tasking: continue working on page directory switching

src/mm/paging.c

@@ -123,6 +123,29 @@ void set_page_dir(uint32_t new_page_dir) {
     asm volatile("mov %0, %%cr3" : : "r" (new_page_dir));
 }
 
+uint32_t phys_to_virt(uint32_t phys)
+{
+    return phys+0xC0000000;
+}
+
+uint32_t create_page_dir()
+{
+    void* ppp = alloc_page();
+    memset(ppp, 0, 0x1000);
+
+    uint32_t* current_pd = (uint32_t*)0xFFFFF000;  // Current PD (self-mapped)
+    uint32_t* new_pd = (uint32_t*)phys_to_virt((uint32_t)ppp);
+
+    for(int i = 768; i < 1023; i++)
+    {
+        new_pd[i] = current_pd[i];
+    }
+
+    new_pd[1023] = (uint32_t)ppp | 0x03;  // Present + Read/Write
+
+    return (uint32_t)new_pd;
+}
+
 void enablePaging() {
     asm volatile (
         "mov %%cr0, %%eax\n"