Appendix A: Key Files Reference

This appendix is a quick-reference table of the most important source files in AOSP. The tables group the files by subsystem. Each heading gives the chapter where the files are discussed. Paths are relative to the AOSP root ($AOSP/).

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Build System (Chapter 2)

File Path	Purpose
build/make/core/main.mk	Top-level build entry point; includes all other makefiles
build/make/core/Makefile	Legacy build rules for images, OTA, packaging
build/make/core/definitions.mk	Common macro definitions used across the build
build/make/core/envsetup.mk	Environment variable setup for build configuration
build/make/core/product.mk	Product-level build variable definitions
build/make/core/product_config.mk	Product configuration loading and validation
build/make/core/board_config.mk	Board-level hardware configuration
build/make/core/binary.mk	Shared rules for building native binaries
frameworks/libs/binary_translation/berberis_config.mk	Berberis (riscv64-to-x86_64) product-package configuration for native bridge
build/make/envsetup.sh	Shell environment setup; defines lunch (plus tapas, banchan, croot) and puts build/soong/bin -- home of the standalone m, mm, mmm scripts -- on PATH
build/soong/cmd/soong_build/main.go	Soong build system entry point
build/soong/android/module.go	Base module type definitions for Soong
build/soong/android/androidmk.go	Emits Android.mk entries for Soong modules so Kati can consume them (Make-Soong interoperability)
build/soong/cc/cc.go	C/C++ module build rules for Soong
build/soong/cc/library.go	Shared/static library build rules
build/soong/cc/binary.go	Native binary build rules
build/soong/cc/config/riscv64_device.go	RISC-V 64-bit device configuration
build/soong/java/java.go	Java module build rules for Soong
build/soong/java/app.go	Android application build rules
build/soong/apex/apex.go	APEX module build rules
build/blueprint/context.go	Blueprint core context and dependency resolution
build/blueprint/module_ctx.go	Module context interface for Blueprint
device/generic/goldfish/board/BoardConfigCommon.mk	Emulator board configuration (common)
device/google/cuttlefish/vsoc_x86_64/BoardConfig.mk	Cuttlefish virtual device board config (x86_64)

Boot and Init (Chapter 4)

File Path	Purpose
system/core/init/init.cpp	PID-1 init process main entry point
system/core/init/service.cpp	Service lifecycle management (start/stop/restart)
system/core/init/service_parser.cpp	Parsing of service definitions in .rc files
system/core/init/action.cpp	Action and trigger execution engine
system/core/init/action_parser.cpp	Parsing of action blocks in .rc files
system/core/init/property_service.cpp	System property daemon and persistence
system/core/init/first_stage_init.cpp	First-stage init before mounting partitions
system/core/init/first_stage_mount.cpp	Early partition mounting logic
system/core/init/selinux.cpp	SELinux policy loading during init
system/core/init/ueventd.cpp	Device node creation daemon
system/core/init/reboot.cpp	Shutdown and reboot sequencing
system/core/rootdir/init.rc	Root init script; defines core services and triggers
system/core/rootdir/init.zygote64_32.rc	Zygote startup configuration (64+32-bit)
system/core/fastboot/fastboot.cpp	Fastboot protocol host-side implementation
bootable/recovery/recovery.cpp	Recovery mode main entry point

Kernel (Chapter 5)

Unlike the rest of this appendix, these paths are relative to a separate Android Common Kernel checkout (its own repo init). In that checkout, the kernel source tree is common/ and the build tooling is build/. The platform checkout's kernel/ directory holds only configs, prebuilts, and tests.

