12 KiB
12 KiB
Debugging Notes
Checkpoint
This code:
F000:F9E9 B000 MOV AL,00
F000:F9EB E620 OUT 20,AL
triggers the following warning:
notice: PIC0(0x20): unsupported OCW2 automatic EOI command: 0x00
and the very next instruction:
F000:F9ED E6A0 OUT A0,AL
triggers the same warning:
notice: PIC1(0xA0): unsupported OCW2 automatic EOI command: 0x00
Checkpoint
There's a loop at F000:B5AA that stores 0x4000 DWORDs into RAM (ie, 64Kb), where each DWORD is a single-bit left rotation of the preceding DWORD. This is followed by another loop that loads each DWORD and verifies that it contains the appropriate bit.
Then a stack is set up in RAM (at 0030:0100) and the first CALL is issued:
F000:BC2E E87DEC CALL A8AE
There's some CMOS I/O activity, serial and parallel port I/O, more CMOS I/O, and then some EGA I/O.
When arrive here:
C000:016D B80700 MOV AX,0007
C000:0170 CD10 INT 10
and we complain that the IDTR limit for the real-mode IDT isn't 0x3FF (it's been set to 0xFFFF instead). That may be OK, but I need to verify that that's what the ROM intended. If it is, then I'll probably need to change our assertion from "cpu.addrIDTLimit == 0x03FF" to "cpu.addrIDTLimit >= 0x03FF".
Checkpoint
The BIOS now progresses as far as F000:F747 (PUSH GS).
Checkpoint
The BIOS now progresses as far as 0030:8618 (MOV AX,GS).
Checkpoint
The BIOS now progresses to a Compaq memory-mapped write operation:
stopped (27129586 ops, 2209813 cycles, 361 ms, 6121366 hz)
EAX=000098FC EBX=0000E000 ECX=00000000 EDX=00000000
ESP=000000E4 EBP=00000000 ESI=0000FFFF EDI=00007FBE
SS=0028[00000300,FFFF] DS=0050[80C00000,FFFF] ES=0048[00FF0000,FFFF]
CS=0030[000F0000,FFFF] FS=0000[00000000,FFFF] GS=0304[00003040,FFFF]
LD=0000[00000000,0000] GD=[0001C000,005F] ID=[000FF821,0007] TR=0000 A20=ON
CR0=0000FFF1 CR2=00000000 CR3=00000000 PS=00000083 V0 D0 I0 T0 S1 Z0 A0 P0 C1
0030:8637 C6060000FC MOV [0000],FC ;history=1
and then gets stuck loading CS:IP of 0x28:0xF4AC:
assertion failure in deskpro386.cpu386
Fault 0x0D blocked by Debugger
stopped (27572151 ops, 443210 cycles, 340635 ms, 1301 hz)
EAX=0000FFF1 EBX=00000080 ECX=0000270F EDX=0000004A
ESP=000000FE EBP=00000000 ESI=00007FB6 EDI=00008000
SS=0030[00000300,FFFF] DS=0040[00000400,FFFF] ES=0000[00000000,FFFF]
CS=F000[000F0000,FFFF] FS=0000[00000000,FFFF] GS=0304[00003040,FFFF]
LD=0000[00000000,0000] GD=[00FF0730,0047] ID=[00000000,FFFF] TR=0000 A20=OFF
CR0=0000FFF1 CR2=00000000 CR3=00000000 PS=00000082 V0 D0 I0 T0 S1 Z0 A0 P0 C0
F000:F4A7 EAACF42800 JMP 0028:F4AC
Here's the code leading up to it:
F000:F494 B000 MOV AL,00 ;history=8
F000:F496 E680 OUT 80,AL ;history=7
F000:F498 2E CS: ;history=6
F000:F499 0F01167E07 LGDT [077E] ;history=5
F000:F49E 0F2000 MOV EAX,CR0 ;history=4
F000:F4A1 0D0100 OR AX,0001 ;history=3
F000:F4A4 0F2200 MOV CR0,EAX ;history=2
F000:F4A7 EAACF42800 JMP 0028:F4AC ;history=1
%00FF073C 92C0 8000 FFFF 0000 - 9200 0000 FFFF 0000 ................
