Recursively map the PML4

zion/memory/paging_util.cpp

@@ -0,0 +1,20 @@
+#include "memory/paging_util.h"
+
+#include "boot/boot_info.h"
+
+#define PRESENT_BIT 0x1
+#define READ_WRITE_BIT 0x2
+
+void InitPaging() {
+  uint64_t pml4_addr = 0;
+  asm volatile("mov %%cr3, %0;" : "=r"(pml4_addr));
+  InitializePml4(pml4_addr);
+}
+
+void InitializePml4(uint64_t pml4_physical_addr) {
+  uint64_t* pml4_virtual = reinterpret_cast<uint64_t*>(
+      boot::GetHigherHalfDirectMap() + pml4_physical_addr);
+
+  uint64_t recursive_entry = pml4_physical_addr | PRESENT_BIT | READ_WRITE_BIT;
+  pml4_virtual[0x1FE] = recursive_entry;
+}