blog_os/src/allocator.rs

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Rust
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2019-10-01 16:19:13 -04:00
use alloc::alloc::{GlobalAlloc, Layout};
use core::ptr::null_mut;
use x86_64:: {
structures::paging:: {
FrameAllocator,
mapper::MapToError,
Mapper,
Page,
PageTableFlags,
Size4KiB,
},
VirtAddr,
};
pub const HEAP_START: usize = 0x_4444_4444_0000;
pub const HEAP_SIZE: usize = 100 * 1024; // 100 KiB
pub struct Dummy;
unsafe impl GlobalAlloc for Dummy {
unsafe fn alloc(&self, _layout: Layout) -> *mut u8 {
null_mut()
}
unsafe fn dealloc(&self, _ptr: *mut u8, _layout: Layout) {
panic!("dealloc should never be called")
}
}
pub fn init_heap(
mapper: &mut impl Mapper<Size4KiB>,
frame_allocator: &mut impl FrameAllocator<Size4KiB>,
) -> Result<(), MapToError> {
let page_range = {
let heap_start = VirtAddr::new(HEAP_START as u64);
let head_end = heap_start + HEAP_SIZE - 1u64;
let heap_start_page = Page::containing_address(heap_start);
let heap_end_page = Page::containing_address(head_end);
Page::range_inclusive(heap_start_page, heap_end_page)
};
for page in page_range {
let frame = frame_allocator
.allocate_frame()
.ok_or(MapToError::FrameAllocationFailed)?;
let flags = PageTableFlags::PRESENT | PageTableFlags::WRITABLE;
unsafe { mapper.map_to(page, frame, flags, frame_allocator)?.flush() };
}
unsafe {
super::ALLOCATOR.lock().init(HEAP_START, HEAP_SIZE);
}
Ok(())
}