From 48e2175bac11299d6f7dd134567d38e518bac17c Mon Sep 17 00:00:00 2001
From: Philipp Oppermann <dev@phil-opp.com>
Date: Mon, 17 Jun 2019 16:55:10 +0200
Subject: [PATCH 01/12] Add a dependency on the alloc crate

---
 src/lib.rs | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/lib.rs b/src/lib.rs
index 45cae2de..d27b7b49 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -5,6 +5,8 @@
 #![test_runner(crate::test_runner)]
 #![reexport_test_harness_main = "test_main"]
 
+extern crate alloc;
+
 use core::panic::PanicInfo;
 
 pub mod gdt;

From c0367074ac143c8952c7fdd7150b470ec9ad5739 Mon Sep 17 00:00:00 2001
From: Philipp Oppermann <dev@phil-opp.com>
Date: Mon, 17 Jun 2019 17:49:06 +0200
Subject: [PATCH 02/12] Create an allocator module with a dummy allocator

---
 src/allocator.rs | 14 ++++++++++++++
 src/lib.rs       |  1 +
 2 files changed, 15 insertions(+)
 create mode 100644 src/allocator.rs

diff --git a/src/allocator.rs b/src/allocator.rs
new file mode 100644
index 00000000..ac452c10
--- /dev/null
+++ b/src/allocator.rs
@@ -0,0 +1,14 @@
+use alloc::alloc::{GlobalAlloc, Layout};
+use core::ptr::null_mut;
+
+pub struct Dummy;
+
+unsafe impl GlobalAlloc for Dummy {
+    unsafe fn alloc(&self, _layout: Layout) -> *mut u8 {
+        null_mut()
+    }
+
+    unsafe fn dealloc(&self, _ptr: *mut u8, _layout: Layout) {
+        panic!("dealloc should be never called")
+    }
+}
\ No newline at end of file
diff --git a/src/lib.rs b/src/lib.rs
index d27b7b49..320a3ca4 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -9,6 +9,7 @@ extern crate alloc;
 
 use core::panic::PanicInfo;
 
+pub mod allocator;
 pub mod gdt;
 pub mod interrupts;
 pub mod memory;

From ebbc6d55d26b90a9ac0eceb8db6ba682b352553c Mon Sep 17 00:00:00 2001
From: Philipp Oppermann <dev@phil-opp.com>
Date: Mon, 17 Jun 2019 17:49:21 +0200
Subject: [PATCH 03/12] Use dummy allocator as global allocator

---
 src/lib.rs | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/lib.rs b/src/lib.rs
index 320a3ca4..94ee9290 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -16,6 +16,9 @@ pub mod memory;
 pub mod serial;
 pub mod vga_buffer;
 
+#[global_allocator]
+static ALLOCATOR: allocator::Dummy = allocator::Dummy;
+
 pub fn init() {
     gdt::init();
     interrupts::init_idt();

From 417c44159ea5de7d54335535c63288742f5912aa Mon Sep 17 00:00:00 2001
From: Philipp Oppermann <dev@phil-opp.com>
Date: Mon, 17 Jun 2019 17:50:35 +0200
Subject: [PATCH 04/12] Add a alloc_error_handler function

---
 src/lib.rs | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/lib.rs b/src/lib.rs
index 94ee9290..3e7673a5 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -2,6 +2,7 @@
 #![cfg_attr(test, no_main)]
 #![feature(custom_test_frameworks)]
 #![feature(abi_x86_interrupt)]
+#![feature(alloc_error_handler)]
 #![test_runner(crate::test_runner)]
 #![reexport_test_harness_main = "test_main"]
 
@@ -82,3 +83,8 @@ fn test_kernel_main(_boot_info: &'static BootInfo) -> ! {
 fn panic(info: &PanicInfo) -> ! {
     test_panic_handler(info)
 }
+
+#[alloc_error_handler]
+fn alloc_error_handler(layout: alloc::alloc::Layout) -> ! {
+    panic!("allocation error: {:?}", layout)
+}

