@@ -73,6 +73,7 @@ mov %eax, %ds
   mov %eax, %es
   mov %eax, %fs
   mov %eax, %gs
+  mov %eax, %ss
 
   # jump to second stage code
   ljmp $0x08, $_ss_start
@@ -112,8 +113,3 @@
 IDT_DESCRIPTOR:
   .word 0
   .int 0
-
-end:
-  .=510
-  .byte 0x55
-  .byte 0xAA

@@ -0,0 +1,20 @@
+.global _kernel_start
+_kernel_start:
+  # this code prints out all ascii characters in reverse order in
+  # rainbow colors just to test if this point of the code was reached
+  # (you might call it overkill, i call it fabulous)
+  mov $255, %ecx
+  mov $0xB8000, %esi
+
+test:
+  movb %cl, (%esi)
+  inc %esi
+  movb %cl, (%esi)
+  inc %esi
+  loop test
+
+  # loop until the heat death of the universe
+loop:
+  jmp loop
+
+  .ascii "hey now youre an allstar get your game on"

@@ -0,0 +1,17 @@
+INPUT(build/entry.o)
+OUTPUT_FORMAT(elf32-i386)
+OUTPUT_ARCH(i386)
+ENTRY(_kernel_start)
+
+SECTIONS
+{
+  .text : 
+  {
+      *.*(.text)
+  }
+
+  .data :
+  {
+      *.*(.data)
+  }
+}

@@ -0,0 +1,17 @@
+.RECIPEPREFIX = >
+
+.PHONY: build
+build: build/entry.o
+> $(GCC_PREFIX)ld -r -T link.txt -o $(BUILD_DIR)/kernel.o --oformat elf32-i386
+
+.PHONY: clear
+clear:
+> @rm build/*.* 2> /dev/null; true
+
+.PHONY: rebuild
+rebuild:
+> $(MAKE) clear
+> $(MAKE) build
+
+build/entry.o: entry.s
+> $(GCC_PREFIX)as -o $@ $<

@@ -9,6 +9,7 @@ {
   BOOT :          ORIGIN = 0x00007C00, LENGTH = 0x00000200
   SECOND_STAGE :  ORIGIN = 0x00010000, LENGTH = 0x00090000
   KERNEL :        ORIGIN = 0xC0000000, LENGTH = 0x30000000
+  APPLICATION :   ORIGIN = 0x10000000, LENGTH = 0xB0000000
 }
 
 SECTIONS
@@ -16,6 +17,9 @@ {
   BOOT : AT(0x0000)
   {
     build/boot.o(.*)
+    . = 510;
+    BYTE(0x55)
+    BYTE(0xAA)
   } >BOOT
 
   SECOND_STAGE : AT(LOADADDR(BOOT) + SIZEOF(BOOT))
@@ -24,9 +28,14 @@ build/second_stage.o(.*)
   } >SECOND_STAGE
 
   KERNEL : AT(LOADADDR(SECOND_STAGE) + SIZEOF(SECOND_STAGE))
+  {
+    build/kernel.o(.*)
+  } >KERNEL
+
+  APPLICATION : AT(LOADADDR(KERNEL) + SIZEOF(KERNEL))
   {
 
-  } >KERNEL
+  } >APPLICATION
 }
 
 __SS_LMA = LOADADDR(SECOND_STAGE);
@@ -36,3 +45,9 @@
 __KERNEL_LMA = LOADADDR(KERNEL);
 __KERNEL_VMA = ADDR(KERNEL);
 __KERNEL_SIZE = SIZEOF(KERNEL);
+
+__APP_LMA = LOADADDR(APPLICATION);
+__APP_VMA = ADDR(APPLICATION);
+__APP_SIZE = SIZEOF(APPLICATION);
+
+ASSERT(__SS_SIZE + __KERNEL_SIZE + __APP_SIZE <= 0x48 * 0x200, "bootloader payload too big!");

