sys: Remove $FreeBSD$: two-line .h pattern

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

busdma: Add KMSAN integration

Sanitizer instrumentation of course cannot automatically update shadow
state when devices write to host memory. KMSAN thus hooks into busdma,
both to update shadow state after a device write, and to verify that the
kernel does not publish uninitalized bytes to devices.

To implement this, when KMSAN is configured, each dmamap embeds a memory
descriptor describing the region currently loaded into the map.
bus_dmamap_sync() uses the operation flags to determine whether to
validate the loaded region or to mark it as initialized in the shadow
map.

Note that in cases where the amount of data written is less than the
buffer size, the entire buffer is marked initialized even when it is
not. For example, if a NIC writes a 128B packet into a 2KB buffer, the
entire buffer will be marked initialized, but subsequent accesses past
the first 128 bytes are likely caused by bugs.

Reviewed by: kib
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D31338

x86: clean up empty lines in .c and .h files

o Move iommu_set_buswide_ctx, iommu_is_buswide_ctx to
the generic iommu busdma backend;
o Move bus_dma_iommu_set_buswide, bus_dma_iommu_load_ident
prototypes to iommu.h.

Reviewed by: kib
Sponsored by: DARPA, AFRL
Differential Revision: https://reviews.freebsd.org/D25866

o Move the buswide_ctxs bitmap to iommu_unit and rename related functions.
o Rename bus_dma_dmar_load_ident() as well.

Reviewed by: kib
Sponsored by: DARPA/AFRL
Differential Revision: https://reviews.freebsd.org/D25852

bus_dma_dmar_load_ident(9): load identity mapping into the map.

Requested, reviewed and tested by: mav
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D22559

Limit bus_dma_dmar_set_buswide() definition to kernel only.

The header is abused for inclusion into userspace, and on stable
branches neither device_t nor bool types are not defined when used
from userspace.

Sponsored by: The FreeBSD Foundation
X-MFC after: now

bus_dma_dmar_set_buswide(9): KPI to indicate that the whole dmar
context should share page tables.

Practically it means that dma requests from any device on the bus are
translated according to the entries loaded for the bus:0:0 device.
KPI requires that the slot and function of the device be 0:0, and that
no tags for other devices on the bus were used.

The intended use are NTBs which pass TLPs from the downstream to the
host with slot:func of the downstream originator.

Reviewed and tested by: mav
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D22434

Allow loading the same DMA address multiple times without any prior
unload for the LinuxKPI.

Reviewed by: kib, zeising
Sponsored by: Dell EMC Isilon
Differential Revision: https://reviews.freebsd.org/D20181

Clean up MD pollution of bus_dma.h:

--Remove special-case handling of sparc64 bus_dmamap* functions.
Replace with a more generic mechanism that allows MD busdma
implementations to generate inline mapping functions by
defining WANT_INLINE_DMAMAP in <machine/bus_dma.h>. This
is currently useful for sparc64, x86, and arm64, which all
implement non-load dmamap operations as simple wrappers
around map objects which may be bus- or device-specific.

--Remove NULL-checked bus_dmamap macros. Implement the
equivalent NULL checks in the inlined x86 implementation.
For non-x86 platforms, these checks are a minor pessimization
as those platforms do not currently allow NULL maps. NULL
maps were originally allowed on arm64, which appears to have
been the motivation behind adding arm[64]-specific barriers
to bus_dma.h, but that support was removed in r299463.

--Simplify the internal interface used by the bus_dmamap_load*
variants and move it to bus_dma_internal.h

--Fix some drivers that directly include sys/bus_dma.h
despite the recommendations of bus_dma(9)

Reviewed by: kib (previous revision), marius
Differential Revision: https://reviews.freebsd.org/D10729