AAOS - Build Automotive Android

Tags: automotiveandroid

Android Automotive extends Android, by adding support for automotive-specific requirements, features, and technologies. It shares the same codebase with Android Open Source Project for phone, tablets, etc.

For General guide for Android Devices: https://source.android.com/docs/setup.
For Automotive Android Devices: https://source.android.com/docs/automotive.

Host Requirements

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Refer: https://source.android.com/docs/setup/start/requirements.

Minimal Hardware

• 64-bit Linux System with glibc >= 2.17 (check with ldd --version)
• 512 GB SSD (need more when using repo mirroring)
• 16 GB RAM (need more when using more parallel threads -jN)

Build tools

Required packages:

sudo apt update
sudo apt install git-core gnupg flex bison build-essential zip curl zlib1g-dev libc6-dev-i386 x11proto-core-dev libx11-dev lib32z1-dev libgl1-mesa-dev libxml2-utils xsltproc unzip fontconfig

May need these:

sudo apt install libncurses-dev software-properties-common

Recommend to use ccache for GCC/G++ compilation:

sudo apt install ccache
mkdir -p ~/.ccache
ccache -M 50G -F 0

Add below line into ~/.bashrc to use ccache for AOSP build:

export USE_CCACHE=1
export CCACHE_EXEC=$(which ccache)

Repo tool

The Repo launcher provides scripts that to checkout and download a full repo:

export REPO=$(mktemp /tmp/repo.XXXXXXXXX)
curl -o ${REPO} https://storage.googleapis.com/git-repo-downloads/repo
gpg --recv-keys 8BB9AD793E8E6153AF0F9A4416530D5E920F5C65
curl -s https://storage.googleapis.com/git-repo-downloads/repo.asc | gpg --verify - ${REPO} && sudo install -m 755 ${REPO} /usr/bin/repo

Android Source Code

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The Android source is located in a collection of Git repositories hosted by Google.

Download Repo

For the latest source code, default main branch is used (i.e. -b main).
For faster cloning, refer to Git partial clone and shallow clone.

repo init --partial-clone -u https://android.googlesource.com/platform/manifest

For a list of branches and tag names, see Source code tags and builds:

Codename	Version	API Level	Tag	Build ID	Security patch
Android15	15	35	android-15.0.0_r1	AP3A.240905.015.A2	2024-09-05
Android14	14	34	android-14.0.0_r74	AD1A.240905.004	2024-09-05
Android13	13	33	android-13.0.0_r83	TQ3A.230805.001.S1	2023-08-05
Android12L	12	32	android-12.1.0_r27	SP2A.220505.008	2022-05-05
Android12	12	31	android-12.1.0_r26	SD2A.220601.004.B2	2022-06-01

Selected branch: android-14.0.0_r74

At this time, it’s the latest stable version for development!

1. Define macros:

   export AOSP_HOME="$HOME/aosp"
   export AOSP_BRANCH="android-14.0.0_r74"

2. Initialize the repo using shallow clone:

   mkdir -p $AOSP_HOME/$AOSP_BRANCH
   cd $AOSP_HOME/$AOSP_BRANCH
   repo init --depth=1 -u https://android.googlesource.com/platform/manifest -b $AOSP_BRANCH

3. Sync (download) source code of the current branch:

   repo sync -c -j$(nproc)

Folders Structure

There are many folders in the root folder of AOSP, here are their short descriptions:

• Directoryart/ Implementation of Android Runtime layer,
  including Ahead-Of-Time (AOT) compilation, Just-In-Time (JIT) compilation.

  • …
• Directorybionic/ Android is not using glibc like most Linux distributions, instead,
  the c-library is called bionic based mostly on BSD-derived sources.

  • …
• Directorybootable/ Bootloader, and some tools for recovery, flashing such as fastboot.

  • …
• Directorybuild/ Scripts, Configurations for Build process, coordinating the compilation, linking, and packaging of various components.

  • …
• Directorycts/ The Compatibility Test suite to ensure that a build complies with the Android specification.

  • …
• Directorydalvik/ Dalvik VM has been replaced by the Android Runtime (ART) since Android 5.0

  • …
• Directorydevelopers/ Assist developers in building, testing, and optimizing Android applications.

  • …
• Directorydevelopment/ Development tools such as the SDK and NDK.

  • …
• Directorydevice/ Build configuration, hardware modules and specific code for different devices,
  containing BSP with overlay, board configs, device, kernel, and SEpolicy.

  • …
• Directoryexternal/ Contains source code for all external open source projects, such as SQLite, FreeType and WebKit.

  • …
• Directoryframeworks/ Implementation of key services such as System Server, Activity Managers, having the combination of Java and C/C++ native libraries where interaction between sources will happen, such as mapping between the java application APIs and the native C++ libraries.

  • …
• Directoryhardware/ The Android Hardware Abstraction Layer specification and implementation.

  • …
• Directorykernel/ Prebuilt kernel files. Just binary files, source code does not come here.

  • …
• Directorypackages/ Source code of default application such as Contacts, Calendar, etc.

  • …
• Directoryprebuilt/ Files that are distributed in binary form for convenience, including the cross compilations toolchain for different development machines.

  • …
• Directorysystem/ That is the minimal Linux system that is started before the Dalvik VM and any java based services are enabled.
  This includes the source code for the init process and the default init.rc script that provide the dynamic configuration of the platform.

  • …
• Directoryvendor/ It is vendor-specific and contains custom apps, SE policies, hardware configurations, and so on.
  This folder is not part of the AOSP source.

  • …

Source code Tools

• AOSP Build Environment is provided in the script build/envsetup.sh to initialize the workspace, and it must be always activated before any build.
• Android Code Search is an online source code searching engine, and cross referencing.
• Android Studio for Platform is the version of the Android Studio IDE for Android Open Source Project platform.

Set up Environment

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Activate AOSP Build Environment:

cd $AOSP_HOME/$AOSP_BRANCH
source build/envsetup.sh

This script provides methods to make different targets, commands for searching:

Make targets

List of make targets:

• make all - make everything, whether it is included in the product definition or not.
• make clean - remove all built files (prepare for a new build).
• make sdk - build the tools that are part of an SDK (adb, fastboot, etc.)
• make snod - build the system image from the current software binaries.
• make modules - shows a list of submodules that can be built.
• make <local_module> - make a specific module defined in LOCAL_MODULE in the Android.mk, not the same as directory name
• make clean-<local_module> - clean a specific module

Build Macros

• croot - change directory to the top of the tree
• m - execute make from the top of the tree (in any directory)
• mm - builds all the modules in the current directory
• mmm <dir1> ... - Builds all the modules in the supplied directories, but not their dependencies.
• mma - Builds all the modules in the current directory, and their dependencies.
• mmma <dir1> ... - Builds all the modules in the supplied directories, and their dependencies.
• allmod - List all of Modules.
• gomod <module> - Jump to the folder of calling module.
• outmod <module>- Returns the output file for the module (.so/.jar/.apk/…)

Search Macros

• cgrep <PATTERN> - Greps on all local C/C++ files.
• ggrep <PATTERN> - Greps on all local Gradle files.
• jgrep <PATTERN> - Greps on all local Java files.
• resgrep <PATTERN> - Greps on all local res/*.xml files.
• mangrep <PATTERN> - Greps on all local AndroidManifest.xml files.
• mgrep <PATTERN> - Greps on all local Makefiles files.
• sepgrep <PATTERN> - Greps on all local sepolicy files.
• sgrep <PATTERN> - Greps on all local source files.
• godir <filename> - Go to the directory containing a file

Select a Target

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There are some kinds of target device:

Physical Device

• This is the real hardware, but it is not always available
• The best environment to test and develop because it is how thing actually run with real devices and environment
• The build will need some specific packages for the target, such as the drivers, configurations (usually known as Board Support Packages)

Android Virtual Device

Android Emulator can run the entire Android Architecture with different Android Virtual Device (AVD) images:

• An AVD contains the full Android software stack, with many functional hooks to appeal to the use cases of the Android app developer
• This may present challenges when building an AVD with customized Android framework due to virtual drivers / devices
• The target is usually named sdk_car

Cuttlefish Virtual Device

Cuttlefish is a configurable virtual Android device that can run both remotely (using third-party cloud offerings such as Google Cloud Engine) and locally (on Linux x86 and ARM64 machines).

• Cuttlefish Virtual Device contains a configurable virtual Android device, including all of the framework code and any custom platform code
• Replicate the framework-based behavior of a real device with a focus on high fidelity by maintaining close alignment with the core framework
• The target is usually named aosp_cf_*_auto

Product Definition

The target selection is an option listed in COMMON_LUNCH_CHOICES which is defined across multiple AndroidProducts.mk files.

To see all lunch target, run the command:

lunch

Lunch menu .. Here are the common combinations:
     ...
     1.  aosp_cf_x86_64_auto-trunk_staging-userdebug
     2.  aosp_cf_x86_64_auto_mdnd-trunk_staging-userdebug
     ...
     3.  sdk_car_arm64-trunk_staging-userdebug
     4.  sdk_car_md_x86_64-trunk_staging-userdebug
     5.  sdk_car_portrait_x86_64-trunk_staging-userdebug
     6.  sdk_car_x86_64-trunk_staging-userdebug
     ...

If there is an error that prevents lunch to show all target. Here is a quick fix:

• run export TARGET_RELEASE=trunk_staging,
• then run build_build_var_cache,
• then finally run lunch again.

Each target name contains:

• TARGET_PRODUCT, for example, a combination of aosp for google AOSP, then optionally cf for cuttlefish device, then Architecture x86_64 and Hardware (codename) such as auto, to make the final name aosp_cf_x86_64_auto
• TARGET_RELEASE is set to trunk_staging.
• TARGET_BUILD_VARIANT is one of user (for production), userdebug (with debugging enabled), and eng (fast build, for development).

Build Cuttlefish Emulator

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Cuttlefish is recommended for platform development. Working on Automotive Android is likely to do something in the Platform side, so this is the first choice when selecting an emulator.

Selected target: aosp_cf_x86_64_auto-trunk_staging-userdebug

Select -eng version may have shorter compilation time, but it may have some bugs on emulator, due to incompatibility of the engineering tools for virtual hardware.

Build Cuttlefish Image

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Find a cuttlefish product:

mgrep "aosp_cf_x86_64_auto"

google/cuttlefish/AndroidProducts.mk:  aosp_cf_x86_64_auto-trunk_staging-userdebug
google/cuttlefish/AndroidProducts.mk:  aosp_cf_x86_64_auto_mdnd-trunk_staging-userdebug

1. Enable development environment:

   cd $AOSP_HOME/$AOSP_BRANCH
   source build/envsetup.sh

2. Select the target:

   lunch aosp_cf_x86_64_auto-trunk_staging-userdebug

3. Now, compile the target:

   m -j$(nproc)

   The image is located at out/target/product/vsoc_x86_64_only.

Some problems may happen:

• ccache is readonly → mount ccache to a different point:

  sudo mkdir -p /mnt/ccache
  sudo mount --bind ~/.ccache /mnt/ccache
  export USE_CCACHE=1
  export CCACHE_EXEC=/usr/bin/ccache
  export CCACHE_DIR=/mnt/ccache

• test is not found → exclude them from test list:

  nano platform_testing/build/tasks/tests/native_test_list.mk

  ifeq ($(BOARD_IS_AUTOMOTIVE), true)
  native_tests += \
      libwatchdog_test \
      evsmanagerd_test \
      #sv_2d_session_tests \
      #sv_3d_session_tests
  endif

• some random failures → lower the threads:
  such as from -j20 to -j10

Build Cuttlefish Device

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Refer: https://source.android.com/docs/devices/cuttlefish/get-started.

Verify KVM availability, this command should return a nonzero value:

grep -c -w "vmx\|svm" /proc/cpuinfo

1. Download support packages:

   sudo apt update
   sudo apt install devscripts equivs config-package-dev debhelper-compat golang

2. Download Cuttlefish source code:

   cd $AOSP_HOME
   git clone https://github.com/google/android-cuttlefish

3. Compile Cuttlefish packages:

   cd android-cuttlefish
   tools/buildutils/build_packages.sh

4. Install Cuttlefish packages:

   sudo dpkg -i ./cuttlefish-base_*_*64.deb || sudo apt-get install -f
   sudo dpkg -i ./cuttlefish-user_*_*64.deb || sudo apt-get install -f
   sudo usermod -aG kvm,cvdnetwork,render $USER

5. Finally, reboot system to apply changes, trigger installing additional kernel modules and applies udev rules.

   sudo reboot

Launch Cuttlefish

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1. Cuttlefish virtual device needs to know the built target’s artifacts to find required configs and images, so it always needs to enter the build environment:

   cd $AOSP_HOME/$AOSP_BRANCH
   source build/envsetup.sh
   lunch aosp_cf_x86_64_auto-trunk_staging-userdebug

2. Now run the emulator:

   launch_cvd --gpu_mode=gfxstream

   If want to a refresh run:

   launch_cvd --gpu_mode=gfxstream --resume=false

Cuttlefish launches with --start_webrtc, which enables a webview through port 8443 on the host machine.

Useful debugging information:

• Point browser to https://localhost:8443 to interact with the device.
• Serial console is disabled; use -console=true to enable it.
• Logcat output: ~/cuttlefish/instances/cvd-1/logs/logcat
• Kernel log: ~/cuttlefish/instances/cvd-1/kernel.log
• Launcher log: ~/cuttlefish/instances/cvd-1/logs/launcher.log
• Instance configuration: ~/cuttlefish/instances/cvd-1/cuttlefish_config.json
• Launcher Build ID: eng.trongv.20241007.012401

Android Platform Tools

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Android platform tools are provide in this package:

sudo apt install google-android-platform-tools-installer

Emulator can be accessed via adb as a normal Android device. For example, check the kernel version:

adb devices

List of devices attached
0.0.0.0:6520  device

adb shell

uname -a

Linux localhost 6.1.68-android14-11-ga7f647f49daf-ab11484633 #1 SMP PREEMPT Wed Feb 21 00:52:15 UTC 2024 x86_64 Toybox

The kernel version is correct for android14.

For stop, restart or reset the emulator:

• If device is responsive, perform a clean restart using adb reboot.
• If device is unresponsive, perform an unclean restart using restart_cvd.
• Reset the device state using powerwash_cvd.
• Stop the device and exit stop_cvd
• Stop the device and launch again with specifi flag launch_cvd --resume=false

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Below sections are for reference

Build Android Virtual Device

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Selected target: sdk_car_x86_64-trunk_staging-userdebug

Select -eng version may have shorter compilation time, but it may have some bugs on emulator, due to incompatibility of the engineering tools for virtual hardware.

Build AVD Target

Find an AVD SDK product:

mgrep "sdk_car_x86_64" --include=AndroidProducts.mk

./device/generic/car/AndroidProducts.mk:32:    sdk_car_x86_64-trunk_staging-userdebug \

1. Enter development environment

   cd $AOSP_HOME/$AOSP_BRANCH
   source build/envsetup.sh

2. Select the target:

   lunch sdk_car_x86_64-trunk_staging-userdebug

3. Now, compile the target:

   m -j$(nproc)

   The image is located at out/target/product/emulator_car64_x86_64.

Run AVD Emulator

Android Emulator is provided as a prebuilt tool in AOSP, located in prebuilts/android-emulator/linux-x86_64/emulator. Building Emulator requires to checkout then compile a different repo.

Run the emulator:

emulator -version

Emulator Command Line provides options to run an emulator. Basically, for development:

emulator -gpu host -selinux permissive -memory 8192 -writable-system -show-kernel -no-snapshot -wipe-data

Most used options:

• verbose: displays which files and settings are actually selected when starting
• shell: open the root shell
• show-kernel: option to show the kernel console, it’s good for debugging
• selinux {disabled|permissive}: SELinux will not be enforced
• gpu {host|guest}: use
• writable-system: system is writable so it can save user’s created files
• no-boot-anim: disable the boot animation
• no-snapshot: do not save system state
• wipe-data: remove all user data

Connect to he device shell, and check the kernel version:

uname -a

Linux localhost 6.6.9-android15-0-g515a956763d8-ab11275718 #1 SMP PREEMPT Thu Jan  4 21:38:14 UTC 2024 x86_64 Toybox

There is an error that the service bt* is created and killed repeatly.
It might happen because of wrong kernel version! It should be android14 for sdk_car_x86_64.
P/s: even using kernel in branch common-android14-6.1, the above issue still happens.

Build Trout Device

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Refer to: https://source.android.com/docs/automotive/virtualization/reference_platform

Through a new product named trout, Android Automotive now provides support for deployment as a guest virtual machine (VM) in environments compatible with the VirtIO standard. trout is based on the Cuttlefish virtual reference platform and is available as the trout device configuration, such as aosp_trout_x86_64-trunk_staging-userdebug.

However, at this time, trout target can not be built!