%00FF074C 9A0F 0000 FFFF 0000 - 9200 C000 FFFF 0000 ................
id physaddr blkaddr used size type id physaddr blkaddr used size type
-------- --------- -------- ------ ------ ---- -------- --------- -------- ------ ------ ----
00040006 %00000000: 00000000 0x8000 0x8000 RAM 00040006 %00000000: 00000000 0x8000 0x8000 RAM
00040008 %00008000: 00008000 0x8000 0x8000 RAM 00040008 %00008000: 00008000 0x8000 0x8000 RAM
0004000A %00010000: 00010000 0x8000 0x8000 RAM 0004000A %00010000: 00010000 0x8000 0x8000 RAM
0004000C %00018000: 00018000 0x8000 0x8000 RAM 0004000C %00018000: 00018000 0x8000 0x8000 RAM
0004000E %00020000: 00020000 0x8000 0x8000 RAM 0004000E %00020000: 00020000 0x8000 0x8000 RAM
00040010 %00028000: 00028000 0x8000 0x8000 RAM 00040010 %00028000: 00028000 0x8000 0x8000 RAM
00040012 %00030000: 00030000 0x8000 0x8000 RAM 00040012 %00030000: 00030000 0x8000 0x8000 RAM
00040014 %00038000: 00038000 0x8000 0x8000 RAM 00040014 %00038000: 00038000 0x8000 0x8000 RAM
00040016 %00040000: 00040000 0x8000 0x8000 RAM 00040016 %00040000: 00040000 0x8000 0x8000 RAM
00040018 %00048000: 00048000 0x8000 0x8000 RAM 00040018 %00048000: 00048000 0x8000 0x8000 RAM
0004001A %00050000: 00050000 0x8000 0x8000 RAM 0004001A %00050000: 00050000 0x8000 0x8000 RAM
0004001C %00058000: 00058000 0x8000 0x8000 RAM 0004001C %00058000: 00058000 0x8000 0x8000 RAM
0004001E %00060000: 00060000 0x8000 0x8000 RAM 0004001E %00060000: 00060000 0x8000 0x8000 RAM
00040020 %00068000: 00068000 0x8000 0x8000 RAM 00040020 %00068000: 00068000 0x8000 0x8000 RAM
00040022 %00070000: 00070000 0x8000 0x8000 RAM 00040022 %00070000: 00070000 0x8000 0x8000 RAM
00040024 %00078000: 00078000 0x8000 0x8000 RAM 00040024 %00078000: 00078000 0x8000 0x8000 RAM
00040026 %00080000: 00080000 0x8000 0x8000 RAM 00040026 %00080000: 00080000 0x8000 0x8000 RAM
00040028 %00088000: 00088000 0x8000 0x8000 RAM 00040028 %00088000: 00088000 0x8000 0x8000 RAM
0004002A %00090000: 00090000 0x8000 0x8000 RAM 0004002A %00090000: 00090000 0x8000 0x8000 RAM
0004002C %00098000: 00098000 0x8000 0x8000 RAM 0004002C %00098000: 00098000 0x8000 0x8000 RAM
00040088 %000B8000: 000B8000 0x8000 0x8000 VIDEO 000400A0 %000B8000: 000B8000 0x8000 0x8000 VIDEO
00040002 %000C0000: 000C0000 0x4000 0x8000 ROM 00040002 %000C0000: 000C0000 0x4000 0x8000 ROM
0004003F %000E0000: 000E0000 0x???? 0x8000 ROM
00040041 %000E8000: 000E0000 0x???? 0x8000 ROM
00040004 %000F0000: 000F8000 0x8000 0x8000 ROM 00040043 %000F0000: 000E0000 0x???? 0x8000 ROM
00040004 %000F8000: 000F8000 0x8000 0x8000 ROM 00040045 %000F8000: 000E0000 0x???? 0x8000 ROM
