python: setup: arch: Switch to systemd-boot if necessary

Signed-off-by: Nathan Chancellor <[email protected]>

python/setup/arch.py

@@ -3,6 +3,7 @@
 # Copyright (C) 2022-2023 Nathan Chancellor
 
 from argparse import ArgumentParser
+from collections import UserDict
 import getpass
 import os
 from pathlib import Path
@@ -29,6 +30,27 @@
             UCODE_VENDOR = 'intel'
 
 
+class CmdlineOptions(UserDict):
+
+    def __init__(self, initial_argument):
+        if isinstance(initial_argument, str):
+            super().__init__()
+
+            for item in initial_argument.split(' '):
+                if item := item.strip():
+                    if '=' in item:
+                        key, value = item.split('=', maxsplit=1)
+                    else:
+                        key, value = item, None
+                    self.data[key] = value
+        else:
+            super().__init__(initial_argument)
+
+    def __str__(self):
+        return ' '.join(
+            sorted(f"{key}={value}" if value else key for key, value in self.data.items()))
+
+
 def add_mods_to_mkinitcpio(modules):
     mkinitcpio_conf, conf_text = lib.utils.path_and_text('/etc/mkinitcpio.conf')
 
@@ -101,8 +123,10 @@ def configure_systemd_boot(init=True, conf='linux.conf'):
         systemd_boot_update_hook.write_text(systemd_boot_update_hook_txt, encoding='utf-8')
         systemd_boot_update_hook.chmod(0o644)
 
-    # If we already set up the configuration, no need to go through all this
-    # again, unless we are not doing the initial configuration
+    # If we already set up the configuration (either via this function or
+    # switch_to_systemd_boot(), depending on what setup was installed prior to
+    # running this setup), no need to go through all this again, unless we are
+    # not doing the initial configuration
     if (linux_conf := (boot_entries := Path('/boot/loader/entries')) / conf).exists() and init:
         return
 
@@ -119,23 +143,13 @@ def configure_systemd_boot(init=True, conf='linux.conf'):
     linux_conf_text = linux_conf.read_text(encoding='utf-8')
     if not (match := re.search('^options (.*)$', linux_conf_text, flags=re.M)):
         raise RuntimeError(f"Could not find 'options' line in {linux_conf}?")
-    current_options_str = match.groups()[0]
-    current_options = {opt for elem in current_options_str.split(' ') if (opt := elem.strip())}
-    new_options = current_options.copy()
-
-    # Add 'console=' if necessary (when connected by serial console in a
-    # virtual machine)
-    if lib.setup.is_virtual_machine() and 'DISPLAY' not in os.environ:
-        new_options.add('console=ttyS0,115200n8')
-
-    # Enable the performance governor
-    new_options.add('cpufreq.default_governor=performance')
+    current_options = CmdlineOptions(match.groups()[0])
 
-    # Mitigate SMT RSB vulnerability
-    new_options.add('kvm.mitigate_smt_rsb=1')
+    new_options = current_options.copy()
+    new_options.update(get_cmdline_additions())
 
     if current_options != new_options:
-        new_text = linux_conf_text.replace(current_options_str, ' '.join(sorted(new_options)))
+        new_text = linux_conf_text.replace(str(current_options), str(new_options))
         linux_conf.write_text(new_text, encoding='utf-8')
 
     # Ensure that the new configuration is the default on the machine.
@@ -189,6 +203,20 @@ def fix_fstab():
     subprocess.run(['dos2unix', '/etc/fstab'], check=True)
 
 
+def get_cmdline_additions():
+    options = CmdlineOptions({
+        # Enable the performance governor
+        'cpufreq.default_governor': 'performance',
+        # Mitigate SMT RSB vulnerability
+        'kvm.mitigate_smt_rsb': '1',
+    })
+    # Add 'console=' if necessary (when connected by serial console in a
+    # virtual machine)
+    if lib.setup.is_virtual_machine() and 'DISPLAY' not in os.environ:
+        options['console'] = 'ttyS0,115200n8'
+    return options
+
+
 def pacman_install(subargs):
     lib.setup.pacman(['-S', '--noconfirm', *subargs])
 
