[wasm] Initial signal handler

src/trap-handler/trap-handler-internal.h

Index: src/trap-handler/trap-handler-internal.h
diff --git a/src/trap-handler/trap-handler-internal.h b/src/trap-handler/trap-handler-internal.h
new file mode 100644
index 0000000000000000000000000000000000000000..702c741eb8ebcbdeaacdcd893a99d180ac2cf052
--- /dev/null
+++ b/src/trap-handler/trap-handler-internal.h
@@ -0,0 +1,64 @@
+// Copyright 2016 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef TRAP_HANDLER_INTERNAL_H_
+#define TRAP_HANDLER_INTERNAL_H_
+
+// This file should not be included (even transitively) by files outside of
+// src/trap-handler.
+
+#include "src/trap-handler/trap-handler.h"
+
+#include <atomic>
+
+#if V8_OS_WIN
+#define THREAD_LOCAL __declspec(thread)
+#elif V8_OS_ANDROID
+// TODO(eholk): fix this before enabling for trap handlers for Android.
+#define THREAD_LOCAL
+#else
+#define THREAD_LOCAL __thread
+#endif
+
+namespace v8 {
+namespace internal {
+namespace trap_handler {
+
+// This describes a chunk of code that the signal handler will be able to
+// handler faults in. base points to the beginning of the chunk, and size is the
+// number of bytes in the code chunk. The remainder of the struct is a list of
+// protected memory access instructions and an offset to a landing pad to handle
+// faults on that instruction.
+struct CodeProtectionInfo {
+  void* base;
+  size_t size;
+  size_t num_protected_instructions;
+  ProtectedInstructionData instructions[1];
+};
+
+class MetadataLock {
+  static std::atomic_flag spinlock_;
+
+ public:
+  MetadataLock();
+  ~MetadataLock();
+
+  MetadataLock(const MetadataLock&) = delete;
+  void operator=(const MetadataLock&) = delete;
+};
+
+#if V8_TRAP_HANDLER_SUPPORTED
+void HandleSignal(int signum, siginfo_t* info, void* context);
+#endif
+
+extern THREAD_LOCAL bool g_thread_in_wasm_code;
+
+extern size_t gNumCodeObjects;
+extern CodeProtectionInfo** gCodeObjects;
+
+}  // namespace trap_handler
+}  // namespace internal
+}  // namespace v8
+
+#endif  // TRAP_HANDLER_INTERNAL_H_