Dual Booting 64 Bit devices

Patching Bootchain

Decrypt iBSS and iBEC:

Firmware keys and proper component names can be found here.

img4 -i iBSS.* -o iBSS.dec -k iv_key

img4 -i iBEC.* -o iBEC.dec -k iv_key

And patch signature checks using iBoot64Patcher:

iBoot64Patcher iBSS.dec iBSS.patched

Now pack into img4:

img4 -i iBSS.patched -o iBSS.img4 -M IM4M -A -T ibss

Important: we need to create two patched iBEC files; One for booting the custom ramdisk, and one for booting the new system.

For booting the second iOS install, iBEC needs an arg which will point it towards the new partition. Add rd=disk0s1s3 (or your new system partition disk) and -v args to iBEC:

iBoot64Patcher iBEC.dec iBEC.patched -b “rd=disk0s1s3 -v”



For booting the custom ramdisk, add rd=md0 restore -v args to iBEC:

iBoot64Patcher iBEC.dec iBECramdisk.patched -b “rd=md0 -restore -v”

Now pack them back into img4:

img4 -i iBECramdisk.patched -o iBECramdisk.img4 -M IM4M -A -T ibec

img4 -i iBEC.patched -o iBEC.img4 -M IM4M -A -T ibec

Great! now there are two different iBEC files you have created. One for booting the ramdisk, and the other for booting the actual system later on.

Note: the rd argument in iBEC stands for "root device", or the target volume iBoot will try to start the system from. md0 always refers to a ramdisk in memory, and disk0s1sX is a disk partition.

Patching Kernelcache:

AMFI

We need to patch amfi in kernel to make the ramdisk load custom binaries. Unpack the kernelcache:

img4 -i kernelcache.* -o kcache.raw

Automatically Patching

To simplify dual booting process I wrote a utility based on patchfinder64 that will automatically patch the kernel:

Kernel64Patcher kcache.raw kcache.patched -a


Create a patch file:

touch kc.bpatch

Note: you can use Hex Fiend to compare the original raw kernelcache and patched kernelcache or this python script for creating diff file:

python3 compareFiles.py kcache.raw kcache.patched


Apply it and sign using img4:

img4 -i kernelcache.release.* -o kernelcache.img4 -M IM4M -T rkrn -P kc.bpatch

DeviceTree

Pack devicetree into img4 with rdtr (RestoreDevicetree) tag. The devicetree needs this tag, otherwise iBEC will refuse to see it as valid:

img4 -i devicetree.XXXXX.im4p -o devicetree.img4 -M IM4M -T rdtr

Done!
Next part → Making Ramdisk

Dual Booting 64 Bit