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

MFC r314148, r314150

r314148:
Misc Coverity fixes in xnb(4)

Most of these are null pointer dereferences or missing error checks in the
unit tests. One is a missing error check in xnb_attach_failed. None can
cause real problems in running systems.

Reported by: Coverity
CIDs: 1092469 1092468 1092467 2092466 1092465 1092512 1092511 1092510
CIDs: 1092510 1092509 1092508 1092507
Reviewed by: royger
MFC after: 3 weeks
Sponsored by: Spectra Logic Corp
Differential Revision: https://reviews.freebsd.org/D9234

r314150:
Fix the xnb(4) unit tests

One test was inadvertently expecting a bug in the kernel's sscanf
implementation circa 2012. I don't know when that bug got fixed.

Reported by: royger
Reviewed by: royger
MFC after: 3 weeks
Sponsored by: Spectra Logic Corp
Differential Revision: https://reviews.freebsd.org/D9766

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

sys/dev: minor spelling fixes.

Most affect comments, very few have user-visible effects.

Somehow fix LINT-NOIP.

Redo r242889, now using the method from projects/amd64_xen_pv r240747.

Reminded by: kib
MFC after: 3 days

Fix a typo.

Change the XNB_ASSERT from a statement expression to do-while(0) as its
result is never used.

s/ is is / is /g
s/ a a / a /g

Approved by: cperciva
MFC after: 3 days

Xen netback driver rewrite.

share/man/man4/Makefile,
share/man/man4/xnb.4,
sys/dev/xen/netback/netback.c,
sys/dev/xen/netback/netback_unit_tests.c:

Rewrote the netback driver for xen to attach properly via newbus
and work properly in both HVM and PVM mode (only HVM is tested).
Works with the in-tree FreeBSD netfront driver or the Windows
netfront driver from SuSE. Has not been extensively tested with
a Linux netfront driver. Does not implement LRO, TSO, or
polling. Includes unit tests that may be run through sysctl
after compiling with XNB_DEBUG defined.

sys/dev/xen/blkback/blkback.c,
sys/xen/interface/io/netif.h:

Comment elaboration.

sys/kern/uipc_mbuf.c:

Fix page fault in kernel mode when calling m_print() on a
null mbuf. Since m_print() is only used for debugging, there
are no performance concerns for extra error checking code.

sys/kern/subr_scanf.c:

Add the "hh" and "ll" width specifiers from C99 to scanf().
A few callers were already using "ll" even though scanf()
was handling it as "l".

Submitted by: Alan Somers <alans@spectralogic.com>
Submitted by: John Suykerbuyk <johns@spectralogic.com>
Sponsored by: Spectra Logic
MFC after: 1 week
Reviewed by: ken