Rename the src directory to kernel.

kernel/arch/x86_64/tss.rs

@@ -0,0 +1,22 @@
+/// The Task State Segment.
+#[repr(C, packed)]
+#[derive(Debug, Default, Clone)]
+pub struct Tss {
+    /// Reserved.
+    pub _reserved1: u32,
+    /// The stack-pointers (reg RSP) for the IO privilege level 0 through 2.
+    pub rsp: [u64; 3],
+    /// Reserved.
+    pub _reserved2: u32,
+    /// Reserved.
+    pub _reserved3: u32,
+    pub ist: [u64; 7],
+    /// Reserved.
+    pub _reserved4: u32,
+    /// Reserved.
+    pub _reserved5: u32,
+    // Reserved.
+    pub reserved6: u16,
+    /// The offset to the IOPB.
+    pub iomap_base: u16,
+}