From d4623419b0be4d2dddad39b9d993a482e890c967 Mon Sep 17 00:00:00 2001
From: Philipp Oppermann <dev@phil-opp.com>
Date: Mon, 17 Jun 2019 17:51:12 +0200
Subject: [PATCH 05/12] Try to use Box type in main.rs

This causes an allocation error because the Dummy::alloc function always returns a null pointer.
---
 src/main.rs | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/src/main.rs b/src/main.rs
index 10b38955..0d3e0df6 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -4,9 +4,12 @@
 #![test_runner(blog_os::test_runner)]
 #![reexport_test_harness_main = "test_main"]
 
+extern crate alloc;
+
 use blog_os::println;
 use bootloader::{entry_point, BootInfo};
 use core::panic::PanicInfo;
+use alloc::boxed::Box;
 
 entry_point!(kernel_main);
 
@@ -20,13 +23,7 @@ fn kernel_main(boot_info: &'static BootInfo) -> ! {
     let mut mapper = unsafe { memory::init(boot_info.physical_memory_offset) };
     let mut frame_allocator = unsafe { BootInfoFrameAllocator::init(&boot_info.memory_map) };
 
-    // map a previously unmapped page
-    let page = Page::containing_address(VirtAddr::new(0xdeadbeaf000));
-    memory::create_example_mapping(page, &mut mapper, &mut frame_allocator);
-
-    // 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) };
+    let x = Box::new(41);
 
     #[cfg(test)]
     test_main();

From 06fc63028ab3b4e111303b957356e937f625d437 Mon Sep 17 00:00:00 2001
From: Philipp Oppermann <dev@phil-opp.com>
Date: Wed, 26 Jun 2019 13:14:56 +0200
Subject: [PATCH 06/12] Create a heap memory area

---
 src/allocator.rs | 34 +++++++++++++++++++++++++++++++++-
 src/main.rs      |  5 ++++-
 2 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/src/allocator.rs b/src/allocator.rs
index ac452c10..cf85bd6d 100644
--- a/src/allocator.rs
+++ b/src/allocator.rs
@@ -1,5 +1,37 @@
 use alloc::alloc::{GlobalAlloc, Layout};
 use core::ptr::null_mut;
+use x86_64::{
+    structures::paging::{
+        mapper::MapToError, FrameAllocator, Mapper, Page, PageTableFlags, Size4KiB,
+    },
+    VirtAddr,
+};
+
+pub const HEAP_START: usize = 0x_4444_4444_0000;
+pub const HEAP_SIZE: usize = 100 * 1024; // 100 KiB
+
+pub fn init_heap(
+    mapper: &mut impl Mapper<Size4KiB>,
+    frame_allocator: &mut impl FrameAllocator<Size4KiB>,
+) -> Result<(), MapToError> {
+    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() };
+    }
+
+    Ok(())
+}
 
 pub struct Dummy;
 
@@ -11,4 +43,4 @@ unsafe impl GlobalAlloc for Dummy {
     unsafe fn dealloc(&self, _ptr: *mut u8, _layout: Layout) {
         panic!("dealloc should be never called")
     }
-}
\ No newline at end of file
+}
diff --git a/src/main.rs b/src/main.rs
index 0d3e0df6..69e73633 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -14,8 +14,8 @@ use alloc::boxed::Box;
 entry_point!(kernel_main);
 
 fn kernel_main(boot_info: &'static BootInfo) -> ! {
+    use blog_os::allocator;
     use blog_os::memory::{self, BootInfoFrameAllocator};
-    use x86_64::{structures::paging::Page, VirtAddr};
 
     println!("Hello World{}", "!");
     blog_os::init();
@@ -23,6 +23,9 @@ fn kernel_main(boot_info: &'static BootInfo) -> ! {
     let mut mapper = unsafe { memory::init(boot_info.physical_memory_offset) };
     let mut frame_allocator = unsafe { BootInfoFrameAllocator::init(&boot_info.memory_map) };
 
+    allocator::init_heap(&mut mapper, &mut frame_allocator)
+        .expect("heap initialization failed");
+
     let x = Box::new(41);
 
     #[cfg(test)]

