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use crate::defs::*;
use crate::io::*;
use crate::machine::multiboot::MultibootMmap;
use core::ops::Range;
use core::slice;
extern "C" {
fn ___FREE_PAGE_STACK__();
}
/// There should only be one global instance of this.
pub struct PageStackAllocator {
page_stack: &'static mut [u64],
size: usize,
head: usize,
}
impl PageStackAllocator {
// covering 4GiB physical memory of 4K frames
const STACK_SIZE: usize = 0x100000;
pub fn new() -> Self {
let ps = Self {
page_stack: unsafe {
slice::from_raw_parts_mut(
P2V(___FREE_PAGE_STACK__ as u64).unwrap() as *mut u64,
Self::STACK_SIZE,
)
},
size: Self::STACK_SIZE,
head: 0,
};
return ps;
}
/// push an addr into the free page stack
/// MUST be atomic or bad things happen...
pub fn free_page(&mut self, addr: u64) -> bool {
if self.head >= self.size {
return false;
}
self.page_stack[self.head] = addr;
self.head += 1;
return true;
}
pub fn alloc_page(&mut self) -> Option<u64> {
if self.head == 0 {
return None;
}
self.head -= 1;
Some(self.page_stack[self.head])
}
/// 4k page only?
pub fn insert_range(&mut self, r: &Range<u64>) -> u64 {
// r.contains(&1);
let mut inserted = 0;
let mut page = roundup_4k(r.start);
loop {
if !r.contains(&page) {
break;
}
if !self.free_page(page) {
break;
} else {
inserted += 1;
}
page += 0x1000;
}
return inserted;
}
}
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