From 4f3e22140c164359bd13de0778dc3bee4979286b Mon Sep 17 00:00:00 2001
From: Jonas 'Sortie' Termansen <sortie@maxsi.org>
Date: Sat, 17 Mar 2012 18:14:57 +0100
Subject: [PATCH] Fixed x64 memory leaks upon process termination.

---
 sortix/x64/boot.s               |  4 ++--
 sortix/x64/memorymanagement.cpp | 22 ++++++++++++++++++++--
 sortix/x86/memorymanagement.cpp |  3 ++-
 3 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/sortix/x64/boot.s b/sortix/x64/boot.s
index aa7744f7..53286351 100644
--- a/sortix/x64/boot.s
+++ b/sortix/x64/boot.s
@@ -78,8 +78,8 @@ multiboot_entry:
 	addl $0x1000, %edi
 
 	# Page-Directory (no user-space access here)
-	movl $0x24203, (%edi) # (First 2 MiB)
-	movl $0x25203, 8(%edi) # (Second 2 MiB)
+	movl $0x24003, (%edi) # (First 2 MiB)
+	movl $0x25003, 8(%edi) # (Second 2 MiB)
 	addl $0x1000, %edi
 
 	# Page-Table
diff --git a/sortix/x64/memorymanagement.cpp b/sortix/x64/memorymanagement.cpp
index a12ac52f..97eb28aa 100644
--- a/sortix/x64/memorymanagement.cpp
+++ b/sortix/x64/memorymanagement.cpp
@@ -35,6 +35,7 @@ namespace Sortix
 	{
 		extern size_t stackused;
 		extern size_t stacklength;
+		void ExtendStack();
 	}
 
 	namespace Memory
@@ -131,17 +132,34 @@ namespace Sortix
 
 		void DestroyAddressSpace()
 		{
+			// Look up the last few entries used for the fractal mapping. These
+			// cannot be unmapped as that would destroy the world. Instead, we
+			// will remember them, switch to another adress space, and safely
+			// mark them as unused. Also handling the forking related pages.
+			addr_t fractal3 = (PMLS[4] + 0)->entry[510UL];
+			addr_t fork2 = (PMLS[3] + 510UL)->entry[0];
+			addr_t fractal2 = (PMLS[3] + 510UL)->entry[510];
+			addr_t fork1 = (PMLS[2] + 510UL * 512UL + 510UL)->entry[0];
+			addr_t fractal1 = (PMLS[2] + 510UL * 512UL + 510UL)->entry[510];
+			addr_t dir = currentdir;
+
 			// First let's do the safe part. Garbage collect any PML1/0's left
 			// behind by user-space. These are completely safe to delete.
 			RecursiveFreeUserspacePages(TOPPMLLEVEL, 0);
 
-			// TODO: Right now this just leaks memory.
-
 			// Switch to the address space from when the world was originally
 			// created. It should contain the kernel, the whole kernel, and
 			// nothing but the kernel.
 			PML* const BOOTPML4 = (PML* const) 0x21000UL;
 			SwitchAddressSpace((addr_t) BOOTPML4);
+
+			// Now safely mark the pages as unused.
+			Page::Put(fractal3 & PML_ADDRESS);
+			Page::Put(fractal2 & PML_ADDRESS);
+			Page::Put(fractal1 & PML_ADDRESS);
+			Page::Put(fork2 & PML_ADDRESS);
+			Page::Put(fork1 & PML_ADDRESS);
+			Page::Put(dir & PML_ADDRESS);
 		}
 
 		const size_t KERNEL_STACK_SIZE = 256UL * 1024UL;
diff --git a/sortix/x86/memorymanagement.cpp b/sortix/x86/memorymanagement.cpp
index 74032e11..18d0c0e7 100644
--- a/sortix/x86/memorymanagement.cpp
+++ b/sortix/x86/memorymanagement.cpp
@@ -140,7 +140,8 @@ namespace Sortix
 
 			// Make sure Page::Put does NOT cause any Page::Get's internally!
 			const size_t NUM_PAGES = 2;
-			if ( Page::stacklength - Page::stackused < NUM_PAGES ) { Page::ExtendStack(); }
+			size_t pagestackfree = Page::stacklength - Page::stackused;
+			if ( pagestackfree < NUM_PAGES ) { Page::ExtendStack(); }
 
 			addr_t fractal1 = PMLS[2]->entry[1022];