forked from AbleOS/ableos
82 lines
2.4 KiB
Rust
82 lines
2.4 KiB
Rust
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use x86_64::{
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structures::paging::{
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FrameAllocator, Mapper, OffsetPageTable, Page, PageTable, PhysFrame, Size4KiB,
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},
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PhysAddr, VirtAddr,
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};
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pub unsafe fn init(physical_memory_offset: VirtAddr) -> OffsetPageTable<'static> {
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let level_4_table = active_level_4_table(physical_memory_offset);
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OffsetPageTable::new(level_4_table, physical_memory_offset)
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}
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unsafe fn active_level_4_table(physical_memory_offset: VirtAddr) -> &'static mut PageTable {
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use x86_64::registers::control::Cr3;
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let (level_4_table_frame, _) = Cr3::read();
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let phys = level_4_table_frame.start_address();
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let virt = physical_memory_offset + phys.as_u64();
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let page_table_ptr: *mut PageTable = virt.as_mut_ptr();
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// THIS IS UNSAFE
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&mut *page_table_ptr
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}
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fn translate_addr_inner(addr: VirtAddr, physical_memory_offset: VirtAddr) -> Option<PhysAddr> {
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use x86_64::registers::control::Cr3;
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use x86_64::structures::paging::page_table::FrameError;
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let (level_4_table_frame, _) = Cr3::read();
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let table_indexes = [
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addr.p4_index(),
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addr.p3_index(),
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addr.p2_index(),
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addr.p1_index(),
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];
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let mut frame = level_4_table_frame;
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for &index in &table_indexes {
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// convert the frame into a page table reference
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let virt = physical_memory_offset + frame.start_address().as_u64();
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let table_ptr: *const PageTable = virt.as_ptr();
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let table = unsafe { &*table_ptr };
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let entry = &table[index];
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frame = match entry.frame() {
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Ok(frame) => frame,
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Err(FrameError::FrameNotPresent) => return None,
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Err(FrameError::HugeFrame) => panic!["huge pages not supported"],
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};
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}
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Some(frame.start_address() + u64::from(addr.page_offset()))
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}
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pub unsafe fn translate_addr(addr: VirtAddr, physical_memory_offset: VirtAddr) -> Option<PhysAddr> {
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translate_addr_inner(addr, physical_memory_offset)
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}
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pub fn create_example_mapping(
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page: Page,
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mapper: &mut OffsetPageTable,
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frame_allocator: &mut impl FrameAllocator<Size4KiB>,
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) {
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use x86_64::structures::paging::PageTableFlags as Flags;
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let frame = PhysFrame::containing_address(PhysAddr::new(0xb8000));
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let flags = Flags::PRESENT | Flags::WRITABLE;
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let map_to_result = unsafe { mapper.map_to(page, frame, flags, frame_allocator) };
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map_to_result.expect("map_to failed").flush();
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}
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pub struct EmptyFrameAllocator;
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unsafe impl FrameAllocator<Size4KiB> for EmptyFrameAllocator {
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fn allocate_frame(&mut self) -> Option<PhysFrame<Size4KiB>> {
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None
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}
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}
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