Merge branch 'post-07' into post-08

Fix: `target-pointer-width` field now expects an integer

Cargo.lock

@@ -36,9 +36,9 @@ dependencies = [
 
 [[package]]
 name = "bootloader"
-version = "0.9.32"
+version = "0.9.33"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1ea119c3ed05625c179e09d17d0914570a3753ca09c890a73d98f6b72aea00d2"
+checksum = "7bdfddac270bbdd45903296bc1caf29a7fdce6b326aaf0bbab7f04c5f98b7447"
 
 [[package]]
 name = "lazy_static"

Cargo.toml

@@ -13,7 +13,7 @@ name = "stack_overflow"
 harness = false
 
 [dependencies]
-bootloader = { version = "0.9", features = ["map_physical_memory"] }
+bootloader = "0.9"
 volatile = "0.2.6"
 spin = "0.5.2"
 x86_64 = "0.14.2"

README.md

@@ -1,10 +1,10 @@
-# Blog OS (Paging Implementation)
+# Blog OS (Introduction to Paging)
 
-[![Build Status](https://github.com/phil-opp/blog_os/workflows/Code/badge.svg?branch=post-09)](https://github.com/phil-opp/blog_os/actions?query=workflow%3A%22Code%22+branch%3Apost-09)
+[![Build Status](https://github.com/phil-opp/blog_os/workflows/Code/badge.svg?branch=post-08)](https://github.com/phil-opp/blog_os/actions?query=workflow%3A%22Code%22+branch%3Apost-08)
 
-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.
+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/paging-implementation/
+[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

@@ -9,7 +9,6 @@ use core::panic::PanicInfo;
 
 pub mod gdt;
 pub mod interrupts;
-pub mod memory;
 pub mod serial;
 pub mod vga_buffer;
 
@@ -71,15 +70,10 @@ pub fn hlt_loop() -> ! {
     }
 }
 
-#[cfg(test)]
-use bootloader::{BootInfo, entry_point};
-
-#[cfg(test)]
-entry_point!(test_kernel_main);
-
 /// Entry point for `cargo xtest`
 #[cfg(test)]
-fn test_kernel_main(_boot_info: &'static BootInfo) -> ! {
+#[unsafe(no_mangle)]
+pub extern "C" fn _start() -> ! {
     init();
     test_main();
     hlt_loop();

src/main.rs

@@ -5,29 +5,20 @@
 #![reexport_test_harness_main = "test_main"]
 
 use blog_os::println;
-use bootloader::{BootInfo, entry_point};
 use core::panic::PanicInfo;
 
-entry_point!(kernel_main);
-
-fn kernel_main(boot_info: &'static BootInfo) -> ! {
-    use blog_os::memory::{self, BootInfoFrameAllocator};
-    use x86_64::{VirtAddr, structures::paging::Page};
-
+#[unsafe(no_mangle)]
+pub extern "C" fn _start() -> ! {
+    use x86_64::registers::control::Cr3;
     println!("Hello World{}", "!");
+
     blog_os::init();
 
-    let phys_mem_offset = VirtAddr::new(boot_info.physical_memory_offset);
-    let mut mapper = unsafe { memory::init(phys_mem_offset) };
-    let mut frame_allocator = unsafe { BootInfoFrameAllocator::init(&boot_info.memory_map) };
-
-    // map an unused page
-    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) };
+    let (level_4_page_table, _) = Cr3::read();
+    println!(
+        "Level 4 page table at: {:?}",
+        level_4_page_table.start_address()
+    );
 
     #[cfg(test)]
     test_main();

src/memory.rs

@@ -1,106 +0,0 @@
-use bootloader::bootinfo::{MemoryMap, MemoryRegionType};
-use x86_64::{
-    PhysAddr, VirtAddr,
-    structures::paging::{
-        FrameAllocator, Mapper, OffsetPageTable, Page, PageTable, PhysFrame, Size4KiB,
-    },
-};
-
-/// Initialize a new OffsetPageTable.
-///
-/// 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).
-pub unsafe fn init(physical_memory_offset: VirtAddr) -> OffsetPageTable<'static> {
-    unsafe {
-        let level_4_table = active_level_4_table(physical_memory_offset);
-        OffsetPageTable::new(level_4_table, physical_memory_offset)
-    }
-}
-
-/// 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: 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();
-
-    unsafe { &mut *page_table_ptr }
-}
-
-/// Creates an example mapping for the given page to frame `0xb8000`.
-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 {
-        // FIXME: this is not safe, we do it only for testing
-        mapper.map_to(page, frame, flags, frame_allocator)
-    };
-    map_to_result.expect("map_to failed").flush();
-}
-
-/// A FrameAllocator that always returns `None`.
-pub struct EmptyFrameAllocator;
-
-unsafe impl FrameAllocator<Size4KiB> for EmptyFrameAllocator {
-    fn allocate_frame(&mut self) -> Option<PhysFrame> {
-        None
-    }
-}
-
-/// A FrameAllocator that returns usable frames from the bootloader's memory map.
-pub struct BootInfoFrameAllocator {
-    memory_map: &'static MemoryMap,
-    next: usize,
-}
-
-impl BootInfoFrameAllocator {
-    /// Create a FrameAllocator from the passed memory map.
-    ///
-    /// This function is unsafe because the caller must guarantee that the passed
-    /// memory map is valid. The main requirement is that all frames that are marked
-    /// as `USABLE` in it are really unused.
-    pub unsafe fn init(memory_map: &'static MemoryMap) -> Self {
-        BootInfoFrameAllocator {
-            memory_map,
-            next: 0,
-        }
-    }
-
-    /// Returns an iterator over the usable frames specified in the memory map.
-    fn usable_frames(&self) -> impl Iterator<Item = PhysFrame> {
-        // get usable regions from memory map
-        let regions = self.memory_map.iter();
-        let usable_regions = regions.filter(|r| r.region_type == MemoryRegionType::Usable);
-        // map each region to its address range
-        let addr_ranges = usable_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.step_by(4096));
-        // create `PhysFrame` types from the start addresses
-        frame_addresses.map(|addr| PhysFrame::containing_address(PhysAddr::new(addr)))
-    }
-}
-
-unsafe impl FrameAllocator<Size4KiB> for BootInfoFrameAllocator {
-    fn allocate_frame(&mut self) -> Option<PhysFrame> {
-        let frame = self.usable_frames().nth(self.next);
-        self.next += 1;
-        frame
-    }
-}

x86_64-blog_os.json

@@ -3,7 +3,7 @@
     "data-layout": "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128",
     "arch": "x86_64",
     "target-endian": "little",
-    "target-pointer-width": "64",
+    "target-pointer-width": 64,
     "target-c-int-width": 32,
     "os": "none",
     "executables": true,