Jssembly is a library that allows you to execute native assembly from Java.
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Jssembly is a library that allows you to execute native assembly from Java via a JNI bridge. The goal is to provide wrappers and parsers for Windows/*NIX/OSX/Android. Most of the work currently consists of writing ANTLR parsers for

  • x86 assembly
  • amd64 assembly
  • ARMv7/v8 assembly

However, with great power comes great responsibility.

WARNING: Jssembly can (and will) crash your VM if you don't know what you're doing. The current pre-alpha state is in no way meant to be used in production code. You have been warned.


Jssembly emulates __asm syntax found in Visual Studio or GCC in Java. Currently, a few proofs of concept work on Android and Windows x64 systems. x84 and *NIX support is currently in development.

Jssembly jsm = new Jssembly();


Jssembly uses executable code "blocks" as its primary invokable piece of native code. There are two types of blocks: raw and assembly. Raw blocks contain opcodes whereas assembly blocks contain (you guessed it) platform-specific assembly. For example, here is a raw block called test1:

jsm.define("test1", new Block(raw) {{
		0x31, 0xC0, 0x48, 0xFF, 0xC0 ... 0xC3

And here is an x64 assembly block called test2:

jsm.define("test2", new Block(x64) {{
	__asm("mov rax, rdi")

We invoke test1 by calling jsm.get("test1").invoke(argument1, argument2 ... argN) or we can invoke a block in-place like so:

jsm.define("test3", new Block(x64) {{
		"nop",  // no-op
		"ret"   // return

Here we see yet another flavor of the ___asm syntax. Note that the parser is called when the Block constructor is called. In case of a syntax error, we should see an exception when a new definition occurs.


We can also pass a variable number of arguments to the invoke() method. These arguments can be accessed through platform-specific assembly.

Return types

In the works, although invoke() currently returns void.

Invocation woes

Great care must be taken with raw blocks as no viable run-time checks can be done on them. Make sure that the right raw code is executed on the right platform -- otherwise, the VM will crash. Naive checks are in the works for assembly blocks.