Re: Ada OS Kernel features

[Ole-Hjalmar Kristensen <ohk@clustra.com>]

"Brian Catlin" <briancatlin@mindspring.com> writes:

> [...snip...snip...]
> 
> > It is possible (and has been done) to associate privileges with the
> > memory segment you are currently executing in, not which process you
> > are running in. In this way it is possible to get both speed and
> > safety, by having special libraries with sufficient privileges. Kind
> > of like the monitor/protected object idea, which lets you execute
> > code within it without process switching.
> 
> Interesting.  Do you have any references to any implementations?  This seems
> that it would work for a small system, such as an RTOS, but I suspect not for a
> large general-purpose operating system.
> 
>  -Brian
> 
> 
> 

Seems my posting did not make it, so I'll try again.  "Transaction
Processing: Concepts and Techniques" by Gray and Reuter has a brief
discussion on pages 64-65.  AS400 is one of the systems mentioned
there, but the System 38 had the same mechanism.  I believe the
concept is discussed other places in the book too.

You probably need some special hardware to do this efficiently,
although the segmentation check hardware in the Intel x86 architecture
could probably be pressed into service.
A pity the 432 never took off.

-- 
Kabelsalat ist gesund.

Ole-Hj. Kristensen