rpm: use a helper script to actually invoke systemctl commands

Instead of embedding the commands to invoke directly in the macros,
let's use a helper script as indirection. This has a couple of advantages:

- the macro language is awkward, we need to suffix most commands by "|| :"
  and "\", which is easy to get wrong. In the new scheme, the macro becomes
  a single simple command.
- in the script we can use normal syntax highlighting, shellcheck, etc.
- it's also easier to test the invoked commands by invoking the helper
  manually.
- most importantly, the logic is contained in the helper, i.e. we can
  update systemd rpm and everything uses the new helper. Before, we would
  have to rebuild all packages to update the macro definition.

This raises the question whether it makes sense to use the lua scriptlets when
the real work is done in a bash script. I think it's OK: we still have the
efficient lua scripts that do the short scripts, and we use a single shared
implementation in bash to do the more complex stuff.

The meson version is raised to 0.47 because that's needed for install_mode.
We were planning to raise the required version anyway…

README

@@ -193,7 +193,7 @@ REQUIREMENTS:
         python-jinja2
         python-lxml (optional, required to build the indices)
         python >= 3.5
-        meson >= 0.46 (>= 0.49 is required to build position-independent executables)
+        meson >= 0.47 (>= 0.49 is required to build position-independent executables)
         ninja
         gcc, awk, sed, grep, and similar tools
         clang >= 10.0, llvm >= 10.0 (optional, required to build BPF programs

meson.build

@@ -10,7 +10,7 @@ project('systemd', 'c',
                 'localstatedir=/var',
                 'warning_level=2',
         ],
-        meson_version : '>= 0.46',
+        meson_version : '>= 0.47',
        )
 
 libsystemd_version = '0.32.0'
@@ -253,6 +253,7 @@ conf.set_quoted('SYSTEMD_SHUTDOWN_BINARY_PATH',               join_paths(rootlib
 conf.set_quoted('SYSTEMD_STDIO_BRIDGE_BINARY_PATH',           join_paths(bindir, 'systemd-stdio-bridge'))
 conf.set_quoted('SYSTEMD_TEST_DATA',                          join_paths(testsdir, 'testdata'))
 conf.set_quoted('SYSTEMD_TTY_ASK_PASSWORD_AGENT_BINARY_PATH', join_paths(rootbindir, 'systemd-tty-ask-password-agent'))
+conf.set_quoted('SYSTEMD_UPDATE_HELPER_PATH',                 join_paths(rootlibexecdir, 'systemd-update-helper'))
 conf.set_quoted('SYSTEMD_USERWORK_PATH',                      join_paths(rootlibexecdir, 'systemd-userwork'))
 conf.set_quoted('SYSTEMD_VERITYSETUP_PATH',                   join_paths(rootlibexecdir, 'systemd-veritysetup'))
 conf.set_quoted('SYSTEM_CONFIG_UNIT_DIR',                     join_paths(pkgsysconfdir, 'system'))

src/rpm/macros.systemd.in

@@ -46,31 +46,33 @@ OrderWithRequires(postun): systemd \
 
 %systemd_post() \
 %{expand:%%{?__systemd_someargs_%#:%%__systemd_someargs_%# systemd_post}} \
-if [ $1 -eq 1 ] && command -v systemctl >/dev/null; then \
+if [ $1 -eq 1 ] && [ -x "{{SYSTEMD_UPDATE_HELPER_PATH}}" ]; then \
     # Initial installation \
-    systemctl --no-reload preset %{?*} || : \
+    {{SYSTEMD_UPDATE_HELPER_PATH}} install-system-units %{?*} || : \
 fi \
 %{nil}
 
-%systemd_user_post() %{expand:%systemd_post \\--global %%{?*}}
+%systemd_user_post() \
+%{expand:%%{?__systemd_someargs_%#:%%__systemd_someargs_%# systemd_user_post}} \
+if [ $1 -eq 1 ] && [ -x "{{SYSTEMD_UPDATE_HELPER_PATH}}" ]; then \
+    # Initial installation \
+    {{SYSTEMD_UPDATE_HELPER_PATH}} install-user-units %{?*} || : \
+fi \
+%{nil}
 
