In this dissertation project a novel exploration of the decompilation of Java Intermediate Representation is undertaken, employing the Neural Machine Translation technique Encoder-Decoder with attention in order to approach the decompilation problem as a translation between two different languages. More specifically, this project seeks to address the question of whether a Java decompiler based on Neural Machine Translation techniques is a theoretically, practically, and economically viable solution. Through the use of a software pipeline that combines a greenfield tool with open-source libraries and tool kits, Java bytecode code-snippets are extracted from a corpus of Java libraries and successfully decompiled to Java source-code. Experimental results, analysed using Machine Translation evaluation metrics, show that these are very similar to the ground truth. The contributions of this project demonstrate that the technical framework developed is a strong and promising candidate for future Java decompilers.
The pipeline developed in this dissertation project is composed by:
- A Java software able to extract translation pairs from a corpus of libraries (downloaded from Maven)
- Through the use of OpenNMT, an Encoder-Decoder with attention neural model is trained and then used to decompile bytecode methods
- The Asiya framework is used to assess the performance of the neural model
To use the Java software written for this dissertation project, run the following commands:
git clone https://github.com/manuNCL/JavaNeuralDecompiler.git
cd JavaNeuralDecompiler/utilityFiles
and then
mvn -f small-corpus.xml -DoutputDirectory=data/binjars dependency:copy-dependencies [OR mvn -f large-corpus.xml -DoutputDirectory=data/binjars dependency:copy-dependencies]
mvn -f small-corpus.xml -DoutputDirectory=data/srcjars -Dclassifier=sources dependency:copy-dependencies [OR mvn -f large-corpus.xml -DoutputDirectory=data/srcjars -Dclassifier=sources dependency:copy-dependencies]
The file small-corpus.xml can be substituted with the other xml file large-corpus.xml if more translation pairs are needed.
To execute the Java software and extract translation pairs, run the command:
mvn exec:java -Dexec.mainClass=com.redhat.jhalliday.Driver
The complete chain of commands to create the dataset and run the Java software are reported in UtilityFiles/CreateDataset
Before using the OpenNMT framework, the dataset composed by the translation pairs must be divided to create three datasets, which are used to train, validate and test the neural model. To do so, it is possible to use the python script createDatasets.py available in the folder UtilityFiles. It is also possible to run the python script analyseDataset.py to visualise the distribution of translation pairs in function of their (low-level) length.
This framework is used to train a neural model, which is then used to decompile translation pairs. To train the neural model, run the following commands:
onmt_preprocess -train_src ./datasets/x_train -train_tgt ./datasets/y_train -valid_src ./datasets/x_valid -valid_tgt ./datasets/y_valid -save_data ./models/experiment --src_vocab_size 250000 --tgt_vocab_size 250000 --src_seq_length 20000 --tgt_seq_length 20000 --log_file ~/datasets/preprocess_logs
CUDA_VISIBLE_DEVICES=0 onmt_train -early_stopping 4 -data ./models/experiment -save_model ./models/experimentTrainedModel -world_size 1 -gpu_ranks 0 -log_file ~/datasets/training_logs
Once the neural model is ready, the translation process can be lunched with the command:
CUDA_VISIBLE_DEVICES=0 onmt_translate -gpu 0 -model ./models/experimentTrainedModel_step_60000.pt -src ~/datasets/remaining_sources -tgt ~/datasets/remaining_references -output ~/datasets/remaining_candidates
In the guide located in UtilityFiles/OperationsToReproduceExperiments, the process to install and use OpenNMT is reported. Please, refer to it.
To work out the metrics used in this dissertation project, two tools can be used: ASIYA and the available metrics in OpenNMT. Using the latter, the evaluation of results is very easy:
th tools/score.lua ~/datasets/remaining_references -scorer ter < ~/datasets/remaining_candidates
th tools/score.lua ~/datasets/remaining_references -scorer dlratio < ~/datasets/remaining_candidates
NOTE: TensorFlow must be installed!
In case you want to use ASIYA, it is best to refer to the installation and user guide located in the file UtilityFiles/asiya_installation