1 files changed, 148 insertions, 0 deletions
diff --git a/libbacktrace/UnwindMap.cpp b/libbacktrace/UnwindMap.cpp
new file mode 100644
index 000000000..798c769c8
--- /dev/null
+++ b/libbacktrace/UnwindMap.cpp
@@ -0,0 +1,148 @@
+/*
+ * 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.
+ */
+
+#include <pthread.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include <backtrace/BacktraceMap.h>
+
+#include <libunwind.h>
+
+#include "BacktraceLog.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.
+//-------------------------------------------------------------------------
+UnwindMap::UnwindMap(pid_t pid) : BacktraceMap(pid) {
+  unw_map_cursor_clear(&map_cursor_);
+}
+
+UnwindMapRemote::UnwindMapRemote(pid_t pid) : UnwindMap(pid) {
+}
+
+UnwindMapRemote::~UnwindMapRemote() {
+  unw_map_cursor_destroy(&map_cursor_);
+  unw_map_cursor_clear(&map_cursor_);
+}
+
+bool UnwindMapRemote::GenerateMap() {
+  // 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_next(&map_cursor_, &unw_map)) {
+    backtrace_map_t map;
+
+    map.start = unw_map.start;
+    map.end = unw_map.end;
+    map.offset = unw_map.offset;
+    map.load_bias = unw_map.load_base;
+    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;
+}
+
+bool UnwindMapRemote::Build() {
+  return (unw_map_cursor_create(&map_cursor_, pid_) == 0) && GenerateMap();
+}
+
+UnwindMapLocal::UnwindMapLocal() : UnwindMap(getpid()), map_created_(false) {
+  pthread_rwlock_init(&map_lock_, nullptr);
+}
+
+UnwindMapLocal::~UnwindMapLocal() {
+  if (map_created_) {
+    unw_map_local_destroy();
+    unw_map_cursor_clear(&map_cursor_);
+  }
+}
+
+bool UnwindMapLocal::GenerateMap() {
+  // Lock so that multiple threads cannot modify the maps data at the
+  // same time.
+  pthread_rwlock_wrlock(&map_lock_);
+
+  // It's possible for the map to be regenerated while this loop is occurring.
+  // If that happens, get the map again, but only try at most three times
+  // before giving up.
+  bool generated = false;
+  for (int i = 0; i < 3; i++) {
+    maps_.clear();
+
+    // Save the map data retrieved so we can tell if it changes.
+    unw_map_local_cursor_get(&map_cursor_);
+
+    unw_map_t unw_map;
+    int ret;
+    while ((ret = unw_map_local_cursor_get_next(&map_cursor_, &unw_map)) > 0) {
+      backtrace_map_t map;
+
+      map.start = unw_map.start;
+      map.end = unw_map.end;
+      map.offset = unw_map.offset;
+      map.load_bias = unw_map.load_base;
+      map.flags = unw_map.flags;
+      map.name = unw_map.path;
+
+      free(unw_map.path);
+
+      // The maps are in descending order, but we want them in ascending order.
+      maps_.push_front(map);
+    }
+    // Check to see if the map changed while getting the data.
+    if (ret != -UNW_EINVAL) {
+      generated = true;
+      break;
+    }
+  }
+
+  pthread_rwlock_unlock(&map_lock_);
+
+  if (!generated) {
+    BACK_LOGW("Unable to generate the map.");
+  }
+  return generated;
+}
+
+bool UnwindMapLocal::Build() {
+  return (map_created_ = (unw_map_local_create() == 0)) && GenerateMap();;
+}
+
+void UnwindMapLocal::FillIn(uint64_t addr, backtrace_map_t* map) {
+  BacktraceMap::FillIn(addr, map);
+  if (!IsValid(*map)) {
+    // Check to see if the underlying map changed and regenerate the map
+    // if it did.
+    if (unw_map_local_cursor_valid(&map_cursor_) < 0) {
+      if (GenerateMap()) {
+        BacktraceMap::FillIn(addr, map);
+      }
+    }
+  }
+}