help.. idt troubles

[batou]

Hi, this is a (slightly reduced) copy of my bootloader... after the sti... bochs fails with the error "3rd (13) exception with no handler". Any help or insight into my idt errors would be much appreciated. thankyou

;------------------------------------------------------------------
; COMPILE TIME DEFINITIONS & MACROS:
;------------------------------------------------------------------

%macro outb 2
   mov al, %2
   out %1, al
%endmacro   

;------------------------------------------------------------------
; CODE ENTRY POINT:
;------------------------------------------------------------------   

BITS 16
[org 1000h]               ;this was loaded from the bootsector !

Start:
      
      mov   ax, 9000h
      mov   ss, ax
      mov   sp, 0FFFFh      ;Set stack

      cli      
      call   enable_A20
      call   remap_PIC
      lgdt   [gdt_desc]
      mov    eax, cr0
      or    eax, 1
      mov    cr0, eax
      jmp    gdt_kernel_code : Protected_Mode_Start


;------------------------------------------------------------------
; BOOT LOADER 16 bit FUNCTIONS:
;------------------------------------------------------------------
enable_A20:
      cli
   .A20_1:               
      in   al, 64h
      test   al, 2
      jnz   .A20_1
      outb   64h, 0d1h
      
   .A20_2:
      in   al, 64h
      and   ax, byte 2
      jnz   .A20_2
      outb   60h, 0dfh
      
      ret

remap_PIC:
      cli

      in   al, 21h
      push   ax
      in   al, 0A1h
      push   ax
      
      outb   20h, 11h
      outb   0A0h, 11h
      outb   21h, 20h
      outb   0A1h, 28h
      outb   21h, 4
      outb   0A1h, 2
      outb   21h, 01h
      outb   0A1h, 01h
      
      pop   ax
      outb   0A1h, al
      pop   ax
      outb   21h, al
      
      ret


;------------------------------------------------------------------
; 32 BIT PROTECTED MODE START:
;------------------------------------------------------------------

[BITS 32]
Protected_Mode_Start:
      mov    ax, gdt_kernel_data
      mov    ds, ax
      mov    ss, ax
      mov    esp, 090000h
      mov   ax, gdt_video_memory
      mov   es, ax

      lidt   [idt_desc]
      sti

hang:
      jmp    hang


;------------------------------------------------------------------
; INTERRUPT HANDLERS:
;------------------------------------------------------------------

ISR:
      pusha
      push gs
      push fs
      push ds
      push es

      pop es
      pop ds
      pop fs
      pop gs
      popa
      iret

;-------------------------------------------------------------------------------------
; GENERAL DESCRIPTOR TABLE:
;-------------------------------------------------------------------------------------

gdt:
gdt_null:
   dd 0
   dd 0
gdt_kernel_code equ $-gdt
   dw 0FFFFh
   dw 0
   db 0
   db 10011010b
   db 11001111b
   db 0
gdt_kernel_data equ $-gdt
   dw 0FFFFh
   dw 0
   db 0
   db 10010010b
   db 11001111b
   db 0   
gdt_video_memory equ $-gdt
   dw 1000h
   dw 8000h
   db 0bh
   db 10010010b
   db 11001111b
   db 0
gdt_end:

gdt_desc:
   dw gdt_end - gdt - 1
   dd gdt

   
;-------------------------------------------------------------------------------------
; INTERRUPT DESCRIPTOR TABLE:
;-------------------------------------------------------------------------------------

idt:
%rep 256
dw ISR          
dw gdt_kernel_code    
db 0x00       
db 0x8E       
dw 0x0000       
%endrep
idt_end:

idt_desc:
   dw idt_end - idt - 1
   dd idt

[Pype.Clicker]

what is the CS value after the bootloader started your program ? if CS!=0, it means you cannot use the same in real and protected mode ...

[batou]

Okay, so then the offset of my IRS is wrong because nasm gives it the offset from real mode yet it should have the offset from the cs in protmode.... does that make sense? thanks for the help

[batou]

Hi all, I'm sorry for wasting space on this board.. I found my problem and it was quite a stupid one... I was not loading enough sectors off the disk and susequently not loading my idt correctly... so embarrassed.