ptos/amd64+hal: Add virtual address space forking

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

service/ptos/mm/vm.c

@@ -35,6 +35,9 @@ static USIZE PageSizeTable[] = {
     [PAGESIZE_4K] = 0x1000
 };
 
+/* Kernel VAS */
+static MMU_VAS KVas;
+
 /* Bump pointer and vad tree */
 static UPTR VallocBump = VALLOC_BASE;
 static MM_VAD_TREE VadTree;
@@ -138,7 +141,15 @@ MmVmInit(VOID)
 
     HalMmuReadVas(&VasCurrent);
     MmVadTreeInit(&VadTree);
+    Status = HalMmuForkVas(&VasCurrent, &KVas);
+    if (PT_ERROR(Status)) {
+        KeBugCheck(
+            BUGCHECK_OOM,
+            "failed to allocate kernel vas\n"
+        );
+    }
 
+    HalMmuWriteVas(&KVas);
     VirtualStart = VallocBump;
     VallocBump += INITIAL_VALLOC_PAGES * PAGESIZE;
     VirtualEnd = VallocBump;
@@ -152,7 +163,7 @@ MmVmInit(VOID)
 
         PhysicalBase = PFN_TO_ADDRESS(Pfn);
         Status = HalMmuMapPage(
-            &VasCurrent,
+            &KVas,
             VirtualStart + Off,
             PhysicalBase,
             PAGE_READ| PAGE_WRITE,