From e029eabe180e6ee070ded981e56849a96664e30a Mon Sep 17 00:00:00 2001
From: Philipp Oppermann <dev@phil-opp.com>
Date: Tue, 18 Apr 2017 12:11:40 +0200
Subject: [PATCH] Add a remap_the_kernel function

---
 src/memory/mod.rs        | 26 +++++++++++++++++++++++++
 src/memory/paging/mod.rs | 41 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 67 insertions(+)

diff --git a/src/memory/mod.rs b/src/memory/mod.rs
index daa3478..f8094bd 100644
--- a/src/memory/mod.rs
+++ b/src/memory/mod.rs
@@ -23,8 +23,34 @@ impl Frame {
     fn clone(&self) -> Frame {
         Frame { number: self.number }
     }
+
+    fn range_inclusive(start: Frame, end: Frame) -> FrameIter {
+        FrameIter {
+            start: start,
+            end: end,
+        }
+    }
+}
+
+struct FrameIter {
+    start: Frame,
+    end: Frame,
 }
 
+impl Iterator for FrameIter {
+    type Item = Frame;
+
+    fn next(&mut self) -> Option<Frame> {
+        if self.start <= self.end {
+            let frame = self.start.clone();
+            self.start.number += 1;
+            Some(frame)
+        } else {
+            None
+        }
+    }
+ }
+
 pub trait FrameAllocator {
     fn allocate_frame(&mut self) -> Option<Frame>;
     fn deallocate_frame(&mut self, frame: Frame);
diff --git a/src/memory/paging/mod.rs b/src/memory/paging/mod.rs
index 257a58a..e734949 100644
--- a/src/memory/paging/mod.rs
+++ b/src/memory/paging/mod.rs
@@ -3,6 +3,7 @@ pub use self::mapper::Mapper;
 use core::ops::{Deref, DerefMut};
 use core::ptr::Unique;
 use memory::{PAGE_SIZE, Frame, FrameAllocator};
+use multiboot2::BootInformation;
 use self::table::{Table, Level4};
 use self::temporary_page::TemporaryPage;
 
@@ -127,3 +128,43 @@ impl InactivePageTable {
         InactivePageTable { p4_frame: frame }
     }
 }
+
+pub fn remap_the_kernel<A>(allocator: &mut A, boot_info: &BootInformation)
+    where A: FrameAllocator
+{
+    let mut temporary_page = TemporaryPage::new(Page { number: 0xcafebabe },
+        allocator);
+
+    let mut active_table = unsafe { ActivePageTable::new() };
+    let mut new_table = {
+        let frame = allocator.allocate_frame().expect("no more frames");
+        InactivePageTable::new(frame, &mut active_table, &mut temporary_page)
+    };
+
+    active_table.with(&mut new_table, &mut temporary_page, |mapper| {
+        let elf_sections_tag = boot_info.elf_sections_tag()
+            .expect("Memory map tag required");
+
+        for section in elf_sections_tag.sections() {
+            use self::entry::WRITABLE;
+
+            if !section.is_allocated() {
+                // section is not loaded to memory
+                continue;
+            }
+            assert!(section.start_address() % PAGE_SIZE == 0,
+                    "sections need to be page aligned");
+
+            println!("mapping section at addr: {:#x}, size: {:#x}",
+                section.addr, section.size);
+
+            let flags = WRITABLE; // TODO use real section flags
+
+            let start_frame = Frame::containing_address(section.start_address());
+            let end_frame = Frame::containing_address(section.end_address() - 1);
+            for frame in Frame::range_inclusive(start_frame, end_frame) {
+                mapper.identity_map(frame, flags, allocator);
+            }
+        }
+    });
+}