[OpenBIOS] [Qemu-ppc] FreeBSD powerpc issue

Andreas TObler andreast at fgznet.ch
Sat Aug 25 12:27:20 CEST 2012

On 08/25/12 11:00, Blue Swirl wrote:
> On Fri, Aug 24, 2012 at 9:45 PM, Andreas Tobler <andreast at fgznet.ch> wrote:
>> Hello,
>> I'm trying to get FreeBSD powerpc running with qemu.
>> So far it loads the fbsd loader and the loader loads the kernel.
>> The kernel starts booting but it hangs in an endless loop. It tries to print
>> out a fatal_trap but it looks like the 'of' doesn't work properly (anymore?)
>> at this stage.
>> I have a remote debugger attached to the kernel and I can see where it
>> hangs. But I can not figure out what caused the fatal trap here.
>> An 'info registers' in qemu shows the srr0=fff025a4, this, as I understand,
>> points to of_client_callback from OpenBIOS. (objdump -dS
>> openbios-qemu.nostrip gives me this.)
>> qemu is on 1.1.90, iow, a git snapshot from yesterday with OpenBIOS from
>> 19th of aug.
>> Is there a possibilty to 'debug' the OpenBIOS somehow?
> CCing OpenBIOS list too.
> We have a built-in debugger in OpenBIOS (maybe not well documented).
> Then there's DEBUG_CIF in libopenbios/client.c and it should be
> possible to add debugging print statements to forth/system/ciface.fs
> too.

Oh, thank you. I'll take a look when I'm back on the machine.

>> I'm not sure whether it is a kernel issue or an OpenBIOS issue.
> The problem could be that there's a MMU fault when the kernel calls
> OpenBIOS, maybe because OpenBIOS is no longer mapped (MMU disabled?)
> and then the above debugging would not help.

Hm, from the FreeBSD kernel code view, I passed several 'of' calls to 
read the memory regions etc. to map memory. That said, OB is working 
fine for the start.
I'm not sure where it happens, the fault above. It might be when I start 
to call 'of' again after I have started the MMU on the FreeBSD kernel side.

So, to my understanding, you say it might be an MMU fault, that OB is no 
longer mapped? Who would be the responsible for this mapping, the 
FreeBSD kernel or OB?

Thanks a lot!

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