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

4 files changed, 128 insertions, 16 deletions

diff --git a/cpukit/include/rtems/rtl/rtl-obj-fwd.h b/cpukit/include/rtems/rtl/rtl-obj-fwd.h
index 39e28c58e1..6d41483aa2 100644
--- a/cpukit/include/rtems/rtl/rtl-obj-fwd.h
+++ b/cpukit/include/rtems/rtl/rtl-obj-fwd.h
@@ -27,6 +27,12 @@ struct rtems_rtl_obj_sect;
 typedef struct rtems_rtl_obj_sect rtems_rtl_obj_sect;
 
 /**
+ * The forward declaration of the obj depends structure.
+ */
+struct rtems_rtl_obj_depends;
+typedef struct rtems_rtl_obj_depends rtems_rtl_obj_depends;
+
+/**
  * The forward declaration of the obj structure.
  */
 struct rtems_rtl_obj;
diff --git a/cpukit/include/rtems/rtl/rtl-obj.h b/cpukit/include/rtems/rtl/rtl-obj.h
index be77a81c9d..976d6c293f 100644
--- a/cpukit/include/rtems/rtl/rtl-obj.h
+++ b/cpukit/include/rtems/rtl/rtl-obj.h
@@ -139,12 +139,35 @@ struct rtems_rtl_obj_sect
 };
 
 /**
+ * Object file dependents. This is a list of tables of pointers to the object
+ * modules the object file depends on. The table is a list of tables because
+ * unresolved externals can exist when an object file is loaded and resolved
+ * later when the dependent object file is loaded.
+ */
+struct rtems_rtl_obj_depends
+{
+  rtems_chain_node node;        /**< The node's link in the chain. */
+  size_t           dependents;  /**< The number of dependent object pointers. */
+  rtems_rtl_obj*   depends[];   /**< Dependtent objects. More follow. */
+};
+
+/**
+ * Dependency iterator.
+ */
+typedef bool (*rtems_rtl_obj_depends_iterator) (rtems_rtl_obj* obj,
+                                                rtems_rtl_obj* dependent,
+                                                void*          data);
+
+/**
  * Object file descriptor flags.
  */
-#define RTEMS_RTL_OBJ_LOCKED     (1 << 0) /**< Lock the object file so it cannot
-                                           *   be unloaded. */
-#define RTEMS_RTL_OBJ_UNRESOLVED (1 << 1) /**< The object file has unresolved
-                                           *   external symbols. */
+#define RTEMS_RTL_OBJ_LOCKED       (1 << 0) /**< Lock the object file so it cannot
+                                             *   be unloaded. */
+#define RTEMS_RTL_OBJ_UNRESOLVED   (1 << 1) /**< The object file has unresolved
+                                             *   external symbols. */
+#define RTEMS_RTL_OBJ_BASE         (1 << 2) /**< The base image. */
+#define RTEMS_RTL_OBJ_RELOC_TAG    (1 << 3) /**< Tag the object as visited when reloc
+                                             *   parsing. */
 
