Initial cross-bootstrap

Read this if you want to know how I ported Gentoo and/or want to do it yourself.

First I tried using existing arm OABI stages. Two problems. You'll immediately hit #462677. That can possibly be fixed by using kernel >=2.6.25. However one of my goals is minimal intervention in device preinstalled software (initfs, kernel, maemo image). Second: although Gentoo has some documented way of changing CHOST, I don't believe it is possible to perform OABI→EABI migration. Correct me if I'm wrong.

Another interesting approach is to convert maemo image into Gentoo using bootstrap-portage script.

Alternatively, Gentoo could be built from scratch using LFS approach. However this may be hard because of busybox. Actually I managed to build full GNU stack (coreutils, diffutils, etc) to /usr/local on vanilla maemo.

Anyway, I chose cross-compilation.

• existing gentoo installation
• n8x0 tablet
• 4gb sd card
• luck
• free time

Install cross-development tools:

emerge crossdev crossdev-wrappers

Build cross-toolchain:

crossdev -S armv6j-unknown-linux-gnueabi

Create convenient cross-portage infrastructure:

emerge-wrapper --init

Change profile from busybox to fully-powered GNU utils:

rm /usr/armv6j-unknown-linux-gnueabi/etc/make.profile
ln -s /usr/portage/profiles/default/linux/arm/10.0/ /usr/armv6j-unknown-linux-gnueabi/etc/make.profile

Tweak make.conf:

nano /usr/armv6j-unknown-linux-gnueabi/etc/make.conf

My tweaks:

• Remove ~arm from ACCEPT_KEYWORDS¹⁾
• USE='-* zlib minimal unicode ncurses'
• Set CFLAGS (see CFLAGS page)
• Remove FEATURES, VIDEO_CARDS, INPUT_DEVICES, USE_EXPAND and UCLIBC_CPU_DEFAULT

Try to cross-build mininal system (I hope it will pass successfully one day):

emerge-armv6j-unknown-linux-gnueabi -vND system

Los of stuff builds, but libperl fails. It won't build. At all. Even don't try. Emerge all remaining packages that don't depend on libperl with –oneshot.

So. We have minimal gentoo system (without perl).

From your tablet:

Transfer gentoo from build machine:

cd /path/to/gentoo/chroot &&\
  ssh root@<gentoo_host_address> 'cd /usr/armv6j-unknown-linux-gnueabi && tar -czp * -O -' | tar -xvzp

Mount misc system stuff into chroot:

cd /path/to/gentoo/chroot &&\
  mount -t proc proc proc &&\
  mount -o bind /dev dev &&\
  cp -L /etc/resolv.conf etc/resolv.conf

Enter chroot:

chroot /path/to/gentoo/chroot /bin/bash

Wooo-haaa! You're inside your n8x0 gentoo installation!

Remove cross-build related stuff from make.conf (see CFLAGS page):

cat > /etc/make.conf << 'EOF'
CHOST='armv6j-unknown-linux-gnueabi'
CFLAGS='-Os -pipe -march=armv6j -mtune=arm1136jf-s -mfpu=vfp'
CXXFLAGS='${CFLAGS}'
USE='-* zlib minimal unicode ncurses'
EOF

Sync portage tree:

emerge --sync

Build missing stuff from 'system':

emerge -v1 automake

Check that all 'system' built:

emerge -vuND system

Rebuild bash (I got strange failures without this):

emerge -v1 bash

Tweak USE flags in make.conf. I set USE='-ipv6 -fortran'

Reemerge natively gcc/glibc (~15 hours using 'performance' cpu governor). Do not forget to plug in battery charger.

Rebuild natively whole world.

emerge -ve system

Profit! You have fully-functional native arm gentoo chroot.