File Path	Purpose
common/Makefile	Top-level kernel Makefile
common/arch/arm64/configs/gki_defconfig	GKI default kernel configuration
common/drivers/android/binder.c	Binder kernel driver implementation
common/drivers/android/binder_alloc.c	Binder memory allocation
common/drivers/staging/android/ion/	ION memory allocator (legacy)
common/drivers/dma-buf/	DMA-BUF framework for buffer sharing
common/drivers/gpu/drm/	DRM/KMS graphics driver framework
common/include/uapi/linux/android/binder.h	Binder UAPI header
common/fs/fuse/dev.c	FUSE device implementation (for scoped storage)
build/build.sh	Kernel build wrapper script (legacy)
build/kleaf/	Kleaf (Bazel-based) kernel build system

Bionic and the Dynamic Linker (Chapter 7)

File Path	Purpose
bionic/libc/bionic/malloc_common.cpp	malloc dispatch (jemalloc/scudo selection)
bionic/libc/bionic/pthread_create.cpp	POSIX thread creation
bionic/libc/bionic/libc_init_dynamic.cpp	Dynamic-linked process startup
bionic/libc/bionic/libc_init_static.cpp	Static-linked process startup
bionic/libc/bionic/system_property_api.cpp	System property client API
bionic/libc/arch-arm64/	ARM64 architecture-specific code
bionic/libc/include/	Public C library headers
bionic/linker/linker.cpp	Dynamic linker main logic
bionic/linker/linker_phdr.cpp	ELF program header parsing and loading
bionic/linker/linker_namespaces.cpp	Linker namespace implementation
bionic/linker/linker_soinfo.cpp	Shared object info management
bionic/linker/linker_config.cpp	Linker configuration file parsing
system/core/rootdir/etc/ld.config.txt	Default linker namespace configuration
bionic/libm/	Math library implementation
bionic/libdl/libdl.cpp	dlopen/dlsym implementation

Binder IPC (Chapter 9)

File Path	Purpose
frameworks/native/libs/binder/IPCThreadState.cpp	Per-thread Binder transaction processing
frameworks/native/libs/binder/ProcessState.cpp	Per-process Binder driver state
frameworks/native/libs/binder/Binder.cpp	BBinder (local) base class
frameworks/native/libs/binder/BpBinder.cpp	BpBinder (proxy) base class
frameworks/native/libs/binder/Parcel.cpp	Data serialization for Binder transactions
frameworks/native/libs/binder/IServiceManager.cpp	Service manager client interface
frameworks/native/cmds/servicemanager/ServiceManager.cpp	Service manager daemon
frameworks/native/cmds/servicemanager/main.cpp	Service manager entry point
frameworks/base/core/java/android/os/Binder.java	Java-side Binder base class
frameworks/base/core/java/android/os/BinderProxy.java	Java-side Binder proxy
frameworks/base/core/java/android/os/Parcel.java	Java-side Parcel
frameworks/base/core/java/android/os/ServiceManager.java	Java service manager client
frameworks/base/core/jni/android_util_Binder.cpp	Binder JNI bridge

HAL -- Hardware Abstraction Layer (Chapter 10)

File Path	Purpose
hardware/interfaces/	Top-level HIDL/AIDL HAL interface directory
hardware/interfaces/audio/aidl/	Audio HAL AIDL interface definitions
hardware/interfaces/camera/provider/aidl/	Camera provider HAL interface
hardware/interfaces/graphics/composer/aidl/	HWC (Hardware Composer) HAL interface
hardware/interfaces/graphics/allocator/aidl/	Gralloc allocator HAL interface
hardware/interfaces/graphics/mapper/stable-c/	Gralloc mapper stable-C HAL interface
hardware/interfaces/health/aidl/	Battery/health HAL interface
hardware/interfaces/sensors/aidl/	Sensors HAL interface
hardware/interfaces/neuralnetworks/aidl/	NNAPI HAL interface
hardware/interfaces/power/aidl/	Power HAL interface
hardware/interfaces/thermal/aidl/	Thermal HAL interface
hardware/interfaces/bluetooth/aidl/	Bluetooth HAL interface
hardware/interfaces/wifi/aidl/	Wi-Fi HAL interface
hardware/interfaces/vibrator/aidl/	Vibrator HAL interface
hardware/libhardware/include/hardware/hardware.h	Legacy HAL module interface (hw_module_t)
system/libhidl/transport/HidlTransportSupport.cpp	HIDL transport initialization
system/tools/hidl/	HIDL compiler (hidl-gen)
system/tools/aidl/	AIDL compiler for HAL interfaces

