Merge pull request #569 from phil-opp/post-10-new

Update post-10 branch for new "Paging Implementation" post

Cargo.lock

@@ -31,7 +31,7 @@ name = "blog_os"
 version = "0.1.0"
 dependencies = [
  "array-init 0.0.3 (registry+https://github.com/rust-lang/crates.io-index)",
- "bootloader 0.3.12 (registry+https://github.com/rust-lang/crates.io-index)",
+ "bootloader 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "lazy_static 1.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "pc-keyboard 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "pic8259_simple 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -43,13 +43,13 @@ dependencies = [
 
 [[package]]
 name = "bootloader"
-version = "0.3.12"
+version = "0.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "fixedvec 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "font8x8 0.2.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "usize_conversions 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "x86_64 0.2.14 (registry+https://github.com/rust-lang/crates.io-index)",
+ "x86_64 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "xmas-elf 0.6.2 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -297,6 +297,19 @@ dependencies = [
  "ux 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "x86_64"
+version = "0.3.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "array-init 0.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "bit_field 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "bitflags 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "os_bootinfo 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "usize_conversions 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "ux 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "x86_64"
 version = "0.5.2"
@@ -328,7 +341,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum array-init 0.0.4 (registry+https://github.com/rust-lang/crates.io-index)" = "23589ecb866b460d3a0f1278834750268c607e8e28a1b982c907219f3178cd72"
 "checksum bit_field 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)" = "ed8765909f9009617974ab6b7d332625b320b33c326b1e9321382ef1999b5d56"
 "checksum bitflags 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)" = "228047a76f468627ca71776ecdebd732a3423081fcf5125585bcd7c49886ce12"
-"checksum bootloader 0.3.12 (registry+https://github.com/rust-lang/crates.io-index)" = "2b498d7168288f3667f80aee93b4894e355dfce867803e1ccd5d9ee42a0b0e1a"
+"checksum bootloader 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "a0808c55da932b82d3ababdaa0caa3f18522c5d2d06309b98f73adda849a3f03"
 "checksum cc 1.0.30 (registry+https://github.com/rust-lang/crates.io-index)" = "d01c69d08ff207f231f07196e30f84c70f1c815b04f980f8b7b01ff01f05eb92"
 "checksum cpuio 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "22b8e308ccfc5acf3b82f79c0eac444cf6114cb2ac67a230ca6c177210068daa"
 "checksum fixedvec 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)" = "7c6c16d316ccdac21a4dd648e314e76facbbaf316e83ca137d0857a9c07419d0"
@@ -364,6 +377,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum winapi-i686-pc-windows-gnu 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "ac3b87c63620426dd9b991e5ce0329eff545bccbbb34f3be09ff6fb6ab51b7b6"
 "checksum winapi-x86_64-pc-windows-gnu 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "712e227841d057c1ee1cd2fb22fa7e5a5461ae8e48fa2ca79ec42cfc1931183f"
 "checksum x86_64 0.2.14 (registry+https://github.com/rust-lang/crates.io-index)" = "2bd647af1614659e1febec1d681231aea4ebda4818bf55a578aff02f3e4db4b4"
+"checksum x86_64 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)" = "f9258d7e2dd25008d69e8c9e9ee37865887a5e1e3d06a62f1cb3f6c209e6f177"
 "checksum x86_64 0.5.2 (registry+https://github.com/rust-lang/crates.io-index)" = "de155d368de1d32afc8f90838bf81986e4bd43a0cd5fcd7f7e9c85cb8f51dc7c"
 "checksum xmas-elf 0.6.2 (registry+https://github.com/rust-lang/crates.io-index)" = "22678df5df766e8d1e5d609da69f0c3132d794edf6ab5e75e7abcd2270d4cf58"
 "checksum zero 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)" = "5f1bc8a6b2005884962297587045002d8cfb8dcec9db332f4ca216ddc5de82c5"

Cargo.toml

@@ -5,7 +5,7 @@ authors = ["Philipp Oppermann <dev@phil-opp.com>"]
 edition = "2018"
 
 [dependencies]
-bootloader = "0.3.12"
+bootloader = { version = "0.4.0", features = ["map_physical_memory"]}
 volatile = "0.2.3"
 spin = "0.4.9"
 uart_16550 = "0.1.0"

README.md

@@ -1,10 +1,10 @@
-# Blog OS (Advanced Paging)
+# Blog OS (Paging Implementation)
 
 [![Build Status](https://travis-ci.org/phil-opp/blog_os.svg?branch=post-10)](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 [Paging Implementation][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-implementation/
 
 **Check out the [master branch](https://github.com/phil-opp/blog_os) for more information.**
 

src/main.rs

@@ -3,7 +3,7 @@
 #![cfg_attr(test, allow(unused_imports))]
 
 use blog_os::println;
-use bootloader::{bootinfo::BootInfo, entry_point};
+use bootloader::{entry_point, BootInfo};
 use core::panic::PanicInfo;
 
 entry_point!(kernel_main);
@@ -11,7 +11,8 @@ entry_point!(kernel_main);
 #[cfg(not(test))]
 fn kernel_main(boot_info: &'static BootInfo) -> ! {
     use blog_os::interrupts::PICS;
-    use blog_os::memory::{self, create_example_mapping};
+    use blog_os::memory;
+    use x86_64::{structures::paging::Page, VirtAddr};
 
     println!("Hello World{}", "!");
 
