No special case for pid == 0. As of 2015, with FreeBSD 10.1-RELEASE #0 r274401 on amd64, this really works and sets the name to "kernel" for pid == 0.

sysdeps/freebsd/procstate.c

@@ -54,9 +54,6 @@ glibtop_get_proc_state_p (glibtop *server,
 
 	memset (buf, 0, sizeof (glibtop_proc_state));
 
-	/* It does not work for the swapper task. */
-	if (pid == 0) return;
-
 	/* Get the process information */
 	pinfo = kvm_getprocs (server->machine.kd, KERN_PROC_PID, pid, &count);
 	if ((pinfo == NULL) || (count != 1)) {