Re: [PATCH 0/6] S390: Watchpoint enhancements and hardware breakpoints

Pedro Alves
2016-09-16T15:43:52Z

On 09/16/2016 01:43 PM, Ulrich Weigand wrote:
> Pedro Alves wrote:

>> I'm curious on the need to disable hw breakpoints when single-stepping.
>
> This is more of a hardware restriction than a GDB issue. The problem is
> that s390 hardware doesn't really have a separate hardware single-step
> feature; to implement ptrace single-stepping, the kernel uses the s390
> hardware breakpoint feature (in effect, enabling hardware breakpoints
> on the full address space, which will hit on the next instruction that
> is executed).
>
> This use of the feature by kernel single-stepping can conflict with
> explicit use of the same feature by GDB; that's why it is better to
> not attempt such explicit use while at the same time also requesting
> kernel single-stepping.

I see. Thanks for the clarification.

A comment to the effect in the code would be nice. Maybe it's
there and I missed it.

I have no further comments on the series. LGTM.

Thanks,
Pedro Alves