[syslinux] [PATCH] chain.c32: add support for loading GRUB stage2

[H. Peter Anvin]

On 06/08/2010 02:15 PM, Paul Bolle wrote:
> On Tue, 2010-06-08 at 19:24 +0200, Thomas Bächler wrote:
>>> GRUB's loading mechanism allows to somehow provide stage2 with the
>>> selected disk and partition, BSD slice, etc. (ie, to tell stage2 what
>>> it's "root" is). I don't yet understand the notation used in that
>>> mechanism. Besides, since stage2 images will not necessarily be loaded
>>> from the disk (and partition, etc.) they were installed to, it seems
>>> best to just use the first disk.
>>
>> I believe that is not the purpose of stage2's "root". When stage2 is
>> loaded, it looks for a file /grub/menu.lst or /boot/grub/menu.lst to
>> read a configuration from. My guess is that the "root" in this case is
>> the device where it looks for that file.
> 
> That seems to be what's happening. "root" is more general, though. It's
> basically used as the default, well, root for all files (kernel, initrd,
> configuration files, etc.) GRUB is supposed to handle.
> 
>> Without menu.lst, grub will just show a prompt. If I am right, it would
>> be very useful to be able to APPEND a "root" so that a chainloaded grub
>> can load a configuration file without user intervention.
> 
> GRUB's stage2 doesn't have a command line itself, does it? That implies
> APPEND is not the most obvious way to supply GRUB's stage2 with
> additional parameters.
> 

No, the right way is to pass in the disk coordinates via the Multiboot
field.  It requires partition-scanning code in mboot.c32 which I so far
have avoided putting in, but I guess it's time.

	-hpa