the rules around acquiring locks have been strictly defined and
implemented, and general lock usage has been improved, to fix and
prevent several different issues.
a vm-region is now destroyed in two separate steps:
1. it is "killed": all mappings are unmapped and deleted, the
region is removed from its parent, and the region and all of
its sub-regions are marked as "dead", preventing any
further actions from being performed with the region.
2. it is "destroyed": the vm-region object is de-allocated when
the last reference/handle is closed. the references that this
region holds to any sub-regions are also released, meaning
these regions may also be de-allocated too.
the %gs base address is now always set to the current cpu block while
in kernel-mode, and is switched back to the userspace %gs base
when returning to user-mode.
this patch must now be done by the wider OS build system, to avoid
interference with any bootloaders that don't support this kind of
patching (e.g GRUB i386-pc)
the lowest 2 bits of handle values are no longer unused, and 0 is
now a valid handle value.
the first 64 handles are now reserved, and will not be automatically
allocated by the kernel. however, they are still valid handles, and
other handles can be moved to this area using an as-yet-unwritten
function. this is to allow support for standard POSIX file descriptors,
which require the values 0, 1, and 2.
all kernel headers have been moved from include/mango to include/kernel
and include definitions that are only relevant to kernel-space.
any definitions that are relevant to both kernel- and user-space
(i.e. type definitions, syscall IDs) have been moved to
include/mango within libmango.
