sandsifter VS mishegos

This has some background.

sandsifter

This is a really clever technique! I was impressed by sandsifter[1] when it originally came out, and this seems an awful lot faster and less prone to false negatives (since it's purely speculative and doesn't require sandsifter's `#PF` hack).

At the risk of unwarranted self-promotion: the other side of this equation is fidelity in software instruction set decoders. x86's massive size and layers of historical complexity make it among the most difficult instruction formats to accurately decode; I've spent a good part of the last two years working on a fuzzer that's discovered thousands of bugs in various popular x86 decoders[2][3].

[1]: https://github.com/xoreaxeaxeax/sandsifter

[2]: https://github.com/trailofbits/mishegos

[3]: https://ww.easychair.org/publications/preprint_download/1LHr

Idea:

If any assembler/disassembler author/team out there wants to produce an assembler/disassembler which is authoritative (difficult to do on x86, because there are so many different possible combinations of instruction encoding, https://github.com/xoreaxeaxeax/sandsifter : "Typically, several million undocumented instructions on your processor will be found, but these generally fall into a small number of different groups.") -- then what they'd do is to create a third program -- which "pits" the output of Assembler A vs. Assembler B, Disassembler A vs. Disassembler B...

That is, between any two assemblers (for the same CPU architecture/instruction set), or any two disassemblers, where are the anomalies?

If we think about an assembler as a simple function, y=f(x), that is, I give it a string of ascii bytes as input (x), and I get a string (1..n) binary bytes as output (y),

Differential fuzzing is woefully underutilized -- our experience is that it consistently[1] finds[2] bugs that "traditional" fuzzing techniques struggle to discover, and that the primary obstacles to its adoption are harness and orchestration complexity. DIFFER goes a long way towards overcoming those obstacles!

(FD: My company.)

[1]: https://github.com/trailofbits/mishegos

[2]: https://x509-limbo.com/

You may also want to check mishegos for another way of comparing different decoders.

Take a look at something like mishegos to see how sometimes the same instruction will be decoded differently by different disassemblers: https://github.com/trailofbits/mishegos

It sounds like what you want is Mishegos [1], described here [2].

[1] https://github.com/trailofbits/mishegos