KDB updates

[Anton Blanchard]

> -- When started with 'startKDB' it seems to work, but when started via
>    'little yellow button', the 'go' command doesn't seem to be handled.
>    It seems like the linux kernel oops handler also wants to run, and
>    that handler doesn't correctly handle the system reset interrupt,
>    at which point the machine powers off.  (That's wrong, the system
>    reset interrupt is fully recoverable, and the debugger should allow
>    system to resume where it was before the system reset.)
>
>    I think the bug is related to arch/ppc64/kernel/traps.c:173
>       if (!debugger(regs))
>       die("System Reset", regs, 0);
>
>    Either those lines are wrong, or kdb should be returning a non-zero
>    return code, I'm not sure which.

Its a feature. xmon now has the ability to recover from any exception,
eg if you get a NULL pointer deref you can fix the instruction and retry
it.

x will exit and retry, X will exit and pass the error on (ie it will
oops). It might be useful if kdb got this technology.

Anton

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