From fb88d1669f3a28d2e8ee84266c8aa3ce0bce8eb1 Mon Sep 17 00:00:00 2001
From: Jeremy Soller <jeremy@system76.com>
Date: Tue, 8 Sep 2020 19:59:13 -0600
Subject: [PATCH] Add unmap function

---
 src/main.rs        | 10 ++++++++++
 src/page/mapper.rs | 23 +++++++++++++++++++++++
 2 files changed, 33 insertions(+)

diff --git a/src/main.rs b/src/main.rs
index eb899ca8df..801389fbe4 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -228,6 +228,16 @@ unsafe fn new_tables<A: Arch>(areas: &'static [MemoryArea]) {
         flush_all.consume(flush);
     }
     flush_all.flush();
+
+    let flush_all = PageFlushAll::new();
+    for i in 0..16 {
+        let virt = VirtualAddress::new(MEGABYTE + i * A::PAGE_SIZE);
+        let flush = mapper.unmap(
+            virt,
+        ).expect("failed to unmap page");
+        flush_all.consume(flush);
+    }
+    flush_all.flush();
 }
 
 unsafe fn inner<A: Arch>() {
diff --git a/src/page/mapper.rs b/src/page/mapper.rs
index 0c9b03e6eb..524e170719 100644
--- a/src/page/mapper.rs
+++ b/src/page/mapper.rs
@@ -78,4 +78,27 @@ impl<'f, A: Arch, F: FrameAllocator> PageMapper<'f, A, F> {
             }
         }
     }
+
+    pub unsafe fn unmap(&mut self, virt: VirtualAddress) -> Option<PageFlush<A>> {
+        let (old, flush) = self.unmap_phys(virt)?;
+        self.allocator.free_one(old.address());
+        Some(flush)
+    }
+
+    pub unsafe fn unmap_phys(&mut self, virt: VirtualAddress) -> Option<(PageEntry<A>, PageFlush<A>)> {
+        //TODO: verify virt is aligned
+        let mut table = self.table();
+        //TODO: unmap parents
+        loop {
+            let i = table.index_of(virt)?;
+            if table.level() == 0 {
+                let entry_opt = table.entry(i);
+                table.set_entry(i, PageEntry::new(0));
+                let entry = entry_opt?;
+                return Some((entry, PageFlush::new(virt)));
+            } else {
+                table = table.next(i)?;
+            }
+        }
+    }
 }