🚀 go-pugleaf

In article <35789@ut-emx.UUCP> lshaw@walt.cc.utexas.edu (logan shaw) writes:
>
>> Another problem is that even if you provide the possiblity for new
>> applications to run protected within the environment, the fact that older
>> programs can still jog around the address space and wreak havoc, defeats
>> the initial purpose.
>
> But they can't wreak havoc with the memory declared as protected.  Granted,
> it won't be 100% safe, but it will sure be alot better than it is right now.
>
> I was under the impression that (motorola, at least) MMU's worked by setting
> certain memory pages with certain attributes (protected, etc), so the
> programs which asked for protected memory would be protected from everything,
> but older programs wouldn't be protected from newer programs.

Not quite. Protected tasks would still have their TCB in MEMF_PUBLIC memory,
which by definition means "Go ahead, stomp on me!" Ditto for memory lists
message ports, messages, I/O requests, etc. If you cannot provide 100% memory
protection and recoverability, then you might as well not provide it at all.

You might disagree, but remember, I'm always right.  ;-)

> It can't be _that_ difficult to write.  PLEASE can we have this in 2.1?
> Please, please, please? Pretty please with syntactic sugar on top of it?

As I have said before, the technical difficulties are not what is keeping us
from coming out with incredibly useful enhancements. You have to factor in the
energy constant, the resistance ratio and the friction coefficient. I found
out the hard way.

> Just _once_ i'd like to see a requestor like this:
> /---------------------------------------\
> | CLI Process 2 tried to hose Process 3 |
> |                                       |
> | /--------\   /--------\     /-------\ |
> | | Freeze |   | Ignore |     | Reset | |
> | \--------/   \--------/     \-------/ |
> \---------------------------------------/

Indeed, coming out with a fully memory protected operating system which
protects even old software, but remains compatible by presenting one of these
requesters every time an illegal access happens, is technically possible.
But these requesters would pop up several times per second, and would leave
novice users rather confused.

Another option would be to come up with an operating system that provides
full memory protection, but would allow the user to turn it on only optionally.
Easy. But to evaluate the likelyhood of such a thing happening, you have to
factory in the energy constant, the resistance ratio and the friction
coefficient...

Valentin
-- 
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