post-09

Cargo.toml

@@ -7,7 +7,7 @@ edition = "2018"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
-bootloader = "0.8.1"
+bootloader = { version = "0.8.1", features = ["map_physical_memory"]}
 pc-keyboard = "0.3.1"
 pic8259_simple = "0.1.1"
 spin = "0.5.2"

src/gdt.rs

@@ -1,7 +1,7 @@
 use lazy_static::lazy_static;
-use x86_64::VirtAddr;
-use x86_64::structures::gdt::{GlobalDescriptorTable, Descriptor, SegmentSelector};
+use x86_64::structures::gdt::{Descriptor, GlobalDescriptorTable, SegmentSelector};
 use x86_64::structures::tss::TaskStateSegment;
+use x86_64::VirtAddr;
 
 pub const DOUBLE_FAULT_IST_INDEX: u16 = 0;
 
@@ -25,7 +25,13 @@ lazy_static!{
         let mut gdt = GlobalDescriptorTable::new();
         let code_selector = gdt.add_entry(Descriptor::kernel_code_segment());
         let tss_selector = gdt.add_entry(Descriptor::tss_segment(&TSS));
-        (gdt, Selectors { code_selector, tss_selector })
+        (
+            gdt,
+            Selectors {
+                code_selector,
+                tss_selector,
+            },
+        )
     };
 }
 

src/interrupts.rs

@@ -1,7 +1,7 @@
 use lazy_static::lazy_static;
 use pic8259_simple::ChainedPics;
 use spin;
-use x86_64::structures::idt::{InterruptDescriptorTable, InterruptStackFrame};
+use x86_64::structures::idt::{InterruptDescriptorTable, InterruptStackFrame, PageFaultErrorCode};
 
 use crate::gdt;
 use crate::hlt_loop;
@@ -15,13 +15,14 @@ lazy_static!{
         let mut idt = InterruptDescriptorTable::new();
         idt.breakpoint.set_handler_fn(breakpoint_handler);
         unsafe {
-            idt.double_fault.set_handler_fn(double_fault_handler)
+            idt.double_fault
+                .set_handler_fn(double_fault_handler)
                 .set_stack_index(gdt::DOUBLE_FAULT_IST_INDEX);
         }
-        idt[InterruptIndex::Timer.as_usize()]
-            .set_handler_fn(timer_interrupt_handler);
-        idt[InterruptIndex::Keyboard.as_usize()]
-            .set_handler_fn(keyboard_interrupt_handler);
+        idt[InterruptIndex::Timer.as_usize()].set_handler_fn(timer_interrupt_handler);
+        idt[InterruptIndex::Keyboard.as_usize()].set_handler_fn(keyboard_interrupt_handler);
+
+        idt.page_fault.set_handler_fn(page_fault_handler);
 
         idt
     };
@@ -31,40 +32,37 @@ pub fn init_idt() {
     IDT.load();
 }
 
-extern "x86-interrupt" fn breakpoint_handler(
-    stack_frame: &mut InterruptStackFrame
-) {
+extern "x86-interrupt" fn breakpoint_handler(stack_frame: &mut InterruptStackFrame) {
     println!("EXCEPTION: BREAKPOINT\n{:#?}", stack_frame);
 }
 
 extern "x86-interrupt" fn double_fault_handler(
-    stack_frame: &mut InterruptStackFrame, _error_code: u64
+    stack_frame: &mut InterruptStackFrame,
+    _error_code: u64,
 ) {
     println!("EXCEPTION: DOUBLE FAULT\n{:#?}", stack_frame);
     hlt_loop();
 }
 
-extern "x86-interrupt" fn timer_interrupt_handler(
-    _stack_frame: &mut InterruptStackFrame
-) {
+extern "x86-interrupt" fn timer_interrupt_handler(_stack_frame: &mut InterruptStackFrame) {
     print!(".");
 
     unsafe {
-        PICS.lock().notify_end_of_interrupt(InterruptIndex::Timer.as_u8());
+        PICS.lock()
+            .notify_end_of_interrupt(InterruptIndex::Timer.as_u8());
     }
 }
 
 pub const PIC_1_OFFSET: u8 = 32;
 pub const PIC_2_OFFSET: u8 = PIC_1_OFFSET + 8;
 
