PERFORCE change 81723 for review

[Robert Watson]

http://perforce.freebsd.org/chv.cgi?CH=81723

Change 81723 by rwatson at rwatson_peppercorn on 2005/08/09 11:24:43

	Expand discussion of MAC Framework versioning.

Affected files ...

.. //depot/projects/trustedbsd/mac/sys/kern/kern_mac.c#447 edit

Differences ...

==== //depot/projects/trustedbsd/mac/sys/kern/kern_mac.c#447 (text+ko) ====

@@ -96,10 +96,21 @@
 
 #ifdef MAC
 
-/*
- * Declare that the kernel provides MAC support, version 1.  This permits
- * modules to refuse to be loaded if the necessary support isn't present,
- * even if it's pre-boot.
+/*-
+ * The TrustedBSD MAC Framework declares two version numbers in support of
+ * policy modules:
+ *
+ * - A linker version number, which declares the version of the MAC policy
+ *   ABI.
+ *
+ * - A feature version number, relative to the linker version, which declares
+ *   what if any optional features for the linker version are present.  This
+ *   supports the incremental addition of features in a FreeBSD RELENG
+ *   branch.
+ *
+ * Modules will be unable to load if they do not match the current linker
+ * version due to ABI compatibility concerns.  They may also test for support
+ * for specific API features that they depend on.
  */
 MODULE_VERSION(kernel_mac_support, 3);