Remove paging testing code again

Cargo.toml

@@ -8,3 +8,8 @@ crate-type = ["staticlib"]
 
 [dependencies]
 rlibc = "1.0"
+volatile = "0.1.0"
+spin = "0.4.5"
+multiboot2 = "0.1.0"
+bitflags = "0.7.0"
+x86_64 = "0.1.2"

README.md

@@ -1,12 +1,12 @@
-# Blog OS (Set Up Rust)
-[![Build Status](https://travis-ci.org/phil-opp/blog_os.svg?branch=post_3)](https://travis-ci.org/phil-opp/blog_os/branches)
+# Blog OS (Page Tables)
+[![Build Status](https://travis-ci.org/phil-opp/blog_os.svg?branch=post_6)](https://travis-ci.org/phil-opp/blog_os/branches)
 
-This repository contains the source code for the [Set Up Rust](http://os.phil-opp.com/set-up-rust.html) post of the [Writing an OS in Rust](http://os.phil-opp.com) series.
+This repository contains the source code for the [Page Tables](http://os.phil-opp.com/modifying-page-tables.html) post of the [Writing an OS in Rust](http://os.phil-opp.com) series.
 
 **Check out the [master branch](https://github.com/phil-opp/blog_os) for more information.**
 
 ## Building
-You need to have `nasm`, `grub-mkrescue`, `xorriso`, `qemu`, and a nigthly Rust compiler installed. Then you can run it using `make run`.
+You need to have `nasm`, `grub-mkrescue`, `xorriso`, `qemu`, and a nightly Rust compiler installed. Then you can run it using `make run`.
 
 Please file an issue if you have any problems.
 

src/arch/x86_64/boot.asm

@@ -5,6 +5,7 @@ section .text
 bits 32
 start:
     mov esp, stack_top
+    mov edi, ebx       ; move Multiboot info pointer to edi
 
     call check_multiboot
     call check_cpuid
@@ -84,6 +85,11 @@ check_long_mode:
     jmp error
 
 set_up_page_tables:
+    ; map P4 table recursively
+    mov eax, p4_table
+    or eax, 0b11 ; present + writable
+    mov [p4_table + 511 * 8], eax
+
     ; map first P4 entry to P3 table
     mov eax, p3_table
     or eax, 0b11 ; present + writable
@@ -151,7 +157,7 @@ p3_table:
 p2_table:
     resb 4096
 stack_bottom:
-    resb 64
+    resb 4096 * 4
 stack_top:
 
 section .rodata

src/arch/x86_64/linker.ld

@@ -11,6 +11,14 @@ SECTIONS {
 
     .text :
     {
-        *(.text)
+        *(.text .text.*)
+    }
+
+    .rodata : {
+        *(.rodata .rodata.*)
+    }
+
+    .data.rel.ro : {
+        *(.data.rel.ro.local*) *(.data.rel.ro .data.rel.ro.*)
     }
 }

src/lib.rs

@@ -1,26 +1,67 @@
 #![feature(lang_items)]
+#![feature(const_fn)]
+#![feature(const_unique_new)]
+#![feature(unique)]
 #![no_std]
 
 extern crate rlibc;
+extern crate volatile;
+extern crate spin;
+extern crate multiboot2;
+#[macro_use]
+extern crate bitflags;
+extern crate x86_64;
+
+#[macro_use]
+mod vga_buffer;
+mod memory;
 
 #[no_mangle]
-pub extern fn rust_main() {
-    // ATTENTION: we have a very small stack and no guard page
+pub extern fn rust_main(multiboot_information_address: usize) {
+    use memory::FrameAllocator;
 
-    let hello = b"Hello World!";
-    let color_byte = 0x1f; // white foreground, blue background
+    vga_buffer::clear_screen();
+    println!("Hello World{}", "!");
 
-    let mut hello_colored = [color_byte; 24];
-    for (i, char_byte) in hello.into_iter().enumerate() {
-        hello_colored[i*2] = *char_byte;
+    let boot_info = unsafe{ multiboot2::load(multiboot_information_address) };
+    let memory_map_tag = boot_info.memory_map_tag()
+        .expect("Memory map tag required");
+
+    println!("memory areas:");
+    for area in memory_map_tag.memory_areas() {
+        println!("    start: 0x{:x}, length: 0x{:x}",
+            area.base_addr, area.length);
     }
 