@@ -14,6 +14,7 @@ .PHONY: build
 build:
 > $(MAKE) -C boot build
 > $(MAKE) -C second_stage build
+> $(MAKE) -C kernel build
 > $(GCC_PREFIX)ld -T link.txt -Map=$(DEBUG_DIR)/mapfile.txt -o $(BUILD_DIR)/base.img --oformat binary
 
 .PHONY: clear
@@ -21,6 +22,7 @@ clear:
 > @rm $(BUILD_DIR)/*.* 2> /dev/null; true
 > @$(MAKE) -C boot clear 2> /dev/null; true
 > @$(MAKE) -C second_stage clear 2> /dev/null; true
+> @$(MAKE) -C kernel clear 2> /dev/null; true
 
 .PHONY: run
 run:
@@ -30,3 +32,7 @@ .PHONY: rebuild
 rebuild:
 > $(MAKE) clear
 > $(MAKE) build
+
+.PHONY: objdump
+objdump:
+> $(GCC_PREFIX)objdump -D $(FILE) > debug/objdump.txt

@@ -1,1 +1,1 @@
-qemu -L .\ -fda build/base.img -m 64 -monitor stdio -no-reboot -d int,cpu_reset+qemu -L .\ -fda build/base.img -m 64 -monitor stdio -no-reboot -d int,cpu_reset 2> debug/err.log

@@ -1,34 +1,29 @@
 .section .text
 .global _ss_start
 _ss_start:
+  # copy the kernel code to 0x00100000
+  call copy_kernel
 
-  # this code prints out all ascii characters in reverse order in
-  # rainbow colors just to test if this point of the code was reached
-  # (you might call it overkill, i call it fabulous)
-  mov $255, %ecx
-  mov $0xB8000, %esi
+  # create a page directory for the kernel that maps it to 0xC0000000
+  # and identity maps the first 1M of memory
+  call create_kernel_environment
+  
+  # load kernel page directory
+  movl %eax, %cr3
 
-test:
-  movb %cl, (%esi)
-  inc %esi
-  movb %cl, (%esi)
-  inc %esi
-  loop test
-
+  # set paging enable and protection bit
+  movl %cr0, %eax
+  or $0x80000010, %eax
+  movl %eax, %cr0
 
   # TODO:
-  #  - copy the kernel code to 0x00100000
-  call copy_kernel
-
-  #  - create a page directory for the kernel that maps it to 0xC0000000
-  #    and identity maps the first 1M of memory
-  #  - enable paging
-  #  - jump to kernel code
-
+  # jump to kernel code
+  ljmp $8, $__KERNEL_VMA
 
   # loop until the heat death of the universe
 loop:
   jmp loop
+  
 
 .section .data
 low_kernel_welcome:

@@ -8,16 +8,22 @@ (uint8_t)(base >> 8), \
         (uint8_t)(base >> 16), \
         (uint8_t)(access), \
         (uint8_t)(((limit >> 16) & 0x0F) | ((flags << 4) & 0xF0)), \
-        (uint8_t)(base >> 24), \
+        (uint8_t)(base >> 24) \
     }
 
-GDT_ENTRY GDT[3] = {
+GDT_ENTRY GDT[5] = {
     // null descriptor
     GDT_MAKE_ENTRY(0x00000000, 0x00000000, 0x00, 0x0),
 
-    // identity mapping (code)
+    // identity mapping (code, ring 0)
     GDT_MAKE_ENTRY(0x00000000, 0x000FFFFF, 0x9A, 0xC),
 
-    // identity mapping (data)
-    GDT_MAKE_ENTRY(0x00000000, 0x000FFFFF, 0x92, 0xC)
+    // identity mapping (data, ring 0)
+    GDT_MAKE_ENTRY(0x00000000, 0x000FFFFF, 0x92, 0xC),
+
+    // identity mapping (code, ring 3)
+    GDT_MAKE_ENTRY(0x00000000, 0x000FFFFF, 0xFA, 0xC),
+
+    // identity mapping (data, ring 3)
+    GDT_MAKE_ENTRY(0x00000000, 0x000FFFFF, 0xF2, 0xC)
 };

