Print kdbus path when opening fails

This makes it easier to debug what is going on.

3 files changed, 20 insertions, 6 deletions

diff --git a/src/core/busname.c b/src/core/busname.c
index b3f7e0d5d5..39ea6a0d93 100644
--- a/src/core/busname.c
+++ b/src/core/busname.c
@@ -290,14 +290,19 @@ static int busname_watch_fd(BusName *n) {
 }
 
 static int busname_open_fd(BusName *n) {
+        _cleanup_free_ char *path = NULL;
+        const char *mode;
+
         assert(n);
 
         if (n->starter_fd >= 0)
                 return 0;
 
-        n->starter_fd = bus_kernel_open_bus_fd(UNIT(n)->manager->running_as == SYSTEMD_SYSTEM ? "system" : "user");
+        mode = UNIT(n)->manager->running_as == SYSTEMD_SYSTEM ? "system" : "user";
+        n->starter_fd = bus_kernel_open_bus_fd(mode, &path);
         if (n->starter_fd < 0) {
-                log_warning_unit(UNIT(n)->id, "Failed to create starter fd: %s", strerror(-n->starter_fd));
+                log_warning_unit(UNIT(n)->id, "Failed to open %s: %s",
+                                 path ?: "kdbus", strerror(-n->starter_fd));
                 return n->starter_fd;
         }
 
diff --git a/src/libsystemd/sd-bus/bus-kernel.c b/src/libsystemd/sd-bus/bus-kernel.c
index f49fb5b394..8b961c38eb 100644
--- a/src/libsystemd/sd-bus/bus-kernel.c
+++ b/src/libsystemd/sd-bus/bus-kernel.c
@@ -1402,11 +1402,20 @@ static int bus_kernel_translate_policy(const BusNamePolicy *policy, struct kdbus
         return 0;
 }
 
-int bus_kernel_open_bus_fd(const char *bus) {
+int bus_kernel_open_bus_fd(const char *bus, char **path) {
         char *p;
         int fd;
+        size_t len;
 
-        p = alloca(strlen("/dev/kdbus/") + DECIMAL_STR_MAX(uid_t) + 1 + strlen(bus) + strlen("/bus") + 1);
+        len = strlen("/dev/kdbus/") + DECIMAL_STR_MAX(uid_t) + 1 + strlen(bus) + strlen("/bus") + 1;
+
+        if (path) {
+                p = malloc(len);
+                if (!p)
+                        return -ENOMEM;
+                *path = p;
+        } else
+                p = alloca(len);
         sprintf(p, "/dev/kdbus/" UID_FMT "-%s/bus", getuid(), bus);
 
         fd = open(p, O_RDWR|O_NOCTTY|O_CLOEXEC);
@@ -1549,7 +1558,7 @@ int bus_kernel_create_monitor(const char *bus) {
 
         assert(bus);
 
-        fd = bus_kernel_open_bus_fd(bus);
+        fd = bus_kernel_open_bus_fd(bus, NULL);
         if (fd < 0)
                 return fd;
 
diff --git a/src/libsystemd/sd-bus/bus-kernel.h b/src/libsystemd/sd-bus/bus-kernel.h
index 2fe2495a6c..87f98c58bf 100644
--- a/src/libsystemd/sd-bus/bus-kernel.h
+++ b/src/libsystemd/sd-bus/bus-kernel.h
@@ -65,7 +65,7 @@ int bus_kernel_take_fd(sd_bus *b);
 int bus_kernel_write_message(sd_bus *bus, sd_bus_message *m, bool hint_sync_call);
 int bus_kernel_read_message(sd_bus *bus, bool hint_priority, int64_t priority);
 
-int bus_kernel_open_bus_fd(const char *bus);
+int bus_kernel_open_bus_fd(const char *bus, char **path);
 int bus_kernel_make_starter(int fd, const char *name, bool activating, bool accept_fd, BusNamePolicy *policy, BusNamePolicyAccess world_policy);
 
 int bus_kernel_create_bus(const char *name, bool world, char **s);