NetNews Offline 2/NetNews Offline Volume 2.iso/news/comp/sys/amiga/misc-part1/2894

Internet Message Format | 1996-08-05 | 3.5 KB

Path: news.rhrz.uni-bonn.de!zeus!fasten
From: [e-mail] (Bernhard Fastenrath)
Newsgroups: comp.sys.amiga.misc
Subject: Re: OS features
Date: 24 Jan 1996 20:35:57 GMT
Organization: Universit"at Bonn, Informatik Abt. II, R"omerstr. 164, 53117 Bonn
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Michael van Elst ([e-mail]) wrote:
: [e-mail] (Wayne Fisher) writes:

<...>
: >    - new programs' code and data would be protected from access by another
: >      process unless explicitly allowed by the program.

: Kills close to all system functions. You had to write a completely new
: AmigaOS.

Maybe not. Let's say (as you suggested earlier) that some subsystems
(e.g. Intuition) have the permission to read and write any memory region.
Intuition functions would have to check if the pointers received from
process A point into A's memory and, of course, if they are consistent
and don't corrupt Intuition's internal data when used (That's a good piece
of work for the programmers and for Intuition at runtime but I guess it's
possible).
Programs which want to browse internal data structures of Intuition are
either given permission or fail.

<...>
: >"much more"? I don't think a few percentages is "much more".

: You forget that memory protection is nothing if you cannot protect
: the system from invalid parameters to system functions. Most system
: functions however use shared data structures.

How about this: Write access to a data structure shared between a process
and Intutition marks the data structure as dirty and Intuition has to
perform consistency checks again before using it.

: The whole concept of device drivers had to be changed.
: BOOPSI is dead.
: System hooks are dead.

Device drivers would have to be a subsystem with the license to kill
(read/write everything). System hooks would be restricted to programs
which were given special permission.

: >It
: >just means that you can't pass pointers between processes and the
: >machine becomes more stable.

: Unfortunately most parameters are passed by pointers. You do have
: to change everything.

Old programs could use one address space and pass pointers as much as
they want to. Maybe if A calls PutMsg() it gives the receiving process B
the permission to read/write its memory. New programs could
also use PutMsg() but they'd allocate the message from a special pool
and the other task receives only read/write permission for this pool.
The private memory of new programs wouldn't have to be in the global
address space.
Another difference between old and new programs could be that the memory
of old programs must not be swapped while new programs can decide for
each of their pools if it has MEMF_SWAP set or not.

Bernhard

PS.: #define MEMF_PUBLIC 0

--

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Hi, I'm not a signature virus. Why don't you just copy me into your signature?