This patch stops using VirtualRangeAllocator in AddressSpace and instead
looks for holes in the region tree when allocating VM space.
There are many benefits:
- VirtualRangeAllocator is non-intrusive and would call kmalloc/kfree
when used. This new solution is allocation-free. This was a source
of unpleasant MM/kmalloc deadlocks.
- We consolidate authority on what the address space looks like in a
single place. Previously, we had both the range allocator *and* the
region tree both being used to determine if an address was valid.
Now there is only the region tree.
- Deallocation of VM when splitting regions is no longer complicated,
as we don't need to keep two separate trees in sync.
This isn't a complete conversion to ErrorOr<void>, but a good chunk.
The end goal here is to propagate buffer allocation failures to the
caller, and allow the use of TRY() with formatting functions.
We now use AK::Error and AK::ErrorOr<T> in both kernel and userspace!
This was a slightly tedious refactoring that took a long time, so it's
not unlikely that some bugs crept in.
Nevertheless, it does pass basic functionality testing, and it's just
real nice to finally see the same pattern in all contexts. :^)
This commit moves the KResult and KResultOr objects to Kernel/API to
signify that they may now be freely used by userspace code at points
where a syscall-related error result is to be expected. It also exposes
KResult and KResultOr to the global namespace to make it nicer to use
for userspace code.
...and also RangeAllocator => VirtualRangeAllocator.
This clarifies that the ranges we're dealing with are *virtual* memory
ranges and not anything else.