@@ -14,7 +14,7 @@ uint8_t limit_and_flags;
     uint8_t base_24;
 } __attribute__((packed)) GDT_ENTRY;
 
-GDT_ENTRY GDT[3];
+GDT_ENTRY GDT[5];
 
 /*struct {
     uint32_t gdt_offset;

@@ -1,4 +1,4 @@
-INPUT(build/entry.o build/gdt.o build/main.o)
+INPUT(build/entry.o build/gdt.o build/main.o build/paging.o)
 OUTPUT_FORMAT(elf32-i386)
 OUTPUT_ARCH(i386)
 ENTRY(_ss_start)
@@ -7,15 +7,11 @@ SECTIONS
 {
   .text : 
   {
-      build/entry.o(.text)
-      build/gdt.o(.text)
-      build/main.o(.text)
+      *.*(.text)
   }
 
   .data :
   {
-      build/entry.o(.data)
-      build/gdt.o(.data)
-      build/main.o(.data)
+      *.*(.data)
   }
 }

@@ -1,20 +1,37 @@
 #include "linker.h"
+#include "paging.h"
+
+#define VGA_TEXTMODE_COLUMNS 80
+#define VGA_TEXTMODE_LINES 25
+#define VGA_TEXTMODE_CELLS (VGA_TEXTMODE_COLUMNS * VGA_TEXTMODE_LINES)
+
+#define VGA_TEXT_COLOR 0x02
 
+const uint8_t const *display_start = (uint8_t*)0xB8000;
 uint8_t *display = (uint8_t*)0xB8000;
 
 void simple_clear(void) {
-    display = (uint8_t*)0xB8000;
+    display = (uint8_t*)display_start;
 
-    for (int i = 0; i < 80 * 25; i++) {
+    for (int i = 0; i < VGA_TEXTMODE_CELLS; i++) {
         display[2 * i] = 0x00;
         display[2 * i + 1] = 0x00;
     }
 }
 
-void simple_print(const char* src) {
+void simple_print(const char *src) {
     while (*src) {
         *display++ = *src++;
-        *display++ = 0x02;
+        *display++ = VGA_TEXT_COLOR;
+    }
+}
+
+void simple_println(const char *src) {
+    simple_print(src);
+
+    while ((display - display_start) % (2 * VGA_TEXTMODE_COLUMNS)) {
+        display++;
+        display++;
     }
 }
 
@@ -29,5 +46,5 @@ for (uint32_t i = 0; i < KERNEL_SIZE; i++) {
         kernel_dest[i] = kernel_src[i];
     }
 
-    simple_print("DONE.");
+    simple_println("DONE.");
 }

@@ -1,7 +1,7 @@
 .RECIPEPREFIX = >
 
 .PHONY: build
-build: build/entry.o build/gdt.o build/main.o
+build: build/entry.o build/gdt.o build/main.o build/paging.o
 > $(GCC_PREFIX)ld -r -T link.txt -o $(BUILD_DIR)/second_stage.o --oformat elf32-i386
 
 .PHONY: clear
@@ -20,4 +20,7 @@ build/gdt.o: gdt.c gdt.h
 > $(GCC_PREFIX)gcc -c -I$(INCLUDE_DIR) --prefix=$(GCC_PREFIX) $(GCC_OPTIONS) -o $@ $<
 
 build/main.o: main.c
-> $(GCC_PREFIX)gcc -c -I$(INCLUDE_DIR) --prefix=$(GCC_PREFIX) $(GCC_OPTIONS) -o $@ $<+> $(GCC_PREFIX)gcc -c -I$(INCLUDE_DIR) --prefix=$(GCC_PREFIX) $(GCC_OPTIONS) -o $@ $<
+
+build/paging.o: paging.c paging.h
+> $(GCC_PREFIX)gcc -c -I$(INCLUDE_DIR) --prefix=$(GCC_PREFIX) $(GCC_OPTIONS) -o $@ $<

