Q about PowerPC new exception processing.

[Sergei Organov]

Eric Valette <valette at crf.canon.fr> writes:
[...]
> > Do we need to switch back to usual method of stack allocation or fix comments
> > in the header?
> 
> I would suggest no to switch back as interrupt stack may need to be
> initialized much more early than what is actually done in rtems...

I thought interrupts are enabled as a result of first context load. And stack
allocation was made before that. What for do we need interrupt stack even
earlier? Am I missing something?

What actually bothers me is the fact of initialization of interrupt stack from 
__rtems_end variable. It seems to be more useful to have separate symbol,
let's say, __rtems_isr_stack (and maybe __rtems_isr_stack_size), that are to
be defined by linker. Having this I can put interrupt stack to whatever memory
region I like (e.g., internal RAM of MPC505). Does it sound reasonable?

> 
> I would change the comments because the defines value exactly describes
> what is done in the code... Compatibility issue is usally an argument
> for people that do not want to improve old code :-) New exception
> management is required to implement either a kenel debugger or RDBG.
> BEside it is also required for new interrupt handling API...

I didn't suggest to switch back to old exception handling code, just to get
space for stack in old way. Besides, I like the new code more than old
one. But the new code itself doesn't depend on the way SPRG1 is initialized,
isn't it?

Thanks in advance.

BR,
Sergei Organov.