Re: How to debug 'out of disk' error.

[Lennart Sorensen]

On Wed, Mar 16, 2011 at 03:23:58PM -0400, Lennart Sorensen wrote:
> On Wed, Mar 16, 2011 at 03:19:48PM -0400, Phillip Susi wrote:
> > On 3/16/2011 1:32 PM, Lennart Sorensen wrote:
> > > So I now have some debug info:
> > > 
> > > version=48
> > > total_sectors=156312576 C=16383 H=16 S=63
> > > error: hd0,msdos1 out of disk.
> > > Entering rescue mode...
> > > grub rescue>
> > > 
> > > So version is returning something, and it is actually getting the disk
> > > size properly.  I wonder what else could cause the out of disk message
> > > then.
> > 
> > What does the partition table look like?  It doesn't extend beyond
> > sector 156312575 does it?
> > 
> > Also I wonder about why H=16.  It should be 255.
> 
> Well usually it should, but not always.
> 
> Here is the partition table:
> 
> Disk /dev/sda: 80.0 GB, 80032038912 bytes
> 255 heads, 63 sectors/track, 9730 cylinders, total 156312576 sectors
> Units = sectors of 1 * 512 = 512 bytes
> Sector size (logical/physical): 512 bytes / 512 bytes
> I/O size (minimum/optimal): 512 bytes / 512 bytes
> Disk identifier: 0x0004a073
> 
>    Device Boot      Start         End      Blocks   Id  System
> /dev/sda1   *        2048   152350719    76174336   83  Linux
> /dev/sda2       152352766   156311551     1979393    5  Extended
> /dev/sda5       152352768   156311551     1979392   82  Linux swap / Solaris

I have now determined that the call to grub_biosdisk_rw_int13_extensions
fails here:

        if (grub_biosdisk_rw_int13_extensions (cmd + 0x42, data->drive, dap))
          {
            /* Fall back to the CHS mode.  */
            data->flags &= ~GRUB_BIOSDISK_FLAG_LBA;
            disk->total_sectors = data->cylinders * data->heads * data->sectors;
            return grub_biosdisk_rw (cmd, disk, sector, size, segment);
          }

Then LBA gets disabled, and access beyond CHS range is gone, and the
error about 'out of disk' happens.

-- 
Len Sorensen