Repair barriers in clh_lock_acquire

Strengthen the clh_lock_acquire to use release on the atomic_exchange
that makes the node public. Otherwise (on ARM & RISCV), the store to
the node value which sets its state to CLHState_Pending can become
visible some time after the node is visible.
In that window of time, the next thread which attempts to acquire the
lock will still see the old state (CLHState_Granted) and enters the
critical section, leading to a mutual exclusion violation.

Signed-off-by: jonas <s9joober@gmail.com>

Repair barriers in sel4_atomic_exchange

The implementation of try_arch_atomic_exchange does not correctly pass
RELEASE memory ordering (or stronger) to the exchange operation.
To acknowledge this, try_arch_atomic_exchange is replaced by a relaxed
try_arch_atomic_exchange_rlx which does not apply any memory ordering.
Instead, the memory ordering is now added manually by
sel4_atomic_exchange. This provides better latency for interrupts as no
barriers are evoked inside the loop which performs the relaxed exchange
and checks for interrupts.
Furthermore, the new manual application of barriers ensures the memory
ordering passed to sel4_atomic_exchange.

Signed-off-by: jonas <s9joober@gmail.com>

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.

arm,SMP: Refactor irq_t structure for smp

Explicitly create a struct definition for irq_t on SMP Arm
configurations. This makes it a lot harder to mistakenly use the wrong
irq encoding when moving an irq between a cnode index and hardware irq
number / core. A couple areas where this was being handled incorrectly
was fixed as part of the refactor. When performing an ipi for masking
PPI interrupts, the idx encoding is used as it fits into a single word.

style: consistently attach return type

Add attach-return-type to astyle

style: consistently align pointer with name

Run astyle with align-pointer=name

ARM/SMP: Re-implement atomic exchange taking sel4 IPI into account

smp: Use explicit fences instead of volatile

This provides a more robust and efficient implementation that only forces memory reloads
at explicit known points, instead of the over approximation of every time they are
accessed that is forced by volatile.

SMP: Introduce ENABLE_SMP_SUPPORT

- Make it more readable and less confusing compared to the 'CONFIG_MAX_NUM_NODES > 1' check

SELFOUR-747: SMP/x86: generalize arch-independent IPI code

Fix licenses (the rest)

smp: fix bugs when stalling remote core

- Restart TCB from inside the lock if it is waiting for anything other than IRQ
- Only replace the TCB with idle thread if it is in ThreadState_RunningVM state

Also, this makes the design generic to be shared with arm.

s/D61/DATA61/ in license headers for consistency

[STYLE_FIX]

SMP: use C++11 __atomic builtins instead of legacy __sync buitins

SMP: move lock.h to architecture-independent include/smp

s/__sync_lock_test_and_set/__atomic_exchange_n in lock.h