From 03acf2943efa4842beb57f8f6d6e5892ecdb5713 Mon Sep 17 00:00:00 2001
From: Julien CLEMENT <julien.clement@epita.fr>
Date: Fri, 3 Dec 2021 22:32:03 +0100
Subject: [PATCH] feat(gdt): add gdt, tss, stack in dedicated section to no
 overwrite pagination pages

Signed-off-by: Julien CLEMENT <julien.clement@epita.fr>
---
 src/boot/boot.asm |  3 ++-
 src/gdt.rs        | 45 +++++++++++++++++++++++++++++++++++++++++++++
 src/interrupts.rs | 21 ++++++++++++++++-----
 src/lib.rs        | 12 +++++++++---
 4 files changed, 72 insertions(+), 9 deletions(-)
 create mode 100644 src/gdt.rs

diff --git a/src/boot/boot.asm b/src/boot/boot.asm
index 4834c91..05ea5f4 100644
--- a/src/boot/boot.asm
+++ b/src/boot/boot.asm
@@ -163,8 +163,9 @@ p3_table:
 p2_table:
     resb 4096
 
+section .stack
 stack_bottom:
-    resb 65536
+    resb 0x800000
 stack_top:
 
 
diff --git a/src/gdt.rs b/src/gdt.rs
new file mode 100644
index 0000000..7ab41cb
--- /dev/null
+++ b/src/gdt.rs
@@ -0,0 +1,45 @@
+use crate::println;
+use lazy_static::lazy_static;
+use x86_64::{VirtAddr, structures::tss::TaskStateSegment};
+use x86_64::structures::gdt::{GlobalDescriptorTable, Descriptor, SegmentSelector};
+use x86_64::instructions::{segmentation::{CS, Segment}, tables::load_tss};
+
+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 })
+    };
+}
+
+pub fn init_gdt() {
+    println!("Loading GDT");
+    GDT.0.load();
+    unsafe {
+        CS::set_reg(GDT.1.code_selector);
+        load_tss(GDT.1.tss_selector);
+    }
+}
+
+struct Selectors {
+    code_selector: SegmentSelector,
+    tss_selector: SegmentSelector,
+}
diff --git a/src/interrupts.rs b/src/interrupts.rs
index 51b235d..ee67b4b 100644
--- a/src/interrupts.rs
+++ b/src/interrupts.rs
@@ -1,25 +1,36 @@
-use x86_64::structures::idt::{InterruptDescriptorTable, InterruptStackFrame};
+use crate::gdt;
 use crate::println;
-use lazy_static::lazy_static;
 use crate::vga::{self, Color, ColorCode};
+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() {
-    println!("Load IDT");
+    println!("Loading IDT");
     IDT.load();
 }
 
-extern "x86-interrupt" fn breakpoint_handler(
-    stack_frame: InterruptStackFrame) {
+extern "x86-interrupt" fn breakpoint_handler(stack_frame: InterruptStackFrame) {
     let color: vga::ColorCode = vga::get_color();
     vga::change_color(ColorCode::new(Color::Pink, Color::Black));
     println!("EXCEPTION: BREAKPOINT\n{:#?}", stack_frame);
     vga::change_color(color);
 }
+
+extern "x86-interrupt" fn double_fault_handler(
+    stack_frame: InterruptStackFrame,
+    _error_code: u64,
+) -> ! {
+    panic!("EXCEPTION: DOUBLE FAULT\n{:#?}", stack_frame);
+}
diff --git a/src/lib.rs b/src/lib.rs
index 1c5364d..2bdba0d 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -2,9 +2,10 @@
 #![no_main]
 #![feature(abi_x86_interrupt)]
 
+mod gdt;
+mod interrupts;
 mod serial;
 mod vga;
-mod interrupts;
 
 use core::panic::PanicInfo;
 use vga::{Color, ColorCode};
@@ -19,6 +20,7 @@ fn panic_handler(info: &PanicInfo) -> ! {
 pub fn init() {
     vga::change_color(ColorCode::new(Color::LightCyan, Color::Black));
     println!("Starting init");
+    gdt::init_gdt();
     interrupts::init_idt();
     vga::change_color(ColorCode::new(Color::LightGreen, Color::Black));
 }
@@ -27,7 +29,11 @@ pub fn init() {
 pub extern "C" fn julios_main() -> ! {
     init();
     println!("***JuliOS V0.1.0***");
-    serial_println!("Hello serial");
-    x86_64::instructions::interrupts::int3();
+    fn stack_overflow() {
+        stack_overflow(); // for each recursion, the return address is pushed
+    }
+
+    stack_overflow();
+
     panic!("Kernel end of flow");
 }