[B2-devel] Use of ExpandMem lowmem?

[Gwenole B. <gb...@di...>]

Hi,

Problem: APD (Apple Personal Diagnostics) crashes at start in 68040
emulation mode under MacOS 8.1. However, it appears to work correctly in
68030+FPU emulation mode. The ROM is still the one from my LC630.

Traceback:

do_handle_screen_fault: unhandled address 0xc054cfff [IP=0x80b20ab]
D0: 7fff7fff D1: 0000a126 D2: 00000126 D3: 00176064
D4: 7fff0000 D5: 01c20000 D6: 00000000 D7: 00000000
A0: 7fff7fff A1: 01d41190 A2: 001ff0fc A3: 7fff7fff
A4: 01c2230c A5: 01fd277a A6: 01d38f86 A7: 01d38f4a
USP=00000000 ISP=01d38f4a MSP=00000000 VBR=00000000
T=00 S=1 M=0 X=1 N=0 Z=0 V=0 C=0 IMASK=0
FP0: 0 FP1: 0 FP2: 0 FP3: 0
FP4: 0 FP5: 0 FP6: 0 FP7: 0
N=0 Z=0 I=0 NAN=0
0002e25a: 2010 6620 48e7 40c0 2f08 MOVE.L (A0),D0
next PC: 0002e25c

Lastest basic blocks executed (most recent first) are copied hereunder.
In other words, exploring why A0 would have the 0x7fff7fff value.

[00000000]-> d68 0002e250 0002e25a
0002e250: 224d                  movea.l a5,a1
0002e252: 2a78 0b7c             movea.l Twitcher2,a5
0002e256: 2008                  move.l  a0,d0
0002e258: 6724                  beq.s   $0002e27e
0002e25a: 2010                  move.l  (a0),d0

[0002e25c]-> d68 02009a20 02009a22
02009a20: 1401                  move.b  d1,d2
02009a22: 4eb0 2591             jsr     ([$00000000,d2.w*4])

[02009a26]-> d68 020099f0 020099fe
020099f0: 2f01                  move.l  d1,-(a7)
020099f2: 2f09                  move.l  a1,-(a7)
020099f4: 3202                  move.w  d2,d1
020099f6: 2f4a 0014             move.l  a2,($0014,a7)
020099fa: 0242 0100             andi.w  #$0100,d2
020099fe: 6620                  bne.s   $02009a20

[02009a00]-> d68 020099b0 020099be
020099b0: 2f0a                  move.l  a2,-(a7)
020099b2: 2f02                  move.l  d2,-(a7)
020099b4: 246f 000a             movea.l ($000a,a7),a2
020099b8: 341a                  move.w  (a2)+,d2
020099ba: 0c42 a800             cmpi.w  #$a800,d2
020099be: 6530                  bcs.s   $020099f0

[020099c0]-> d68 001ff0ec 001ff0fa
001ff0ec: 2078 02b6             movea.l ExpandMem,a0
001ff0f0: 2068 02a8             movea.l ($02a8,a0),a0
001ff0f4: 2628 001c             move.l  ($001c,a0),d3
001ff0f8: 204b                  movea.l a3,a0
001ff0fa: a126                  HandleZone

Any ideas? HandleZone() is in ROM.

PS: Christian, it would be neat if cxmon could resolve the address of low
mem global by name, I currently get:

[001ff0fc]-> m ExpandMem
*** Undefined variable

[001ff0fc]-> m 2b6
As I don't know by heart my table of Low Mem globals, I use mon_lowmem.h.
;-)

Thanks,
Gwenole.