00040048 %00100000: 00100000 0x8000 0x8000 RAM 00040048 %00100000: 00100000 0x8000 0x8000 RAM
0004004A %00108000: 00108000 0x8000 0x8000 RAM 0004004A %00108000: 00108000 0x8000 0x8000 RAM
0004004C %00110000: 00110000 0x8000 0x8000 RAM 0004004C %00110000: 00110000 0x8000 0x8000 RAM
0004004E %00118000: 00118000 0x8000 0x8000 RAM 0004004E %00118000: 00118000 0x8000 0x8000 RAM
00040050 %00120000: 00120000 0x8000 0x8000 RAM 00040050 %00120000: 00120000 0x8000 0x8000 RAM
00040052 %00128000: 00128000 0x8000 0x8000 RAM 00040052 %00128000: 00128000 0x8000 0x8000 RAM
00040054 %00130000: 00130000 0x8000 0x8000 RAM 00040054 %00130000: 00130000 0x8000 0x8000 RAM
00040056 %00138000: 00138000 0x8000 0x8000 RAM 00040056 %00138000: 00138000 0x8000 0x8000 RAM
00040058 %00140000: 00140000 0x8000 0x8000 RAM 00040058 %00140000: 00140000 0x8000 0x8000 RAM
0004005A %00148000: 00148000 0x8000 0x8000 RAM 0004005A %00148000: 00148000 0x8000 0x8000 RAM
0004005C %00150000: 00150000 0x8000 0x8000 RAM 0004005C %00150000: 00150000 0x8000 0x8000 RAM
0004005E %00158000: 00158000 0x8000 0x8000 RAM 0004005E %00158000: 00158000 0x8000 0x8000 RAM
00040060 %00160000: 00160000 0x8000 0x8000 RAM 00040060 %00160000: 00160000 0x8000 0x8000 RAM
00040062 %00168000: 00168000 0x8000 0x8000 RAM 00040062 %00168000: 00168000 0x8000 0x8000 RAM
00040064 %00170000: 00170000 0x8000 0x8000 RAM 00040064 %00170000: 00170000 0x8000 0x8000 RAM
00040066 %00178000: 00178000 0x8000 0x8000 RAM 00040066 %00178000: 00178000 0x8000 0x8000 RAM
00040068 %00180000: 00180000 0x8000 0x8000 RAM 00040068 %00180000: 00180000 0x8000 0x8000 RAM
0004006A %00188000: 00188000 0x8000 0x8000 RAM 0004006A %00188000: 00188000 0x8000 0x8000 RAM
0004006C %00190000: 00190000 0x8000 0x8000 RAM 0004006C %00190000: 00190000 0x8000 0x8000 RAM
0004006E %00198000: 00198000 0x8000 0x8000 RAM 0004006E %00198000: 00198000 0x8000 0x8000 RAM
00040070 %001A0000: 001A0000 0x8000 0x8000 RAM 00040070 %001A0000: 001A0000 0x8000 0x8000 RAM
00040072 %001A8000: 001A8000 0x8000 0x8000 RAM 00040072 %001A8000: 001A8000 0x8000 0x8000 RAM
00040074 %001B0000: 001B0000 0x8000 0x8000 RAM 00040074 %001B0000: 001B0000 0x8000 0x8000 RAM
00040076 %001B8000: 001B8000 0x8000 0x8000 RAM 00040076 %001B8000: 001B8000 0x8000 0x8000 RAM
00040078 %001C0000: 001C0000 0x8000 0x8000 RAM 00040078 %001C0000: 001C0000 0x8000 0x8000 RAM
0004007A %001C8000: 001C8000 0x8000 0x8000 RAM 0004007A %001C8000: 001C8000 0x8000 0x8000 RAM
0004007C %001D0000: 001D0000 0x8000 0x8000 RAM 0004007C %001D0000: 001D0000 0x8000 0x8000 RAM