-pub static PICS: spin::Mutex<ChainedPics> = spin::Mutex::new(unsafe {
-    ChainedPics::new(PIC_1_OFFSET, PIC_2_OFFSET)
-});
+pub static PICS: spin::Mutex<ChainedPics> =
+    spin::Mutex::new(unsafe { ChainedPics::new(PIC_1_OFFSET, PIC_2_OFFSET) });
 
 extern "x86-interrupt" fn keyboard_interrupt_handler(_stack_frame: &mut InterruptStackFrame) {
-    use x86_64::instructions::port::Port;
-    use pc_keyboard::{Keyboard, ScancodeSet1, DecodedKey, layouts};
+    use pc_keyboard::{layouts, DecodedKey, Keyboard, ScancodeSet1};
     use spin::Mutex;
+    use x86_64::instructions::port::Port;
 
     lazy_static! {
         static ref KEYBOARD: Mutex<Keyboard<layouts::Us104Key, ScancodeSet1>> =
@@ -90,6 +88,19 @@ extern "x86-interrupt" fn keyboard_interrupt_handler(_stack_frame: &mut Interrup
     }
 }
 
+extern "x86-interrupt" fn page_fault_handler(
+    stack_frame: &mut InterruptStackFrame,
+    error_code: PageFaultErrorCode,
+) {
+    use x86_64::registers::control::Cr2;
+
+    println!("EXCEPTION: PAGE FAULT");
+    println!("Accessed Address: {:?}", Cr2::read());
+    println!("Error Code: {:?}", error_code);
+    println!("{:#?}", stack_frame);
+    hlt_loop();
+}
+
 #[derive(Debug, Clone, Copy)]
 #[repr(u8)]
 pub enum InterruptIndex {

src/lib.rs

@@ -7,10 +7,17 @@
 
 use core::panic::PanicInfo;
 
+#[cfg(test)]
+use bootloader::{entry_point, BootInfo};
+
+#[cfg(test)]
+entry_point!(test_kernel_main);
+
 pub mod gdt;
 pub mod interrupts;
-pub mod serial;
 pub mod macros;
+pub mod memory;
+pub mod serial;
 pub mod vga_buffer;
 
 pub fn test_runner(tests: &[&dyn Fn()]) {
@@ -30,8 +37,7 @@ pub fn test_panic_handler(info: &PanicInfo) -> ! {
 
 /// Entry point for `cargo xtest`
 #[cfg(test)]
-#[no_mangle]
-pub extern "C" fn _start() -> ! {
+fn test_kernel_main(_boot_info: &'static BootInfo) -> ! {
     init();
     test_main();
     hlt_loop();

src/main.rs

@@ -7,6 +7,7 @@
 use core::panic::PanicInfo;
 
 use blog_os::println;
+use bootloader::{entry_point, BootInfo};
 
 /// This function is called on panic.
 #[cfg(not(test))]
@@ -22,12 +23,28 @@ fn panic(info: &PanicInfo) -> ! {
     blog_os::test_panic_handler(info)
 }
 
-#[no_mangle]
-pub extern "C" fn _start() -> ! {
-    println!("Hello World{}", "!");
+entry_point!(kernel_main);
 
+fn kernel_main(boot_info: &'static BootInfo) -> ! {
+    use blog_os::memory;
+    use x86_64::{structures::paging::Page, VirtAddr};
+
+    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 { memory::BootInfoFrameAllocator::init(&boot_info.memory_map) };
+
+    let page = Page::containing_address(VirtAddr::new(0xdeadbeef000));
+    memory::create_example_mapping(page, &mut mapper, &mut frame_allocator);
+
+    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 +1,104 @@
+use bootloader::bootinfo::{MemoryMap, MemoryRegionType};
+use x86_64::{
+    structures::paging::{
+        FrameAllocator, Mapper, OffsetPageTable, Page, PageTable, PhysFrame, Size4KiB,
+    },
+    PhysAddr, VirtAddr,
+};
+
+/// A FrameAllocator that always returns `None`.
+pub struct EmptyFrameAllocator;
+
+unsafe impl FrameAllocator<Size4KiB> for EmptyFrameAllocator {
+    fn allocate_frame(&mut self) -> Option<PhysFrame> {
+        None
+    }
+}
+
+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
+    /// meory map is valid. The main requirement is that all frame 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
+    }
+}
+
+/// 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> {
+    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();
+
+    &mut *page_table_ptr
+}
+
+/// Creates an example maping 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 { mapper.map_to(page, frame, flags, frame_allocator) };
+
+    map_to_result.expect("map_to failed").flush();
+}

tests/should_panic.rs

@@ -1,8 +1,8 @@
 #![no_std]
 #![no_main]
 
+use blog_os::{exit_qemu, serial_print, serial_println, QemuExitCode};
 use core::panic::PanicInfo;
-use blog_os::{QemuExitCode, exit_qemu, serial_print, serial_println};
 
 #[no_mangle]
 pub extern "C" fn _start() -> ! {

tests/stack_overflow.rs

@@ -22,8 +22,7 @@ lazy_static! {
     };
 }
 
-
-use blog_os::{exit_qemu, QemuExitCode, serial_print, serial_println};
+use blog_os::{exit_qemu, serial_print, serial_println, QemuExitCode};
 
 #[no_mangle]
 pub extern "C" fn _start() -> ! {