The handling of page tables is very architecture specific, so belongs
in the Arch directory. Some parts were already architecture-specific,
however this commit moves the rest of the PageDirectory class into the
Arch directory.
While we're here the aarch64/PageDirectory.{h,cpp} files are updated to
be aarch64 specific, by renaming some members and removing x86_64
specific code.
Now that AddressSpace itself is always SpinlockProtected, we don't
need to also wrap the RegionTree. Whoever has the AddressSpace locked
is free to poke around its tree.
This forces anyone who wants to look into and/or manipulate an address
space to lock it. And this replaces the previous, more flimsy, manual
spinlock use.
Note that pointers *into* the address space are not safe to use after
you unlock the space. We've got many issues like this, and we'll have
to track those down as wlel.
This makes locking them much more straightforward, and we can remove
a bunch of confusing use of AddressSpace::m_lock. That lock will also
be converted to use of SpinlockProtected in a subsequent patch.
Until now, our kernel has reimplemented a number of AK classes to
provide automatic internal locking:
- RefPtr
- NonnullRefPtr
- WeakPtr
- Weakable
This patch renames the Kernel classes so that they can coexist with
the original AK classes:
- RefPtr => LockRefPtr
- NonnullRefPtr => NonnullLockRefPtr
- WeakPtr => LockWeakPtr
- Weakable => LockWeakable
The goal here is to eventually get rid of the Lock* classes in favor of
using external locking.
All users which relied on the default constructor use a None lock rank
for now. This will make it easier to in the future remove LockRank and
actually annotate the ranks by searching for None.
This patch adds RegionTree::get_lock() which exposes the internal lock
inside RegionTree. We can then lock it from the outside when doing
lookups or traversal.
This solution is not very beautiful, we should find a way to protect
this data with SpinlockProtected or something similar. This is a stopgap
patch to try and fix the currently flaky CI.
This patch move AddressSpace (the per-process memory manager) to using
the new atomic "place" APIs in RegionTree as well, just like we did for
MemoryManager in the previous commit.
This required updating quite a few places where VM allocation and
actually committing a Region object to the AddressSpace were separated
by other code.
All you have to do now is call into AddressSpace once and it'll take
care of everything for you.
RegionTree holds an IntrusiveRedBlackTree of Region objects and vends a
set of APIs for allocating memory ranges.
It's used by AddressSpace at the moment, and will be used by MM soon.
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 optimization was added when region lookup was O(n), before we had
the O(log n) RedBlackTree. Let's remove it to simplify the code, as we
have no evidence that it remains valuable.
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. :^)
