From c83ab3c3a292f9bcbc09b069a308f20fb49df8c1 Mon Sep 17 00:00:00 2001
From: Erin <erin@hashbang.sh>
Date: Sun, 4 Jun 2017 17:51:17 -0500
Subject: [PATCH] Remap the kernel! (finally)

---
 src/arch/x86_64/memory/mod.rs        |  2 +-
 src/arch/x86_64/memory/paging/mod.rs | 46 ++++++++++++++++++++++++++++++++++++
 src/lib.rs                           |  5 ++--
 3 files changed, 50 insertions(+), 3 deletions(-)

diff --git a/src/arch/x86_64/memory/mod.rs b/src/arch/x86_64/memory/mod.rs
index 346e82f..ef208a7 100644
--- a/src/arch/x86_64/memory/mod.rs
+++ b/src/arch/x86_64/memory/mod.rs
@@ -7,7 +7,7 @@ mod paging;
 
 pub use self::area_frame_allocator::AreaFrameAllocator;
 
-pub use self::paging::test_paging;
+pub use self::paging::remap_kernel;
 
 /// The physical size of each frame.
 pub const PAGE_SIZE: usize = 4096;
diff --git a/src/arch/x86_64/memory/paging/mod.rs b/src/arch/x86_64/memory/paging/mod.rs
index d293fb4..4823a56 100644
--- a/src/arch/x86_64/memory/paging/mod.rs
+++ b/src/arch/x86_64/memory/paging/mod.rs
@@ -3,12 +3,15 @@
 //! Extremely ripped off from Phil Oppermann's tutorials, because I don't feel like writing
 //! a paging system off the top of my head today.
 
+use core::ops::{Deref, DerefMut};
+use multiboot2::BootInformation;
 use super::PAGE_SIZE;
 use super::{Frame, FrameAllocator};
 
 mod entry;
 mod table;
 mod mapper;
+mod temporary_page;
 
 use self::entry::*;
 use self::table::{Table, Level4};
@@ -148,6 +151,49 @@ impl Page {
     }
 }
 
+/// Remap the kernel
+pub fn remap_kernel<A>(allocator: &mut A, boot_info: &BootInformation)
+        where A: FrameAllocator {
+
+    let mut scratch_page = TemporaryPage::new(Page { index: 0xabadcafe },
+        allocator);
+
+    let mut active_table = unsafe {ActivePageTable::new()};
+    let mut new_table = {
+        let frame = allocator.alloc_frame()
+            .expect("Attempted to allocate a frame for a new page table, but no frames are available!");
+        InactivePageTable::new(frame, &mut active_table, &mut scratch_page)
+    };
+
+    active_table.with(&mut new_table, &mut scratch_page, |mapper| {
+        let elf_sections_tag = boot_info.elf_sections_tag()
+            .expect("ELF sections tag required!");
+        for section in elf_sections_tag.sections() {
+            if !section.is_allocated() {
+                // section is not loaded to memory
+                continue;
+            }
+
+            assert!(section.start_address() % PAGE_SIZE == 0, "ELF sections must be page-aligned!");
+            debug!("Mapping section at addr: {:#x}, size: {:#x}",
+                section.addr, section.size);
+
+            let flags = WRITABLE;
+            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);
+            }
+        }
+
+        let vga_buffer_frame = Frame::containing_address(0xb8000);
+        mapper.identity_map(vga_buffer_frame, WRITABLE, allocator);
+    });
+
+    let old_table = active_table.switch(new_table);
+    info!("Successfully switched to new page table.");
+}
+
 /// Temporary function to test paging
 pub fn test_paging<A>(allocator: &mut A) where A: FrameAllocator {
     let mut page_table = unsafe {ActivePageTable::new()};
diff --git a/src/lib.rs b/src/lib.rs
index fcfc4e5..0bd9d73 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -63,8 +63,9 @@ pub extern fn kernel_main(multiboot_info_pointer: usize) {
         kernel_start as usize, kernel_end as usize, multiboot_start,
         multiboot_end, memory_map_tag.memory_areas());
 
-    memory::test_paging(&mut frame_allocator);
-    println!("-- memory paging test finished --");
+    memory::remap_kernel(&mut frame_allocator, boot_info);
+
+    println!("-- remap_kernel finished! --");
 
     loop {}
 }