Re: [Qemu-ppc] [OpenBIOS] MorphOS 4.x on QEMU

[BALATON Zoltan]

On Tue, 4 Mar 2014, BALATON Zoltan wrote:
> Raise exception at 00441bcc => 00000002 (00)
> IN:
> 0x00000300:  b       0xffffc3a0
>
> invalid/unsupported opcode: 00 - 00 - 00 (00000000) ffffc3a0 0
> IN:
> 0xffffc3a0:  .long 0x0
>
> Raise exception at ffffc3a4 => 00000006 (21)
> IN:
> 0x00000700:  mtsprg  2,r2
> 0x00000704:  li      r2,7
> 0x00000708:  b       0xffffe0f0
>
> invalid/unsupported opcode: 00 - 00 - 00 (00000000) ffffe0f0 0
> IN:
> 0xffffe0f0:  .long 0x0
>
> Raise exception at ffffe0f4 => 00000006 (21)
> Raise exception at ffffe0f4 => 00000006 (21)
>
> Something seems to overwrite the vector at 0x300 (which was set to 0x238c 
> before this point) but the new value seems to point to the wrong place.

It seems that this is happening when MorphOS tries to install its own 
exception handlers but something is going wrong during this. What I think 
it does is copying a block of memory with the exception handler vectors 
and then it tries to fix up the jumps in it to point to somewhere but 
either the fixup is not correct or the handlers are not where they are 
expected to be. I'm currently out of ideas how to debug this further.

Regards,
BALATON Zoltan