From d7484ab48b740a5a9171b2ef622889aee9630e30 Mon Sep 17 00:00:00 2001
From: Philipp Oppermann <dev@phil-opp.com>
Date: Wed, 26 Jun 2019 15:05:57 +0200
Subject: [PATCH 07/12] Use linked_list_allocator crate instead of dummy
 allocator

---
 Cargo.lock       | 10 ++++++++++
 Cargo.toml       |  1 +
 src/allocator.rs |  4 ++++
 src/lib.rs       |  3 ++-
 4 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/Cargo.lock b/Cargo.lock
index be6694de..c52c589a 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -24,6 +24,7 @@ version = "0.1.0"
 dependencies = [
  "bootloader 0.6.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "lazy_static 1.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "linked_list_allocator 0.6.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "pc-keyboard 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "pic8259_simple 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "spin 0.4.10 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -99,6 +100,14 @@ name = "libc"
 version = "0.2.51"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "linked_list_allocator"
+version = "0.6.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "spin 0.5.0 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "llvm-tools"
 version = "0.1.1"
@@ -349,6 +358,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum getopts 0.2.18 (registry+https://github.com/rust-lang/crates.io-index)" = "0a7292d30132fb5424b354f5dc02512a86e4c516fe544bb7a25e7f266951b797"
 "checksum lazy_static 1.3.0 (registry+https://github.com/rust-lang/crates.io-index)" = "bc5729f27f159ddd61f4df6228e827e86643d4d3e7c32183cb30a1c08f604a14"
 "checksum libc 0.2.51 (registry+https://github.com/rust-lang/crates.io-index)" = "bedcc7a809076656486ffe045abeeac163da1b558e963a31e29fbfbeba916917"
+"checksum linked_list_allocator 0.6.4 (registry+https://github.com/rust-lang/crates.io-index)" = "47314ec1d29aa869ee7cb5a5be57be9b1055c56567d59c3fb6689926743e0bea"
 "checksum llvm-tools 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)" = "955be5d0ca0465caf127165acb47964f911e2bc26073e865deb8be7189302faf"
 "checksum nodrop 0.1.13 (registry+https://github.com/rust-lang/crates.io-index)" = "2f9667ddcc6cc8a43afc9b7917599d7216aa09c463919ea32c59ed6cac8bc945"
 "checksum os_bootinfo 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)" = "66481dbeb5e773e7bd85b63cd6042c30786f834338288c5ec4f3742673db360a"
diff --git a/Cargo.toml b/Cargo.toml
index f7d9d20a..46e66f6f 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -20,6 +20,7 @@ x86_64 = "0.7.0"
 uart_16550 = "0.2.0"
 pic8259_simple = "0.1.1"
 pc-keyboard = "0.3.1"
+linked_list_allocator = "0.6.4"
 
 [dependencies.lazy_static]
 version = "1.0"
diff --git a/src/allocator.rs b/src/allocator.rs
index cf85bd6d..0d1f3b73 100644
--- a/src/allocator.rs
+++ b/src/allocator.rs
@@ -30,6 +30,10 @@ pub fn init_heap(
         unsafe { mapper.map_to(page, frame, flags, frame_allocator)?.flush() };
     }
 
+    unsafe {
+        super::ALLOCATOR.lock().init(HEAP_START, HEAP_SIZE);
+    }
+
     Ok(())
 }
 
diff --git a/src/lib.rs b/src/lib.rs
index 3e7673a5..f416c1e5 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -9,6 +9,7 @@
 extern crate alloc;
 
 use core::panic::PanicInfo;
+use linked_list_allocator::LockedHeap;
 
 pub mod allocator;
 pub mod gdt;
@@ -18,7 +19,7 @@ pub mod serial;
 pub mod vga_buffer;
 
 #[global_allocator]
-static ALLOCATOR: allocator::Dummy = allocator::Dummy;
+static ALLOCATOR: LockedHeap = LockedHeap::empty();
 
 pub fn init() {
     gdt::init();

