From beb2227d7e4c1d95854dddba6b55bfbe9c9068a8 Mon Sep 17 00:00:00 2001
From: Conzer <vaporvault04@gmail.com>
Date: Tue, 3 Dec 2024 19:24:57 -0500
Subject: [PATCH] Handle all double faults (3h44m)

---
 src/gdt.rs        | 47 +++++++++++++++++++++++++++++++++++++++++++++++
 src/interrupts.rs | 13 +++++++++++++
 src/lib.rs        |  9 ++++++---
 src/main.rs       |  6 +++++-
 4 files changed, 71 insertions(+), 4 deletions(-)
 create mode 100644 src/gdt.rs

diff --git a/src/gdt.rs b/src/gdt.rs
new file mode 100644
index 0000000..707716d
--- /dev/null
+++ b/src/gdt.rs
@@ -0,0 +1,47 @@
+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;
+
+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(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,
+}
\ No newline at end of file
diff --git a/src/interrupts.rs b/src/interrupts.rs
index d0440b1..c9f1da3 100644
--- a/src/interrupts.rs
+++ b/src/interrupts.rs
@@ -1,10 +1,17 @@
 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); // new
+        }
+
         idt
     };
 }
@@ -19,6 +26,12 @@ extern "x86-interrupt" fn breakpoint_handler(
     println!("EXCEPTION: BREAKPOINT\n{:#?}", stack_frame);
 }
 
+extern "x86-interrupt" fn double_fault_handler(
+    stack_frame: InterruptStackFrame, _error_code: u64) -> !
+{
+    panic!("EXCEPTION: DLB FAULT\n{:#?}", stack_frame);
+}
+
 #[test_case]
 fn test_breakpoint_exception() {
     // invoke a breakpoint exception
diff --git a/src/lib.rs b/src/lib.rs
index 297bb59..a28f671 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -6,13 +6,16 @@
 #![reexport_test_harness_main = "test_main"]
 #![feature(abi_x86_interrupt)]
 
-pub fn init() {
-    interrupts::init_idt();
-}
 
 pub mod serial;
 pub mod vga_buffer;
 pub mod interrupts;
+pub mod gdt;
+
+pub fn init() {
+    gdt::init();
+    interrupts::init_idt();
+}
 
 use core::panic::PanicInfo;
 
diff --git a/src/main.rs b/src/main.rs
index f794e6b..b66d41a 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -13,7 +13,11 @@ pub extern "C" fn _start() -> ! {
 
     donald::init();
 
-    x86_64::instructions::interrupts::int3();
+    fn stack_overflow() {
+        stack_overflow();
+    }
+
+    stack_overflow();
 
     #[cfg(test)]
     test_main();