selinux: generate flask headers during kernel build

Add a simple utility (scripts/selinux/genheaders) and invoke it to
generate the kernel-private class and permission indices in flask.h
and av_permissions.h automatically during the kernel build from the
security class mapping definitions in classmap.h.  Adding new kernel
classes and permissions can then be done just by adding them to classmap.h.

Signed-off-by:  Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: James Morris <jmorris@namei.org>
diff --git a/security/selinux/Makefile b/security/selinux/Makefile
index d47fc5e..f013982 100644
--- a/security/selinux/Makefile
+++ b/security/selinux/Makefile
@@ -18,5 +18,13 @@
 
 selinux-$(CONFIG_NETLABEL) += netlabel.o
 
-EXTRA_CFLAGS += -Isecurity/selinux/include
+EXTRA_CFLAGS += -Isecurity/selinux -Isecurity/selinux/include
 
+$(obj)/avc.o: $(obj)/flask.h
+
+quiet_cmd_flask = GEN     $(obj)/flask.h $(obj)/av_permissions.h
+      cmd_flask = scripts/selinux/genheaders/genheaders $(obj)/flask.h $(obj)/av_permissions.h
+
+targets += flask.h
+$(obj)/flask.h: $(src)/include/classmap.h FORCE
+	$(call if_changed,flask)