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From: jesup@steinmetz.UUCP
Newsgroups: comp.sys.amiga
Subject: Re: Networking Amigas + MMU's
Message-ID: <1445@steinmetz.steinmetz.UUCP>
Date: Tue, 14-Apr-87 16:33:08 EST
Article-I.D.: steinmet.1445
Posted: Tue Apr 14 16:33:08 1987
Date-Received: Fri, 17-Apr-87 03:23:57 EST
References: <8704080809.AA04117@cory.Berkeley.EDU> <12822@watnot.UUCP>
Reply-To: jesup@kbsvax.steinmetz.UUCP (Randell Jesup)
Organization: General Electric CRD, Schenectady, NY
Lines: 30

In article <12822@watnot.UUCP> ccplumb@watnot.UUCP (Colin Plumb) writes:
...
>I can't think of any application except debugging that requires access to
>another process's *text* space.  (For non-Unix types, that's where the
>machine code goes... you know, the stuff that's a pain to make relocatable.)
>Anything Mem_Alloc'd can easily be made MEMF_PUBLIC (you *do* use that flag,
>don't you?), and thus globally addressed by all processes.
...
>	-Colin Plumb (watmath!watnot!ccplumb)

	I think this needs to be re-iterated, and pounded into all Amiga
developers heads:  If the memory is to be used by ANYONE else, make it 
MEMF_PUBLIC!  This includes messages, packets, task structures, etc.
It would be nice if it included even the buffers for Read and Write, but
this could be handled transparently, though inefficiently.  (allow the
fileing system to run with everything mapped, and translate the mapped
address to absolute in the Read/Write call before passing the packet to
the filing system.)  The overhead wouldn't be too bad.
	I'm afraid that all Chip memory will have to be public, but that's
life.  At least you won't be able to trash someone elses private code or
data.
	The result of this is a mostly protected system, but since Chip memory
(and Public) are writable, it is still possible to blow other tasks (of
course, if you move read-only structures like libraries and various other such
into public-readonly memory, the consequences should be greatly reduced.)
It DOES greatly reduce the chance of blowing other tasks, though.

	Randell Jesup
	jesup@steinmetz.uucp
	jesup@ge-crd.arpa