cmake: Add support for systemd integration on Linux operating systems

Previously, only the Autotools build system could do this. This commit
includes most of the same features as in the Autotools build, although
not the user-session semantics, which will be added separately.

Systemd support is controlled by the cmake variable ENABLE_SYSTEMD, which can
have the values OFF, ON and AUTO, the latter enabling support by default if
the required libraries are available.

With WITH_SYSTEMD_SYSTEMUNITDIR a custom installation location can be specified.
If it is not specified, the related install path is determined from the installed
systemd package, if present.

6 files changed, 110 insertions, 2 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index a0095ebb..48cf9675 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -52,6 +52,10 @@ set(BUILD_TIMESTAMP ${DBUS_BUILD_TIMESTAMP})
 
 ########### basic vars ###############
 
+if(UNIX AND CMAKE_SYSTEM_NAME STREQUAL "Linux")
+    set(DBUS_LINUX 1)
+endif()
+
 include(GNUInstallDirs)
 
 if(DBUSDIR)
@@ -135,6 +139,35 @@ option(DBUS_DISABLE_ASSERT "Disable assertion checking" OFF)
 option(DBUS_ENABLE_STATS "enable bus daemon usage statistics" OFF)
 option(DBUS_ENABLE_CONTAINERS "enable restricted servers for app-containers" OFF)
 
+if(DBUS_LINUX)
+    add_auto_option(ENABLE_SYSTEMD "build with systemd at_console support" AUTO)
+    include(FindPkgConfig)
+    pkg_check_modules(SYSTEMD libsystemd>=209)
+    if(NOT SYSTEMD_FOUND)
+        pkg_check_modules(SYSTEMD libsystemd-login>=32 libsystemd-daemon>=32 libsystemd-journal>=32)
+    endif()
+    check_auto_option(ENABLE_SYSTEMD "systemd support" SYSTEMD_FOUND "systemd")
+    if(ENABLE_SYSTEMD AND SYSTEMD_FOUND)
+        set(DBUS_BUS_ENABLE_SYSTEMD ON)
+        set(HAVE_SYSTEMD ${SYSTEMD_FOUND})
+    endif()
+    add_path_option(WITH_SYSTEMD_SYSTEMUNITDIR "Directory for systemd service files" "")
+    # get defaults
+    pkg_check_modules(_SYSTEMD systemd)
+    if(_SYSTEMD_FOUND)
+        pkg_get_variable(_SYSTEMD_PREFIX systemd prefix)
+        pkg_get_variable(_SYSTEMD_SYSTEMUNITDIR systemd systemdsystemunitdir)
+        pkg_get_variable(_SYSTEMD_USERUNITDIR systemd systemduserunitdir)
+        # remove install prefix, which may not match the current prefix
+        string(REPLACE "${_SYSTEMD_PREFIX}/" "" DBUS_SYSTEMD_SYSTEMUNITDIR ${_SYSTEMD_SYSTEMUNITDIR})
+    else()
+        set(DBUS_SYSTEMD_SYSTEMUNITDIR lib/systemd/system)
+    endif()
+    if(WITH_SYSTEMD_SYSTEMUNITDIR)
+        set(DBUS_SYSTEMD_SYSTEMUNITDIR ${WITH_SYSTEMD_SYSTEMUNITDIR})
+    endif()
+endif()
+
 if(WIN32)
     set(FD_SETSIZE "8192" CACHE STRING "The maximum number of connections that can be handled at once")
 endif()
@@ -609,6 +642,8 @@ message("        Building bus stats API:   ${DBUS_ENABLE_STATS}                "
 message("        installing system libs:   ${DBUS_INSTALL_SYSTEM_LIBS}         ")
 message("        Building inotify support: ${DBUS_BUS_ENABLE_INOTIFY}          ")
 message("        Building kqueue support:  ${DBUS_BUS_ENABLE_KQUEUE}           ")
+message("        Building systemd support: ${DBUS_BUS_ENABLE_SYSTEMD}          ")
+message("        systemd system install dir:${DBUS_SYSTEMD_SYSTEMUNITDIR}      ")
 message("        Building Doxygen docs:    ${DBUS_ENABLE_DOXYGEN_DOCS}         ")
 message("        Building Qt help docs:    ${DBUS_ENABLE_QTHELP_DOCS}          ")
 message("        Building XML docs:        ${DBUS_ENABLE_XML_DOCS}             ")
@@ -679,7 +714,6 @@ add_custom_target(help-options
 #
 if(DBUS_ENABLE_PKGCONFIG)
     set(PLATFORM_LIBS pthread ${LIBRT})
-    include(FindPkgConfig QUIET)
     if(PKG_CONFIG_FOUND)
         # convert lists of link libraries into -lstdc++ -lm etc..
         foreach(LIB ${CMAKE_C_IMPLICIT_LINK_LIBRARIES} ${PLATFORM_LIBS})
diff --git a/README.cmake b/README.cmake
index e6bc9725..0b32fdca 100644
--- a/README.cmake
+++ b/README.cmake
@@ -149,6 +149,12 @@ DBUS_ENABLE_STATS:BOOL=OFF
 // enable restricted servers for app containers
 DBUS_ENABLE_CONTAINERS:BOOL=OFF
 
+// build with systemd at_console support
+ENABLE_SYSTEMD:STRING=AUTO
+
+// Directory for systemd service files
+WITH_SYSTEMD_SYSTEMUNITDIR:STRING=
+
 // support verbose debug mode
 DBUS_ENABLE_VERBOSE_MODE:BOOL=ON
 
diff --git a/bus/CMakeLists.txt b/bus/CMakeLists.txt
index 5d76573d..2aa6068d 100644
--- a/bus/CMakeLists.txt
+++ b/bus/CMakeLists.txt
@@ -169,6 +169,13 @@ if(NOT WIN32)
     install_example_file(example-system-hardening-without-traditional-activation.conf)
 endif()
 
