breakpoint insert API (was: A patch for ia32 hardware watchpoint.)

[Richard Earnshaw]

> "J.T. Conklin" wrote:
> 
> > Todd> So I would have to argue that the singlestep logic must either
> > Todd> happen at a really low level (this guarantees it will patch last
> > Todd> and un-patch first) or must go through the real breakpoint logic
> > Todd> which can do duplicate detection.
> > 
> > The SOFTWARE_SINGLE_STEP() macro is called at a low enough level that
> > it inserts and remove trap instructions without effecting GDB's high-
> > level breakpoints.  So I think we're OK.  As a result, I wouldn't be
> > suprised if steping into a breakpoint didn't behave the same as on a
> > machine with hardware single-step.
> 
> Its got long-term problems.
> 
> The code assumes that it is going to retain control, blocked on the
> target, while the actual step is performed.
> This doesn't work well within a pure event model where control is ment
> to return to the event-loop when ever the target is resumed.

It doesn't work properly with INSTRUCTION_NULLIFIED either -- at least it 
didn't last time I tried it...

R.