NDK -- Native Development Kit (Chapter 11)

File Path	Purpose
frameworks/native/include/android/	Public NDK native headers
frameworks/native/libs/nativewindow/include/android/native_window.h	ANativeWindow API
frameworks/native/include/android/native_activity.h	NativeActivity API
frameworks/native/include/android/sensor.h	Sensor NDK API
frameworks/native/include/android/asset_manager.h	Asset manager NDK API
frameworks/av/media/ndk/	Media NDK implementation (AMediaCodec, etc.)
packages/modules/NeuralNetworks/runtime/	NNAPI runtime implementation
frameworks/native/libs/nativewindow/	ANativeWindow implementation

Native Services (Chapter 12)

File Path	Purpose
frameworks/native/services/inputflinger/dispatcher/InputDispatcher.cpp	Input event dispatch to windows
frameworks/native/services/inputflinger/reader/InputReader.cpp	Input device event reading
frameworks/native/services/inputflinger/InputManager.cpp	Input subsystem coordinator
frameworks/native/services/sensorservice/SensorService.cpp	Sensor event multiplexing
frameworks/native/services/surfaceflinger/main_surfaceflinger.cpp	SurfaceFlinger process entry point
system/logging/logd/SerializedLogBuffer.cpp	System log ring buffer
system/memory/lmkd/lmkd.cpp	Low memory killer daemon
system/memory/lmkd/	Modern LMKD implementation
system/core/healthd/	Battery/health daemon
system/netd/server/NetdNativeService.cpp	Network daemon native service

Graphics and Render Pipeline (Chapter 13)

File Path	Purpose
frameworks/native/services/surfaceflinger/SurfaceFlinger.cpp	Compositor main class
frameworks/native/services/surfaceflinger/SurfaceFlinger.h	SurfaceFlinger declarations
frameworks/native/services/surfaceflinger/Scheduler/Scheduler.cpp	VSYNC scheduling and frame pacing
frameworks/native/services/surfaceflinger/Scheduler/VSyncReactor.cpp	VSYNC controller implementation (VsyncController interface in VsyncController.h)
frameworks/native/services/surfaceflinger/CompositionEngine/	Composition strategy engine
frameworks/native/services/surfaceflinger/DisplayHardware/HWComposer.cpp	HWC abstraction layer
frameworks/native/services/surfaceflinger/PowerAdvisor/PowerAdvisor.cpp	Power hint integration
frameworks/native/services/surfaceflinger/Layer.cpp	Individual surface/layer management
frameworks/native/services/surfaceflinger/FrontEnd/LayerSnapshot.cpp	Buffer-backed layer state snapshot (frontend)
frameworks/native/services/surfaceflinger/FrontEnd/LayerLifecycleManager.cpp	Layer lifecycle tracking
frameworks/native/services/surfaceflinger/Tracing/TransactionTracing.cpp	Transaction trace capture
frameworks/native/libs/gui/Surface.cpp	Client-side Surface implementation
frameworks/native/libs/gui/BufferQueue.cpp	Producer-consumer buffer queue
frameworks/native/libs/gui/BufferQueueProducer.cpp	Buffer queue producer side
frameworks/native/libs/gui/BufferQueueConsumer.cpp	Buffer queue consumer side
frameworks/native/libs/gui/SurfaceComposerClient.cpp	SurfaceFlinger client interface
frameworks/native/libs/gui/BLASTBufferQueue.cpp	BLAST buffer queue (modern path)
frameworks/native/libs/renderengine/skia/SkiaGLRenderEngine.cpp	Skia-based GPU composition
frameworks/native/libs/renderengine/skia/SkiaVkRenderEngine.cpp	Skia Vulkan render engine
frameworks/native/opengl/libs/EGL/eglApi.cpp	EGL API entry points
frameworks/native/opengl/libs/EGL/Loader.cpp	EGL driver loader
frameworks/native/vulkan/libvulkan/driver.cpp	Vulkan loader/driver interface
frameworks/native/vulkan/libvulkan/api.cpp	Vulkan API dispatch
external/skia/src/gpu/ganesh/GrDirectContext.cpp	Skia GPU context
external/skia/src/gpu/graphite/	Skia Graphite (next-gen GPU backend)
frameworks/base/libs/hwui/renderthread/RenderThread.cpp	HWUI render thread
frameworks/base/libs/hwui/renderthread/CanvasContext.cpp	Per-window render context
frameworks/base/libs/hwui/pipeline/skia/SkiaOpenGLPipeline.cpp	Skia GL rendering pipeline
frameworks/base/libs/hwui/pipeline/skia/SkiaVulkanPipeline.cpp	Skia Vulkan rendering pipeline
frameworks/base/libs/hwui/RenderNode.cpp	Display list render node
frameworks/base/libs/hwui/RecordingCanvas.cpp	Display list recording canvas
frameworks/base/libs/hwui/DamageAccumulator.cpp	Dirty region tracking
frameworks/base/libs/hwui/JankTracker.cpp	Frame jank detection and reporting
frameworks/base/graphics/java/android/graphics/Canvas.java	Java Canvas API
frameworks/base/graphics/java/android/graphics/RenderNode.java	Java RenderNode API
frameworks/base/core/java/android/view/Choreographer.java	VSYNC-based callback scheduler
frameworks/base/core/java/android/view/ViewRootImpl.java	View hierarchy root; drives measure/layout/draw
frameworks/base/core/java/android/view/ThreadedRenderer.java	Java bridge to HWUI RenderThread

