diff --git a/HACKING b/HACKING
index bda37897b2..fdad7c3247 100644
--- a/HACKING
+++ b/HACKING
@@ -57,3 +57,7 @@ Third-party Code and License Overview
   Source: kexec-tools, http://www.xmission.com/~ebiederm/files/kexec/
   Current version we use: kexec-tools 1.101
 
+* lib/clog2.c: Triple-licensed, MPL 1.1/GPL 2.0/LGPL 2.1
+  Source: http://lxr.mozilla.org/mozilla1.8.0/source/js/src/jscpucfg.c
+  Current version we use: CVS rev. 3.25
+
diff --git a/lib/clog2.c b/lib/clog2.c
index 36abd4f93d..221109d164 100644
--- a/lib/clog2.c
+++ b/lib/clog2.c
@@ -1,4 +1,10 @@
-/* log 2 in c, from mozilla, from jscpucfg.c */
+/*
+ * This file is part of the LinuxBIOS project.
+ *
+ * It is based on the file js/src/jscpucfg.c from Mozilla, CVS rev. 3.25.
+ * See http://lxr.mozilla.org/mozilla1.8.0/source/js/src/jscpucfg.c.
+ */
+
 /* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
  *
  * ***** BEGIN LICENSE BLOCK *****