00:00			`.Sh DESCRIPTION`
			`The special file`
Fix a bunch of man pages to stop abusing the .Nm macro, along with some other minor fixes for some problems I noticed while making these changes. Pointed out by: bde 1997-02-05 15:07:37 +00:00			`.Pa /dev/io`
Document the /dev/io security hole. 1996-01-01 11:01:13 +00:00			`is a controlled security hole that allows a process to gain I/O`
			`privileges`
mdoc(7) police: Avoid using parenthesis enclosure macros (.Pq and .Po/.Pc) with plain text. Not only this slows down the mdoc(7) processing significantly, but it also has an undesired (in this case) effect of disabling hyphenation within the entire enclosed block. 2001-08-07 15:48:51 +00:00			`(which are normally reserved for kernel-internal code).`
Document the /dev/io security hole. 1996-01-01 11:01:13 +00:00			`Any process that holds a file descriptor on`
Fix a bunch of man pages to stop abusing the .Nm macro, along with some other minor fixes for some problems I noticed while making these changes. Pointed out by: bde 1997-02-05 15:07:37 +00:00			`.Pa /dev/io`
Document the /dev/io security hole. 1996-01-01 11:01:13 +00:00			`open will get its`
			`.Em IOPL`
			`bits in the flag register set, thus allowing it to perform direct`
Mechanically kill hard sentence breaks and double whitespaces. 2004-07-03 18:29:24 +00:00			`I/O operations.`
			`This can be useful in order to write userland`
Document the /dev/io security hole. 1996-01-01 11:01:13 +00:00			`programs that handle some hardware directly.`
Update io(4) to match reality following revision 1.42 of sys/i386/i386/mem.c: only the super-user may open /dev/io regardless of the device permissions (just 4 years late!). Also, add cross-reference to i386_{get,set}_ioperm(2). PR: kern/13359 2001-08-12 21:08:34 +00:00			`Note that even read-only access will grant the full I/O privileges.`
Document the /dev/io security hole. 1996-01-01 11:01:13 +00:00			`.Pp`
Update io(4) to match reality following revision 1.42 of sys/i386/i386/mem.c: only the super-user may open /dev/io regardless of the device permissions (just 4 years late!). Also, add cross-reference to i386_{get,set}_ioperm(2). PR: kern/13359 2001-08-12 21:08:34 +00:00			`In addition to any file access permissions on`
Fix a bunch of man pages to stop abusing the .Nm macro, along with some other minor fixes for some problems I noticed while making these changes. Pointed out by: bde 1997-02-05 15:07:37 +00:00			`.Pa /dev/io ,`
Update io(4) to match reality following revision 1.42 of sys/i386/i386/mem.c: only the super-user may open /dev/io regardless of the device permissions (just 4 years late!). Also, add cross-reference to i386_{get,set}_ioperm(2). PR: kern/13359 2001-08-12 21:08:34 +00:00			`the kernel enforces that only the super-user may open this device.`
Document the /dev/io security hole. 1996-01-01 11:01:13 +00:00			`.Sh FILES`
			`.Bl -tag -width Pa -compact`
			`.It Pa /dev/io`
			`.El`
			`.Sh SEE ALSO`
mdoc(7) police: fix SEE ALSO. 2001-08-14 15:53:07 +00:00			`.Xr i386_get_ioperm 2 ,`
			`.Xr i386_set_ioperm 2 ,`
Document the /dev/io security hole. 1996-01-01 11:01:13 +00:00			`.Xr mem 4`
			`.Sh HISTORY`
			`The`
mdoc(7) police: use the new features of the Nm macro. 2000-11-20 18:41:33 +00:00			`.Nm`
Document the /dev/io security hole. 1996-01-01 11:01:13 +00:00			`file appeared in`
Use the .Fx macro for FreeBSD references for releases prior to 2.0. Use the .Tn macro for generic FreeBSD references. Cleanup other formatting problems noticed while making the above changes. 1997-03-21 20:14:15 +00:00			`.Fx 1.0 .`