@@ -465,6 +493,79 @@ def setup_user(username, userpass):
     lib.setup.setup_ssh_authorized_keys(username)
 
 
+def switch_to_systemd_boot(dryrun=False):
+    # If we are not booted in UEFI mode, we cannot switch to systemd-boot
+    if not Path('/sys/firmware/efi').exists():
+        return
+
+    # If systemd-boot is already installed, we are good to go
+    if lib.setup.using_systemd_boot():
+        return
+
+    # Install systemd-boot to ESP
+    if dryrun:
+        print('$ bootctl install')
+    else:
+        subprocess.run(['bootctl', 'install'], check=True)
+
+    # Create initial loader.conf
+    loader_conf_txt = 'default linux.conf\ntimeout 3\n'
+    if dryrun:
+        print('$ mkdir /boot/loader')
+        print(f"$ echo '{loader_conf_txt}' > /boot/loader/loader.conf")
+    else:
+        Path('/boot/loader').mkdir(exist_ok=True)
+        Path('/boot/loader/loader.conf').write_text(loader_conf_txt, encoding='utf-8')
+
+    # Get partition UUID and filesystem type of /
+    partuuid, fstype = subprocess.run(['findmnt', '-n', '-o', 'PARTUUID,FSTYPE', '/'],
+                                      capture_output=True,
+                                      check=True,
+                                      text=True).stdout.strip().split(' ')
+
+    # Default cmdline options
+    cmdline_options = CmdlineOptions({
+        'root': f"PARTUUID={partuuid}",
+        'rootfstype': fstype,
+        'rw': None,
+    })
+    cmdline_options.update(get_cmdline_additions())
+    # Copy over any cmdline options that we added in grub, as those might be
+    # necessary for the machine to work properly.
+    if (grub_default := Path('/etc/default/grub')).exists():
+        grub_default_txt = grub_default.read_text(encoding='utf-8')
+        if match := re.search('^GRUB_CMDLINE_LINUX_DEFAULT="(.*)"$', grub_default_txt, flags=re.M):
+            default_skip = (
+                'loglevel=',  # I do not mind seeing logs
+                'quiet',  # I do not mind the boot up noise
+            )
+            filtered_str = ' '.join(item for item in match.groups()[0].split(' ')
+                                    if not item.startswith(default_skip))
+            cmdline_options.update(CmdlineOptions(filtered_str))
+        if match := re.search('^GRUB_CMDLINE_LINUX="(.*)"$', grub_default_txt, flags=re.M):
+            cmdline_options.update(CmdlineOptions(match.groups()[0]))
+
+    # Create initial linux.conf
+    linux_conf_txt = (
+        'title Arch Linux (linux)\n'
+        'linux /vmlinuz-linux\n'
+        f"initrd /{UCODE_VENDOR}-ucode.img\n" if UCODE_VENDOR else '',
+        'initrd /initramfs-linux.img\n'
+        f"options {' '.join(sorted(cmdline_options))}\n",
+    )
+    if dryrun:
+        print('$ mkdir /boot/loader/entries')
+        print(f"$ echo '{linux_conf_txt}' > /boot/loader/entries/linux.conf")
+    else:
+        Path('/boot/loader/entries').mkdir(exist_ok=True)
+        Path('/boot/loader/entries/linux.conf').write_text(linux_conf_txt, encoding='utf-8')
+
+        # Remove grub
+        lib.setup.remove_if_installed('grub')
+        if (boot_grub := Path('/boot/grub')).exists():
+            shutil.rmtree(boot_grub)
+
+
 def uncomment_pacman_option(conf, option, old_value=None, new_value=None):
     if old_value and new_value:
         return re.sub(f"^#{option} = {old_value}", f"{option} = {new_value}", conf, flags=re.M)
@@ -502,6 +603,7 @@ def vmware_adjustments():
         password = getpass.getpass(prompt='Password for Arch Linux user account: ')
 
     prechecks()
+    switch_to_systemd_boot()
     configure_systemd_boot()
     pacman_settings()
     pacman_key_setup()