Create and load a static TSS and GDT

src/interrupts/mod.rs

@@ -2,6 +2,7 @@ use x86_64::VirtualAddress;
 use x86_64::structures::idt::{Idt, ExceptionStackFrame};
 use x86_64::structures::tss::TaskStateSegment;
 use memory::MemoryController;
+use spin::Once;
 
 mod gdt;
 
@@ -14,15 +15,30 @@ lazy_static! {
     };
 }
 
+static TSS: Once<TaskStateSegment> = Once::new();
+static GDT: Once<gdt::Gdt> = Once::new();
+
 const DOUBLE_FAULT_IST_INDEX: usize = 0;
 
 pub fn init(memory_controller: &mut MemoryController) {
     let double_fault_stack = memory_controller.alloc_stack(1)
         .expect("could not allocate double fault stack");
 
-    let mut tss = TaskStateSegment::new();
-    tss.interrupt_stack_table[DOUBLE_FAULT_IST_INDEX] = VirtualAddress(
-        double_fault_stack.top());
+    let tss = TSS.call_once(|| {
+        let mut tss = TaskStateSegment::new();
+        tss.interrupt_stack_table[DOUBLE_FAULT_IST_INDEX] = VirtualAddress(
+            double_fault_stack.top());
+        tss
+    });
+
+    let gdt = GDT.call_once(|| {
+        let mut gdt = gdt::Gdt::new();
+        let code_selector = gdt.add_entry(gdt::Descriptor::
+                            kernel_code_segment());
+        let tss_selector = gdt.add_entry(gdt::Descriptor::tss_segment(&tss));
+        gdt
+    });
+    gdt.load();
 
     IDT.load();
 }