...

src/boot.asm

@@ -1,6 +1,32 @@
 [org 0x7c00]
 [bits 16]
 
+KERNEL_LOCATION equ 0x1000
+
+mov [BOOT_DISK], dl                 
+
+xor ax, ax                          
+mov es, ax
+mov ds, ax
+mov bp, 0x8000
+mov sp, bp
+
+mov bx, KERNEL_LOCATION
+mov dh, 2
+
+mov ah, 0x02
+mov al, dh 
+mov ch, 0x00
+mov dh, 0x00
+mov cl, 0x02
+mov dl, [BOOT_DISK]
+int 0x13
+
+                                    
+mov ah, 0x0
+mov al, 0x3
+int 0x10
+
 CODE_SEG equ gdt_code - gdt_start
 
 cli
@@ -40,6 +66,17 @@ gdt_descriptor:
 
 [bits 32]
 start_protected_mode:
+    mov ax, DATA_SEG
+	mov ds, ax
+	mov ss, ax
+	mov es, ax
+	mov fs, ax
+	mov gs, ax
+	
+	mov ebp, 0x90000
+	mov esp, ebp
+
+    jmp KERNEL_LOCATION
     jmp $
 
 

src/kernel.c

@@ -0,0 +1,5 @@
+int main(void)
+{
+    *(char*)0xb8000 = 'A';
+    return 0;
+}

src/kernel_entry.asm

@@ -0,0 +1,5 @@
+section .text
+    [bits 32]
+    [extern main]
+    call main
+    jmp $