From 3134a1d6ad3dc234a9bbaa2cbbf5e4e7ea1927ce Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Thomas=20Lov=C3=A9n?= <thomasloven@gmail.com>
Date: Fri, 29 Dec 2017 23:33:48 +0100
Subject: [PATCH] VMM - free_page unsets P2 entry if P1 is empty

---
 src/kernel/memory/vmm.c  | 20 ++++++++++++++++++++
 src/kernel/memory/vmm.tt |  9 +++++++++
 2 files changed, 29 insertions(+)

diff --git a/src/kernel/memory/vmm.c b/src/kernel/memory/vmm.c
index c26049e..87b9058 100644
--- a/src/kernel/memory/vmm.c
+++ b/src/kernel/memory/vmm.c
@@ -82,4 +82,24 @@ void free_page(void *P4, uintptr_t addr, int free)
     ))
     return;
   P1e(P4, addr).value = 0;
+
+  union PTE *pt;
+
+  pt = PT(P2e(P4, addr).value);
+  for(int i = 0; i < ENTRIES_PER_PT; i++)
+    if(pt[i].value)
+      return;
+  P2e(P4, addr).value = 0;
+
+  pt = PT(P3e(P4, addr).value);
+  for(int i = 0; i < ENTRIES_PER_PT; i++)
+    if(pt[i].value)
+      return;
+  P3e(P4, addr).value = 0;
+
+  pt = PT(P4e(P4, addr).value);
+  for(int i = 0; i < ENTRIES_PER_PT; i++)
+    if(pt[i].value)
+      return;
+  P4e(P4, addr).value = 0;
 }
diff --git a/src/kernel/memory/vmm.tt b/src/kernel/memory/vmm.tt
index 29284c5..d8a9ffa 100644
--- a/src/kernel/memory/vmm.tt
+++ b/src/kernel/memory/vmm.tt
@@ -137,3 +137,12 @@ TEST(free_page_unsets_page)
 
   ASSERT_EQ_PTR(p1[4], 0);
 }
+TEST(free_page_unsets_P2_entry_if_P1_is_empty)
+{
+  BUILD_PT(1,2,3);
+  p1[4] = PAGE_PRESENT;
+
+  free_page(p4, ADDR1234, 1);
+
+  ASSERT_EQ_PTR(p2[3], 0);
+}