When Apple firmware boots a kernel, it passes a device tree in a binary format. This format is very similar to, but different from, the Open Firmware standard expected by Linux.
Like Linux devicetrees, the Apple device tree (ADT) encodes a number of untyped byte arrays (properties) in a hierarchy of nodes. These describe the available hardware, or provide other information that Apple thinks the firmware might need to tell the kernel about. This includes identifying and secret information like serial numbers and WiFi keys.
The main difference between ADTs and Linux DTs is byte order; since properties are untyped, we can't automatically correct for that.
Obtaining your ADT
Given hardware, you can access your ADT in a number of ways.
Option 1: via m1n1 debug console.
The easiest way is probably using m1n1 via adt.py
cd m1n1/proxyclient ; python -m m1n1.adt --retrieve dt.bin
This will write a file called "dt.bin" containing the raw (binary) ADT and print the decoded ADT.
Option 2: via macOS im4p files (Note: these are missing details filled in by iBoot during boot)
img4lib
Get a copy of xerub's img4lib
git clone https://github.com/xerub/img4lib
cd img4lib
make -C lzfse
make
make install
img4tool
Get a copy of tihmstar's img4tool (you will also need his libgeneral as well as autoconf, automate, libtool, pkg-config, openssl and libelist-2.0).
git clone https://github.com/tihmstar/libgeneral.git
git clone https://github.com/tihmstar/img4tool.git
then for each
./autogen.sh
make
make install
Obtaining device tree files
copy the im4p file from the below directory. See Devices for Machine 'j' model details.
/System/Volumes/Preboot/[UUID]/restore/Firmware/all_flash/DeviceTree.{model}.im4p
If the dir doesn't exist try disabling csrutil in recovery mode, going to settings and enabling terminal to acces all files, or start from Volumes/Macintosh HD/ because it may be symlinked. If it's still not accessible, try good ol sudo find . -type f -name '*.im4p'.
then use img4tool to extract the im4p file into a .bin file e.g.
img4tool -e DeviceTree.j274ap.im4p -o j274.bin
To do the same with img4lib, do
img4 -i DeviceTree.j274ap.im4p -o j274.bin
Option 3: From macOS
You can get a textual representation of the ADT directly from macOS by running:
ioreg -p IODeviceTree -l | cat
While this does not require decoding, it outputs much less information than using m1n1 (see below).
Decoding an ADT
after m1n1 installation (see repo page)
cd m1n1/proxyclient
get construct python library (not a construct.py file, it's a library)
pip install construct
copy obtained j{*}.bin file into proxyclient dir && extract by:
python -m m1n1.adt j{*}.bin
You can also get a memory map with the -a option:
python -m m1n1.adt -a j{*}.bin
Other ways?
Feature Support:
Project related:
Platform documentation:
For users:
For developers:
- Yaks in need of shaving (HELP WANTED!)
- Tethered Boot Setup (For Developers)
- m1n1:User Guide Boot loader
- Hypervisor
- U-Boot
- Devicetree bindings
- Open OS ecosystem on Apple Silicon Macs
Wiki for the Asahi Linux project: https://asahilinux.org/