-    // write `Hello World!` to the center of the VGA text buffer
-    let buffer_ptr = (0xb8000 + 1988) as *mut _;
-    unsafe { *buffer_ptr = hello_colored };
+    let elf_sections_tag = boot_info.elf_sections_tag()
+        .expect("Elf-sections tag required");
+
+    println!("kernel sections:");
+    for section in elf_sections_tag.sections() {
+        println!("    addr: 0x{:x}, size: 0x{:x}, flags: 0x{:x}",
+            section.addr, section.size, section.flags);
+    }
+
+    let kernel_start = elf_sections_tag.sections().map(|s| s.addr)
+        .min().unwrap();
+    let kernel_end = elf_sections_tag.sections().map(|s| s.addr + s.size)
+        .max().unwrap();
+    let multiboot_start = multiboot_information_address;
+    let multiboot_end = multiboot_start + (boot_info.total_size as usize);
+
+    let mut frame_allocator = memory::AreaFrameAllocator::new(
+        kernel_start as usize, kernel_end as usize, multiboot_start,
+        multiboot_end, memory_map_tag.memory_areas());
 
     loop{}
 }
 
 #[lang = "eh_personality"] extern fn eh_personality() {}
-#[lang = "panic_fmt"] #[no_mangle] pub extern fn panic_fmt() -> ! {loop{}}
+
+#[lang = "panic_fmt"]
+#[no_mangle]
+pub extern fn panic_fmt(fmt: core::fmt::Arguments, file: &'static str, line: u32) -> ! {
+    println!("\n\nPANIC in {} at line {}:", file, line);
+    println!("    {}", fmt);
+    loop{}
+}

src/memory/area_frame_allocator.rs

@@ -0,0 +1,88 @@
+use memory::{Frame, FrameAllocator};
+use multiboot2::{MemoryAreaIter, MemoryArea};
+
+pub struct AreaFrameAllocator {
+    next_free_frame: Frame,
+    current_area: Option<&'static MemoryArea>,
+    areas: MemoryAreaIter,
+    kernel_start: Frame,
+    kernel_end: Frame,
+    multiboot_start: Frame,
+    multiboot_end: Frame,
+}
+
+impl FrameAllocator for AreaFrameAllocator {
+    fn allocate_frame(&mut self) -> Option<Frame> {
+        if let Some(area) = self.current_area {
+            // "Clone" the frame to return it if it's free. Frame doesn't
+            // implement Clone, but we can construct an identical frame.
+            let frame = Frame{ number: self.next_free_frame.number };
+
+            // the last frame of the current area
+            let current_area_last_frame = {
+                let address = area.base_addr + area.length - 1;
+                Frame::containing_address(address as usize)
+            };
+
+            if frame > current_area_last_frame {
+                // all frames of current area are used, switch to next area
+                self.choose_next_area();
+            } else if frame >= self.kernel_start && frame <= self.kernel_end {
+                // `frame` is used by the kernel
+                self.next_free_frame = Frame {
+                    number: self.kernel_end.number + 1
+                };
+            } else if frame >= self.multiboot_start && frame <= self.multiboot_end {
+                // `frame` is used by the multiboot information structure
+                self.next_free_frame = Frame {
+                    number: self.multiboot_end.number + 1
+                };
+            } else {
+                // frame is unused, increment `next_free_frame` and return it
+                self.next_free_frame.number += 1;
+                return Some(frame);
+            }
+            // `frame` was not valid, try it again with the updated `next_free_frame`
+            self.allocate_frame()
+        } else {
+            None // no free frames left
+        }
+    }
+
+    fn deallocate_frame(&mut self, _frame: Frame) {
+        unimplemented!()
+    }
+}
+
+impl AreaFrameAllocator {
+    pub fn new(kernel_start: usize, kernel_end: usize,
+        multiboot_start: usize, multiboot_end: usize,
+        memory_areas: MemoryAreaIter) -> AreaFrameAllocator
+    {
+        let mut allocator = AreaFrameAllocator {
+            next_free_frame: Frame::containing_address(0),
+            current_area: None,
+            areas: memory_areas,
+            kernel_start: Frame::containing_address(kernel_start),
+            kernel_end: Frame::containing_address(kernel_end),
+            multiboot_start: Frame::containing_address(multiboot_start),
+            multiboot_end: Frame::containing_address(multiboot_end),
+        };
+        allocator.choose_next_area();
+        allocator
+    }
+
+    fn choose_next_area(&mut self) {
+        self.current_area = self.areas.clone().filter(|area| {
+            let address = area.base_addr + area.length - 1;
+            Frame::containing_address(address as usize) >= self.next_free_frame
+        }).min_by_key(|area| area.base_addr);
+
+        if let Some(area) = self.current_area {
+            let start_frame = Frame::containing_address(area.base_addr as usize);
+            if self.next_free_frame < start_frame {
+                self.next_free_frame = start_frame;
+            }
+        }
+    }
+}