0004007E %001D8000: 001D8000 0x8000 0x8000 RAM 0004007E %001D8000: 001D8000 0x8000 0x8000 RAM
00040080 %001E0000: 001E0000 0x8000 0x8000 RAM 00040080 %001E0000: 001E0000 0x8000 0x8000 RAM
00040082 %001E8000: 001E8000 0x8000 0x8000 RAM 00040082 %001E8000: 001E8000 0x8000 0x8000 RAM
00040084 %001F0000: 001F0000 0x8000 0x8000 RAM 00040084 %001F0000: 001F0000 0x8000 0x8000 RAM
00040086 %001F8000: 001F8000 0x8000 0x8000 RAM 00040086 %001F8000: 001F8000 0x8000 0x8000 RAM
0004002E %00FA0000: 00FA0000 0x8000 0x8000 RAM 0004002E %00FA0000: 00FA0000 0x8000 0x8000 RAM
00040030 %00FA8000: 00FA8000 0x8000 0x8000 RAM 00040030 %00FA8000: 00FA8000 0x8000 0x8000 RAM
00040032 %00FB0000: 00FB0000 0x8000 0x8000 RAM 00040032 %00FB0000: 00FB0000 0x8000 0x8000 RAM
00040034 %00FB8000: 00FB8000 0x8000 0x8000 RAM 00040034 %00FB8000: 00FB8000 0x8000 0x8000 RAM
00040036 %00FC0000: 00FC0000 0x8000 0x8000 RAM 00040036 %00FC0000: 00FC0000 0x8000 0x8000 RAM
00040038 %00FC8000: 00FC8000 0x8000 0x8000 RAM 00040038 %00FC8000: 00FC8000 0x8000 0x8000 RAM
0004003A %00FD0000: 00FD0000 0x8000 0x8000 RAM 0004003A %00FD0000: 00FD0000 0x8000 0x8000 RAM
0004003C %00FD8000: 00FD8000 0x8000 0x8000 RAM 0004003C %00FD8000: 00FD8000 0x8000 0x8000 RAM
0004003E %00FE0000: 00FE0000 0x8000 0x8000 RAM 0004003E %00FE0000: 00FE0000 0x8000 0x8000 RAM
00040040 %00FE8000: 00FE8000 0x8000 0x8000 RAM 00040040 %00FE8000: 00FE8000 0x8000 0x8000 RAM
00040042 %00FF0000: 00FF0000 0x8000 0x8000 RAM 00040042 %00FF0000: 00FF0000 0x8000 0x8000 RAM
00040044 %00FF8000: 00FF8000 0x8000 0x8000 RAM 00040044 %00FF8000: 00FF8000 0x8000 0x8000 RAM
00040046 %80C00000: 80C00000 0x0001 0x8000 H/W 00040046 %80C00000: 80C00000 0x0001 0x8000 H/W
00040004 %FFFF0000: 000F8000 0x8000 0x8000 ROM 00040004 %FFFF0000: 000F8000 0x8000 0x8000 ROM
00040004 %FFFF8000: 000F8000 0x8000 0x8000 ROM 00040004 %FFFF8000: 000F8000 0x8000 0x8000 ROM
But when we stopped here next, it was no longer good:
breakpoint hit: F000:F498 (exec)
stopped (27572162 ops, 443166 cycles, 143 ms, 3099063 hz)
EAX=0000FF00 EBX=00000080 ECX=0000270F EDX=0000004A
ESP=000000FE EBP=00000000 ESI=00007FB6 EDI=00008000
SS=0030 DS=0040 ES=0000 FS=0000 GS=0304 PS=00000046 V0 D0 I0 T0 S0 Z1 A0 P1 C0
F000:F498 2E CS:
F000:F499 0F01167E07 LGDT [077E]
F000:077E 0047 0730 00FF FFFF - 0000 0000 87AA 0018 G.0.............
F000:078E 87F8 0018 8828 0018 - 0F2E 1601 0778 200F ....(.......x..
%00FF0730 0000 0000 0000 0000 - 0000 0000 0000 0000 ................
%00FF0740 0000 0000 0000 0000 - 0000 0000 0000 0000 ................
Turns out this is because the A20 line has been disabled.