[Vm-dev] Re: SegmentationFault in with OmniBrowser

John M McIntosh johnmci at smalltalkconsulting.com
Tue May 22 18:12:49 UTC 2007

Well a CPU is a bytecode reader in a sense too. When I was working on  
a 68K assembler interface for Ian's squeak compiler I was surprised  
to see
many instructions could be created that were not covered in the op  
code manual. Also I recall in the days of VirtualPC that team  
discovered certain
i386 machine sequences which would effectively crash the microcode,  
anyone recall what that "bug" was.  Certainly I remember patchs being  
loaded on
my linux box to prevent the problem from happening, once it had been  
leaked to the internet.

Lastly if this verify is so perfect, why the Java exploits I read  
about from time to time?

On May 22, 2007, at 11:03 AM, tim Rowledge wrote:

> On 22-May-07, at 10:56 AM, Philippe Marschall wrote:
>> Java has a bytecode verifyer to prevent these problems with zero
>> runtime cost (if you don't count class loading). Squeak could have  
>> the
>> same.
> Absolutely irrelevant to the problem in question. Smalltalk has a  
> 'bytecode verifier' too - it's called the compiler. It too makes  
> sure the bytecodes are suitable as it 'loads' them.
> The problem is that if some *other* tool is generating bytecodes it  
> can make 'bad' ones that will stomp over other objects. Just as in  
> java you could etc etc. At least, I assume java could have a tool  
> to generate bytecodes and run them? I wouldn't really know, never  
> having had anything to do with it.
> tim
> --
> tim Rowledge; tim at rowledge.org; http://www.rowledge.org/tim
> Gotta run, the cat's caught in the printer.

John M. McIntosh <johnmci at smalltalkconsulting.com>
Corporate Smalltalk Consulting Ltd.  http://www.smalltalkconsulting.com

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