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Subject: Re: Virtual address Memory Protection Unit
Date: Mon, 25 Jun 2012 13:15:47 +0100 (BST)
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In article <js88hb$p6...@speranza.aioe.org>,
Ivan Godard  <igod...@pacbell.net> wrote:
>
>> I remain amazed at the fiendish contortions that people are prepared
>> to go through just to avoid admitting that the world of computing has
>> changed in the past 40 years, when the solution to this is so simple.
>> Simply abandoning the whole demand paging / TLB model in favour of
>> segment authorities (not x86 segments, of course) eliminates the
>> whole horrible mess for essentially no downside.
>>
>> But, of course, I am totally heretical in regarding the need to
>> replace completely misdesigned, misimplemented and just plain broken
>> software as not a downside :-)
>
>Why not go all the way to caps?

Well, yes, but what I am proposing doesn't actually impact very
much, and could be used to run almost all existing software;
only the most foully misdesigned would need rewriting.  The
trouble with capabilities are that they are incompatible with
the POSIX model, and therefore force major changes.  Yes, I agree
that the POSIX model is broken, but abandoning it is a major
upheaval.


Regards,
Nick Maclaren.