In most cases it's safe to abort the requested operation and go forward,
however, in some places it's not clear yet how to handle these failures,
therefore, we use the MUST() wrapper to force a kernel panic for now.
On the QEMU microvm machine type, it became apparent that the BIOS was
not setting the i8042 controller to function as expected. To ensure that
the controller is always outputting correct scan codes, set it to scan
code 2 and enable first port translation to ensure all scan codes are
translated to scan code set 1. This is the expected behavior when using
SeaBIOS, but on qboot (the BIOS for the QEMU microvm machine type), the
firmware doesn't take care of this so we need to do this ourselves.
This keeps us from accidentally overwriting an already set region name,
for example when we are mapping a file (as, in this case, the file name
is already stored in the region).
Since KASLR was added kernel_load_base only signifies the address at
which the kernel image start, not the start of kernel memory, meaning
that a valid kernel stack can be allocated before it in memory.
We use kernel_mapping_base, the lowest address covered by the kernel
page directory, as the minimal address when performing safety checks
during backtrace generation.
When we lock a mutex, eventually `Thread::block` is invoked which could
in turn invoke `Process::big_lock().restore_exclusive_lock()`. This
would then try to add the current thread to a different blocked thread
list then the one in use for the original mutex being locked, and
because it's an intrusive list, the thread is removed from its original
list during the `.append()`. When the original mutex eventually
unblocks, we no longer have the thread in the intrusive blocked threads
list and we panic.
Solve this by making the big lock mutex special and giving it its own
blocked thread list. Because the process big lock is temporary and is
being actively removed from e.g. syscalls, it's a matter of time before
we can also remove the fix introduced by this commit.
Fixes issue #9401.
If we unregister from the RegionTree before unmapping, there's a race
where a new region can get inserted at the same address that we're about
to unmap. If this happens, ~Region() will then unmap the newly inserted
region, which now finds itself with cleared-out page table entries.
This had no business being in RegionTree, since RegionTree doesn't track
identity-mapped regions anyway. (We allow *any* address to be identity
mapped, not just the ones that are part of the RegionTree's range.)
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 syscall ends up disabling interrupts while changing the time,
and the clock is a global resource anyway, so preventing threads in the
same process from running wouldn't solve anything.
Let's use terminology from the the Intel manual to avoid confusion.
Also add `_string` suffixes to better distinguish the numeric values
from the string values.
...and remove the last remaining client of the API. It's no longer
possible to ask the RegionTree for a VM range. You can only ask it to
place your Region somewhere in available space.
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.
Instead of first allocating the VM range, and then inserting a region
with that range into the MM region tree, we now do both things in a
single atomic operation:
- RegionTree::place_anywhere(Region&, size, alignment)
- RegionTree::place_specifically(Region&, address, size)
To reduce the number of things we do while locking the region tree,
we also require callers to provide a constructed Region object.
This patch ports MemoryManager to RegionTree as well. The biggest
difference between this and the userspace code is that kernel regions
are owned by extant OwnPtr<Region> objects spread around the kernel,
while userspace regions are owned by the AddressSpace itself.
For kernelspace, there are a couple of situations where we need to make
large VM reservations that never get backed by regular VMObjects
(for example the kernel image reservation, or the big kmalloc range.)
Since we can't make a VM reservation without a Region object anymore,
this patch adds a way to create unbacked Region objects that can be
used for this exact purpose. They have no internal VMObject.)
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.
