From f3f7aad23c5bb1f48b10a716c10b1be8acf15e39 Mon Sep 17 00:00:00 2001
From: guillaume didier <guillaume.didier@inria.fr>
Date: Thu, 20 Feb 2020 09:19:40 +0100
Subject: [PATCH] Memory map dump

---
 src/main.rs   | 2 ++
 src/memory.rs | 6 ++++--
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/main.rs b/src/main.rs
index 9667a70..a276038 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -64,6 +64,8 @@ fn kernel_main(boot_info: &'static BootInfo) -> ! {
     use x86_64::structures::paging::MapperAllSizes;
     use x86_64::VirtAddr;
 
+    serial_println!("Memory map: {:#?}", boot_info.memory_map);
+
     let phys_mem_offset = VirtAddr::new(boot_info.physical_memory_offset);
     // new: initialize a mapper
     let mut frame_allocator =
diff --git a/src/memory.rs b/src/memory.rs
index ce98eb5..93bfcaa 100644
--- a/src/memory.rs
+++ b/src/memory.rs
@@ -79,12 +79,14 @@ impl BootInfoFrameAllocator {
         // map each region to its address range
         let addr_ranges = usable_regions.map(|r| r.range.start_addr()..r.range.end_addr());
         // transform to an iterator of frame start addresses
-        let frame_addresses = addr_ranges.flat_map(|r| r.step_by(4096));
-        // create `PhysFrame` types from the start addresses
+        let frame_addresses = addr_ranges.flat_map(|r| r.step_by(4096)); // TODO Magic number, this is where 4k pages are enforced
+                                                                         // create `PhysFrame` types from the start addresses
         let frames = frame_addresses.map(|addr| PhysFrame::containing_address(PhysAddr::new(addr)));
         frames
     }
 }
+
+// We only allocate 4k pages
 unsafe impl FrameAllocator<Size4KiB> for BootInfoFrameAllocator {
     fn allocate_frame(&mut self) -> Option<UnusedPhysFrame> {
         let frame = self.usable_frames().nth(self.next);