From 7c7589c36d18382bf5f77791a9b37dfb9bc5b616 Mon Sep 17 00:00:00 2001
From: Gardouille <gardouille@gmail.com>
Date: Fri, 18 Aug 2023 15:10:50 +0200
Subject: [PATCH] Create unified kernel for arch linux

---
 archlinux/create-efi-kernel.sh | 418 +++++++++++++++++++++++++++++++++
 1 file changed, 418 insertions(+)
 create mode 100755 archlinux/create-efi-kernel.sh

diff --git a/archlinux/create-efi-kernel.sh b/archlinux/create-efi-kernel.sh
new file mode 100755
index 0000000..138a62b
--- /dev/null
+++ b/archlinux/create-efi-kernel.sh
@@ -0,0 +1,418 @@
+#!/bin/sh
+#
+# Purpose {{{
+# This script will create an Unified Kernel + UEFI entry for ArchLinux
+#   1. Verify dependancies (efibootmgr, objcopy…).
+#   2. Clean older unified kernels.
+#   3. Backup last unified kernel.
+#   4. Create a new unified kernel from vmlinuz, initramfs, UUID of root,…
+#   5. Ensure an UEFI entry exists for this unified kernel.
+#
+# 2023-08-17
+# }}}
+# TODO {{{
+# 1. Encrypted LVM is not yet supported. See crypt_part_uuid relative comments.
+# }}}
+# Flags {{{
+## Exit on error {{{
+set -o errexit
+## }}}
+## Exit on unset var {{{
+### Use "${VARNAME-}" to test a var that may not have been set
+set -o nounset
+## }}}
+## Pipeline command is treated as failed {{{
+### Not available in POSIX sh − https://github.com/koalaman/shellcheck/wiki/SC3040
+#set -o pipefail
+## }}}
+## Help with debugging {{{
+### Call the script by prefixing it with "TRACE=1 ./script.sh"
+if [ "${TRACE-0}" -eq 1 ]; then set -o xtrace; fi
+## }}}
+# }}}
+# Vars {{{
+PROGNAME=$(basename "${0}"); readonly PROGNAME
+PROGDIR=$(readlink --canonicalize-missing $(dirname "${0}")); readonly PROGDIR
+ARGS="${*}"; readonly ARGS
+readonly NBARGS="${#}"
+[ -z "${DEBUG-}" ] && DEBUG=1
+## Export DEBUG for sub-script
+export DEBUG
+
+## Default values for Unified kernel
+readonly ROOT_UUID_DEFAULT=$(findmnt --kernel --noheadings --output UUID -- /)
+readonly ROOT_FSTYPE_DEFAULT=$(findmnt --kernel --noheadings --output FSTYPE -- /)
+readonly CRYPT_PART_UUID_DEFAULT=$(blkid | sed --silent 's;/dev/.*_crypt.*UUID="\(.*\)".*TYPE=.*;\1;p')
+readonly UEFI_BOOT_STUB_FILE_DEFAULT="/usr/lib/systemd/boot/efi/linuxx64.efi.stub"
+
+## Default values for UEFI entry
+readonly EFI_BASE_LABEL_DEFAULT="Arch Linux unified"
+readonly EFI_MOUNT_PATH_DEFAULT="/boot/efi"
+
+## Temp files
+readonly temp_kernel_command_file="/tmp/kernel.command.temp"
+
+## Colors
+readonly PURPLE='\033[1;35m'
+readonly RED='\033[0;31m'
+readonly RESET='\033[0m'
+readonly COLOR_DEBUG="${PURPLE}"
+# }}}
+usage() {                                                       # {{{
+
+	cat <<- HELP
+usage: $PROGNAME [-d|-h|-b|-f|-k|-u|-l|-m]
+
+Script to build unified kernel for Arch Linux will all required informations
+(vmlinuz, initramfs, UUID of root's partition,…) and create an UEFI entry.
+
+EXAMPLES :
+    - Build unified kernel with default :
+        ${PROGNAME}
+
+    - Build unified kernel with current command line :
+        ${PROGNAME} --kernel "\$(< /proc/cmdline)"
+
+OPTIONS :
+    -d,--debug
+        Enable debug messages.
+
+    -h,--help
+        Print this help message.
+
+Unified kernel OPTIONS :
+
+    -b,--boot-stub,--uefi-boot
+        Define UEFI boot stub file to use.
