[syslinux] isohybrid --mac doesn't find the mac efi image

[email@missionaccomplish.com]

We been trying to boot the image in vbox using efi emulation but it complains about kernel not supporting handover. Anyways, I will take your advice and get back to you tomorrow. I think we might be getting close to a successful boot on Mac OSX hardware and any other UEFI capable hardware.

Thanks for your help and tomorrow I should come with more data to debug. 

P.S the latest fedora ISO seems to boot fine in vbox perhaps you might want to look at their image. Enjoy the rest of your weekend.

Sent from my HTC

----- Reply message -----
From: "Thomas Schmitt" <scdbackup at gmx.net>
To: <syslinux at zytor.com>
Cc: <email at missionaccomplish.com>
Subject: isohybrid --mac doesn't find the mac efi image
Date: Sun, Feb 9, 2014 3:46 am


Hi,

i wrote:
> >  -eltorito-id "MAC" \
Fernando Reyes wrote:
> thanks a lot, that seems to allow isohybrid --mac to work \o/

This confirms my theory why isohybrid.c fails.

But to state it again:

I do believe isohybrid --gpt --mac is buggy, and it should not
be necessary to be applied to a xorriso generated image that
used -isohybrid-mbr for the BIOS image, and -isohybrid-gpt-basdat
-isohybrid-apm-hfsplus for the EFI and the MAC boot image.

Just try to boot it as it comes out of xorriso.


[gdisk GPT report after applying isohybrid --gpt --mac :]
>   2           42552           52615   4.9 MiB     0700  [8-bit salad]
>   3            2232           42551   19.7 MiB    AF00  [8-bit salad]
>  ok, I don't know what that garble text is above.

This is the most obvious one of the bugs of isohybrid.c.
It writes the C constant "ISOHybrid" (10 bytes) as 20 bytes into
the GPT partition entry, in the hope that it would become UTF-16
encoded. I am not aware of any gcc option which would support that
hope.
It does similar with "ISOHybrid ISO" for the first partition that
covers the whole ISO image but is not shown by gdisk.
(See memcpy() in lines 795, 804, 817 of utils/isohybrid.c)


gdisk reports:
>   APM: not present

Interesting question why gdisk does not recognize the Apple
Partiton Map of xorriso and isohybrid.c alike.
Do Macs recognize it ?

> Using GPT and creating fresh protective MBR.

Let's hope that it does not write that MBR into the ISO.

> Warning! Main partition table overlaps the first partition by 64 blocks!

This is a consequence of the mjg multi-hybrid layout,
which prescribes nested partitions.
There is a school of thought which emphasizes that partitions
should not be nested (see the results of GRUB2's grub-mkrescue
with EFI support).

------------------------------------------------------------

If you really rely on Apple Partition Map and macboot.img,
then test this with all machines in reach.
If there arise problems, then send me the first 64 kB of
your image for inspection, or upload it as a whole and tell
me where i can get it.

I would be interested to learn the hardware model name and the
MacOS system name of an example that actually boots via APM and
the HFS+ image macboot.img.


Have a nice day :)

Thomas