Re: [RFA/commit] arm-tdep.c: Do not single-step after hitting a watchpoint

Will Deacon
2014-09-30T09:04:15Z

On Tue, Sep 30, 2014 at 09:57:46AM +0100, Will Deacon wrote:
> On Mon, Sep 29, 2014 at 07:23:05PM +0100, Peter Maydell wrote:
> > Joel Brobecker wrote:
> > > I have been trying to understand the various contributions, and
> > > I admit I am still not quite sure...
> > >
> > > Does it look like the patch I proposed is correct? It seems to be
> > > supported by Terry Guo's experiments as well...
> >
> > Note that the ARMv7 architecture allows watchpoints to
> > be implemented as *asynchronous*, in which case what
> > you will see is that you take a watchpoint exception
> > but it may not fire until after the instruction that
> > triggers the watchpoint and possibly several following
> > instructions have all finished execution. This may be
> > what you are seeing in your hardware tests.
>
> No you won't; the kernel will swallow the async watchpoint and complain in
> dmesg. I'm not aware of any CPU implementations that actually generate
> these.

D'oh, the lack of morning coffee means I missed the fall-through that Pedro
pointed out. I should go find the author of that code...

Will