ShofEL2

A misleadingly-named Tegra X1 Boot ROM exploit and Nintendo Switch Linux loader.

See the accompanying blog post: https://fail0verflow.com/blog/2018/shofel2/

Obligatory disclaimer

If your Switch catches fire or turns into an Ouya, it's not our fault. It's stupidly easy to blow up embedded platforms like this with bad software (e.g. all voltages are software-controlled). We already caused temporary damage to one LCD panel with bad power sequencing code. Seriously, do not complain if something goes wrong.

On the other hand, this exploit probably works on the Ouya...

Usage

You need arm-linux-gnueabi and aarch64-linux-gnu toolchains. Linaro have working toolchains.

Clone everything:

$ git clone https://github.com/fail0verflow/shofel2.git
$ git clone --recursive https://github.com/fail0verflow/switch-coreboot.git coreboot
$ git clone https://github.com/fail0verflow/switch-u-boot.git u-boot
$ git clone https://github.com/fail0verflow/switch-linux.git linux
$ git clone https://github.com/boundarydevices/imx_usb_loader.git

Build the cbfs loader:

$ cd shofel2/exploit
$ make

Build u-boot:

$ cd u-boot
$ export CROSS_COMPILE=aarch64-linux-gnu-
$ make nintendo-switch_defconfig
$ make

Build coreboot:

$ cd coreboot
$ make nintendo_switch_defconfig
$ make iasl
$ make

Build imx_usb_loader:

$ cd imx_usb_loader
$ make

Build Linux:

$ cd linux
$ export ARCH=arm64
$ export CROSS_COMPILE=aarch64-linux-gnu-
$ make nintendo-switch_defconfig
$ make

If you get an error that looks like:

make[1]: *** No rule to make target '/lib/firmware/brcm/brcmfmac4356-pcie.txt', needed by 'firmware/brcm/brcmfmac4356-pcie.txt.gen.o'.  Stop.

download this, base64 decode it and put it on your host filesystem as /lib/firmware/brcm/brcmfmac4356-pcie.txt:

$ base64 -d brcmfmac4356-pcie.txt > brcmfmac4356-pcie-decoded.txt
$ cp brcmfmac4356-pcie-decoded.txt /lib/firmware/brcm/brcmfmac4356-pcie.txt # This command needs root.

Run the exploit

$ cd shofel2/exploit
$ ./shofel2.py cbfs.bin ../../coreboot/build/coreboot.rom # This command needs root or permissions to access usb devices.

Build the u-boot script and run it

$ cd shofel2/usb_loader
$ ../../u-boot/tools/mkimage -A arm64 -T script -C none -n "boot.scr" -d switch.scr switch.scr.img
$ ../../imx_usb_loader/imx_usb -c . # This command needs root or permissions to access usb devices.

Root filesystems

If all went well, you should have some penguins. You should probably put a root filesystem on your SD card. Userspace libraries and other patches coming soon.

Here is an example on how to get Arch up and running.

• make a new MBR partition table on a fresh sdcard
• make two partitions on it
• format the second one as ext4
• mount that partition somewhere
• download Arch Linux ARM rootfs
• untar it into your partition as root.

Here are some example commands you should not just copy paste into your terminal.

$ mkdir -p /tmp/sdcard
$ mount -t ext4 /dev/mmcblk0p2 /tmp/sdcard
$ wget http://os.archlinuxarm.org/os/ArchLinuxARM-aarch64-latest.tar.gz
$ sudo tar -xf ArchLinuxARM-aarch64-latest.tar.gz -C /tmp/sdcard
$ sudo umount /dev/mmcblk0p2

You will most likely need a 1.8V serial cable connected to the right hand side Joy-Con port to do anything useful with this at this point. Please do not bug us with questions about how to get this to run if you do not have a means to debug things yourself. This is not ready for end users. If you really want to try configuring your Linux image standalone to boot with WiFi or X support to get something done without a serial console, you're on your own and you get to suffer through the pain all by yourself. Hint: WiFi is broken on the first boot, you need to reboot on the first Linux launch (which puts you back into RCM mode), and then run the exploit again. Patches welcome.