Re: Windows,grub and grub2

[Viswesh S]

Hi,



----- Original Message ----
> From: Bean <address@hidden>
> To: The development of GRUB 2 <address@hidden>
> Sent: Tuesday, 23 September, 2008 7:20:49 PM
> Subject: Re: Windows,grub and grub2
> 
> On Tue, Sep 23, 2008 at 4:23 PM, Viswesh S wrote:
> >
> >
> >
> >
> > ----- Original Message ----
> >> From: Bean 
> >> To: The development of GRUB 2 
> >> Sent: Monday, 22 September, 2008 9:10:26 AM
> >> Subject: Re: Windows,grub and grub2
> >>
> >> On Tue, Sep 9, 2008 at 2:00 PM, Viswesh S 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
> >>
> >>
> >
> > Hi,
> >
> > The value of boot drive is 0x80.
> >
> > This was the same value in disk->drive also.
> 
> Hi,
> 
> Interesting, perhaps %dx is changed somewhere. Please try the
> following patch, it dumps the value of %dx just before jumping to the
> boot sector.
> 
> -- 
> Bean

The patch works and now Windows is booting perfectly fine from Grub2. 

I will go through the assembly and try to understand what modifications you 
have done.So there is a problem in Grub2 code, which needs to be fixed ?

Till this point, I was chainloading grub from Grub2 and then chainloading 
Windows2008 from it.

Thanks for the consistent help till this point and for the future also.

Viswesh



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