docs: add repr guarantees for address types, pages, and frames

Author: mkroening

src/addr.rs

@@ -28,6 +28,10 @@ const ADDRESS_SPACE_SIZE: u64 = 0x1_0000_0000_0000;
 /// On `x86_64`, only the 48 lower bits of a virtual address can be used. The top 16 bits need
 /// to be copies of bit 47, i.e. the most significant bit. Addresses that fulfil this criterion
 /// are called “canonical”. This type guarantees that it always represents a canonical address.
+///
+/// # Representation
+///
+/// This struct has the same representation as a [`u64`].
 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
 #[repr(transparent)]
 pub struct VirtAddr(u64);
@@ -41,6 +45,10 @@ pub struct VirtAddr(u64);
 ///
 /// On `x86_64`, only the 52 lower bits of a physical address can be used. The top 12 bits need
 /// to be zero. This type guarantees that it always represents a valid physical address.
+///
+/// # Representation
+///
+/// This struct has the same representation as a [`u64`].
 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
 #[repr(transparent)]
 pub struct PhysAddr(u64);

src/structures/paging/frame.rs

@@ -8,6 +8,10 @@ use core::marker::PhantomData;
 use core::ops::{Add, AddAssign, Sub, SubAssign};
 
 /// A physical memory frame.
+///
+/// # Representation
+///
+/// This struct has the same representation as a [`u64`].
 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
 #[repr(transparent)]
 pub struct PhysFrame<S: PageSize = Size4KiB> {

src/structures/paging/page.rs

@@ -62,6 +62,10 @@ impl PageSize for Size1GiB {
 impl Sealed for super::Size1GiB {}
 
 /// A virtual memory page.
+///
+/// # Representation
+///
+/// This struct has the same representation as a [`u64`].
 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
 #[repr(transparent)]
 pub struct Page<S: PageSize = Size4KiB> {