1 files changed, 61 insertions, 0 deletions
diff --git a/src/shared/dtables.rs b/src/shared/dtables.rs
new file mode 100644
index 0000000..c5337fb
--- /dev/null
+++ b/src/shared/dtables.rs
@@ -0,0 +1,61 @@
+//! Functions and data-structures to load descriptor tables.
+
+use core::mem::size_of;
+
+use current::irq::IdtEntry;
+use shared::segmentation::SegmentDescriptor;
+
+/// A struct describing a pointer to a descriptor table (GDT / IDT).
+/// This is in a format suitable for giving to 'lgdt' or 'lidt'.
+#[derive(Debug)]
+#[repr(C, packed)]
+pub struct DescriptorTablePointer<Entry> {
+    /// Size of the DT.
+    pub limit: u16,
+    /// Pointer to the memory region containing the DT.
+    pub base: *const Entry,
+}
+
+impl<T> DescriptorTablePointer<T> {
+    fn new(slice: &[T]) -> Self {
+        let len = slice.len() * size_of::<T>();
+        assert!(len < 0x10000);
+        DescriptorTablePointer {
+            base: slice.as_ptr(),
+            limit: len as u16,
+        }
+    }
+}
+
+impl DescriptorTablePointer<SegmentDescriptor> {
+    pub fn new_gdtp(gdt: &[SegmentDescriptor]) -> Self {
+        let mut p = Self::new(gdt);
+        p.limit -= 1;
+        p
+    }
+    pub fn new_ldtp(ldt: &[SegmentDescriptor]) -> Self {
+        Self::new(ldt)
+    }
+}
+
+impl DescriptorTablePointer<IdtEntry> {
+    pub fn new_idtp(idt: &[IdtEntry]) -> Self {
+        Self::new(idt)
+    }
+}
+
+
+/// Load GDT table.
+pub unsafe fn lgdt(gdt: &DescriptorTablePointer<SegmentDescriptor>) {
+    asm!("lgdt ($0)" :: "r" (gdt) : "memory");
+}
+
+/// Load LDT table.
+pub unsafe fn lldt(ldt: &DescriptorTablePointer<SegmentDescriptor>) {
+    asm!("lldt ($0)" :: "r" (ldt) : "memory");
+}
+
+/// Load IDT table.
+pub unsafe fn lidt(idt: &DescriptorTablePointer<IdtEntry>) {
+    asm!("lidt ($0)" :: "r" (idt) : "memory");
+}