--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/os/bsd/gc/z/zBackingFile_bsd.hpp	Tue Nov 12 09:27:21 2019 +0000
@@ -0,0 +1,59 @@
+/*
+ * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+#ifndef OS_BSD_GC_Z_ZBACKINGFILE_BSD_HPP
+#define OS_BSD_GC_Z_ZBACKINGFILE_BSD_HPP
+
+#include "memory/allocation.hpp"
+
+class ZPhysicalMemory;
+
+// On macOS, we use a virtual backing file. It is represented by a reserved virtual
+// address space, in which we commit physical memory using the mach_vm_map() API.
+// The multi-mapping API simply remaps these addresses using mach_vm_remap() into
+// the different heap views. This works as-if there was a backing file, it's just
+// that the file is represented with memory mappings instead.
+
+class ZBackingFile {
+private:
+  uintptr_t _base;
+  size_t    _size;
+  bool      _initialized;
+
+  bool commit_inner(size_t offset, size_t length);
+
+public:
+  ZBackingFile();
+
+  bool is_initialized() const;
+
+  size_t size() const;
+
+  size_t commit(size_t offset, size_t length);
+  size_t uncommit(size_t offset, size_t length);
+
+  void map(uintptr_t addr, size_t size, uintptr_t offset) const;
+  void unmap(uintptr_t addr, size_t size) const;
+};
+
+#endif // OS_BSD_GC_Z_ZBACKINGFILE_BSD_HPP