From 211ec3898bb84e39a2a40e4b88ee68a178a2f1c8 Mon Sep 17 00:00:00 2001
From: Philipp Oppermann <dev@phil-opp.com>
Date: Wed, 11 Sep 2019 13:40:26 +0200
Subject: [PATCH 1/3] Use OffsetPageTable instead of MappedPageTable

---
 src/main.rs   |  3 ++-
 src/memory.rs | 18 ++++++------------
 2 files changed, 8 insertions(+), 13 deletions(-)

diff --git a/src/main.rs b/src/main.rs
index 10b38955..af63c56f 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -17,7 +17,8 @@ fn kernel_main(boot_info: &'static BootInfo) -> ! {
     println!("Hello World{}", "!");
     blog_os::init();
 
-    let mut mapper = unsafe { memory::init(boot_info.physical_memory_offset) };
+    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 a previously unmapped page
diff --git a/src/memory.rs b/src/memory.rs
index 626f4fdb..b54225c2 100644
--- a/src/memory.rs
+++ b/src/memory.rs
@@ -1,26 +1,20 @@
 use bootloader::bootinfo::{MemoryMap, MemoryRegionType};
 use x86_64::{
     structures::paging::{
-        FrameAllocator, MappedPageTable, Mapper, MapperAllSizes, Page, PageTable, PhysFrame,
-        Size4KiB,
+        FrameAllocator, Mapper, OffsetPageTable, Page, PageTable, PhysFrame, Size4KiB,
     },
     PhysAddr, VirtAddr,
 };
 
-/// Initialize a new MappedPageTable.
+/// Initialize a new OffsetPageTable.
 ///
 /// This function is unsafe because the caller must guarantee that the
 /// complete physical memory is mapped to virtual memory at the passed
 /// `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: u64) -> impl MapperAllSizes {
+pub unsafe fn init(physical_memory_offset: VirtAddr) -> OffsetPageTable<'static> {
     let level_4_table = active_level_4_table(physical_memory_offset);
-    let phys_to_virt = move |frame: PhysFrame| -> *mut PageTable {
-        let phys = frame.start_address().as_u64();
-        let virt = VirtAddr::new(phys + physical_memory_offset);
-        virt.as_mut_ptr()
-    };
-    MappedPageTable::new(level_4_table, phys_to_virt)
+    OffsetPageTable::new(level_4_table, physical_memory_offset)
 }
 
 /// Returns a mutable reference to the active level 4 table.
@@ -29,13 +23,13 @@ pub unsafe fn init(physical_memory_offset: u64) -> impl MapperAllSizes {
 /// complete physical memory is mapped to virtual memory at the passed
 /// `physical_memory_offset`. Also, this function must be only called once
 /// to avoid aliasing `&mut` references (which is undefined behavior).
-unsafe fn active_level_4_table(physical_memory_offset: u64) -> &'static mut PageTable {
+unsafe fn active_level_4_table(physical_memory_offset: VirtAddr) -> &'static mut PageTable {
     use x86_64::registers::control::Cr3;
 
     let (level_4_table_frame, _) = Cr3::read();
 
     let phys = level_4_table_frame.start_address();
-    let virt = VirtAddr::new(phys.as_u64() + physical_memory_offset);
+    let virt = physical_memory_offset + phys.as_u64();
     let page_table_ptr: *mut PageTable = virt.as_mut_ptr();
 
     &mut *page_table_ptr // unsafe

From 7ec727f69f9113d4fb23d9edc39bb3c6436acd23 Mon Sep 17 00:00:00 2001
From: Philipp Oppermann <dev@phil-opp.com>
Date: Sat, 14 Sep 2019 18:33:16 +0200
Subject: [PATCH 2/3] Update comment

---
 src/main.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/main.rs b/src/main.rs
index af63c56f..2974192a 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -21,7 +21,7 @@ fn kernel_main(boot_info: &'static BootInfo) -> ! {
     let mut mapper = unsafe { memory::init(phys_mem_offset) };
     let mut frame_allocator = unsafe { BootInfoFrameAllocator::init(&boot_info.memory_map) };
 
-    // map a previously unmapped page
+    // map an unused page
     let page = Page::containing_address(VirtAddr::new(0xdeadbeaf000));
     memory::create_example_mapping(page, &mut mapper, &mut frame_allocator);
 

From 5cced71fb0cc00aea3b9e361bd3e39f55aaa7bb9 Mon Sep 17 00:00:00 2001
From: Philipp Oppermann <dev@phil-opp.com>
Date: Sat, 14 Sep 2019 18:33:37 +0200
Subject: [PATCH 3/3] Directly use OffsetPageTable for create_example_mapping
 instead of impl trait

---
 src/memory.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/memory.rs b/src/memory.rs
index b54225c2..11c50445 100644
--- a/src/memory.rs
+++ b/src/memory.rs
@@ -38,7 +38,7 @@ unsafe fn active_level_4_table(physical_memory_offset: VirtAddr) -> &'static mut
 /// Creates an example mapping for the given page to frame `0xb8000`.
 pub fn create_example_mapping(
     page: Page,
-    mapper: &mut impl Mapper<Size4KiB>,
+    mapper: &mut OffsetPageTable,
     frame_allocator: &mut impl FrameAllocator<Size4KiB>,
 ) {
     use x86_64::structures::paging::PageTableFlags as Flags;