Re: [Bug-xorriso] Test Proposal for [bug #46716] Protective MBR partition is not marked as bootable

[Thomas Schmitt]

Hi,

i wrote:
> > Ain't that a bug ?

Andrei Borzenkov wrote:
> What exactly?

Partition type "msdos" with block size 2048.
If GRUB2 accepts "msdos" on CDROM, then it should not make such
a weird assumption.


i wrote:
> > one could set 512 as soon as partition type "msdos" is detected.

Andrei Borzenkov wrote:
> Yes, that may be an option. 

It would give users the choice between UEFI 2.4, 5.2.1, Figure 16
and UEFI 2.4, 5.2.3, Figure 17.

Currently it looks like one could make the 5.2.1 image as variation
of the normal 5.2.3 image by just these changes to the xorriso options
in grub-mkrescue:
  - omitting HFS+ related options
  - omitting -efi-boot-part "--efi-boot-image"
  - adding -no-pad (saves 300 KiB)
  - adding -append_partition 2 0xef ...local.address.of.efi.img...
Supported by xorriso releases since at least 2.5 years.

As stated, i consider to avoid the waste of a duplicate efi.img
in a future xorriso version. "Ceterum censeo ..." - Cato.


> So it still looks like adding dummy bootable partition to MBR
> is the least evil.

It would need patching of the xorriso output or a future release
of xorriso.

If you want such an option for grub-mkrescue then i am willing
to implement it. (-shadow_mbr_part ? --mbr-boot-dummy ?
Not easy to describe its nature and purpose. -alexanders_partition ?)


> > I wonder how the machine came to "Windows".

> On Mac this is synonym for "legacy BIOS" or "CSM" boot.

The x86 code in the MBR together with the bootability flag ?
(Afaik this hops onto the BIOS El Torito boot image
 /boot/grub/i386-pc/eltorito.img )

That 2012 Mac seems to be quite open towards boot paths.


Have a nice day :)

Thomas