allocation working

os/.cargo/config.toml

@@ -1,5 +1,5 @@
 [unstable]
-build-std = ["core", "compiler_builtins"]
+build-std = ["core", "compiler_builtins", "alloc"]
 build-std-features = ["compiler-builtins-mem"]
 
 [build]

os/Cargo.toml

@@ -14,6 +14,7 @@ volatile = "0.2.6"
 uart_16550 = "0.2.0"
 pic8259 = "0.10.4"
 pc-keyboard = "0.7.0"
+linked_list_allocator = "0.9.0"
 lazy_static = { version = "1.0", features = ["spin_no_std"] }
 bootloader = { version = "0.9.23", features = ["map_physical_memory"]}
 

os/src/allocator.rs

@@ -0,0 +1,43 @@
+use x86_64::{
+    structures::paging::{
+        mapper::MapToError, FrameAllocator, Mapper, Page, PageTableFlags, Size4KiB,
+    },
+    VirtAddr,
+};
+use linked_list_allocator::LockedHeap;
+
+#[global_allocator]
+static ALLOCATOR: LockedHeap = LockedHeap::empty();
+
+pub fn init_heap(
+    mapper: &mut impl Mapper<Size4KiB>,
+    frame_allocator: &mut impl FrameAllocator<Size4KiB>,
+) -> Result<(), MapToError<Size4KiB>> {
+    let page_range = {
+        let heap_start = VirtAddr::new(HEAP_START as u64);
+        let heap_end = heap_start + HEAP_SIZE - 1u64;
+        let heap_start_page = Page::containing_address(heap_start);
+        let heap_end_page = Page::containing_address(heap_end);
+        Page::range_inclusive(heap_start_page, heap_end_page)
+    };
+
+    for page in page_range {
+        let frame = frame_allocator
+            .allocate_frame()
+            .ok_or(MapToError::FrameAllocationFailed)?;
+        let flags = PageTableFlags::PRESENT | PageTableFlags::WRITABLE;
+        unsafe {
+            mapper.map_to(page, frame, flags, frame_allocator)?.flush()
+        };
+    }
+
+    // Initialize the allocator with the correct bounds
+    unsafe {
+        ALLOCATOR.lock().init(HEAP_START, HEAP_SIZE);
+    }
+
+    Ok(())
+}
+
+pub const HEAP_START: usize = 0x_4444_4444_0000;
+pub const HEAP_SIZE: usize = 100 * 1024; // 100 KiB

os/src/lib.rs

@@ -5,6 +5,8 @@
 #![test_runner(crate::test_runner)]
 #![reexport_test_harness_main = "test_main"]
 
+extern crate alloc;
+
 #[cfg(test)]
 use bootloader::{entry_point, BootInfo};
 
@@ -13,6 +15,7 @@ pub mod interrupts;
 pub mod serial;
 pub mod vga;
 pub mod memory;
+pub mod allocator;
 
 pub fn init() {
     gdt::init();

os/src/main.rs

@@ -4,34 +4,49 @@
 #![test_runner(knarkos::test_runner)]
 #![reexport_test_harness_main = "test_main"]
 
+extern crate alloc;
+
 use knarkos::println;
 use bootloader::{BootInfo, entry_point};
+use alloc::{boxed::Box, vec, vec::Vec, rc::Rc};
 
 entry_point!(kernel_main);
 
 fn kernel_main(boot_info: &'static BootInfo) -> ! {
-    use knarkos::memory;
+    use knarkos::{memory, allocator};
     use knarkos::memory::BootInfoFrameAllocator;
-    use x86_64::{structures::paging::Page, VirtAddr}; // new import
+    use x86_64::VirtAddr;
 
     // Initialize operating system
     knarkos::init();
     println!("Hello, world!");
 
-    // Read page tables
+    // Setup heap
     let phys_mem_offset = VirtAddr::new(boot_info.physical_memory_offset);
     let mut mapper = unsafe { memory::init(phys_mem_offset) };
     let mut frame_allocator = unsafe {
         BootInfoFrameAllocator::init(&boot_info.memory_map)
     };
-
-    // map an unused page
-    let page = Page::containing_address(VirtAddr::new(0));
-    memory::create_example_mapping(page, &mut mapper, &mut frame_allocator);
+    allocator::init_heap(&mut mapper, &mut frame_allocator).expect("heap initialization failed");
+
+    // Heap allocation
+    // allocate a number on the heap
+    let heap_value = Box::new(41);
+    println!("heap_value at {:p}", heap_value);
+
+    // create a dynamically sized vector
+    let mut vec = Vec::new();
+    for i in 0..500 {
+        vec.push(i);
+    }
+    println!("vec at {:p}", vec.as_slice());
 
-    // write the string `New!` to the screen through the new mapping
-    let page_ptr: *mut u64 = page.start_address().as_mut_ptr();
-    unsafe { page_ptr.offset(400).write_volatile(0x_f021_f077_f065_f04e)};
+    // create a reference counted vector -> will be freed when count reaches 0
+    let reference_counted = Rc::new(vec![1, 2, 3]);
+    let cloned_reference = reference_counted.clone();
+    println!("current reference count is {}", Rc::strong_count(&cloned_reference));
+    core::mem::drop(reference_counted);
+    println!("reference count is {} now", Rc::strong_count(&cloned_reference));
 
     #[cfg(test)]
     test_main();