x86emu emulation problem

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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...

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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