[syslinux] isohybrid --mac doesn't find the mac efi image
Thomas Schmitt
scdbackup at gmx.net
Sun Feb 9 00:46:56 PST 2014
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
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