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Chromebook minimal busybox installation

Install a minimal busybox installation on an ASUS C200M Chromebook (Baytrail). This model does not have yet a working SEABIOS version, so we use the chrome normal booting method to boot our own custom kernel.

Generate keys

openssl genrsa -F4 4096 > key.pem
openssl req -batch -new -x509 -key key.pem > key.crt
dumpRSAPublicKey -cert key.crt > key.keyb

futility vbutil_key --pack key.vbpubk  --key key.keyb --algorithm 8 --version 1
futility vbutil_key --pack key.vbprivk --key key.pem  --algorithm 8
futility vbutil_keyblock --pack key.keyblock --datapubkey key.vbpubk --flags 15

Kernel

curl -O https://kernel.org/pub/linux/kernel/v4.x/testing/linux-4.0-rc7.tar.xz
tar xvf linux-4.0-rc7.tar.xz
cd linux-4.0-rc7
make mrproper
cp ../config-kernel .config
ARCH=x86_64 make nconfig
ARCH=x86_64 make -j4

Build the kernel partition

echo 'root=PARTUUID=%U/PARTNROFF=1 quiet' > cmdline
futility vbutil_kernel --pack   kern.bin --keyblock key.keyblock --signprivate key.vbprivk --version 1  --config cmdline --vmlinuz linux-4.0-rc7/arch/x86_64/boot/bzImage
scp -i ~/.ssh/testing_rsa kern.bin  [email protected]:/root

Set partition as bootable

dd if=kern.bin of=/dev/mmcblk0p6
cgpt add -i 6 -S 0 -T 1 -P 5 /dev/mmcblk0

Sysroot

mkdir -p sys-dev/{include,lib}
mkdir -p sys/{bin,boot,dev,etc,lib,mnt,proc,root,sbin,sys,tmp}
cp rcS sys/etc
cp fstab sys/etc
cp udhcpc.sh sys/usr/share
# TODO keymap
# TODO profile
ln -s /tmp/resolv.conf sys/etc/resolv.conf
ln -s /proc/mounts sys/etc/mtab

Busybox

curl -O http://busybox.net/downloads/busybox-1.23.2.tar.bz2
tar xvf busybox-1.23.2.tar.bz2 
cd busybox-1.23.2
make menuconfig
make -j8 CC=musl-gcc
make CC=musl-gcc CONFIG_PREFIX=../sys install

kexec-tools

curl -O https://kernel.org/pub/linux/utils/kernel/kexec/kexec-tools-2.0.9.tar.xz
tar xvf kexec-tools-2.0.9.tar.xz
cd kexec-tools-2.0.9
CC=musl-gcc CFLAGS="-Dloff_t=off_t -Os" LDFLAGS=-static ./configure 
make -j8
strip build/sbin/kexec
cp build/sbin/kexec ../sys/bin

util-linux

curl -O https://www.kernel.org/pub/linux/utils/util-linux/v2.26/util-linux-2.26.tar.xz
tar xvf util-linux-2.26.tar.xz
cd util-linux-2.26
CC=musl-gcc CFLAGS=-Os ./configure --disable-all-programs --enable-libuuid --enable-libblkid
make -j8
mkdir -p ../sys-dev/include/{uuid,blkid}
cp .libs/libuuid.a .libs/libblkid.a ../sys-dev/lib
cp libuuid/src/uuid.h ../sys-dev/include/uuid
cp libblkid/src/blkid.h ../sys-dev/include/blkid

zlib

curl -O http://zlib.net/zlib-1.2.8.tar.gz
tar xvf zlib-1.2.8.tar.gz
cd zlib-1.2.8
CC=musl-gcc ./configure --static
make -j8
cp zlib.h zconf.h ../sys-dev/include
cp libz.a ../sys-dev/lib

lzo

curl -O http://www.oberhumer.com/opensource/lzo/download/lzo-2.09.tar.gz
tar xvf lzo-2.09.tar.gz
cd lzo-2.09
CC=musl-gcc CFLAGS=-Os LDFLAGS=-static ./configure
make -j8
cp src/.libs/liblzo2.a ../sys-dev/lib
cp -a include/lzo ../sys-dev/include

