feat: docs & ARCH 2.2, 2.3, 2.4

kernel/src/mem/address.rs

@@ -1,3 +1,19 @@
+use core::sync::atomic::{AtomicU64, Ordering};
+
+static HHDM_OFFSET: AtomicU64 = AtomicU64::new(0);
+
+/// Store the Higher-Half Direct Map offset obtained from the bootloader.
+/// Must be called once during early boot, before any address translation.
+pub fn init_hhdm(offset: u64) {
+    HHDM_OFFSET.store(offset, Ordering::Release);
+}
+
+/// Return the HHDM offset (kernel virtual base for physical memory).
+#[inline]
+pub fn get_hhdm() -> u64 {
+    HHDM_OFFSET.load(Ordering::Relaxed)
+}
+
 #[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
 #[repr(transparent)]
 pub struct PhysAddr(pub u64);
@@ -8,8 +24,8 @@ pub struct VirtAddr(pub u64);
 
 impl PhysAddr {
     /// Convert physical address to virtual via HHDM offset
-    pub fn to_virt(self, hhdm_offset: u64) -> VirtAddr {
-        VirtAddr(self.0 + hhdm_offset)
+    pub fn to_virt(self) -> VirtAddr {
+        VirtAddr(self.0 + get_hhdm())
     }
     
     #[allow(dead_code)]
@@ -24,9 +40,10 @@ impl PhysAddr {
 
 impl VirtAddr {
     #[allow(dead_code)]
-    pub fn to_phys(self, hhdm_offset: u64) -> Option<PhysAddr> {
-        if self.0 < hhdm_offset { return None; }
-        Some(PhysAddr(self.0 - hhdm_offset))
+    pub fn to_phys(self) -> Option<PhysAddr> {
+        let hhdm = get_hhdm();
+        if self.0 < hhdm { return None; }
+        Some(PhysAddr(self.0 - hhdm))
     }
 
     #[allow(dead_code)]