src/memory/mod.rs

@@ -0,0 +1,27 @@
+pub use self::area_frame_allocator::AreaFrameAllocator;
+use self::paging::PhysicalAddress;
+
+mod area_frame_allocator;
+mod paging;
+
+pub const PAGE_SIZE: usize = 4096;
+
+#[derive(Debug, PartialEq, Eq, PartialOrd, Ord)]
+pub struct Frame {
+    number: usize,
+}
+
+impl Frame {
+    fn containing_address(address: usize) -> Frame {
+        Frame{ number: address / PAGE_SIZE }
+    }
+
+    fn start_address(&self) -> PhysicalAddress {
+        self.number * PAGE_SIZE
+    }
+}
+
+pub trait FrameAllocator {
+    fn allocate_frame(&mut self) -> Option<Frame>;
+    fn deallocate_frame(&mut self, frame: Frame);
+}

src/memory/paging/entry.rs

@@ -0,0 +1,47 @@
+use memory::Frame;
+
+pub struct Entry(u64);
+
+impl Entry {
+    pub fn is_unused(&self) -> bool {
+        self.0 == 0
+    }
+
+    pub fn set_unused(&mut self) {
+        self.0 = 0;
+    }
+
+    pub fn flags(&self) -> EntryFlags {
+        EntryFlags::from_bits_truncate(self.0)
+    }
+
+    pub fn pointed_frame(&self) -> Option<Frame> {
+        if self.flags().contains(PRESENT) {
+            Some(Frame::containing_address(
+                self.0 as usize & 0x000fffff_fffff000
+            ))
+        } else {
+            None
+        }
+    }
+
+    pub fn set(&mut self, frame: Frame, flags: EntryFlags) {
+        assert!(frame.start_address() & !0x000fffff_fffff000 == 0);
+        self.0 = (frame.start_address() as u64) | flags.bits();
+    }
+}
+
+bitflags! {
+    pub flags EntryFlags: u64 {
+        const PRESENT =         1 << 0,
+        const WRITABLE =        1 << 1,
+        const USER_ACCESSIBLE = 1 << 2,
+        const WRITE_THROUGH =   1 << 3,
+        const NO_CACHE =        1 << 4,
+        const ACCESSED =        1 << 5,
+        const DIRTY =           1 << 6,
+        const HUGE_PAGE =       1 << 7,
+        const GLOBAL =          1 << 8,
+        const NO_EXECUTE =      1 << 63,
+    }
+}

