Add Process heap about emerald HOT 1 CLOSED

const HEAP_OFFSET_FROM_ELF_END: usize = 1 * MB;
const DEAFULT_MAX_HEAP_SIZE: usize = 1 * GB;

let (_min_addr, max_addr) = load_elf_to_vm(elf, file, &mut vm)?;

 // set it quite a distance from the elf and align it to 2MB pages (we are not using 2MB virtual memory, so its not related)
let heap_start = align_up(max_addr + HEAP_OFFSET_FROM_ELF_END, PAGE_2M);
let heap_size = 0; // start at 0, let user space programs control it
let heap_max = DEAFULT_MAX_HEAP_SIZE;

/// Add/Remove to/from the heap and return the previous end of the heap before the change
/// If this is an `Add` (positive), it will return the address of the new block
/// If this is a `Remove` (negative), the result will generally be useless
/// Use with `0` to get the current heap end
fn sys_inc_heap(increment: isize);