From f429a8ab032647ed2a285dd7a536ef224a8adcd0 Mon Sep 17 00:00:00 2001
From: Philipp Oppermann <dev@phil-opp.com>
Date: Wed, 26 Jun 2019 15:06:40 +0200
Subject: [PATCH 08/12] Example use of Box, Vec, and Rc in kernel_main

---
 src/main.rs | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/src/main.rs b/src/main.rs
index 69e73633..3ce0b620 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -9,7 +9,7 @@ extern crate alloc;
 use blog_os::println;
 use bootloader::{entry_point, BootInfo};
 use core::panic::PanicInfo;
-use alloc::boxed::Box;
+use alloc::{boxed::Box, vec, vec::Vec, rc::Rc};
 
 entry_point!(kernel_main);
 
@@ -26,7 +26,23 @@ fn kernel_main(boot_info: &'static BootInfo) -> ! {
     allocator::init_heap(&mut mapper, &mut frame_allocator)
         .expect("heap initialization failed");
 
-    let x = Box::new(41);
+    // 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 deallocated 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();

From e5b6ba38ac74cb47ba6c1f639bdddff4b1861cb2 Mon Sep 17 00:00:00 2001
From: Philipp Oppermann <dev@phil-opp.com>
Date: Wed, 26 Jun 2019 16:33:20 +0200
Subject: [PATCH 09/12] Update Readme for new post

---
 README.md | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/README.md b/README.md
index 33e5ea77..5d2fa573 100644
--- a/README.md
+++ b/README.md
@@ -1,10 +1,10 @@
-# Blog OS (Paging Implementation)
+# Blog OS (Heap Allocation)
 
 [![Azure Pipelines CI build](https://img.shields.io/azure-devops/build/phil-opp/blog_os/1/post-08.svg?label=Build&style=flat-square)](https://dev.azure.com/phil-opp/blog_os/_build?definitionId=1)
 
-This repository contains the source code for the [Paging Implementation][post] post of the [Writing an OS in Rust](https://os.phil-opp.com) series.
+This repository contains the source code for the [Heap Allocation][post] post of the [Writing an OS in Rust](https://os.phil-opp.com) series.
 
-[post]: https://os.phil-opp.com/paging-implementation/
+[post]: https://os.phil-opp.com/heap-allocation/
 
 **Check out the [master branch](https://github.com/phil-opp/blog_os) for more information.**
 

From 5cf388439607c641a92611b98858a89b14fc87ef Mon Sep 17 00:00:00 2001
From: Philipp Oppermann <dev@phil-opp.com>
Date: Wed, 26 Jun 2019 16:59:38 +0200
Subject: [PATCH 10/12] Run cargo fmt

---
 src/main.rs | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/src/main.rs b/src/main.rs
index 3ce0b620..5f2d1856 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -6,10 +6,10 @@
 
 extern crate alloc;
 
+use alloc::{boxed::Box, rc::Rc, vec, vec::Vec};
 use blog_os::println;
 use bootloader::{entry_point, BootInfo};
 use core::panic::PanicInfo;
-use alloc::{boxed::Box, vec, vec::Vec, rc::Rc};
 
 entry_point!(kernel_main);
 
@@ -23,8 +23,7 @@ fn kernel_main(boot_info: &'static BootInfo) -> ! {
     let mut mapper = unsafe { memory::init(boot_info.physical_memory_offset) };
     let mut frame_allocator = unsafe { BootInfoFrameAllocator::init(&boot_info.memory_map) };
 
-    allocator::init_heap(&mut mapper, &mut frame_allocator)
-        .expect("heap initialization failed");
+    allocator::init_heap(&mut mapper, &mut frame_allocator).expect("heap initialization failed");
 
     // allocate a number on the heap
     let heap_value = Box::new(41);
@@ -40,9 +39,15 @@ fn kernel_main(boot_info: &'static BootInfo) -> ! {
     // create a reference counted vector -> will be deallocated 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));
+    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));
+    println!(
+        "reference count is {} now",
+        Rc::strong_count(&cloned_reference)
+    );
 
     #[cfg(test)]
     test_main();

