From 063c065d2f61d54cefe7917b882764d27facf714 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Thomas=20Lov=C3=A9n?= <thomasloven@gmail.com>
Date: Fri, 29 Dec 2017 23:15:34 +0100
Subject: [PATCH] VMM - free_page unsets page

---
 src/kernel/memory/vmm.c  | 12 ++++++++++++
 src/kernel/memory/vmm.tt | 15 +++++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/src/kernel/memory/vmm.c b/src/kernel/memory/vmm.c
index e0bd1c3..c26049e 100644
--- a/src/kernel/memory/vmm.c
+++ b/src/kernel/memory/vmm.c
@@ -71,3 +71,15 @@ int touch_page(void *P4, uintptr_t addr, uint16_t flags)
 
   return 0;
 }
+
+void free_page(void *P4, uintptr_t addr, int free)
+{
+  (void)free;
+  if(!(P4
+      && P4e(P4, addr).present
+      && P3e(P4, addr).present
+      && P2e(P4, addr).present
+    ))
+    return;
+  P1e(P4, addr).value = 0;
+}
diff --git a/src/kernel/memory/vmm.tt b/src/kernel/memory/vmm.tt
index 846c9ff..8e41db0 100644
--- a/src/kernel/memory/vmm.tt
+++ b/src/kernel/memory/vmm.tt
@@ -155,3 +155,18 @@ TEST(touch_page_fails_if_out_of_pages)
   int retval = touch_page(p4, 0, 0);
   ASSERT_NEQ_INT(retval, 0);
 }
+
+TEST(free_page_unsets_page)
+{
+  p4[1] = (uintptr_t)p3;
+  p4[1] |= PAGE_PRESENT;
+  p3[2] = (uintptr_t)p2;
+  p3[2] |= PAGE_PRESENT;
+  p2[3] = (uintptr_t)p1;
+  p2[3] |= PAGE_PRESENT;
+  p1[4] = PAGE_PRESENT;
+
+  free_page(p4, ADDR1234, 0);
+
+  ASSERT_EQ_PTR(p1[4], 0);
+}