Thunking & Ring 0

[Walt Decker]

1. Is there a way to access 16-bit real-mode data?

2. Is there a way to go up to ring 0 in order to obtain direct acces to hardware?


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[Steve Hutchesson]

Walt,

Yes but it pretty messy stuff, you need to get the appropriate
Microsoft DDK and write your own drivers to get access to ring 0
in the operating system.

The drivers are operating system specific and will not work on
other versions usually so unless you have very good reason to do
it, I would see if there is another way of accessing the data you
need.

Regards,

[email protected]

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[Larry Buller]

you can access ports with a bit of assembly in the PBDLL.
FUNCTION INPT (BYVAL inport AS INTEGER) EXPORT AS INTEGER
! mov dx, inport
! in al, dx
! mov function[0], al
END FUNCTION
'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
SUB OUTP (BYVAL outport AS INTEGER, BYVAL dat AS INTEGER) EXPORT
! mov dx, outport
! mov al, dat
! out dx, al
END SUB

This works in Windows 9x, but not in 2000 or NT.


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[Lance Edmonds]

Correct. Win9x does not stop direct hardware access (ie, via inline-assembler, etc) whereas NT/2000 will stop it blind via the HAL layer. To access hardware under NT/2000 requires a Kernel-mode driver to get to Ring-0.

PowerBASIC produces Portable Executable (PE) format files, and these cannot act as kernel-mode drivers.
www.lvr.com hosts a range of freeware and shareware NT/2000 kernel mode drivers to allow hardware access for Ring-3 applications, and they even have some available for Win9x so the Ring-3 code can be written in a less platform-specific manner.



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Lance
PowerBASIC Support
mailto:[email protected][email protected]</A>