Re: Current status on grub-installer on PowerMac

[Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>]

On 14/04/2021 12:53, John Paul Adrian Glaubitz wrote:

> > > FWIW, I also found a number of bugs in GRUB on PowerMac itself while working
> > > on the problem. It turns out that GRUB does not set the proper openfirmware
> > > path in NVRAM pointing to the BootX script that it just installed. The script
> > > gets installed into :System:Library:CoreServices:BootX but grub-install (the
> > > upstream GRUB installation tool) just sets the path to :BootX.
> >
> > I would expect this to work since BootX is simply the filename and so it is a
> > relative path reference, presumably to the blessed CoreServices directory.
> > Otherwise you'd end up using an absolute path in the form \path\to\BootX.
>
> The problem was simply that the HFS filesystem had to be unmounted before accessing
> with hfsutils. It works now. Currently performing the final test.

Excellent!

> > > Also, while GRUB's grub-install blesses the "CoreServices" folder, it does
> > > not set the "tbxi" attribute which means it's not possible to boot the disk
> > > with "boot hd:N,:\\tbxi" (N being the partition).
> >
> > That should be an easy fix now that you've got hattrib working:
> >
> >     hattrib -t tbxi -c chrp path/to/BootX
>
> Not sure why to pass "-c chrp" here as all the instructions I have seen for
> PowerMac pass "-c UNIX".

(goes and looks)

From what I can see there is a mixture of creator types: chrp is mentioned for 
FreeBSD and BootX, whilst most of the grub references suggest using UNIX. Having a 
look around the OpenBIOS code I think the creator type is only used in the absence of 
a blessed directory, so either will do fine.

> > I'm curious as to how grub-install currently handles the blessing of the CoreServices
> > directory for different filesystems - does it only attempt to bless the folder if it
> > detects a HFS/HFS+ filesystem?
>
> Seems so. See the grub-install source code.
>
> > Finally it may be worth noting that if you omit the partition number then the firmware
> > will locate the first bootable partition itself which is the default value that OpenBIOS
> > uses, e.g.
> >
> >     boot hd:,\\:tbxi
>
> I'm just using the path provided by "opathname" as this way we can install onto any type
> of media instead of just hard disks.
>
> > > And, finally, GRUB's grub-install never substitutes the variable names "device"
> > > and "partition" in the boot script [3] it installs. They just remain as is on
> > > the disk which naturally means that grub-install currently cannot itself properly
> > > install GRUB on a PowerMac which is obviously a bug.
> >
> > This shouldn't be needed. Having a look at grub.chrp.in from your link and ofboot.b
> on some old Fedora ISOs I have lying around, these files are all CHRP boot scripts
> > i.e. XML surrounded by <CHRP-BOOT>...</CHRP-BOOT> tags.
> >
> > IIRC it is part of the CHRP boot specification that the firmware substitutes the values
> > for "&device;" and "&partition;" in <BOOT-SCRIPT>...</BOOT-SCRIPT> when reading the CHRP
> > boot script into memory, and that's certainly what OpenBIOS does.
>
> Ah, I wasn't aware of that.
>
> > I guess the real question is does Apple's OF do the right thing here? My feeling is that it
> > does, since grub.chrp.in uses the hard-coded path \System\Library\CoreServices\grub.elf
> > which is a directory that only exists if grub is installed on a MacOS computer.
>
> I can try removing the sed command from grub-installer again and see if that still works.
>
> Currently, I have:
>
> sed -i 's!&device;:&partition;!'"$ofpath"'!g' $ROOT/boot/grub/System/Library/CoreServices/BootX

Out of curiosity did it still work when you removed this?


ATB,

Mark.