Subject: Re: compartmentalization of kernel memory
To: Steve Woodford <>
From: John Gordon <>
List: tech-kern
Date: 04/08/2003 14:29:32

> > > Could the 16 protection bits (forgotten what they are called) be used??
> >
> > No, don't try to use the domains system.
> Could you elaborate a little on this statement?

Taken out of context that sounds like a global suggestion not to use the domain
mechanism... in context, it was simply a recommendation not to use them to try
to protect the exception vectors (which was the topic of that particular

The problem with using the domain system is that the domain access control
register is not changed by an exception. So, if the vectors were inaccessible
at the time of the exception, they will remain inaccessible when the CPU tries
to execute the vector instruction(s). That will result in another exception...
and so on, ad infinitum.

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