turn kdbus support into a runtime option

./configure --enable/disable-kdbus can be used to set the default
behavior regarding kdbus.

If no kdbus kernel support is available, dbus-dameon will be used.

With --enable-kdbus, the kernel command line option "kdbus=0" can
be used to disable kdbus.

With --disable-kdbus, the kernel command line option "kdbus=1" is
required to enable kdbus support.

13 files changed, 17 insertions, 60 deletions

diff --git a/src/basic/def.h b/src/basic/def.h
index 011c7c667e..5aaba1fe87 100644
--- a/src/basic/def.h
+++ b/src/basic/def.h
@@ -63,13 +63,7 @@
 
 #define UNIX_SYSTEM_BUS_ADDRESS "unix:path=/var/run/dbus/system_bus_socket"
 #define KERNEL_SYSTEM_BUS_ADDRESS "kernel:path=/sys/fs/kdbus/0-system/bus"
-
-#ifdef ENABLE_KDBUS
-#  define DEFAULT_SYSTEM_BUS_ADDRESS KERNEL_SYSTEM_BUS_ADDRESS ";" UNIX_SYSTEM_BUS_ADDRESS
-#else
-#  define DEFAULT_SYSTEM_BUS_ADDRESS UNIX_SYSTEM_BUS_ADDRESS
-#endif
-
+#define DEFAULT_SYSTEM_BUS_ADDRESS KERNEL_SYSTEM_BUS_ADDRESS ";" UNIX_SYSTEM_BUS_ADDRESS
 #define UNIX_USER_BUS_ADDRESS_FMT "unix:path=%s/bus"
 #define KERNEL_USER_BUS_ADDRESS_FMT "kernel:path=/sys/fs/kdbus/"UID_FMT"-user/bus"
 
diff --git a/src/bus-proxyd/bus-proxyd.c b/src/bus-proxyd/bus-proxyd.c
index 3e398b53e9..3cc3b33ae7 100644
--- a/src/bus-proxyd/bus-proxyd.c
+++ b/src/bus-proxyd/bus-proxyd.c
@@ -239,11 +239,7 @@ static int parse_argv(int argc, char *argv[]) {
                         if (!e)
                                 return log_oom();
 
-#ifdef ENABLE_KDBUS
                         a = strjoin("x-machine-kernel:machine=", e, ";x-machine-unix:machine=", e, NULL);
-#else
-                        a = strjoin("x-machine-unix:machine=", e, NULL);
-#endif
                         if (!a)
                                 return log_oom();
 
diff --git a/src/bus-proxyd/stdio-bridge.c b/src/bus-proxyd/stdio-bridge.c
index 61bc08ae33..f275f6705f 100644
--- a/src/bus-proxyd/stdio-bridge.c
+++ b/src/bus-proxyd/stdio-bridge.c
@@ -110,11 +110,7 @@ static int parse_argv(int argc, char *argv[]) {
                         if (!e)
                                 return log_oom();
 
-#ifdef ENABLE_KDBUS
                         a = strjoin("x-machine-kernel:machine=", e, ";x-machine-unix:machine=", e, NULL);
-#else
-                        a = strjoin("x-machine-unix:machine=", e, NULL);
-#endif
                         if (!a)
                                 return log_oom();
 
diff --git a/src/core/execute.c b/src/core/execute.c
index a6ff5ac56e..94cc101738 100644
--- a/src/core/execute.c
+++ b/src/core/execute.c
@@ -1514,7 +1514,6 @@ static int exec_child(
                 }
         }
 
-#ifdef ENABLE_KDBUS
         if (params->bus_endpoint_fd >= 0 && context->bus_endpoint) {
                 uid_t ep_uid = (uid == UID_INVALID) ? 0 : uid;
 
@@ -1524,7 +1523,6 @@ static int exec_child(
                         return r;
                 }
         }
-#endif
 
         /* If delegation is enabled we'll pass ownership of the cgroup
          * (but only in systemd's own controller hierarchy!) to the
diff --git a/src/core/kmod-setup.c b/src/core/kmod-setup.c
index f5584b6b14..e7a6bdc8c4 100644
--- a/src/core/kmod-setup.c
+++ b/src/core/kmod-setup.c
@@ -66,10 +66,8 @@ int kmod_setup(void) {
                 /* this should never be a module */
                 { "unix",      "/proc/net/unix",            true,   true,    NULL      },
 
-#ifdef ENABLE_KDBUS
                 /* IPC is needed before we bring up any other services */
                 { "kdbus",     "/sys/fs/kdbus",             false,  false,   is_kdbus_wanted },
-#endif
 
