#!/bin/bash
# 2022-10-15

KERNEL_DEFAULT=6.0

OUTFOLDER=$1
KERNEL_MAIN=$2
KERNEL_PATCH=$3
KERNEL_RT=$4
PATCH_FILE=
KERNEL=
FINAL_FOLDER=$OUTFOLDER
BASE_FOLDER=$FINAL_FOLDER

SKIP_PACMAN=1
SKIP_TOOLCHAIN_CREATION=1
SKIP_ADD_FOLDER=0
SKIP_GRAB_KERNEL=0
SKIP_KERNEL_RT=1
SKIP_BUILD_KERNEL=0
SKIP_BUILD_FINAL=0

#
# https://www.raspberrypi.com/documentation/computers/linux_kernel.html#cross-compiling-the-kernel
# https://wiki.archlinux.org/title/Cross-compiling_tools_package_guidelines
# https://ilyas-hamadouche.medium.com/creating-a-cross-platform-toolchain-for-raspberry-pi-4-5c626d908b9d
#

function header() {
	clear
	echo ">>> Toolchain Archlinux / RPi 4 ARM64 / Kernel"
	echo "--------------------------------------------------"
	echo ">> DATE     : $CURRENT"
	echo ">> OUTFOLDER: $OUTFOLDER"
	echo ">> BRANCH   : $BRANCH"
	echo ">> PATCH    : $PATCH_FILE"
	echo ">> RT PATCH : $KERNEL_RT"
	echo ">> VERSION  : $VERSION"
	echo ">> KERNEL   : $KERNEL"
	echo "--------------------------------------------------"
	echo ""
}

function wait() {
	read -p "> [Press enter to continue] "
}

header
echo "> Prepare things"
# if kernel branch is not given, use default
if [ -z "$KERNEL_MAIN" ]; then
	KERNEL_MAIN=$KERNEL_DEFAULT
fi
# if patch is given but file doesn't exist, remove it
if [ ! -z "$KERNEL_PATCH" ]; then
	if [ ! -f "$KERNEL_PATCH" ]; then
		KERNEL_PATCH=
	else
		PATCH_FILE=$(basename $KERNEL_PATCH)
	fi
fi

# kernel branch/version
MAIN=$KERNEL_MAIN
BRANCH=rpi-$MAIN.y

# use current date as base kernel folder
CURRENT=$(date '+%Y-%m-%d')

# folders
OUTFOLDER=$BASE_FOLDER/$CURRENT

header
echo "> Create working folders"
if [ ! -d "~/src" ]; then
	mkdir -p ~/src
fi
if [ ! -d "$OUTFOLDER" ]; then
	mkdir -p $OUTFOLDER
fi
cd $OUTFOLDER
if [ ! -d "ctng" ]; then
	mkdir ctng
fi
cd $OUTFOLDER

if [ ! -z "$PATCH_FILE" ]; then
	cp $KERNEL_PATCH $OUTFOLDER/$PATCH_FILE
fi

if [ "$SKIP_PACMAN" == "0" ]; then
	header
	echo "> Install crosstool-ng"
	wait
	sudo pacman -S --needed crosstool-ng
fi

if [ "$SKIP_TOOLCHAIN_CREATION" == "0" ]; then
	header
	echo "> Create toolchain for RPi 4"
	echo ">> Set 'Render the toolchain read-only' to false (uncheck)"
	wait
	ulimit -n 4096 now
	#
	#  Make 1 changes:
	#  1. Allow extending the toolchain after it is created (by default, it is created as read-only):
	#      Paths and misc options -> Render the toolchain read-only ->false
	#
	cd ctng
	ct-ng -j$(nproc) aarch64-rpi4-linux-gnu
	ct-ng -j$(nproc) menuconfig

	header
	# (path: ${HOME}/x-tools/aarch64-rpi4-linux-gnu)
	echo "> Build the toolchain"
	ct-ng -j$(nproc) build
fi

header
echo "> Add toolchain path"
cd $OUTFOLDER
PATH=$PATH:~/x-tools/aarch64-rpi4-linux-gnu/bin

