The kernel is now actually useable with paging enabled.

Makefile

@@ -2,7 +2,7 @@ CFLAGS = -m32 -mgeneral-regs-only -nostdlib -fno-builtin -fno-exceptions -fno-le
 LDFLAGS = 
 
 DISK_IMG_FILES = build/kernel/kernel.bin
-KERNEL_OBJS = build/c_code_entry.o build/kernel/screenstuff.o build/kernel/io.o build/kernel/idt.o build/kernel/keyboard.o build/kernel/strings.o build/kernel/atapio.o build/kernel/kernel.o build/kernel/paging.o
+KERNEL_OBJS = build/c_code_entry.o build/kernel/screenstuff.o build/kernel/io.o build/kernel/idt.o build/kernel/keyboard.o build/kernel/strings.o build/kernel/atapio.o build/kernel/kernel.o build/kernel/paging.o build/kernel/allocate.o
 STAGE2_OBS = build/c_code_entry.o build/boot_stage2/io.o build/boot_stage2/atapio.o build/boot_stage2/strings.o build/boot_stage2/screenstuff.o build/boot_stage2/stage2.o build/boot_stage2/paging.o
 
 run: disk.img
@@ -23,6 +23,7 @@ prepare:
 	mkdir -p build/boot
 	mkdir -p build/boot_stage2
 	mkdir -p build/kernel
+	mountpoint img.d | grep not || umount img.d
 
 clean:
 	rm -rf build

src/boot_stage2/main.c

@@ -119,9 +119,13 @@ void main() {
   map_4k_phys_to_virt((uint32_t)kernel_page_directory, 0xc0100000, kernel_page_directory, kernel_page_tables); // Map the page directory to 0xc0100000
   map_many_4k_phys_to_virt(0x121000, 0xc0101000, kernel_page_directory, kernel_page_tables, 1024); // Map 1024 pages from 0x121000 to 0xc0101000
   map_4k_phys_to_virt(0xb8000, 0xc0501000, kernel_page_directory, kernel_page_tables); // Map 0xb8000 (video) to 0xc0501000
+  map_4k_phys_to_virt(0x521000, 0xc0502000, kernel_page_directory, kernel_page_tables); // Map the PTE** data, we'll need to convert the pointers to point at kernel space at some point.
+
+  // Map the bitmap 
+  map_many_4k_phys_to_virt(0x100000, 0xc0600000, kernel_page_directory, kernel_page_tables, 32);
 
   map_many_4k_phys_to_virt(0x7000, 0x7000, kernel_page_directory, kernel_page_tables, 2);
-  map_4k_phys_to_virt(0x8f000, 0x8f000, kernel_page_directory, kernel_page_tables);
+  map_many_4k_phys_to_virt(0x8a000, 0x8a000, kernel_page_directory, kernel_page_tables, 6);
 
   load_file("KERNEL  BIN", kernel_location);
 

src/kernel/allocate.c

@@ -0,0 +1,72 @@
+#include "allocate.h"
+
+uint8_t* bitmap = 0xc0600000;
+PDE* kernel_page_directory = 0xc0100000;
+PTE** kernel_page_tables = 0xc0502000;
+
+uint32_t kernel_allocate_area = 0xf0000000;
+
+uint32_t last_free_page = 0;
+
+/*void init_allocator() {
+  for (int i=0; i<1024; i++) {
+    kernel_page_tables[i] = 0xc0101000 + 0x1000*i;
+  }
+}*/ // Don't do this.
+
+void set_bit(uint32_t offset, uint8_t* buffer) {
+  uint32_t index = offset / 8;
+  uint32_t bit = offset % 8;
+
+  buffer[index] |= (1<<(7 - bit));
+}
+
+uint8_t get_bit(uint32_t offset, uint8_t* buffer) {
+  uint32_t index = offset / 8;
+  uint32_t bit = offset % 8;
+
+  return buffer[index] & (1<<(7 - bit));
+}
+
+void unset_bit(uint32_t offset, uint8_t* buffer) {
+  uint32_t index = offset / 8;
+  uint32_t bit = offset % 8;
+
+  buffer[index] &= (255 - (1<<(7 - bit)));
+}
+
+void mark_unavailble(uint32_t address, uint32_t size) {
+  // This function takes a physical address and length and marks the corresponding pages as unavailable.
+  address -= address % 4096; 
+  if (size % 4096)
+    size += 4096 - (size % 4096);
+
+  address /= 4096;
+  size /= 4096;
+
+  for (int i=0; i<size; i++) {
+    unset_bit(address + i, bitmap);
+  }
+}
+
+void* dumb_alloc(uint32_t size) {
+  if (size % 4096)
+    size += 4096 - (size % 4096); // Since this is dumb alloc just make the amount we're allocating be in whole page sizes
+
+  uint32_t ptr = kernel_allocate_area;
+
+  while (size > 0) {
+    for (; get_bit(last_free_page, bitmap) == 0; last_free_page++);
+    printf("Free page: %d\n", last_free_page);
+
+    uint32_t phys_addr = last_free_page * 4096;
+
+    mark_unavailble(phys_addr, 4096);
+    map_4k_phys_to_virt(phys_addr, kernel_allocate_area, kernel_page_directory, kernel_page_tables);
+
+    kernel_allocate_area += 4096;
+    size -= 4096;
+  }
+
+  return (void*)ptr;
+}

