Porting AT&T System V Release 4 to multiple cpus

[Israel Pinkas]

In article <1990Dec28.150334.24778 at sctc.com> briel at sctc.com (Marc Briel ) writes:

> We are currently planning to port AT&T System V Release 4 to a
> proprietary 68030 based platform. We are also considering another port
> to a 486 based platform. Theoretically, how much additional effort is
> required to do the 486 port if the platforms are "identical" except
> for the difference in MPU used?

Not much.  Most of the code is pretty generic.  There are a few routines
written in assembler, primarily for either speed, or to do something that
cannot be done in C.

> How well isolated are the CPU dependencies in AT&T System V Release 4?
> Do almost all of the modules change between a 68030 version and a 486
> version or do only a few modules change?

>From what I know, the source trees are separate.  I don't know why.  I am
involved with a group that is porting SVR4 to the Intel i860.  Our base was
the i386 version.  The i386 version is set up do deal with a large number
of variations.  When building, you specify the bus type (AT, Multibus,
etc.)  and the machine type (for hardware dependencies).  We are treating
all i860 machines (which don't have a bus) as a new bus type, to make life
easier.

We have discovered and fixed a few problems.  These include things like
unaligned accesses (not allowed by the i860) and code speedups.  Everything
is being fed back to AT&T.

> We are licensing the 68030 version source from AT&T. Is there a 486
> version source? How many source modules are identical between the two
> versions. If many of the modules are identical, we can port those
> modules to out 68030 platform first and then just recompile them for
> the 486 (again theoretically).

The 486 version is the same as the i386 version.  It is available from
AT&T, just like any other version.

I can't comment on how much the two versions have in common.  You might
want to ask AT&T, through official cannels.

> I should also point out that System V will run as a "application"
> virtual operating system on top of a proprietry "virtual-machine-like"
> kernel with some unusual characteristics. As a result, we need to make
> modifications to many System V modules that would normally not be
> touched in a "standard UNIX port" even if we start with 68030 version
> source and are porting to a 68030 hardware platform. Since so many
> changes are required, it would be very nice if we didn't have to redo
> all of those changes from scratch on 486 version source. If mostof
> the source modules are identical between the 68030 and 486 versions,
> we can use th same modified source for both versions.

I suspect that most of your changes to the generic 68030 version will be in
the low level device drivers.  We've done something similar here.  We did
the initial i860 port for an i860 card that plugged into an i386 bus.  We
modified the drivers so that instead of accesing H/W, a message was sent to
a daemon on the i386 that accessed the H/W.  This included everything from
disk to mouse.  A virtual machine could probably be done the same way.

-Israel Pinkas
 Intel Corp.
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Disclaimer: The above are my personal opinions, and in no way represent
the opinions of Intel Corporation.  In no way should the above be taken
to be a statement of Intel.

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