From 621c38faff56b1b1d3af353e562aef667e6620e9 Mon Sep 17 00:00:00 2001
From: Nathan Giddings <nathang567@gmail.com>
Date: Fri, 17 Jul 2020 12:31:54 -0500
Subject: [PATCH] Imlemented munmap and added some error checking

---
 src/mmgr/addressspace.cpp | 25 +++++++++++++++++++++----
 src/mmgr/addressspace.hpp |  4 ++--
 2 files changed, 23 insertions(+), 6 deletions(-)

diff --git a/src/mmgr/addressspace.cpp b/src/mmgr/addressspace.cpp
index 8056e8a..b325093 100644
--- a/src/mmgr/addressspace.cpp
+++ b/src/mmgr/addressspace.cpp
@@ -7,7 +7,7 @@ kernel::AddressSpace::AddressSpace(MemoryAllocator& malloc)
 	this->pageDirectory = (PageTableEntry*) 0xFFFFF000;
 }
 
-void* kernel::AddressSpace::mmap(void* start, size_t length)
+int kernel::AddressSpace::mmap(void* start, size_t length)
 {
 	size_t tableIndex = (size_t) start / 4096;
 	for(int i = (int) length; i > 0; i -= 4096)
@@ -16,6 +16,8 @@ void* kernel::AddressSpace::mmap(void* start, size_t length)
 		if(!pageDirectory[directoryIndex].getPresent())
 		{
 			physaddr_t newPT = malloc.allocate(4096);
+			if(newPT == 0)
+				return -1;
 			pageDirectory[directoryIndex] = newPT;
 			pageDirectory[directoryIndex].setPresent(true);
 			pageDirectory[directoryIndex].setUsermode(false);
@@ -31,12 +33,27 @@ void* kernel::AddressSpace::mmap(void* start, size_t length)
 		}
 		tableIndex++;
 	}
-	return start;
+	return 0;
 }
 
-void kernel::AddressSpace::munmap(void* start, size_t length)
+int kernel::AddressSpace::munmap(void* start, size_t length)
 {
-
+	if((size_t) start % 4096 != 0)
+		return -1;
+	size_t tableIndex = (size_t) start / 4096;
+	for(int i = (int) length; i > 0; i -= 4096)
+	{
+		size_t directoryIndex = tableIndex / 1024;
+		if(pageDirectory[directoryIndex].getPresent())
+		{
+			pageDirectory[directoryIndex] = 0;
+			pageDirectory[directoryIndex].setPresent(false);
+			pageDirectory[directoryIndex].setUsermode(false);
+			pageDirectory[directoryIndex].setRw(false);
+		}
+		tableIndex++;
+	}
+	return 0;
 }
 
 physaddr_t kernel::AddressSpace::getPhysicalAddress(void* virtualAddress)
diff --git a/src/mmgr/addressspace.hpp b/src/mmgr/addressspace.hpp
index eaba986..26073e0 100755
--- a/src/mmgr/addressspace.hpp
+++ b/src/mmgr/addressspace.hpp
@@ -14,9 +14,9 @@ public:
     
 	AddressSpace(MemoryAllocator& malloc);
 
-	void* mmap(void* start, size_t length);
+	int mmap(void* start, size_t length);
 
-	void munmap(void* start, size_t length);
+	int munmap(void* start, size_t length);
 
 	physaddr_t getPhysicalAddress(void* virtualAddress) const;