Re: [GNU-linux-libre] ppc64el support in endorsed distros

[Denis 'GNUtoo' Carikli]

On Fri, 18 May 2018 10:41:41 +0200
Andreas Grapentin <address@hidden> wrote:

Hi,
 
> I have been involved in that a bit, and I think the current problem is
> creating a suitable cross toolchain to start the port in earnest. If
> we had people with experience and ideas in that regard, that might me
> very helpful.
I'm very interested in being able to create arbitrary toolchains from
an FSDG distribution, as I need it to be able to compile older
(ARM) kernels, compile lm32 code for some AMD processor (SMU) present in
AMD CPUs, etc.

== Cross toolchains ==
In Parabola we have crosstool-ng but I didn't spend enough time
on it to successfully create a toolchain.
> $ pacman -sS crosstool
> pcr/crosstool-ng 1.23.0-1.parabola1
>     Versatile (cross-)toolchain generator, with Linux-libre kernel
> support pcr/crosstool-ng-git 1.22.0.r21.g2d3c70d-1.parabola2
>     Versatile cross-toolchain generator, with Linux-libre kernel
> support

Another approach would be to add support for that architecture in Guix
and build the toolchain through that.

I remember seeing compatibility the results of test in tables with
the combination of different versions of glibc, gcc, and binutils for
each architecture. Typcally, with x86, combining most of the
glibc, gcc, and binutils versions will work, whereas you might hit
problematic bugs when you do that for other less-scrutinized
architectures.

In any case, building a toolchain is not enough, you also need it to
work enough to bootstrap enough userspace to be able to boot (and
then be able to build packages and the toolchain on the booted
system).

== Using another distro ==
Another approach would be to use any GNU/Linux distribution (which is
not necessarily FSDG compliant) that supports ppc64 little-endian, run
it in qemu, and with it bootstrap a Parabola for ppc64 little-endian.

In one hand this may seem ethically acceptable[1]:
> But there is one special case where using some nonfree software, and
> even urging others to use it, can be a positive thing. That's when
> the use of the nonfree software aims directly at putting an end to
> the use of that very same nonfree software.

But if you see it with another point of view it might be problematic as
it would be preferable not have to run non-FSDG distributions to port
FSDG distributions to other architectures in general. And porting
Parabola to ppc64 little-endian will not enable to avoid running
non-FSDG distributions when porting to a different architecture.

It would also be nice to be able to create arbitrary toolchains with
FSDG compliant software.

References:
-----------
[1]https://www.gnu.org/philosophy/is-ever-good-use-nonfree-program.html

Denis.

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