a90fbe1dbb
- .Nd in section NAME is not optional - .Ed was missing - "indent" is not a flag, but a literal argument for -offset - stop switching font sizes for acronyms - use .Brq instead of rolling our own
131 lines
3.6 KiB
Groff
131 lines
3.6 KiB
Groff
.\"
|
|
.\" 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.
|
|
.\"
|
|
.\" $FreeBSD$
|
|
.\"
|
|
.Dd June 01, 2010
|
|
.Dt IO 4
|
|
.Os
|
|
.Sh NAME
|
|
.Nm io
|
|
.Nd I/O privilege file
|
|
.Sh SYNOPSIS
|
|
.Cd "device io"
|
|
.Pp
|
|
.In sys/types.h
|
|
.In sys/ioctl.h
|
|
.In dev/io/iodev.h
|
|
.In machine/iodev.h
|
|
.Bd -literal
|
|
struct iodev_pio_req {
|
|
u_int access;
|
|
u_int port;
|
|
u_int width;
|
|
u_int val;
|
|
};
|
|
.Ed
|
|
.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).
|
|
This can be useful in order to write userland
|
|
programs that handle some hardware directly.
|
|
.Pp
|
|
The usual operations on the device are to open it via the
|
|
.Xr open 2
|
|
interface and to send I/O requests to the file descriptor using the
|
|
.Xr ioctl 2
|
|
syscall.
|
|
.Pp
|
|
The
|
|
.Xr ioctl 2
|
|
requests available for
|
|
.Pa /dev/io
|
|
are mostly platform dependent, but there are also some in common between
|
|
all of them.
|
|
The
|
|
.Dv IODEV_PIO
|
|
is used by all the architectures in order to request that an I/O operation
|
|
be performed.
|
|
It takes a 'struct iodev_pio_req' argument that must be previously setup.
|
|
.Pp
|
|
The
|
|
.Fa access
|
|
member specifies the type of operation requested.
|
|
It may be:
|
|
.Bl -tag -width IODEV_PIO_WRITE
|
|
.It Dv IODEV_PIO_READ
|
|
The operation is an "in" type.
|
|
A value will be read from the specified port
|
|
(retrieved from the
|
|
.Fa port
|
|
member) and the result will be stored in the
|
|
.Fa val
|
|
member.
|
|
.It Dv IODEV_PIO_WRITE
|
|
The operation is a "out" type.
|
|
The value will be fetched from the
|
|
.Fa val
|
|
member and will be written out to the specified port (defined as the
|
|
.Fa port
|
|
member).
|
|
.El
|
|
.Pp
|
|
Finally, the
|
|
.Fa width
|
|
member specifies the size of the operand to be read/written, expressed
|
|
in bytes.
|
|
.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 LEGACY
|
|
The
|
|
.Pa /dev/io
|
|
interface used to be very i386 specific and worked differently.
|
|
The initial implementation simply raised the
|
|
.Em IOPL
|
|
of the current thread when
|
|
.Xr open 2
|
|
was called on the device.
|
|
This behaviour is retained in the current implementation as legacy
|
|
support for both i386 and amd64 architectures.
|
|
.Sh SEE ALSO
|
|
.Xr close 2 ,
|
|
.Xr i386_get_ioperm 2 ,
|
|
.Xr i386_set_ioperm 2 ,
|
|
.Xr ioctl 2 ,
|
|
.Xr open 2 ,
|
|
.Xr mem 4
|
|
.Sh HISTORY
|
|
The
|
|
.Nm
|
|
file appeared in
|
|
.Fx 1.0 .
|