Follow-up Comment #2, bug #29464 (project grub):
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/disk.c::grub_disk_open():
grub_dprintf("disk", "grub_disk_dev_list %sn", 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", "%sn", "GRUB_ERR_NONE");
break;
}
else if (grub_errno == GRUB_ERR_UNKNOWN_DEVICE) {
grub_errno = GRUB_ERR_NONE;
grub_dprintf("disk", "%sn", "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.
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