    The makefile can be adjusted to make a version of adb for
nonseparate I/D machines.  Change the -DNUM_VM_PAGES value to
something like 6 to 8, this will use less real memory (and cause
adb to run a bit slower) and allow adb to run on a non-split I/D 
machine.  

Changes for overlaid processes are intended to work in the most obvious way
and are:

     1.	There is an additional map for an overlay (430 or 431) object
	file, described by the triple (bo,eo,fo).  bo is initialized
	on startup, and the others are changed on setting an overlay.
	This is done automatically if there is an appropriate corefile
	or when a traced subprocess stops, and can be done manually
	(described below).

     2.	There are two additional internal variables set for overlay objects.
	The variable o is the sum of the overlay sizes.  c is the current
	overlay number.  It is set automatically as described above,
	and can be changed manually (#>c).  This changes the overlay
	map (eo and fo) to map in the named overlay.  This affects only
	adb's mapping.

     3.	Although the variable c controls the overlay map, the "register"
	variable "ov" reflects the overlay actually mapped when the
	process stopped (or dumped core).  This value is shown as "ov" 
	in the register list ($r).  It may also be used as other register
	variables, in the "<" and ">" commands.  In the latter case,
	this actually causes the kernel to remap the subprocess, and the
	correct overlay must be mapped to restart the process.  NOTE:
	the kernel routine procxmt must support overlay changes for this
	to work.  The (1982) 2bsd distribution includes the necessary
	changes.

     4.	For text symbols in overlaid objects, the default symbol
	used to find "name" is "~name" rather than "_name".  This
	means that the actual subroutine, rather than its thunk, is
	found.  To examine a thunk, use "_name" explicitly.

     5.	In the overlaid segment, only symbols in the current overlay
	(c) are used in symbolic addresses.  In order to find these
	overlay numbers, the new version of (ov)ld must be used.
	The reason for this is that the previous version of ovld put 
	the overlay number only in symbols for thunks, 
	not in local text symbols.

     6. In order to support breakpoints in overlaid segments, the
	strategy used by adb has been changed slightly.  Breakpoints
	are written into the subprocess immediately when a ":b"
	command is executed, and deleted immediately with ":d".

Changes to support overlaid kernels:

     1.	The user's saved registers are in different places in the
	kernel stack.  They are found relative to the entry u.u_ar0
	in the core file if there is one, with offsets from <sys/reg.h>
	and <sys/user.h>.  If there is no core file,a default is
	used.  This default is defined as UAR0 in defs.h.
*******	UAR0 should be checked whenever the user structure changes.

     2.	There is a new command-line flag, -k, which sets things
	appropriately for the kernel.
        It sets the mapping of the core file appropriately
	for 407, 411 and 430 kernels, and changes the debugger's idea of
	saved register locations.  Thus, $r will print the register
	values saved by dump, and $c will use the saved r5 from low core.

In addition, a number of minor bugs have been fixed.

				Mike Karels
				ucbvax!virus!mike
				Department of Molecular Biology
				University of California, Berkeley