@@ -20,11 +21,16 @@ 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 mapper = unsafe { memory::init(boot_info.physical_memory_offset) };
     let mut frame_allocator = memory::init_frame_allocator(&boot_info.memory_map);
 
-    create_example_mapping(&mut recursive_page_table, &mut frame_allocator);
+    // map a previously unmapped page
-    unsafe { (0xdeadbeaf900 as *mut u64).write_volatile(0xf021f077f065f04e) };
+    let page = Page::containing_address(VirtAddr::new(0xdeadbeaf000));
+    memory::create_example_mapping(page, &mut mapper, &mut frame_allocator);
+
+    // write the string `New!` to the screen through the new mapping
+    let page_ptr: *mut u64 = page.start_address().as_mut_ptr();
+    unsafe { page_ptr.offset(400).write_volatile(0x_f021_f077_f065_f04e) };
 
     println!("It did not crash!");
     blog_os::hlt_loop();

src/memory.rs

@@ -1,24 +1,26 @@
 use bootloader::bootinfo::{MemoryMap, MemoryRegionType};
-use x86_64::structures::paging::{
+use x86_64::{
-    FrameAllocator, Mapper, Page, PageTable, PhysFrame, RecursivePageTable, Size4KiB,
+    structures::paging::{
+        FrameAllocator, MappedPageTable, Mapper, MapperAllSizes, Page, PageTable, PhysFrame,
+        Size4KiB,
+    },
+    PhysAddr, VirtAddr,
 };
-use x86_64::{PhysAddr, VirtAddr};
 
-/// Creates a RecursivePageTable instance from the level 4 address.
+/// Initialize a new MappedPageTable.
 ///
-/// This function is unsafe because it can break memory safety if an invalid
+/// This function is unsafe because the caller must guarantee that the
-/// address is passed.
+/// complete physical memory is mapped to virtual memory at the passed
-pub unsafe fn init(level_4_table_addr: usize) -> RecursivePageTable<'static> {
+/// `physical_memory_offset`. Also, this function must be only called once
-    /// Rust currently treats the whole body of unsafe functions as an unsafe
+/// to avoid aliasing `&mut` references (which is undefined behavior).
-    /// block, which makes it difficult to see which operations are unsafe. To
+pub unsafe fn init(physical_memory_offset: u64) -> impl MapperAllSizes {
-    /// limit the scope of unsafe we use a safe inner function.
+    let level_4_table = active_level_4_table(physical_memory_offset);
-    fn init_inner(level_4_table_addr: usize) -> RecursivePageTable<'static> {
+    let phys_to_virt = move |frame: PhysFrame| -> *mut PageTable {
-        let level_4_table_ptr = level_4_table_addr as *mut PageTable;
+        let phys = frame.start_address().as_u64();
-        let level_4_table = unsafe { &mut *level_4_table_ptr };
+        let virt = VirtAddr::new(phys + physical_memory_offset);
-        RecursivePageTable::new(level_4_table).unwrap()
+        virt.as_mut_ptr()
-    }
+    };
-
+    MappedPageTable::new(level_4_table, phys_to_virt)
-    init_inner(level_4_table_addr)
 }
 
 /// Create a FrameAllocator from the passed memory map
@@ -39,17 +41,36 @@ pub fn init_frame_allocator(
     BootInfoFrameAllocator { frames }
 }
 
+/// Returns a mutable reference to the active level 4 table.
+///
+/// This function is unsafe because the caller must guarantee that the
+/// complete physical memory is mapped to virtual memory at the passed
+/// `physical_memory_offset`. Also, this function must be only called once
+/// to avoid aliasing `&mut` references (which is undefined behavior).
+unsafe fn active_level_4_table(physical_memory_offset: u64) -> &'static mut PageTable {
+    use x86_64::{registers::control::Cr3, VirtAddr};
+
+    let (level_4_table_frame, _) = Cr3::read();
+
+    let phys = level_4_table_frame.start_address();
+    let virt = VirtAddr::new(phys.as_u64() + physical_memory_offset);
+    let page_table_ptr: *mut PageTable = virt.as_mut_ptr();
+
+    &mut *page_table_ptr // unsafe
+}
+
+/// Creates an example mapping for the given page to frame `0xb8000`.
 pub fn create_example_mapping(
-    recursive_page_table: &mut RecursivePageTable,
+    page: Page,
+    mapper: &mut impl Mapper<Size4KiB>,
     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) };
+    let map_to_result = unsafe { mapper.map_to(page, frame, flags, frame_allocator) };
     map_to_result.expect("map_to failed").flush();
 }