[Qemu-devel] OS/2 Bootloader Some weird behaviour of branch instruction

[Tero Kaarlela]

Hi,

   I took a look at qemu in_asm & cpu debugging with OS/2 bootloader 
under Qemu -prep. And there is something weird happening in my opinion:

This happens after boot.cfg has been gone through and kernel bootstrap 
task should start:

IN:
0xf0107068:  .long 0x10009d81
0xf010706c:  tdi    0,r0,27776
0xf0107070:  bl    F011EDF0    <<= Shouldnt this branch to F011EDF0 
instead of going on???
0xf0107074:  .long 0xb2c
0xf0107078:  cmpwi    r0,-32191

After this code branches back to 0x0f0107068(this block start) And does 
this same block again 42 times. Then:

----------------
nip=00000300 super=1 ir=0
translate opcode f01072ac (3c 16 0a)
invalid/unsupported opcode: 3c - 16 - 0a (f01072ac) 0x00000300 0
IN:
0x00000300:  lhau    r3,4336(r18)

----------------
nip=00000700 super=1 ir=0
translate opcode f0000730 (3c 18 1c)
invalid/unsupported opcode: 3c - 18 - 1c (f0000730) 0x00000700 0
IN:
0x00000700:  addic    r0,r7,240


Here is CPU debug from same:

---------------- excp: 0108
nip=0xf0107068 LR=0xf0107010 CTR=0xf01071e0 XER=0x20000000 MSR=0x00010031
GPR00: f01072ac f0000060 00000000 f0170004 00000001 40000000 00000010 
f0004100
GPR08: f0107010 84000023 f0107068 f01071e0 f0000000 f0000300 00000000 
20000000
GPR16: 00000004 38603000 60000000 00000000 0000b588 00000000 001990c7 
00195000
GPR24: 00000000 0000000c 00000041 40010031 00000010 00000000 f0000300 
f0170004
CR: 0x84000023  [ L  G  -  -  -  -  E  EO ] TB: 0x00000000 dd2f1962
FPR00: 6162636465666d00 0000000000000000 0000000000000000 0000000000000000
FPR04: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
FPR08: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
FPR12: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
SRR0 0xf0102700 SRR1 0x00010031 DECR=0x22d0b634
reservation 0x00000000
invalid/unsupported opcode: 3c - 16 - 0a (f01072ac) 0x00000300 0
---------------- excp: 0007
nip=0x00000300 LR=0xf0107010 CTR=0xf01071e0 XER=0x20000000 MSR=0x00010001
GPR00: f01072ac f0000060 00000000 f0170004 00000001 40000000 00000010 
f0004100
GPR08: f0107010 84000023 f0107068 f01071e0 f0000000 f0000300 00000000 
20000000
GPR16: 00000004 38603000 60000000 00000000 0000b588 00000000 001990c7 
00195000
GPR24: 00000000 0000000c 00000041 40010031 00000010 00000000 f0000300 
f0170004
CR: 0x84000023  [ L  G  -  -  -  -  E  EO ] TB: 0x00000000 dd2fbe70
FPR00: 6162636465666d00 0000000000000000 0000000000000000 0000000000000000
FPR04: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
FPR08: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
FPR12: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
SRR0 0xf0107068 SRR1 0x00000031 DECR=0x22d014be
reservation 0x00000000
invalid/unsupported opcode: 3c - 18 - 1c (f0000730) 0x00000700 0


So any ideas what might be reason for this?


Tero Kaarlela