Spin‑off from Chromebook  papge to document running mainline u‑boot and Linux on Exynos

Contents: [Dobrica Pavlinušić's random unstructured stuff]
• Dobrica Pavlinušić's random unstructured stuff (u‑boot) 
• Dobrica Pavlinušić's random unstructured stuff (SPI eeprom image) 
• Dobrica Pavlinušić's random unstructured stuff (chromiumos build) 
• Dobrica Pavlinušić's random unstructured stuff (pxelinux config) 
• Dobrica Pavlinušić's random unstructured stuff (kernel) 
• Dobrica Pavlinušić's random unstructured stuff (chromiumos kernel) 
• Dobrica Pavlinušić's random unstructured stuff (security) 

u‑boot
SPI eeprom image
dpavlin@klin:/klin/u-boot$ cat build-spi.sh 
#!/bin/sh -xe

make
#cp /klin/books/Chromebook/spi/snow-bricked.rom .
cp snow-bricked.rom snow-mix.rom
dd conv=notrunc if=spl/smdk5250-spl.bin of=snow-mix.rom seek=$((0x00002000)) bs=1
dd conv=notrunc if=u-boot.bin of=snow-mix.rom seek=$((0x00006000)) bs=1
scp snow-mix.rom rpi2:chromebook/

Upstream u‑boot works, but can't find mmc devices, so internal flash is not accessable, so I had to boot from USB network using u‑boot pxe
chromiumos build
dpavlin@klin:/klin/chromebook$ . env.sh 
dpavlin@klin:/klin/chromebook/chromiumos$ cros_sdk

• apply some patches (or not) as described at
(cr) (altAddr) dpavlin@klin ~/trunk/src/third_party/u-boot/files $ emerge-${BOARD} chromeos-u-boot

pxelinux config
dpavlin@x230:/var/tftp/pxelinux.cfg$ cat default-arm-exynos 
TIMEOUT 10

MENU TITLE TFTP boot

LABEL snow
        MENU LABEL sdcard?
        LINUX ../zImage
        FDTDIR ../
        APPEND console=tty1 console=ttyS0,115200n8 loglevel=8 rootwait rw earlyprintk root=/dev/sdcard0

kernel
doesn't boot ATM
dpavlin@klin:/klin/imx6/linux-imx$ cat build-chromebook.sh 
# 

cd /klin/chromebook/chromiumos/src/third_party/kernel/v4.4

export CROSS_COMPILE="arm-linux-gnueabihf-" ARCH=arm

test ! -f .config && make exynos_defconfig
make -j4 zImage exynos5250-snow.dtb
cp -v arch/arm/boot/zImage arch/arm/boot/dts/exynos5250-snow.dtb /media/boot/

chromiumos kernel
https://github.com/dnschneid/crouton/wiki/Build‑chrome‑os‑kernel‑and‑kernel‑modules 
security
(might not be related, but useful to keep track of)
• https://fredericb.info/2020/06/exynos8890‑bootrom‑dump‑dump‑exynos‑8890‑bootrom‑from‑samsung‑galaxy‑s7.html 
• https://fredericb.info/2020/06/reverse‑engineer‑usb‑stack‑of‑exynos‑bootrom.html 
• https://github.com/frederic/exynos8890‑bootrom‑dump