Comment 5 for bug 555500

After adding several debugging fprintf statements the reason for this problem seems to become clear. grub-setup calls grub_disk_open() which in turn calls an open() function via an array of pointers. Here's the source-code peppered with my debug print statements from kern/desk.c::grub_disk_open():

  grub_dprintf("disk", "grub_disk_dev_list %s\n", raw);
  for (dev = grub_disk_dev_list; dev; dev = dev->next)
    {
      grub_dprintf("disk", "dev->open (%p)\n", (void *) dev->open);
      if ((dev->open) (raw, disk) == GRUB_ERR_NONE) {
       grub_dprintf("disk", "%s\n", "GRUB_ERR_NONE");
 break;
      }
      else if (grub_errno == GRUB_ERR_UNKNOWN_DEVICE) {
 grub_errno = GRUB_ERR_NONE;
       grub_dprintf("disk", "%s\n", "GRUB_ERR_UNKNOWN_DEVICE");
      }
      else
 goto fail;
    }

Running grub-setup with extra debug info output to stdout:

sudo ./grub-setup -vvv '(hd0)' >grub-setup.log 2>grub-setup.stderr.log

shows:

grub-setup: opening destination 'hd0'
/home/all/SourceCode/grub/grub2-1.98/kern/disk.c:245: Opening `hd0'...
/home/all/SourceCode/grub/grub2-1.98/kern/disk.c:268: grub_disk_dev_list hd0
/home/all/SourceCode/grub/grub2-1.98/kern/disk.c:271: dev->open (0x80754f7)
/home/all/SourceCode/grub/grub2-1.98/kern/disk.c:278: GRUB_ERR_UNKNOWN_DEVICE
/home/all/SourceCode/grub/grub2-1.98/kern/disk.c:271: dev->open (0x80740b0)
/home/all/SourceCode/grub/grub2-1.98/kern/disk.c:278: GRUB_ERR_UNKNOWN_DEVICE
/home/all/SourceCode/grub/grub2-1.98/kern/disk.c:271: dev->open (0x804b6d6)
grub_util_biosdisk_open(hd0)
find_grub_drive(hd0)
i=0 hd0
find_grub_drive(hd0) returned 0
setting disk->id=0
/home/all/SourceCode/grub/grub2-1.98/kern/disk.c:273: GRUB_ERR_NONE
grub-setup: testing: disk->id = 0

So find_grub_drive() is the function returning 0.

That function simply iterates through an array called 'map' that contains the contents of /boot/grub/device.map. The first entry in 'map' (map[0]) represents the first line in the device.map file.

From that it is now possible to see why the id is set to 0 and therefore why the buggy BIOS work-around never gets applied to the boot sector.