ptos/amd64: mmu: Add virtual address space helpers

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

service/ptos/arch/amd64/cpu/mmu.c

@@ -0,0 +1,40 @@
+/*
+ * Copyright (c) 2026, Chloe M.
+ * Provided under the BSD-3 clause.
+ *
+ * Description: Platform MMU HAL interface
+ * Author:      Chloe M.
+ */
+
+#include <hal/mmu.h>
+#include <ptdef.h>
+
+VOID
+HalMmuReadVas(MMU_VAS *Result)
+{
+    if (Result == NULL) {
+        return;
+    }
+
+    ASMV(
+        "mov %%cr3, %0"
+        : "=r" (Result->Cr3)
+        :
+        : "memory"
+    );
+}
+
+VOID
+HalMmuWriteVas(const MMU_VAS *Vas)
+{
+    if (Vas == NULL) {
+        return;
+    }
+
+    ASMV(
+        "mov %0, %%cr3"
+        :
+        : "r" (Vas->Cr3)
+        : "memory"
+    );
+}

service/ptos/head/hal/mmu.h

@@ -0,0 +1,31 @@
+/*
+ * Copyright (c) 2026, Chloe M.
+ * Provided under the BSD-3 clause.
+ *
+ * Description: Platform MMU HAL interface
+ * Author:      Chloe M.
+ */
+
+#ifndef _HAL_MMU_H_
+#define _HAL_MMU_H_ 1
+
+#include <hal/vas.h>
+#include <ptdef.h>
+
+/*
+ * Read the current virtual address space into an
+ * MMU_VAS descriptor.
+ *
+ * @Result: Result is written here
+ */
+VOID HalMmuReadVas(MMU_VAS *Result);
+
+/*
+ * Write a virtual address space into the current context
+ * from an MMU_VAS descriptor
+ *
+ * @Vas:  VAS to write to current context
+ */
+VOID HalMmuWriteVas(const MMU_VAS *Vas);
+
+#endif  /* !_HAL_MMU_H_ */