Using LinuxPPC executables on 8xx processors

Using LinuxPPC executables on 8xx processors

[Alan Mimms]

Hi all,

I BELIEVE have seen various folks talk about using LinuxPPC executables
directly on MPC8xx processor targets using some kernel floating point
instruction emulation.  As I recall (I'm too lazy to look it up, as I THINK I'm
remembering right), the notes I saw espoused simply building a kernel with the
math emulation turned on and you could use LinuxPPC executables with no changes.

I don't see how this can be true.

There are two significant (at least!) differences between "real" PowerPC and
the embedded flavor: [1] the floating point unit is not present on 8xx and [2]
the cache line size is 16 on 8xx as opposed to 32 bytes on 6xx/7xx.  The kernel
fix for emulating the floating point instructions appears to be touted as a
soluation for #1, but what about #2?

The ONLY way I can see to get MPC8xx kernels to run applications is to use one
of the prebuilt things from Dan's glibc-1.99, or to build a glibc that has the
cache line size fixed in memset (the fixit scripts like Wolfgang's do this by
moving the PowerPC specific one aside and using the generic one that doesn't
use the cache enhanced zeroing) and in dl-machine.c for the data-to-code
operation needed after mmap-ing libraries.

Am I missing something?

 --
Alan Mimms     Packet Engines, Inc.     Spokane, Washington [99214-0497]
  USA, Earth, Sol, Milky Way, The Local Group, Virgo Supercluster, U0
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Re: Using LinuxPPC executables on 8xx processors

[Graham Stoney]

Alan Mimms writes:
> The ONLY way I can see to get MPC8xx kernels to run applications is to use one
> of the prebuilt things from Dan's glibc-1.99, or to build a glibc that has the
> cache line size fixed in memset (the fixit scripts like Wolfgang's do this by
> moving the PowerPC specific one aside and using the generic one that doesn't
> use the cache enhanced zeroing) and in dl-machine.c for the data-to-code
> operation needed after mmap-ing libraries.

I believe you just answered your own question: You can indeed use dynamically
linked LinuxPPC executables directly on MPC8xx targets. However, you need
to rebuild the shared library they link against at runtime as Wolfgang
describes. Note that memset.S and dl-machine.c are in the shared library, and
not in the dynamically linked executables.

Regards,
Graham

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Re: Using LinuxPPC executables on 8xx processors

[Wolfgang Denk]

In message <20000203052532.A3A581B568@elph.research.canon.com.au>
Graham Stoney writes:
>
> I believe you just answered your own question: You can indeed use dynamically
> linked LinuxPPC executables directly on MPC8xx targets. However, you need
> to rebuild the shared library they link against at runtime as Wolfgang
> describes. Note that memset.S and dl-machine.c are in the shared library, and
> not in the dynamically linked executables.

Well, in fact even the original (for instance LinuxPPC  R4)  binaries
*and*  libraries run pretty stable on the MPC8xx system once you have
the FPU emulation working. It seems that the cache line problem  does
not  show  up most of the time. So if you are running a test environ-
ment, where you occassionally need this tool or another, you may just
ignore this for a while.

However, for a production system which must run stable I recommend to
recompile the included libs and bins with (1) the the cache line size
adjusted and (2) soft-float (or - even better -avoid FP suff at all).


Finally: credit where credit is due. All I did was  putting  together
some  scripts to build the tools and libs - but most of the patches I
include where contributed by other people here on the list.

Wolfgang Denk

--
Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-4596-87  Fax: (+49)-8142-4596-88  Email: wd@denx.de
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Re: Using LinuxPPC executables on 8xx processors

[Marcus Sundberg]

Wolfgang Denk <wd@denx.de> writes:

> Well, in fact even the original (for instance LinuxPPC  R4)  binaries
> *and*  libraries run pretty stable on the MPC8xx system once you have
> the FPU emulation working. It seems that the cache line problem  does
> not  show  up most of the time.

IIRC R4 was not based on glibc2, so I'd expect it to never show up.

//Marcus
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Re: Using LinuxPPC executables on 8xx processors

[Wolfgang Denk]

In message <kfyu2jq34ix.fsf@kieraypc07.p.y.ki.era.ericsson.se>
Marcus Sundberg wrote:
>
> > Well, in fact even the original (for instance LinuxPPC  R4)  binaries
> > *and*  libraries run pretty stable on the MPC8xx system once you have
> > the FPU emulation working. It seems that the cache line problem  does
> > not  show  up most of the time.
>
> IIRC R4 was not based on glibc2, so I'd expect it to never show up.

Of course you are right. I know there was another reason why I  stick
with R4 for the native test environment.

Wolfgang Denk

--
Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-4596-87  Fax: (+49)-8142-4596-88  Email: wd@denx.de
When you die, the first thing you lose is your life. The  next  thing
is the illusions.                       - Terry Pratchett, _Pyramids_

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