[srv.init] Serve a service locator protocol from init

The init process now serves as a service locator for its children,
passing all children a mailbox handle on which it is serving the service
locator protocol.

src/user/srv.init/main.cpp

@@ -10,6 +10,7 @@
 
 #include "loader.h"
 #include "modules.h"
+#include "service_locator.h"
 
 using bootproto::module;
 using bootproto::module_type;
@@ -28,6 +29,9 @@ main(int argc, const char **argv)
 {
     j6_status_t s;
 
+    j6_handle_t slp_mb = j6_handle_invalid;
+    j6_handle_t slp_mb_child = j6_handle_invalid;
+
     j6_handle_t sys = j6_handle_invalid;
     j6_handle_t sys_child = j6_handle_invalid;
 
@@ -45,6 +49,13 @@ main(int argc, const char **argv)
     if (s != j6_status_ok)
         return s;
 
+    s = j6_mailbox_create(&slp_mb);
+    if (s != j6_status_ok)
+        return s;
+
+    s = j6_handle_clone(slp_mb, &slp_mb_child,
+            j6_cap_mailbox_send |
+            j6_cap_object_clone);
     if (s != j6_status_ok)
         return s;
 
@@ -57,11 +68,12 @@ main(int argc, const char **argv)
         sprintf(message, "  loading program module '%s' at %lx", prog.filename, prog.base_address);
         j6_log(message);
 
-        if (!load_program(prog, sys_child, message)) {
+        if (!load_program(prog, sys_child, slp_mb_child, message)) {
             j6_log(message);
-            return 1;
+            return 2;
         }
     }
 
+    service_locator_start(slp_mb);
     return 0;
 }