Add errors::SelectorError

This interprets the values of the selector error during #GP.

Signed-off-by: Nathaniel McCallum <[email protected]>

Author: npmccallum

src/errors.rs

@@ -1,5 +1,7 @@
 //! This module contains errors and exception types.
 
+use bit_field::BitField;
+
 /// Exception Error Codes
 ///
 /// This structure is defined by the following manual sections:
@@ -78,3 +80,71 @@ pub enum Exception {
     /// Security Exception
     Security = 0x1E,
 }
+
+/// The index in a selector error
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub enum SelectorIndex {
+    /// An IDT selector
+    Idt(u16),
+
+    /// A GDT selector
+    Gdt(u16),
+
+    /// An LDT selector
+    Ldt(u16),
+}
+
+/// A selector error
+///
+/// This structure is defined by the following manual sections:
+///   * AMD Volume 2: 8.4.1
+///   * Intel Volume 3A: 6.13
+#[derive(Copy, Clone, Debug)]
+#[repr(transparent)]
+pub struct SelectorError(u32);
+
+impl SelectorError {
+    /// Whether or not the fault was external to the CPU.
+    #[inline]
+    pub fn external(self) -> bool {
+        self.0.get_bit(0)
+    }
+
+    /// Returns the selector index.
+    #[inline]
+    pub fn index(self) -> SelectorIndex {
+        let index = self.0.get_bits(3..16) as u16;
+
+        if self.0.get_bit(1) {
+            SelectorIndex::Idt(index)
+        } else if self.0.get_bit(2) {
+            SelectorIndex::Ldt(index)
+        } else {
+            SelectorIndex::Gdt(index)
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn selector() {
+        let se = SelectorError(0b0101010101010101_0101010101010101);
+        assert_eq!(se.external(), true);
+        assert_eq!(se.index(), SelectorIndex::Ldt(0b0101010101010));
+
+        let se = SelectorError(0b0101010101010101_0101010101010111);
+        assert_eq!(se.external(), true);
+        assert_eq!(se.index(), SelectorIndex::Idt(0b0101010101010));
+
+        let se = SelectorError(0b0101010101010101_0101010101010011);
+        assert_eq!(se.external(), true);
+        assert_eq!(se.index(), SelectorIndex::Idt(0b0101010101010));
+
+        let se = SelectorError(0b0101010101010101_0101010101010001);
+        assert_eq!(se.external(), true);
+        assert_eq!(se.index(), SelectorIndex::Gdt(0b0101010101010));
+    }
+}