src/memory/paging/mod.rs

@@ -0,0 +1,157 @@
+pub use self::entry::*;
+use core::ptr::Unique;
+use memory::{PAGE_SIZE, Frame, FrameAllocator};
+use self::table::{Table, Level4};
+
+mod entry;
+mod table;
+
+const ENTRY_COUNT: usize = 512;
+
+pub type PhysicalAddress = usize;
+pub type VirtualAddress = usize;
+
+pub struct Page {
+   number: usize,
+}
+
+impl Page {
+    pub fn containing_address(address: VirtualAddress) -> Page {
+        assert!(address < 0x0000_8000_0000_0000 ||
+            address >= 0xffff_8000_0000_0000,
+            "invalid address: 0x{:x}", address);
+        Page { number: address / PAGE_SIZE }
+    }
+
+    fn start_address(&self) -> usize {
+        self.number * PAGE_SIZE
+    }
+
+    fn p4_index(&self) -> usize {
+        (self.number >> 27) & 0o777
+    }
+    fn p3_index(&self) -> usize {
+        (self.number >> 18) & 0o777
+    }
+    fn p2_index(&self) -> usize {
+        (self.number >> 9) & 0o777
+    }
+    fn p1_index(&self) -> usize {
+        (self.number >> 0) & 0o777
+    }
+}
+
+pub struct ActivePageTable {
+    p4: Unique<Table<Level4>>,
+}
+
+impl ActivePageTable {
+    pub unsafe fn new() -> ActivePageTable {
+        ActivePageTable {
+            p4: Unique::new_unchecked(table::P4),
+        }
+    }
+
+    fn p4(&self) -> &Table<Level4> {
+        unsafe { self.p4.as_ref() }
+    }
+
+    fn p4_mut(&mut self) -> &mut Table<Level4> {
+        unsafe { self.p4.as_mut() }
+    }
+
+    pub fn translate(&self, virtual_address: VirtualAddress) -> Option<PhysicalAddress> {
+        let offset = virtual_address % PAGE_SIZE;
+        self.translate_page(Page::containing_address(virtual_address))
+            .map(|frame| frame.number * PAGE_SIZE + offset)
+    }
+
+    fn translate_page(&self, page: Page) -> Option<Frame> {
+        use self::entry::HUGE_PAGE;
+
+        let p3 = self.p4().next_table(page.p4_index());
+
+        let huge_page = || {
+            p3.and_then(|p3| {
+                let p3_entry = &p3[page.p3_index()];
+                // 1GiB page?
+                if let Some(start_frame) = p3_entry.pointed_frame() {
+                    if p3_entry.flags().contains(HUGE_PAGE) {
+                        // address must be 1GiB aligned
+                        assert!(start_frame.number % (ENTRY_COUNT * ENTRY_COUNT) == 0);
+                        return Some(Frame {
+                            number: start_frame.number + page.p2_index() *
+                                    ENTRY_COUNT + page.p1_index(),
+                        });
+                    }
+                }
+                if let Some(p2) = p3.next_table(page.p3_index()) {
+                    let p2_entry = &p2[page.p2_index()];
+                    // 2MiB page?
+                    if let Some(start_frame) = p2_entry.pointed_frame() {
+                        if p2_entry.flags().contains(HUGE_PAGE) {
+                            // address must be 2MiB aligned
+                            assert!(start_frame.number % ENTRY_COUNT == 0);
+                            return Some(Frame {
+                                number: start_frame.number + page.p1_index()
+                            });
+                        }
+                    }
+                }
+                None
+            })
+        };
+
+        p3.and_then(|p3| p3.next_table(page.p3_index()))
+        .and_then(|p2| p2.next_table(page.p2_index()))
+        .and_then(|p1| p1[page.p1_index()].pointed_frame())
+        .or_else(huge_page)
+    }
+
+    pub fn map_to<A>(&mut self, page: Page, frame: Frame, flags: EntryFlags,
+                    allocator: &mut A)
+        where A: FrameAllocator
+    {
+        let p4 = self.p4_mut();
+        let mut p3 = p4.next_table_create(page.p4_index(), allocator);
+        let mut p2 = p3.next_table_create(page.p3_index(), allocator);
+        let mut p1 = p2.next_table_create(page.p2_index(), allocator);
+
+        assert!(p1[page.p1_index()].is_unused());
+        p1[page.p1_index()].set(frame, flags | PRESENT);
+    }
+
+    pub fn map<A>(&mut self, page: Page, flags: EntryFlags, allocator: &mut A)
+        where A: FrameAllocator
+    {
+        let frame = allocator.allocate_frame().expect("out of memory");
+        self.map_to(page, frame, flags, allocator)
+    }
+
+    pub fn identity_map<A>(&mut self, frame: Frame, flags: EntryFlags, allocator: &mut A)
+        where A: FrameAllocator
+    {
+        let page = Page::containing_address(frame.start_address());
+        self.map_to(page, frame, flags, allocator)
+    }
+
+    fn unmap<A>(&mut self, page: Page, allocator: &mut A)
+        where A: FrameAllocator
+    {
+        use x86_64::instructions::tlb;
+        use x86_64::VirtualAddress;
+
+        assert!(self.translate(page.start_address()).is_some());
+
+        let p1 = self.p4_mut()
+                    .next_table_mut(page.p4_index())
+                    .and_then(|p3| p3.next_table_mut(page.p3_index()))
+                    .and_then(|p2| p2.next_table_mut(page.p2_index()))
+                    .expect("mapping code does not support huge pages");
+        let frame = p1[page.p1_index()].pointed_frame().unwrap();
+        p1[page.p1_index()].set_unused();
+        tlb::flush(VirtualAddress(page.start_address()));
+        // TODO free p(1,2,3) table if empty
+        //allocator.deallocate_frame(frame);
+    }
+}

