Re: [parisc-linux] Single-stepping

[Richard Hirst <rhirst@linuxcare.com>]

On Wed, Nov 15, 2000 at 02:49:02PM -0500, John David Anglin wrote:
> >   I've been helping Alan Modra out with kernel changes to support
> > single stepping for gdb.  Paul Bame suggested I bounced our ideas
> > off you in case you (or anyone else) had any comments.  I havn't
> > actually committed my changes yet.
> > 
> > The basic approach is to use the recovery counter to generate
> > a trap every instruction.  The scheme is complicated because a
> > suspended process may or may not return to user space via an RFI.
> 
> I really don't know enough to comment on the implementation choice.  Why
> did you decide on this approach as opposed to inserting breaks and
> enabling the taken branch branch trap (T)?  It would appear that the recovery
> counter was intended to provide software recovery from hardware faults
> in fault tolerant systems.  Possibly, Grant could comment on whether
> it is actually useful for this purpose.

Alan Modra made those early decisions, but I gather that he went
for the recovery counter because it at least appears to be rather
more straightforward.

Richard