KERNEL: Implementing VMM & cleaning up

Folders now are alll lower case

Started working on the implementation of the Virtual memory manager. Implemented allocate and free page funtionality for as far as I can atm.

Implemented the

Makefile

@@ -5,7 +5,7 @@ CC = ${HOME}/opt/cross/bin/i686-elf-gcc
 CPP = ${HOME}/opt/cross/bin/i686-elf-g++ 
 CFLAGS =  -ffreestanding -Og -ggdb  -Wall -Wextra
 
-OFILES =$(BUILD_DIR)/boot.o $(BUILD_DIR)/kterm.o $(BUILD_DIR)/kernel.o $(BUILD_DIR)/memory.o  $(BUILD_DIR)/paging.o	$(BUILD_DIR)/pit.o 	$(BUILD_DIR)/time.o	$(BUILD_DIR)/keyboard.o	 $(BUILD_DIR)/io.o 	$(BUILD_DIR)/gdtc.o $(BUILD_DIR)/idt.o $(BUILD_DIR)/pic.o $(BUILD_DIR)/sv-terminal.o $(BUILD_DIR)/string.o  $(BUILD_DIR)/prekernel.o
+OFILES =$(BUILD_DIR)/boot.o $(BUILD_DIR)/kterm.o $(BUILD_DIR)/kernel.o $(BUILD_DIR)/memory.o  $(BUILD_DIR)/paging.o	$(BUILD_DIR)/pit.o 	$(BUILD_DIR)/time.o	$(BUILD_DIR)/keyboard.o	 $(BUILD_DIR)/io.o 	$(BUILD_DIR)/gdtc.o $(BUILD_DIR)/idt.o $(BUILD_DIR)/pic.o $(BUILD_DIR)/sv-terminal.o $(BUILD_DIR)/string.o  $(BUILD_DIR)/prekernel.o $(BUILD_DIR)/cpu.o
 
 SRC_DIR = source
 BUILD_DIR = build
@@ -55,7 +55,7 @@ $(BUILD_DIR)/kernel.o:
 	$(CPP) -c $(SRC_DIR)/kernel/kernel.cpp -o $(BUILD_DIR)/kernel.o $(CFLAGS) -fno-exceptions -fno-rtti
 
 $(BUILD_DIR)/kterm.o:
-	$(CPP) -c $(SRC_DIR)/kernel/Terminal/kterm.cpp  -o $(BUILD_DIR)/kterm.o $(CFLAGS) -fno-exceptions -fno-rtti
+	$(CPP) -c $(SRC_DIR)/kernel/terminal/kterm.cpp  -o $(BUILD_DIR)/kterm.o $(CFLAGS) -fno-exceptions -fno-rtti
 
 $(BUILD_DIR)/boot.o:
 	$(AS) $(SRC_DIR)/kernel/boot/boot.s -o $(BUILD_DIR)/boot.o
@@ -71,38 +71,41 @@ $(BUILD_DIR)/io.o:
 
 
 $(BUILD_DIR)/idt.o:
-	$(CPP) -c $(SRC_DIR)/kernel/Interrupts/idt/idt.cpp -o $(BUILD_DIR)/idt.o $(CFLAGS) -fno-exceptions -fno-rtti
+	$(CPP) -c $(SRC_DIR)/kernel/interrupts/idt/idt.cpp -o $(BUILD_DIR)/idt.o $(CFLAGS) -fno-exceptions -fno-rtti
 
 $(BUILD_DIR)/gdtc.o:
-	$(CPP) -c $(SRC_DIR)/kernel/Memory/GDT/gdtc.cpp -o $(BUILD_DIR)/gdtc.o $(CFLAGS) -fno-exceptions -fno-rtti
+	$(CPP) -c $(SRC_DIR)/kernel/memory/gdt/gdtc.cpp -o $(BUILD_DIR)/gdtc.o $(CFLAGS) -fno-exceptions -fno-rtti
 
 
 $(BUILD_DIR)/pic.o:
-	$(CPP) -c $(SRC_DIR)/kernel/Drivers/PIC/pic.cpp -o $(BUILD_DIR)/pic.o $(CFLAGS) -fno-exceptions -fno-rtti
+	$(CPP) -c $(SRC_DIR)/kernel/drivers/pic/pic.cpp -o $(BUILD_DIR)/pic.o $(CFLAGS) -fno-exceptions -fno-rtti
 
