Add script for crossystem/mosys building, update readme with docs for both

README.md

@@ -190,6 +190,45 @@ You can use the environment variable `PRAWNOS_SUITE` to use a Debian suite other
 You can use the environment variable `PRAWNOS_DEBOOTSTRAP_MIRROR` to use a non-default Debian mirror with debootstrap.  For example, to use [Debian's Tor onion service mirror](https://onion.debian.org/) with debootstrap, you can build with `sudo PRAWNOS_DEBOOTSTRAP_MIRROR=http://vwakviie2ienjx6t.onion/debian make image`.
 
 
+## Crossystem / mosys
+You can run the `buildCrossystem.sh` script located in `/InstallScripts/` to build `mosys` and install `crossystem`
+```
+sudo /InstallScripts/buildCrossystem.sh
+```
+
+### Warning: running these commands can leave you in a state where you cannot boot.
+Specifically, enabling `dev_boot_signed_only` will prevent PrawnOS from booting, as no key is stored in the bootloader for the PrawnOS Linux kernel
+Its also a bad idea to disable `dev_boot_usb` unless you are positive you will always be able to boot to the internal emmc.
+Unless you are running libreboot, the only way to recover if you get in one of these states is to reinstall chromeos using recovery media 
+
+#### Example crossystem  and mosys commands, most require root privileges
+
+Kernels signature verification:
+
+`sudo crossystem dev_boot_signed_only=1` enable
+`sudo crossystem dev_boot_signed_only=0` disable
+
+External media boot:
+
+`sudo crossystem dev_boot_usb=1` enable
+`sudo crossystem dev_boot_usb=0` disable
+
+Legacy payload boot:
+
+`sudo crossystem dev_boot_legacy=1` enable 
+`sudo crossystem dev_boot_legacy=0` disable
+
+Default boot medium:
+`sudo crossystem dev_default_boot=disk` internal storage
+`sudo crossystem dev_default_boot=usb` external media
+`sudo crossystem dev_default_boot=legacy` legacy payload
+
+Dump system state:
+`sudo crossystem`
+
+View mosys command tree:
+`sudo mosys -t`
+
 ### GPU Support
 
 Watch this link for GPU support:

scripts/InstallScripts/buildCrossystem.sh

@@ -0,0 +1,69 @@
+#!/bin/sh -xe
+
+#Build mosys, which is required for crossystem
+
+
+# This file is part of PrawnOS (http://www.prawnos.com)
+# Copyright (c) 2018 Hal Emmerich <hal@halemmerich.com>
+
+# PrawnOS is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 2
+# as published by the Free Software Foundation.
+
+# PrawnOS is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with PrawnOS.  If not, see <https://www.gnu.org/licenses/>.
+
+
+# install crossystem
+sudo apt install -y vboot-utils
+
+#install clang and pre-reqs
+sudo apt install -y clang uuid-dev meson pkg-config cmake libcmocka-dev cargo
+
+#clone flashmap, need to build libfmap
+git clone https://github.com/dhendrix/flashmap.git
+cd flashmap
+make all
+sudo make install
+
+#clone mosys. Later releases start depending on the minijail library which we would have to build, and that we don't care about anyway on linux
+git clone https://chromium.googlesource.com/chromiumos/platform/mosys
+cd mosys
+git checkout release-R69-10895.B
+
+# compile the c parts
+CC=clang meson -Darch=arm build
+ninja -C build
+# compile the rust parts
+MESON_BUILD_ROOT=build cargo build
+
+# install mosys so crossystem can access it. It EXPECTS it to be right here and fails otherwise...
+sudo cp build/mosys /usr/sbin/mosys
+
+
+# Example crossystem commands, all require root priviledges
+#Kernels signature verification:
+
+# crossystem dev_boot_signed_only=1 # enable
+# crossystem dev_boot_signed_only=0 # disable
+
+#External media boot:
+
+# crossystem dev_boot_usb=1 # enable
+# crossystem dev_boot_usb=0 # disable
+
+#Legacy payload boot:
+
+# crossystem dev_boot_legacy=1 # enable
+# crossystem dev_boot_legacy=0 # disable
+
+#Default boot medium:
+
+# crossystem dev_default_boot=disk # internal storage
+# crossystem dev_default_boot=usb # external media
+# crossystem dev_default_boot=legacy # legacy payload