Hacking Java Bytecode for Programmers (Part 2)

Re:Hacking Java Bytecode for Programmers (Part 2) by cypher543 on Friday May 17, 2013 @03:48PM (#5726363)

Maybe I'm not part of the target audience for this article, but it seems to lack quite a bit of information. For example, you explain what op-codes are, but then only cover one of them. I think at least a basic overview of common op-codes and how they work together would have been great. Also, the "hacking" you demonstrate is simply replacing a string, which is certainly not Java-specific and rarely useful. A more interesting example would have been changing the control flow in some way.

Of course, that's not to say it's a bad article. I just think you could have expanded quite a bit more.

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Re:Hacking Java Bytecode for Programmers (Part 2) by gtani on Friday May 17, 2013 @04:20PM (#5726508)

I think target audience is folks who're mucking around the low-levels using javap, proguard, Jconsole/visualVM tools (jmap, jstack etc) and other diagnostic/disassembler tools like that for benchmarking/tuning, picking hotspot command line options, looking for malware, shoehorning into android etc. Javap is pretty well documented, you could start there.

this is good, about byteman, JRebel, tools like that

http://arhipov.blogspot.ie/2012/09/javazone-2012-taming-java...

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Re:Hacking Java Bytecode for Programmers (Part 2) by voidlogic on Friday May 17, 2013 @04:40PM (#5726597)

>>Maybe I'm not part of the target audience for this article, but it seems to lack quite a bit of information.

I think for anyone with minimal assembly experience or a desire to learn this is pretty straight forward.

>>For example, you explain what op-codes are, but then only cover one of them.

He gives you a link to the list of all of the op codes... Did you read it?

>>I think at least a basic overview of common op-codes and how they work together would have been great

Maybe this is going to be in a follow up article. But after explaining the concept, giving you toy example and giving you the opcode list, with the provided hexdump you should be able to start doing this yourself. Try it! Its fun.

>>Also, the "hacking" you demonstrate is simply replacing a string, which is certainly not Java-specific and rarely useful

Intro to concept examples are often toy examples....

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Re:Hacking Java Bytecode for Programmers (Part 2) by jfolkins on Friday May 17, 2013 @04:22PM (#5726520)

Nah, I think you probably are. I'm just laying the ground work so that someone could start at the beginning and get to the point where they can, say, change a if_icmpeq to a if_icmpne.

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