src/memory/paging/table.rs

@@ -0,0 +1,100 @@
+use core::marker::PhantomData;
+use core::ops::{Index, IndexMut};
+use memory::FrameAllocator;
+use memory::paging::entry::*;
+use memory::paging::ENTRY_COUNT;
+
+pub const P4: *mut Table<Level4> = 0xffffffff_fffff000 as *mut _;
+
+pub struct Table<L: TableLevel> {
+    entries: [Entry; ENTRY_COUNT],
+    level: PhantomData<L>,
+}
+
+impl<L> Table<L> where L: TableLevel {
+    pub fn zero(&mut self) {
+        for entry in self.entries.iter_mut() {
+            entry.set_unused();
+        }
+    }
+}
+
+impl<L> Table<L> where L: HierarchicalLevel {
+    fn next_table_address(&self, index: usize) -> Option<usize> {
+        let entry_flags = self[index].flags();
+        if entry_flags.contains(PRESENT) && !entry_flags.contains(HUGE_PAGE) {
+            let table_address = self as *const _ as usize;
+            Some((table_address << 9) | (index << 12))
+        } else {
+            None
+        }
+    }
+
+    pub fn next_table(&self, index: usize) -> Option<&Table<L::NextLevel>> {
+        self.next_table_address(index)
+            .map(|address| unsafe { &*(address as *const _) })
+    }
+
+    pub fn next_table_mut(&mut self, index: usize) -> Option<&mut Table<L::NextLevel>> {
+        self.next_table_address(index)
+            .map(|address| unsafe { &mut *(address as *mut _) })
+    }
+
+    pub fn next_table_create<A>(&mut self,
+                                index: usize,
+                                allocator: &mut A)
+                                -> &mut Table<L::NextLevel>
+        where A: FrameAllocator
+    {
+        if self.next_table(index).is_none() {
+            assert!(!self.entries[index].flags().contains(HUGE_PAGE),
+                    "mapping code does not support huge pages");
+            let frame = allocator.allocate_frame().expect("no frames available");
+            self.entries[index].set(frame, PRESENT | WRITABLE);
+            self.next_table_mut(index).unwrap().zero();
+        }
+        self.next_table_mut(index).unwrap()
+    }
+}
+
+impl<L> Index<usize> for Table<L> where L: TableLevel {
+    type Output = Entry;
+
+    fn index(&self, index: usize) -> &Entry {
+        &self.entries[index]
+    }
+}
+
+impl<L> IndexMut<usize> for Table<L> where L: TableLevel {
+    fn index_mut(&mut self, index: usize) -> &mut Entry {
+        &mut self.entries[index]
+    }
+}
+
+pub trait TableLevel {}
+
+pub enum Level4 {}
+pub enum Level3 {}
+pub enum Level2 {}
+pub enum Level1 {}
+
+impl TableLevel for Level4 {}
+impl TableLevel for Level3 {}
+impl TableLevel for Level2 {}
+impl TableLevel for Level1 {}
+
+pub trait HierarchicalLevel: TableLevel {
+    type NextLevel: TableLevel;
+}
+
+impl HierarchicalLevel for Level4 {
+    type NextLevel = Level3;
+}
+
+impl HierarchicalLevel for Level3 {
+    type NextLevel = Level2;
+}
+
+impl HierarchicalLevel for Level2 {
+    type NextLevel = Level1;
+}