btrfs-progs

git clone git://git.kernel.org/pub/scm/linux/kernel/git/kdave/btrfs-progs.git
cd btrfs-progs
git checkout -b v3.19.1 v3.19.1
./autogen.sh
CC=musl-gcc CFLAGS='-I../sys-dev/include -Os' LDFLAGS='-static -L../sys-dev/lib/' ./configure --disable-documentation --disable-convert --disable-backtrace
# Remove /usr/lib from the generated Makefile
make -j8
strip btrfs mkfs.btrfs
cp btrfs mkfs.btrfs ../sys/bin

iw

libnl

curl -O http://www.infradead.org/~tgr/libnl/files/libnl-3.2.25.tar.gz
tar xvf libnl-3.2.25.tar.gz
cd libnl-3.2.25
CC=musl-gcc ./configure --disable-pthreads --disable-debug --disable-shared --disable-cli 
make -j8
cp lib/.libs/*.a ../sys-dev/lib/
cp -a include/netlink ../sys-dev/include/

iw

curl -O https://www.kernel.org/pub/software/network/iw/iw-4.0.tar.xz
tar xvf iw-4.0.tar.xz
cd iw-4.0
CC=musl-gcc CFLAGS=-I../sys-dev/include LDFLAGS='-static -L../sys-dev/lib' make -j4
strip iw
cp iw ../sys/bin

wpa_supplicant

curl -O http://w1.fi/releases/wpa_supplicant-2.4.tar.gz
tar xvf wpa_supplicant-2.4.tar.gz
cd wpa_supplicant-2.4/wpa_supplicant
cp ../../wpa_supplicant.config .config
make -j8
strip wpa_supplicant wpa_cli wpa_passphrase
cp wpa_supplicant wpa_cli wpa_passphrase ../../sys/bin

cgpt

git clone https://chromium.googlesource.com/chromiumos/platform/vboot_reference
cd vboot_reference
# TODO: patch
CC=musl-gcc CFLAGS=-I../sys-dev/include LDFLAGS='-L../sys-dev/lib -static' make cgpt
strip build/cgpt/cgpt
cp build/cgpt/cgpt ../sys/bin

e2fs

curl -O https://www.kernel.org/pub/linux/kernel/people/tytso/e2fsprogs/v1.42.12/e2fsprogs-1.42.12.tar.xz
tar xvf e2fsprogs-1.42.12.tar.xz
cd e2fsprogs-1.42.12
CC=musl-gcc CFLAGS="-I$PWD/../sys-dev/include -Os" LDFLAGS="-static -L$PWD/../sys-dev/lib" ./configure --disable-uuidd --disable-libblkid --disable-libuuid
make -j4
strip ./misc/mke2fs ./misc/tune2fs ./e2fsck/e2fsck
cp ./misc/mke2fs ./misc/tune2fs ./e2fsck/e2fsck ../sys/bin

curl

curl -O http://curl.haxx.se/download/curl-7.41.0.tar.lzma
tar xvf curl-7.41.0.tar.lzma
cd curl-7.41.0
CC=musl-gcc CFLAGS="-I$PWD/../sys-dev/include -Os -Wl,-static" LDFLAGS="-L$PWD/../sys-dev/lib" ./configure --with-zlib --disable-verbose --disable-libcurl-option --disable-rtsp --disable-shared --disable-file --disable-ldap --disable-dict --disable-telnet --disable-tftp --disable-pop3 --disable-imap --disable-smtp --disable-gopher
make -j4
strip src/curl
cp src/curl ../sys/bin

