Merge branch 'post-08' into post-09

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

Cargo.lock

@@ -4,15 +4,21 @@ version = 4
 
 [[package]]
 name = "bit_field"
-version = "0.10.1"
+version = "0.10.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "dcb6dd1c2376d2e096796e234a70e17e94cc2d5d54ff8ce42b28cef1d0d359a4"
+checksum = "dc827186963e592360843fb5ba4b973e145841266c1357f7180c43526f2e5b61"
 
 [[package]]
 name = "bitflags"
-version = "1.2.1"
+version = "1.3.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "cf1de2fe8c75bc145a2f577add951f8134889b4795d47466a54a5c846d691693"
+checksum = "bef38d45163c2f1dde094a7dfd33ccf595c92905c8f8f4fdc18d06fb1037718a"
+
+[[package]]
+name = "bitflags"
+version = "2.9.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6a65b545ab31d687cff52899d4890855fec459eb6afe0da6417b8a18da87aa29"
 
 [[package]]
 name = "blog_os"
@@ -22,7 +28,7 @@ dependencies = [
  "lazy_static",
  "pc-keyboard",
  "pic8259",
- "spin",
+ "spin 0.5.2",
  "uart_16550",
  "volatile 0.2.7",
  "x86_64",
@@ -30,17 +36,17 @@ dependencies = [
 
 [[package]]
 name = "bootloader"
-version = "0.9.31"
+version = "0.9.33"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "974e79cf1b0b737839f01330fb5393095daf1124d52693696494e32523ae9ef5"
+checksum = "7bdfddac270bbdd45903296bc1caf29a7fdce6b326aaf0bbab7f04c5f98b7447"
 
 [[package]]
 name = "lazy_static"
-version = "1.4.0"
+version = "1.5.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e2abad23fbc42b3700f2f279844dc832adb2b2eb069b2df918f455c4e18cc646"
+checksum = "bbd2bcb4c963f2ddae06a2efc7e9f3591312473c50c6685e1f298068316e66fe"
 dependencies = [
- "spin",
+ "spin 0.9.8",
 ]
 
 [[package]]
@@ -51,13 +57,19 @@ checksum = "ed089a1fbffe3337a1a345501c981f1eb1e47e69de5a40e852433e12953c3174"
 
 [[package]]
 name = "pic8259"
-version = "0.10.1"
+version = "0.10.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "08cc920d83ee33c0f9b73aa441e75468bf2d10c959a3eb6260cf720b05ac91a1"
+checksum = "cb844b5b01db1e0b17938685738f113bfc903846f18932b378bc0eabfa40e194"
 dependencies = [
  "x86_64",
 ]
 
+[[package]]
+name = "rustversion"
+version = "1.0.22"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b39cdef0fa800fc44525c84ccb54a029961a8215f9619753635a9c0d2538d46d"
+
 [[package]]
 name = "spin"
 version = "0.5.2"
@@ -65,12 +77,19 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6e63cff320ae2c57904679ba7cb63280a3dc4613885beafb148ee7bf9aa9042d"
 
 [[package]]
-name = "uart_16550"
-version = "0.2.14"
+name = "spin"
+version = "0.9.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "503a6c0e6d82daa87985e662d120c0176b09587c92a68db22781b28ae95405dd"
+checksum = "6980e8d7511241f8acf4aebddbb1ff938df5eebe98691418c4468d0b72a96a67"
+
+[[package]]
+name = "uart_16550"
+version = "0.2.19"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "614ff2a87880d4bd4374722268598a970bbad05ced8bf630439417347254ab2e"
 dependencies = [
- "bitflags",
+ "bitflags 1.3.2",
+ "rustversion",
  "x86_64",
 ]
 
@@ -82,17 +101,18 @@ checksum = "f6b06ad3ed06fef1713569d547cdbdb439eafed76341820fb0e0344f29a41945"
 
 [[package]]
 name = "volatile"
-version = "0.4.4"
+version = "0.4.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e4c2dbd44eb8b53973357e6e207e370f0c1059990df850aca1eca8947cf464f0"
+checksum = "442887c63f2c839b346c192d047a7c87e73d0689c9157b00b53dcc27dd5ea793"
 
 [[package]]
 name = "x86_64"
-version = "0.14.7"
+version = "0.14.13"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fb611915c917c6296d11e23f71ff1ecfe49c5766daba92cd3df52df6b58285b6"
+checksum = "c101112411baafbb4bf8d33e4c4a80ab5b02d74d2612331c61e8192fc9710491"
 dependencies = [
  "bit_field",
- "bitflags",
- "volatile 0.4.4",
+ "bitflags 2.9.2",
+ "rustversion",
+ "volatile 0.4.6",
 ]

Cargo.toml

@@ -13,7 +13,7 @@ name = "stack_overflow"
 harness = false
 
 [dependencies]
-bootloader = "0.9"
+bootloader = { version = "0.9", features = ["map_physical_memory"] }
 volatile = "0.2.6"
 spin = "0.5.2"
 x86_64 = "0.14.2"
@@ -25,10 +25,19 @@ pc-keyboard = "0.7.0"
 version = "1.0"
 features = ["spin_no_std"]
 
+[[bin]]
+name = "blog_os"
+test = true
+bench = false
+
 
 [package.metadata.bootimage]
 test-args = [
-    "-device", "isa-debug-exit,iobase=0xf4,iosize=0x04", "-serial", "stdio",
-    "-display", "none"
+    "-device",
+    "isa-debug-exit,iobase=0xf4,iosize=0x04",
+    "-serial",
+    "stdio",
+    "-display",
+    "none",
 ]
-test-success-exit-code = 33         # (0x10 << 1) | 1
+test-success-exit-code = 33 # (0x10 << 1) | 1

README.md

@@ -1,10 +1,10 @@
-# Blog OS (Introduction to Paging)
+# Blog OS (Paging Implementation)
 
-[![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)
+[![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)
 
-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.
+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/paging-introduction/
+[post]: https://os.phil-opp.com/paging-implementation/
 
 **Check out the [master branch](https://github.com/phil-opp/blog_os) for more information.**
 

src/lib.rs

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

src/main.rs

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

src/memory.rs

@@ -0,0 +1,106 @@
+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

@@ -3,8 +3,8 @@
     "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-c-int-width": "32",
+    "target-pointer-width": 64,
+    "target-c-int-width": 32,
     "os": "none",
     "executables": true,
     "linker-flavor": "ld.lld",