 $(BUILD_DIR)/string.o:
-	$(CC) -c $(SRC_DIR)/kernel/Lib/string.c  -o $(BUILD_DIR)/string.o $(CFLAGS) -std=gnu99
+	$(CC) -c $(SRC_DIR)/kernel/lib/string.c  -o $(BUILD_DIR)/string.o $(CFLAGS) -std=gnu99
 
 
 $(BUILD_DIR)/pit.o:
-	$(CPP) -c $(SRC_DIR)/kernel/Drivers/PIT/pit.cpp  -o $(BUILD_DIR)/pit.o $(CFLAGS) -fno-exceptions -fno-rtti
+	$(CPP) -c $(SRC_DIR)/kernel/drivers/pit/pit.cpp  -o $(BUILD_DIR)/pit.o $(CFLAGS) -fno-exceptions -fno-rtti
 
 
 $(BUILD_DIR)/keyboard.o:
-	$(CPP) -c $(SRC_DIR)/kernel/Drivers/PS-2/keyboard.cpp  -o $(BUILD_DIR)/keyboard.o $(CFLAGS) -fno-exceptions -fno-rtti
+	$(CPP) -c $(SRC_DIR)/kernel/drivers/ps-2/keyboard.cpp  -o $(BUILD_DIR)/keyboard.o $(CFLAGS) -fno-exceptions -fno-rtti
 
 
 $(BUILD_DIR)/time.o:
 	$(CPP) -c $(SRC_DIR)/kernel/time.cpp  -o $(BUILD_DIR)/time.o $(CFLAGS) -fno-exceptions -fno-rtti
 
 $(BUILD_DIR)/sv-terminal.o:
-	$(CPP) -c $(SRC_DIR)/kernel/SuperVisorTerminal/superVisorTerminal.cpp  -o $(BUILD_DIR)/sv-terminal.o $(CFLAGS) -fno-exceptions -fno-rtti
+	$(CPP) -c $(SRC_DIR)/kernel/supervisorterminal/superVisorTerminal.cpp  -o $(BUILD_DIR)/sv-terminal.o $(CFLAGS) -fno-exceptions -fno-rtti
 
 $(BUILD_DIR)/memory.o:
-	$(CPP) -c $(SRC_DIR)/kernel/Memory/PhysicalMemoryManager.cpp  -o $(BUILD_DIR)/memory.o $(CFLAGS) -fno-exceptions -fno-rtti
+	$(CPP) -c $(SRC_DIR)/kernel/memory/PhysicalMemoryManager.cpp  -o $(BUILD_DIR)/memory.o $(CFLAGS) -fno-exceptions -fno-rtti
 
 $(BUILD_DIR)/paging.o:
-	$(CPP) -c $(SRC_DIR)/kernel/Memory/VirtualMemoryManager.cpp -o $(BUILD_DIR)/paging.o $(CFLAGS) -fno-exceptions -fno-rtti
+	$(CPP) -c $(SRC_DIR)/kernel/memory/VirtualMemoryManager.cpp -o $(BUILD_DIR)/paging.o $(CFLAGS) -fno-exceptions -fno-rtti
 
 $(BUILD_DIR)/prekernel.o:
-	$(CPP) -c $(SRC_DIR)/kernel/PreKernel/prekernel.cpp -o $(BUILD_DIR)/prekernel.o $(CFLAGS) -fno-exceptions -fno-rtti
+	$(CPP) -c $(SRC_DIR)/kernel/prekernel/prekernel.cpp -o $(BUILD_DIR)/prekernel.o $(CFLAGS) -fno-exceptions -fno-rtti
+
+$(BUILD_DIR)/cpu.o:
+	$(CPP) -c $(SRC_DIR)/kernel/cpu.cpp -o $(BUILD_DIR)/cpu.o $(CFLAGS) -fno-exceptions -fno-rtti

