From d54a206f82739c43af052ee799524170316d6184 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Thomas=20Lov=C3=A9n?= <thomasloven@gmail.com>
Date: Sat, 30 Dec 2017 13:16:20 +0100
Subject: [PATCH] VMM - free_page returns P1 to PMM if empty

---
 src/kernel/memory/vmm.c  |  3 +++
 src/kernel/memory/vmm.tt | 16 ++++++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/src/kernel/memory/vmm.c b/src/kernel/memory/vmm.c
index e3c6ac5..4052cd8 100644
--- a/src/kernel/memory/vmm.c
+++ b/src/kernel/memory/vmm.c
@@ -91,17 +91,20 @@ void free_page(void *P4, uintptr_t addr, int free)
   for(int i = 0; i < ENTRIES_PER_PT; i++)
     if(pt[i].value)
       return;
+  pmm_free(MASK_FLAGS(P2e(P4, addr).value));
   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;
+  pmm_free(MASK_FLAGS(P3e(P4, addr).value));
   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;
+  pmm_free(MASK_FLAGS(P4e(P4, addr).value));
   P4e(P4, addr).value = 0;
 }
diff --git a/src/kernel/memory/vmm.tt b/src/kernel/memory/vmm.tt
index a505d67..21773a1 100644
--- a/src/kernel/memory/vmm.tt
+++ b/src/kernel/memory/vmm.tt
@@ -165,3 +165,19 @@ TEST(free_page_does_not_unset_P2_entry_if_P1_is_not_empty)
 
   ASSERT_NEQ_PTR(p2[3], 0);
 }
+
+uintptr_t freed[] = {0,0,0,0,0};
+void pmm_free(uintptr_t page)
+{
+  static int counter = 0;
+  freed[counter++] = page;
+}
+TEST(free_page_returns_P1_to_PMM_if_empty)
+{
+  BUILD_PT(1,2,3);
+  p1[4] = PAGE_PRESENT;
+
+  free_page(p4, ADDR1234, 1);
+
+  ASSERT_EQ_PTR(freed[0], p1);
+}