[parisc-linux] Single-stepping

[Stan Sieler]

Re:

> I implemented two different single step algorithms for a a _kernel_ debugger
> for hp-ux.  The algorithm used could be chosen by a compile switch, because

BTW, Frank, ask Lee Courtney at MontaVista about Debug/iX ...
we've had kernel debugging and single stepping (except for the interrupt 
control stack and a few other corner cases) for 15+ years.

It's *very* powerful to be able to logon as root (or equivalent) and set
breakpoints within the kernel, hit them, and then single step 
... all on a standard release of the operating system.

> I liked the recovery counter method better than my second method (but had to
> deal with collisions with the other kernel services).  My second method was
> to insert a breakpoint at the target of the single step.  It's a pain to do
> that because of issues with delay slots, branching, and nullification.

Worse yet...the breakpoint mechanism raises hell if you have more than
one CPU :)    You realllly don't want that other CPU to hit the breakpoint!
 
-- 
Stan Sieler                                           sieler@allegro.com
www.allegro.com/sieler/wanted/index.html                  www.sieler.com