source/kernel/Memory/VirtualMemoryManager.cpp

@@ -1,24 +0,0 @@
-#include "VirtualMemoryManager.h"
-
-extern "C" void loadPageDirectory (uint32_t* addr );
-extern "C" void enablePaging();
-
-void AllocatePage(uint32_t vaddr)
-{
-
-}
-
-void FreePage(uint32_t vaddr )
-{
-
-}
-
-void Map (  uint32_t vaddr, uint32_t paddr)
-{
-
-}
-
-void Unmap(uint32_t vaddr)
-{
-    // NOTE: I will implement lazy unmapping for now 
-}

source/kernel/SuperVisorTerminal/superVisorTerminal.h

@@ -1,8 +0,0 @@
-#pragma once 
-#include "../Terminal/kterm.h"
-#include "../time.h"
-#include "../Drivers/PIT/pit.h"
-#include "../Drivers/PS-2/keyboard.h"
-#include "../Memory/PhysicalMemoryManager.h"
-
-void startSuperVisorTerminal();

source/kernel/boot/boot.s

@@ -17,6 +17,7 @@ stack_top:
 .globl boot_page_directory
 boot_page_directory:
 	.skip 4096
+.globl boot_page_table
 boot_page_table:
 	.skip 4096
 .globl multiboot_page_table
@@ -60,15 +61,6 @@ _start:
 3:	# Map VGA video memory to 0xC03FF00 as "present, writable"
 	movl $(0x000B8000 | 0x003), boot_page_table - 0xC0000000 + 1023 * 4
 
-	# IMPORTANT NOTE FROM WIKI.OSDEV.ORG/HIGHER_HALF_X86_BARE_BONES
-
-	# The page table is used at both page directory entry 0 (virtually from 0x0
-	# to 0x3FFFFF) (thus identity mapping the kernel) and page directory entry
-	# 768 (virtually from 0xC0000000 to 0xC03FFFFF) (thus mapping it in the
-	# higher half). The kernel is identity mapped because enabling paging does
-	# not change the next instruction, which continues to be physical. The CPU
-	# would instead page fault if there was no identity mapping.\
-	
 	# Map the page table to both virtual addresss 0x00000000 and 0xC0000000
 	movl $(boot_page_table - 0xC0000000 + 0x003), boot_page_directory - 0xC0000000 + 0
 	movl $(boot_page_table - 0xC0000000 + 0x003), boot_page_directory - 0xC0000000 + 768 * 4
@@ -112,10 +104,9 @@ isPaging:
 	jmp 1b
 
 
-.include "./source/kernel/Memory/GDT/gdt.s"
+.include "./source/kernel/memory/gdt/gdt.s"
 .include "./source/kernel/irs_table.s"
 .include "./source/kernel/irq_table.s"
-.include "./source/kernel/Interrupts/idt/idt.s"
-.include "./source/kernel/cpu.s"
+.include "./source/kernel/interrupts/idt/idt.s"
 
 

source/kernel/cpu.cpp

@@ -0,0 +1,39 @@
+#include "cpu.h"
+
+
+uint32_t GetEFLAGS()
+{
+    uint32_t EFLAGS = 0;
+    asm volatile ("pushfl;" "movl 4(%%esp), %%edx" : "=d"(EFLAGS));
+    return EFLAGS;
+}
+
+
+uint32_t GetCR0()
+{   
+    uint32_t cr0_value;
+    asm volatile ("movl %%cr0, %%edx" : "=d"(cr0_value));
+    return cr0_value;
+
+}
+
+
+uint32_t GetCR2(){
+    uint32_t cr2_value;
+    __asm__ volatile("movl %%cr2, %%edx": "=d"(cr2_value));
+    return cr2_value;
+}
+
+
+uint32_t GetCR3(){
+    uint32_t cr3_value;
+    __asm__ volatile("movl %%cr3, %%edx": "=d"(cr3_value));
+    return cr3_value;
+}
+
+
+uint32_t GetCR4(){
+    uint32_t cr4_value;
+    __asm__ volatile("movl %%cr4, %%edx": "=d"(cr4_value));
+    return cr4_value;
+}

source/kernel/cpu.h

@@ -9,19 +9,18 @@ C++ interface for the cpu.s assembly file.
 ©Nigel Barink - 2022 
 */
 
-
 /*
 *       EFLAGS FUNCTIONS
 */
 
-extern "C" uint32_t GetEFLAGS();
+uint32_t GetEFLAGS();
 
