ptos: vm: Add virtual memory related macros

Signed-off-by: Chloe M <chloe@yiffware.org>

service/ptos/head/mm/vm.h

@@ -0,0 +1,31 @@
+/*
+ * Copyright (c) 2026, Chloe M.
+ * Provided under the BSD-3 clause.
+ *
+ * Description:  Virtual memory management
+ * Author:       Chloe M.
+ */
+
+#ifndef _MM_VM_H_
+#define _MM_VM_H_ 1
+
+#include <ke/bpal.h>
+
+/*
+ * Virtual memory allocation region. This is outside the
+ * higher half direct map and thus cannot be converted with
+ * PMA_TO_VMA() / VMA_TO_PMA()
+ */
+#define VALLOC_BASE 0xFFFF804000000000
+
+/*
+ * Used to convert physical addresses to virtual addresses
+ * and vice versa only when they are within the higher half
+ * direct map.
+ */
+#define PMA_TO_VMA(PMA) \
+    PTR_OFFSET((VOID *)PMA, KeBpalLoadBase())
+#define VMA_TO_PMA(VMA) \
+    (UPTR)PTR_NOFFSET(VMA, KeBpalLoadBase())
+
+#endif  /* !_MM_VM_H_ */