1 files changed, 94 insertions, 0 deletions
diff --git a/linker/linker_gdb_support.cpp b/linker/linker_gdb_support.cpp
new file mode 100644
index 000000000..de7408740
--- /dev/null
+++ b/linker/linker_gdb_support.cpp
@@ -0,0 +1,94 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "linker_gdb_support.h"
+
+#include <pthread.h>
+
+#include "private/ScopedPthreadMutexLocker.h"
+
+// This function is an empty stub where GDB locates a breakpoint to get notified
+// about linker activity.
+extern "C"
+void __attribute__((noinline)) __attribute__((visibility("default"))) rtld_db_dlactivity();
+
+r_debug _r_debug =
+    {1, nullptr, reinterpret_cast<uintptr_t>(&rtld_db_dlactivity), r_debug::RT_CONSISTENT, 0};
+
+static pthread_mutex_t g__r_debug_mutex = PTHREAD_MUTEX_INITIALIZER;
+static link_map* r_debug_tail = nullptr;
+
+void insert_link_map_into_debug_map(link_map* map) {
+  // Stick the new library at the end of the list.
+  // gdb tends to care more about libc than it does
+  // about leaf libraries, and ordering it this way
+  // reduces the back-and-forth over the wire.
+  if (r_debug_tail != nullptr) {
+    r_debug_tail->l_next = map;
+    map->l_prev = r_debug_tail;
+    map->l_next = nullptr;
+  } else {
+    _r_debug.r_map = map;
+    map->l_prev = nullptr;
+    map->l_next = nullptr;
+  }
+  r_debug_tail = map;
+}
+
+void remove_link_map_from_debug_map(link_map* map) {
+  if (r_debug_tail == map) {
+    r_debug_tail = map->l_prev;
+  }
+
+  if (map->l_prev) {
+    map->l_prev->l_next = map->l_next;
+  }
+  if (map->l_next) {
+    map->l_next->l_prev = map->l_prev;
+  }
+}
+
+void notify_gdb_of_load(link_map* map) {
+  ScopedPthreadMutexLocker locker(&g__r_debug_mutex);
+
+  _r_debug.r_state = r_debug::RT_ADD;
+  rtld_db_dlactivity();
+
+  insert_link_map_into_debug_map(map);
+
+  _r_debug.r_state = r_debug::RT_CONSISTENT;
+  rtld_db_dlactivity();
+}
+
+void notify_gdb_of_unload(link_map* map) {
+  ScopedPthreadMutexLocker locker(&g__r_debug_mutex);
+
+  _r_debug.r_state = r_debug::RT_DELETE;
+  rtld_db_dlactivity();
+
+  remove_link_map_from_debug_map(map);
+
+  _r_debug.r_state = r_debug::RT_CONSISTENT;
+  rtld_db_dlactivity();
+}
+
+void notify_gdb_of_libraries() {
+  _r_debug.r_state = r_debug::RT_ADD;
+  rtld_db_dlactivity();
+  _r_debug.r_state = r_debug::RT_CONSISTENT;
+  rtld_db_dlactivity();
+}
+