+        (default: ${UEFI_BOOT_STUB_FILE_DEFAULT})
+        For more infos, see: https://man.archlinux.org/man/linuxx64.efi.stub.7.en
+
+    -f,--fs,--root-fs
+        Define a different root partition's filesystem.
+        (default: ${ROOT_FSTYPE_DEFAULT})
+        Thanks to command : findmnt --kernel --noheadings --output FSTYPE -- /
+
+    -u,--uuid,--root-uuid
+        Define a different root partition's UUID.
+        (default: ${ROOT_UUID_DEFAULT})
+        Thanks to command : findmnt --kernel --noheadings --output UUID -- /
+
+    -k,--kernel,--kernel-cmd
+        Define the kernel command line to use.
+        (default: build with root-fs|root-uuid and add_efi_memmap + ro options)
+
+UEFI entry OPTIONS :
+
+    -l,--label
+        Set a new label for UEFI entry.
+        (default: ${EFI_BASE_LABEL_DEFAULT})
+
+    -m,--mount-path,--esp
+        Define a different mountpoint for the EFI partition.
+        (default: ${EFI_MOUNT_PATH_DEFAULT})
+HELP
+}
+# }}}
+debug_message() {                                               # {{{
+
+	local_debug_message="${1}"
+
+	## Print message if DEBUG is enable (=0)
+	[ "${DEBUG}" -eq "0" ] && printf '\e[1;35m%-6b\e[m\n' "DEBUG − ${PROGNAME} : ${local_debug_message}"
+
+	unset local_debug_message
+
+	return 0
+}
+# }}}
+error_message() {                                               # {{{
+
+	local_error_message="${1}"
+	local_error_code="${2}"
+
+	## Print message
+	printf '%b\n' "ERROR − ${PROGNAME} : ${RED}${local_error_message}${RESET}" >&2
+
+	unset local_error_message
+
+	exit "${local_error_code:=66}"
+}
+# }}}
+define_vars() {                                                 # {{{
+
+	# If root_uuid wasn't defined (argument) {{{
+	if [ -z "${root_uuid-}" ]; then
+		## Use default value
+		readonly root_uuid="${ROOT_UUID_DEFAULT}"
+	fi
+	# }}}
+	# If root_fstype wasn't defined (argument) {{{
+	if [ -z "${root_fstype-}" ]; then
+		## Use default value
+		readonly root_fstype="${ROOT_FSTYPE_DEFAULT}"
+	fi
+	# }}}
+	# If kernel_command_line wasn't defined (argument) {{{
+	if [ -z "${kernel_command_line-}" ]; then
+		## Use default value
+		readonly kernel_command_line="root=UUID=${root_uuid} rootfstype=${root_fstype} add_efi_memmap ro"
+		## For encrypted LVM
+		#readonly kernel_command_line="root=UUID=${root_uuid} rootfstype=${root_fstype} add_efi_memmap ro cryptdevice=UUID=${crypt_part_uuid}:lvm"
+	fi
+	# }}}
+	# If uefi_boot_stub_file wasn't defined (argument) {{{
+	if [ -z "${uefi_boot_stub_file-}" ]; then
+		## Use default value
+		readonly uefi_boot_stub_file="${UEFI_BOOT_STUB_FILE_DEFAULT}"
+	fi
+	# }}}
+
+	# If efi_base_label wasn't defined (argument) {{{
+	if [ -z "${efi_base_label-}" ]; then
+		## Use default value
+		readonly efi_base_label="${EFI_BASE_LABEL_DEFAULT}"
+	fi
+	# }}}
+	# If efi_mount_path wasn't defined (argument) {{{
+	if [ -z "${efi_mount_path-}" ]; then
+		## Use default value
+		readonly efi_mount_path="${EFI_MOUNT_PATH_DEFAULT}"
+	fi
+	# }}}
+
+	# If esp_device wasn't defined (argument) {{{
+	if [ -z "${esp_device-}" ]; then
+		## Use default value
+		readonly esp_device=$(findmnt -kno SOURCE "${efi_mount_path}" | grep --invert-match -- systemd | sed s-/dev/--)
+	fi
+	# }}}
+	# If esp_disk wasn't defined (argument) {{{
+	if [ -z "${esp_disk-}" ]; then
+		## Use default value
+		readonly esp_disk=$(lsblk /dev/"${esp_device}" -no pkname)
+	fi
+	# }}}
+	# If esp_part wasn't defined (argument) {{{
+	if [ -z "${esp_part-}" ]; then
+		## Use default value
+		readonly esp_part=$(cat /sys/class/block/"${esp_device}"/partition)
+	fi
+	# }}}
+
+}
+# }}}
+
+is_command_available() {                                        # {{{
+
+	local_command_available_cmd="${1}"
+	debug_prefix="${2:-}"
+
+	## Return False by default
+	return_command_available="1"
+
+	if [ "$(command -v ${local_command_available_cmd})" ]; then
+		debug_message "${debug_prefix}is_command_available − \
+${RED}${local_command_available_cmd}${COLOR_DEBUG} seems present on this host."
