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Index > OS Construction > why this code can run win2k8/win7, but not Winxp

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pyq881120



Joined: 23 Nov 2011
Posts: 1
pyq881120
Hi everyone

I'm copy the MBR to Second sector, then build below code to bin, cover First sector, remain origin MBR Partition table info. this can normal boot win2k8/win7,but not Winxp。

Code:
  org 0h
start:

    xor    ax, ax
       mov    ds, ax
       mov    si, 7C00h
    mov    ax, 0600h
    mov    es, ax
       xor    di, di
       push   100h
 pop    cx

       rep    movsw

    mov eax, [ds:4Ch] ; 
    mov dword [es:int_13h], eax 
    mov word [ds:4Ch], int13_hook 
  mov word [ds:4Eh], es
   pop ds 

 sti
 
    push   es
   mov    ax,next
      push   ax
   retf
next:
   push    dx
  mov     dx, 0
       mov     es, dx
      pop     dx
  mov     cx, 2
       mov     ax, 201h                ; sector 1
  mov     dl, 80h
     mov     bx, 7c00h
   int     13h
 jmp word 0x0000:0x07c00

int13_hook:

       db 0xea
int_13h: dw 0 ; offset
dw  0 ; segment    


[Edit By Loco] Added code tags and moved to OS Construction by public demand (although I don't fully agree with the last action)
Post 29 Nov 2011, 08:33
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typedef



Joined: 25 Jul 2010
Posts: 2913
Location: 0x77760000
typedef
Are you trying to run it in pMode ? By the way, I think you posted in a wrong section.
Post 29 Nov 2011, 11:00
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f0dder



Joined: 19 Feb 2004
Posts: 3170
Location: Denmark
f0dder
typedef wrote:
Are you trying to run it in pMode ? By the way, I think you posted in a wrong section.
Looks more like bootloader code, trying to chain to previous bootloader code.

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Post 29 Nov 2011, 16:09
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typedef



Joined: 25 Jul 2010
Posts: 2913
Location: 0x77760000
typedef
f0dder wrote:
typedef wrote:
Are you trying to run it in pMode ? By the way, I think you posted in a wrong section.
Looks more like bootloader code, trying to chain to previous bootloader code.


oh yeah. I see the org.

But yeah, wrong section I think
Post 29 Nov 2011, 16:32
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shutdownall



Joined: 02 Apr 2010
Posts: 518
Location: Munich
shutdownall
pyq881120 wrote:
Hi everyone

I'm copy the MBR to Second sector, then build below code to bin, cover First sector, remain origin MBR Partition table info. this can normal boot win2k8/win7,but not Winxp


Are you sure, you let run the same code on all systems ?
Do you test with different PC's or do you have all 3 operating systems on the same PC with partitions ?

The code looks like it's not working at all, when compiling there is an error shown at "jmp word 0x0000:0x07c00". I think the size of int13hook is too small. And you do a POP DS without pushing something.

Did you write the code yourself ? Looks like copied from different sources. Rolling Eyes

Why do you jump after loading the code and why do a retf with the stack ?
By the way, you don't init the stack (SS / SP) which is not a good programming style and can cause side effects.

And what do you want to do ? I think INT13 from BIOS is used for bootloader only. Operating system will use ATAPI interface with in/out or memory mapped i/o and not use BIOS interrupt.

Just my thoughts before spending too much time in a project ...
Post 29 Nov 2011, 20:22
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shutdownall



Joined: 02 Apr 2010
Posts: 518
Location: Munich
shutdownall
And yes, section is wrong.
Should be posted in OS construction ... (for bootloaders).
Post 29 Nov 2011, 20:25
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mbr_tsr



Joined: 03 Apr 2011
Posts: 4903
mbr_tsr
ECS:EIP Ha ha i have DQ Double Quad Word Math U when you dq it splits the whole thing in half and flips it then splits each quarter in half and flips it then splits and flips again, dq 0xFFFFFFFFFFFFFFFF i cracked the 64 bit code you try to inc qword [cs:MyDQ] u can't unless you do the butterfly flip formula.
Post 03 Dec 2011, 02:21
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