src/vga_buffer.rs

@@ -0,0 +1,147 @@
+use core::fmt;
+use core::ptr::Unique;
+use spin::Mutex;
+use volatile::Volatile;
+
+pub static WRITER: Mutex<Writer> = Mutex::new(Writer {
+    column_position: 0,
+    color_code: ColorCode::new(Color::LightGreen, Color::Black),
+    buffer: unsafe { Unique::new_unchecked(0xb8000 as *mut _) },
+});
+
+#[allow(dead_code)]
+#[derive(Debug, Clone, Copy)]
+#[repr(u8)]
+pub enum Color {
+    Black      = 0,
+    Blue       = 1,
+    Green      = 2,
+    Cyan       = 3,
+    Red        = 4,
+    Magenta    = 5,
+    Brown      = 6,
+    LightGray  = 7,
+    DarkGray   = 8,
+    LightBlue  = 9,
+    LightGreen = 10,
+    LightCyan  = 11,
+    LightRed   = 12,
+    Pink       = 13,
+    Yellow     = 14,
+    White      = 15,
+}
+
+#[derive(Debug, Clone, Copy)]
+struct ColorCode(u8);
+
+impl ColorCode {
+    const fn new(foreground: Color, background: Color) -> ColorCode {
+        ColorCode((background as u8) << 4 | (foreground as u8))
+    }
+}
+
+#[derive(Debug, Clone, Copy)]
+#[repr(C)]
+struct ScreenChar {
+    ascii_character: u8,
+    color_code: ColorCode,
+}
+
+const BUFFER_HEIGHT: usize = 25;
+const BUFFER_WIDTH: usize = 80;
+
+struct Buffer {
+    chars: [[Volatile<ScreenChar>; BUFFER_WIDTH]; BUFFER_HEIGHT],
+}
+
+pub struct Writer {
+    column_position: usize,
+    color_code: ColorCode,
+    buffer: Unique<Buffer>,
+}
+
+impl Writer {
+    pub fn write_byte(&mut self, byte: u8) {
+        match byte {
+            b'\n' => self.new_line(),
+            byte => {
+                if self.column_position >= BUFFER_WIDTH {
+                    self.new_line();
+                }
+
+                let row = BUFFER_HEIGHT - 1;
+                let col = self.column_position;
+
+                let color_code = self.color_code;
+                self.buffer().chars[row][col].write(ScreenChar {
+                    ascii_character: byte,
+                    color_code: color_code,
+                });
+                self.column_position += 1;
+            }
+        }
+    }
+
+    pub fn write_str(&mut self, s: &str) {
+        for byte in s.bytes() {
+        self.write_byte(byte)
+        }
+    }
+
+    fn buffer(&mut self) -> &mut Buffer {
+        unsafe{ self.buffer.as_mut() }
+    }
+
+    fn new_line(&mut self) {
+        for row in 1..BUFFER_HEIGHT {
+            for col in 0..BUFFER_WIDTH {
+                let buffer = self.buffer();
+                let character = buffer.chars[row][col].read();
+                buffer.chars[row - 1][col].write(character);
+            }
+        }
+        self.clear_row(BUFFER_HEIGHT-1);
+        self.column_position = 0;
+    }
+
+    fn clear_row(&mut self, row: usize) {
+        let blank = ScreenChar {
+            ascii_character: b' ',
+            color_code: self.color_code,
+        };
+        for col in 0..BUFFER_WIDTH {
+            self.buffer().chars[row][col].write(blank);
+        }
+    }
+}
+
+impl fmt::Write for Writer {
+    fn write_str(&mut self, s: &str) -> fmt::Result {
+        for byte in s.bytes() {
+          self.write_byte(byte)
+        }
+        Ok(())
+    }
+}
+
+macro_rules! print {
+    ($($arg:tt)*) => ({
+        $crate::vga_buffer::print(format_args!($($arg)*));
+    });
+}
+
+macro_rules! println {
+    ($fmt:expr) => (print!(concat!($fmt, "\n")));
+    ($fmt:expr, $($arg:tt)*) => (print!(concat!($fmt, "\n"), $($arg)*));
+}
+
+pub fn print(args: fmt::Arguments) {
+    use core::fmt::Write;
+    WRITER.lock().write_fmt(args).unwrap();
+}
+
+pub fn clear_screen() {
+    for _ in 0..BUFFER_HEIGHT {
+        println!("");
+    }
+}