Adding support for MAC_TASK_CONTEXTS and MAC_OBJ_CONTEXTS to userspace.

I'm looking at the audit userspace implications of adding two new kernel audit records. AUDIT_MAC_TASK_CONTEXTS and AUDIT_MAC_OBJ_CONTEXTS are used when there are multiple security modules with a "security context" active on the system. This design has been discussed here at length. The records will look like: AUDIT_MAC_TASK_CONTEXTS subj_<lsmname>=value subj_<lsmname>=value ... Looking at the audit user-space code I see several things that have me concerned. The first is the use of WITH_APPARMOR. Going forward what behavior would we want if subj_apparmor=something shows up on a system that has not got WITH_APPARMOR defined? The code is inconsistent in that it does not use WITH_SELINUX, but that's hardly a surprise given its origins. There is also no WITH_SMACK, but that's unlikely to be an issue since Smack's use of audit is very much like SELinux's. The question is what to do about filtering when subj=foo is specified. I suggest that if any of subj_selinux, subj_smack or subj_something is "foo", it is a match. But the SELinux components of a label (level, user, ...) are also available for filtering. If someone wrote a simple Bell & LaPadula LSM filtering by some of those fields could be useful there, too. I would like guidance on whether I ought to go the route of more extensive use of WITH_APPARMOR (and WITH_SMACK, WITH_MUMBLE) or take the path of greater generalization. Or, whether I should treat each case individually and give it my best whack. Thank you.