Animation System (Chapter 14)

File Path	Purpose
frameworks/base/core/java/android/animation/ValueAnimator.java	Core property animation engine
frameworks/base/core/java/android/animation/ObjectAnimator.java	Property-targeted animation
frameworks/base/core/java/android/animation/AnimatorSet.java	Coordinated animation sequencing
frameworks/base/core/java/android/view/animation/Animation.java	Legacy view animation base class
frameworks/base/core/java/android/transition/TransitionManager.java	Scene transition framework
frameworks/base/core/java/android/window/TransitionInfo.java	Shell transition metadata
frameworks/libs/systemui/animationlib/src/	SystemUI shared animation library

Audio System (Chapter 15)

File Path	Purpose
frameworks/av/services/audioflinger/AudioFlinger.cpp	Audio mixing daemon main class
frameworks/av/services/audioflinger/Threads.cpp	Playback and record thread implementations
frameworks/av/services/audioflinger/Tracks.cpp	Audio track management
frameworks/av/services/audioflinger/Effects.cpp	Audio effects chain processing
frameworks/av/services/audiopolicy/managerdefault/AudioPolicyManager.cpp	Audio routing policy
frameworks/av/services/audiopolicy/common/managerdefinitions/src/PolicyAudioPort.cpp	Audio port abstraction
frameworks/av/media/libaudioclient/AudioTrack.cpp	Client-side audio playback
frameworks/av/media/libaudioclient/AudioRecord.cpp	Client-side audio recording
frameworks/av/media/libaudioclient/AudioSystem.cpp	Audio system client interface
frameworks/av/media/libaudiohal/impl/DeviceHalAidl.cpp	Audio device HAL AIDL adapter
frameworks/base/media/java/android/media/AudioTrack.java	Java audio playback API
frameworks/base/services/core/java/com/android/server/audio/AudioService.java	Audio service (volume, routing)

Media and Video Pipeline (Chapter 16)

