error if base =/= expected base

Author: Restioson

src/structures/gdt.rs

@@ -320,16 +320,23 @@ impl Descriptor {
             return Err(InvalidIoMap::TooLong { len: iomap.len() })
         }
 
-        let distance = iomap.as_ptr() as usize - tss as *const _ as usize;
-        if distance > 0xdfff {
-            return Err(InvalidIoMap::TooFarFromTss { distance })
+        let base = iomap.as_ptr() as usize - tss as *const _ as usize;
+        if base > 0xdfff {
+            return Err(InvalidIoMap::TooFarFromTss { distance: base })
         }
 
         let last_byte = *iomap.last().unwrap_or(&0xff);
         if last_byte != 0xff {
             return Err(InvalidIoMap::InvalidTerminatingByte { byte: last_byte })
         }
 
+        if tss.iomap_base != base as u16 {
+            return Err(InvalidIoMap::InvalidBase {
+                expected: base as u16,
+                got: tss.iomap_base
+            });
+        }
+
         // SAFETY: all invariants checked above
         Ok(unsafe { Self::tss_segment_raw(tss, iomap.len() as u16) })
     }

src/structures/tss.rs

@@ -55,4 +55,9 @@ pub enum InvalidIoMap {
     TooLong {
         len: usize
     },
+    /// The `iomap_base` in the `TaskStateSegment` struct was not what was expected.
+    InvalidBase {
+        expected: u16,
+        got: u16,
+    }
 }