proc: implement basic mmap with files, real_program in arg

kernel/arch/x86_64/src/mem/process.rs

@@ -61,7 +61,7 @@ impl<TA: TableAllocator> ProcessAddressSpaceManager<TA> for ProcessAddressSpaceI
         self.write_l3_entry(address, PageEntry::page(physical, flags.into()), false)
     }
 
-    unsafe fn unmap_page(&mut self, address: usize) -> Result<PhysicalAddress, Error> {
+    unsafe fn unmap_page(&mut self, address: usize) -> Result<(PhysicalAddress, bool), Error> {
         self.pop_l3_entry(address)
     }
 
@@ -111,7 +111,7 @@ impl<TA: TableAllocator> ProcessAddressSpaceImpl<TA> {
         Ok(())
     }
 
-    fn pop_l3_entry(&mut self, virt: usize) -> Result<PhysicalAddress, Error> {
+    fn pop_l3_entry(&mut self, virt: usize) -> Result<(PhysicalAddress, bool), Error> {
         let l0i = virt.page_index::<L0>();
         let l1i = virt.page_index::<L1>();
         let l2i = virt.page_index::<L2>();
@@ -123,13 +123,14 @@ impl<TA: TableAllocator> ProcessAddressSpaceImpl<TA> {
         let mut l3 = l2.get_mut(l2i).ok_or(Error::DoesNotExist)?;
 
         let page = l3[l3i].as_page().ok_or(Error::DoesNotExist)?;
+        let dirty = l3[l3i].is_dirty();
 
         l3[l3i] = PageEntry::INVALID;
         unsafe {
             flush_tlb_entry(virt);
         }
 
-        Ok(page)
+        Ok((page, dirty))
     }
 
     fn read_l3_entry(&self, virt: usize) -> Option<(PhysicalAddress, MapAttributes)> {

kernel/arch/x86_64/src/mem/table.rs

@@ -31,6 +31,8 @@ bitflags! {
         /// For tables, allows user access to further translation levels, for pages/blocks, allows
         /// user access to the region covered by the entry
         const USER = 1 << 2;
+        /// If set, the page has been written to
+        const DIRTY = 1 << 6;
     }
 }
 
@@ -103,6 +105,10 @@ impl PageEntry<L3> {
             None
         }
     }
+
+    pub fn is_dirty(&self) -> bool {
+        self.0 & PageAttributes::DIRTY.bits() != 0
+    }
 }
 
 impl PageEntry<L2> {