 #ifdef HAVE_LIBIPTC
                 /* netfilter is needed by networkd, nspawn among others, and cannot be autoloaded */
diff --git a/src/core/load-fragment-gperf.gperf.m4 b/src/core/load-fragment-gperf.gperf.m4
index 66c9145aa6..aae81c80cb 100644
--- a/src/core/load-fragment-gperf.gperf.m4
+++ b/src/core/load-fragment-gperf.gperf.m4
@@ -229,9 +229,7 @@ Service.BusName,                 config_parse_bus_name,              0,
 Service.FileDescriptorStoreMax,  config_parse_unsigned,              0,                             offsetof(Service, n_fd_store_max)
 Service.NotifyAccess,            config_parse_notify_access,         0,                             offsetof(Service, notify_access)
 Service.Sockets,                 config_parse_service_sockets,       0,                             0
-m4_ifdef(`ENABLE_KDBUS',
-`Service.BusPolicy,              config_parse_bus_endpoint_policy,   0,                             offsetof(Service, exec_context)',
-`Service.BusPolicy,              config_parse_warn_compat,           DISABLED_EXPERIMENTAL,         0')
+Service.BusPolicy,               config_parse_bus_endpoint_policy,   0,                             offsetof(Service, exec_context)
 EXEC_CONTEXT_CONFIG_ITEMS(Service)m4_dnl
 CGROUP_CONTEXT_CONFIG_ITEMS(Service)m4_dnl
 KILL_CONTEXT_CONFIG_ITEMS(Service)m4_dnl
diff --git a/src/core/manager.c b/src/core/manager.c
index eb80dd1b46..a1f37bbbb3 100644
--- a/src/core/manager.c
+++ b/src/core/manager.c
@@ -731,7 +731,6 @@ static int manager_setup_notify(Manager *m) {
 }
 
 static int manager_setup_kdbus(Manager *m) {
-#ifdef ENABLE_KDBUS
         _cleanup_free_ char *p = NULL;
 
         assert(m);
@@ -749,7 +748,6 @@ static int manager_setup_kdbus(Manager *m) {
                 return log_debug_errno(m->kdbus_fd, "Failed to set up kdbus: %m");
 
         log_debug("Successfully set up kdbus on %s", p);
-#endif
 
         return 0;
 }
diff --git a/src/core/mount-setup.c b/src/core/mount-setup.c
index c35248eeae..42a6b952b9 100644
--- a/src/core/mount-setup.c
+++ b/src/core/mount-setup.c
@@ -104,10 +104,8 @@ static const MountPoint mount_table[] = {
         { "efivarfs",    "/sys/firmware/efi/efivars", "efivarfs",   NULL,                      MS_NOSUID|MS_NOEXEC|MS_NODEV,
           is_efi_boot,   MNT_NONE                   },
 #endif
-#ifdef ENABLE_KDBUS
         { "kdbusfs",    "/sys/fs/kdbus",             "kdbusfs",    NULL, MS_NOSUID|MS_NOEXEC|MS_NODEV,
           NULL,       MNT_IN_CONTAINER },
-#endif
 };
 
 /* These are API file systems that might be mounted by other software,
diff --git a/src/core/service.c b/src/core/service.c
index 71252e29e2..fa1e80b710 100644
--- a/src/core/service.c
+++ b/src/core/service.c
@@ -568,14 +568,12 @@ static int service_add_extras(Service *s) {
                 s->notify_access = NOTIFY_MAIN;
 
         if (s->bus_name) {
-#ifdef ENABLE_KDBUS
                 const char *n;
 
                 n = strjoina(s->bus_name, ".busname");
                 r = unit_add_dependency_by_name(UNIT(s), UNIT_AFTER, n, NULL, true);
                 if (r < 0)
                         return r;
-#endif
 
                 r = unit_watch_bus_name(UNIT(s), s->bus_name);
                 if (r < 0)
@@ -1180,7 +1178,6 @@ static int service_spawn(
         } else
                 path = UNIT(s)->cgroup_path;
 
-#ifdef ENABLE_KDBUS
         if (s->exec_context.bus_endpoint) {
                 r = bus_kernel_create_endpoint(UNIT(s)->manager->running_as == MANAGER_SYSTEM ? "system" : "user",
                                                UNIT(s)->id, &bus_endpoint_path);
@@ -1192,7 +1189,6 @@ static int service_spawn(
                  * as the service is running. */
                 exec_params.bus_endpoint_fd = s->bus_endpoint_fd = r;
         }
-#endif
 
         exec_params.argv = argv;
         exec_params.fds = fds;
diff --git a/src/libsystemd/sd-bus/sd-bus.c b/src/libsystemd/sd-bus/sd-bus.c
index 0881b4779a..b559ee9eb8 100644
--- a/src/libsystemd/sd-bus/sd-bus.c
+++ b/src/libsystemd/sd-bus/sd-bus.c
@@ -1239,18 +1239,9 @@ int bus_set_address_user(sd_bus *b) {
                 if (!ee)
                         return -ENOMEM;
 
