This branch contains vastly improved kernel memory
subsystem with following new features:
* 2M/1G pages
* Lazy copying/lazy memory allocation
* Used for speeding up ASAN memory allocation
* Kernel memory is also lazily allocated
* NX flag
* Buddy physical memory allocator
* O((log N)^2) region manipulation
* More convenient syscall API
* IPC with memory regions of size larger than 4K
* Not used at the moment but would be useful
for file server optimization
* Reduced memory consumption by a lot
* All supported sanitizers can work simultaneously
with any amount of memory (as long as bootloader can allocate enough memory for the kernel)
The code is mostly located in kern/pmap.c
A set of trees is used for holding metadata (nodes are of type struct Page):
* A tree describing physical memory
* One tree for every address space (for every environment and kernel)
TODO
* Replace user_mem_assert with exception-based code
* copyin/copyout functions
* Refactor address space and move all kernel-only memory
regions to canonical upper part of address space
(this requires copyin/copyout functions because
ASAN should never touch user-space memory)