From df75f7f4e83d666ac5fa1b84066959635844922f Mon Sep 17 00:00:00 2001
From: Philipp Oppermann <dev@phil-opp.com>
Date: Wed, 26 Jun 2019 16:59:56 +0200
Subject: [PATCH 11/12] Add an integration test for heap allocation

---
 tests/heap_allocation.rs | 63 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 63 insertions(+)
 create mode 100644 tests/heap_allocation.rs

diff --git a/tests/heap_allocation.rs b/tests/heap_allocation.rs
new file mode 100644
index 00000000..a4548d9e
--- /dev/null
+++ b/tests/heap_allocation.rs
@@ -0,0 +1,63 @@
+#![no_std]
+#![no_main]
+#![feature(custom_test_frameworks)]
+#![test_runner(blog_os::test_runner)]
+#![reexport_test_harness_main = "test_main"]
+
+extern crate alloc;
+
+use alloc::{boxed::Box, vec::Vec};
+use blog_os::{serial_print, serial_println};
+use bootloader::{entry_point, BootInfo};
+use core::panic::PanicInfo;
+
+entry_point!(main);
+
+fn main(boot_info: &'static BootInfo) -> ! {
+    use blog_os::allocator;
+    use blog_os::memory::{self, BootInfoFrameAllocator};
+
+    blog_os::init();
+    let mut mapper = unsafe { memory::init(boot_info.physical_memory_offset) };
+    let mut frame_allocator = unsafe { BootInfoFrameAllocator::init(&boot_info.memory_map) };
+
+    allocator::init_heap(&mut mapper, &mut frame_allocator).expect("heap initialization failed");
+
+    test_main();
+    loop {}
+}
+
+#[test_case]
+fn simple_allocation() {
+    serial_print!("simple_allocation... ");
+    let heap_value = Box::new(41);
+    assert_eq!(*heap_value, 41);
+    serial_println!("[ok]");
+}
+
+#[test_case]
+fn large_vec() {
+    serial_print!("large_vec... ");
+    let n = 1000;
+    let mut vec = Vec::new();
+    for i in 0..n {
+        vec.push(i);
+    }
+    assert_eq!(vec.iter().sum::<u64>(), (n - 1) * n / 2);
+    serial_println!("[ok]");
+}
+
+#[test_case]
+fn many_boxes() {
+    serial_print!("many_boxes... ");
+    for i in 0..10_000 {
+        let x = Box::new(i);
+        assert_eq!(*x, i);
+    }
+    serial_println!("[ok]");
+}
+
+#[panic_handler]
+fn panic(info: &PanicInfo) -> ! {
+    blog_os::test_panic_handler(info)
+}

From 4792ec41b13cb4e8df433a8adef3a12162ef5370 Mon Sep 17 00:00:00 2001
From: Philipp Oppermann <dev@phil-opp.com>
Date: Wed, 26 Jun 2019 21:08:08 +0200
Subject: [PATCH 12/12] Adjust comments to be equal with post

---
 src/main.rs              | 2 +-
 tests/heap_allocation.rs | 1 -
 2 files changed, 1 insertion(+), 2 deletions(-)

diff --git a/src/main.rs b/src/main.rs
index 5f2d1856..de7cc0f0 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -36,7 +36,7 @@ fn kernel_main(boot_info: &'static BootInfo) -> ! {
     }
     println!("vec at {:p}", vec.as_slice());
 
-    // create a reference counted vector -> will be deallocated when count reaches 0
+    // 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!(
diff --git a/tests/heap_allocation.rs b/tests/heap_allocation.rs
index a4548d9e..c803ba77 100644
--- a/tests/heap_allocation.rs
+++ b/tests/heap_allocation.rs
@@ -20,7 +20,6 @@ fn main(boot_info: &'static BootInfo) -> ! {
     blog_os::init();
     let mut mapper = unsafe { memory::init(boot_info.physical_memory_offset) };
     let mut frame_allocator = unsafe { BootInfoFrameAllocator::init(&boot_info.memory_map) };
-
     allocator::init_heap(&mut mapper, &mut frame_allocator).expect("heap initialization failed");
 
     test_main();