dropbear

curl -O https://matt.ucc.asn.au/dropbear/dropbear-2015.67.tar.bz2
tar xvf dropbear-2015.67.tar.bz2
cd dropbear-2015.67
CC=musl-gcc CFLAGS="-I$PWD/../sys-dev/include -Os" LDFLAGS="-static -L$PWD/../sys-dev/lib" ./configure --disable-lastlog --disable-wtmp --disable-syslog --disable-shadow
make PROGRAMS="dropbear dbclient scp" MULTI=1 STATIC=1 -j8
make PROGRAMS=dropbearkey STATIC=1
make PROGRAMS=dropbearconvert STATIC=1
strip dropbearmulti dropbearkey dropbearconvert
cp dropbearmulti ../sys/bin
ln -s dropbearmulti ../sys/bin/dropbear
ln -s dropbearmulti ../sys/bin/ssh
ln -s dropbearmulti ../sys/bin/scp
./dropbearkey -t ecdsa -f ../sys/etc/ecdsa_host_key
cat ~/.ssh/testing_rsa.pub > ../sys/etc/authorized_keys

flashrom

libkmod

curl -O http://ftp.kernel.org/pub/linux/utils/kernel/kmod/kmod-20.tar.xz
tar xvf kmod-20.tar.xz
cd kmod-20
# Remove check for enable static
CC=musl-gcc CFLAGS="-I$PWD/../sys-dev/include -Os" LDFLAGS="-L$PWD/../sys-dev/lib" ./configure  --enable-static --disable-manpages --disable-tools --disable-logging
make -j8
cp libkmod/libkmod.h ../sys-dev/include
cp libkmod/.libs/libkmod.a ../sys-dev/lib

pciutils

curl -O http://ftp.kernel.org/pub/software/utils/pciutils/pciutils-3.3.1.tar.xz
tar xvf pciutils-3.3.1.tar.xz
cd pciutils-3.3.1
CC=musl-gcc LDFLAGS="-L$PWD/../sys-dev/lib" make OPT="-Os -I$PWD/../sys-dev/include" DNS=no HWDB=no
cp lib/libpci.a ../sys-dev/lib
mkdir -p ../sys-dev/include/pci
cp lib/{config.h,header.h,pci.h,types.h} ../sys-dev/include/pci

dtc

curl -O https://www.kernel.org/pub/software/utils/dtc/dtc-1.4.1.tar.xz
tar xvf dtc-1.4.1.tar.xz
cd  dtc-1.4.1
CC=musl-gcc make -j8
cp libfdt/{fdt.h,libfdt.h,libfdt_env.h} ../sys-dev/include
cp libfdt/libfdt.a ../sys-dev/lib

flashrom

git clone https://chromium.googlesource.com/chromiumos/third_party/flashrom
cd flashrom
CC=musl-gcc CFLAGS="-Dloff_t=off_t -Os" CPPFLAGS=-I$PWD/../sys-dev/include LDFLAGS=-L$PWD/../sys-dev/lib make NOWARNERROR=yes CONFIG_STATIC=yes CONFIG_FT2232_SPI=no
strip flashrom
cp flashrom ../sys/bin

dmidecode

curl -LO http://download.savannah.gnu.org/releases/dmidecode/dmidecode-2.12.tar.bz2
tar xvf dmidecode-2.12.tar.bz2
cd dmidecode-2.12
make -j8 LDFLAGS=-static CC=musl-gcc
strip dmidecode
cp dmidecode ../sys/bin

auto

cd auto
CC=musl-gcc LDFLAGS="-s -static" make
cp auto ../sys/sbin

create filesystem

mksquashfs  sys sys.sqsh -comp lz4 -all-root -noappend
scp -i ~/.ssh/testing_rsa sys.sqsh [email protected]:/root
# dd if=sys.sqsh of=/dev/mmcblk0p3

Partitions

partitions 6 and 7 after partitions 8 partition 3 is data

Initial state

cgpt show /dev/mmcblk0 -q | sort

      64       16384      11  ChromeOS firmware
   16448           1       6  ChromeOS kernel
   16449           1       7  ChromeOS rootfs
   16450           1       9  ChromeOS reserved
   16451           1      10  ChromeOS reserved
   
   # 4028 gap
   
   20480       32768       2  ChromeOS kernel
   53248       32768       4  ChromeOS kernel
   86016       32768       8  Linux data
   
   # 131072 gap at 118784
   
  249856       32768      12  EFI System Partition
  282624     4194304       5  ChromeOS rootfs
 4476928     4194304       3  ChromeOS rootfs
 8671232    22073344       1  Linux data

