Add support for the new unwind method.

Also add a comment to the GetElf function to indicate that it never returns
nullptr.

Also needed to add this library to the a million and one places that the vndk
has hard-coded this data.

Bug: 23762183

Test: Built, nothing uses the new code.
Test: However, I did run backtrace_test using this code, and all tests pass.
Change-Id: Ib270665dcb7a7607075e36d88be76dbde6e2faa8
(cherry picked from commit dc4104b720c7fd2014ccfa9fa621d02df58a43c4)

1 files changed, 94 insertions, 0 deletions

diff --git a/libbacktrace/UnwindStackMap.cpp b/libbacktrace/UnwindStackMap.cpp
new file mode 100644
index 000000000..ba9fd87d7
--- /dev/null
+++ b/libbacktrace/UnwindStackMap.cpp
@@ -0,0 +1,94 @@
+/*
+ * Copyright (C) 2017 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 <stdint.h>
+#include <stdlib.h>
+#include <sys/types.h>
+
+#include <backtrace/BacktraceMap.h>
+#include <unwindstack/Elf.h>
+#include <unwindstack/MapInfo.h>
+#include <unwindstack/Maps.h>
+
+#include "UnwindStackMap.h"
+
+//-------------------------------------------------------------------------
+UnwindStackMap::UnwindStackMap(pid_t pid) : BacktraceMap(pid) {}
+
+bool UnwindStackMap::Build() {
+  if (pid_ == 0) {
+    pid_ = getpid();
+    stack_maps_.reset(new unwindstack::LocalMaps);
+  } else {
+    stack_maps_.reset(new unwindstack::RemoteMaps(pid_));
+  }
+
+  if (!stack_maps_->Parse()) {
+    return false;
+  }
+
+  // Iterate through the maps and fill in the backtrace_map_t structure.
+  for (auto& map_info : *stack_maps_) {
+    backtrace_map_t map;
+    map.start = map_info.start;
+    map.end = map_info.end;
+    map.offset = map_info.offset;
+    // Set to -1 so that it is demand loaded.
+    map.load_bias = static_cast<uintptr_t>(-1);
+    map.flags = map_info.flags;
+    map.name = map_info.name;
+
+    maps_.push_back(map);
+  }
+
+  return true;
+}
+
+void UnwindStackMap::FillIn(uintptr_t addr, backtrace_map_t* map) {
+  BacktraceMap::FillIn(addr, map);
+  if (map->load_bias != static_cast<uintptr_t>(-1)) {
+    return;
+  }
+
+  // Fill in the load_bias.
+  unwindstack::MapInfo* map_info = stack_maps_->Find(addr);
+  if (map_info == nullptr) {
+    return;
+  }
+  unwindstack::Elf* elf = map_info->GetElf(pid_, true);
+  map->load_bias = elf->GetLoadBias();
+}
+
+//-------------------------------------------------------------------------
+// BacktraceMap create function.
+//-------------------------------------------------------------------------
+BacktraceMap* BacktraceMap::CreateNew(pid_t pid, bool uncached) {
+  BacktraceMap* map;
+
+  if (uncached) {
+    // Force use of the base class to parse the maps when this call is made.
+    map = new BacktraceMap(pid);
+  } else if (pid == getpid()) {
+    map = new UnwindStackMap(0);
+  } else {
+    map = new UnwindStackMap(pid);
+  }
+  if (!map->Build()) {
+    delete map;
+    return nullptr;
+  }
+  return map;
+}