Memory Management
=================

Memory management is split into three layers: physical, virtual & the heap.

The **physical memory manager** (PMM) is responsible for allocating physical
memory. It gives `pmm_*` functions. The `pmm_allocPage()` function allocates a
4kB page frame and retuns its **physical address**.

The **virtual memory manager** (VMM) is responsible for allocating virtual
memory. It provides `vmm_*` functions. The `vmm_alloc()` function takes in a
number of 4kB pages to allocate and returns the **virtual address** of the
first page. Userspace can interface with the VMM using the `mmap()` and
`munmap()` syscalls.

**The heap** is an area of memory that both kernel and user space have. 
Kernel space uses the `kalloc()` and it's derivative functions for the heap.
User space may use the `brk()` and `sbrk()` syscalls to grow and shrink the
heap.