 %systemd_preun() \
 %{expand:%%{?__systemd_someargs_%#:%%__systemd_someargs_%# systemd_preun}} \
-if [ $1 -eq 0 ] && command -v systemctl >/dev/null; then \
+if [ $1 -eq 0 ] && [ -x "{{SYSTEMD_UPDATE_HELPER_PATH}}" ]; then \
     # Package removal, not upgrade \
-    if [ -d /run/systemd/system ]; then \
-          systemctl --no-reload disable --now %{?*} || : \
-    else \
-          systemctl --no-reload disable %{?*} || : \
-    fi \
+    {{SYSTEMD_UPDATE_HELPER_PATH}} remove-system-units %{?*} || : \
 fi \
 %{nil}
 
 %systemd_user_preun() \
 %{expand:%%{?__systemd_someargs_%#:%%__systemd_someargs_%# systemd_user_preun}} \
-if [ $1 -eq 0 ] && command -v systemctl >/dev/null; then \
+if [ $1 -eq 0 ] && [ -x "{{SYSTEMD_UPDATE_HELPER_PATH}}" ]; then \
     # Package removal, not upgrade \
-    systemctl --global disable %{?*} || : \
+    {{SYSTEMD_UPDATE_HELPER_PATH}} remove-user-units %{?*} || : \
 fi \
 %{nil}
 
@@ -84,11 +86,9 @@ fi \
 
 %systemd_postun_with_restart() \
 %{expand:%%{?__systemd_someargs_%#:%%__systemd_someargs_%# systemd_postun_with_restart}} \
-if [ $1 -ge 1 ] && command -v systemctl >/dev/null; then \
+if [ $1 -ge 1 ] && [ -x "{{SYSTEMD_UPDATE_HELPER_PATH}}" ]; then \
     # Package upgrade, not uninstall \
-    for unit in %{?*}; do \
-        systemctl set-property $unit Markers=+needs-restart || : \
-    done \
+    {{SYSTEMD_UPDATE_HELPER_PATH}} mark-restart-system-units %{?*} || : \
 fi \
 %{nil}
 

src/rpm/meson.build

@@ -1,9 +1,13 @@
 # SPDX-License-Identifier: LGPL-2.1-or-later
 
 in_files = [
-        ['macros.systemd',      rpmmacrosdir != 'no'],
-        ['triggers.systemd',    false],
-        ['triggers.systemd.sh', false]]
+        ['macros.systemd',        rpmmacrosdir != 'no', rpmmacrosdir],
+
+        # we conditionalize on rpmmacrosdir, but install into rootlibexecdir
+        ['systemd-update-helper', rpmmacrosdir != 'no', rootlibexecdir, 'rwxr-xr-x'],
+
+        ['triggers.systemd',      false],
+        ['triggers.systemd.sh',   false]]
 
 # The last two don't get installed anywhere, one of them needs to included in
 # the rpm spec file definition instead.
@@ -17,6 +21,7 @@ foreach tuple : in_files
                 command : [meson_render_jinja2, config_h, '@INPUT@'],
                 capture : true,
                 install : tuple[1],
-                install_dir : rpmmacrosdir,
+                install_dir : tuple.length() > 2 ? tuple[2] : '',
+                install_mode : tuple.length() > 3 ? tuple[3] : false,
                 build_by_default : true)
 endforeach

src/rpm/systemd-update-helper.in

@@ -0,0 +1,60 @@
+#!/bin/bash
+set -eu
+set -o pipefail
+
+command="${1:?}"
+shift
+
+command -v systemctl >/dev/null || exit 0
+
+case "$command" in
+    install-system-units)
+        systemctl --no-reload preset "$@"
+        ;;
+
+    install-user-units)
+        systemctl --no-reload preset --global "$@"
+        ;;
+
+    remove-system-units)
+        if [ -d /run/systemd/system ]; then
+            systemctl --no-reload disable --now "$@"
+        else
+            systemctl --no-reload disable "$@"
+        fi
+        ;;
+
+    remove-user-units)
+        systemctl --global disable "$@"
+        ;;
+
+    mark-restart-system-units)
+        [ -d /run/systemd/system ] || exit 0
+
+        for unit in "$@"; do
+            systemctl set-property "$unit" Markers=+needs-restart || :
+        done
+        ;;
+
+    system-reload-restart|system-reload|system-restart)
+        if [ -n "$*" ]; then
+            echo "Unexpected arguments for '$command': $*"
+            exit 2
+        fi
+
+        [ -d /run/systemd/system ] || exit 0
+
+        if [[ "$command" =~ reload ]]; then
+            systemctl daemon-reload
+        fi
+
+        if [[ "$command" =~ restart ]]; then
+            systemctl reload-or-restart --marked
+        fi
+        ;;
+
+    *)
+        echo "Unknown verb '$command'"
+        exit 3
+        ;;
+esac

