Bug#345931: A patch solving #345931

[Robert Millan]

On Mon, Sep 11, 2006 at 06:26:37PM +0200, Mats Erik Andersson wrote:
>   Venerable Maintainers of Grub,
> 
>  I offer you a patch that should close bug report  
>  #345931.
>  
>  The patch has been built on top of grub-0.97-13 with
>  success and it repaired with honours mbr-installs of
> 
>         grub-0.97-1ubuntu1   on kubuntu 6.0.6
>   and
>         grub-0.95+cvs20040624-17sarge1 on Debian
> Sarge.

Does your patch work with grub from debian sid?

Does GRUB 2 also exhibit this problem?


>  As you will see the coding is independent of any
>  Debian patches and contains a few lines of code for
>  the source file
> 
>          grub-0.97/stage2/builtins.c
> 
>  and thus would easily integrate in the upstream  
>  version 0.97. I leave to you to decide whether the 
>  author ought to be informed, since I am still a
>  novice in these matters.
> 
>           Best regards
> 
>             Mats Erik Andersson
>             ynglingatal at yahoo.se
Content-Description: 526972506-drive_correction.diff
> diff -Naur grub-0.97.orig/stage2/builtins.c grub-0.97/stage2/builtins.c
> --- grub-0.97.orig/stage2/builtins.c	2006-09-11 16:08:32.261227280 +0200
> +++ grub-0.97/stage2/builtins.c	2006-09-11 16:15:54.035067448 +0200
> @@ -1953,13 +1953,30 @@
>    *((unsigned char *) (stage1_buffer + STAGE1_FORCE_LBA)) = is_force_lba;
>  
>    /* If DEST_DRIVE is a hard disk, enable the workaround, which is
> -     for buggy BIOSes which don't pass boot drive correctly. Instead,
> -     they pass 0x00 or 0x01 even when booted from 0x80.  */
> +   * for buggy BIOSes which don't pass boot drive correctly. Instead,
> +   *  they pass 0x00 or 0x01 even when booted from 0x80.  */
>    if (dest_drive & BIOS_FLAG_FIXED_DISK)
> -    /* Replace the jmp (2 bytes) with double nop's.  */
> -    *((unsigned short *) (stage1_buffer + STAGE1_BOOT_DRIVE_CHECK))
> -      = 0x9090;
> -  
> +  {
> +    if ( *((unsigned char *) (stage1_buffer + STAGE1_BOOT_DRIVE_CHECK)) == 0xeb )
> +            /* For version 0.97: 
> +	     * Replace the jmp (2 bytes) with double nop's.  */
> +       *((unsigned short *) (stage1_buffer + STAGE1_BOOT_DRIVE_CHECK))
> +         = 0x9090;
> +    else if ( *((unsigned char *) (stage1_buffer + STAGE1_BOOT_DRIVE_CHECK)) == 0x80 )
> +         {   
> +            /* For versions 0.94-96:
> +	     *  Set the boot drive mask. This is a workaround for buggy BIOSes which
> +            *  don't pass boot drive correctly. Instead, they pass 0x00 even when
> +            *  booted from 0x80.
> +	     *  Rem: the old STAGE1_BOOT_DRIVE_MASK equals STAGE1_BOOT_DRIVE_CHECK + 2  */
> +         *((unsigned char *) (stage1_buffer + STAGE1_BOOT_DRIVE_CHECK + 2 ))
> +             = (dest_drive & BIOS_FLAG_FIXED_DISK);
> +	  }
> +        else
> +	      /* The boot sector is older than version 0.94.
> +	       * Changing to a "nop" could make 0.92 and 0.93 acceptable. */
> +	   goto fail;
> +  }
>    /* Read the first sector of Stage 2.  */
>    disk_read_hook = disk_read_savesect_func;
>    if (grub_read (stage2_first_buffer, SECTOR_SIZE) != SECTOR_SIZE)

-- 
Robert Millan

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