interesting line in process.c

[Edward Swarthout]

>From Dan Malek:
>
> Paul Mackerras wrote:
> >
> > Which brings up another question that I have been meaning to ask: what
> > is the rationale for adding the dbcr0/1 fields to the ptrace struct
> > for 4xx?
>
> I dunno.  They have also been moving around during the 4xx port.
> I just put them where the folks that send the patches have them.
> I'll take a look at this since gdb is currently broken on 4xx.
> They have to be context switched, and maybe someone though gdb should
> have access to them.....

I bumped into this when I was looking at adding 74xx IABR/DABR support
for hardware breakpoints under gdb.
(see http://lists.linuxppc.org/linuxppc-dev/200108/msg00249.html)

But to really support the 405 (or booke) all 11 (or 12 for booke)
debug breakpoint registers should to be accessible to gdb.

i386 defines debugreg[8] in the thread_struct and gives ptrace access
to it with special restrictions.

I would suggest ppc do the same thing and define a single debug array
in thread_struct which contains the processor specific debug registers
needed to support gdb's use of hardware breakpoints.  New ptrace
numbers (offsets) will need to be defined to access this array.

Ed.Swarthout at motorola.com

** Sent via the linuxppc-dev mail list. See http://lists.linuxppc.org/