Partitioning

 cgpt add -i 6 -b 118784 -s 32768 /dev/mmcblk0
 cgpt add -i 7 -b 151552 -s 32768 /dev/mmcblk0
 cgpt add -i 3 -t data -l root    /dev/mmcblk0
 # reboot

Remove unused partitions

cgpt add -i 9 -t unused /dev/mmcblk0
cgpt add -i 10 -t unused /dev/mmcblk0
cgpt add -i 11 -t unused /dev/mmcblk0
cgpt add -i 12 -t unused /dev/mmcblk0

Final state

  cgpt show /dev/mmcblk0 -q | sort

      64       16384      11  ChromeOS firmware
   16450           1       9  ChromeOS reserved
   16451           1      10  ChromeOS reserved
   20480       32768       2  ChromeOS kernel
   53248       32768       4  ChromeOS kernel
   86016       32768       8  Linux data
  118784       32768       6  ChromeOS kernel
  151552       32768       7  ChromeOS rootfs
  249856       32768      12  EFI System Partition
  282624     4194304       5  ChromeOS rootfs
 4476928     4194304       3  ChromeOS rootfs
 8671232    22073344       1  Linux data

Install archlinux

mkfs.btrfs -f /dev/mmcblk0p11
mount /dev/mmcblk0p11 /mnt
cd /mnt
btrfs subvolume create root
btrfs subvolume create home

curl -O http://archlinux.mirrors.ovh.net/archlinux/iso/2015.04.01/archlinux-bootstrap-2015.04.01-x86_64.tar.gz
tar xf archlinux-bootstrap-2015.04.01-x86_64.tar.gz
rm archlinux-bootstrap-2015.04.01-x86_64.tar.gz

# Select a mirror
vi root.x86_64/etc/pacman.d/mirrorlist

# chroot
cp /etc/resolv.conf    root.x86_64/etc/
mount -t proc none     root.x86_64/proc/
mount --rbind /sys     root.x86_64/sys/
mount --rbind /dev     root.x86_64/dev/
chroot root.x86_64

# This can be very long (not enough entropy ?)
pacman-key --init
pacman-key --populate archlinux
mount -o compress=lzo,subvol=root /dev/mmcblk0p11 /mnt
mkdir /mnt/home
mount -o compress=lzo,subvol=home /dev/mmcblk0p11 /mnt/home

Follow https://wiki.archlinux.org/index.php/Installation_guide#Install_the_base_packages

# patch pacstrap may be needed
pacstrap /mnt base
genfstab -p /mnt >> /mnt/etc/fstab
arch-chroot /mnt
echo chromeos > /etc/hostname
ln -sf /usr/share/zoneinfo/Europe/Paris /etc/localtime
locale-gen
echo KEYMAP=fr-latin1 > /etc/vconsole.conf
ln -s /proc/self/fd /dev
mkinitcpio -p linux
passwd

restart the system

Boot into archlinux

kexec -l /mnt/boot/vmlinuz-linux --initrd=/mnt/boot/initramfs-linux.img --command-line="root=/dev/mmcblk0p3 rootflags=subvol=root"
kexec -e

Misc

Remove boot warning screen

Remove the write protect screw

write protect screw

Write protect

/usr/share/vboot/bin/set_gbb_flags.sh 0x1

URL

Chromeos dev ssh keys

Let us ssh into the chromebook in dev mode.

https://chromium.googlesource.com/chromiumos/chromite/+/master/ssh_keys

ssh -i ~/.ssh/testing_rsa root@chromebook_ip

dump the partitions

dd if=/dev/mmcblk0pX of=mmcblk0pX

build vboot_reference (futility)

CFLAGS : remove -Werror make utils futil cgpt

Repack an existing partition

futility vbutil_kernel --repack kern.bin --keyblock key.keyblock --signprivate key.vbprivk --config cmdline --oldblob mmcblk0pX

Connect to the wifi

wpa_passphrase MYSSID passphrase > /tmp/wpa.conf
udhcpc

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