src/kernel/allocate.h

@@ -0,0 +1,15 @@
+#ifndef ALLOCATE_H
+#define ALLOCATE_H
+
+#include "paging.h"
+//void init_allocator();
+
+void set_bit(uint32_t offset, uint8_t* buffer);
+void unset_bit(uint32_t offset, uint8_t* buffer);
+uint8_t get_bit(uint32_t offset, uint8_t* buffer);
+
+void mark_unavailble(uint32_t address, uint32_t size);
+
+void* dumb_alloc(uint32_t size);
+
+#endif 

src/kernel/atapio.c

@@ -11,8 +11,8 @@
 uint16_t identify_result[256];
 uint32_t total_28_lbas = 0;
 
-uint8_t* rootDirEntries = 0x1000000;
-uint16_t* FAT1 = 0x1002000;
+uint8_t* rootDirEntries;
+uint16_t* FAT1;
 
 uint16_t countReserved;
 uint8_t countFATs;
@@ -21,6 +21,10 @@ uint16_t sectorsPerFAT;
 
 
 void init_atapio() {
+  rootDirEntries = (uint8_t*)dumb_alloc(8192);
+  FAT1 = (uint16_t*)dumb_alloc(512 * 34);
+  printf("RDE: %x\nFAT1: %x\n", rootDirEntries, FAT1);
+
   countReserved = *(uint16_t*)0x7c0e;
   countFATs = *(uint8_t*)0x7c10;
   countRDEs = *(uint16_t*)0x7c11;

src/kernel/atapio.h

@@ -6,6 +6,7 @@
 #include "io.h"
 #include "types.h"
 #include "strings.h"
+#include "allocate.h"
 
 void init_atapio();
 void read_sector(uint32_t address, uint8_t* buffer);

src/kernel/kernel.c

@@ -7,19 +7,21 @@
 #include "atapio.h"
 
 int main() {
-  while (1);
   init_idt();
   init_term();
+//  init_allocator();
 
+  printf("Hello, World!\n\nWe are running XnoeOS Code in C now, Protected Mode has been achieved (as well as Virtual Memory / Paging!!!) and everything is working super nicely!\n\nHow wonderful!\n\nNow I just need to hope my print function works properly too~~\n");
+  
   printf("KERNEL OK!\n");
 
-  printf("Hello, World!\n\nWe are running XnoeOS Code in C now, Protected Mode has been achieved and everything is working super nicely!\n\nHow wonderful!\n\nNow I just need to hope my print function works properly too~~\n");
-  
   init_keyboard();
   
   enable_idt();
   init_atapio();
 
+  //while (1);
+
   uint8_t sector[512];
 
   read_sector(0, sector);

src/kernel/paging.c

@@ -24,7 +24,7 @@ void map_4k_phys_to_virt(uint32_t physical, uint32_t virtual, PDE* page_director
     .ignored2 = 0
   };
 
-  page_tables[split->pd_index][split->pt_index] = (PTE){
+  ((PTE*)((uint32_t)page_tables[split->pd_index] + 0xbffe0000))[split->pt_index] = (PTE){
     .address = physical >> 12,
     .available = 0,
     .global = 0,

src/kernel/screenstuff.c

@@ -1,6 +1,6 @@
 #include "screenstuff.h"
 
-uint16_t* VMEM_ADDR = (uint16_t*)0xb8000;
+uint16_t* VMEM_ADDR = (uint16_t*)0xc0501000;
 const int TERM_WIDTH = 80;
 const int TERM_HEIGHT = 25;