[RFC] 4xx hardware watchpoint support

[Roland McGrath]

> I would think there would be a different REQUEST value to mean "set a
> hardware breakpoint".  Roland McGrath (cc'd) might be able to tell us
> what other architectures do.

Other architectures don't give a good model to follow.  (If anything,
they just trivally virtualize their own idiosyncratic hardware.)

What I want to see done for this in the future is reviving and
finishing the hw_breakpoint work begun by Alan Stern, and porting
that to each arch's particular hardware features.  On that we'd
build any new interfaces in abstract machine-independent terms,
just describing the constraints of what the hardware can do,
rather than having the user interface involve mimicking hardware
encodings.  (The existing hardware-idiosyncratic ptrace interfaces
would tie into hw_breakpoint for backward compatibility.)


Thanks,
Roland