[openpsion] compiler for arm linux 2.4.x kernel via chroot and qemu

[Klaasjan <kla...@gm...>]

Dear list,

Over the past few weeks I have been renewing my interest and experience 
with the openpsion/psilinux kernel source, and compiling and testing it.
Below is a brief summary of the initial steps, hopefully this will raise 
some new/renewed interest.

The first issue was getting a suitable compiler running. It seems the 
2.4 kernels need ancient versions (gcc 2.95 in particular), and 
compiling such an old cross-compiler then requires a chain of compilers 
working backwards from contemporary ones.

Instead, a solution that works for me uses debootstrap, chroot and qemu 
as follows. This seems not only much simpler than installing or building 
a suitable cross-compiler, but also creates a filesystem that is 
suitable for running on your psion device (once you have a booting linux 
kernel).

See below. Feedback appreciated. With enough positive feedback, perhaps 
this should go onto the openpsion website?

Enjoy!
Best,
Klaasjan

*** You need:
- a recent (non-arm!) machine running debian (tested with bullseye), 
with internet access, root access and several GB of free disk space

** On this machine, create a suitable debian arm woody chroot as follows
# most of the below needs to be done as root (use sudo, or sudo -i)

* install the required tools:
- apt install qemu qemu-user-static binfmt-support debootstrap
- update-binfmts --display | grep arm  # this should output:
qemu-arm (enabled):
  interpreter = /usr/libexec/qemu-binfmt/arm-binfmt-P
# also /usr/bin/qemu-arm-static should exist now

* make a filesystem suitable for this old distro (ext2 revision 0)
- dd if=/dev/zero of=./debian-arm-woody.img bs=100M count=20  # creates 
a 2GB file
- mkfs.ext2 -r 0 ./debian-arm-woody.img

* Create a debian distro on the image file (debootstrap first stage)
- losetup -f #  to create /dev/loop devices, only needed if these don't 
exist yet
- mkdir /mnt/debian-arm-woody
- mount -o loop ./debian-arm-woody.img /mnt/debian-arm-woody/
- debootstrap --foreign --arch=arm woody /mnt/debian-arm-woody/ 
http://archive.debian.org/debian/
- cp -i /usr/bin/qemu-arm-static /mnt/debian-arm-woody/usr/bin/
- cp /etc/hosts /mnt/debian-arm-woody/etc/hosts

* Complete initial distro installation (debootsrap second stage)
- chroot /mnt/debian-arm-woody/  /bin/sh
- mount proc /proc -t proc
- /debootstrap/debootstrap --second-stage --keep-debootstrap-dir
# some warnings, like:
apt-config: not found
dpkg: warning, architecture `arm-none' not in remapping table
W: Cannot find binary for checking sha256 checksums, falling back to sha1
I: Installing core packages...
...

* install compiler software
- apt-get install less bison flex gcc
- apt-get install dialog wget bzip2 patch


* check:
- gcc -print-libgcc-file-name
/usr/lib/gcc-lib/arm-linux/2.95.4/libgcc.a

* next steps would be getting a suitable kernel source and try compiling 
it. More detailed instructions for that should probably be a follow-up item.