--- old/src/share/vm/utilities/globalDefinitions.cpp	2012-11-12 10:52:11.648617572 -0800
+++ new/src/share/vm/utilities/globalDefinitions.cpp	2012-11-12 10:52:11.564618628 -0800
@@ -355,3 +355,49 @@
 
     return size_t(result);
 }
+
+// Clamp an address to be within a specific page
+// 1. If the address is on the page it is returned as is
+// 2. If the address is above the page_address the start of the *next* page will be returned
+// 3. If the address is below the page_address the start of the page will be returned
+static address clamp_address_in_page(address addr, address page_address, intptr_t page_size) {
+  if (align_size_down(intptr_t(addr), page_size) == align_size_down(intptr_t(page_address), page_size)) {
+    // address is in the specified page, just return it as is
+    return addr;
+  } else if (addr > page_address) {
+    // address is on above specified page, return start of next page
+    return (address)align_size_down(intptr_t(page_address), page_size) + page_size;
+  } else {
+    // address is below specified page, return start of page
+    return (address)align_size_down(intptr_t(page_address), page_size);
+  }
+}
+
+address clamp_address_in_page(address addr, address page_address) {
+  intptr_t page_size = os::vm_page_size();
+  return clamp_address_in_page(addr, page_address, page_size);
+}
+
+#ifndef PRODUCT
+
+void GlobalDefinitions::test_globals() {
+  intptr_t page_size = 4096;
+  address a_page = (address)(10*page_size);
+
+  // Check that address within page is returned as is
+  assert(clamp_address_in_page(a_page, a_page, 4096) == a_page, "incorrect");
+  assert(clamp_address_in_page(a_page + 128, a_page, 4096) == a_page + 128, "incorrect");
+  assert(clamp_address_in_page(a_page + page_size - 1, a_page, 4096) == a_page + page_size - 1, "incorrect");
+
+  // Check that address above page returns start of next page
+  assert(clamp_address_in_page(a_page + page_size, a_page, 4096) == a_page + page_size, "incorrect");
+  assert(clamp_address_in_page(a_page + page_size + 1, a_page, 4096) == a_page + page_size, "incorrect");
+  assert(clamp_address_in_page(a_page + page_size*5 + 1, a_page, 4096) == a_page + page_size, "incorrect");
+
+  // Check that address below page returns start of page
+  assert(clamp_address_in_page(a_page - 1, a_page, 4096) == a_page, "incorrect");
+  assert(clamp_address_in_page(a_page - 2*page_size - 1, a_page, 4096) == a_page, "incorrect");
+  assert(clamp_address_in_page(a_page - 5*page_size - 1, a_page, 4096) == a_page, "incorrect");
+}
+
+#endif // PRODUCT