Breaking changes

• Added support for EL2 and EL3 page tables. This requires a new parameter to IdMap::new,
  LinearMap::new, Mapping::new and RootTable::new.
• Attributes::EXECUTE_NEVER renamed to Attributes::UXN.
• Attributes::DEVICE_NGNRE and NORMAL have been removed in favour of ATTRIBUTE_INDEX_*,
  OUTER_SHAREABLE and INNER_SHAREABLE, to avoid making assumptions about how the MAIR registers
  are programmed.

New features

• Added root_address, mark_active and mark_inactive methods to IdMap, LinearMap and
  Mapping. These may be used to activate and deactivate the page table manually rather than
  calling activate and deactivate.
• Added NS and PXN bits to Attributes.

Bug fixes

• When an invalid descriptor is split into a table, the table descriptors aren't set unless to
  non-zero values unless the original descriptor was.

Other changes

• Attributes::ACCESSED is no longer automatically set on all new mappings. To maintain existing
  behaviour you should explicitly set Attributes::ACCESSED whenever calling map_range for a
  valid mapping.

Bug fixes

• Reject the PAGE_OR_TABLE flag when passed to map_range, which would result in corrupt table
  mappings to be created.

Breaking changes

• Updated modify_range to split block entries before traversing them, and pass only the
  descriptors and subregions that are completely covered by the given region to the updater callback
  function.
• Updated modify_range to only pass block or page descriptors to the callback function and prevent
  them from being converted into table descriptors inadvertently.
• Added rigid break-before-make (BBM) checks to map_range and modify_range.
• Marked activate and deactivate methods as unsafe.

New features

• Added new map_range() alternative map_range_with_constraints() with extra contraints
  argument.
• Added walk_range method that iterates over all block or page descriptorsthat intersect with a
  given region, without permitting the callback to make changes to the descriptors

Bug fixes

• RootTable, Mapping, IdMap and LinearMap are now correctly marked as Send, as it doesn't
  matter where they are used from.

Breaking changes

• Updated bitflags to 2.0.2, which changes the API of Attributes a bit.
• Updated map_range method to support mapping leaf page table entries without the VALID flag.
  Attributes::VALID is no longer implicitly set when mapping leaf page table entries.

New features

• Added modify_range method to IdMap, LinearMap and Mapping to update details of a mapped
  range. This can be used e.g. to change flags for some range which is already mapped. As part of
  this, the Descriptor struct was added to the public API.
• Added DBM and software flags to Attributes.

Breaking changes

• Made Translation trait responsible for allocating page tables. This should help make it possible
  to use more complex mapping schemes, and to construct page tables in a different context to where
  they are used.
• Renamed AddressRangeError to MapError, which is now an enum with three variants and implements
  Display.
• From<*const T> and From<*mut T> are no longer implemented for VirtualAddress.
• Added support for using TTBR1 as well as TTBR0; this changes various constructors to take an extra
  parameter.

New features

• Made alloc dependency optional via a feature flag.
• Added support for linear mappings with new LinearMap.
• Implemented subtraction of usize from address types.

Bugfixes

• Fixed memory leak introduced in 0.2.0: dropping a page table will now actually free its memory.

New features

• Implemented Debug and Display for MemoryRegion.
• Implemented From<Range<VirtualAddress>> for MemoryRegion.
• Implemented arithmetic operations for PhysicalAddress and VirtualAddress.

Breaking changes

• Added bounds check to IdMap::map_range; it will now return an error if you attempt to map a
  virtual address outside the range of the page table given its configured root level.

New features

• Implemented Debug for PhysicalAddress and VirtualAddress.
• Validate that chosen root level is supported.

Bugfixes

• Fixed bug in Display and Drop implementation for RootTable that would result in a crash for
  any pagetable with non-zero mappings.
• Fixed Display implementation for PhysicalAddress and VirtualAddress to use correct number of
  digits.

Initial release.