 /**
  * RTL Object. There is one for each object module loaded plus one for the base
@@ -154,7 +177,8 @@ struct rtems_rtl_obj
 {
   rtems_chain_node    link;         /**< The node's link in the chain. */
   uint32_t            flags;        /**< The status of the object file. */
-  uint32_t            users;        /**< References to the object file. */
+  size_t              users;        /**< Users of this object file, number of loads. */
+  size_t              refs;         /**< References to the object file. */
   int                 format;       /**< The format of the object file. */
   const char*         fname;        /**< The file name for the object. */
   const char*         oname;        /**< The object file name. Can be
@@ -164,27 +188,28 @@ struct rtems_rtl_obj
                                      *   in a lib */
   off_t               ooffset;      /**< The object offset in the archive. */
   size_t              fsize;        /**< Size of the object file. */
-  rtems_chain_control sections;     /**< The sections of interest in the
-                                     *   object file. */
+  rtems_chain_control sections;     /**< The sections of interest in the object
+                                     *   file. */
+  rtems_chain_control dependents;   /**< The dependent object files. */
   rtems_rtl_obj_sym*  local_table;  /**< Local symbol table. */
   size_t              local_syms;   /**< Local symbol count. */
   size_t              local_size;   /**< Local symbol memory usage. */
   rtems_rtl_obj_sym*  global_table; /**< Global symbol table. */
   size_t              global_syms;  /**< Global symbol count. */
   size_t              global_size;  /**< Global symbol memory usage. */
-  uint32_t            unresolved;   /**< The number of unresolved relocations. */
+  size_t              unresolved;   /**< The number of unresolved relocations. */
   void*               text_base;    /**< The base address of the text section
                                      *   in memory. */
   size_t              text_size;    /**< The size of the text section. */
   void*               const_base;   /**< The base address of the const section
                                      *   in memory. */
-  void*               eh_base;      /**< The base address of the eh section
-                                     *   in memory. */
+  void*               eh_base;      /**< The base address of the eh section in
+                                     *   memory. */
   size_t              eh_size;      /**< The size of the eh section. */
   void*               data_base;    /**< The base address of the data section
                                      *   in memory. */
-  void*               bss_base;     /**< The base address of the bss section
-                                     *   in memory. */
+  void*               bss_base;     /**< The base address of the bss section in
+                                     *   memory. */
   size_t              bss_size;     /**< The size of the bss section. */
   size_t              exec_size;    /**< The amount of executable memory
                                      *   allocated */
@@ -192,9 +217,11 @@ struct rtems_rtl_obj
   uint32_t            checksum;     /**< The checksum of the text sections. A
                                      *   zero means do not checksum. */
   uint32_t*           sec_num;      /**< The sec nums of each obj. */
-  uint32_t            obj_num;      /**< The count of elf files in an rtl obj. */
+  uint32_t            obj_num;      /**< The count of elf files in an rtl
+                                     *   obj. */
   struct link_map*    linkmap;      /**< For GDB. */
-  void*               loader;       /**< The file details specific to a loader. */
+  void*               loader;       /**< The file details specific to a
+                                     *   loader. */
 };
 
 /**
@@ -443,6 +470,46 @@ rtems_rtl_obj_sect* rtems_rtl_obj_find_section_by_mask (const rtems_rtl_obj* obj
                                                         uint32_t             mask);
 
 /**
+ * Allocate a table for dependent objects.
+ *
+ * @param obj The object file's descriptor.
+ * @param dependents The size of the table.
+ * @retval true The table was allocated.
+ * @retval false The alloction failed.
+ */
+bool rtems_rtl_obj_alloc_dependents (rtems_rtl_obj* obj, size_t dependents);
+
+/**
+ * Erase the object file descriptor's dependents.
+ *
+ * @param obj The object file's descriptor.
+ */
+void rtems_rtl_obj_erase_dependents (rtems_rtl_obj* obj);
+
+/**
+ * Add an object file to the dependents table.
+ *
+ * @param obj The object file's descriptor.
+ * @param dependent The dependent object file to add.
+ * @retval true The dependent has been added to the table.
+ * @retval false There is no space in the table.
+ */
+bool rtems_rtl_obj_add_dependent (rtems_rtl_obj* obj, rtems_rtl_obj* dependent);
+
+/**
+ * Iterate over the module dependenices.
+ *
+ * @param obj The object file's descriptor.
+ * @param handler The iterator handler. Returns true to end.
+ * @param data User data passed to the iterator.
+ * @retval true The iterator handler returned true.
+ * @retval false The iterator handler returned false.
+ */
+bool rtems_rtl_obj_iterate_dependents (rtems_rtl_obj*                 obj,
+                                       rtems_rtl_obj_depends_iterator iterator,
+                                       void*                          data);
+
+/**
  * The text section size. Only use once all the sections has been added. It
  * includes alignments between sections that are part of the object's text
  * area. The consts sections are included in this section.
@@ -643,6 +710,20 @@ void rtems_rtl_obj_run_ctors (rtems_rtl_obj* obj);
 void rtems_rtl_obj_run_dtors (rtems_rtl_obj* obj);
 
