Align the double fault stack through a new wrapper type

Make double fault handlers diverging

.github/workflows/build-code.yml

@@ -53,6 +53,32 @@ jobs:
     - name: "Create Bootimage"
       run: cargo bootimage
 
+     # install QEMU
+    - name: Install QEMU (Linux)
+      run: sudo apt update && sudo apt install qemu-system-x86
+      if: runner.os == 'Linux'
+    - name: Install QEMU (macOS)
+      run: brew install qemu
+      if: runner.os == 'macOS'
+      env:
+        HOMEBREW_NO_AUTO_UPDATE: 1
+        HOMEBREW_NO_BOTTLE_SOURCE_FALLBACK: 1
+        HOMEBREW_NO_INSTALL_CLEANUP: 1
+    - name: Install Scoop (Windows)
+      run: |
+        Invoke-Expression (New-Object System.Net.WebClient).DownloadString('https://get.scoop.sh')
+        echo ::add-path::$HOME\scoop\shims
+      if: runner.os == 'Windows'
+      shell: pwsh
+    - name: Install QEMU (Windows)
+      run: scoop install qemu
+      if: runner.os == 'Windows'
+      shell: pwsh
+    - name: "Print QEMU Version"
+      run: qemu-system-x86_64 --version
+
+    - name: "Run cargo xtest"
+      run: cargo xtest
 
   check_formatting:
     name: "Check Formatting"

Cargo.lock

@@ -1,5 +1,26 @@
 # This file is automatically @generated by Cargo.
 # It is not intended for manual editing.
+[[package]]
+name = "array-init"
+version = "0.0.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "23589ecb866b460d3a0f1278834750268c607e8e28a1b982c907219f3178cd72"
+dependencies = [
+ "nodrop",
+]
+
+[[package]]
+name = "bit_field"
+version = "0.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ed8765909f9009617974ab6b7d332625b320b33c326b1e9321382ef1999b5d56"
+
+[[package]]
+name = "bitflags"
+version = "1.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cf1de2fe8c75bc145a2f577add951f8134889b4795d47466a54a5c846d691693"
+
 [[package]]
 name = "blog_os"
 version = "0.1.0"
@@ -7,7 +28,9 @@ dependencies = [
  "bootloader",
  "lazy_static",
  "spin",
+ "uart_16550",
  "volatile",
+ "x86_64 0.8.1",
 ]
 
 [[package]]
@@ -16,6 +39,15 @@ version = "0.8.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d596849a47f28abdea62d7a6a25c4f6e69c3d9b09b0a2877db6e9cda004ca993"
 
+[[package]]
+name = "cast"
+version = "0.2.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4b9434b9a5aa1450faa3f9cb14ea0e8c53bb5d2b3c1bfd1ab4fc03e9f33fbfb0"
+dependencies = [
+ "rustc_version",
+]
+
 [[package]]
 name = "lazy_static"
 version = "1.4.0"
@@ -25,14 +57,85 @@ dependencies = [
  "spin",
 ]
 
+[[package]]
+name = "nodrop"
+version = "0.1.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "72ef4a56884ca558e5ddb05a1d1e7e1bfd9a68d9ed024c21704cc98872dae1bb"
+
+[[package]]
+name = "rustc_version"
+version = "0.2.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "138e3e0acb6c9fb258b19b67cb8abd63c00679d2851805ea151465464fe9030a"
+dependencies = [
+ "semver",
+]
+
+[[package]]
+name = "semver"
+version = "0.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1d7eb9ef2c18661902cc47e535f9bc51b78acd254da71d375c2f6720d9a40403"
+dependencies = [
+ "semver-parser",
+]
+
+[[package]]
+name = "semver-parser"
+version = "0.7.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "388a1df253eca08550bef6c72392cfe7c30914bf41df5269b68cbd6ff8f570a3"
+
 [[package]]
 name = "spin"
 version = "0.5.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6e63cff320ae2c57904679ba7cb63280a3dc4613885beafb148ee7bf9aa9042d"
 
+[[package]]
+name = "uart_16550"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "803ea8cb602dbb32c1a657a866d2dd79fe7dbeab0fb2ac667cb4dcc7de12a58b"
+dependencies = [
+ "bitflags",
+ "x86_64 0.7.7",
+]
+
+[[package]]
+name = "ux"
+version = "0.1.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "88dfeb711b61ce620c0cb6fd9f8e3e678622f0c971da2a63c4b3e25e88ed012f"
+
 [[package]]
 name = "volatile"
 version = "0.2.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6af0edf5b4faacc31fc51159244d78d65ec580f021afcef7bd53c04aeabc7f29"
+
+[[package]]
+name = "x86_64"
+version = "0.7.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1f27d9168654aee1b0c1b73746caeb4aa33248f8b8c8f6e100e697fcc2a794b2"
+dependencies = [
+ "array-init",
+ "bit_field",
+ "bitflags",
+ "cast",
+ "ux",
+]
+
+[[package]]
+name = "x86_64"
+version = "0.8.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f21672dcbed52bc09eea030d189600c0189c66c97bc5b31779eb780e064a201f"
+dependencies = [
+ "array-init",
+ "bit_field",
+ "bitflags",
+ "cast",
+]