File Path	Purpose
frameworks/av/media/libmediaplayerservice/MediaPlayerService.cpp	Media player daemon
frameworks/av/media/codec2/sfplugin/CCodec.cpp	Codec2 framework plugin
frameworks/av/media/codec2/sfplugin/CCodecBufferChannel.cpp	Codec2 buffer management
frameworks/av/media/codec2/components/	Software codec implementations
frameworks/av/media/libstagefright/MediaCodec.cpp	MediaCodec native implementation
frameworks/av/media/libstagefright/ACodec.cpp	Legacy OMX codec adapter
frameworks/av/media/libmediaplayerservice/nuplayer/NuPlayer.cpp	Media playback engine
frameworks/av/media/module/extractors/	Media file format extractors (MP4, MKV, etc.)
frameworks/av/services/camera/libcameraservice/CameraService.cpp	Camera service daemon
frameworks/av/drm/mediadrm/plugins/clearkey/	ClearKey DRM reference implementation
frameworks/base/media/java/android/media/MediaCodec.java	Java MediaCodec API
frameworks/base/media/java/android/media/MediaPlayer.java	Java MediaPlayer API

ART Runtime (Chapter 18)

File Path	Purpose
art/runtime/runtime.cc	ART runtime initialization
art/runtime/class_linker.cc	Class loading and linking
art/runtime/interpreter/interpreter.cc	Bytecode interpreter entry point
art/runtime/jit/jit.cc	JIT compiler coordinator
art/runtime/jit/jit_code_cache.cc	JIT compiled code cache
art/runtime/gc/heap.cc	Garbage collector heap management
art/runtime/gc/collector/concurrent_copying.cc	Concurrent copying GC
art/runtime/thread.cc	Thread management
art/runtime/oat/oat_file.cc	OAT file format handling
art/runtime/mirror/object.h	Root object type for managed heap
art/runtime/mirror/class.h	Class metadata representation
art/compiler/optimizing/optimizing_compiler.cc	AOT/JIT optimizing compiler
art/compiler/optimizing/code_generator_arm64.cc	ARM64 code generation backend
art/compiler/optimizing/register_allocator_linear_scan.cc	Register allocation
art/dex2oat/dex2oat.cc	Ahead-of-time compilation tool
art/dex2oat/dex2oat_options.cc	DEX-to-OAT compilation options
art/libdexfile/dex/dex_file.h	DEX file format definitions
art/runtime/native_bridge_art_interface.cc	ART-side native bridge integration

Native Bridge and Binary Translation (Chapter 19)

File Path	Purpose
frameworks/libs/binary_translation/native_bridge/native_bridge.h	NativeBridgeCallbacks interface (v3-v8)
frameworks/libs/binary_translation/native_bridge/native_bridge.cc	Native bridge framework implementation
frameworks/libs/binary_translation/guest_loader/	Guest library loading and linking
frameworks/libs/binary_translation/guest_abi/	ABI conversion between host and guest
frameworks/libs/binary_translation/guest_state/	Guest CPU state abstraction
frameworks/libs/binary_translation/jni/	JNI trampoline generation
frameworks/libs/binary_translation/cpu_emulation/interpreter/	Guest instruction interpreter
frameworks/libs/binary_translation/cpu_emulation/decoder/	Guest instruction decoder
frameworks/libs/binary_translation/cpu_emulation/backend/	Host code generation backend
frameworks/libs/binary_translation/cpu_emulation/assembler/	Host instruction assembler
frameworks/libs/binary_translation/android_api/	Android framework proxy stubs
frameworks/libs/native_bridge_support/native_bridge_support.mk	Build synchronization for bridge support
art/libnativebridge/native_bridge.cc	System-side native bridge loading

system_server (Chapter 20)

