[U-Boot] disassembler ?

[Peter Barada]

On 05/23/2013 03:49 PM, Albert ARIBAUD wrote:
> Hi Peter,
>
> On Thu, 23 May 2013 15:08:24 -0400, Peter Barada
> <peter.barada at logicpd.com> wrote:
>
>> On 05/23/2013 02:53 PM, Albert ARIBAUD wrote:
>>> Also, I *very* strongly suggest that you integrate *some* debugging
>>> interface, based on *some* industry standard. Seeing as you're working
>>> on a brand new, untested so far, silicon, such a debugging interface
>>> is an absolute must IMO.
>> Ditto here.
>>
>> JTAG (or some other industry debugging standard) allows attaching mature
>> tools (like an Abatron BDI or some such) to not only help verify the
>> state, but develop/debug the code you're writing.  Without such you'll
>> only be able to do a postmortem and inspect memory after the
>> code/processor crash - a much more laborious process...
> One won't even be able to do that, at least not if the inspection is
> done using Bedbug within U-Boot since launching U-boot will, in itself,
> overwrite some of the memory -- and Murphy guarantees that the
> overwritten memory will include the areas needed for a successful
> postmortem.
>
>
If one was lucky maybe.  But who builds schedules around luck?  And yes,
Murphy's a mother...

I was assuming that through some black magic they could get into Bedbug
on reset and use it to inspect memory.  Of course this assumes that
Bedbug and u-boot don't collide, u-boot doesn't try to relocate itself
(or scribble over memory), all of which is extra development that a
JTAG[1] attached debugger would preclude.

A JTAG debugger would allow you to load code directly into memory and
then step through the processor initialization(or supply instructions on
the fly!), low-level startup development that everyone does on a new
processor.  Also by stepping you can see where/when the processor is
about to go off into the weeds many, many, many instructions _before_ it
munches any hope of postmortem debugging.  From experience bringing up
boards w/o JTAG is not only tedious but unpredictable and takes a
loooong time - the extra cost/effort of integrating JTAG (especially
since this is a spanking new processor!) is more than justified by it
reducing both total development time and overall schedule risk...

[1] I use JTAG to mean any industry standard hardware debug/access
method that allows arbitrary execution and inspection/modification of
registers/memory...


-- 
Peter Barada
peter.barada at logicpd.com