-#ifdef ENABLE_KDBUS
                 (void) asprintf(&b->address, KERNEL_USER_BUS_ADDRESS_FMT ";" UNIX_USER_BUS_ADDRESS_FMT, getuid(), ee);
-#else
-                (void) asprintf(&b->address, UNIX_USER_BUS_ADDRESS_FMT, ee);
-#endif
-        } else {
-#ifdef ENABLE_KDBUS
+        } else
                 (void) asprintf(&b->address, KERNEL_USER_BUS_ADDRESS_FMT, getuid());
-#else
-                return -ECONNREFUSED;
-#endif
-        }
 
         if (!b->address)
                 return -ENOMEM;
@@ -1372,11 +1363,7 @@ int bus_set_address_system_machine(sd_bus *b, const char *machine) {
         if (!e)
                 return -ENOMEM;
 
-#ifdef ENABLE_KDBUS
         b->address = strjoin("x-machine-kernel:machine=", e, ";x-machine-unix:machine=", e, NULL);
-#else
-        b->address = strjoin("x-machine-unix:machine=", e, NULL);
-#endif
         if (!b->address)
                 return -ENOMEM;
 
diff --git a/src/login/pam_systemd.c b/src/login/pam_systemd.c
index b5d419000c..0ebdfdf19e 100644
--- a/src/login/pam_systemd.c
+++ b/src/login/pam_systemd.c
@@ -177,7 +177,6 @@ static int export_legacy_dbus_address(
                 uid_t uid,
                 const char *runtime) {
 
-#ifdef ENABLE_KDBUS
         _cleanup_free_ char *s = NULL;
         int r;
 
@@ -195,7 +194,7 @@ static int export_legacy_dbus_address(
                 pam_syslog(handle, LOG_ERR, "Failed to set bus variable.");
                 return r;
         }
-#endif
+
         return PAM_SUCCESS;
 }
 
diff --git a/src/machine/machine-dbus.c b/src/machine/machine-dbus.c
index 9f026beb13..7813a0bcc7 100644
--- a/src/machine/machine-dbus.c
+++ b/src/machine/machine-dbus.c
@@ -509,11 +509,7 @@ int bus_machine_method_open_login(sd_bus_message *message, void *userdata, sd_bu
         if (r < 0)
                 return r;
 
-#ifdef ENABLE_KDBUS
 #  define ADDRESS_FMT "x-machine-kernel:pid=%1$" PID_PRI ";x-machine-unix:pid=%1$" PID_PRI
-#else
-#  define ADDRESS_FMT "x-machine-unix:pid=%1$" PID_PRI
-#endif
         if (asprintf(&address, ADDRESS_FMT, m->leader) < 0)
                 return log_oom();
 
diff --git a/src/shared/bus-util.c b/src/shared/bus-util.c
index 8fcc289957..11350dad71 100644
--- a/src/shared/bus-util.c
+++ b/src/shared/bus-util.c
@@ -545,7 +545,6 @@ int bus_open_system_systemd(sd_bus **_bus) {
          * directly to the system instance, instead of going via the
          * bus */
 
-#ifdef ENABLE_KDBUS
         r = sd_bus_new(&bus);
         if (r < 0)
                 return r;
@@ -564,7 +563,6 @@ int bus_open_system_systemd(sd_bus **_bus) {
         }
 
         bus = sd_bus_unref(bus);
-#endif
 
         r = sd_bus_new(&bus);
         if (r < 0)
@@ -598,7 +596,6 @@ int bus_open_user_systemd(sd_bus **_bus) {
 
         assert(_bus);
 
-#ifdef ENABLE_KDBUS
         r = sd_bus_new(&bus);
         if (r < 0)
                 return r;
@@ -616,7 +613,6 @@ int bus_open_user_systemd(sd_bus **_bus) {
         }
 
         bus = sd_bus_unref(bus);
-#endif
 
         e = secure_getenv("XDG_RUNTIME_DIR");
         if (!e)
@@ -2034,15 +2030,22 @@ int bus_path_decode_unique(const char *path, const char *prefix, char **ret_send
 
 bool is_kdbus_wanted(void) {
         _cleanup_free_ char *value = NULL;
+#ifdef ENABLE_KDBUS
+        const bool configured = true;
+#else
+        const bool configured = false;
+#endif
+
         int r;
 
-        if (get_proc_cmdline_key("kdbus", NULL) <= 0) {
-                r = get_proc_cmdline_key("kdbus=", &value);
-                if (r <= 0 || parse_boolean(value) != 1)
-                        return false;
-        }
+        if (get_proc_cmdline_key("kdbus", NULL) > 0)
+                return true;
+
+        r = get_proc_cmdline_key("kdbus=", &value);
+        if (r <= 0)
+                return configured;
 
-        return true;
+        return parse_boolean(value) == 1;
 }
 
 bool is_kdbus_available(void) {