diff --git a/sysdeps/mach/readonly-area.c b/sysdeps/mach/readonly-area.c
new file mode 100644
index 0000000000..afee7a4bde
--- /dev/null
+++ b/sysdeps/mach/readonly-area.c
@@ -0,0 +1,57 @@
+/* Test if a memory region is wholly unwritable.  Mach version.
+   Copyright (C) 2004 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library 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
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, write to the Free
+   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+   02111-1307 USA.  */
+
+#include <stdlib.h>
+#include <stdint.h>
+#include <mach.h>
+
+/* Return 1 if the whole area PTR .. PTR+SIZE is not writable.
+   Return -1 if it is writable.  */
+
+int
+__readonly_area (const char *ptr, size_t size)
+{
+  vm_address_t region_address = (uintptr_t) ptr;
+  vm_size_t region_length = size;
+  vm_prot_t protection;
+  vm_prot_t max_protection;
+  vm_inherit_t inheritance;
+  boolean_t is_shared;
+  mach_port_t object_name;
+  vm_offset_t offset;
+
+  while (__vm_region (__mach_task_self (),
+		      &region_address, &region_length,
+		      &protection, &max_protection, &inheritance, &is_shared,
+		      &object_name, &offset) == KERN_SUCCESS
+	 && region_address <= (uintptr_t) ptr)
+    {
+      region_address += region_length;
+      if (region_address < (uintptr_t) ptr)
+	continue;
+
+      if (protection & VM_PROT_WRITE)
+	return -1;
+
+      if (region_address - (uintptr_t) ptr >= size)
+	break;
+    }
+
+  return 1;
+}