Add tests to ensure correct constant calculation

src/arch/mod.rs

@@ -19,11 +19,14 @@ pub trait Arch {
 
     const PAGE_SIZE: usize = 1 << Self::PAGE_SHIFT;
     const PAGE_OFFSET_MASK: usize = Self::PAGE_SIZE - 1;
-    const PAGE_ADDRESS_MASK: usize = !Self::PAGE_OFFSET_MASK;
+    const PAGE_ADDRESS_SHIFT: usize = Self::PAGE_LEVELS * Self::PAGE_ENTRY_SHIFT + Self::PAGE_SHIFT;
+    const PAGE_ADDRESS_SIZE: usize = 1 << Self::PAGE_ADDRESS_SHIFT;
+    const PAGE_ADDRESS_MASK: usize = Self::PAGE_ADDRESS_SIZE - 1 - Self::PAGE_OFFSET_MASK;
     const PAGE_ENTRY_SIZE: usize = 1 << (Self::PAGE_SHIFT - Self::PAGE_ENTRY_SHIFT);
     const PAGE_ENTRIES: usize = 1 << Self::PAGE_ENTRY_SHIFT;
     const PAGE_ENTRY_MASK: usize = Self::PAGE_ENTRIES - 1;
 
+    //TODO: allow this to differ from page address mask
     const ENTRY_ADDRESS_MASK: usize = Self::PAGE_ADDRESS_MASK;
     const ENTRY_FLAGS_MASK: usize = !Self::ENTRY_ADDRESS_MASK;
 

src/arch/x86_64.rs

@@ -45,3 +45,24 @@ impl Arch for X8664Arch {
         unimplemented!();
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use crate::Arch;
+    use super::X8664Arch;
+
+    #[test]
+    fn constants() {
+        assert_eq!(X8664Arch::PAGE_SIZE, 4096);
+        assert_eq!(X8664Arch::PAGE_OFFSET_MASK, 0xFFF);
+        assert_eq!(X8664Arch::PAGE_ADDRESS_SHIFT, 48);
+        assert_eq!(X8664Arch::PAGE_ADDRESS_SIZE, 0x0001_0000_0000_0000);
+        assert_eq!(X8664Arch::PAGE_ADDRESS_MASK, 0x0000_FFFF_FFFF_F000);
+        assert_eq!(X8664Arch::PAGE_ENTRY_SIZE, 8);
+        assert_eq!(X8664Arch::PAGE_ENTRIES, 512);
+        assert_eq!(X8664Arch::PAGE_ENTRY_MASK, 0x1FF);
+
+        assert_eq!(X8664Arch::ENTRY_ADDRESS_MASK, 0x0000_FFFF_FFFF_F000);
+        assert_eq!(X8664Arch::ENTRY_FLAGS_MASK, 0xFFFF_0000_0000_0FFF);
+    }
+}