Re: Windows,grub and grub2

[Bean]

On Tue, Sep 9, 2008 at 2:00 PM, Viswesh S <address@hidden> wrote:
> Below is the dump of screen output while chainloading the ntfsnew file.
> ***************************************
> DI=CFF0 SI=07EE BP=1FF0 SP=1FE8 BX=0000 DX=0000 CX=0000 AX=0000
> CS=0000 SS=0000 DS=0000 ES=0000 FG=0246 IP=7C57
>
> DI=7FF0 SI=07EE BP=1FF0 SP=7BF4 BX=55AA DX=0000 CX=0000 AX=0100 CX=07C0
> DS=07C0 ES=0000 FG=0007 IP=0082
> ******************************************
> Could you please let me know the way to disassemble the binary file without
> any header.The way in which you decoded the boot record.
>
> Also one more thing to let you know is that,
>
> with the grub-1.96 ( without the chainloader patch of disk->dev->read() ) ,
> with windows2003 in partition 1 and linux in partition 3, when we chainload,
> if we look at the partition table passed to another bootloader ie location
> 0x7be - we can see that it is junk, but the surprising point is that, in
> this case as I have mentioned in my first mail, windows boots up from
> grub2.So it is that the partition table is not required for the chainloader
> thing and just the boot record is sufficient

Hi,

Oh, sorry for another long delay. I disassemble the file with ida,
which is an amazing tool. I don't know if there is open source
alternative, please let me know if you find one.

The output from ida is in masm format, I modify it a bit so that it
can be compiled using nasm. Please note that nasm doesn't generate the
same binary file as original one, but you can get an idea what it
does.

>From the output, the program fails at the second int 13 call, int
13/ah = 48h. Although I notice that DL=0, which is not supposed to
happen. Perhaps you can add a grub_printf in grub_chainloader_boot to
show the value of boot drive:

static grub_err_t
grub_chainloader_boot (void)
{
  grub_printf ("boot_drive=%d\n", boot_drive);
  grub_chainloader_real_boot (boot_drive, boot_part_addr);

  /* Never reach here.  */
  return GRUB_ERR_NONE;
}

-- 
Bean