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] 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)]