VHook86D: A VxD that Hooks Interrupt 2Fh in V86 Mode

Revised: February 1993

VHook86D is a virtual device (VxD) that demonstrates the
use of Hook_V86_Int_Chain, which is one of the virtual
 machine (VM) interrupt and callback services. VHook86D
exists for demonstration purposes only; this VxD adversely
affects system performance because it hooks Interrupt 2Fh
and prints Trace_Out messages to the debugging monitor.


To build VHook86D:

You will need Microsoft(R) 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(TM) version 3.1 Device Driver Kit
(DDK), you can build its version of VHook86D 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 VHook86D:

1.  Run VHOOK86D.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. VHook86D 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 VHOOK86D.EXE
to VHOOK86D.386 and move it to the Windows SYSTEM
subdirectory. Add the line DEVICE=VHOOK86D.386 to the
[386Enh] section of the SYSTEM.INI file.

2.  Run Windows in enhanced mode and watch the debugging
display (which must be connected to COM1). The Trace_Out
messages will slow the system down to a c-r-a-w-l.

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.

VHook86D 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)

THIS TOOL IS NOT SUPPORTED BY MICROSOFT CORPORATION. IT IS
PROVIDED "AS IS" BECAUSE WE BELIEVE IT MAY BE USEFUL TO
YOU. PLEASE DO NOT CONTACT MICROSOFT PRODUCT SUPPORT
SERVICES FOR SUPPORT OR ASSISTANCE SHOULD YOU HAVE
PROBLEMS USING THIS TOOL.

READ THE ASSOCIATED DOCUMENTATION, IF ANY, REGARDING THIS
TOOL PRIOR TO USING. ANY USE BY YOU OF THE TOOL IS AT YOUR
OWN RISK. THE TOOL IS PROVIDED FOR USE "AS IS" WITHOUT
WARRANTY OF ANY KIND. MICROSOFT AND ITS SUPPLIERS DISCLAIM
ALL WARRANTIES OF ANY KIND, EITHER EXPRESS OR IMPLIED,
INCLUDING, WITHOUT LIMITATION, IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