@@ -0,0 +1,38 @@
+#include "paging.h"
+#include "linker.h"
+
+void *ss_memset(void *ptr, uint8_t value, uint32_t num) {
+    for (uint32_t i = 0; i < num; i++) {
+        ((uint8_t*)ptr)[i] = value;
+    }
+    return ptr;
+}
+
+void *create_kernel_environment() {
+    PAGE_DIR_ENTRY (*pdir)[PAGE_ENTRY_COUNT] = (void*)(0 * PAGE_SIZE);
+    PAGE_TABLE_ENTRY (*kernel)[PAGE_ENTRY_COUNT] = (void*)(1 * PAGE_SIZE);
+    PAGE_TABLE_ENTRY (*lowmem)[PAGE_ENTRY_COUNT] = (void*)(2 * PAGE_SIZE);
+
+    // set everything to zero
+    ss_memset(pdir, 0, 3 * PAGE_SIZE);
+
+    // map page directory to itself
+    //(*pdir)[PAGE_DIR_INDEX(0)].entry = MAKE_PAGE_ENTRY(pdir, 0b000000000011);
+
+    // map kernel to 0xC0000000
+    (*pdir)[PAGE_DIR_INDEX(KERNEL_VMA)].entry = MAKE_PAGE_ENTRY(kernel, 0b000000000011);
+
+
+    for (uint32_t i = 0; i < 1 << 8; i++) {
+        (*kernel)[i].entry = MAKE_PAGE_ENTRY(KERNEL_LMA + PAGE_SIZE * i, 0b000000000011);
+    }
+
+    // identity map first 4M of memory
+    (*pdir)[PAGE_DIR_INDEX(0)].entry = MAKE_PAGE_ENTRY(lowmem, 0b000000000011);
+
+    for (uint32_t i = 0; i < 1 << 10; i++) {
+        (*lowmem)[i].entry = MAKE_PAGE_ENTRY(PAGE_SIZE * i, 0b000000000011);
+    }
+
+    return pdir;
+}

@@ -0,0 +1,53 @@
+#ifndef PAGING_H
+#define PAGING_H
+
+#include <stdint.h>
+
+#define PAGE_ENTRY_COUNT (1 << 10)
+#define PAGE_SIZE (1 << 12)
+
+typedef union {
+    uint32_t entry;
+    struct
+    {
+        uint32_t present : 1;
+        uint32_t read_write : 1;
+        uint32_t user_supervisor : 1;
+        uint32_t write_through : 1;
+        uint32_t cache_disabled : 1;
+        uint32_t accessed : 1;
+        uint32_t __zero : 1;
+        uint32_t page_size : 1;
+        uint32_t __ignored : 1;
+        uint32_t available : 3;
+        uint32_t page_table_addr : 20;
+    } __attribute((packed)) fields;
+} PAGE_DIR_ENTRY;
+
+typedef union {
+    uint32_t entry;
+    uint8_t bytes[4];
+    struct {
+        uint32_t present : 1;
+        uint32_t read_write : 1;
+        uint32_t user_supervisor : 1;
+        uint32_t write_through : 1;
+        uint32_t cache_disabled : 1;
+        uint32_t accessed : 1;
+        uint32_t dirty : 1;
+        uint32_t __zero : 1;
+        uint32_t global : 1;
+        uint32_t available : 3;
+        uint32_t page_addr : 20;
+    } __attribute((packed)) fields;
+} PAGE_TABLE_ENTRY;
+
+#define MAKE_PAGE_ENTRY(addr, flags) (uint32_t)(((uint32_t)(addr) & 0xFFFFF000) | (flags))
+
+#define PAGE_DIRECTORY (PAGE_DIR_ENTRY[PAGE_ENTRY_COUNT])
+#define PAGE_TABLE (PAGE_TABLE_ENTRY[PAGE_ENTRY_COUNT])
+
+#define PAGE_DIR_INDEX(addr) ((uint32_t)(addr) >> 22)
+#define PAGE_TABLE_INDEX(addr) ((uint32_t)(addr) >> 12)
+
+#endif