 
 
 /*
 *       CONTROL_REGISTER_0 FUNCTIONS
 */
-extern "C" uint32_t GetCR0();
+uint32_t GetCR0();
 
 /*
  struct CR0_Register  {
@@ -57,7 +56,7 @@ extern "C" uint32_t GetCR0();
 *       CONTROL_REGISTER_4 FUNCTIONS
 */
 
-extern "C" uint32_t GetCR4();
+uint32_t GetCR4();
 
 #define GET_PSE_BIT(CONTROL_REGISTER_4) (CONTROL_REGISTER_4&0x4)
 #define GET_PAE_BIT(CONTROL_REGISTER_4) (CONTROL_REGISTER_4&0x5)
@@ -66,10 +65,10 @@ extern "C" uint32_t GetCR4();
 *       CONTROL_REGISTER_2 FUNCTIONS
 */
 
-extern "C" uint32_t GetCR2();
+uint32_t GetCR2();
 
 /*
 *       CONTROL_REGISTER_3 FUNCTIONS
 */
 
-extern "C" uint32_t GetCR3();
+uint32_t GetCR3();

source/kernel/cpu.s

@@ -1,63 +0,0 @@
-# Basic cpu functions 
-.globl GetCR0
-GetCR0:
-	push %ebp # save the base pointer on the stack
-	mov %esp, %ebp  # Set the base pointer to the current stack pointer 
-
-	xor %eax, %eax # Clear EAX to make sure no weird stuff is going on
-	mov %cr0, %eax # Copy the value of the CR0 register into EAX
-
-	mov %ebp, %esp # restore the base pointer 
-	pop %ebp
-	ret
-
-.globl GetCR4
-GetCR4:
-	push %ebp
-	mov %esp, %ebp
-
-	xor %eax, %eax
-	mov %cr4, %eax 
-
-	mov %ebp, %esp 
-	pop %ebp
-	ret
-
-
-
-.globl GetEFLAGS
-GetEFLAGS:
-	push %ebp 
-	mov %esp, %ebp
-
-	xor %eax, %eax 
-	pushfl # Push the EFLAGS register content onto the stack, should be pushfd but GAS apparently doesn't agree
-	mov 4(%esp) , %eax
-
-	mov %ebp, %esp
-	pop %ebp
-	ret
-
-.globl GetCR2
-GetCR2:
-	push %ebp
-	mov %esp, %ebp
-
-	xor %eax, %eax
-	mov %cr2, %eax
-	
-	mov %ebp, %esp
-	pop %ebp
-	ret
-	
-.globl GetCR3
-GetCR3:
-	push %ebp
-	mov %esp, %ebp
-
-	xor %eax, %eax
-	mov %cr3, %eax
-	
-	mov %ebp, %esp
-	pop %ebp
-	ret

source/kernel/drivers/pit/pit.cpp

@@ -1,5 +1,5 @@
 #include "pit.h"
-#include "../../Terminal/kterm.h"
+
 uint32_t pit_tick = 0;
 
 

source/kernel/drivers/pit/pit.h

@@ -1,6 +1,7 @@
 #pragma once 
 #include <stdint.h>
 #include "../../io.h"
+#include "../../terminal/kterm.h"
 #define PIT_DATA_0 0x40
 #define PIT_DATA_1 0x41
 #define PIT_DATA_2 0x42

source/kernel/drivers/ps-2/keyboard.h

@@ -1,6 +1,6 @@
 #pragma once
 #include <stdint.h>
-#include "../../Terminal/kterm.h"
+#include "../../terminal/kterm.h"
 enum ScanCodeSet {
     None            =   0,
     ScanCodeSet1    =   1,

source/kernel/interrupts/idt/idt.cpp

@@ -1,6 +1,6 @@
 #include "idt.h"
-#include "../../Drivers/PIT/pit.h"
-#include "../../Drivers/PS-2/keyboard.h"
+#include "../../drivers/pit/pit.h"
+#include "../../drivers/ps-2/keyboard.h"
 #include "../../cpu.h"
 IDT_entry idt_table[256];
 IDT_ptr idt_ptr;

source/kernel/interrupts/idt/idt.h

@@ -2,10 +2,10 @@
 
 #include <stdint.h>
 #include <stddef.h>
-#include "../../Drivers/VGA/colors.h"
-#include "../../Drivers/PIC/pic.h"
+#include "../../drivers/vga/colors.h"
+#include "../../drivers/pic/pic.h"
 
