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From: peters@ti-csl.UUCP
Newsgroups: comp.sys.m68k
Subject: stack backtrace on a 68010
Message-ID: <18534@ti-csl.CSNET>
Date: Mon, 6-Apr-87 20:42:36 EST
Article-I.D.: ti-csl.18534
Posted: Mon Apr  6 20:42:36 1987
Date-Received: Thu, 9-Apr-87 03:48:15 EST
Organization: TI Computer Science Center, Dallas
Lines: 23
Keywords: 68k stack


I am trying to construct a stack backtrace routine to run on a 68010
system we are building (Internal use only.  This is not a product 
announcement.).  I'm after the sort of thing that adb will give
you when you use the $c command.  Unfortunately, all of our Unix
source is for the Vax, so I can't just lift the algorithm from adb.

At any given point in time, the frame pointer (in our case, A6) is pointing
at the previous value of A6, conveniently stored on the stack.
Continuing to unwind the stack, you find the return address of the jsr,
right next to where A6 is pointing now .  Then the fun begins.
Next in line is the top of the previous routine's stack.  The bottom of
the frame can be determined from the place A6 is pointing right now.
Great, we've got the top of the stack and the bottom of the frame for
the previous routine.  Next you need to find the bottom of the stack
(or the top of the frame) so you can distinguish the stack (parameters
to the next routine) from the local variables (the frame of this
routine).  Easier said than done--at least I haven't figured out how to
do it yet.  I just keep bumping into this glob that's part frame and part
stack (and I don't know how much of each).

If anyone out there would care to enlighten me on this subject, I would
be in your debt (figuratively speaking, of course).