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From: iarocci@eneevax.UUCP (John Iarocci)
Newsgroups: comp.sys.atari.st
Subject: BIOS re-entrancy
Message-ID: <955@eneevax.UUCP>
Date: Tue, 23-Jun-87 14:16:36 EDT
Article-I.D.: eneevax.955
Posted: Tue Jun 23 14:16:36 1987
Date-Received: Thu, 25-Jun-87 03:21:14 EDT
Reply-To: iarocci@eneevax.umd.edu.UUCP (John Iarocci)
Distribution: world
Organization: Amgem, Inc.
Lines: 23

Anyone out there have any experience with making BIOS, XBIOS, and/or GEMDOS
calls recursively?  I'm writing a multi-tasking kernel, and trying to find
a safe way to allow multiple processes access to operating system functions.
My understanding is that upon entry to the BIOS trap routines, registers
are saved in savptr ($4a2).  However, the default save area contains enough
room for only three levels of re-entrancy.  Can this situation be resolved
simply by allocating a larger area of memory and setting savptr to point to
it?

Also, does anyone know if any conflics may arise if a process were preempted
in the middle of the BIOS, only to have another process make a BIOS call,
possibly the same one that was interrupted?  The same question goes for the
XBIOS and GEMDOS.  Thanks in advance for any help you can offer.


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| ARPA : iarocci@eneevax.umd.edu                                              |
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