setup GDT & fixed a deadlock

kernel/src/arch/x86_64/gdt.rs

@@ -1,4 +1,12 @@
-use x86_64::{structures::tss::TaskStateSegment, VirtAddr};
+use x86_64::{
+    instructions::tables::load_tss,
+    registers::segmentation::{Segment, CS, DS, ES, SS},
+    structures::{
+        gdt::{Descriptor, GlobalDescriptorTable, SegmentSelector},
+        tss::TaskStateSegment,
+    },
+    VirtAddr,
+};
 
 use spin::Lazy;
 
@@ -16,3 +24,46 @@ static TSS: Lazy<TaskStateSegment> = Lazy::new(|| {
     };
     tss
 });
+
+static GDT: Lazy<(GlobalDescriptorTable, Selectors)> = Lazy::new(|| {
+    let mut gdt = GlobalDescriptorTable::new();
+    let code_selector = gdt.append(Descriptor::kernel_code_segment());
+    let data_selector = gdt.append(Descriptor::kernel_data_segment());
+
+    let user_code_selector = gdt.append(Descriptor::user_code_segment());
+    let user_data_selector = gdt.append(Descriptor::user_data_segment());
+
+    let tss_selector = gdt.append(Descriptor::tss_segment(&TSS));
+
+    (
+        gdt,
+        Selectors {
+            code_selector,
+            data_selector,
+            user_code_selector,
+            user_data_selector,
+            tss_selector,
+        },
+    )
+});
+
+struct Selectors {
+    code_selector: SegmentSelector,
+    data_selector: SegmentSelector,
+    user_code_selector: SegmentSelector,
+    user_data_selector: SegmentSelector,
+    tss_selector: SegmentSelector,
+}
+
+pub fn init() {
+    GDT.0.load();
+
+    unsafe {
+        CS::set_reg(GDT.1.code_selector);
+        load_tss(GDT.1.tss_selector);
+
+        DS::set_reg(self::GDT.1.data_selector);
+        ES::set_reg(self::GDT.1.data_selector);
+        SS::set_reg(self::GDT.1.data_selector);
+    }
+}