After Uncompresseing Linux..., what's next

[Gary Thomas]

On Fri, 2002-12-20 at 09:14, Prakash kanthi wrote:
>
> Folks,
>
> I just wanted to provide more info on my env. I have
> PPC405 based board with no network support forcing me
> to use zImage.initrd.elf.
>
> Can you suggest more on my problem described below? I
> saw the memory values at 0x00000000 onwards after
> uncompressing linux and they have changed. But when
> the control jumps to 0x0, my board hangs. I see that
> ESR is showing a value of 0x80000000, meaning either
> illegal instruction or Machine Check.
>
> Can you tell what's going on? What happens next after
> uncompressing? I am thinking it executes start_kernel
> function which calls lock_kernel. Let me know if i am
> wrong.
>

A *lot* happens, even before the first "printk"!

At the point where the kernel is being started, all that
has happened is the basic image has been loaded to low
memory.  The kernel then needs to set up the memory management
(to map things the way it wants to), then perform quite a
lot of initialization, then start up the generic kernel
which will then do things like initialize devices, etc.

Since you just say you have a board (and don't name it),
I assume that you are porting Linux yourself.  In this case,
you'll either need some tools (like the BDI already mentioned)
or a lot of patience.  You'll need to look at how the kernel
is trying to do its work, at least to the point where you can
get to the first "printk" (which comes during the memory 'find'
sequence on the PPC in arch/ppc/mm/ppc_mmu.c).  Once you get
this far, and printk is working, you can then move on and find
out what else needs to be done.


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