Re: [Freedos-kernel] Re: 32RTM bug

[Michael D. <Fre...@de...>]

At 11:12 AM 8/11/2004 +1200, Bart Oldeman wrote:
>On Tue, 10 Aug 2004, Michael Devore wrote:
>
> > Some way or another, it looks 32RTM is unhappy with what is going on with
> > the stack on the call to function 34h.  I don't think the InDOS pointer
> > itself is what causes the failure because the exception can occur during or
> > immediately after return from the Get InDOS simulate call.
>
> >From your story it sounds that the int21 entry code uses too much
>space on the user stack.

Before someone invest too much of their life, I suppose the location could 
be an artefact of the debugger interacting with InDOS, but it doesn't look 
like it.  After RTM goes into (16-bit) protected mode and installs a DPMI 
server, any breakpoints I place with 386SWAT wind up at an IRET (apparently 
because of the dual nature of what IRET does and confused real mode/pmode 
issues with the debugger).  If I breakpoint right before the INT 31h 
simulate real call function, I get the expected IRET.  Placing a breakpoint 
immediately after gets the exception and termination feedback.  Can't see 
how it would be other than that INT 31h function which is the problem.

I tracked down the actual exception location reported.  It's on a REP 
MOVSW, as is very typical.  Possibly occurs in the DPMI interface which 
copies values to/from low memory.  Not much help, that.

And for all I know, this could be a bug in RTM which is masked in MS-DOS 
because of a larger or differently structured stack, or other internal 
image difference.