Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

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

Continue 7-CURRENT MAC Framework rearrangement and cleanup:

Don't perform a nested include of _label.h in mac.h, as mac.h now
describes only the user API to MAC, and _label.h defines the in-kernel
representation of MAC labels.

Remove mac.h includes from policies and MAC framework components that do
not use userspace MAC API definitions.

Add _KERNEL inclusion checks to mac_internal.h and mac_policy.h, as these
are kernel-only include files

Obtained from: TrustedBSD Project

Move mac_init_label() and mac_destroy_label() from mac_framework.c to
mac_label.c, and use these instead of replicated code in the label zone
constructor and destructor.

Obtained from: TrustedBSD Project

Staticize and comment zone_label.

Obtained from: TrustedBSD Project

Complete break-out of sys/sys/mac.h into sys/security/mac/mac_framework.h
begun with a repo-copy of mac.h to mac_framework.h. sys/mac.h now
contains the userspace and user<->kernel API and definitions, with all
in-kernel interfaces moved to mac_framework.h, which is now included
across most of the kernel instead.

This change is the first step in a larger cleanup and sweep of MAC
Framework interfaces in the kernel, and will not be MFC'd.

Obtained from: TrustedBSD Project
Sponsored by: SPARTA

In the MAC label zone destructor, assert that the label is only
destroyed in an initialized state.

* Add a "how" argument to uma_zone constructors and initialization functions
so that they know whether the allocation is supposed to be able to sleep
or not.
* Allow uma_zone constructors and initialation functions to return either
success or error. Almost all of the ones in the tree currently return
success unconditionally, but mbuf is a notable exception: the packet
zone constructor wants to be able to fail if it cannot suballocate an
mbuf cluster, and the mbuf allocators want to be able to fail in general
in a MAC kernel if the MAC mbuf initializer fails. This fixes the
panics people are seeing when they run out of memory for mbuf clusters.
* Allow debug.nosleepwithlocks on WITNESS to be disabled, without changing
the default.

Both bmilekic and jeff have reviewed the changes made to make failable
zone allocations work.

Modify the MAC Framework so that instead of embedding a (struct label)
in various kernel objects to represent security data, we embed a
(struct label *) pointer, which now references labels allocated using
a UMA zone (mac_label.c). This allows the size and shape of struct
label to be varied without changing the size and shape of these kernel
objects, which become part of the frozen ABI with 5-STABLE. This opens
the door for boot-time selection of the number of label slots, and hence
changes to the bound on the number of simultaneous labeled policies
at boot-time instead of compile-time. This also makes it easier to
embed label references in new objects as required for locking/caching
with fine-grained network stack locking, such as inpcb structures.

This change also moves us further in the direction of hiding the
structure of kernel objects from MAC policy modules, not to mention
dramatically reducing the number of '&' symbols appearing in both the
MAC Framework and MAC policy modules, and improving readability.

While this results in minimal performance change with MAC enabled, it
will observably shrink the size of a number of critical kernel data
structures for the !MAC case, and should have a small (but measurable)
performance benefit (i.e., struct vnode, struct socket) do to memory
conservation and reduced cost of zeroing memory.

NOTE: Users of MAC must recompile their kernel and all MAC modules as a
result of this change. Because this is an API change, third party
MAC modules will also need to be updated to make less use of the '&'
symbol.

Suggestions from: bmilekic
Obtained from: TrustedBSD Project
Sponsored by: DARPA, Network Associates Laboratories