+		return_command_available="0"
+	else
+		debug_message "${debug_prefix}is_command_available − \
+${RED}${local_command_available_cmd}${COLOR_DEBUG} is not available on this host."
+		return_command_available="1"
+	fi
+
+	unset local_command_available_cmd
+	unset debug_prefix
+
+	return "${return_command_available}"
+}
+# }}}
+
+main() {                                                        # {{{
+
+	debug_message "--- MAIN BEGIN"
+
+	## If a efibootmgr is missing {{{
+	### Exit with error message
+	is_command_available "efibootmgr" "| " \
+		|| error_message "No efibootmgr command available. Please install efibootmgr package with your package manager (pacman -S efibootmgr)." 01
+	## }}}
+	## If a objcopy is missing {{{
+	### Exit with error message
+	is_command_available "objcopy" "| " \
+		|| error_message "No objcopy command available. Please install binutils package with your package manager (pacman -S binutils)." 02
+	## }}}
+
+	## Define all vars
+	define_vars
+	debug_message "| Define vars"
+
+	## If UEFI boot stub is missing {{{
+	### Exit with error message
+	test -f "${uefi_boot_stub_file}" \
+		|| error_message "No UEFI boot stub file available (${uefi_boot_stub_file}). Please verify your systemd installation (systemd or systemd-boot-efi packages)." 03
+	## }}}
+	## Ensure EFI device is mounted {{{
+	if ! mountpoint --quiet "${efi_mount_path}"; then
+		mount "${efi_mount_path}" \
+			|| error_message "Can't mount EFI device" 04
+	fi
+	## }}}
+
+	## Put Kernel command line in temp file {{{
+	rm --force -- "${temp_kernel_command_file}" ; touch "${temp_kernel_command_file}"
+	printf "%s" "${kernel_command_line}" >> "${temp_kernel_command_file}"
+	## }}}
+
+	## Calculate address values to use for each section {{{
+	osrel_offs=$(objdump --section-headers -- "${uefi_boot_stub_file}" | awk 'NF==7 {size=strtonum("0x"$3); offset=strtonum("0x"$4)} END {print size + offset}')
+	cmdline_offs=$((osrel_offs + $(stat --dereference --format=%s -- "/usr/lib/os-release")))
+	linux_offs=$((cmdline_offs + $(stat --dereference --format=%s -- "${temp_kernel_command_file}")))
+	#linux_offs=$((cmdline_offs + $(stat --dereference --format=%s -- "/proc/cmdline")))
+	initrd_offs=$((linux_offs + $(stat --dereference --format=%s -- "/boot/vmlinuz-linux")))
+	## }}}
+
+	## Debug message {{{
+	debug_message "Try to build Unified kernel with from this informations :\r
+  * UEFI boot stub file: ${RED}${uefi_boot_stub_file}${COLOR_DEBUG}\r
+  * Root's UUID: ${RED}${root_uuid}${COLOR_DEBUG}\r
+  * Root's filesystem: ${RED}${root_fstype}${COLOR_DEBUG}\r
+  * Kernel command line: ${RED}${kernel_command_line}${COLOR_DEBUG}\r
+  * EFI device: ${RED}${esp_device}${COLOR_DEBUG}\r
+  * EFI disk: ${RED}${esp_disk}${COLOR_DEBUG}\r
+  * EFI partition number: ${RED}${esp_part}${COLOR_DEBUG}\r
+Addresses values :\r
+  * osrel : ${RED}${osrel_offs}${COLOR_DEBUG}\r
+  * cmdline : ${RED}${cmdline_offs}${COLOR_DEBUG}\r
+  * linux : ${RED}${linux_offs}${COLOR_DEBUG}\r
+  * initrd : ${RED}${initrd_offs}${COLOR_DEBUG}\r
+And generate UEFI entry :\r
+  * Label: ${RED}${efi_base_label}${COLOR_DEBUG}"
+
+	## }}}
+
+	## Ensure EFI mount path subdirectories exists
+	mkdir --parents -- "${efi_mount_path}/EFI/arch/"
+	## Create unified kernel blob {{{
+	objcopy \
+		--add-section .osrel="/usr/lib/os-release" --change-section-vma .osrel=$(printf 0x%x $osrel_offs) \
+		--add-section .cmdline="${temp_kernel_command_file}" --change-section-vma .cmdline=$(printf 0x%x $cmdline_offs) \
