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ableOS_v1Change/ableos/src/arch/x86_64/memory.rs

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2021-11-22 08:58:35 -06:00
use bootloader::bootinfo::{MemoryMap, MemoryRegionType};
use x86_64::{
structures::paging::{
FrameAllocator, Mapper, OffsetPageTable, Page, PageTable, PhysFrame, Size4KiB,
},
PhysAddr, VirtAddr,
};
pub unsafe fn init(physical_memory_offset: VirtAddr) -> OffsetPageTable<'static> {
let level_4_table = active_level_4_table(physical_memory_offset);
OffsetPageTable::new(level_4_table, physical_memory_offset)
}
unsafe fn active_level_4_table(physical_memory_offset: VirtAddr) -> &'static mut PageTable {
use x86_64::registers::control::Cr3;
let (level_4_table_frame, _) = Cr3::read();
let phys = level_4_table_frame.start_address();
let virt = physical_memory_offset + phys.as_u64();
let page_table_ptr: *mut PageTable = virt.as_mut_ptr();
// THIS IS UNSAFE
&mut *page_table_ptr
}
fn translate_addr_inner(addr: VirtAddr, physical_memory_offset: VirtAddr) -> Option<PhysAddr> {
use x86_64::registers::control::Cr3;
use x86_64::structures::paging::page_table::FrameError;
let (level_4_table_frame, _) = Cr3::read();
let table_indexes = [
addr.p4_index(),
addr.p3_index(),
addr.p2_index(),
addr.p1_index(),
];
let mut frame = level_4_table_frame;
for &index in &table_indexes {
// convert the frame into a page table reference
let virt = physical_memory_offset + frame.start_address().as_u64();
let table_ptr: *const PageTable = virt.as_ptr();
let table = unsafe { &*table_ptr };
let entry = &table[index];
frame = match entry.frame() {
Ok(frame) => frame,
Err(FrameError::FrameNotPresent) => return None,
Err(FrameError::HugeFrame) => panic!["huge pages not supported"],
};
}
Some(frame.start_address() + u64::from(addr.page_offset()))
}
pub unsafe fn translate_addr(addr: VirtAddr, physical_memory_offset: VirtAddr) -> Option<PhysAddr> {
translate_addr_inner(addr, physical_memory_offset)
}
pub fn create_example_mapping(
page: Page,
mapper: &mut OffsetPageTable,
frame_allocator: &mut impl FrameAllocator<Size4KiB>,
) {
use x86_64::structures::paging::PageTableFlags as Flags;
let frame = PhysFrame::containing_address(PhysAddr::new(0xb8000));
let flags = Flags::PRESENT | Flags::WRITABLE;
let map_to_result = unsafe { mapper.map_to(page, frame, flags, frame_allocator) };
map_to_result.expect("map_to failed").flush();
}
pub struct EmptyFrameAllocator;
unsafe impl FrameAllocator<Size4KiB> for EmptyFrameAllocator {
fn allocate_frame(&mut self) -> Option<PhysFrame<Size4KiB>> {
None
}
}
2021-11-22 08:58:35 -06:00
pub struct BootInfoFrameAllocator {
memory_map: &'static MemoryMap,
next: usize,
}
impl BootInfoFrameAllocator {
pub unsafe fn init(memory_map: &'static MemoryMap) -> Self {
Self {
memory_map,
next: 0,
}
}
fn usable_frames(&self) -> impl Iterator<Item = PhysFrame> {
let regions = self.memory_map.iter();
let usable_regions = regions.filter(|r| r.region_type == MemoryRegionType::Usable);
let addr_range = usable_regions.map(|r| r.range.start_addr()..r.range.end_addr());
let frame_address = addr_range.flat_map(|r| r.step_by(4096));
frame_address.map(|addr| PhysFrame::containing_address(PhysAddr::new(addr)))
}
}
unsafe impl FrameAllocator<Size4KiB> for BootInfoFrameAllocator {
fn allocate_frame(&mut self) -> Option<PhysFrame<Size4KiB>> {
let frame = self.usable_frames().nth(self.next);
self.next += 1;
frame
}
}