-#include "../../Terminal/kterm.h"
+#include "../../terminal/kterm.h"
 
 
 extern "C" {

source/kernel/kernel.cpp

@@ -1,11 +1,6 @@
 #include "kernel.h"
 extern "C" void early_main()
 {
-    /*
-     * Initialize terminal interface 
-     */ 
-
-
     kterm_init();
     initGDT();
 
@@ -64,10 +59,11 @@ extern "C" void early_main()
         printf("MemoryInfoheap size : %d bytes\n", BootInfo->map_size);
         // Print the memory regions 
         MemoryInfoBlock* currentBlock = (MemoryInfoBlock*) ((uint32_t)BootInfo->MemoryMap + KERNEL_BASE_ADDR) ;
-  
+
         printf( "Starting address: 0x%x\n", currentBlock);
         while( (uint32_t)currentBlock->next != 0x0 )
         {
+            printf("CurrentBlock: 0x%x \n", (uint32_t ) currentBlock );
             if(IS_AVAILABLE_MEM(currentBlock->type)){
                 //printf("AVAILABLE RAM\n");
             }
@@ -91,11 +87,12 @@ extern "C" void early_main()
           
         }
 
+        printf("Starting physical memory management setup\n");
         // Setup PhysicalMemoryManagement
         SetupPhysicalMemoryManager(BootInfo);
      
     }
-    
+    printf("Enable Protected mode and jump to kernel main\n");
 	asm volatile("mov %cr0, %eax ");
     asm volatile("or $1, %eax");
     asm volatile("mov %eax, %cr0"); // re-enable protected mode ? 

source/kernel/kernel.h

@@ -1,27 +1,27 @@
 #pragma once
 extern "C" 
 {
-   #include "Lib/string.h" 
+   #include "lib/string.h" 
 }
 #include "definitions.h"
 
-#include "Drivers/VGA/VBE.h"
-#include "Terminal/kterm.h"
+#include "drivers/vga/VBE.h"
+#include "terminal/kterm.h"
 
-#include "Memory/PhysicalMemoryManager.h"
-#include "Memory/VirtualMemoryManager.h"
+#include "memory/PhysicalMemoryManager.h"
+#include "memory/VirtualMemoryManager.h"
 
-#include "Memory/GDT/gdtc.h"
-#include "Interrupts/idt/idt.h"
+#include "memory/gdt/gdtc.h"
+#include "interrupts/idt/idt.h"
 
-#include "Drivers/PIT/pit.h"
+#include "drivers/pit/pit.h"
 #include "io.h"
 #include "cpu.h"
 #include "serial.h"
 
 #include "time.h"
-#include "SuperVisorTerminal/superVisorTerminal.h"
-#include "PreKernel/bootstructure.h"
+#include "supervisorterminal/superVisorTerminal.h"
+#include "prekernel/bootstructure.h"
 
 #define CHECK_FLAG(flag, bit) ( flag & (1 << bit ))
 #define PANIC(message) {return;} 

source/kernel/memory/KernelHeap.cpp

@@ -14,6 +14,7 @@ void* malloc(size_t size)
     printf("Received request for %d bytes of memory", size);
     heap_block* current = start;
 
+    // look for a free block
     while(current <  start + heap_size)
     {
         if(current->size >= size && current->Used == false )
@@ -33,7 +34,7 @@ void* malloc(size_t size)
 
     // If we are here we need more memory so we should 
     // probably ask the VMM for more 
-    // TODO: ask for more memory
+    // TODO: ask for more memory | Extend kernel heap
     
 }
 

source/kernel/memory/PhysicalMemoryManager.cpp

@@ -1,29 +1,33 @@
 #include "./PhysicalMemoryManager.h"
 
