; Declare constants for the multiboot header.
MBALIGN  equ  1 << 0            ; align loaded modules on page boundaries
MEMINFO  equ  1 << 1            ; provide memory map
FLAGS    equ  MBALIGN | MEMINFO ; this is the Multiboot 'flag' field
MAGIC    equ  0x1BADB002        ; 'magic number' lets bootloader find the header
CHECKSUM equ -(MAGIC + FLAGS)   ; checksum of above, to prove we are multiboot
 
section .multiboot
align 4
	dd MAGIC
	dd FLAGS
	dd CHECKSUM
 
section .bss
align 16
stack_bottom:
resb 16384 ; 16 KiB
stack_top:
 
section .text

global reloadSegments ; Flush GDT
reloadSegments:
   JMP   0x08:reload_CS ; 0x08 points at the new code selector
reload_CS:
   MOV   AX, 0x10 ; 0x10 points at the new data selector
   MOV   DS, AX
   MOV   ES, AX
   MOV   FS, AX
   MOV   GS, AX
   MOV   SS, AX
   RET

%macro ISR_NOERRCODE 1  ; define a macro, taking one parameter
  [GLOBAL isr%1]        ; %1 accesses the first parameter.
  isr%1:
    cli
    push byte %1
    push byte %1
    jmp isr_common_stub
%endmacro

%macro ISR_ERRCODE 1
  [GLOBAL isr%1]
  isr%1:
    cli
    push byte %1
    jmp isr_common_stub
%endmacro 

ISR_NOERRCODE 0
ISR_NOERRCODE 1
ISR_NOERRCODE 2
ISR_NOERRCODE 3
ISR_NOERRCODE 4
ISR_NOERRCODE 5
ISR_NOERRCODE 6
ISR_NOERRCODE 7
ISR_NOERRCODE 8
ISR_NOERRCODE 9
ISR_NOERRCODE 10
ISR_NOERRCODE 11
ISR_NOERRCODE 12
ISR_NOERRCODE 13
ISR_NOERRCODE 14
ISR_NOERRCODE 15
ISR_NOERRCODE 16
ISR_NOERRCODE 17
ISR_NOERRCODE 18
ISR_NOERRCODE 19
ISR_NOERRCODE 20
ISR_NOERRCODE 21
ISR_NOERRCODE 22
ISR_NOERRCODE 23
ISR_NOERRCODE 24
ISR_NOERRCODE 25
ISR_NOERRCODE 26
ISR_NOERRCODE 27
ISR_NOERRCODE 28
ISR_NOERRCODE 29
ISR_NOERRCODE 30
ISR_NOERRCODE 31

[EXTERN isr_handler]

isr_common_stub:
   pusha                    ; Pushes edi,esi,ebp,esp,ebx,edx,ecx,eax

   mov ax, ds               ; Lower 16-bits of eax = ds.
   push eax                 ; save the data segment descriptor

   mov ax, 0x10  ; load the kernel data segment descriptor
   mov ds, ax
   mov es, ax
   mov fs, ax
   mov gs, ax

   call isr_handler

   pop eax        ; reload the original data segment descriptor
   mov ds, ax
   mov es, ax
   mov fs, ax
   mov gs, ax

   popa                     ; Pops edi,esi,ebp...
   add esp, 8     ; Cleans up the pushed error code and pushed ISR number
   sti
   iret           ; pops 5 things at once: CS, EIP, EFLAGS, SS, and ESP


global _start:function (_start.end - _start)
_start:
	mov esp, stack_top
   	extern kernel_main
	call kernel_main
	cli

.hang:	hlt
	jmp .hang
.end: