Merge branch 'post-11' into post-12

# Conflicts:
#	README.md

Cargo.lock

@@ -1,41 +1,38 @@
 # This file is automatically @generated by Cargo.
 # It is not intended for manual editing.
-version = 4
+version = 3
 
 [[package]]
 name = "autocfg"
-version = "1.5.0"
+version = "1.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c08606f8c3cbf4ce6ec8e28fb0014a2c086708fe954eaa885384a6165172e7e8"
+checksum = "cdb031dd78e28731d87d56cc8ffef4a8f36ca26c38fe2de700543e627f8a464a"
 
 [[package]]
 name = "bit_field"
-version = "0.10.2"
+version = "0.10.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "dc827186963e592360843fb5ba4b973e145841266c1357f7180c43526f2e5b61"
+checksum = "dcb6dd1c2376d2e096796e234a70e17e94cc2d5d54ff8ce42b28cef1d0d359a4"
 
 [[package]]
 name = "bitflags"
-version = "1.3.2"
+version = "1.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "bef38d45163c2f1dde094a7dfd33ccf595c92905c8f8f4fdc18d06fb1037718a"
+checksum = "cf1de2fe8c75bc145a2f577add951f8134889b4795d47466a54a5c846d691693"
-
-[[package]]
-name = "bitflags"
-version = "2.9.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6a65b545ab31d687cff52899d4890855fec459eb6afe0da6417b8a18da87aa29"
 
 [[package]]
 name = "blog_os"
 version = "0.1.0"
 dependencies = [
  "bootloader",
+ "conquer-once",
+ "crossbeam-queue",
+ "futures-util",
  "lazy_static",
  "linked_list_allocator",
  "pc-keyboard",
  "pic8259",
- "spin 0.5.2",
+ "spin",
  "uart_16550",
  "volatile 0.2.7",
  "x86_64",
@@ -43,64 +40,142 @@ dependencies = [
 
 [[package]]
 name = "bootloader"
-version = "0.9.33"
+version = "0.9.23"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7bdfddac270bbdd45903296bc1caf29a7fdce6b326aaf0bbab7f04c5f98b7447"
+checksum = "b6e02311b16c9819e7c72866d379cdd3026c3b7b25c1edf161f548f8e887e7ff"
+
+[[package]]
+name = "cfg-if"
+version = "0.1.10"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4785bdd1c96b2a846b2bd7cc02e86b6b3dbf14e7e53446c4f54c92a361040822"
+
+[[package]]
+name = "conquer-once"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "96eb12fb69466716fbae9009d389e6a30830ae8975e170eff2d2cff579f9efa3"
+dependencies = [
+ "conquer-util",
+]
+
+[[package]]
+name = "conquer-util"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "654fb2472cc369d311c547103a1fa81d467bef370ae7a0680f65939895b1182a"
+
+[[package]]
+name = "crossbeam-queue"
+version = "0.2.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "774ba60a54c213d409d5353bda12d49cd68d14e45036a285234c8d6f91f92570"
+dependencies = [
+ "cfg-if",
+ "crossbeam-utils",
+ "maybe-uninit",
+]
+
+[[package]]
+name = "crossbeam-utils"
+version = "0.7.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c3c7c73a2d1e9fc0886a08b93e98eb643461230d5f1925e4036204d5f2e261a8"
+dependencies = [
+ "autocfg",
+ "cfg-if",
+]
+
+[[package]]
+name = "futures-core"
+version = "0.3.15"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0402f765d8a89a26043b889b26ce3c4679d268fa6bb22cd7c6aad98340e179d1"
+
+[[package]]
+name = "futures-task"
+version = "0.3.15"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8a16bef9fc1a4dddb5bee51c989e3fbba26569cbb0e31f5b303c184e3dd33dae"
+
+[[package]]
+name = "futures-util"
+version = "0.3.15"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "feb5c238d27e2bf94ffdfd27b2c29e3df4a68c4193bb6427384259e2bf191967"
+dependencies = [
+ "autocfg",
+ "futures-core",
+ "futures-task",
+ "pin-project-lite",
+ "pin-utils",
+]
 
 [[package]]
 name = "lazy_static"
-version = "1.5.0"
+version = "1.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "bbd2bcb4c963f2ddae06a2efc7e9f3591312473c50c6685e1f298068316e66fe"
+checksum = "e2abad23fbc42b3700f2f279844dc832adb2b2eb069b2df918f455c4e18cc646"
 dependencies = [
- "spin 0.9.8",
+ "spin",
 ]
 
 [[package]]
 name = "linked_list_allocator"
-version = "0.9.1"
+version = "0.9.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "549ce1740e46b291953c4340adcd74c59bcf4308f4cac050fd33ba91b7168f4a"
+checksum = "d0b725207570aa16096962d0b20c79f8a543df2280bd3c903022b9b0b4d7ea68"
 dependencies = [
  "spinning_top",
 ]
 
 [[package]]
 name = "lock_api"
-version = "0.4.13"
+version = "0.4.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "96936507f153605bddfcda068dd804796c84324ed2510809e5b2a624c81da765"
+checksum = "0382880606dff6d15c9476c416d18690b72742aa7b605bb6dd6ec9030fbf07eb"
 dependencies = [
- "autocfg",
  "scopeguard",
 ]
 
 [[package]]
-name = "pc-keyboard"
+name = "maybe-uninit"
-version = "0.7.0"
+version = "2.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ed089a1fbffe3337a1a345501c981f1eb1e47e69de5a40e852433e12953c3174"
+checksum = "60302e4db3a61da70c0cb7991976248362f30319e88850c487b9b95bbf059e00"
+
+[[package]]
+name = "pc-keyboard"
+version = "0.5.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5c6f2d937e3b8d63449b01401e2bae4041bc9dd1129c2e3e0d239407cf6635ac"
 
 [[package]]
 name = "pic8259"
-version = "0.10.4"
+version = "0.10.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "cb844b5b01db1e0b17938685738f113bfc903846f18932b378bc0eabfa40e194"
+checksum = "08cc920d83ee33c0f9b73aa441e75468bf2d10c959a3eb6260cf720b05ac91a1"
 dependencies = [
  "x86_64",
 ]
 
 [[package]]
-name = "rustversion"
+name = "pin-project-lite"
-version = "1.0.22"
+version = "0.2.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b39cdef0fa800fc44525c84ccb54a029961a8215f9619753635a9c0d2538d46d"
+checksum = "dc0e1f259c92177c30a4c9d177246edd0a3568b25756a977d0632cf8fa37e905"
+
+[[package]]
+name = "pin-utils"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8b870d8c151b6f2fb93e84a13146138f05d02ed11c7e7c54f8826aaaf7c9f184"
 
 [[package]]
 name = "scopeguard"
-version = "1.2.0"
+version = "1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "94143f37725109f92c262ed2cf5e59bce7498c01bcc1502d7b9afe439a4e9f49"
+checksum = "d29ab0c6d3fc0ee92fe66e2d99f700eab17a8d57d1c1d3b748380fb20baa78cd"
 
 [[package]]
 name = "spin"
@@ -108,29 +183,22 @@ version = "0.5.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6e63cff320ae2c57904679ba7cb63280a3dc4613885beafb148ee7bf9aa9042d"
 
-[[package]]
-name = "spin"
-version = "0.9.8"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6980e8d7511241f8acf4aebddbb1ff938df5eebe98691418c4468d0b72a96a67"
-
 [[package]]
 name = "spinning_top"
-version = "0.2.5"
+version = "0.2.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5b9eb1a2f4c41445a3a0ff9abc5221c5fcd28e1f13cd7c0397706f9ac938ddb0"
+checksum = "75adad84ee84b521fb2cca2d4fd0f1dab1d8d026bda3c5bea4ca63b5f9f9293c"
 dependencies = [
  "lock_api",
 ]
 
 [[package]]
 name = "uart_16550"
-version = "0.2.19"
+version = "0.2.14"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "614ff2a87880d4bd4374722268598a970bbad05ced8bf630439417347254ab2e"
+checksum = "503a6c0e6d82daa87985e662d120c0176b09587c92a68db22781b28ae95405dd"
 dependencies = [
- "bitflags 1.3.2",
+ "bitflags",
- "rustversion",
  "x86_64",
 ]
 
@@ -142,18 +210,17 @@ checksum = "f6b06ad3ed06fef1713569d547cdbdb439eafed76341820fb0e0344f29a41945"
 
 [[package]]
 name = "volatile"
-version = "0.4.6"
+version = "0.4.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "442887c63f2c839b346c192d047a7c87e73d0689c9157b00b53dcc27dd5ea793"
+checksum = "e4c2dbd44eb8b53973357e6e207e370f0c1059990df850aca1eca8947cf464f0"
 
 [[package]]
 name = "x86_64"
-version = "0.14.13"
+version = "0.14.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c101112411baafbb4bf8d33e4c4a80ab5b02d74d2612331c61e8192fc9710491"
+checksum = "fb611915c917c6296d11e23f71ff1ecfe49c5766daba92cd3df52df6b58285b6"
 dependencies = [
  "bit_field",
- "bitflags 2.9.2",
+ "bitflags",
- "rustversion",
+ "volatile 0.4.4",
- "volatile 0.4.6",
 ]

Cargo.toml

@@ -2,7 +2,7 @@
 name = "blog_os"
 version = "0.1.0"
 authors = ["Philipp Oppermann <dev@phil-opp.com>"]
-edition = "2024"
+edition = "2018"
 
 [[test]]
 name = "should_panic"
@@ -13,32 +13,36 @@ name = "stack_overflow"
 harness = false
 
 [dependencies]
-bootloader = { version = "0.9", features = ["map_physical_memory"] }
+bootloader = { version = "0.9.8", features = ["map_physical_memory"]}
 volatile = "0.2.6"
 spin = "0.5.2"
 x86_64 = "0.14.2"
 uart_16550 = "0.2.0"
 pic8259 = "0.10.1"
-pc-keyboard = "0.7.0"
+pc-keyboard = "0.5.0"
 linked_list_allocator = "0.9.0"
 
 [dependencies.lazy_static]
 version = "1.0"
 features = ["spin_no_std"]
 
-[[bin]]
+[dependencies.crossbeam-queue]
-name = "blog_os"
+version = "0.2.1"
-test = true
+default-features = false
-bench = false
+features = ["alloc"]
 
+[dependencies.conquer-once]
+version = "0.2.0"
+default-features = false
+
+[dependencies.futures-util]
+version = "0.3.4"
+default-features = false
+features = ["alloc"]
 
 [package.metadata.bootimage]
 test-args = [
-    "-device",
+    "-device", "isa-debug-exit,iobase=0xf4,iosize=0x04", "-serial", "stdio",
-    "isa-debug-exit,iobase=0xf4,iosize=0x04",
+    "-display", "none"
-    "-serial",
-    "stdio",
-    "-display",
-    "none",
 ]
-test-success-exit-code = 33 # (0x10 << 1) | 1
+test-success-exit-code = 33         # (0x10 << 1) | 1

README.md

@@ -1,10 +1,10 @@
-# Blog OS (Allocator Designs)
+# Blog OS (Async/Await)
 
-[![Build Status](https://github.com/phil-opp/blog_os/workflows/Code/badge.svg?branch=post-11)](https://github.com/phil-opp/blog_os/actions?query=workflow%3A%22Code%22+branch%3Apost-11)
+[![Build Status](https://github.com/phil-opp/blog_os/workflows/Code/badge.svg?branch=post-12)](https://github.com/phil-opp/blog_os/actions?query=workflow%3A%22Code%22+branch%3Apost-12)
 
-This repository contains the source code for the [Allocator Designs][post] post of the [Writing an OS in Rust](https://os.phil-opp.com) series.
+This repository contains the source code for the [Async/Await][post] post of the [Writing an OS in Rust](https://os.phil-opp.com) series.
 
-[post]: https://os.phil-opp.com/allocator-designs/
+[post]: https://os.phil-opp.com/async-await/
 
 **Check out the [master branch](https://github.com/phil-opp/blog_os) for more information.**
 

src/allocator.rs

@@ -2,10 +2,10 @@ use alloc::alloc::{GlobalAlloc, Layout};
 use core::ptr::null_mut;
 use fixed_size_block::FixedSizeBlockAllocator;
 use x86_64::{
-    VirtAddr,
     structures::paging::{
-        FrameAllocator, Mapper, Page, PageTableFlags, Size4KiB, mapper::MapToError,
+        mapper::MapToError, FrameAllocator, Mapper, Page, PageTableFlags, Size4KiB,
     },
+    VirtAddr,
 };
 
 pub mod bump;

src/allocator/bump.rs

@@ -1,4 +1,4 @@
-use super::{Locked, align_up};
+use super::{align_up, Locked};
 use alloc::alloc::{GlobalAlloc, Layout};
 use core::ptr;
 

src/allocator/fixed_size_block.rs

@@ -44,9 +44,7 @@ impl FixedSizeBlockAllocator {
     /// heap bounds are valid and that the heap is unused. This method must be
     /// called only once.
     pub unsafe fn init(&mut self, heap_start: usize, heap_size: usize) {
-        unsafe {
+        self.fallback_allocator.init(heap_start, heap_size);
-            self.fallback_allocator.init(heap_start, heap_size);
-        }
     }
 
     /// Allocates using the fallback allocator.
@@ -93,16 +91,12 @@ unsafe impl GlobalAlloc for Locked<FixedSizeBlockAllocator> {
                 assert!(mem::size_of::<ListNode>() <= BLOCK_SIZES[index]);
                 assert!(mem::align_of::<ListNode>() <= BLOCK_SIZES[index]);
                 let new_node_ptr = ptr as *mut ListNode;
-                unsafe {
+                new_node_ptr.write(new_node);
-                    new_node_ptr.write(new_node);
+                allocator.list_heads[index] = Some(&mut *new_node_ptr);
-                    allocator.list_heads[index] = Some(&mut *new_node_ptr);
-                }
             }
             None => {
                 let ptr = NonNull::new(ptr).unwrap();
-                unsafe {
+                allocator.fallback_allocator.deallocate(ptr, layout);
-                    allocator.fallback_allocator.deallocate(ptr, layout);
-                }
             }
         }
     }

src/allocator/linked_list.rs

@@ -1,4 +1,4 @@
-use super::{Locked, align_up};
+use super::{align_up, Locked};
 use alloc::alloc::{GlobalAlloc, Layout};
 use core::{mem, ptr};
 
@@ -39,9 +39,7 @@ impl LinkedListAllocator {
     /// heap bounds are valid and that the heap is unused. This method must be
     /// called only once.
     pub unsafe fn init(&mut self, heap_start: usize, heap_size: usize) {
-        unsafe {
+        self.add_free_region(heap_start, heap_size);
-            self.add_free_region(heap_start, heap_size);
-        }
     }
 
     /// Adds the given memory region to the front of the list.
@@ -54,10 +52,8 @@ impl LinkedListAllocator {
         let mut node = ListNode::new(size);
         node.next = self.head.next.take();
         let node_ptr = addr as *mut ListNode;
-        unsafe {
+        node_ptr.write(node);
-            node_ptr.write(node);
+        self.head.next = Some(&mut *node_ptr)
-            self.head.next = Some(&mut *node_ptr);
-        }
     }
 
     /// Looks for a free region with the given size and alignment and removes
@@ -132,9 +128,7 @@ unsafe impl GlobalAlloc for Locked<LinkedListAllocator> {
             let alloc_end = alloc_start.checked_add(size).expect("overflow");
             let excess_size = region.end_addr() - alloc_end;
             if excess_size > 0 {
-                unsafe {
+                allocator.add_free_region(alloc_end, excess_size);
-                    allocator.add_free_region(alloc_end, excess_size);
-                }
             }
             alloc_start as *mut u8
         } else {
@@ -146,6 +140,6 @@ unsafe impl GlobalAlloc for Locked<LinkedListAllocator> {
         // perform layout adjustments
         let (size, _) = LinkedListAllocator::size_align(layout);
 
-        unsafe { self.lock().add_free_region(ptr as usize, size) }
+        self.lock().add_free_region(ptr as usize, size)
     }
 }

src/gdt.rs

@@ -1,7 +1,7 @@
 use lazy_static::lazy_static;
-use x86_64::VirtAddr;
 use x86_64::structures::gdt::{Descriptor, GlobalDescriptorTable, SegmentSelector};
 use x86_64::structures::tss::TaskStateSegment;
+use x86_64::VirtAddr;
 
 pub const DOUBLE_FAULT_IST_INDEX: u16 = 0;
 
@@ -12,7 +12,7 @@ lazy_static! {
             const STACK_SIZE: usize = 4096 * 5;
             static mut STACK: [u8; STACK_SIZE] = [0; STACK_SIZE];
 
-            let stack_start = VirtAddr::from_ptr(&raw const STACK);
+            let stack_start = VirtAddr::from_ptr(unsafe { &STACK });
             let stack_end = stack_start + STACK_SIZE;
             stack_end
         };
@@ -41,7 +41,7 @@ struct Selectors {
 }
 
 pub fn init() {
-    use x86_64::instructions::segmentation::{CS, Segment};
+    use x86_64::instructions::segmentation::{Segment, CS};
     use x86_64::instructions::tables::load_tss;
 
     GDT.0.load();

src/interrupts.rs

@@ -80,31 +80,11 @@ extern "x86-interrupt" fn timer_interrupt_handler(_stack_frame: InterruptStackFr
 }
 
 extern "x86-interrupt" fn keyboard_interrupt_handler(_stack_frame: InterruptStackFrame) {
-    use pc_keyboard::{DecodedKey, HandleControl, Keyboard, ScancodeSet1, layouts};
-    use spin::Mutex;
     use x86_64::instructions::port::Port;
 
-    lazy_static! {
-        static ref KEYBOARD: Mutex<Keyboard<layouts::Us104Key, ScancodeSet1>> =
-            Mutex::new(Keyboard::new(
-                ScancodeSet1::new(),
-                layouts::Us104Key,
-                HandleControl::Ignore
-            ));
-    }
-
-    let mut keyboard = KEYBOARD.lock();
     let mut port = Port::new(0x60);
-
     let scancode: u8 = unsafe { port.read() };
-    if let Ok(Some(key_event)) = keyboard.add_byte(scancode) {
+    crate::task::keyboard::add_scancode(scancode);
-        if let Some(key) = keyboard.process_keyevent(key_event) {
-            match key {
-                DecodedKey::Unicode(character) => print!("{}", character),
-                DecodedKey::RawKey(key) => print!("{:?}", key),
-            }
-        }
-    }
 
     unsafe {
         PICS.lock()

src/lib.rs

@@ -2,6 +2,7 @@
 #![cfg_attr(test, no_main)]
 #![feature(custom_test_frameworks)]
 #![feature(abi_x86_interrupt)]
+#![feature(const_mut_refs)]
 #![test_runner(crate::test_runner)]
 #![reexport_test_harness_main = "test_main"]
 
@@ -13,6 +14,7 @@ pub mod gdt;
 pub mod interrupts;
 pub mod memory;
 pub mod serial;
+pub mod task;
 pub mod vga_buffer;
 
 pub fn init() {
@@ -74,7 +76,7 @@ pub fn hlt_loop() -> ! {
 }
 
 #[cfg(test)]
-use bootloader::{BootInfo, entry_point};
+use bootloader::{entry_point, BootInfo};
 
 #[cfg(test)]
 entry_point!(test_kernel_main);

src/main.rs

@@ -6,9 +6,9 @@
 
 extern crate alloc;
 
-use alloc::{boxed::Box, rc::Rc, vec, vec::Vec};
 use blog_os::println;
-use bootloader::{BootInfo, entry_point};
+use blog_os::task::{executor::Executor, keyboard, Task};
+use bootloader::{entry_point, BootInfo};
 use core::panic::PanicInfo;
 
 entry_point!(kernel_main);
@@ -27,35 +27,13 @@ fn kernel_main(boot_info: &'static BootInfo) -> ! {
 
     allocator::init_heap(&mut mapper, &mut frame_allocator).expect("heap initialization failed");
 
-    // 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());
-
-    // 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();
 
-    println!("It did not crash!");
+    let mut executor = Executor::new();
-    blog_os::hlt_loop();
+    executor.spawn(Task::new(example_task()));
+    executor.spawn(Task::new(keyboard::print_keypresses()));
+    executor.run();
 }
 
 /// This function is called on panic.
@@ -72,6 +50,15 @@ fn panic(info: &PanicInfo) -> ! {
     blog_os::test_panic_handler(info)
 }
 
+async fn async_number() -> u32 {
+    42
+}
+
+async fn example_task() {
+    let number = async_number().await;
+    println!("async number: {}", number);
+}
+
 #[test_case]
 fn trivial_assertion() {
     assert_eq!(1, 1);

src/memory.rs

@@ -1,7 +1,7 @@
 use bootloader::bootinfo::{MemoryMap, MemoryRegionType};
 use x86_64::{
-    PhysAddr, VirtAddr,
     structures::paging::{FrameAllocator, OffsetPageTable, PageTable, PhysFrame, Size4KiB},
+    PhysAddr, VirtAddr,
 };
 
 /// Initialize a new OffsetPageTable.
@@ -11,10 +11,8 @@ use x86_64::{
 /// `physical_memory_offset`. Also, this function must be only called once
 /// to avoid aliasing `&mut` references (which is undefined behavior).
 pub unsafe fn init(physical_memory_offset: VirtAddr) -> OffsetPageTable<'static> {
-    unsafe {
+    let level_4_table = active_level_4_table(physical_memory_offset);
-        let level_4_table = active_level_4_table(physical_memory_offset);
+    OffsetPageTable::new(level_4_table, physical_memory_offset)
-        OffsetPageTable::new(level_4_table, physical_memory_offset)
-    }
 }
 
 /// Returns a mutable reference to the active level 4 table.
@@ -32,7 +30,7 @@ unsafe fn active_level_4_table(physical_memory_offset: VirtAddr) -> &'static mut
     let virt = physical_memory_offset + phys.as_u64();
     let page_table_ptr: *mut PageTable = virt.as_mut_ptr();
 
-    unsafe { &mut *page_table_ptr }
+    &mut *page_table_ptr // unsafe
 }
 
 /// A FrameAllocator that always returns `None`.

src/task/executor.rs

@@ -0,0 +1,102 @@
+use super::{Task, TaskId};
+use alloc::{collections::BTreeMap, sync::Arc, task::Wake};
+use core::task::{Context, Poll, Waker};
+use crossbeam_queue::ArrayQueue;
+
+pub struct Executor {
+    tasks: BTreeMap<TaskId, Task>,
+    task_queue: Arc<ArrayQueue<TaskId>>,
+    waker_cache: BTreeMap<TaskId, Waker>,
+}
+
+impl Executor {
+    pub fn new() -> Self {
+        Executor {
+            tasks: BTreeMap::new(),
+            task_queue: Arc::new(ArrayQueue::new(100)),
+            waker_cache: BTreeMap::new(),
+        }
+    }
+
+    pub fn spawn(&mut self, task: Task) {
+        let task_id = task.id;
+        if self.tasks.insert(task.id, task).is_some() {
+            panic!("task with same ID already in tasks");
+        }
+        self.task_queue.push(task_id).expect("queue full");
+    }
+
+    pub fn run(&mut self) -> ! {
+        loop {
+            self.run_ready_tasks();
+            self.sleep_if_idle();
+        }
+    }
+
+    fn run_ready_tasks(&mut self) {
+        // destructure `self` to avoid borrow checker errors
+        let Self {
+            tasks,
+            task_queue,
+            waker_cache,
+        } = self;
+
+        while let Ok(task_id) = task_queue.pop() {
+            let task = match tasks.get_mut(&task_id) {
+                Some(task) => task,
+                None => continue, // task no longer exists
+            };
+            let waker = waker_cache
+                .entry(task_id)
+                .or_insert_with(|| TaskWaker::new(task_id, task_queue.clone()));
+            let mut context = Context::from_waker(waker);
+            match task.poll(&mut context) {
+                Poll::Ready(()) => {
+                    // task done -> remove it and its cached waker
+                    tasks.remove(&task_id);
+                    waker_cache.remove(&task_id);
+                }
+                Poll::Pending => {}
+            }
+        }
+    }
+
+    fn sleep_if_idle(&self) {
+        use x86_64::instructions::interrupts::{self, enable_and_hlt};
+
+        interrupts::disable();
+        if self.task_queue.is_empty() {
+            enable_and_hlt();
+        } else {
+            interrupts::enable();
+        }
+    }
+}
+
+struct TaskWaker {
+    task_id: TaskId,
+    task_queue: Arc<ArrayQueue<TaskId>>,
+}
+
+impl TaskWaker {
+    fn new(task_id: TaskId, task_queue: Arc<ArrayQueue<TaskId>>) -> Waker {
+        Waker::from(Arc::new(TaskWaker {
+            task_id,
+            task_queue,
+        }))
+    }
+
+    fn wake_task(&self) {
+        self.task_queue.push(self.task_id).expect("task_queue full");
+    }
+}
+
+impl Wake for TaskWaker {
+    fn wake(self: Arc<Self>) {
+        self.wake_task();
+    }
+
+    fn wake_by_ref(self: &Arc<Self>) {
+        self.wake_task();
+    }
+}

src/task/keyboard.rs

@@ -0,0 +1,83 @@
+use crate::{print, println};
+use conquer_once::spin::OnceCell;
+use core::{
+    pin::Pin,
+    task::{Context, Poll},
+};
+use crossbeam_queue::ArrayQueue;
+use futures_util::{
+    stream::{Stream, StreamExt},
+    task::AtomicWaker,
+};
+use pc_keyboard::{layouts, DecodedKey, HandleControl, Keyboard, ScancodeSet1};
+
+static SCANCODE_QUEUE: OnceCell<ArrayQueue<u8>> = OnceCell::uninit();
+static WAKER: AtomicWaker = AtomicWaker::new();
+
+/// Called by the keyboard interrupt handler
+///
+/// Must not block or allocate.
+pub(crate) fn add_scancode(scancode: u8) {
+    if let Ok(queue) = SCANCODE_QUEUE.try_get() {
+        if let Err(_) = queue.push(scancode) {
+            println!("WARNING: scancode queue full; dropping keyboard input");
+        } else {
+            WAKER.wake();
+        }
+    } else {
+        println!("WARNING: scancode queue uninitialized");
+    }
+}
+
+pub struct ScancodeStream {
+    _private: (),
+}
+
+impl ScancodeStream {
+    pub fn new() -> Self {
+        SCANCODE_QUEUE
+            .try_init_once(|| ArrayQueue::new(100))
+            .expect("ScancodeStream::new should only be called once");
+        ScancodeStream { _private: () }
+    }
+}
+
+impl Stream for ScancodeStream {
+    type Item = u8;
+
+    fn poll_next(self: Pin<&mut Self>, cx: &mut Context) -> Poll<Option<u8>> {
+        let queue = SCANCODE_QUEUE
+            .try_get()
+            .expect("scancode queue not initialized");
+
+        // fast path
+        if let Ok(scancode) = queue.pop() {
+            return Poll::Ready(Some(scancode));
+        }
+
+        WAKER.register(&cx.waker());
+        match queue.pop() {
+            Ok(scancode) => {
+                WAKER.take();
+                Poll::Ready(Some(scancode))
+            }
+            Err(crossbeam_queue::PopError) => Poll::Pending,
+        }
+    }
+}
+
+pub async fn print_keypresses() {
+    let mut scancodes = ScancodeStream::new();
+    let mut keyboard = Keyboard::new(layouts::Us104Key, ScancodeSet1, HandleControl::Ignore);
+
+    while let Some(scancode) = scancodes.next().await {
+        if let Ok(Some(key_event)) = keyboard.add_byte(scancode) {
+            if let Some(key) = keyboard.process_keyevent(key_event) {
+                match key {
+                    DecodedKey::Unicode(character) => print!("{}", character),
+                    DecodedKey::RawKey(key) => print!("{:?}", key),
+                }
+            }
+        }
+    }
+}

src/task/mod.rs

@@ -0,0 +1,39 @@
+use alloc::boxed::Box;
+use core::{
+    future::Future,
+    pin::Pin,
+    sync::atomic::{AtomicU64, Ordering},
+    task::{Context, Poll},
+};
+
+pub mod executor;
+pub mod keyboard;
+pub mod simple_executor;
+
+pub struct Task {
+    id: TaskId,
+    future: Pin<Box<dyn Future<Output = ()>>>,
+}
+
+impl Task {
+    pub fn new(future: impl Future<Output = ()> + 'static) -> Task {
+        Task {
+            id: TaskId::new(),
+            future: Box::pin(future),
+        }
+    }
+
+    fn poll(&mut self, context: &mut Context) -> Poll<()> {
+        self.future.as_mut().poll(context)
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
+struct TaskId(u64);
+
+impl TaskId {
+    fn new() -> Self {
+        static NEXT_ID: AtomicU64 = AtomicU64::new(0);
+        TaskId(NEXT_ID.fetch_add(1, Ordering::Relaxed))
+    }
+}

src/task/simple_executor.rs

@@ -0,0 +1,44 @@
+use super::Task;
+use alloc::collections::VecDeque;
+use core::task::{Context, Poll, RawWaker, RawWakerVTable, Waker};
+
+pub struct SimpleExecutor {
+    task_queue: VecDeque<Task>,
+}
+
+impl SimpleExecutor {
+    pub fn new() -> SimpleExecutor {
+        SimpleExecutor {
+            task_queue: VecDeque::new(),
+        }
+    }
+
+    pub fn spawn(&mut self, task: Task) {
+        self.task_queue.push_back(task)
+    }
+
+    pub fn run(&mut self) {
+        while let Some(mut task) = self.task_queue.pop_front() {
+            let waker = dummy_waker();
+            let mut context = Context::from_waker(&waker);
+            match task.poll(&mut context) {
+                Poll::Ready(()) => {} // task done
+                Poll::Pending => self.task_queue.push_back(task),
+            }
+        }
+    }
+}
+
+fn dummy_raw_waker() -> RawWaker {
+    fn no_op(_: *const ()) {}
+    fn clone(_: *const ()) -> RawWaker {
+        dummy_raw_waker()
+    }
+
+    let vtable = &RawWakerVTable::new(clone, no_op, no_op, no_op);
+    RawWaker::new(0 as *const (), vtable)
+}
+
+fn dummy_waker() -> Waker {
+    unsafe { Waker::from_raw(dummy_raw_waker()) }
+}

tests/basic_boot.rs

@@ -7,7 +7,7 @@
 use blog_os::println;
 use core::panic::PanicInfo;
 
-#[unsafe(no_mangle)] // don't mangle the name of this function
+#[no_mangle] // don't mangle the name of this function
 pub extern "C" fn _start() -> ! {
     test_main();
 

tests/heap_allocation.rs

@@ -8,7 +8,7 @@ extern crate alloc;
 
 use alloc::{boxed::Box, vec::Vec};
 use blog_os::allocator::HEAP_SIZE;
-use bootloader::{BootInfo, entry_point};
+use bootloader::{entry_point, BootInfo};
 use core::panic::PanicInfo;
 
 entry_point!(main);

tests/should_panic.rs

@@ -1,10 +1,10 @@
 #![no_std]
 #![no_main]
 
-use blog_os::{QemuExitCode, exit_qemu, serial_print, serial_println};
+use blog_os::{exit_qemu, serial_print, serial_println, QemuExitCode};
 use core::panic::PanicInfo;
 
-#[unsafe(no_mangle)]
+#[no_mangle]
 pub extern "C" fn _start() -> ! {
     should_fail();
     serial_println!("[test did not panic]");

tests/stack_overflow.rs

@@ -2,12 +2,12 @@
 #![no_main]
 #![feature(abi_x86_interrupt)]
 
-use blog_os::{QemuExitCode, exit_qemu, serial_print, serial_println};
+use blog_os::{exit_qemu, serial_print, serial_println, QemuExitCode};
 use core::panic::PanicInfo;
 use lazy_static::lazy_static;
 use x86_64::structures::idt::{InterruptDescriptorTable, InterruptStackFrame};
 
-#[unsafe(no_mangle)]
+#[no_mangle]
 pub extern "C" fn _start() -> ! {
     serial_print!("stack_overflow::stack_overflow...\t");
 

x86_64-blog_os.json

@@ -1,16 +1,15 @@
 {
     "llvm-target": "x86_64-unknown-none",
-    "data-layout": "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128",
+    "data-layout": "e-m:e-i64:64-f80:128-n8:16:32:64-S128",
     "arch": "x86_64",
     "target-endian": "little",
-    "target-pointer-width": 64,
+    "target-pointer-width": "64",
-    "target-c-int-width": 32,
+    "target-c-int-width": "32",
     "os": "none",
     "executables": true,
     "linker-flavor": "ld.lld",
     "linker": "rust-lld",
     "panic-strategy": "abort",
     "disable-redzone": true,
-    "features": "-mmx,-sse,+soft-float",
+    "features": "-mmx,-sse,+soft-float"
-    "rustc-abi": "x86-softfloat"
   }