From 6e481f72aa0d2de7543512401e92fc7e1d1ff702 Mon Sep 17 00:00:00 2001
From: Nathan Cannon <neviynhd@gmail.com>
Date: Wed, 16 May 2018 00:42:37 +0100
Subject: [PATCH] Now only required number of kernel pages assigned.

---
 kernel/arch/i386/paging.nim | 15 ++++++++++++++-
 kernel/arch/i386/tty.nim    |  2 +-
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/kernel/arch/i386/paging.nim b/kernel/arch/i386/paging.nim
index b1f01f6..cb9ae02 100644
--- a/kernel/arch/i386/paging.nim
+++ b/kernel/arch/i386/paging.nim
@@ -9,6 +9,13 @@ type
 const 
   blankPageDirectory: PageDirectoryEntry = 0x00000002
 
+var
+  kernelMemoryStart{.importc: "_kernel_start"}: uint32
+  kernelMemoryEnd{.importc: "_kernel_end"}: uint32
+
+proc kernelMemoryStartAddress(): uint32 = cast[uint32](kernelMemoryStart.addr)
+proc kernelMemoryEndAddress(): uint32 = cast[uint32](kernelMemoryEnd.addr)
+
 var
   pageDirectory: ptr PageDirectory
   pageTable0{.exportc, codegenDecl: "$# $# __attribute__((aligned(0x1000)))".}: PageTable
@@ -54,7 +61,13 @@ proc init*() =
   pageDirectory = cast[ptr PageDirectory](toVirtual(pagingAddress))
   for i in 0..767:
     pageDirectory[][i] = blankPageDirectory
-  for i in 0..1023:
+  var pages: uint = uint(int(kernelMemoryEndAddress() - 0xC0000000'u32) / 0x1000)
+  serial.write("Pages:")
+  serial.writeLine(pages)
+  # Assign VGA memory area to 0xC0000000
+  pageTable0[0] = createEntry(address = 0xB8000, readWrite = true, present = true)
+  # Assign kernel memory pages to 0xC0100000+
+  for i in 256..pages:
     pageTable0[i] = createEntry(address = uint32(i) * 0x1000, readWrite = true, present = true)
   pageDirectory[][768] = createDirectory(address = toPhysical(cast[uint32](pageTable0.addr)), readWrite = true, present = true)
   for i in 769..1023:
diff --git a/kernel/arch/i386/tty.nim b/kernel/arch/i386/tty.nim
index cbf9a10..69c10b4 100644
--- a/kernel/arch/i386/tty.nim
+++ b/kernel/arch/i386/tty.nim
@@ -8,7 +8,7 @@ type
   VGAMemory = ptr array[0..(vgaWidth * vgaHeight - 1), VGADoubleByte]
 
 const
-  terminalBufferBaseAddress = 0xC00B8000
+  terminalBufferBaseAddress = 0xC0000000
   vgaMem = cast[VGAMemory](terminalBufferBaseAddress)
 
 var