time-util: deal with systems where userspace has 64bit time_t but kernel does not

Fixes: #14362

src/basic/time-util.c

@@ -1500,8 +1500,29 @@ int time_change_fd(void) {
         if (fd < 0)
                 return -errno;
 
-        if (timerfd_settime(fd, TFD_TIMER_ABSTIME|TFD_TIMER_CANCEL_ON_SET, &its, NULL) < 0)
-                return -errno;
+        if (timerfd_settime(fd, TFD_TIMER_ABSTIME|TFD_TIMER_CANCEL_ON_SET, &its, NULL) >= 0)
+                return TAKE_FD(fd);
 
-        return TAKE_FD(fd);
+        /* So apparently there are systems where time_t is 64bit, but the kernel actually doesn't support
+         * 64bit time_t. In that case configuring a timer to TIME_T_MAX will fail with EOPNOTSUPP or a
+         * similar error. If that's the case let's try with INT32_MAX instead, maybe that works. It's a bit
+         * of a black magic thing though, but what can we do?
+         *
+         * We don't want this code on x86-64, hence let's conditionalize this for systems with 64bit time_t
+         * but where "long" is shorter than 64bit, i.e. 32bit archs.
+         *
+         * See: https://github.com/systemd/systemd/issues/14362 */
+
+#if SIZEOF_TIME_T == 8 && ULONG_MAX < UINT64_MAX
+        if (ERRNO_IS_NOT_SUPPORTED(errno)) {
+                static const struct itimerspec its32 = {
+                        .it_value.tv_sec = INT32_MAX,
+                };
+
+                if (timerfd_settime(fd, TFD_TIMER_ABSTIME|TFD_TIMER_CANCEL_ON_SET, &its32, NULL) >= 0)
+                        return TAKE_FD(fd);
+        }
+#endif
+
+        return -errno;
 }