From 0264a5e4b626eaeb109c3339210f4911edc6a8bc Mon Sep 17 00:00:00 2001
From: greg <greg.shuflin@protonmail.com>
Date: Thu, 18 Jul 2019 03:01:57 -0700
Subject: [PATCH] GDT, IDT stuff

set a separate stack for double-fault handler
---
 src/gdt.rs        | 47 +++++++++++++++++++++++++++++++++++++++++++++++
 src/interrupts.rs |  7 ++++++-
 src/main.rs       | 18 +++++++++++-------
 3 files changed, 64 insertions(+), 8 deletions(-)
 create mode 100644 src/gdt.rs

diff --git a/src/gdt.rs b/src/gdt.rs
new file mode 100644
index 0000000..2748534
--- /dev/null
+++ b/src/gdt.rs
@@ -0,0 +1,47 @@
+use x86_64::VirtAddr;
+use x86_64::structures::tss::TaskStateSegment;
+use x86_64::structures::gdt::{GlobalDescriptorTable, Descriptor, SegmentSelector};
+use lazy_static::lazy_static;
+
+//double fault interrupt stack table
+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; //4k stack
+
+      //this static mut is temporarily the stack until proper allocation can be implemented
+      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
+  };
+}
+
+struct Selectors {
+  code_selector: SegmentSelector,
+  data_selector: SegmentSelector,
+}
+
+lazy_static! {
+  static ref GDT: (GlobalDescriptorTable, Selectors) = {
+    let mut gdt = GlobalDescriptorTable::new();
+    let code_selector = gdt.add_entry(Descriptor::kernel_code_segment());
+    let data_selector = gdt.add_entry(Descriptor::tss_segment(&TSS));
+    (gdt, Selectors { code_selector, data_selector })
+  };
+}
+
+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.data_selector);
+  }
+}
diff --git a/src/interrupts.rs b/src/interrupts.rs
index fa67843..3d70e98 100644
--- a/src/interrupts.rs
+++ b/src/interrupts.rs
@@ -2,11 +2,16 @@ use lazy_static::lazy_static;
 use x86_64::structures::idt::{InterruptStackFrame, InterruptDescriptorTable};
 use crate::println;
 
+use crate::gdt;
+
 lazy_static! {
   static ref IDT: InterruptDescriptorTable = {
     let mut idt = InterruptDescriptorTable::new();
     idt.breakpoint.set_handler_fn(breakpoint_handler);
-    idt.double_fault.set_handler_fn(double_fault_handler);
+    unsafe {
+    idt.double_fault.set_handler_fn(double_fault_handler)
+      .set_stack_index(gdt::DOUBLE_FAULT_IST_INDEX);
+    }
     idt
   };
 }
diff --git a/src/main.rs b/src/main.rs
index 5febffc..18f9035 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,10 +1,11 @@
-#![feature(abi_x86_interrupt, asm)] 
+#![feature(abi_x86_interrupt, asm)]
 #![no_std]
 #![no_main]
 
 #[macro_use]
 mod vga_buffer;
 mod interrupts;
+mod gdt;
 
 use core::panic::PanicInfo;
 
@@ -15,21 +16,24 @@ fn panic(info: &PanicInfo) -> !{
 }
 
 pub fn init() {
+  gdt::init();
   interrupts::init_idt();
 }
 
 #[no_mangle]
 pub extern "C" fn _start() -> ! {
-
   init();
-  //x86_64::instructions::interrupts::int3();
 
-  unsafe {
-    *(0xf0f0b8b8 as *mut u64) = 10;
+  fn yolo() {
+    yolo();
   }
 
-  println!("Gamarjoba, munde: {}", 1);
-  println!("Gamarjoba, munde: {}", 2);
+  yolo();
+
+
+  for i in 1..10 {
+    println!("Gamarjoba, munde: {}", i);
+  }
   loop {}
 }