This repository contains code for an Android JVMTI agent that can be attached to an app in order to instrument it for AFL-style code coverage.
It consists of two portions, Java code in the runtime_java folder that gets called at runtime
when a basic block is hit.
The code to add this call is generated in runtime_cpp which is a JVMTI agent with a
ClassFileLoadHook that transforms dex files when they are loaded. In particular it adds a call
to Instrumentation.reachedBlock(blockId). It also adds the java code to the classpath so it can
be loaded by the app at runtime.
Normally you can build by importing the project into Android Studio and building. On the command line:
(Replace ANDROID_SDK_ROOT with your actual Android SDK folder)
set ANDROID_SDK_ROOT=%APPDATA%\Local\Android\Sdk
gradlew.bat assembleANDROID_SDK_ROOT=/path/to/sdk ./gradlew assembleThe deployer folder in this project contains a convenience application to push the CoverageAgent
to an Android device using adb.
gradle run --args="your.android.package.name"It will locate the app's data directory and push the coverage agent into the
DATA_DIR/code_cache/startup_agents directory.
It will also make all Android Runtimes on the phone debuggable by setting the
dalvik.vm.dex2oat-flags property to --debuggable. After this, you should be able to launch
the app while instrumenting coverage with:
am start-activity --attach-agent /path/to/libcoverage.so your.android.package.name/.app.MainActivityNote: this is probably wrong and not needed
If you are trying to instrument apps that don't have the android:debuggable attribute set and you
want to use the code_cache/startup_agents to attach it on every launch. You must ensure
you have root access on the device and ro.debuggable is set. The deployer can toggle the
debuggable bit in the system process. Firstly, ensure that
setprop persist.debug.dalvik.vm.jdwp.enabled 1is set and restart the device after setting this property.
Next, invoke the deployer with the --force-debuggable to have it deploy the coverage agent and
flip the debug bit for you.
gradle run --args="your.android.package.name --force-debuggable"
