VMIOD: A VxD that Monitors I/O Traffic on a Port

Revised: February 1993

VMIOD, the virtual monitor I/O device, is a VxD that
demonstrates how to call the Install_IO_Handler service to
monitor I/O traffic on a port. Although most VxDs that use
this service are designed to virtualize the I/O port,
VMIOD only monitors the port and writes to a secondary
monitor to display the port activity.

Warning:  The Microsoft(R) Windows(TM) operating system
allows only one I/O handler per port. This means that you
can't install an I/O handler on a port that is already
trapped in the system. Most of the hardware devices that
Windows knows about (keyboard, timer, video) are trapped
ports, and thus cannot be monitored by VMIOD. For a simple
demonstration of VMIOD, try 3F5, a floppy controller port.
This port was untrapped in the retail release of Windows
versions 3.0 and 3.1.

VMIOD only demonstrates I/O port trapping, not interrupt
request (IRQ) handling. See the VMIRQD sample for more
information on working with IRQs.

VMIOD uses the following virtual machine manager (VMM)
services:

>  Get_Profile_Hex_Int
>  Install_IO_Handler
>  Clear_Mono_Screen
>  Set_Mono_Cur_Pos
>  Out_Mono_String


To build VMIOD:

You will need Microsoft Macro Assembler version 6.0 or
higher, as well as some special tools and include files;
 see the "VxD Tools" and "VxD Include Files" abstracts to
copy these files to your development system. Configure
your development environment as described in the "VxD-Lite
Mini-DDK" technical article on the Microsoft Developer
Network CD.

If you have the Windows version 3.1 Device Driver Kit
(DDK), you can build its version of VMIOD using the DDK-
supplied MASM5.EXE (a special version of Macro Assembler
version 5.10). Note that the DDK samples require a
specific structure for the source and include
subdirectories, whereas the corresponding samples in the
"VxD-Lite Mini-DDK" utilize the INCLUDE environment
variable to give you more flexibility in structuring your
development files.


To execute VMIOD:

To use VMIOD, you must have a secondary (monochrome)
monitor on your system.

1.  Place the following lines in the [386Enh] section of
your SYSTEM.INI file:

     DEBUGMONO=TRUE
     VMIOD_Port=nnnn

where nnnn is the hex I/O port number to monitor (try
floppy controller port 3F5).

2.  Run VMIOD.EXE from the MS-DOS(R) prompt before
starting Windows. When enhanced-mode Windows starts up,
the VxD will load automatically. Thus, you do not need to
modify the SYSTEM.INI file to load this VxD. VMIOD will
automatically load each time you start Windows until you
reboot your computer; once rebooted, the stub loader is
cleared from memory and the VxD will not load.

If you prefer to have Windows load the VxD without first
executing it from the MS-DOS prompt, rename VMIOD.EXE to
VMIOD.386 and move it to the Windows SYSTEM subdirectory.
Add the line DEVICE=VMIOD.386 to the [386Enh] section of
the SYSTEM.INI file.

3.  Run Windows in enhanced mode. The code responsible for
self-loading the VxD is in the VXDSTUB.ASM file and is
linked into the final VxD file by the STUB 'VXDSTUB.EXE'
module definition (.DEF) file statement. When executed
from the MS-DOS prompt, the VxDStub hooks Interrupt 2Fh,
terminates, and stays resident. When Microsoft Windows
initializes itself, the TSR responds to the Interrupt 2Fh,
AX=1605h broadcast and returns a structure that causes the
VxD to be loaded. This technique is discussed in the "TSR
Support in Microsoft Windows Version 3.1" technical
article on the Microsoft Developer Network CD.

VMIOD was built and tested under Microsoft Windows version
3.1 using Microsoft MASM versions 6.0 and 6.1 and the
tools and include files provided in the "VxD-Lite Mini-
DDK."

KEYWORDS: PR-CD1; CD3 (revised)

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