Cargo.toml

@@ -4,11 +4,29 @@ version = "0.1.0"
 authors = ["Philipp Oppermann <dev@phil-opp.com>"]
 edition = "2018"
 
+[[test]]
+name = "should_panic"
+harness = false
+
+[[test]]
+name = "stack_overflow"
+harness = false
+
 [dependencies]
 bootloader = "0.8.0"
 volatile = "0.2.6"
 spin = "0.5.2"
+x86_64 = "0.8.1"
+uart_16550 = "0.2.0"
 
 [dependencies.lazy_static]
 version = "1.0"
 features = ["spin_no_std"]
+
+
+[package.metadata.bootimage]
+test-args = [
+    "-device", "isa-debug-exit,iobase=0xf4,iosize=0x04", "-serial", "stdio",
+    "-display", "none"
+]
+test-success-exit-code = 33         # (0x10 << 1) | 1

README.md

@@ -1,10 +1,10 @@
-# Blog OS (VGA Text Mode)
+# Blog OS (Double Faults)
 
-[![Build Status](https://github.com/phil-opp/blog_os/workflows/Build%20Code/badge.svg?branch=post-03)](https://github.com/phil-opp/blog_os/actions?query=workflow%3A%22Build+Code%22+branch%3Apost-03)
+[![Build Status](https://github.com/phil-opp/blog_os/workflows/Build%20Code/badge.svg?branch=post-06)](https://github.com/phil-opp/blog_os/actions?query=workflow%3A%22Build+Code%22+branch%3Apost-06)
 
-This repository contains the source code for the [VGA Text Mode][post] post of the [Writing an OS in Rust](https://os.phil-opp.com) series.
+This repository contains the source code for the [Double Faults][post] post of the [Writing an OS in Rust](https://os.phil-opp.com) series.
 
-[post]: https://os.phil-opp.com/vga-text-mode/
+[post]: https://os.phil-opp.com/double-fault-exceptions/
 
 **Check out the [master branch](https://github.com/phil-opp/blog_os) for more information.**
 
@@ -52,6 +52,10 @@ dd if=target/x86_64-blog_os/debug/bootimage-blog_os.bin of=/dev/sdX && sync
 
 Where `sdX` is the device name of your USB stick. **Be careful** to choose the correct device name, because everything on that device is overwritten.
 
+## Testing
+
+To run the unit and integration tests, execute `cargo xtest`.
+
 ## License
 
 Licensed under either of

src/gdt.rs

@@ -0,0 +1,56 @@
+use lazy_static::lazy_static;
+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;
+
+lazy_static! {
+    static ref TSS: TaskStateSegment = {
+        let mut tss = TaskStateSegment::new();
+        tss.interrupt_stack_table[DOUBLE_FAULT_IST_INDEX as usize] = {
+            const STACK_SIZE: usize = 4096;
+
+            #[repr(align(16))]
+            struct Stack([u8; STACK_SIZE]);
+
+            static mut STACK: Stack = Stack([0; STACK_SIZE]);
+
+            let stack_start = VirtAddr::from_ptr(unsafe { &STACK });
+            let stack_end = stack_start + STACK_SIZE;
+            stack_end
+        };
+        tss
+    };
+}
+
+lazy_static! {
+    static ref GDT: (GlobalDescriptorTable, Selectors) = {
+        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,
+            },
+        )
+    };
+}
+
+struct Selectors {
+    code_selector: SegmentSelector,
+    tss_selector: SegmentSelector,
+}
+
+pub fn init() {
+    use x86_64::instructions::segmentation::set_cs;
+    use x86_64::instructions::tables::load_tss;
+
+    GDT.0.load();
+    unsafe {
+        set_cs(GDT.1.code_selector);
+        load_tss(GDT.1.tss_selector);
+    }
+}

