improve panic messages for arithmetic operations

Previously, the error message didn't make it immediately obvious what
went wrong.
Let's be a bit more explicit.
Note that "attempt to add/subtract with overflow" is the panic message
used by Rust for normal arithmetic operations.

Author: Freax13

src/addr.rs

@@ -366,7 +366,12 @@ impl Add<u64> for VirtAddr {
     type Output = Self;
     #[inline]
     fn add(self, rhs: u64) -> Self::Output {
-        VirtAddr::new(self.0.checked_add(rhs).unwrap())
+        VirtAddr::try_new(
+            self.0
+                .checked_add(rhs)
+                .expect("attempt to add with overflow"),
+        )
+        .expect("attempt to add resulted in non-canonical virtual address")
     }
 }
 
@@ -381,7 +386,12 @@ impl Sub<u64> for VirtAddr {
     type Output = Self;
     #[inline]
     fn sub(self, rhs: u64) -> Self::Output {
-        VirtAddr::new(self.0.checked_sub(rhs).unwrap())
+        VirtAddr::try_new(
+            self.0
+                .checked_sub(rhs)
+                .expect("attempt to subtract with overflow"),
+        )
+        .expect("attempt to subtract resulted in non-canonical virtual address")
     }
 }
 
@@ -396,7 +406,9 @@ impl Sub<VirtAddr> for VirtAddr {
     type Output = u64;
     #[inline]
     fn sub(self, rhs: VirtAddr) -> Self::Output {
-        self.as_u64().checked_sub(rhs.as_u64()).unwrap()
+        self.as_u64()
+            .checked_sub(rhs.as_u64())
+            .expect("attempt to subtract with overflow")
     }
 }