sigsev in 64/32 bit VM

Martin Kuball martinkuball at
Tue May 30 20:19:02 UTC 2006

Am Monday, 29. May 2006 23:43 schrieb tim Rowledge:
> On 29-May-06, at 12:51 PM, Martin Kuball wrote:
> >>>> I examined the arguments to longAtput and they seem OK. But
> >>>> there is no Memory mapped at sqMemoryBase. How could that
> >>>> happen?
> >>>>
> >>>> Martin
> >>>
> >>> Forgot to give you some more details. I'm running a amd64
> >>> system with linux 2.6.14. Compiler ist gcc 4.0.3.
> If there is no memory mapped at a fundamental address like
> sqMemoryBase that implies to me that some very serious has failed,
> and I think it must surely have failed right at the beginning of
> starting Squeak. You didn't mention anything about whether the
> system started up or not, what you were doing, or anything that
> might help us.
> sqMemoryBase is typically set right at the beginning of the VM
> startup, by allocating the memory for the image so if for some
> strange reason that fails you could be in trouble. It's hard to
> imagine how the allocate could fail and not be detected though.


I compiled a VM with BallonEngine, BitBlitSimulation and FilePlugin.
I started the vm in gdb and checked the allocation of the memory. All 
went well. The reason I reported a bad memory region earlier is that 
sqMemoryBase is the real base - 16.
Now the interpreter loop runs and at its 12th cylce (opcode 134) I 
still get the SIGSEV. Further investigation showed that 
foo->stackPointer is the culprit. All the cycles before it had a 
value of 15723512. But this time the value is 1509280732. Really bad. 
I will try to find out where this change happens tomorrow.

By the way when compiling I see a lot of warnings like this one:

	warning: cast from pointer to integer of different size

I'm not sure if it is save to ignore them.

The reason I did not mention anything about system startup is that 
nothing unusual happend. And it's not the the first time I build a 
VM. I even have an 64/32 bit VM working here. But it's almost 1 year 
old and has no network support. Because of that and because I plan to 
resume work on my xvid plugin I want something more up to date.


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