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MBOOT_PAGE_ALIGN    equ 1<<0 
MBOOT_MEM_INFO      equ 1<<1
MBOOT_VIDINFO equ  1 << 2       ;;; DOESN'T WORK IN QEMU
MBOOT_HEADER_MAGIC  equ 0x1BADB002 ; Multiboot Magic value
MBOOT_HEADER_FLAGS  equ MBOOT_PAGE_ALIGN | MBOOT_MEM_INFO
MBOOT_CHECKSUM      equ -(MBOOT_HEADER_MAGIC + MBOOT_HEADER_FLAGS)


[BITS 32]

[GLOBAL mboot] 
[EXTERN code]                   ; Start of the '.text' section.
[EXTERN bss]                    ; Start of the .bss section.
[EXTERN end]                    ; End of the last loadable section.

mboot:
    dd  MBOOT_HEADER_MAGIC 
    dd  MBOOT_HEADER_FLAGS 
    dd  MBOOT_CHECKSUM
    
    dd  mboot                   ; Location of this descriptor
    dd  code                    ; Start of kernel '.text' (code) section.
    dd  bss                     ; End of kernel '.data' section.
    dd  end                     ; End of kernel.
    dd  start                   ; Kernel entry point (initial EIP).
;       dd 0 ; # 0 = set graphics mode
;	dd 1024
;	dd 768
;	dd 32
;    ^ ^ ^ Don't work in Qemu

[GLOBAL start]                  ; Kernel entry point.
[EXTERN main]                   ; This is the entry point of our C code

start:

	mov eax, cr0
	and eax,-0x2
	mov cr0,eax ; disable PM

	[bits 16]

       ;; Interrupts already enabled by grub?

	mov ah,0
	mov al,4 ; 320x200x(4 color)
	int 0x10  ; gets crashed

	[bits 32]
   ; push esp - stack ptr
   ; push ebx - mboot ptr



    ; Execute the kernel:
   ; cli                       
   ; call main ; not yet, still in 16 bit real mode
    jmp $

Code: Select all

MBOOT_PAGE_ALIGN    equ 1<<0 
MBOOT_MEM_INFO      equ 1<<1
MBOOT_VIDINFO equ  1 << 2       ;;; DOESN'T WORK IN QEMU
MBOOT_HEADER_MAGIC  equ 0x1BADB002 ; Multiboot Magic value
MBOOT_HEADER_FLAGS  equ MBOOT_PAGE_ALIGN | MBOOT_MEM_INFO
MBOOT_CHECKSUM      equ -(MBOOT_HEADER_MAGIC + MBOOT_HEADER_FLAGS)


[BITS 32]

[GLOBAL mboot] 
[EXTERN code]                   ; Start of the '.text' section.
[EXTERN bss]                    ; Start of the .bss section.
[EXTERN end]                    ; End of the last loadable section.

mboot:
    dd  MBOOT_HEADER_MAGIC 
    dd  MBOOT_HEADER_FLAGS 
    dd  MBOOT_CHECKSUM
    
    dd  mboot                   ; Location of this descriptor
    dd  code                    ; Start of kernel '.text' (code) section.
    dd  bss                     ; End of kernel '.data' section.
    dd  end                     ; End of kernel.
    dd  start                   ; Kernel entry point (initial EIP).

[GLOBAL start]                  ; Kernel entry point.
[EXTERN main]                   ; This is the entry point of our C code

start:
   cli
   sgdt [OLDGDT]
   sidt [OLDIDT]
   
   lgdt [gdtinfo]
   lidt [idt_real]

   mov eax, cr0
   mov DWORD [OLDCR0], eax
   mov eax, cr3
   mov DWORD [OLDCR3], eax

   jmp 0x08:.protected16bit
[bits 16]
   .protected16bit:
      mov ax, 0x10
      mov ds, ax
      mov es, ax
      mov eax, cr0
      and eax, 0x7FFFFFFE
      mov cr0, eax
      jmp 0:.realmode ; Or Whatever Segment You Need

  .realmode:
    mov ax, 0 ; Or Whatever Segment You Need
    mov ds, ax
    mov es, ax

    ;Setup stack
    mov ss, ax
    mov sp, 0xFFF0

   ; sti ; If you need maskable ints uncomment this

   mov ah,0
   mov al,4 ; 320x200x(4 color)
   int 0x10

   cli
   mov eax, DWORD [OLDCR3]
   mov cr3, eax
   mov eax, DWORD [OLDCR0]
   mov cr0, eax

   ; lgdt [OLDGDT] ; If you changed your GDT reload the old one.

   jmp 18h:.protectedmode
[bits 32]
    .protectedmode:
      mov ax, 0x10
      mov dx, ax
      mov es, ax
      mov ss, ax
      mov sp, [KERNEL_STACK]
      lidt [OLDIDT]
      call main
      .halt:
        hlt
        jmp .halt


;----------------------------------------------------
;                        GDT
;----------------------------------------------------
gdtinfo:
   dw (gdt_end - gdt - 1)   ;last byte in table
   dd (gdt)                ;start of table

gdt         dd 0,0        ; entry 0 is always unused
flatcode    db 0xFF, 0xFF, 0, 0, 0, 10011010b, 10001111b, 0 ; 16-bit code
flatdata    db 0xFF, 0xFF, 0, 0, 0, 10010010b, 11001111b, 0 ; 32-bit data
pmflatcode  db 0xFF, 0xFF, 0, 0, 0, 10011010b, 11001111b, 0 ; 32-bit code
gdt_end:

OLDGDT dd 0
OLDIDT dd 0
OLDCR0 dd 0
OLDCR3 dd 0

idt_real:
  dw 0x3ff    ; 256 entries, 4b each = 1K
  dd 0      ; Real Mode IVT @ 0x0000