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The way how logical partition, or "Logical Resizable Android Partitions"
as they say in AOSP source code, is setup makes it impossible to early
mount the partitions from the shared super partition with just
a few lines of code; in fact, AOSP has a whole "fs_mgr" folder which
consist of multiple complex libraries, with 15K lines of code just
to deal with the device mapper shenanigans.
In order to keep the already overly complicated MagiskInit more
managable, I chose NOT to go the route of including fs_mgr directly
into MagiskInit. Luckily, starting from Android Q, Google decided to
split init startup into 3 stages, with the first stage doing _only_
early mount. This is great news, because we can simply let the stock
init do its own thing for us, and we intercept the bootup sequence.
So the workflow can be visualized roughly below:
Magisk First Stage --> First Stage Mount --> Magisk Second Stage --+
(MagiskInit) (Original Init) (MagiskInit) +
+
+
...Rest of the boot... <-- Second Stage <-- Selinux Setup <--+
(__________________ Original Init ____________________)
The catch here is that after doing all the first stage mounting, /init
will pivot /system as root directory (/), leaving us impossible to
regain control after we hand it over. So the solution here is to patch
fstab in /first_stage_ramdisk on-the-fly to redirect /system to
/system_root, making the original init do all the hard work for
us and mount required early mount partitions, but skips the step of
switching root directory. It will also conveniently hand over execution
back to MagiskInit, which we will reuse the routine for patching
root directory in normal system-as-root situations.
Magisk
Downloads | Documentation | XDA Thread
Introduction
Magisk is a suite of open source tools for customizing Android, supporting devices higher than Android 4.2 (API 17). It covers the fundamental parts for Android customization: root, boot scripts, SELinux patches, AVB2.0 / dm-verity / forceencrypt removals etc.
Furthermore, Magisk provides a Systemless Interface to alter the system (or vendor) arbitrarily while the actual partitions stay completely intact. With its systemless nature along with several other hacks, Magisk can hide modifications from nearly any system integrity verifications used in banking apps, corporation monitoring apps, game cheat detections, and most importantly Google's SafetyNet API.
Bug Reports
Make sure to install the latest Canary Build before reporting any bugs! DO NOT report bugs that is already fixed upstream. Follow the instructions in the Canary Channel XDA Thread, and report a bug either by opening an issue on GitHub or directly in the thread.
Building Environment Requirements
- Python 3: run
build.pyscript - Java Development Kit (JDK) 8: Compile Magisk Manager and sign zips
- Latest Android SDK: set
ANDROID_HOMEenvironment variable to the path to Android SDK - Android NDK: Install NDK along with SDK (
$ANDROID_HOME/ndk-bundle), or optionally specify a custom pathANDROID_NDK_HOME - (Windows Only) Python package Colorama: Install with
pip install colorama, used for ANSI color codes
Building Notes and Instructions
- Clone sources with submodules:
git clone --recurse-submodules https://github.com/topjohnwu/Magisk.git - Building is supported on macOS, Linux, and Windows. Official releases are built and tested with FrankeNDK; point
ANDROID_NDK_HOMEto FrankeNDK if you want to use it for compiling. - Set configurations in
config.prop. A sample fileconfig.prop.sampleis provided as an example. - Run
build.pywith argument-hto see the built-in help message. The-hoption also works for each supported actions, e.g../build.py binary -h - By default,
build.pybuild binaries and Magisk Manager in debug mode. If you want to build Magisk Manager in release mode (via the-r, --releaseflag), you need a Java Keystore filerelease-key.jks(onlyJKSformat is supported) to sign APKs and zips. For more information, check out Google's Official Documentation.
Translations
Default string resources for Magisk Manager are scattered throughout
app/src/main/res/values/strings.xmlstub/src/main/res/values/strings.xmlshared/src/main/res/values/strings.xml
Translate each and place them in the respective locations (<module>/src/main/res/values-<lang>/strings.xml).
Signature Verification
Official release zips and APKs are signed with my personal private key. You can verify the key certificate to make sure the binaries you downloaded are not manipulated in anyway.
# Use the keytool command from JDK to print certificates
keytool -printcert -jarfile <APK or Magisk zip>
# The output should contain the following signature
Owner: CN=John Wu, L=Taipei, C=TW
Issuer: CN=John Wu, L=Taipei, C=TW
Serial number: 50514879
Valid from: Sun Aug 14 13:23:44 EDT 2016 until: Tue Jul 21 13:23:44 EDT 2116
Certificate fingerprints:
MD5: CE:DA:68:C1:E1:74:71:0A:EF:58:89:7D:AE:6E:AB:4F
SHA1: DC:0F:2B:61:CB:D7:E9:D3:DB:BE:06:0B:2B:87:0D:46:BB:06:02:11
SHA256: B4:CB:83:B4:DA:D9:9F:99:7D:BE:87:2F:01:3A:A1:6C:14:EE:C4:1D:16:70:21:F3:71:F7:E1:33:0F:27:3E:E6
Signature algorithm name: SHA256withRSA
Version: 3
License
Magisk, including all git submodules are free software:
you can redistribute it and/or modify it under the terms of the
GNU General Public License as published by the Free Software Foundation,
either version 3 of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.