 PhysicalMemoryManagerInfoBlock* PMMInfoBlock;
+extern uint32_t* boot_page_directory;
+extern uint32_t* boot_page_table;
 
 const uint32_t KERNEL_OFFSET = 0xC0000000;
 void SetupPhysicalMemoryManager( BootInfoBlock* Bootinfo) {
-
-    PMMInfoBlock = (PhysicalMemoryManagerInfoBlock*) ((uint32_t)MemoryMapHeap_pptr + Bootinfo->map_size + 0xC0000000);
-
+    // NOTE: Physical memory map will override the boot info for now!
+    PMMInfoBlock = (PhysicalMemoryManagerInfoBlock*) (&BootInfoBlock_pptr + KERNEL_OFFSET );
+    printf("Setting up physical memory infoblock (0x%x) \n", (uint32_t)&PMMInfoBlock);
     /*
         Every byte contains 8 pages
         A page is 4096 kib 
         Every block (1 bit) represent an page 
     */
-    // calculate the maximum number of blocks
-    PMMInfoBlock->max_blocks =Bootinfo->MemorySize / BLOCK_SIZE / 8;
-    PMMInfoBlock->used_blocks = 0;
 
+    // Calculate the maximum number of blocks
+    printf("Maxblocks at address(0x%x)\n" , (uint32_t)&(PMMInfoBlock->max_blocks));
+
+    int maximum_blocks = (uint32_t)Bootinfo->MemorySize / BLOCK_SIZE / 8;
+    printf("Set bitmap block maximum: %d\n", maximum_blocks);
+    PMMInfoBlock->max_blocks = maximum_blocks;
+
+    printf("Set used blocks to zero\n");
+    PMMInfoBlock->used_blocks = 0;
+    
+    printf("Determine memory bit map address");
     // put the map after the gdt
     PMMInfoBlock->memoryBitMap = (uint32_t*) ( 0xC010b100) ;
-
-    // // Page in the address space please 
-    // uint32_t PDEI =  0xC020a000 >> 22;
-    // uint32_t PTEI = (0xC020a000 >> 12) & 0x1FFF;
-    // printf("PDEI: %d, PTEI: %d\n", PDEI, PTEI);
-
     
     printf("Maximum num blocks: %d \n",PMMInfoBlock->max_blocks);
     //Size of memory map 
@@ -54,7 +58,7 @@ void SetupPhysicalMemoryManager( BootInfoBlock* Bootinfo) {
     printf("kernel size in memory: 0x%x\n", kernel_size);
     allocate_region((uint32_t)&kernel_begin, kernel_size);
 
-    printf("allocate BIOS region");
+    printf("allocate BIOS region\n");
     allocate_region (0x0000000, 0x00100000);
 }
 

source/kernel/memory/PhysicalMemoryManager.h

@@ -1,8 +1,8 @@
 #pragma once
 #include <stddef.h>
-#include "../PreKernel/bootstructure.h"
-#include "../Terminal/kterm.h"
-#include "../Lib/mem.h"
+#include "../prekernel/bootstructure.h"
+#include "../terminal/kterm.h"
+#include "../lib/mem.h"
 #include "../bitmap.h"
 
 // Asumming i386 for now!
@@ -14,8 +14,8 @@
 struct PhysicalMemoryManagerInfoBlock
 {
     uint32_t* memoryBitMap;
-    size_t pmmap_size;
-    size_t max_blocks;
+    uint32_t pmmap_size;
+    uint32_t max_blocks;
     int used_blocks;
 };
 

