changed page allocation to happen on page fault for performance reasons

kernel/src/arch/x86_64/interrupts.rs

@@ -1,7 +1,10 @@
+use libk::drivers::memory::{FRAME_ALLOCATOR, OFFSET_PAGE_TABLE};
 use libk::prelude::*;
 use pic8259::ChainedPics;
 use x86_64::registers::control::Cr2;
 use x86_64::structures::idt::{InterruptDescriptorTable, InterruptStackFrame, PageFaultErrorCode};
+use x86_64::structures::paging::mapper::MapperFlushAll;
+use x86_64::structures::paging::{FrameAllocator, Mapper, Page, PageTableFlags, Size4KiB};
 
 use spin::{Lazy, Mutex};
 
@@ -52,12 +55,19 @@ impl InterruptIndex {
 
 pub fn init_idt() {
     IDT.load();
-    // enable_apic();
-    // TODO: fix apic
-    // unsafe {
-    //     PICS.lock().initialize();
-    //     PICS.lock().write_masks(0xfc, 0xff);
-    // }
+}
+
+pub fn enable_pic() {
+    unsafe {
+        PICS.lock().initialize();
+        PICS.lock().write_masks(0xfc, 0xff);
+    }
+}
+
+pub fn disable_pic() {
+    unsafe {
+        PICS.lock().disable();
+    }
 }
 
 extern "x86-interrupt" fn breakpoint_handler(stack_frame: InterruptStackFrame) {
@@ -118,10 +128,28 @@ extern "x86-interrupt" fn page_fault_handler(
     stack_frame: InterruptStackFrame,
     error_code: PageFaultErrorCode,
 ) {
-    serial_println!("Exception: Page Fault");
-    serial_println!("Accessed Address: {:?}", Cr2::read());
-    serial_println!("Error Code: {:?}", error_code);
-    serial_println!("{:#?}", stack_frame);
+    // serial_println!("Exception: Page Fault");
+    // serial_println!("Accessed Address: {:?}", Cr2::read());
+    // serial_println!("Error Code: {:?}", error_code);
+    // serial_println!("{:#?}", stack_frame);
 
-    panic!("page fault");
+    if let Some(frame_allocator) = FRAME_ALLOCATOR.get() {
+        let mut f = frame_allocator.lock();
+
+        let frame = f.allocate_frame().unwrap();
+        let flags = PageTableFlags::PRESENT | PageTableFlags::WRITABLE;
+        let page: Page<Size4KiB> = Page::containing_address(Cr2::read().unwrap());
+
+        unsafe {
+            let mut mapper = OFFSET_PAGE_TABLE.get().unwrap().lock();
+
+            match mapper.map_to(page, frame, flags, &mut *f) {
+                Ok(_) => {}
+                Err(why) => panic!("failed to map page: {:?}", why),
+            }
+        }
+        MapperFlushAll::new().flush_all();
+    } else {
+        panic!("failed to get frame allocator");
+    }
 }