File Path	Purpose
frameworks/base/services/java/com/android/server/SystemServer.java	system_server boot sequence
frameworks/base/services/core/java/com/android/server/SystemServiceManager.java	Service lifecycle manager
frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java	Activity Manager Service
frameworks/base/services/core/java/com/android/server/wm/WindowManagerService.java	Window Manager Service
frameworks/base/services/core/java/com/android/server/wm/ActivityTaskManagerService.java	Activity Task Manager Service
frameworks/base/services/core/java/com/android/server/pm/PackageManagerService.java	Package Manager Service
frameworks/base/services/core/java/com/android/server/power/PowerManagerService.java	Power management
frameworks/base/services/core/java/com/android/server/display/DisplayManagerService.java	Display management
frameworks/base/services/core/java/com/android/server/input/InputManagerService.java	Input management bridge
frameworks/base/core/java/com/android/internal/os/ZygoteInit.java	Zygote process initialization
frameworks/base/core/java/com/android/internal/os/ZygoteConnection.java	Zygote fork request handling
frameworks/base/core/java/com/android/internal/os/Zygote.java	Zygote fork mechanics
frameworks/base/core/java/com/android/internal/os/RuntimeInit.java	App process runtime initialization

Activity and Window Management (Chapter 22)

File Path	Purpose
frameworks/base/services/core/java/com/android/server/wm/Task.java	Task (back stack) container
frameworks/base/services/core/java/com/android/server/wm/ActivityRecord.java	Per-activity state tracking
frameworks/base/services/core/java/com/android/server/wm/ActivityStarter.java	Intent resolution and activity start
frameworks/base/services/core/java/com/android/server/wm/ActivityClientController.java	Activity lifecycle IPC handler
frameworks/base/services/core/java/com/android/server/wm/RootWindowContainer.java	Root of the window hierarchy
frameworks/base/services/core/java/com/android/server/wm/TaskFragment.java	Activity embedding container
frameworks/base/core/java/android/app/Activity.java	Application-side activity base class
frameworks/base/core/java/android/app/ActivityThread.java	Main thread of every Android app
frameworks/base/core/java/android/app/Instrumentation.java	Activity lifecycle instrumentation hooks

Window System (Chapter 23)

File Path	Purpose
frameworks/base/services/core/java/com/android/server/wm/WindowState.java	Per-window server state
frameworks/base/services/core/java/com/android/server/wm/WindowToken.java	Window grouping token
frameworks/base/services/core/java/com/android/server/wm/Session.java	Per-app WMS session
frameworks/base/services/core/java/com/android/server/wm/WindowStateAnimator.java	Window-to-Surface bridge; creates and manages the window's SurfaceControl
frameworks/base/services/core/java/com/android/server/wm/WindowAnimator.java	Window animation coordinator
frameworks/base/services/core/java/com/android/server/wm/InsetsStateController.java	System insets management
frameworks/base/services/core/java/com/android/server/wm/InsetsPolicy.java	Insets visibility policy
frameworks/base/core/java/android/view/WindowManager.java	Client window manager interface
frameworks/base/core/java/android/view/WindowManagerImpl.java	Window manager implementation
frameworks/base/core/java/android/view/View.java	Base UI component (measure/layout/draw)
frameworks/base/core/java/android/view/ViewGroup.java	Container for child views
frameworks/base/core/java/android/view/SurfaceView.java	Separate-surface view component

Display System (Chapter 24)

File Path	Purpose
frameworks/base/services/core/java/com/android/server/wm/DisplayContent.java	Per-display window container
frameworks/base/services/core/java/com/android/server/wm/DisplayPolicy.java	Per-display window policy (bars, cutouts)
frameworks/base/services/core/java/com/android/server/wm/DisplayRotation.java	Display rotation handling
frameworks/base/services/core/java/com/android/server/display/LogicalDisplay.java	Logical display abstraction
frameworks/base/services/core/java/com/android/server/display/DisplayDeviceInfo.java	Physical display properties
frameworks/base/services/core/java/com/android/server/display/LocalDisplayAdapter.java	Built-in display adapter

PackageManagerService (Chapter 26)