src/interrupts.rs

@@ -0,0 +1,42 @@
+use crate::{gdt, println};
+use lazy_static::lazy_static;
+use x86_64::structures::idt::{InterruptDescriptorTable, InterruptStackFrame};
+
+lazy_static! {
+    static ref IDT: InterruptDescriptorTable = {
+        let mut idt = InterruptDescriptorTable::new();
+        idt.breakpoint.set_handler_fn(breakpoint_handler);
+        unsafe {
+            idt.double_fault
+                .set_handler_fn(double_fault_handler)
+                .set_stack_index(gdt::DOUBLE_FAULT_IST_INDEX);
+        }
+        idt
+    };
+}
+
+pub fn init_idt() {
+    IDT.load();
+}
+
+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,
+) -> ! {
+    panic!("EXCEPTION: DOUBLE FAULT\n{:#?}", stack_frame);
+}
+
+#[cfg(test)]
+use crate::{serial_print, serial_println};
+
+#[test_case]
+fn test_breakpoint_exception() {
+    serial_print!("test_breakpoint_exception...");
+    // invoke a breakpoint exception
+    x86_64::instructions::interrupts::int3();
+    serial_println!("[ok]");
+}

src/lib.rs

@@ -0,0 +1,64 @@
+#![no_std]
+#![cfg_attr(test, no_main)]
+#![feature(custom_test_frameworks)]
+#![feature(abi_x86_interrupt)]
+#![test_runner(crate::test_runner)]
+#![reexport_test_harness_main = "test_main"]
+
+use core::panic::PanicInfo;
+
+pub mod gdt;
+pub mod interrupts;
+pub mod serial;
+pub mod vga_buffer;
+
+pub fn init() {
+    gdt::init();
+    interrupts::init_idt();
+}
+
+pub fn test_runner(tests: &[&dyn Fn()]) {
+    serial_println!("Running {} tests", tests.len());
+    for test in tests {
+        test();
+    }
+    exit_qemu(QemuExitCode::Success);
+}
+
+pub fn test_panic_handler(info: &PanicInfo) -> ! {
+    serial_println!("[failed]\n");
+    serial_println!("Error: {}\n", info);
+    exit_qemu(QemuExitCode::Failed);
+    loop {}
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+#[repr(u32)]
+pub enum QemuExitCode {
+    Success = 0x10,
+    Failed = 0x11,
+}
+
+pub fn exit_qemu(exit_code: QemuExitCode) {
+    use x86_64::instructions::port::Port;
+
+    unsafe {
+        let mut port = Port::new(0xf4);
+        port.write(exit_code as u32);
+    }
+}
+
+/// Entry point for `cargo xtest`
+#[cfg(test)]
+#[no_mangle]
+pub extern "C" fn _start() -> ! {
+    init();
+    test_main();
+    loop {}
+}
+
+#[cfg(test)]
+#[panic_handler]
+fn panic(info: &PanicInfo) -> ! {
+    test_panic_handler(info)
+}

src/main.rs

@@ -1,20 +1,42 @@
 #![no_std]
 #![no_main]
+#![feature(custom_test_frameworks)]
+#![test_runner(blog_os::test_runner)]
+#![reexport_test_harness_main = "test_main"]
 
+use blog_os::println;
 use core::panic::PanicInfo;
 
-mod vga_buffer;
-
 #[no_mangle]
 pub extern "C" fn _start() -> ! {
     println!("Hello World{}", "!");
 
+    blog_os::init();
+
+    fn stack_overflow() {
+        stack_overflow(); // for each recursion, the return address is pushed
+    }
+
+    // uncomment line below to trigger a stack overflow
+    // stack_overflow();
+
+    #[cfg(test)]
+    test_main();
+
+    println!("It did not crash!");
     loop {}
 }
 
 /// This function is called on panic.
+#[cfg(not(test))]
 #[panic_handler]
 fn panic(info: &PanicInfo) -> ! {
     println!("{}", info);
     loop {}
 }
+
+#[cfg(test)]
+#[panic_handler]
+fn panic(info: &PanicInfo) -> ! {
+    blog_os::test_panic_handler(info)
+}

src/serial.rs

@@ -0,0 +1,37 @@
+use lazy_static::lazy_static;
+use spin::Mutex;
+use uart_16550::SerialPort;
+
+lazy_static! {
+    pub static ref SERIAL1: Mutex<SerialPort> = {
+        let mut serial_port = unsafe { SerialPort::new(0x3F8) };
+        serial_port.init();
+        Mutex::new(serial_port)
+    };
+}
+
+#[doc(hidden)]
+pub fn _print(args: ::core::fmt::Arguments) {
+    use core::fmt::Write;
+    SERIAL1
+        .lock()
+        .write_fmt(args)
+        .expect("Printing to serial failed");
+}
+
+/// Prints to the host through the serial interface.
+#[macro_export]
+macro_rules! serial_print {
+    ($($arg:tt)*) => {
+        $crate::serial::_print(format_args!($($arg)*));
+    };
+}
+
+/// Prints to the host through the serial interface, appending a newline.
+#[macro_export]
+macro_rules! serial_println {
+    () => ($crate::serial_print!("\n"));
+    ($fmt:expr) => ($crate::serial_print!(concat!($fmt, "\n")));
+    ($fmt:expr, $($arg:tt)*) => ($crate::serial_print!(
+        concat!($fmt, "\n"), $($arg)*));
+}

src/vga_buffer.rs

@@ -3,6 +3,9 @@ use lazy_static::lazy_static;
 use spin::Mutex;
 use volatile::Volatile;
 
