Add virtual memory translation

src/lib.rs

@@ -24,6 +24,7 @@ use x86_64::instructions::bochs_breakpoint;
 
 pub mod gdt;
 pub mod interrupts;
+pub mod memory;
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 #[repr(u32)]

src/main.rs

@@ -41,7 +41,7 @@ fn panic(info: &PanicInfo) -> ! {
 entry_point!(kernel_main);
 
 // Kernel entry point
-fn kernel_main(_boot_info: &'static BootInfo) -> ! {
+fn kernel_main(boot_info: &'static BootInfo) -> ! {
     // TODO: Take care of cpuid stuff and set-up all floating point exetnsions
     // TODO: We may also need to enable debug registers ?
 
@@ -55,19 +55,33 @@ fn kernel_main(_boot_info: &'static BootInfo) -> ! {
 
     x86_64::instructions::interrupts::int3();
 
-    use x86_64::registers::control::Cr3;
+    use dendrobates_tinctoreus_azureus::memory;
+    use x86_64::VirtAddr;
+    use x86_64::structures::paging::{PageTable,MapperAllSizes};
 
-    let (level_4_page_table, flags) = Cr3::read();
-    println!(
-        "Level 4 page table at: {:?}, flags {:?}",
-        level_4_page_table.start_address(),
-        flags
-    );
-    serial_println!(
-        "Level 4 page table at: {:?}, flags {:?}",
-        level_4_page_table.start_address(),
-        flags
-    );
+
+    let phys_mem_offset = VirtAddr::new(boot_info.physical_memory_offset);
+    // new: initialize a mapper
+    let mapper = unsafe { memory::init(phys_mem_offset) };
+
+    let addresses = [
+        // the identity-mapped vga buffer page
+        0xb8000,
+        // some code page
+        0x201008,
+        // some stack page
+        0x0100_0020_1a10,
+        // virtual address mapped to physical address 0
+        boot_info.physical_memory_offset,
+    ];
+
+
+    for &address in &addresses {
+        let virt = VirtAddr::new(address);
+        // new: use the `mapper.translate_addr` method
+        let phys = mapper.translate_addr(virt);
+        serial_println!("{:?} -> {:?}", virt, phys);
+    }
 
     serial_println!("Preparing nasty fault...");
     unsafe {

src/memory.rs

@@ -0,0 +1,33 @@
+
+use x86_64::{structures::paging::{PageTable,OffsetPageTable}, VirtAddr, PhysAddr};
+
+
+/// 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: VirtAddr) -> OffsetPageTable<'static> {
+    let level_4_table = active_level_4_table(physical_memory_offset);
+    OffsetPageTable::new(level_4_table, physical_memory_offset)
+}
+/// Returns a mutable reference to the active level 4 table.
+///
+/// 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).
+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 = physical_memory_offset + phys.as_u64();
+    let page_table_ptr: *mut PageTable = virt.as_mut_ptr();
+
+    &mut *page_table_ptr // unsafe
+}