File Path	Purpose
frameworks/base/services/core/java/com/android/server/pm/PackageManagerService.java	Package management core
frameworks/base/services/core/java/com/android/server/pm/Settings.java	Package settings persistence
frameworks/base/services/core/java/com/android/server/pm/InstallPackageHelper.java	Package installation logic
frameworks/base/services/core/java/com/android/server/pm/PackageInstallerService.java	Installer session management
frameworks/base/services/core/java/com/android/server/pm/permission/PermissionManagerService.java	Runtime permission management
frameworks/base/core/java/com/android/internal/pm/pkg/parsing/ParsingPackageUtils.java	APK manifest parsing
frameworks/base/services/core/java/com/android/server/pm/resolution/ComponentResolver.java	Intent filter resolution
frameworks/base/services/core/java/com/android/server/pm/dex/ArtManagerService.java	ART profile and DEX optimization service
frameworks/base/core/java/android/content/pm/PackageManager.java	Public PackageManager API

Security (Chapter 40)

File Path	Purpose
system/sepolicy/public/	Public SELinux policy definitions
system/sepolicy/private/	Private (platform) SELinux policy
system/sepolicy/vendor/	Vendor SELinux policy
system/security/keystore2/	Keystore2 service (Rust)
system/security/identity/	Identity credential service
external/selinux/	SELinux userspace tools
system/extras/verity/	dm-verity tools
system/fs/fs_mgr/libfs_avb/	AVB (Android Verified Boot) integration
frameworks/base/services/core/java/com/android/server/biometrics/	Biometric authentication
frameworks/base/keystore/java/android/security/keystore2/	Keystore Java API

SystemUI (Chapter 48)

File Path	Purpose
frameworks/base/packages/SystemUI/src/com/android/systemui/application/SystemUIApplication.kt	SystemUI application entry
frameworks/base/packages/SystemUI/src/com/android/systemui/statusbar/phone/CentralSurfacesImpl.java	Status bar + notification shade
frameworks/base/packages/SystemUI/src/com/android/systemui/qs/panels/domain/startable/QSPanelsCoreStartable.kt	Quick Settings panels startup coordinator
frameworks/base/packages/SystemUI/src/com/android/systemui/recents/OverviewProxyRecentsImpl.java	Recents/overview proxy to Launcher
frameworks/base/packages/SystemUI/src/com/android/systemui/keyguard/KeyguardViewMediator.java	Lock screen coordinator
frameworks/base/packages/SystemUI/src/com/android/systemui/navigationbar/views/NavigationBar.java	Navigation bar
frameworks/base/packages/SystemUI/src/com/android/systemui/volume/VolumeDialogControllerImpl.java	Volume dialog logic
frameworks/base/packages/SystemUI/src/com/android/systemui/shade/NotificationPanelViewController.java	Notification panel controller

Launcher3 (Chapter 49)

File Path	Purpose
packages/apps/Launcher3/src/com/android/launcher3/Launcher.java	Main Launcher activity
packages/apps/Launcher3/src/com/android/launcher3/Workspace.java	Home screen workspace
packages/apps/Launcher3/src/com/android/launcher3/allapps/ActivityAllAppsContainerView.java	All-apps drawer
packages/apps/Launcher3/src/com/android/launcher3/model/LoaderTask.java	App list loading
packages/apps/Launcher3/src/com/android/launcher3/dragndrop/DragController.java	Drag-and-drop coordinator
packages/apps/Launcher3/quickstep/src/com/android/quickstep/RecentsActivity.java	Recents (overview) activity
packages/apps/Launcher3/quickstep/src/com/android/quickstep/TouchInteractionService.kt	Gesture navigation service

Settings App (Chapter 50)

File Path	Purpose
packages/apps/Settings/src/com/android/settings/Settings.java	Main Settings activity
packages/apps/Settings/src/com/android/settings/dashboard/DashboardFragment.java	Preference dashboard base
packages/apps/Settings/src/com/android/settings/search/SearchFeatureProvider.java	Settings search
packages/apps/Settings/src/com/android/settings/biometrics/	Biometrics enrollment

CompanionDeviceManager and Virtual Devices (Chapter 52)

File Path	Purpose
frameworks/base/services/companion/java/com/android/server/companion/CompanionDeviceManagerService.java	CDM service
frameworks/base/services/companion/java/com/android/server/companion/virtual/VirtualDeviceManagerService.java	VDM service

Mainline Modules (Chapter 54)

