Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!udel!mmdf
From: tsarna@polar.bowdoin.edu (Tyler Sarna)
Newsgroups: comp.os.minix
Subject: Re: Virtual addresses
Message-ID: <53697@nigel.ee.udel.edu>
Date: 15 May 91 17:01:22 GMT
Sender: mmdf@ee.udel.edu
Lines: 42

CvW writes:

> I do not know what exactly has been done around -- but:

Do you know if anything has been done?
	
> Future versions of 68K MINIX with MMU have the following features:
> - all processes have virtual addresses starting at zero (or, near zero.
>   It is sensible to leave the first 8K or so unused to trace NIL pointer
>   dereferences)
> - there will be memory protection

My thoughts exactly.

> This does not change the layout of the system binaries, for example.
> These are actually relocated for use at address zero, but there is
> relocation info that allows MM to relocate it. In 68K-MMU-MINIX, you can
> use the same binaries and just ignore the relocation info.

Yes. The kernel can even be written to detect the MMU and run
like normal Minix if it's not present.

> How it is done in practise is under discussion. Opinions go from
> - integrating MM in the kernel
> to
> - leaving MM as it is, but expanding the MM-Kernel interface.

I vote for #2. 

> Surely, FS and MM will have their own address space like every other process,
> most likely, the kernel uses a 'flat' address space.

FS and MM can be flat too. It might be easier.

One thing I'd like is the ability for processes to expand so
that when a process grows past it's chmem'd limit, it just gets
bigger. This could be done with swapping.

--
Tyler "Ty" Sarna                       tsarna@polar.bowdoin.edu

     "Navy. It's not just a job, it's $98.76 a week." -SNL