Implement TSS

kernel/src/cpu/gdt.rs

@@ -11,9 +11,31 @@ struct GDTEntry {
     flags: u8,
     base_high: u8,
 }
+#[repr(C, packed)]
+struct TSS {
+    reserved1: u32,
+    rsp: [u64; 3],
+    reserved2: u64,
+    ist: [u64; 7],
+    reserved3: u64,
+    reserved4: u16,
+    iopb_offset: u16,
+}
+#[repr(C)]
+struct TSSDescriptor {
+    limit_low: u16,
+    base_low: u16,
+    base_middle: u8,
+    access: u8,
+    flags: u8,
+    base_high: u8,
+    base_upper: u32,
+    reserved: u32,
+}
 #[repr(C)]
 struct GDT {
     entries: [GDTEntry; 5],
+    tss: TSSDescriptor,
 }
 #[repr(C, packed)]
 struct GDTDescriptor {
@@ -22,6 +44,15 @@ struct GDTDescriptor {
 }
 
 pub fn setup_gdt() {
+    let tss = Box::leak(Box::new(TSS {
+        reserved1: 0,
+        rsp: [0; 3],
+        reserved2: 0,
+        ist: [0; 7],
+        reserved3: 0,
+        reserved4: 0,
+        iopb_offset: size_of::<TSS>() as u16,
+    }));
     let gdt = Box::leak(Box::new(GDT {
         entries: [
             GDTEntry {
@@ -65,6 +96,16 @@ pub fn setup_gdt() {
                 base_high: 0,
             },
         ],
+        tss: TSSDescriptor {
+            limit_low: (size_of::<TSS>() - 1) as u16,
+            base_low: tss as *const TSS as u16,
+            base_middle: (tss as *const TSS as u64 >> 16) as u8,
+            access: 0x89,
+            flags: ((size_of::<TSS>() - 1) >> 16) as u8,
+            base_high: (tss as *const TSS as u64 >> 24) as u8,
+            base_upper: (tss as *const TSS as u64 >> 32) as u32,
+            reserved: 0,
+        },
     }));
     let gdt_descriptor = Box::leak(Box::new(GDTDescriptor {
         limit: (size_of::<GDT>() - 1) as u16,
@@ -83,6 +124,8 @@ pub fn setup_gdt() {
             mov %ax, %fs
             mov %ax, %gs
             mov %ax, %ss
+            mov $0x28, %ax
+            ltr %ax
         ", in(reg) gdt_descriptor, out("rax") _, options(att_syntax));
     }
 }