File Path	Purpose
packages/modules/Wifi/	Wi-Fi Mainline module
packages/modules/Bluetooth/	Bluetooth Mainline module
packages/modules/NetworkStack/	Network stack Mainline module
packages/modules/Permission/	Permission controller module
packages/providers/MediaProvider/	Media storage provider module
packages/modules/adb/	ADB Mainline module
packages/modules/common/	Shared Mainline module infrastructure
system/apex/apexd/	APEX daemon (module installer)
system/apex/apexd/apexd.cpp	APEX installation and activation
system/apex/libs/libapexutil/	APEX utility library

Virtualization Framework (Chapter 56)

File Path	Purpose
packages/modules/Virtualization/	Android Virtualization Framework top-level
packages/modules/Virtualization/android/virtualizationservice/	VM lifecycle management
packages/modules/Virtualization/build/microdroid/	Minimal guest OS (Microdroid) build files
packages/modules/Virtualization/guest/pvmfw/	Protected VM firmware
packages/modules/Virtualization/libs/libvm_payload/	Guest payload interface

Testing (Chapter 57)

File Path	Purpose
test/vts/	Vendor Test Suite top-level
cts/tests/	Compatibility Test Suite tests
tools/tradefederation/core/	Trade Federation test harness core
tools/tradefederation/core/src/com/android/tradefed/	TradeFed framework classes
platform_testing/tests/	Platform integration tests
frameworks/base/core/tests/	Framework core unit tests
frameworks/base/test-runner/	Android test runner framework

Architecture Support (Chapter 59)

File Path	Purpose
build/soong/cc/config/arm64_device.go	ARM64 toolchain: arch variants, CPU tuning, PAC/BTI
build/soong/cc/config/arm_device.go	ARM 32-bit toolchain: Thumb/ARM, errata workarounds
build/soong/cc/config/x86_device.go	x86 32-bit toolchain: SSE, stack realignment
build/soong/cc/config/x86_64_device.go	x86_64 toolchain: microarchitecture variants
build/soong/cc/config/riscv64_device.go	RISC-V 64-bit toolchain: ISA extensions
build/soong/cc/config/toolchain.go	Toolchain interface and factory registry
build/soong/cc/config/global.go	Global compiler/linker flags for all architectures
build/soong/cc/config/bionic.go	Bionic CRT objects and default shared libraries
build/soong/cc/config/clang.go	Clang unknown-flags filter
build/soong/android/arch.go	Arch struct, ArchType, multilib decode logic
bionic/libc/arch-arm64/ifuncs.cpp	ARM64 ifunc dispatchers (MTE variant selection; SVE variants present but not yet enabled)
art/runtime/arch/riscv64/instruction_set_features_riscv64.h	ART RISC-V feature detection
art/runtime/arch/arm64/instruction_set_features_arm64.h	ART ARM64 feature bitmap and errata

Emulator (Chapter 60)

File Path	Purpose
external/qemu/android-qemu2-glue/emulation/	Glue between QEMU and the android-emu emulation layer
external/qemu/android/android-emu/android/emulation/	Emulator hardware emulation
device/generic/goldfish/	Goldfish virtual device definitions
device/google/cuttlefish/	Cuttlefish virtual device definitions
device/google/cuttlefish/host/commands/run_cvd/	Cuttlefish launcher
external/crosvm/	CrosVM virtual machine monitor
external/qemu/android/android-grpc/	Emulator gRPC control interface

Device Form Factors (Chapter 62)

File Path	Purpose
packages/services/Car/	Android Automotive service layer
packages/services/Car/service/src/com/android/car/CarServiceImpl.java	Automotive car service
packages/apps/Car/Launcher/	Automotive launcher
device/google/atv/	Android TV device configuration
packages/apps/TvSettings/	TV settings application
prebuilts/sdk/opt/wear/	Wear OS SDK prebuilts

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Note: Paths may shift between AOSP branches. The paths above target AOSP main as of early 2026. Use find or cs.android.com to verify against your checked-out branch.