Add plugin API for processing plugin-added input files

Gold plugins may wish to further process an input file added by a plugin. For
example, the plugin may need to assign a unique segment for sections in a
plugin-generated input file. This patch adds a plugin callback that the linker
will call when reading symbols from a new input file added after the
all_symbols_read event (i.e. an input file added by a plugin).

2017-12-11  Stephen Crane  <sjc@immunant.com>

	* plugin-api.h: Add new plugin hook to allow processing of input
	files added by a plugin.
	(ld_plugin_new_input_handler): New function hook type.
	(ld_plugin_register_new_input): New interface.
	(LDPT_REGISTER_NEW_INPUT_HOOK): New enum val.
	(tv_register_new_input): New member.

	* plugin.cc (Plugin::load): Include hooks for register_new_input
	in transfer vector.
	(Plugin::new_input): New function.
	(register_new_input): New function.
	(Plugin_manager::claim_file): Call Plugin::new_input if in
	replacement phase.
	* plugin.h (Plugin::set_new_input_handler): New function.
	* testsuite/plugin_new_section_layout.c: New plugin to test
	new_input plugin API.
	* testsuite/plugin_final_layout.sh: Add new input test.
	* testsuite/Makefile.am (plugin_layout_new_file): New test case.
	* testsuite/Makefile.in: Regenerate.

1 files changed, 48 insertions, 15 deletions

diff --git a/gold/plugin.cc b/gold/plugin.cc
index 5ea23b5..49212b4 100644
--- a/gold/plugin.cc
+++ b/gold/plugin.cc
@@ -167,6 +167,9 @@ static enum ld_plugin_status
 get_input_section_size(const struct ld_plugin_section section,
                        uint64_t* secsize);
 
+static enum ld_plugin_status
+register_new_input(ld_plugin_new_input_handler handler);
+
 };
 
 #endif // ENABLE_PLUGINS
@@ -211,7 +214,7 @@ Plugin::load()
   sscanf(ver, "%d.%d", &major, &minor);
 
   // Allocate and populate a transfer vector.
-  const int tv_fixed_size = 29;
+  const int tv_fixed_size = 30;
 
   int tv_size = this->args_.size() + tv_fixed_size;
   ld_plugin_tv* tv = new ld_plugin_tv[tv_size];
@@ -346,6 +349,10 @@ Plugin::load()
   tv[i].tv_u.tv_get_input_section_size = get_input_section_size;
 
   ++i;
+  tv[i].tv_tag = LDPT_REGISTER_NEW_INPUT_HOOK;
+  tv[i].tv_u.tv_register_new_input = register_new_input;
+
+  ++i;
   tv[i].tv_tag = LDPT_NULL;
   tv[i].tv_u.tv_val = 0;
 
@@ -383,6 +390,15 @@ Plugin::all_symbols_read()
     (*this->all_symbols_read_handler_)();
 }
 
+// Call the new_input handler.
+
+inline void
+Plugin::new_input(struct ld_plugin_input_file* plugin_input_file)
+{
+  if (this->new_input_handler_ != NULL)
+    (*this->new_input_handler_)(plugin_input_file);
+}
+
 // Call the cleanup handler.
 
 inline void
@@ -476,8 +492,6 @@ Plugin_manager::claim_file(Input_file* input_file, off_t offset,
 
   gold_assert(lock_initialized);
   Hold_lock hl(*this->lock_);
-  if (this->in_replacement_phase_)
-    return NULL;
 
   unsigned int handle = this->objects_.size();
   this->input_file_ = input_file;
@@ -494,19 +508,28 @@ Plugin_manager::claim_file(Input_file* input_file, off_t offset,
        this->current_ != this->plugins_.end();
        ++this->current_)
     {
-      if ((*this->current_)->claim_file(&this->plugin_input_file_))
+      // If we aren't yet in replacement phase, allow plugins to claim input
+      // files, otherwise notify the plugin of the new input file, if needed.
+      if (!this->in_replacement_phase_)
         {
-	  this->any_claimed_ = true;
-	  this->in_claim_file_handler_ = false;
-
-          if (this->objects_.size() > handle
-              && this->objects_[handle]->pluginobj() != NULL)
-            return this->objects_[handle]->pluginobj();
-
-          // If the plugin claimed the file but did not call the
-          // add_symbols callback, we need to create the Pluginobj now.
-          Pluginobj* obj = this->make_plugin_object(handle);
-          return obj;
+          if ((*this->current_)->claim_file(&this->plugin_input_file_))
+            {
+              this->any_claimed_ = true;
+              this->in_claim_file_handler_ = false;
+
+              if (this->objects_.size() > handle
+                  && this->objects_[handle]->pluginobj() != NULL)
+                return this->objects_[handle]->pluginobj();
+
+              // If the plugin claimed the file but did not call the
+              // add_symbols callback, we need to create the Pluginobj now.
+              Pluginobj* obj = this->make_plugin_object(handle);
+              return obj;
+            }
+        }
+      else
+        {
+          (*this->current_)->new_input(&this->plugin_input_file_);
         }
     }
 
@@ -1905,6 +1928,16 @@ unique_segment_for_sections(const char* segment_name,
   return LDPS_OK;
 }
 
+// Register a new_input handler.
+
+static enum ld_plugin_status
+register_new_input(ld_plugin_new_input_handler handler)
+{
+  gold_assert(parameters->options().has_plugins());
+  parameters->options().plugins()->set_new_input_handler(handler);
+  return LDPS_OK;
+}
+
 #endif // ENABLE_PLUGINS
 
 // Allocate a Pluginobj object of the appropriate size and endianness.