if [ "$SKIP_ADD_FOLDER" == "0" ]; then
	header
	echo "> Add folders"
	wait
	sudo rm -rf build
	mkdir -p build/mnt/fat32/overlays
	mkdir -p build/mnt/ext4/opt/build/kernel/$CURRENT/$BRANCH
fi

if [ ! -z "$PATCH_FILE" ]; then
	cp $OUTFOLDER/$PATCH_FILE build/mnt/$PATCH_FILE
fi

if [ "$SKIP_GRAB_KERNEL" == "0" ]; then
	header
	echo "> Get kernel sources"
	rm -rf linux
	rm -rf $BRANCH
	git clone --branch $BRANCH --depth=1 https://github.com/raspberrypi/linux
	mv linux $BRANCH
fi
cd $BRANCH

header
echo "> Get exact kernel version"
FILE=Makefile
KVERSION=VERSION
KPATCHLEVEL=PATCHLEVEL
KSUBLEVEL=SUBLEVEL
KEXTRAVERSION=EXTRAVERSION
	GET_VAR=$KVERSION && KVERSION=$(grep --color=never -Po "^${GET_VAR}\ =\ \K.*" "${FILE}" || true)
	GET_VAR=$KPATCHLEVEL && KPATCHLEVEL=$(grep --color=never -Po "^${GET_VAR}\ =\ \K.*" "${FILE}" || true)
	GET_VAR=$KSUBLEVEL && KSUBLEVEL=$(grep --color=never -Po "^${GET_VAR}\ =\ \K.*" "${FILE}" || true)
	GET_VAR=$KEXTRAVERSION && KEXTRAVERSION=$(grep --color=never -Po "^${GET_VAR}\ =\ \K.*" "${FILE}" || true)
VERSION=$KVERSION.$KPATCHLEVEL.$KSUBLEVEL

if [ "$SKIP_BUILD_KERNEL" == "0" ]; then
	header

	if [ "$SKIP_KERNEL_RT" == "0" ]; then
		echo "> Apply RT patchs"
		wget https://mirrors.edge.kernel.org/pub/linux/kernel/projects/rt/$MAIN/patch-$MAIN-$KERNEL_RT.patch.gz
		if [ ! -f patch-$MAIN-$KERNEL_RT.patch.gz ]; then
			echo ">> No Kernel RT patch found... Not appying !"
			wait
		else
			gzip -cd patch-$MAIN-$KERNEL_RT.patch.gz | patch -p1 --verbose
		fi
	fi

	header
	echo "> Generate default config"
	KERNEL=kernel8
	env PATH=$PATH make -j$(nproc) ARCH=arm64 CROSS_COMPILE=aarch64-rpi4-linux-gnu- bcm2711_defconfig

    header
	echo "> Disable Debug Infos"
	env PATH=$PATH scripts/config --disable DEBUG_INFO

	header
	echo "> Backup config"
	cp -f .config .config.original

	if [ ! -z "$PATCH_FILE" ]; then
		header
		echo "> Apply config patch"
		cp $OUTFOLDER/$PATCH_FILE $PATCH_FILE
		patch < $OUTFOLDER/$PATCH_FILE
	fi

	# setup kernel config and generate diff patch from original
	# or patch default config with defined patch
	header
	echo "> Generate config"
	echo ">> If you specified patch, you may save/exit only"
    echo ">> Feel free to adjust settings too..."
	wait
	env PATH=$PATH make -j$(nproc) ARCH=arm64 CROSS_COMPILE=aarch64-rpi4-linux-gnu- menuconfig
	if [ ! -f ".config" ]; then
		header
		echo "> !!! No .config (menuconfig) found!"
		echo "> !!! Abort!"
		exit 1
	fi

    header
    echo "> Create config patch from original for current version"
    diff -u .config.original .config > $OUTFOLDER/kernel_config_patch_$VERSION.patch

	header
	echo "> Disable Debug Info"
	wait
	env PATH=$PATH scripts/config --disable DEBUG_INFO

	header
	echo "> Compile kernel"
	wait
	env PATH=$PATH make -j$(nproc) ARCH=arm64 CROSS_COMPILE=aarch64-rpi4-linux-gnu- Image modules dtbs

