Xref: news2.mv.net comp.os.msdos.djgpp:7929
From: Charles Sandmann <sandmann AT clio DOT rice DOT edu>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Memory mapped files using djgpp on DOS
Date: Mon, 19 Aug 1996 19:13:00 CDT
Organization: Rice University, Houston, Texas
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Message-ID: <3219030c.sandmann@clio.rice.edu>
References: <Pine DOT NEB DOT 3 DOT 95 DOT 960818184854 DOT 9877A-100000 AT ananke DOT amu DOT edu DOT pl>
Reply-To: sandmann AT clio DOT rice DOT edu
To: djgpp AT delorie DOT com
DJ-Gateway: from newsgroup comp.os.msdos.djgpp

> So my question is: is there a way to implement mmaped files using PF scheme?

Only under a full DPMI 1.0 provider.  Since only 386MAX advertises to be
a DPMI 1.0 provider, you are pretty much out of luck.  You could modify
CWSDPMI to provide the augmented exception handler frame described in 
DPMI 1.0 which would provide you the CR2 and PTE values.

> How client can make the server reflect PF faults? 

This is a DPMI 1.0 feature, and only supported for uncommitted/readonly
pages.

> Should it be done by directly modifying IDT?

If you have access to the IDT you can do this (like with CWSDPMI for
example) but you will need to plan to run at the appropriate ring and
chain to the previous handler, and will need to find the page tables also.
At one time I planned to write a demo hook showing how to provide the
old GRX type driver page fault graphics, but my interest in DOS hacking
is gone.