src/rpm/triggers.systemd.in

@@ -13,20 +13,11 @@
 -- upgraded. We care about the case where a package is initially
 -- installed, because other cases are covered by the *un scriptlets,
 -- so sometimes we will reload needlessly.
-if posix.access("/run/systemd/system") then
-    pid = posix.fork()
-    if pid == 0 then
-        assert(posix.execp("systemctl", "daemon-reload"))
-    elseif pid > 0 then
-        posix.wait(pid)
-    end
-
-    pid = posix.fork()
-    if pid == 0 then
-        assert(posix.execp("systemctl", "reload-or-restart", "--marked"))
-    elseif pid > 0 then
-        posix.wait(pid)
-    end
+pid = posix.fork()
+if pid == 0 then
+    assert(posix.exec("{{SYSTEMD_UPDATE_HELPER_PATH}}", "system-reload-restart"))
+elseif pid > 0 then
+    posix.wait(pid)
 end
 
 %transfiletriggerpostun -P 1000100 -p <lua> -- {{SYSTEM_DATA_UNIT_DIR}} /etc/systemd/system
@@ -35,24 +26,20 @@ end
 -- On upgrade, we need to run daemon-reload after any new unit files
 -- have been installed, but before %postun scripts in packages get
 -- executed.
-if posix.access("/run/systemd/system") then
-    pid = posix.fork()
-    if pid == 0 then
-        assert(posix.execp("systemctl", "daemon-reload"))
-    elseif pid > 0 then
-        posix.wait(pid)
-    end
+pid = posix.fork()
+if pid == 0 then
+    assert(posix.exec("{{SYSTEMD_UPDATE_HELPER_PATH}}", "system-reload"))
+elseif pid > 0 then
+    posix.wait(pid)
 end
 
 %transfiletriggerpostun -P 10000 -p <lua> -- {{SYSTEM_DATA_UNIT_DIR}} /etc/systemd/system
 -- We restart remaining services that should be restarted here.
-if posix.access("/run/systemd/system") then
-    pid = posix.fork()
-    if pid == 0 then
-        assert(posix.execp("systemctl", "reload-or-restart", "--marked"))
-    elseif pid > 0 then
-        posix.wait(pid)
-    end
+pid = posix.fork()
+if pid == 0 then
+    assert(posix.exec("{{SYSTEMD_UPDATE_HELPER_PATH}}", "system-restart"))
+elseif pid > 0 then
+    posix.wait(pid)
 end
 
 %transfiletriggerin -P 100700 -p <lua> -- {{SYSUSERS_DIR}}

src/rpm/triggers.systemd.sh.in

@@ -14,10 +14,7 @@
 # upgraded. We care about the case where a package is initially
 # installed, because other cases are covered by the *un scriptlets,
 # so sometimes we will reload needlessly.
-if test -d "/run/systemd/system"; then
-  systemctl daemon-reload || :
-  systemctl reload-or-restart --marked || :
-fi
+{{SYSTEMD_UPDATE_HELPER_PATH}} system-reload-restart || :
 
 %transfiletriggerpostun -P 1000100 -- {{SYSTEM_DATA_UNIT_DIR}} /etc/systemd/system
 # On removal, we need to run daemon-reload after any units have been
@@ -25,15 +22,11 @@ fi
 # On upgrade, we need to run daemon-reload after any new unit files
 # have been installed, but before %postun scripts in packages get
 # executed.
-if test -d "/run/systemd/system"; then
-  systemctl daemon-reload || :
-fi
+{{SYSTEMD_UPDATE_HELPER_PATH}} system-reload || :
 
 %transfiletriggerpostun -P 10000 -- {{SYSTEM_DATA_UNIT_DIR}} /etc/systemd/system
 # We restart remaining services that should be restarted here.
-if test -d "/run/systemd/system"; then
-  systemctl reload-or-restart --marked || :
-fi
+{{SYSTEMD_UPDATE_HELPER_PATH}} system-restart || :
 
 %transfiletriggerin -P 1000700 -- {{SYSUSERS_DIR}}
 # This script will process files installed in {{SYSUSERS_DIR}} to create