+#[cfg(test)]
+use crate::{serial_print, serial_println};
+
 lazy_static! {
     /// A global `Writer` instance that can be used for printing to the VGA text buffer.
     ///
@@ -169,3 +172,33 @@ pub fn _print(args: fmt::Arguments) {
     use core::fmt::Write;
     WRITER.lock().write_fmt(args).unwrap();
 }
+
+#[test_case]
+fn test_println_simple() {
+    serial_print!("test_println... ");
+    println!("test_println_simple output");
+    serial_println!("[ok]");
+}
+
+#[test_case]
+fn test_println_many() {
+    serial_print!("test_println_many... ");
+    for _ in 0..200 {
+        println!("test_println_many output");
+    }
+    serial_println!("[ok]");
+}
+
+#[test_case]
+fn test_println_output() {
+    serial_print!("test_println_output... ");
+
+    let s = "Some test string that fits on a single line";
+    println!("{}", s);
+    for (i, c) in s.chars().enumerate() {
+        let screen_char = WRITER.lock().buffer.chars[BUFFER_HEIGHT - 2][i].read();
+        assert_eq!(char::from(screen_char.ascii_character), c);
+    }
+
+    serial_println!("[ok]");
+}

tests/basic_boot.rs

@@ -0,0 +1,27 @@
+#![no_std]
+#![no_main]
+#![feature(custom_test_frameworks)]
+#![test_runner(blog_os::test_runner)]
+#![reexport_test_harness_main = "test_main"]
+
+use blog_os::{println, serial_print, serial_println};
+use core::panic::PanicInfo;
+
+#[no_mangle] // don't mangle the name of this function
+pub extern "C" fn _start() -> ! {
+    test_main();
+
+    loop {}
+}
+
+#[panic_handler]
+fn panic(info: &PanicInfo) -> ! {
+    blog_os::test_panic_handler(info)
+}
+
+#[test_case]
+fn test_println() {
+    serial_print!("test_println... ");
+    println!("test_println output");
+    serial_println!("[ok]");
+}

tests/should_panic.rs

@@ -0,0 +1,25 @@
+#![no_std]
+#![no_main]
+
+use blog_os::{exit_qemu, serial_print, serial_println, QemuExitCode};
+use core::panic::PanicInfo;
+
+#[no_mangle]
+pub extern "C" fn _start() -> ! {
+    should_fail();
+    serial_println!("[test did not panic]");
+    exit_qemu(QemuExitCode::Failed);
+    loop {}
+}
+
+fn should_fail() {
+    serial_print!("should_fail... ");
+    assert_eq!(0, 1);
+}
+
+#[panic_handler]
+fn panic(_info: &PanicInfo) -> ! {
+    serial_println!("[ok]");
+    exit_qemu(QemuExitCode::Success);
+    loop {}
+}

tests/stack_overflow.rs

@@ -0,0 +1,57 @@
+#![no_std]
+#![no_main]
+#![feature(abi_x86_interrupt)]
+
+use blog_os::{exit_qemu, serial_print, serial_println, QemuExitCode};
+use core::panic::PanicInfo;
+use lazy_static::lazy_static;
+use x86_64::structures::idt::{InterruptDescriptorTable, InterruptStackFrame};
+
+#[no_mangle]
+pub extern "C" fn _start() -> ! {
+    serial_print!("stack_overflow... ");
+
+    blog_os::gdt::init();
+    init_test_idt();
+
+    // trigger a stack overflow
+    stack_overflow();
+
+    panic!("Execution continued after stack overflow");
+}
+
+#[allow(unconditional_recursion)]
+fn stack_overflow() {
+    stack_overflow(); // for each recursion, the return address is pushed
+}
+
+lazy_static! {
+    static ref TEST_IDT: InterruptDescriptorTable = {
+        let mut idt = InterruptDescriptorTable::new();
+        unsafe {
+            idt.double_fault
+                .set_handler_fn(test_double_fault_handler)
+                .set_stack_index(blog_os::gdt::DOUBLE_FAULT_IST_INDEX);
+        }
+
+        idt
+    };
+}
+
+pub fn init_test_idt() {
+    TEST_IDT.load();
+}
+
+extern "x86-interrupt" fn test_double_fault_handler(
+    _stack_frame: &mut InterruptStackFrame,
+    _error_code: u64,
+) -> ! {
+    serial_println!("[ok]");
+    exit_qemu(QemuExitCode::Success);
+    loop {}
+}
+
+#[panic_handler]
+fn panic(info: &PanicInfo) -> ! {
+    blog_os::test_panic_handler(info)
+}