--- a/src/share/vm/runtime/arguments.cpp	Mon Mar 19 10:09:24 2012 +0100
+++ b/src/share/vm/runtime/arguments.cpp	Tue Mar 20 16:46:39 2012 -0400
@@ -816,8 +816,21 @@
     return true;
   }
 
-  jio_fprintf(defaultStream::error_stream(),
-              "Unrecognized VM option '%s'\n", argname);
+  // For locked flags, report a custom error message if available.
+  // Otherwise, report the standard unrecognized VM option.
+
+  Flag* locked_flag = Flag::find_flag((char*)argname, strlen(argname), true);
+  if (locked_flag != NULL) {
+    char locked_message_buf[BUFLEN];
+    locked_flag->get_locked_message(locked_message_buf, BUFLEN);
+    if (strlen(locked_message_buf) == 0) {
+      jio_fprintf(defaultStream::error_stream(),
+        "Unrecognized VM option '%s'\n", argname);
+    } else {
+      jio_fprintf(defaultStream::error_stream(), "%s", locked_message_buf);
+    }
+  }
+
   // allow for commandline "commenting out" options like -XX:#+Verbose
   return arg[0] == '#';
 }

--- a/src/share/vm/runtime/globals.cpp	Mon Mar 19 10:09:24 2012 +0100
+++ b/src/share/vm/runtime/globals.cpp	Tue Mar 20 16:46:39 2012 -0400
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2011, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2012, 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
@@ -81,6 +81,12 @@
   }
 }
 
+// Get custom message for this locked flag, or return NULL if
+// none is available.
+void Flag::get_locked_message(char* buf, int buflen) const {
+  get_locked_message_ext(buf, buflen);
+}
+
 bool Flag::is_writeable() const {
   return strcmp(kind, "{manageable}") == 0 ||
          strcmp(kind, "{product rw}") == 0 ||
@@ -260,17 +266,22 @@
   return strncmp(s, q, len) == 0;
 }
 
-Flag* Flag::find_flag(char* name, size_t length) {
-  for (Flag* current = &flagTable[0]; current->name; current++) {
+// Search the flag table for a named flag
+Flag* Flag::find_flag(char* name, size_t length, bool allow_locked) {
+  for (Flag* current = &flagTable[0]; current->name != NULL; current++) {
     if (str_equal(current->name, name, length)) {
+      // Found a matching entry.  Report locked flags only if allowed.
       if (!(current->is_unlocked() || current->is_unlocker())) {
-        // disable use of diagnostic or experimental flags until they
-        // are explicitly unlocked
-        return NULL;
+        if (!allow_locked) {
+          // disable use of locked flags, e.g. diagnostic, experimental,
+          // commercial... until they are explicitly unlocked
+          return NULL;
+        }
       }
       return current;
     }
   }
+  // Flag name is not in the flag table
   return NULL;
 }
 

--- a/src/share/vm/runtime/globals.hpp	Mon Mar 19 10:09:24 2012 +0100
+++ b/src/share/vm/runtime/globals.hpp	Tue Mar 20 16:46:39 2012 -0400
@@ -222,7 +222,7 @@
   // number of flags
   static size_t numFlags;
 
-  static Flag* find_flag(char* name, size_t length);
+  static Flag* find_flag(char* name, size_t length, bool allow_locked = false);
 
   bool is_bool() const        { return strcmp(type, "bool") == 0; }
   bool get_bool() const       { return *((bool*) addr); }
@@ -259,6 +259,9 @@
   bool is_writeable_ext() const;
   bool is_external_ext() const;
 
+  void get_locked_message(char*, int) const;
+  void get_locked_message_ext(char*, int) const;
+
   void print_on(outputStream* st, bool withComments = false );
   void print_as_flag(outputStream* st);
 };

--- a/src/share/vm/runtime/globals_ext.hpp	Mon Mar 19 10:09:24 2012 +0100
+++ b/src/share/vm/runtime/globals_ext.hpp	Tue Mar 20 16:46:39 2012 -0400
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2011 Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2011, 2012, 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
@@ -61,4 +61,9 @@
   return false;
 }
 
+inline void Flag::get_locked_message_ext(char* buf, int buflen) const {
+  assert(buf != NULL, "Buffer cannot be NULL");
+  buf[0] = '\0';
+}
+
 #endif // SHARE_VM_RUNTIME_GLOBALS_EXT_HPP