Introduce accessor functions mac_label_get() and mac_label_set() to replace

LABEL_TO_SLOT() macro used by policy modules to query and set label data
in struct label.  Instead of using a union, store an intptr_t, simplifying
the API.

Update policies: in most cases this required only small tweaks to current
wrapper macros.  In two cases, a single wrapper macros had to be split into
separate get and set macros.

Move struct label definition from _label.h to mac_internal.h and remove
_label.h.  With this change, policies may now treat struct label * as
opaque, allowing us to change the layout of struct label without breaking
the policy module ABI.  For example, we could make the maximum number of
policies with labels modifiable at boot-time rather than just at
compile-time.

Obtained from:	TrustedBSD Project

1 files changed, 3 insertions, 7 deletions

diff --git a/sys/security/mac/mac_policy.h b/sys/security/mac/mac_policy.h
index 750218f..c3c435c 100644
--- a/sys/security/mac/mac_policy.h
+++ b/sys/security/mac/mac_policy.h
@@ -47,8 +47,6 @@
 #error "no user-serviceable parts inside"
 #endif
 
-#include <sys/_label.h>
-
 /*-
  * Pluggable access control policy definition structure.
  *
@@ -970,11 +968,9 @@ int	mac_policy_modevent(module_t mod, int type, void *data);
 /*
  * Policy interface to map a struct label pointer to per-policy data.
  * Typically, policies wrap this in their own accessor macro that casts a
- * void pointer to a policy-specific data type.
- *
- * XXXRW: It might be preferable to provide get/set methods via functions to
- * avoid encoding the struct label layout in compiled modules.
+ * uintptr_t to a policy-specific data type.
  */
-#define	LABEL_TO_SLOT(l, s)	(l)->l_perpolicy[s]
+intptr_t	mac_label_get(struct label *l, int slot);
+void		mac_label_set(struct label *l, int slot, intptr_t v);
 
 #endif /* !_SYS_SECURITY_MAC_MAC_POLICY_H_ */