	header
	echo "> Install modules"
	env PATH=$PATH make -j$(nproc) ARCH=arm64 CROSS_COMPILE=aarch64-rpi4-linux-gnu- INSTALL_MOD_PATH=../build/mnt/ext4 modules_install
else
	KERNEL=kernel8
fi
KERNEL=$KERNEL-$VERSION-v8+

header
echo "> Copy files"
wait
sudo cp arch/arm64/boot/Image ../build/mnt/fat32/$KERNEL.img
sudo cp arch/arm64/boot/dts/broadcom/*.dtb ../build/mnt/fat32/
sudo cp arch/arm64/boot/dts/overlays/*.dtb* ../build/mnt/fat32/overlays/
sudo cp arch/arm64/boot/dts/overlays/README ../build/mnt/fat32/overlays/

header
echo "> Adjust permissions"
wait
cd $OUTFOLDER
sudo chmod -R 0755 build/mnt/fat32/

header
echo "> Copy kernel source"
cd $OUTFOLDER
sudo mkdir -p build/mnt/ext4/opt/build/kernel/$CURRENT/$BRANCH
sudo cp -r $BRANCH build/mnt/ext4/opt/build/kernel/$CURRENT/

header
echo "> Remove symlinks..."
wait
cd $OUTFOLDER
cd build/mnt/ext4/lib/modules/$VERSION-v8+/
sudo rm build
sudo rm source


header
echo "> Create post-install script..."
cd $OUTFOLDER
sudo chown -R 1000:1000 build
cd build/mnt/
rm -f install.sh
touch install.sh
tee -a install.sh <<EOF
#!/bin/bash
clear

echo ">>> Installation of kernel [$KERNEL]"

echo "> Setup permissions (fat32)"
chmod -R 0755 fat32/

echo "> Setup owner (root)"
chown -R root:root fat32/
chown -R root:root ext4/

echo "> Copy files (fat32, ext4)"
cp -rf fat32/.      /boot/
cp -rf ext4/lib/.   /lib/
cp -rf ext4/opt/.   /opt/

echo "> Symlink kernel source to modules ($VERSION-v8+)"
rm -f /lib/modules/$VERSION-v8+/build
rm -f /lib/modules/$VERSION-v8+/source
ln -s /opt/build/kernel/$CURRENT/$BRANCH /lib/modules/$VERSION-v8+/build
ln -s /opt/build/kernel/$CURRENT/$BRANCH /lib/modules/$VERSION-v8+/source

echo "> Add kernel line (as disabled) to config.txt"
echo '#kernel=$KERNEL.img' >> /boot/config.txt

echo "> Done!"
EOF
chmod +x install.sh

header
echo "> Adjust rights"
wait
cd $OUTFOLDER
sudo chown -R root:root build

if [ "$SKIP_BUILD_FINAL" == "0" ]; then
	header
	echo "> Build archive"
	cd $OUTFOLDER/build/mnt/
	sudo tar -cf $OUTFOLDER/rpi_kernel_arm64_$VERSION.tar .
    sudo chown 1000:1000 $OUTFOLDER/rpi_kernel_arm64_$VERSION.tar

	header
	echo "> Compress archive"
	cd $OUTFOLDER
	sudo pigz --force --best rpi_kernel_arm64_$VERSION.tar
	sudo chown 1000:1000 rpi_kernel_arm64_$VERSION.tar.gz
fi

header
echo "> Create install script"
rm -f install.sh
touch install.sh
tee -a install.sh <<EOF
#!/bin/bash
clear

echo ">>> Extraction of kernel [$KERNEL]"

echo "> Unzip archive"
pigz -d rpi_kernel_arm64_$VERSION.tar.gz
chown root:root rpi_kernel_arm64_$VERSION.tar

echo "> Untar archive"
tar -xf rpi_kernel_arm64_$VERSION.tar

echo "> Set install script as root/executable"
chown root:root install.sh
chmod +x install.sh

echo "> Proceed to install kernel with: [bash install.sh]"
echo "> Done!"
EOF
chmod +x install.sh

header
echo "> Done!"

exit 0