bytecode execution event

[Volker Simonis]

If you really want to see the execution of every single bytecode, you
can run in interpreted mode (`-Xint`) and use the
`-XX:+TraceBytecodes` command line option. There's also
`-XX:StopInterpreterAt=<int>`, but that's really only useful if
running in a native debugger like gdb. Both these options are only
available in debug builds (both fast- and slowdebug).

For what you plan to do it's probably better to write a Java bytecode
agent which allows you too hook into arbitrary Java methods [1]. There
exists a lot of information about bytecode instrumentation on the net,
but some of the tools you're definitely want to look at are ASM [2],
ByteBuddy [3] and Byteman [4].

Regards,
Volker

[1] https://docs.oracle.com/javase/8/docs/api/java/lang/instrument/package-summary.html
[2] https://asm.ow2.io/
[3] https://bytebuddy.net/#/
[4] https://byteman.jboss.org/

On Mon, May 15, 2023 at 4:00 PM QwertyYtPL QwertyYtPL
<qwertyytpl1612 at gmail.com> wrote:
>
> I wanted to modify OpenJDK's source code just for myself to add little event that will be called just before one bytecode will be called, in this event i want to be able to check what bytecode it is and like all attributes (i guess that i need Node or something). I want to do that to have control over java application ran, for example if I'm running some virus written in java I will be able to stop everything at some specific instruction that for example causes some file to download or command to execute. It will be a gate for creating some security system that for example asks the user if he wants a java program to download something or run something (on runtime). I think that I will just do this event that will call functions in my dll or something, so I won't be coping with the jdk build system. I can even do lua scripting for that, so my dll will be able to read lua script and let it handle events. I'm asking it here because firstly I have problems with finding a place for hooking an event and secondly I want to ask if it even makes sense.