dumpcoverage

libdumpcoverage.so is a JVMTI agent designed to dump coverage information for a process, where the binaries have been instrumented by JaCoCo. JaCoCo automatically starts recording data on process start, and we need a way to trigger the resetting or dumping of this data.

The JVMTI agent is used to make the calls to JaCoCo in its process.

Usage

Note that these examples assume you have an instrumented build (userdebug_coverage). Here is, for example, how to dump coverage information regarding the default clock app. First some setup is necessary:

adb root # necessary to copy files in/out of the /data/data/{package} folder
adb shell 'mkdir /data/data/com.android.deskclock/folder-to-use'

Then we can run the command to dump the data:

adb shell 'am attach-agent com.android.deskclock /system/lib/libdumpcoverage.so=dump:/data/data/com.android.deskclock/folder-to-use/coverage-file.ec'

We can also reset the coverage information with

adb shell 'am attach-agent com.android.deskclock /system/lib/libdumpcoverage.so=reset'

then perform more actions, then dump the data again. To get the files, we can get

adb pull /data/data/com.android.deskclock/folder-to-use/coverage-file.ec ~/path-on-your-computer

And you should have coverage-file.ec on your machine under the folder ~/path-on-your-computer

Details

In dump mode, the agent makes JNI calls equivalent to

Agent.getInstance().getExecutionData(/*reset = */ false);

and then saves the result to a file specified by the passed in directory

In reset mode, it makes a JNI call equivalent to

Agent.getInstance().reset();