Previously context::switch used compare_and_swap for acquiring the
global context switch lock, but given its deprecation in more recent
Rust versions, it has been replaced with compare_exchange_weak (which
can be further optimized on some architectures).
It also replaces panic!() with abort() in switch_finish_hook, because
unwinding from assembly is not that fun.
This also removes the need to do another semi-expensive remap when
cloning processes, since the KPCRs (for kernel TLS) are no longer stored
in the user PML4.
We may also want to do this with the MADT and the HPET tables, and let
user drivers specify what the tables mean independent of ACPI. That is,
adding an interface for registering new CPUs, and specifying the main
timer IRQ.
Currently, there are some things that need to be set up by userspace
that the kernel previously did. These include telling firmware when the
I/O APIC is used, and most importantly, shutting down the system.
The former is not particularly important, but for the latter I think
that we could implement this using a "shutdown pipe". Essentially it
will be a file that triggers an event shutting down, which would be used
to notify to acpid that the kernel is requesting a shutdown.
This allows schemes to avoid checking the length against zero before
constructing a slice from pointer+len that the kernel gave.
Additionally, the address is now non-canonical on x86, meaning that
userspace will fail instead of continuing with UB, if they would ever
forget to check the length.
4lDO2