Fix which maps to search for globals.

If multiple threads are unwinding at the same time, new maps that contain
the global variables for dex files and jit information are created. This
leads to threads creating more new maps that then get searched, then
more maps, then more searching until virtual address space exhaustion.

Fix this so that we only search maps that have a corresponding rw map that
could contain the global memory.

Small refactor to combine the code to search for global variables into
one class that both classes inherit from.

Modify unit tests for the new pattern checking.

Bug: 117761427

Test: Ran unit tests for libunwindstack/libbacktrace/simpleperf.
Test: Ran art 004-ThreadStress that used to fail.
Change-Id: I837ca6b9d0383100079de090bc7d019598e0cdfe

3 files changed, 65 insertions, 8 deletions

diff --git a/libunwindstack/include/unwindstack/DexFiles.h b/libunwindstack/include/unwindstack/DexFiles.h
index 26f5d35..c2fde74 100644
--- a/libunwindstack/include/unwindstack/DexFiles.h
+++ b/libunwindstack/include/unwindstack/DexFiles.h
@@ -25,16 +25,18 @@
 #include <unordered_map>
 #include <vector>
 
+#include <unwindstack/Global.h>
+#include <unwindstack/Memory.h>
+
 namespace unwindstack {
 
 // Forward declarations.
 class DexFile;
 class Maps;
 struct MapInfo;
-class Memory;
 enum ArchEnum : uint8_t;
 
-class DexFiles {
+class DexFiles : public Global {
  public:
   explicit DexFiles(std::shared_ptr<Memory>& memory);
   DexFiles(std::shared_ptr<Memory>& memory, std::vector<std::string>& search_libs);
@@ -60,8 +62,7 @@ class DexFiles {
 
   bool ReadEntry64();
 
-  std::shared_ptr<Memory> memory_;
-  std::vector<std::string> search_libs_;
+  bool ReadVariableData(uint64_t ptr_offset) override;
 
   std::mutex lock_;
   bool initialized_ = false;
diff --git a/libunwindstack/include/unwindstack/Global.h b/libunwindstack/include/unwindstack/Global.h
new file mode 100644
index 0000000..70e3ddd
--- /dev/null
+++ b/libunwindstack/include/unwindstack/Global.h
@@ -0,0 +1,54 @@
+/*
+ * Copyright (C) 2018 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.
+ */
+
+#ifndef _LIBUNWINDSTACK_GLOBAL_H
+#define _LIBUNWINDSTACK_GLOBAL_H
+
+#include <stdint.h>
+
+#include <memory>
+#include <mutex>
+#include <string>
+#include <unordered_map>
+#include <vector>
+
+#include <unwindstack/Memory.h>
+
+namespace unwindstack {
+
+// Forward declarations.
+class Maps;
+struct MapInfo;
+
+class Global {
+ public:
+  explicit Global(std::shared_ptr<Memory>& memory);
+  Global(std::shared_ptr<Memory>& memory, std::vector<std::string>& search_libs);
+  virtual ~Global() = default;
+
+ protected:
+  uint64_t GetVariableOffset(MapInfo* info, const std::string& variable);
+  void FindAndReadVariable(Maps* maps, const char* variable);
+
+  virtual bool ReadVariableData(uint64_t offset) = 0;
+
+  std::shared_ptr<Memory> memory_;
+  std::vector<std::string> search_libs_;
+};
+
+}  // namespace unwindstack
+
+#endif  // _LIBUNWINDSTACK_GLOBAL_H
diff --git a/libunwindstack/include/unwindstack/JitDebug.h b/libunwindstack/include/unwindstack/JitDebug.h
index 0bcd0b0..ccb473f 100644
--- a/libunwindstack/include/unwindstack/JitDebug.h
+++ b/libunwindstack/include/unwindstack/JitDebug.h
@@ -24,15 +24,17 @@
 #include <string>
 #include <vector>
 
+#include <unwindstack/Global.h>
+#include <unwindstack/Memory.h>
+
 namespace unwindstack {
 
 // Forward declarations.
 class Elf;
 class Maps;
-class Memory;
 enum ArchEnum : uint8_t;
 
-class JitDebug {
+class JitDebug : public Global {
  public:
   explicit JitDebug(std::shared_ptr<Memory>& memory);
   JitDebug(std::shared_ptr<Memory>& memory, std::vector<std::string>& search_libs);
@@ -45,11 +47,9 @@ class JitDebug {
  private:
   void Init(Maps* maps);
 
-  std::shared_ptr<Memory> memory_;
   uint64_t entry_addr_ = 0;
   bool initialized_ = false;
   std::vector<Elf*> elf_list_;
-  std::vector<std::string> search_libs_;
 
   std::mutex lock_;
 
@@ -62,6 +62,8 @@ class JitDebug {
   uint64_t ReadEntry32Pack(uint64_t* start, uint64_t* size);
   uint64_t ReadEntry32Pad(uint64_t* start, uint64_t* size);
   uint64_t ReadEntry64(uint64_t* start, uint64_t* size);
+
+  bool ReadVariableData(uint64_t ptr_offset) override;
 };
 
 }  // namespace unwindstack