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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: Arbitrary Sandbox
Date: Sat, 18 Feb 2012 09:26:42 +0100
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Date: 2012-02-18T09:26:42+01:00
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On Fri, 17 Feb 2012 20:47:36 -0800 (PST), Shark8 wrote:

> You know; I always wondered why they (developers, and OS designers)
> didn't take advantage of segments.

Ineffective, complicated, generally useless?

> I realize that the flat memory model is simpler, in concept, and
> likely the programming community wanted to be able to "just take the
> integer value of the location"... and likely was a "cheap-and-dirty"
> way of handling inter-process communication. But isn't such a layout/
> usage is almost asking for abuse (as you can then just fiddle around
> in memory), and asking for both uncontrolled memory usage (leaks) and
> unauthorized access (like you mentioned about self-modifying code)?

Flat /= von Neumann's. If the question is whether the memory access rights
should be reflected in the structure of the address, then, most likely, the
answer is no.

> Though, that does bring to mind a design question: what is/are the
> best way(s) to handle inter-process communication in a general-purpose
> OS?

That depends on the requirements imposed on such a communication and the
machine architecture, if you have shared memory in mind.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de