Re-enable libunwind for arm.

Update to handle the new optimized way that libunwind works.

In addition, a small refactor of the BacktraceMap code.

A few new tests of for good measure.

Change-Id: I2f9b4f5ad5a0dfe907b31febee76e4b9b94fb76f

1 files changed, 110 insertions, 0 deletions

diff --git a/libbacktrace/UnwindMap.cpp b/libbacktrace/UnwindMap.cpp
new file mode 100644
index 0000000..9c8193b
--- /dev/null
+++ b/libbacktrace/UnwindMap.cpp
@@ -0,0 +1,110 @@
+/*
+ * Copyright (C) 2014 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.
+ */
+
+#define LOG_TAG "libbacktrace"
+
+#include <pthread.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include <backtrace/BacktraceMap.h>
+
+#include <libunwind.h>
+
+#include "UnwindMap.h"
+
+//-------------------------------------------------------------------------
+// libunwind has a single shared address space for the current process
+// aka local. If multiple maps are created for the current pid, then
+// only update the local address space once, and keep a reference count
+// of maps using the same map cursor.
+//-------------------------------------------------------------------------
+static pthread_mutex_t g_map_mutex = PTHREAD_MUTEX_INITIALIZER;
+static unw_map_cursor_t* g_map_cursor = NULL;
+static int g_map_references = 0;
+
+UnwindMap::UnwindMap(pid_t pid) : BacktraceMap(pid) {
+  map_cursor_.map_list = NULL;
+}
+
+UnwindMap::~UnwindMap() {
+  if (pid_ == getpid()) {
+    pthread_mutex_lock(&g_map_mutex);
+    if (--g_map_references == 0) {
+      // Clear the local address space map.
+      unw_map_set(unw_local_addr_space, NULL);
+      unw_map_cursor_destroy(&map_cursor_);
+    }
+    pthread_mutex_unlock(&g_map_mutex);
+  } else {
+    unw_map_cursor_destroy(&map_cursor_);
+  }
+}
+
+bool UnwindMap::Build() {
+  bool return_value = true;
+  if (pid_ == getpid()) {
+    pthread_mutex_lock(&g_map_mutex);
+    if (g_map_references == 0) {
+      return_value = (unw_map_cursor_create(&map_cursor_, pid_) == 0);
+      if (return_value) {
+        // Set the local address space to this cursor map.
+        unw_map_set(unw_local_addr_space, &map_cursor_);
+        g_map_references = 1;
+        g_map_cursor = &map_cursor_;
+      }
+    } else {
+      g_map_references++;
+      map_cursor_ = *g_map_cursor;
+    }
+    pthread_mutex_unlock(&g_map_mutex);
+  } else {
+    return_value = (unw_map_cursor_create(&map_cursor_, pid_) == 0);
+  }
+
+  if (!return_value)
+    return false;
+
+  // Use the map_cursor information to construct the BacktraceMap data
+  // rather than reparsing /proc/self/maps.
+  unw_map_cursor_reset(&map_cursor_);
+  unw_map_t unw_map;
+  while (unw_map_cursor_get(&map_cursor_, &unw_map)) {
+    backtrace_map_t map;
+
+    map.start = unw_map.start;
+    map.end = unw_map.end;
+    map.flags = unw_map.flags;
+    map.name = unw_map.path;
+
+    // The maps are in descending order, but we want them in ascending order.
+    maps_.push_front(map);
+  }
+
+  return true;
+}
+
+//-------------------------------------------------------------------------
+// BacktraceMap create function.
+//-------------------------------------------------------------------------
+BacktraceMap* BacktraceMap::Create(pid_t pid) {
+  BacktraceMap* map = new UnwindMap(pid);
+  if (!map->Build()) {
+    delete map;
+    return NULL;
+  }
+  return map;
+}