mm: kill current task on usermode pagefault and fix destroy_page_dir destroying kernel space mappings

src/kernel/isr.c

@@ -101,6 +101,13 @@ void handle_page_fault(uint32_t error_code, uint32_t faulting_address)
 
     printf("ERR: 0x%X\n", error_code);
 
+    if (user) {
+        printf("page fault, killing task %x\n", current->pid);
+        task_kill(current);
+        asm volatile("sti");
+        while (1) {}
+    }
+
     asm("hlt");
 }
 

src/mm/paging.c

@@ -169,7 +169,7 @@ void destroy_page_dir(uint32_t* page_dir_virt) {
 
     // Iterate through user-space page directory entries (PDEs 0-767).
     // Kernel space (768+) is shared and should not be freed.
-    for (int i = 0; i < 768; i++) {
+    for (int i = 1; i < 768; i++) {
         uint32_t pde = page_dir_virt[i];
 
         // Check if the page directory entry is present