[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: GRUB booting Mac OS X (xnu)

From: Chris Murphy
Subject: Re: GRUB booting Mac OS X (xnu)
Date: Mon, 27 Oct 2014 10:30:31 -0600

On Oct 27, 2014, at 1:39 AM, Andrei Borzenkov <address@hidden> wrote:

> It does not look like anything needs to
> be changed in grub2 though. You will need to modify os-prober to
> return efi loader type in this case; grub2 already supports
> chainloading EFI binary in 30_os-prober.

30_os-prober creates this entry for EFI systems:
 284              chainloader /EFI/${DEVICE}

This won't work on Macs, because the OS X bootloader isn't a.) on the ESP and 
b.) isn't in an \EFI directory.

So it looks like os-prober needs to look for the Apple Boot partitiontypeGUID, 
pass that device to 30_os-prober which can then do:
                chainloader /System/Library/CoreServices/boot.efi

Currently 30_os-prober lines 44 to 103 appear obsolete and should be removed. 
That's what creates the OS X entries right now using the various xnu modules.

> You still need to keep current xnu loader (and macosx os-prober type)
> for the case of CSM boot though.

What's the use case for this? Something like linux BIOS installation with i386 
version of GRUB, and it uses the xnu modules to EFI boot OS X? OK, but that's 
still broken today and going forward because neither GRUB nor linux can read 
Core Storage, which is where the xnu kernel and its initramfs are found. And 
anyone using any version of OS X for the past three years with full disk 
encryption likewise can't use GRUB xnu modules to EFI boot OS X from CSM mode 
either. This seems like a very legacy use case.

If it's possible to have an i386 30_os-prober that keeps the current osx xnu 
module boot entries intact; but on x86_64 the 30_os-prober makes the grub.cfg 
with chainloader, then I'm fine with that.

>> The Apple Boot [1] is used by OS X 10.7 through 10.10, so it's a good start 
>> point to search for OS X since it won't be anywhere else.
> give grub device name; it is file system and has UUID right? So it is
> going to find it during boot just fine.

Yes, I mean for grub-mkconfig to create the entry via os-prober it's going to 
need to know to only look for OS X's bootloader that has the Apple Boot 
partitiontype GUID because it's not going to find it anywhere else. And if it 
does, it's not really an OS X bootloader, it's likely a renamed grubx64.efi 
masquerading as an OS X bootloader, so that the built-in firmware boot manager 
displays it as a boot option at start up time (which it doesn't do if the EFI 
binary is on the EFI System partition).

Chris Murphy

reply via email to

[Prev in Thread] Current Thread [Next in Thread]