[TUHS] Unix Reverse Engineering

[segaloco via TUHS]

On Monday, May 12th, 2025 at 5:49 AM, Thalia Archibald via TUHS <tuhs at tuhs.org> wrote:

> On May 12, 2025, at 04:04, Noel wrote:
> 
> > That's going to be a real trick; 'as' was written in PDP-11 assembler:
> 
> 
> It has, indeed, been quite the challenge to translate. I’ve completed 1114/3531
> lines or 7/20 files in my translation of `as` to C. It seems that it was never
> ported to C by the original authors, so this is probably the most closely
> someone’s looked at many parts of it in a long time.
> 
> I’ve very steadily been improving my PDP-11 assembly skills and rather efficient
> now. It’s quite tedious tracking all the register effects, though good
> signatures annotated with in- and out-registers helps a lot. I feel like a
> compiler, manually performing control flow structuring like the Relooper or LLVM
> Stackifier algorithms. With this completed, my manual effort will bootstrap
> reverse engineering the rest with a proper decompiler.
> 
> Thalia

Not sure how helpful it'd be, but pdp11-dec-aout is a valid target for GNU
binutils as of the current version, so objdump may be another
disassembler/analyzer option.

If it helps, here's some stalled-out work on disassembling V2 commands:

https://gitlab.com/segaloco/v2src

Do you have a particular end-goal in mind or is it just an exercise?

- Matt G.