Re: [PATCH v2 08/12] kern: Make grub_error() more verbose

[Didier Spaier]

Le 06/03/2020 à 18:03, David Michael a écrit :
> On Fri, Mar 6, 2020 at 9:02 AM Didier Spaier <address@hidden> wrote:
>> Le 06/03/2020 à 13:43, Daniel Kiper a écrit :
>>> If we go that way then we have to care about them by the end of the
>>> universe. And this means more and more issues like [1]. If somebody
>>> wants to use new GRUB then he/she have to reinstall the machine or
>>> something like that. IMO we should not care about users who do not want
>>> upgrade their machines or whatnot. Or at least their choices cannot
>>> impact GRUB development too much. And I think that this MBR constraint
>>> is hindering the project too much at this point. So, as above...
>>>
>>> Sorry for being blunt...
>>
>> Sorry to be off topic... In case of a GUID partition table, if I
>> understand the UEFI specification[1], as the first usable LBA should be
>> greater than or equal to 34 for a 512 bytes block size or 6 for a
>> 4096 bytes logical block size, it could begin after a gap of 24K.
>>
>> Then, if we assume that the first partition begins @ 1MiB, can't GRUB
>> use the space unused between the first usable LBA and 1MiB instead of
>> a Bios Boot partition, in case of "legacy" booting and a GPT? I ask as
>> then a Bios Boot partition wouldn't be necessary any more.
> 
> It would be best to use a boot partition so the core.img space is
> reserved by the GPT, but I once wanted to tack i386-pc GRUB onto an
> existing UEFI GPT disk, so I wrote the commands that do what you're
> describing here:
> 
> https://github.com/dm0-/installer/blob/master/examples/systems/fitpc.sh#L151-L178
> 
> I may be misremembering, but I think the core.img size was limited to
> around half a megabyte, so it should be safe to write it to the unused
> ~1MiB before the first partition after the GPT.  But yes, using the
> boot partition would probably be for the best if you are formatting a
> new disk.

Thanks for sharing David. This can be useful to allow Legacy booting
off a drive initially partitioned for UEFI booting only.