Path: utzoo!attcan!uunet!husc6!uwvax!rutgers!columbia!garfield!aronoff
From: aronoff@garfield (Avram Aronoff)
Newsgroups: comp.sys.ibm.pc
Subject: Re: help needed with device driver chai
Message-ID: <5717@columbia.edu>
Date: 19 Jun 88 04:56:09 GMT
References: <39500014@pyr1.cs.ucl.ac.uk>
Sender: nobody@columbia.edu
Reply-To: aronoff@garfield.UUCP (Avram Aronoff)
Organization: Columbia University CS Department
Lines: 28

In article <39500014@pyr1.cs.ucl.ac.uk> awylie@pyr1.cs.ucl.ac.uk writes:
>Can someone out there tell me how to find the beginning of the DOS device
>driver chain?

The following information is from _MS-DOS Papers_ by The Waite Group.
DOS has an undocumented system call, 52H, which returns a pointer to the
"list-of-lists," an array of far pointers to assorted structures. Do
		mov	ah,52h
		int	21h
A far pointer is returned in es:bx. The information contained there is:

typedef struct ListOfLists {
	void far	*DeviceControlBlockHead;
	void far	*SystemFileTableHandlesHead;
	void far	*ClockDriver;
	void far	*ConsoleDriver;
	short		MaximumSectorSize;
	void far	*CacheBufferHead;
	void far	*CurrentDirectoryStructure;
	void far	*SystemFileTableFCBsHead;
	short		SystemFileTableFCBsSize;
	char		DriveCount;
	char		LastDrive;
} LOL;
The NUL device driver begins immediately after the ListOfLists, and the
segment of the first Memory Control Block sits immediately before it.

							Hymie