Revert r330897:

This was intended to be a non-functional change. It wasn't. The commit
message was thus wrong. In addition it broke arm, and merged crypto
related code.

Revert with prejudice.

This revert skips files touched in r316370 since that commit was since
MFCed. This revert also skips files that require $FreeBSD$ property
changes.

Thank you to those who helped me get out of this mess including but not
limited to gonzo, kevans, rgrimes.

Requested by: gjb (re)

Partial merge of the SPDX changes

These changes are incomplete but are making it difficult
to determine what other changes can/should be merged.

No objections from: pfg

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

Convert hwpmc(4) debug printfs over to KTR.

Differential Revision: https://reviews.freebsd.org/D2487
Reviewed by: davide, emaste
MFC after: 2 weeks
Sponsored by: Norse Corp, Inc.

malloc(9) cannot return NULL if M_WAITOK flag is specified.

Add a generic way to call per event allocate / release function.

Reviewed by: mav
MFC after: 1 month

Add support for good old 8192Hz profiling clock to software PMC.

Reviewed by: fabient

Change the way how software PMC updates counters.
This at least fixes -n option of pmcstat.

Reviewed by: fabient

Quiesce a couple of clang warnings

Submitted by: hiren panchasara <hiren.panchasara@gmail.com>
Obtained from: Yahoo! Inc

Add software PMC support.

New kernel events can be added at various location for sampling or counting.
This will for example allow easy system profiling whatever the processor is
with known tools like pmcstat(8).

Simultaneous usage of software PMC and hardware PMC is possible, for example
looking at the lock acquire failure, page fault while sampling on
instructions.

Sponsored by: NETASQ
MFC after: 1 month