Editing assembly on Mac OS X

Asked 19/12, 2009 at 6:56 Answered 4/12, 2011 at 17:52

I'm currently disassembling a Mach-O executable(the executable runs on Mac OS X, to be specific) in IDA Pro on windows. I have one instruction which I want to change, but it doesn't seem that IDA Pro allows you to do this. So, I tried using otool on OS X to dump the assembly(which it does fine). However, after editing the assembly in otool, I tried to reassemble it using as <file name of modified otool -tV output>. This greets me with a bunch of errors like Junk character 43 (+). What's the easiest way to change just a single instruction in a Mach-O binary on Mac OS X?

Countryman answered 19/12, 2009 at 6:56 Comment(0)

I've used both otool and otx to disassemble various binaries, and I've found the easiest way to edit them is to figure out what the assembly of the new code I want is (using nasm or similar), then just use a hex editor (I prefer Hex Fiend) on the binary file.

Arrivederci answered 19/12, 2009 at 7:10 Comment(2)

This seems like a horrible solution(though tolerable for small edits), especially considering that x86 has variable-length instructions. Are there no good tools for disassembling and reassembling files on OS X? – Countryman 19/12, 2009 at 7:24

unfurtunely there are no tools like ollydbg on OS X :( – Wallraff 11/1, 2010 at 14:33

I use Synalize It!.

You can load also a custom grammar (example for png files, showing header, tags, etc...)

Ephesus answered 4/12, 2011 at 17:52 Comment(0)

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