stack overflow no longer causes a chain reaction leading to a triple exception and a system reboot

4 files changed, 72 insertions, 3 deletions

diff --git a/StrixKernel/src/gdt.rs b/StrixKernel/src/gdt.rs
new file mode 100644
index 0000000..e0c3d71
--- /dev/null
+++ b/StrixKernel/src/gdt.rs
@@ -0,0 +1,54 @@
+// src/gdt.rs
+
+use x86_64::VirtAddr;
+use x86_64::structures::tss::TaskStateSegment;
+use lazy_static::lazy_static;
+
+pub const DOUBLE_FAULT_IST_INDEX: u16 = 0;
+
+pub fn init() {
+    use x86_64::instructions::tables::load_tss;
+    use x86_64::instructions::segmentation::{CS, Segment};
+
+    GDT.0.load();
+
+    unsafe {
+        CS::set_reg(GDT.1.code_selector);
+        load_tss(GDT.1.tss_selector);
+    }
+
+}
+
+
+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(&raw const STACK);
+            let stack_end = stack_start + STACK_SIZE;
+            stack_end
+        };
+        tss
+    };
+}
+
+use x86_64::structures::gdt::SegmentSelector;
+use x86_64::structures::gdt::GlobalDescriptorTable;
+use x86_64::structures::gdt::Descriptor;
+
+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,
+}
diff --git a/StrixKernel/src/interrupts.rs b/StrixKernel/src/interrupts.rs
index e55aa13..e79898a 100644
--- a/StrixKernel/src/interrupts.rs
+++ b/StrixKernel/src/interrupts.rs
@@ -1,14 +1,21 @@
 // interrupts.rs
 
 use x86_64::structures::idt::{InterruptDescriptorTable, InterruptStackFrame};
-use crate::println;
 use lazy_static::lazy_static;
 
+use crate::println;
+use crate::gdt;
+
+
 lazy_static! {
     static ref IDT: InterruptDescriptorTable = {
         let mut idt = InterruptDescriptorTable::new();
         idt.breakpoint.set_handler_fn(breakpoint_handler); // breakpoint exception handler
-        idt.double_fault.set_handler_fn(double_fault_handler); // double fault exception handler // IMPORTANT (if not implemented would cause a triple fault and thus a system reset which is bad)
+unsafe {
+            idt.double_fault.set_handler_fn(double_fault_handler)
+                .set_stack_index(gdt::DOUBLE_FAULT_IST_INDEX); // new
+        }
+
         idt
     };
 }
diff --git a/StrixKernel/src/lib.rs b/StrixKernel/src/lib.rs
index a1c4553..9572cf7 100644
--- a/StrixKernel/src/lib.rs
+++ b/StrixKernel/src/lib.rs
@@ -10,12 +10,14 @@ use core::panic::PanicInfo;
 pub mod serial;
 pub mod vga_buffer;
 pub mod interrupts;
+pub mod gdt;
 
 pub trait Testable {
     fn run(&self) -> ();
 }
 
 pub fn init() {
+    gdt::init();
     interrupts::init_idt();    
 }
 
diff --git a/StrixKernel/src/main.rs b/StrixKernel/src/main.rs
index 3fa7149..91689cc 100644
--- a/StrixKernel/src/main.rs
+++ b/StrixKernel/src/main.rs
@@ -14,10 +14,16 @@ pub extern "C" fn _start() -> ! {
 
     strix_os::init(); // Call the init function as declared in ./lib.rs
 
+    // Cause a stack overflow
+    fn stack_overflow() {
+        stack_overflow();
+    }
+
+    stack_overflow();
     // Continue as normal
     #[cfg(test)]
     test_main();
-    
+
     loop {}
 }