CODEWITHSUNDEEP
androidclassbytecodeloaderemulation
PhilPotter1987
PhilPotter1987

Reputation: 1316

How can I make Android load dynamically generated dalvik bytecode without writing to a file first?

For the past six months as my final university project, I've been writing a PlayStation 1 emulator in Java to prove it can be performant - part of my strategy involves writing a custom class loader that imports bytecode I have just generated from an array into a new class - in effect a Java bytecode dynarec core which speeds up the emulated CPU orders of magnitude (in theory). All quite possible on an Oracle JVM, and done before by others.

My question is, aside from the fact I would need to generate dalvik bytecode rather than Java bytecode, there doesn't seem to be anyway to dynamically load classes into a running Android app that doesn't involve loading them from a dex file on flash somewhere. I know similar things have been asked before, but as I would eventually like to port this emulator (and have it be quicker than its currently unplayable speed), is there anyway around this? I don't want to be continually writing to flash when a new section of MIPS code is converted to bytecode, as it could wear the flash out and probably isn't very fast either.

A thought I had was maybe mounting a tmpfs using a small JNI lib and storing class files there to be loaded, so in effect storing them in RAM as before - is this even possible for an unprivileged app to do though? I'd appreciate peoples input/thoughts.

Upvotes: 0

Views: 366

Answers (1)

Rafael Winterhalter
Rafael Winterhalter

Reputation: 43997

No, that might be possible on a jailbroken device but it's not possible in a sandboxed app.

I tried several ways to load dynamic code on Android but the only feasible way is via the DexClassLoader where the dex file must be stored in a privileged region.

You can have a look at my project Byte Buddy where I implemented such class loading: https://github.com/raphw/byte-buddy/blob/master/byte-buddy-android/src/main/java/net/bytebuddy/android/AndroidClassLoadingStrategy.java

Upvotes: 1

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