support for BookE hardware debug features

[Thiago Jung Bauermann <bauerman@br.ibm.com>]

Hi folks,

This is a heads up message to mention some work we're doing to support
more BookE hardware debug features for userspace debugging under Linux,
which we intend to submit upstream. Perhaps someone out there has input
on this, or even want to help us. :-)

Right now GDB just supports one hardware watchpoint in embedded ppc
processors. We're adding support for:

- one more hardware watchpoint,
- four hardware breakpoints,
- support for the two DVCs (Data Value Compare), which enable
hardware-accelerated conditions for hardware watchpoints,
- two ranged hardware breakpoints,
- one ranged hardware watchpoint.

We're also working on the kernel side of the equation. We'll test it all
on the ppc440 processor.

We don't know yet how we'll extend gdb commands to express the ranged
breakpoints and watchpoints, and the DVCs. For the latter maybe we can
add some intelligence to use the registers if the condition expression
is simple enough, I didn't think much about this yet.
-- 
[]'s
Thiago Jung Bauermann
IBM Linux Technology Center