Reset code to post-09 branch for new 'Paging Implementation' post

README.md

@@ -1,10 +1,10 @@
-# Blog OS (Advanced Paging)
+# Blog OS (Introduction to Paging)
 
-[![Build Status](https://travis-ci.org/phil-opp/blog_os.svg?branch=post-10)](https://travis-ci.org/phil-opp/blog_os/branches)
+[![Build Status](https://travis-ci.org/phil-opp/blog_os.svg?branch=post-09)](https://travis-ci.org/phil-opp/blog_os/branches)
 
-This repository contains the source code for the [Advanced Paging][post] post of the [Writing an OS in Rust](https://os.phil-opp.com) series.
+This repository contains the source code for the [Introduction to Paging][post] post of the [Writing an OS in Rust](https://os.phil-opp.com) series.
 
-[post]: https://os.phil-opp.com/advanced-paging/
+[post]: https://os.phil-opp.com/paging-introduction/
 
 **Check out the [master branch](https://github.com/phil-opp/blog_os) for more information.**
 

src/lib.rs

@@ -3,7 +3,6 @@
 
 pub mod gdt;
 pub mod interrupts;
-pub mod memory;
 pub mod serial;
 pub mod vga_buffer;
 

src/main.rs

@@ -3,15 +3,13 @@
 #![cfg_attr(test, allow(unused_imports))]
 
 use blog_os::println;
-use bootloader::{bootinfo::BootInfo, entry_point};
 use core::panic::PanicInfo;
 
-entry_point!(kernel_main);
-
 #[cfg(not(test))]
-fn kernel_main(boot_info: &'static BootInfo) -> ! {
+#[no_mangle]
+pub extern "C" fn _start() -> ! {
     use blog_os::interrupts::PICS;
-    use blog_os::memory::{self, create_example_mapping};
+    use x86_64::registers::control::Cr3;
 
     println!("Hello World{}", "!");
 
@@ -20,11 +18,11 @@ fn kernel_main(boot_info: &'static BootInfo) -> ! {
     unsafe { PICS.lock().initialize() };
     x86_64::instructions::interrupts::enable();
 
-    let mut recursive_page_table = unsafe { memory::init(boot_info.p4_table_addr as usize) };
-    let mut frame_allocator = memory::init_frame_allocator(&boot_info.memory_map);
-
-    create_example_mapping(&mut recursive_page_table, &mut frame_allocator);
-    unsafe { (0xdeadbeaf900 as *mut u64).write_volatile(0xf021f077f065f04e) };
+    let (level_4_page_table, _) = Cr3::read();
+    println!(
+        "Level 4 page table at: {:?}",
+        level_4_page_table.start_address()
+    );
 
     println!("It did not crash!");
     blog_os::hlt_loop();

src/memory.rs

@@ -1,79 +0,0 @@
-use bootloader::bootinfo::{MemoryMap, MemoryRegionType};
-use x86_64::structures::paging::{
-    FrameAllocator, Mapper, Page, PageTable, PhysFrame, RecursivePageTable, Size4KiB,
-};
-use x86_64::{PhysAddr, VirtAddr};
-
-/// Creates a RecursivePageTable instance from the level 4 address.
-///
-/// This function is unsafe because it can break memory safety if an invalid
-/// address is passed.
-pub unsafe fn init(level_4_table_addr: usize) -> RecursivePageTable<'static> {
-    /// Rust currently treats the whole body of unsafe functions as an unsafe
-    /// block, which makes it difficult to see which operations are unsafe. To
-    /// limit the scope of unsafe we use a safe inner function.
-    fn init_inner(level_4_table_addr: usize) -> RecursivePageTable<'static> {
-        let level_4_table_ptr = level_4_table_addr as *mut PageTable;
-        let level_4_table = unsafe { &mut *level_4_table_ptr };
-        RecursivePageTable::new(level_4_table).unwrap()
-    }
-
-    init_inner(level_4_table_addr)
-}
-
-/// Create a FrameAllocator from the passed memory map
-pub fn init_frame_allocator(
-    memory_map: &'static MemoryMap,
-) -> BootInfoFrameAllocator<impl Iterator<Item = PhysFrame>> {
-    // get usable regions from memory map
-    let regions = memory_map
-        .iter()
-        .filter(|r| r.region_type == MemoryRegionType::Usable);
-    // map each region to its address range
-    let addr_ranges = regions.map(|r| r.range.start_addr()..r.range.end_addr());
-    // transform to an iterator of frame start addresses
-    let frame_addresses = addr_ranges.flat_map(|r| r.into_iter().step_by(4096));
-    // create `PhysFrame` types from the start addresses
-    let frames = frame_addresses.map(|addr| PhysFrame::containing_address(PhysAddr::new(addr)));
-
-    BootInfoFrameAllocator { frames }
-}
-
-pub fn create_example_mapping(
-    recursive_page_table: &mut RecursivePageTable,
-    frame_allocator: &mut impl FrameAllocator<Size4KiB>,
-) {
-    use x86_64::structures::paging::PageTableFlags as Flags;
-
-    let page: Page = Page::containing_address(VirtAddr::new(0xdeadbeaf000));
-    let frame = PhysFrame::containing_address(PhysAddr::new(0xb8000));
-    let flags = Flags::PRESENT | Flags::WRITABLE;
-
-    let map_to_result = unsafe { recursive_page_table.map_to(page, frame, flags, frame_allocator) };
-    map_to_result.expect("map_to failed").flush();
-}
-
-/// A FrameAllocator that always returns `None`.
-pub struct EmptyFrameAllocator;
-
-impl FrameAllocator<Size4KiB> for EmptyFrameAllocator {
-    fn allocate_frame(&mut self) -> Option<PhysFrame> {
-        None
-    }
-}
-
-pub struct BootInfoFrameAllocator<I>
-where
-    I: Iterator<Item = PhysFrame>,
-{
-    frames: I,
-}
-
-impl<I> FrameAllocator<Size4KiB> for BootInfoFrameAllocator<I>
-where
-    I: Iterator<Item = PhysFrame>,
-{
-    fn allocate_frame(&mut self) -> Option<PhysFrame> {
-        self.frames.next()
-    }
-}