Double Faults

src/gdt.rs

@@ -0,0 +1,48 @@
+use x86_64::VirtAddr;
+use x86_64::structures::tss::TaskStateSegment;
+use lazy_static::lazy_static;
+use x86_64::structures::gdt::{GlobalDescriptorTable, Descriptor};
+use x86_64::structures::gdt::SegmentSelector;
+
+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 * 5;
+            static mut STACK: [u8; STACK_SIZE] = [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() {
+    #[allow(deprecated)]
+    use x86_64::instructions::segmentation::set_cs;
+    use x86_64::instructions::tables::load_tss;
+
+    GDT.0.load();
+    unsafe {
+        #[allow(deprecated)]
+        set_cs(GDT.1.code_selector);
+        load_tss(GDT.1.tss_selector);
+    }
+}

src/interrupts.rs

@@ -1,11 +1,16 @@
 use x86_64::structures::idt::{InterruptDescriptorTable, InterruptStackFrame};
 use crate::println;
 use lazy_static::lazy_static;
+use crate::gdt;
 
 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
     };
 }
@@ -17,3 +22,7 @@ pub fn init_idt() {
 extern "x86-interrupt" fn breakpoint_handler(stack_frame: InterruptStackFrame) {
     println!("EXCEPTION: BREAKPOINT\n{:#?}", stack_frame);
 }
+
+extern "x86-interrupt" fn double_fault_handler(stack_frame: InterruptStackFrame, _error_code: u64) -> ! {
+    panic!("EXCEPTION: DOUBLE FAULT\n{:#?}", stack_frame);
+}

src/lib.rs

@@ -9,6 +9,7 @@ use core::panic::PanicInfo;
 pub mod serial;
 pub mod vga_buffer;
 pub mod interrupts;
+pub mod gdt;
 
 pub trait Testable {
     fn run(&self) -> ();
@@ -79,5 +80,6 @@ pub fn exit_qemu(exit_code: QemuExitCode) {
 }
 
 pub fn init() {
+    gdt::init();
     interrupts::init_idt();
 }

src/main.rs

@@ -15,9 +15,18 @@ pub extern "C" fn _start() -> ! {
     println!("Hello World{}", "!");
 
     anos::init();
+
+    // 触发一个中断
     x86_64::instructions::interrupts::int3();
     println!("It didn't crash!");
 
+    // 触发一个页错误
+    // 由于我们没有设定页错误的处理函数
+    // 所以会触发 double fault
+    unsafe {
+        *(0xdeadbeef as *mut u64) = 42; // 强制写入某个内存地址
+    }
+
     #[cfg(test)]
     test_main();