On 10/5/06, jf simon <jfaslist@xxxxxxxx> wrote:
Hi,
I am trying to use the x86emu code to emulate a PCI ATI Radeon
VGA bios on a powerpc platform (IBM 970 Maple).
The emulation starts OK, but after some time I can see that it is
making a call to a location that is outside of the VGA bios.
Which causes x86emu to emulate whatever rabbish it finds here.
At first I thought that maybe x86emu was emulating the wrong code
(maybe got misaligned in the opcodes). But using the "ndisasm"
x86 disassembler on the original VGA bios showed that x86emu was
emulating the code correctly.
I have also compared PCI traces (collected with a H/W analyser)
ran on the powerpc system and on a AMD64 system (which runs the
VGA BIOS OK) and I can see that x86emu on the powerpc is making
the right PCI accesses to the ATI before it crashes. Which makes
me thing the x86emu is working OK, at least at the beginning.
The problem is on the "call 0xe903" instruction. There is no code
there (code is from c0000:0000 to c0000:0d000 ). Plus there are
those strange opcodes "ENTER 8000,15", which are causing the SP
to go from SP=DFD0, to SP=5fa4 (righ in the code!). I have read
that the ENTER opcode was designed to make for high level
language procedures, and their required stack frame needs. But
0x8000 seems like a lot!
I am really at a loss so as what to do next...
FWIW, many video card bioses mess with PCI registers and the like.
Alex
Thaks for any help,
-jf simon
1- the x86emu trace just before the problem:
cat trace.cpu
c000:68dd a00080 MOV AL,[8000]
AX=0000 BX=01e3 CX=4100 DX=f004 SP=dfd0 BP=0197
SI=0000 DI=0000
DS=0000 ES=c000 SS=c000 CS=c000 IP=68e2 NV UP DI
PL ZR NA PE NC
c000:68e0 04f5 ADD AL,f5
[BP+SI]AL AX=00f5 BX=01e3 CX=4100 DX=f004 SP=dfd0
BP=0197 SI=0000 D
I=0000
DS=0000 ES=c000 SS=c000 CS=c000 IP=68e4 NV UP DI
NG NZ NA PE NC
c000:68e2 0002 ADD ,
AX=00f5 BX=01e3 CX=4100 DX=f004 SP=dfd0 BP=0197
SI=0000 DI=0000
DS=0000 ES=c000 SS=c000 CS=c000 IP=68e8 NV UP DI
NG NZ AC PO CY
c000:68e4 c8008015 ENTER 8000
,15
AX=00f5 BX=01e3 CX=4100 DX=f004 SP=5fa4 BP=dfce
SI=0000 DI=0000
DS=0000 ES=c000 SS=c000 CS=c000 IP=68e9 NV UP DI
NG NZ AC PO CY
c000:68e8 0e PUSH CS
[00c8]AX AX=00f5 BX=01e3 CX=4100 DX=f004 SP=5fa2
BP=dfce SI=0000 D
I=0000
DS=0000 ES=c000 SS=c000 CS=c000 IP=68ed NV UP DI
NG NZ AC PO CY
c000:68e9 0106c800 ADD ,
[BX+SI] AX=00f5 BX=01e3 CX=4100 DX=f004 SP=5fa2 BP=dfce
SI=0000 DI=0000
DS=0000 ES=c000 SS=c000 CS=c000 IP=68f0 NV UP DI
PL NZ NA PE NC
c000:68ed 80100e ADC BYTE PTR ,e
[DI]AX AX=00f5 BX=01e3 CX=4100 DX=f004 SP=5fa2 BP=dfce
SI=0000 DI=0000
DS=0000 ES=c000 SS=c000 CS=c000 IP=68f2 NV UP DI
PL NZ NA PO NC
c000:68f0 0105 ADD ,
AX=00f5 BX=01e3 CX=4100 DX=f004 SP=5fa2 BP=dfce
SI=0000 DI=0000
DS=0000 ES=c000 SS=c000 CS=c000 IP=68f6 NV UP DI
PL NZ NA PE NC
c000:68f2 c800800b ENTER 8000
,b
AX=00f5 BX=01e3 CX=4100 DX=f004 SP=df8a BP=5fa0
SI=0000 DI=0000
DS=0000 ES=c000 SS=c000 CS=c000 IP=68f7 NV UP DI
PL NZ NA PE NC
c000:68f6 0e PUSH CS
[SI]AX AX=00f5 BX=01e3 CX=4100 DX=f004 SP=df88 BP=5fa0
SI=0000 DI=0000
DS=0000 ES=c000 SS=c000 CS=c000 IP=68f9 NV UP DI
PL NZ NA PE NC
c000:68f7 0104 ADD ,
AX=00f5 BX=01e3 CX=4100 DX=f004 SP=df88 BP=5fa0
SI=0000 DI=0000
DS=0000 ES=c000 SS=c000 CS=c000 IP=68fd NV UP DI
PL NZ NA PO NC
c000:68f9 c8008006 ENTER 8000
AX=00f5 BX=01e3 CX=4100 DX=f004 SP=5f7a BP=df86
SI=0000 DI=0000
DS=0000 ES=c000 SS=c000 CS=c000 IP=68fe NV UP DI
PL NZ NA PO NC
c000:68fd 0e PUSH CS
[BP+SI]AX AX=00f5 BX=01e3 CX=4100 DX=f004 SP=5f78
BP=df86 SI=0000 D
I=0000
DS=0000 ES=c000 SS=c000 CS=c000 IP=6900 NV UP DI
PL NZ NA PO NC
c000:68fe 0102 ADD ,
AX=00f5 BX=01e3 CX=4100 DX=f004 SP=5f78 BP=df86
SI=0000 DI=0000
DS=0000 ES=c000 SS=c000 CS=c000 IP=6903 NV UP DI
PL NZ NA PE NC
c000:6900 e80080 CALL e903 !!PROBLEM HERE!!
[BX+SI]AL AX=00f5 BX=01e3 CX=4100 DX=f004 SP=5f76
BP=df86 SI=0000 D
I=0000
DS=0000 ES=c000 SS=c000 CS=c000 IP=e905 NV UP DI
PL NZ NA PE NC
c000:e903 0000 ADD ,
[BX+SI]AL
(x86emu starts emulating bad codes (all zeroes)
AX=00f5 BX=01e3 CX=4100 DX=f004 SP=5f76 BP=df86 SI=0000 D
I=0000
DS=0000 ES=c000 SS=c000 CS=c000 IP=e907 NV UP DI
PL NZ AC PE CY
c000:e905 0000 ADD ,
2- The same code as seen from ndisasm:
000068DA A00080 mov al,[0x8000]
000068DD 04F5 add al,0xf5
000068DF 0002 add [bp+si],al
000068E1 C8008015 enter 0x8000,0x15
000068E5 0E push cs
000068E6 0106C800 add [0xc8],ax
000068EA 80100E adc byte [bx+si],0xe
000068ED 0105 add [di],ax
000068EF C800800B enter 0x8000,0xb
000068F3 0E push cs
000068F4 0104 add [si],ax
000068F6 C8008006 enter 0x8000,0x6
000068FA 0E push cs
000068FB 0102 add [bp+si],ax
000068FD E80080 call 0xe900 <<<<<!!!HERE AGAIN
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