Re: support for BookE hardware debug features

[Sérgio Durigan Júnior <sergiodj at linux dot vnet dot ibm dot com>]

On Sun, 2009-05-24 at 16:38 -0300, Thiago Jung Bauermann wrote:

> I implemented a "watch-range" command, which takes a start address (or
> expression which evaluates to an address) and an end address (or
> expression). Not sure if I'll keep it that way or change. Didn't think
> much about it yet.

Just to complement (I don't know if it's worth mentioning, but
anyway...) it seems we may have found a little bug regarding
watchpoint's expression evaluation.  Basically, the problem was
occurring when GDB tried to see if a block of memory changed in order to
determine whether it should trigger the watchpoint.  GDB was basically
comparing the address of this memory region, and not the content itself,
which made it impossible to trigger the watchpoint.

Unfortunately, I don't have much details about this fix, but I think
Thiago can explain more (if needed).  Also, IIUC, this fix is not
related to the job we're doing so we could send it before we're able to
send other patches :-).

> We are just starting to work on the DVC (conditioned hw watchpoint), but
> for now I'm inclined to use it automagically for simple expressions with
> just one == or != operator. We're taking into account Joel's comments
> and suggestions on this. Thanks Joel for your input!

That is what I was thinking, too.  I don't know if it's possible to use
the DVC registers for more complex expressions, do you?

> Sérgio did most of the work here. I don't know if he wants to add
> anything to this report...

Thank you, the report is very good!

Regards,

-- 
Sérgio Durigan Júnior
Linux on Power Toolchain - Software Engineer
Linux Technology Center - LTC
IBM Brazil