diff -r 000000000000 -r 6474c204b198 js/src/jit/AsmJSSignalHandlers.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit/AsmJSSignalHandlers.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,55 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ * vim: set ts=8 sts=4 et sw=4 tw=99:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef jit_AsmJSSignalHandlers_h
+#define jit_AsmJSSignalHandlers_h
+
+struct JSRuntime;
+
+#ifdef XP_MACOSX
+# include <mach/mach.h>
+# include "jslock.h"
+#endif
+
+namespace js {
+
+// Returns whether signal handlers for asm.js and for JitRuntime access
+// violations have been installed.
+bool
+EnsureAsmJSSignalHandlersInstalled(JSRuntime *rt);
+
+// Force any currently-executing asm.js code to call
+// js::HandleExecutionInterrupt.
+extern void
+RequestInterruptForAsmJSCode(JSRuntime *rt);
+
+// On OSX we are forced to use the lower-level Mach exception mechanism instead
+// of Unix signals. Mach exceptions are not handled on the victim's stack but
+// rather require an extra thread. For simplicity, we create one such thread
+// per JSRuntime (upon the first use of asm.js in the JSRuntime). This thread
+// and related resources are owned by AsmJSMachExceptionHandler which is owned
+// by JSRuntime.
+#ifdef XP_MACOSX
+class AsmJSMachExceptionHandler
+{
+    bool installed_;
+    PRThread *thread_;
+    mach_port_t port_;
+
+    void uninstall();
+
+  public:
+    AsmJSMachExceptionHandler();
+    ~AsmJSMachExceptionHandler() { uninstall(); }
+    mach_port_t port() const { return port_; }
+    bool installed() const { return installed_; }
+    bool install(JSRuntime *rt);
+};
+#endif
+
+} // namespace js
+
+#endif // jit_AsmJSSignalHandlers_h