Re: Improving Ada's image - Was: 7E7 Flight Controls Electronics

[Marin David Condic <nobody@noplace.com>]

Like I said: The thing that makes operating systems hard to get right 
are not usually language issues. They are related to the asynchronicity 
of events and the complexity of the algorithms involved. Perhaps a 
hypothetical Ada OS might eliminate some errors, but the worst ones are 
not usually an issue of language checks.

Also, because OS's need high efficiency, it is not at all uncommon to 
turn off most of the runtime checks because you really need the 
performance. (Or is someone suggesting that all Ada checks should be 
left in when developing an OS?) Ada can't help with a variety of runtime 
errors unless the checks are left in, so does it really buy enough 
benefit to be able to make claims about how wonderful a theoretical Ada 
OS would be?

MDC



Hyman Rosen wrote:
> Which illustrates that you did not actually bother to read about
> what the problem is. The exploit code (which crashes the kernel,
> so it's not precisely a security violation) involves user code
> which executes a floating-point processor instruction in a signal
> handler that should cause a floating-point exception, immediately
> followed by a system call. I think that the hardware exception
> occurs a little bit later, such that kernel mode has taken over,
> and when the kernel goes to restore the floating-point state, the
> exception finally kicks in and brings it down.
> 
> I suspect the ultimnate fix involves the kernel checking for
> deferred user-mode floating point exceptions so that it can reraise
> them in user mode, but in any case, this has nothing to do with the
> programming language in which the kernel was written - at the point
> of death, it is executing an assembly code insertion.


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Marin David Condic
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