Elf interface for new unwinder.

This cl includes the code to read arm unwind information from a shared
library.

Bug: 23762183

Test: Passes all unit tests. I can dump the arm unwind information
Test: for an arm shared library.
Change-Id: I43501ea2eab843b81de8bd5128401dd1971af8d3
diff --git a/libunwindstack/Elf.h b/libunwindstack/Elf.h
new file mode 100644
index 0000000..7bf45b8
--- /dev/null
+++ b/libunwindstack/Elf.h
@@ -0,0 +1,78 @@
+/*
+ * 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.
+ */
+
+#ifndef _LIBUNWINDSTACK_ELF_H
+#define _LIBUNWINDSTACK_ELF_H
+
+#include <stddef.h>
+
+#include <memory>
+#include <string>
+
+#include "ElfInterface.h"
+#include "Memory.h"
+
+#if !defined(EM_AARCH64)
+#define EM_AARCH64 183
+#endif
+
+// Forward declaration.
+class Regs;
+
+class Elf {
+ public:
+  Elf(Memory* memory) : memory_(memory) {}
+  virtual ~Elf() = default;
+
+  bool Init();
+
+  void InitGnuDebugdata();
+
+  bool GetSoname(std::string* name) {
+    return valid_ && interface_->GetSoname(name);
+  }
+
+  bool GetFunctionName(uint64_t, std::string*, uint64_t*) {
+    return false;
+  }
+
+  bool Step(uint64_t rel_pc, Regs* regs, Memory* process_memory) {
+    return valid_ && interface_->Step(rel_pc, regs, process_memory);
+  }
+
+  ElfInterface* CreateInterfaceFromMemory(Memory* memory);
+
+  bool valid() { return valid_; }
+
+  uint32_t machine_type() { return machine_type_; }
+
+  uint8_t class_type() { return class_type_; }
+
+  Memory* memory() { return memory_.get(); }
+
+  ElfInterface* interface() { return interface_.get(); }
+
+  static bool IsValidElf(Memory* memory);
+
+ protected:
+  bool valid_ = false;
+  std::unique_ptr<ElfInterface> interface_;
+  std::unique_ptr<Memory> memory_;
+  uint32_t machine_type_;
+  uint8_t class_type_;
+};
+
+#endif  // _LIBUNWINDSTACK_ELF_H