Remove /^\s*\*\n \*\s+\$FreeBSD\$$\n/

The SPDX folks have obsoleted the BSD-2-Clause-FreeBSD identifier. Catch
up to that fact and revert to their recommended match of BSD-2-Clause.

Discussed with:		pfg
MFC After:		3 days
Sponsored by:		Netflix

vm_ooffset_t is now unsigned. Remove some tests for negative values,
or make other adjustments accordingly.

Reported by:	Coverity
Reviewed by:	kib markj
Sponsored by:	Dell EMC Isilon
Differential Revision:	https://reviews.freebsd.org/D26214

Future changes would require additional initialization of OBJT_PHYS
objects, and vm_object_allocate() is not suitable for it.

Reviewed by:	markj
Tested by:	pho
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Differential revision:	https://reviews.freebsd.org/D24652

It turns out relocating the symbol table itself can cause issues, like fbt
crashing because it applies the offsets to the kernel twice.

This had been previously brought up in rS333447 when the stoffs hack was
added, but I had been unaware of this and reimplemented symtab relocation.

Instead of relocating the symbol table, keep track of the relocation base
in ddb, so the ddb symbols behave like the kernel linker-provided symbols.

This is intended to be NFC on platforms other than PowerPC, which do not
use fully relocatable kernels. (The relbase will always be 0)

 * Remove the rest of the stoffs hack.
 * Remove my half-baked displace_symbol_table() function.
 * Extend ddb initialization to cope with having a relocation offset on the
   kernel symbol table.
 * Fix my kernel-as-initrd hack to work with booke64 by using a temporary
   mapping to access the data.
 * Fix another instance of __powerpc__ that is actually RELOCATABLE_KERNEL.
 * Change the behavior or X_db_symbol_values to apply the relocation base
   when updating valp, to match link_elf_symbol_values() behavior.

Reviewed by:	jhibbits
Sponsored by:	Tag1 Consulting, Inc.
Differential Revision:	https://reviews.freebsd.org/D25223

The pages stored in the ksyms object are not pageable.  Moreover, this
obviates the need to set OBJ_NOSPLIT.

Reviewed by:	alc, kib
MFC after:	3 days
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D22229

The object does not provide anonymous memory.

Reported by:	kib
Reviewed by:	kib
MFC after:	3 days
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D22123

Summary:
PowerPC kernels are fully position independent, just like kernel modules.
The same fixups that are done for modules therefore need to be done to the
kernel, else symbol resolution in, e.g., DTrace, cannot resolve the kernel
symbols, so only addresses in the kernel are printed, while kernel module
symbols are printed.

Test Plan:
Run lockstat on powerpc64.  Note symbols are resolved for kernel and
modules.

Reviewed By: markj
Differential Revision: https://reviews.freebsd.org/D20316

Mainly focus on files that use BSD 2-Clause license, however the tool I
was using misidentified many licenses so this was mostly a manual - error
prone - task.

The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.

Reported by:	jhb
X-MFC with:	r321963