[Qemu-devel] Problem with QEMU on PPC

[Qemu-devel] Problem with QEMU on PPC

[Helmar Wodtke]

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Hi,

I want to run x86 code (more specific my FORTH at http://www.printly.de/HelFORTH/ )  with user mode emulation on PPC linux.
I've made some debugging and figured out that the following code (for fasm) does not run:
------------------------------------
format elf executable

entry main

main:
        mov ebx,bla
        inc dword [ebx]
                       
        xor ebx,ebx    
        xor eax,eax
        inc eax    
        int 80h

bla: dd 0
------------------------------------
x86/x86 works fine, so I think this is a bug in PPC version. Also "inc dword [bla[" would work.

Thank you.

Helmar

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Re: [Qemu-devel] Problem with QEMU on PPC

[Johannes Schindelin]

Hi,

On Thu, 4 Nov 2004, Helmar Wodtke wrote:

> I want to run x86 code (more specific my FORTH at
> http://www.printly.de/HelFORTH/ )  with user mode emulation on PPC
> linux. I've made some debugging and figured out that the following code
> (for fasm)
> does not run:

Means segmentation fault? Or does not start? Or does nothing?

> x86/x86 works fine, so I think this is a bug in PPC version. Also "inc
> dword [bla[" would work.

Tip: Enable single stepping, enable all logging (or at least in_asm and
cpu) and then compare between PPC and x86 host. You should get an idea
which insn is causing the glitch.

Hth,
Dscho

Re: [Qemu-devel] Problem with QEMU on PPC

[Helmar Wodtke]

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> Hi,
>
> On Thu, 4 Nov 2004, Helmar Wodtke wrote:
>
> > I want to run x86 code (more specific my FORTH at
> > http://www.printly.de/HelFORTH/ )  with user mode emulation on PPC
> > linux. I've made some debugging and figured out that the following code
> > (for fasm)
> > does not run:
>
> Means segmentation fault? Or does not start? Or does nothing?

It says:

helmar@imac helforth04b $ bin/qemu-i386 hf
()<1234567qemu: uncaught target signal 11 (Segmentation fault) - exiting
helmar@imac helforth04b $ bin/qemu-i386 test
qemu: uncaught target signal 11 (Segmentation fault) - exiting
helmar@imac helforth04b $ 

The first command is my FORTH with some debugging code I added and "test" is the code I send in last mail. BTW: Does the segmentation fault message mean it's the emulator or it's the program?

> > x86/x86 works fine, so I think this is a bug in PPC version. Also "inc
> > dword [bla[" would work.
>
> Tip: Enable single stepping, enable all logging (or at least in_asm and
> cpu) and then compare between PPC and x86 host. You should get an idea
> which insn is causing the glitch.

How? Can you point me to documentation? I dont know structure of QEMU well - as far as I've seen there are a lot optimisations for PCC. I dont understand PPC-assembler and dont like to learn it for this problem (I would implement a C-FORTH instead...).

Bis dann,
Helmar

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Re: [Qemu-devel] Problem with QEMU on PPC

[Johannes Schindelin]

Hi,

On Sat, 6 Nov 2004, Helmar Wodtke wrote:

> helmar@imac helforth04b $ bin/qemu-i386 hf
> ()<1234567qemu: uncaught target signal 11 (Segmentation fault) - exiting
> helmar@imac helforth04b $ bin/qemu-i386 test
> qemu: uncaught target signal 11 (Segmentation fault) - exiting

This means that QEmu tries to access memory which was not mapped, i.e.
something like *(char*)0x0.

> > Tip: Enable single stepping, enable all logging (or at least in_asm and
> > cpu) and then compare between PPC and x86 host. You should get an idea
> > which insn is causing the glitch.
>
> How? Can you point me to documentation? I dont know structure of QEMU
> well - as far as I've seen there are a lot optimisations for PCC. I dont
> understand PPC-assembler and dont like to learn it for this problem (I
> would implement a C-FORTH instead...).

If you look into target-i386/translate.c, and search for CF_SINGLE_INSN,
you will probably know what I mean. Just make the if() succeed all the
time (so that only one insn is translated into one Translated Block).

BTW, PPC-assembler is not that complicated. And I think it'd be good to
squash that bug.

Hth,
Dscho