About the patch to add h/w watchpoint to ppc arch

About the patch to add h/w watchpoint to ppc arch

[Wu Zhou]

Hello maintainers,

We have discussed a lot about this patch.  And I had made some modification
to the original to make it more acceptable.  I am now revisiting the patch
to see whether it is ok to check it in.

The latest patch is at:
  http://sourceware.org/ml/gdb-patches/2005-12/msg00250.html

It addressed the issue of getting the stopped data address. Eli said that it
made sense.  Others didn't replied.  Could I take this as no objection? :-)
Said that, I am still very open to different opinions.  Suggestion for 
improvement are highly appreciated!

I am not sure whether there are any other problems hindering its acceptance.
The patch didn't add anything more to nm.h now(Thanks Mark, Ulrich ... for 
suggesting ways to achieve this); It tested ok on p630(will try to find other
ppc machines to test this); It uses run-time check to see whether kernel
support DABR manipulation or whether target machine have DABR registers.

One issue might be that some 32-bits ppc cpu might have more than one DABRs
(I am not sure which ones have >1 DABRs, Daniel and Anton suggested that). 
But I think that this patch still works ok with any 32-bits ppc models.  
The reason is that the current 32-bits ppc kernel don't support 
PTRACE_SET_DEBUGREG, so the run-time check in ppc_linux_check_watch_resources
will fail and hence there won't be any difference than the unpatched GDB.
Any different opinion on this?

Another issue I can think of is that Anton's patch to return stopped data
address upon DABR hit is not in the upstream kernel yet.  But I believe 
that there won't be many objection for that, provided that it will only
impact debugger behavior. If it is a pre-requirement for this patch to go
into gdb, I can ping Anton to get his patch into kernel first.

Are there any other issues? Maybe some documents or testcase?  If it is
needed, I can add a testcase for rwatch/awatch or some words somewhere.

These are all I can think of at this time.  Did I miss something?  Your 
comments/suggestion are highly appreciated!

Regards
- Wu Zhou

Re: About the patch to add h/w watchpoint to ppc arch

[Ben Elliston]

Hi Wu

> Are there any other issues? Maybe some documents or testcase?  If it
> is needed, I can add a testcase for rwatch/awatch or some words
> somewhere.

I did take a look when I originally wrote the patch and concluded that
there was no need for additional test cases.  The existing ones in the
testsuite seemed to cover things adequately.  Indeed, there were some
progressions in the test results when I applied my patch.

Ben