trivial: fix header files

Signed-off-by: Curtis Millar <curtis.millar@data61.csiro.au>

replacing all ifndef with pargma once

All the kernel header files now use pargma once rather than the ifndef,
as the pre-processed C files do not change while header files
are protected with pargma once. This will also solve any naming issues
caused by ifndef.

Convert license tags to SPDX identifiers

This commit also converts our own copyright headers to directly use
SPDX, but leaves all other copyright header intact, only adding the
SPDX ident. As far as possible this commit also merges multiple
Data61 copyright statements/headers into one for consistency.

RFC-3: Update context for x86 to use FS and GS.

TLS_BASE virtual register is replaced with FS_BASE and GS_BASE virtual
registers.

The FS_BASE and GS_BASE virtual registers are moved to the end of the
context so they need not be considered in the kernel exit and entry
implementation.

Removed tracking of ES, DS, FS, and GS segment selectors on kernel entry
and exit.

ES and DS are clobbered on kernel entry with the RPL 3 selector for a
DPL 3 linear data segment.

FS is clobbered on exit with the RPL 3 selector for the DPL 3 segment
with FS_BASE as the base. This is done on exit to reload the value from
the GDT.

GS is clobbered on exit with the RPL 3 selector for the DPL 3 segment
with GS_BASE as the base. This is done on exit to reload the value from
the GDT.

Kernel entry and exit code is refactored, simplified, and improved in
light of the above changes.

x64: update verified config to use fsgsbase instr

The verification platform for x64 relies on the fsgsbase instruction.

style: consistently align pointer with name

Run astyle with align-pointer=name

style: correct parenthesis padding

Use astyle's unpad-paren to unpad all parentheses that are not included
by pad-header, pad-oper, and pad-comma.

[STYLE_FIX]

x64: SKIM window to mitigate Meltdown (CVE-2017-5754) on x86-64

Introduces a kernel option that, when enabled, reduces the kernel window in a user address
space to just be Static Kernel Image and Microstate (SKIM), instead of the full kernel
address space. This isolates the important kernel data from the user preventing a
Meltdown style attack being able to violate secrecy. The kernel text and read only data,
i.e. anything that is static from boot, is not secret and can be allowed in the SKIM window
and potentially read by the user. Additionally to switch to and from the actual kernel
address space a small amount of state needs to also be in the SKIM window.

This is only an implementation for x86-64, although the same design is applicable to ia32

x64: Invalid ASID with single asm block

This performs a double address space switch to invalidate an ASID using a single hand
written asm block instead of setCurrentCR3. The purpose of this is to ensure that the
only requirements on the temporary address space that we switch to is that the kernel
code is still mapped in at the same location. As we ensure our old cr3 value is in
register we can ensure, unlike with calling getCurrentCR3 that no stack or other
temporary memory is required.

x64: If PCIDs are not enabled forbid them in any CR3 values

When PCIDs are not enabled the low 12 bits of CR3 are not all ignored as bits 3 and 4 control
memory typing of the translation. To prevent setting these to 'random' values we should leave
the low bits of CR3 0 when not using PCIDs.

A new makeCR3 wrapper is defined that is used instead of cr3_new that, based on CONFIG_SUPPORT_PCID,
either fills in the PCID or 0 as required.

x64: Separate notion of current vspace root with current user vspace root

This introduces functions for specifically manipulating the user vspace root, either as an
abstract root or the specific CR3 value, in a way that is separated from the current vspace
root. Currently they are one and the same, but this separation allows for having the kernel
translation (and hence the active vspace root) be different the currently active user.

Fix licenses (the rest)

x86: Remove trailing semicolons in asm statements

These semicolons are not actually necessary, and cause problems for the C parser

s/D61/DATA61/ in license headers for consistency

[STYLE_FIX]

x86: Implement safe rdmsr function

Implements a safe version of `x86_rdmsr` that can return success or failure depending
on if the rdmsr caused a GP fault

x86: Avoid writing the fs/gs base if we don't have to

x64: Multicore TLB coherency

x64: Support multiple kernel stacks

Adds support for per-core kernel stacks through the use of
thread local storage and swapgs. In addition to the main
kernel stack the IRQ stack also needs to be made per core

x64: Access core local state correctly

SELFOUR-634: support for TLB and cache management

Replace #pragma once with include guards

[STYLE_FIX]

x64: Correctly invalidate PCIDs

x64: Add x86_64 support