Re: [MirageOS-devel] Fwd: Mirage ARM port

[Anil Madhavapeddy <anil@xxxxxxxxxx>]

On 19 Apr 2014, at 00:05, Andy Ray <andy.ray@xxxxxxxxxxx> wrote:

>> 
>> I've been looking at the (rather slick) cross compiler tools for
>> FreeBSD and (I think) I have compiled a RaspberryPi kernel and
>> userland which I will now start to test.
>> 
> 
> So firstly I think I missed the "k" in discussions around kFreeBSD...I
> didn't realise OCaml native code wasn't supported on FreeBSD ARM and I
> suppose it is with a Debian userland.
> 

I should have mentioned that the prototype referred to an x86_64 FreeBSD
kernel module backend, with the assumption that the hop to ARM would be
relatively straightforward.  With x86_64, the major downside is the lack
of soft floating point support (since the kernel doesn't save FP registers
across kthread switches).  With ARM, we should be able to use soft-float
and avoid this whole issue.

> Never mind, I pushed ahead and I have 4.01.0 native code compilers at
> least somewhat working with FreeBSD on the Raspberry PI now.  I say
> somewhat because I've barely tested them and had to make some (very
> minor) patches to the OCaml configure system and ARM backend.  None
> the less I haven't seen anything not work as yet.  I also haven't
> tried building the ".opt" compilers but will do soon.

Patches look good -- if you can cook up a trunk patch against 
https://github.com.ocaml/ocaml, I can also test it on OpenBSD/ARMv7
on my Pandaboard (I almost have it booting on my Cubieboard there too).
That should shake out any lurking EABI issues and also ensure that
4.02.0dev has the right patches moving forward.  I'm about to kick
off some large-scale qemu-based ARM bulk builds on trunk, so that
should give it some more testing in the next few months again the
OPAM bulk repository.

> I've been keeping notes and scripts at
> https://github.com/andrewray/mirage-fpga.  I've just put a v0.1
> release up in order to provide opam 1.1 binaries for FreeBSD 10.0
> RELEASE on rPi.
> 
> It's not of much use right now but I intend to push a compiler up to
> opam shortly which should get things going.  Fair play to my rPi which
> has been compiling like a trooper all week to get this far!

I have a bit of a cheeky hack for Travis to build a qemu-ARM chroot
btw: https://github.com/avsm/ocaml/blob/travis/.travis-ci.sh

Might come in handy if you want to use a faster host rather than
the rPi for local builds on Linux.

> My intention is to also provide a binary compiler as per ocamlpro's
> 4.01.0+bin-ocp which should make installing ocaml and opam a much
> nicer experience on these embedded systems.
> 
> Now, one thing I have found and really like is with FreeBSD once
> you've spent all day waiting for perl to compile so wget can use it
> (probably for 1 liner in the makefile...grrrrr) you can:
> 
> $ pkg create [....]
> 
> and get installable binaries.  I have a few compiled and will no doubt
> be generating some more.  If this is likely to be of use to other folk
> then it would be good to share.

Sounds great!  It may be worth investigating using 0install as an
alternative to the 4.01.0+bin-ocp.  I'm a bit wary of distributing
binaries via OPAM as it's not really designed for that use-case,
whereas 0install does only that.  It would just install the compilers
as the system one in that case, so OPAM would still work fine.

-anil

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