Provide null segment selector as associated constant on SegmentSelector

Author: Michael Jenny

src/registers/segmentation.rs

@@ -77,6 +77,10 @@ impl SegmentSelector {
         SegmentSelector(index << 3 | (rpl as u16))
     }
 
+    /// Can be used as a selector into a non-existent segment and assigned to segment registers,
+    /// e.g. data segment register in ring 0
+    pub const NULL: Self = Self::new(0, PrivilegeLevel::Ring0);
+
     /// Returns the GDT index.
     #[inline]
     pub fn index(self) -> u16 {

src/structures/gdt.rs

@@ -93,14 +93,6 @@ impl GlobalDescriptorTable {
         &self.table[..self.len]
     }
 
-    /// Get the GDT's null segment descriptor as selector.
-    ///
-    /// Can be used as a selector into a non-existent segment and assigned to segment registers.
-    #[inline]
-    pub fn null_segment_selector(&self) -> SegmentSelector {
-        SegmentSelector::new(0u16, PrivilegeLevel::from_u16(0u16))
-    }
-
     /// Adds the given segment descriptor to the GDT, returning the segment selector.
     ///
     /// Panics if the GDT doesn't have enough free entries to hold the Descriptor.