+		--add-section .linux="/boot/vmlinuz-linux" --change-section-vma .linux=$(printf 0x%x $linux_offs) \
+		--add-section .initrd="/boot/initramfs-linux.img" --change-section-vma .initrd=$(printf 0x%x $initrd_offs) \
+		"${uefi_boot_stub_file}" "${efi_mount_path}/EFI/arch/linux.arch.efi"
+	## }}}
+	## If no UEFI entry for this label + kernel {{{
+	## Create one
+	efibootmgr | grep --quiet -- "${efi_base_label}.*\\\EFI\\\arch\\\linux.arch.efi" \
+		|| efibootmgr --disk /dev/"${esp_disk}" --part "${esp_part}" --create --label "${efi_base_label}" --loader "\\EFI\\arch\\linux.arch.efi"
+	## }}}
+
+	## Remove temp files
+	rm --force -- "${temp_kernel_command_file}"
+
+	debug_message "--- MAIN END"
+}
+# }}}
+
+# Manage arguments                                                # {{{
+# This code can't be in a function due to argument management
+
+if [ ! "${NBARGS}" -eq "0" ]; then
+
+	manage_arg="0"
+
+	## If the first argument ask for help (h|help|-h|-help|-*h|-*help) {{{
+	if printf -- '%s' "${1-}" | grep --quiet --extended-regexp -- "^-*h(elp)?$"; then
+		usage
+		exit 0
+	fi
+	## }}}
+
+	## If the first argument is not an option
+	if ! printf -- '%s' "${1}" | grep --quiet --extended-regexp -- "^-+";
+	then
+		## Print help message and exit
+		printf '%b\n' "${RED}Invalid option: ${1}${RESET}"
+		printf '%b\n' "---"
+		usage
+
+		exit 1
+	fi
+
+	# Parse all options (start with a "-") one by one
+	while printf -- '%s' "${1-}" | grep --quiet --extended-regexp -- "^-+"; do
+
+	case "${1}" in
+		## OPTIONS
+		-d|--debug )                          ## debug
+			DEBUG=0
+			debug_message "--- Manage argument BEGIN"
+			;;
+		-h|--help )                           ## display help message
+			usage
+			exit 0
+			;;
+		## Unified kernel OPTIONS
+		-u|--boot-stub|--uefi-boot )          ## Define uefi_boot_stub_file with given arg
+			## Move to the next argument
+			shift
+			## Define var
+			readonly uefi_boot_stub_file="${1}"
+			;;
+		-k|--kernel|--kernel-cmd )            ## Define kernel_command_line with given arg
+			## Move to the next argument
+			shift
+			## Define var
+			readonly kernel_command_line="${1}"
+			;;
+		-f|--fs|--root-fs )                   ## Define root_fstype with given arg
+			## Move to the next argument
+			shift
+			## Define var
+			readonly root_fstype="${1}"
+			;;
+		-u|--uuid|--root-uuid )               ## Define root_uuid with given arg
+			## Move to the next argument
+			shift
+			## Define var
+			readonly root_uuid="${1}"
+			;;
+		## UEFI entry OPTIONS
+		-l|--label )                          ## Define efi_base_label with given arg
+			## Move to the next argument
+			shift
+			## Define var
+			readonly efi_base_label="${1}"
+			;;
+		-m|--mount-path|--esp )               ## Define efi_mount_path with given arg
+			## Move to the next argument
+			shift
+			## Define var
+			readonly efi_mount_path="${1}"
+			;;
+		* )                                   ## unknow option
+			printf '%b\n' "${RED}Invalid option: ${1}${RESET}"
+			printf '%b\n' "---"
+			usage
+			exit 1
+			;;
+	esac
+
+	debug_message "| ${RED}${1}${COLOR_DEBUG} option managed."
+
+	## Move to the next argument
+	shift
+	manage_arg=$((manage_arg+1))
+
+	done
+
+	debug_message "| ${RED}${manage_arg}${COLOR_DEBUG} argument(s) successfully managed."
+else
+	debug_message "| No arguments/options to manage."
+fi
+
+	debug_message "--- Manage argument END"
+# }}}
+
+main
+
+exit 0