🚀 go-pugleaf

I AM HAVING TROUBLE DETERMINING WHERE MY DEVICE DRIVER ENDS IN MEMORY
WHEN IT IS INITIALIZING - I.E. FINDING THE BREAKPOINT TO RETURN TO
DOS.

I need to determine the last paragraph occupied by my drivers code
and data.  Here's my situation:

I have written a block mode device (a special purpose RAM disk) using
Robert Lai's book as a guide.  In particular I have written the
frontend in TASM large model and I link it to Turbo C large model code
for the driver commands (again using Lai's book as a guide).  I plan
to link in a bunch more large model code in the future as this driver
is one day going to implement some network services using our
implementation of the XTP Transfer Protocol.

All the example code in Lai's book uses Tiny model and he uses a TASM
GROUP command to order the segments, putting the CODE segment last in
the executable.  He then calculates the break point for the end of the
driver relative to the last instructions in his CODE segment - this
works well for him since his CODE segment is the last thing in his
executable.

My problem is that I'm working in large model and the linker is
putting CODE first and _BSS last (according to the .map file).  So,
how can I find the segment:offset address of the bottom of the _BSS at
init time so that I can use this address to calculate the break point
for my driver to return to DOS?

My first thought was to look in the PSP, but I come to find that DOS
does not build a PSP for drivers.

At the present time I just add 1000 paragraphs to the bottom of my
code segment and use that as a break address.  It works but it
obviously wastes memory and only works because I know I have far less
than 16K of data below my code - a very poor hack to get me around the
problem.


Any suggestions would be appreciated.  I'd appreciate e-mail responses.
I'll summarize the solutions I get and post them to the net.

Thank you for your time!

-- 
Fraser Street
fraser@Virginia.EDU
University of Virginia
Department of Computer Science