 /**
+ * Increment the object file reference count.
+ *
+ * @param obj The object file's descriptor.
+ */
+void rtems_rtl_obj_inc_reference (rtems_rtl_obj* obj);
+
+/**
+ * Decrement the object file reference count.
+ *
+ * @param obj The object file's descriptor.
+ */
+void rtems_rtl_obj_dec_reference (rtems_rtl_obj* obj);
+
+/**
  * Load the object file, reading all sections into memory, symbols and
  * performing any relocation fixups.
  *
diff --git a/cpukit/include/rtems/rtl/rtl-sym.h b/cpukit/include/rtems/rtl/rtl-sym.h
index be246a908d..aff9339ea1 100644
--- a/cpukit/include/rtems/rtl/rtl-sym.h
+++ b/cpukit/include/rtems/rtl/rtl-sym.h
@@ -92,7 +92,7 @@ bool rtems_rtl_symbol_global_add (rtems_rtl_obj*       obj,
  *
  * @param name The name as an ASCIIZ string.
  * @retval NULL No symbol found.
- * @return rtems_rtl_obj_sym_t* Reference to the symbol.
+ * @return rtems_rtl_obj_sym* Reference to the symbol.
  */
 rtems_rtl_obj_sym* rtems_rtl_symbol_global_find (const char* name);
 
@@ -102,7 +102,7 @@ rtems_rtl_obj_sym* rtems_rtl_symbol_global_find (const char* name);
  * @param obj The object file to search.
  * @param name The name as an ASCIIZ string.
  * @retval NULL No symbol found.
- * @return rtems_rtl_obj_sym_t* Reference to the symbol.
+ * @return rtems_rtl_obj_sym* Reference to the symbol.
  */
 rtems_rtl_obj_sym* rtems_rtl_symbol_obj_find (rtems_rtl_obj* obj,
                                               const char*    name);
diff --git a/cpukit/include/rtems/rtl/rtl.h b/cpukit/include/rtems/rtl/rtl.h
index e30dba90ef..398ac2cd3f 100644
--- a/cpukit/include/rtems/rtl/rtl.h
+++ b/cpukit/include/rtems/rtl/rtl.h
@@ -28,6 +28,7 @@
 #include <rtems/rtl/rtl-obj.h>
 #include <rtems/rtl/rtl-obj-cache.h>
 #include <rtems/rtl/rtl-obj-comp.h>
+#include <rtems/rtl/rtl-sym.h>
 #include <rtems/rtl/rtl-unresolved.h>
 
 #ifdef __cplusplus
@@ -71,6 +72,11 @@ extern "C" {
 #define RTEMS_RTL_UNRESOLVED_BLOCK_SIZE (64)
 
 /**
+ * The number of dependency record per block in the dependency table.
+ */
+#define RTEMS_RTL_DEPENDENCY_BLOCK_SIZE (16)
+
+/**
  * The global debugger interface variable.
  */
 extern struct r_debug _rtld_debug;
@@ -173,6 +179,16 @@ void rtems_rtl_obj_decompress (rtems_rtl_obj_comp** decomp,
                                off_t                offset);
 
 /**
+ * Update the mask in the object files. You can clear flags and then set
+ * flags. A zero (0) does not clear or set the flags. This is global to all
+ * object files that are laoded.
+ *
+ * @param clear The flag's clear mask, a 0 does not clear any flags.
+ * @param set The flag's set mask, a 0 does not set any flags.
+ */
+void rtems_rtl_obj_update_flags (uint32_t clear, uint32_t set);
+
+/**
  * Lock the Run-time Linker.
  *
  * @return rtems_rtl_data* The RTL data after being locked.
@@ -207,6 +223,15 @@ rtems_rtl_obj* rtems_rtl_check_handle (void* handle);
 rtems_rtl_obj* rtems_rtl_find_obj (const char* name);
 
 /**
+ * Find the object file a symbol is exported from.
+ *
+ * @param sym The symbol to search with.
+ * @retval NULL No object file found.
+ * @return rtems_rtl_obj* Reference to the symbol.
+ */
+rtems_rtl_obj* rtems_rtl_find_obj_with_symbol (const rtems_rtl_obj_sym* sym);
+
+/**
  * Load an object file into memory relocating it. It will not be resolved
  * against other symbols in other object files or the base image.
  *