libdl: Add object file dependencies to track references

Tracking references lets us manage when an object file can be
unloaded. If an object file has references to it, it cannot be
unloaded.

Modules that depend on each other cannot be unloaded.

Updates #3605

1 files changed, 47 insertions, 1 deletions

diff --git a/cpukit/libdl/rtl.c b/cpukit/libdl/rtl.c
index 628fc771bc..fdf4c1229f 100644
--- a/cpukit/libdl/rtl.c
+++ b/cpukit/libdl/rtl.c
@@ -216,6 +216,11 @@ rtems_rtl_data_init (void)
        */
       rtl->base->oname = rtems_rtl_strdup ("rtems-kernel");
 
+      /*
+       * Lock the base image and flag it as the base image.
+       */
+      rtl->base->flags |= RTEMS_RTL_OBJ_LOCKED | RTEMS_RTL_OBJ_BASE;
+
       rtems_chain_append (&rtl->objects, &rtl->base->link);
     }
 
@@ -312,6 +317,21 @@ rtems_rtl_obj_decompress (rtems_rtl_obj_comp** decomp,
   }
 }
 
+void
+rtems_rtl_obj_update_flags (uint32_t clear, uint32_t set)
+{
+  rtems_chain_node* node  = rtems_chain_first (&rtl->objects);
+  while (!rtems_chain_is_tail (&rtl->objects, node))
+  {
+    rtems_rtl_obj* obj = (rtems_rtl_obj*) node;
+    if (clear != 0)
+      obj->flags &= ~clear;
+    if (set != 0)
+      obj->flags |= set;
+    node = rtems_chain_next (node);
+  }
+}
+
 rtems_rtl_data*
 rtems_rtl_lock (void)
 {
@@ -386,6 +406,21 @@ rtems_rtl_find_obj (const char* name)
 }
 
 rtems_rtl_obj*
+rtems_rtl_find_obj_with_symbol (const rtems_rtl_obj_sym* sym)
+{
+  rtems_chain_node* node = rtems_chain_first (&rtl->objects);
+  while (!rtems_chain_is_tail (&rtl->objects, node))
+  {
+    rtems_rtl_obj* obj = (rtems_rtl_obj*) node;
+    if (sym >= obj->global_table &&
+        sym < (obj->global_table + obj->global_syms))
+      return obj;
+    node = rtems_chain_next (node);
+  }
+  return NULL;
+}
+
+rtems_rtl_obj*
 rtems_rtl_load_object (const char* name, int mode)
 {
   rtems_rtl_obj* obj;
@@ -489,6 +524,11 @@ rtems_rtl_unload_object (rtems_rtl_obj* obj)
 
   if (obj->users == 0)
   {
+    if (obj->refs != 0)
+    {
+      rtems_rtl_set_error (EBUSY, "object file referenced");
+      return false;
+    }
     obj->flags |= RTEMS_RTL_OBJ_LOCKED;
     rtems_rtl_unlock ();
     rtems_rtl_obj_run_dtors (obj);
@@ -618,5 +658,11 @@ rtems_rtl_base_sym_global_add (const unsigned char* esyms,
 rtems_rtl_obj*
 rtems_rtl_baseimage (void)
 {
-  return NULL;
+  rtems_rtl_obj* base = NULL;
+  if (rtems_rtl_lock ())
+  {
+    base = rtl->base;
+    rtems_rtl_unlock ();
+  }
+  return base;
 }