+if(DBUS_BUS_ENABLE_SYSTEMD)
+    configure_file(dbus.socket.in ${CMAKE_CURRENT_BINARY_DIR}/dbus.socket)
+    configure_file(dbus.service.in ${CMAKE_CURRENT_BINARY_DIR}/dbus.service)
+    add_systemd_service(${CMAKE_CURRENT_BINARY_DIR}/dbus.socket PATH ${DBUS_SYSTEMD_SYSTEMUNITDIR} LINKS sockets.target.wants)
+    add_systemd_service(${CMAKE_CURRENT_BINARY_DIR}/dbus.service PATH ${DBUS_SYSTEMD_SYSTEMUNITDIR} LINKS multi-user.target.wants)
+endif()
+
 ## mop up the gcov files
 #clean-local:
 #	/bin/rm *.bb *.bbg *.da *.gcov || true
diff --git a/cmake/config.h.cmake b/cmake/config.h.cmake
index 1bc545a9..cbffcfa9 100644
--- a/cmake/config.h.cmake
+++ b/cmake/config.h.cmake
@@ -227,6 +227,7 @@
 #cmakedefine HAVE_RAISE 1
 #cmakedefine HAVE_SETRLIMIT 1
 #cmakedefine HAVE_UNIX_FD_PASSING 1
+#cmakedefine HAVE_SYSTEMD
 
 /* Define to use epoll(4) on Linux */
 #cmakedefine DBUS_HAVE_LINUX_EPOLL 1
diff --git a/cmake/modules/Macros.cmake b/cmake/modules/Macros.cmake
index 9db3bfb0..caf4372c 100644
--- a/cmake/modules/Macros.cmake
+++ b/cmake/modules/Macros.cmake
@@ -233,3 +233,63 @@ macro(check_auto_option _name _text _var _vartext)
         message(FATAL_ERROR "${_text} requested but ${_vartext} not found")
     endif()
 endmacro()
+
+#
+# Provide option that takes a path
+#
+macro(add_path_option _name _text _default)
+    if(NOT DEFINED ${_name})
+        set(${_name} ${_default} CACHE STRING "${_text}" FORCE)
+    else()
+        set(${_name} ${_default} CACHE STRING "${_text}")
+    endif()
+endmacro()
+
+#
+# create directory on install
+#
+macro(install_dir filepath)
+    install(CODE "
+    set(_path \"\$ENV{DESTDIR}\${CMAKE_INSTALL_PREFIX}/${filepath}\")
+    if(NOT EXISTS \"\${_path}\")
+        execute_process(COMMAND ${CMAKE_COMMAND} -E make_directory \"\${_path}\")
+        message(\"-- Creating directory: \${_path}\")
+    else()
+        message(\"-- Up-to-date: \${_path}\")
+    endif()
+    ")
+endmacro()
+
+#
+# create symlink on install
+#
+macro(install_symlink filepath sympath)
+    install(CODE "
+    set(_sympath \"\$ENV{DESTDIR}\${CMAKE_INSTALL_PREFIX}/${sympath}\")
+    file(REMOVE \"\${_sympath}\")
+    execute_process(COMMAND ${CMAKE_COMMAND} -E create_symlink \"${filepath}\" \"\${_sympath}\" RESULT_VARIABLE result)
+    if(NOT result)
+        message(\"-- Creating symlink: \${_sympath} -> ${filepath}\")
+    else()
+        message(FATAL ERROR \"-- Failed to create symlink: \${_sympath} -> ${filepath}\")
+    endif()
+    ")
+endmacro()
+
+#
+# add system service <file> PATH <install path> LINKS [multi-user.target.wants [...]]
+#
+macro(add_systemd_service file)
+    set(options)
+    set(oneValueArgs PATH)
+    set(multiValueArgs LINKS)
+    cmake_parse_arguments(_ "${options}" "${oneValueArgs}" "${multiValueArgs}" ${ARGN})
+    set(_targetdir ${__PATH})
+    install(FILES ${file} DESTINATION ${_targetdir})
+    get_filename_component(_name ${file} NAME)
+    foreach(l ${__LINKS})
+        set(_linkdir ${_targetdir}/${l})
+        install_dir(${_linkdir})
+        install_symlink(../${_name} ${_linkdir}/${_name})
+    endforeach()
+endmacro()
diff --git a/dbus/CMakeLists.txt b/dbus/CMakeLists.txt
index 972e05c1..63070b69 100644
--- a/dbus/CMakeLists.txt
+++ b/dbus/CMakeLists.txt
@@ -281,7 +281,7 @@ else(WIN32)
     if(DEFINED DBUS_LIBRARY_REVISION)
         set_target_properties(dbus-1 PROPERTIES VERSION ${DBUS_LIBRARY_MAJOR}.${DBUS_LIBRARY_AGE}.${DBUS_LIBRARY_REVISION} SOVERSION ${DBUS_LIBRARY_MAJOR})
     endif()
-    target_link_libraries(dbus-1 ${CMAKE_THREAD_LIBS_INIT})
+    target_link_libraries(dbus-1 ${CMAKE_THREAD_LIBS_INIT} ${SYSTEMD_LIBRARIES})
     if(LIBRT)
         target_link_libraries(dbus-1 ${LIBRT})
     endif()