MFC r315803:

memguard(9): fix igor/manlint warnings

- Expand a contraction [1].
- Add a missing section number when referring to uma(9) with .Xr .

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

Remove the BUGS entry in memguard's man page.

UMA refcounting is gone as of r296243, so this bug no longer exists. In
particular, it's now possible to guard mbuf clusters with memguard.

use .Mt to mark up email addresses consistently (part6)

PR: 191174
Submitted by: Franco Fichtner <franco at lastsummer.de>

Rename global cnt to vm_cnt to avoid shadowing.

To reduce the diff struct pcu.cnt field was not renamed, so
PCPU_OP(cnt.field) is still used. pc_cnt and pcpu are also used in
kvm(3) and vmstat(8). The goal was to not affect externally used KPI.

Bump __FreeBSD_version_ in case some out-of-tree module/code relies on the
the global cnt variable.

Exp-run revealed no ports using it directly.

No objection from: arch@
Sponsored by: EMC / Isilon Storage Division

Spelling.

Submitted by: dougb

Note that it is still not possible to guard special kind of allocations, those
that have special relationships with uma(9). Currently only mbuf clusters.

Document that memguard(9) now can guard uma(9) allocations.

Rework memguard(9) to reserve significantly more KVA to detect
use-after-free over a longer time. Also release the backing pages of
a guarded allocation at free(9) time to reduce the overhead of using
memguard(9). Allow setting and varying the malloc type at run-time.
Add knobs to allow:

- randomly guarding memory
- adding un-backed KVA guard pages to detect underflow and overflow
- a lower limit on the size of allocations that are guarded

Reviewed by: alc
Reviewed by: brueffer, Ulrich Spörlein <uqs spoerlein net> (man page)
Silence from: -arch
Approved by: zml (mentor)
MFC after: 1 month

Markup fixes.

Document how to find a short description of a memory type.

Xref redzone(9)

Update manual page after last memguard changes.

Glanced at by: simon

First cut at a manpage for the MemGuard debugging allocator.

most content from: bmilekic
mdoc lessons by: ru