source/kernel/memory/VirtualMemoryManager.cpp

@@ -0,0 +1,73 @@
+#include "VirtualMemoryManager.h"
+extern uint32_t boot_page_directory[1024] ;
+extern uint32_t boot_page_table[1024];
+void AllocatePage(uint32_t vaddr)
+{
+    uint32_t page_aligned_address = ALIGN(vaddr, 4096);
+
+    // allocate a page at  virtual address
+    int PageDirectoryEntryIndex = vaddr >> 22;
+    int PageTableEntryIndex = (vaddr >> 12) & 0x1FFF;
+
+    printf("Allocation happening at PDE: %d PTE: %d\n", PageDirectoryEntryIndex, PageTableEntryIndex);
+
+    // check if the page directory entry is marked as present 
+    if (boot_page_directory[PageDirectoryEntryIndex] & 0x1 ) {
+
+        uint32_t* page_table = (uint32_t*)((boot_page_directory[PageDirectoryEntryIndex]) & 0xFFFFE000 + 0xC0000000);
+
+        // check if the page table entry is marked as present 
+        if ( page_table[PageTableEntryIndex] & 0x1 )
+        {   
+            // Map the entry to a physical page
+            page_table[PageTableEntryIndex] = (uint32_t)(allocate_block() + 0x3);
+        } else{
+            // mark page as present
+            page_table[PageTableEntryIndex] =   0x3;
+        }
+
+    } else {
+        // mark the page table as present and allocate a physical block for it
+        boot_page_directory[PageDirectoryEntryIndex] = (uint32_t)(allocate_block() + 0x3);
+    }
+
+
+}
+
+void FreePage(uint32_t vaddr )
+{
+    uint32_t page_aligned_address = ALIGN(vaddr, 4096);
+
+    // allocate a page at  virtual address
+    int PageDirectoryEntryIndex = vaddr >> 22;
+    int PageTableEntryIndex = (vaddr >> 12) & 0x1FFF;
+
+    uint32_t* pageTable = (uint32_t*)(boot_page_directory[PageDirectoryEntryIndex] & 0xFFFFE000 + 0xC0000000);
+
+
+    void* physicalAddressToFree = (void*)(pageTable[PageTableEntryIndex] & 0xFFFFE000 + 0xC0000000);
+    free_block(physicalAddressToFree);
+
+    pageTable[PageTableEntryIndex] = 0x0;
+
+
+}
+
+void Map (  uint32_t vaddr, uint32_t paddr)
+{
+    uint32_t page_aligned_address = ALIGN(vaddr, 4096);
+
+    // allocate a page at  virtual address
+    int PageDirectoryEntryIndex = vaddr >> 22;
+    int PageTableEntryIndex = (vaddr >> 12) & 0x1FFF;
+}
+
+void Unmap(uint32_t vaddr)
+{
+    // NOTE: I will implement lazy unmapping for now 
+    uint32_t page_aligned_address = ALIGN(vaddr, 4096);
+
+    // allocate a page at  virtual address
+    int PageDirectoryEntryIndex = vaddr >> 22;
+    int PageTableEntryIndex = (vaddr >> 12) & 0x1FFF;
+}

source/kernel/memory/VirtualMemoryManager.h

@@ -1,6 +1,6 @@
 #pragma once 
 #include "PhysicalMemoryManager.h"
-#include "../Terminal/kterm.h"
+#include "../terminal/kterm.h"
 #include "../cpu.h"
 
 void AllocatePage(uint32_t v_addr );

source/kernel/memory/gdt/gdtc.cpp

@@ -1,5 +1,5 @@
 #include "gdtc.h"
-#include "../../Terminal/kterm.h"
+#include "../../terminal/kterm.h"
 
 #define NULL_SEGMENT          0
 #define KERNEL_CODE_SEGMENT   1

source/kernel/prekernel/prekernel.cpp

@@ -16,6 +16,7 @@ extern "C" void prekernelSetup  ( unsigned long magic, multiboot_info_t* mbi) {
   if (magic != MULTIBOOT_BOOTLOADER_MAGIC)
   {
         BIB->MapIsInvalid = true;
+        // crash
         return;
   } else{
         BIB->MapIsInvalid = false;

source/kernel/serial.h

@@ -1,6 +1,6 @@
 #pragma once
 
-#include "Terminal/kterm.h"
+#include "terminal/kterm.h"
 #include "io.h"
 #define PORT 0x3f8 
 static int init_serial() {

source/kernel/supervisorterminal/superVisorTerminal.h

@@ -0,0 +1,8 @@
+#pragma once 
+#include "../terminal/kterm.h"
+#include "../time.h"
+#include "../drivers/pit/pit.h"
+#include "../drivers/ps-2/keyboard.h"
+#include "../memory/PhysicalMemoryManager.h"
+
+void startSuperVisorTerminal();

source/kernel/terminal/kterm.h

@@ -3,11 +3,11 @@
 #include <stddef.h>
 #include <stdbool.h>
 
-#include "../Drivers/VGA/colors.h"
+#include "../drivers/vga/colors.h"
 #include "../io.h"
 
 extern "C"{
-    #include "../Lib/string.h"
+    #include "../lib/string.h"
 }
 
 void kterm_init();