Automatic transformation of Android's dex code

Question

I want to transform/instrument Dex files. The goals of transformation include measuring code coverage. Note that the source files are not available. So instrumenting Dex is the only option.

I am wondering if there are any existing code base that I could look at as examples to write a tool to achieve my goal.

I know about the Smali project and a host of other projects that build on Smali. However, none of these projects are good examples for my purpose.

I am looking for code that automatically transforms smali code or the dexlib representation, from which smali is generated. The later option is preferred for my purpose because the overhead of generating smali can be avoided.

Answer 1

It's a lot of code, but dx's DexMerger is an example program that transforms dex files. It's made quite complicated by the fact that it needs to guess the size of the output in order make forward-references work.

You'd also need to create infrastructure to rewrite dalvik instructions. DexMerger's InstructionTransformer does a shallow rewrite: it adjusts offsets from one mapping to another. To measure code coverage your instruction rewriting would probably need to be much more sophisticated.