Viewing profile — rrnewton

I thought it was very cool how gVisor is multi-backend (their “sentry” implemented vie either ptrace or kvm), which is pretty unusual with instrumentation tools. We could maybe hav…

The distinction that we often have trouble getting across is between eliminating/controlling nondeterminism, vs recording what happens to occur. Undo, like rr, and Microsoft TTD, r…

There’s a bit of shared lineage there. Joseph Devietti and I started working in this area together around 2015. And Joe had worked on the deterministic dOS at UW during his PhD (wh…

Yeah, it's interesting to think about persisting the state we would need to make the file system more sympatico with Hermit. If we were willing to have a daemon.... Meta develops t…

Well, we don't prove the absence of concurrency bugs -- that would be more a job for formal verification, type systems, at the source level. But we can tell when our `--chaos` stre…

Yep, good point -- should have mentioned it. That's still roughly accurate because Hermit is, today, still ptrace-powered. I'll quote my reply from elsewhere about the WIP high-per…

Thanks for all the questions! Whew, here goes. > How are you sanitizing the result of stat(), for example? Ah, that part's the same as it was described in the ASPLOS'20 paper ( htt…

Well, the starting datetime at the beginning of execution in the container is whatever you set it to: $ hermit run --epoch=2022-01-01T00:00:00Z /bin/date Fri Dec 31 16:00:00 PST 20…

Ah, at least you were in good hands with Michael Vollmer. Btw, he's now a prof at University of Kent in the UK ( http://recurial.com/ ).

Well, probably not on device ;-). The underlying Reverie instrumentation layer works on ARM, but Hermit isn't ported yet, and we haven't touched RISC-V yet at all. (Contributions w…

Well, gettimeofday is a syscall, and we do intercept it (along with clock_gettime, clock_gettres, time, nanosleep, and the rdtsc instruction, even though that last one is not a sys…

Yes, I'm very interested in that as well. I've been involved with the ACM Artifact Evaluation process which has been going on in several conferences for a while. https://www.acm.or…

Alas the performance overhead in realtime is not great yet. It still uses ptrace currently, which often results in a multiple-X slowdown (but at least it doesn't "subscribe" to eve…

Sure! So it really breaks down into two cases: internal and external networking relative to the container Hermit creates. (1) internal networking If you run a test like `rust/netwo…

Sure! I think underpinning your question is a really subtle point there. And I think the answer is in the different purposes of regression testing and bug finding. In regression te…

Reverted a badly-timed breaking change that came through the sync system. Will fix it properly shortly (and add a Dockerfile and release tag). But for now you may have better luck …

(1) rr [formerly Mozilla rr] We're big fans of rr! Hermit is different in that creating a deterministic OS semantics is different than recording whatever nondeterministic behavior …

It's a good question. We would like to make it usable as a platform for dynamic analysis. The idea being that you can control all these external factors (like thread scheduling), f…

Heh, I implore you to consider the engineers-eye view. We're tech geeks inside or outside of FAANG, with all the usual incentives. I've been the tech lead on this project for 5 yea…

Yes indeed. That concurrency testing capability is a pretty well-studied area and we implement a couple existing algorithms. The first is our adaptation of the PCT algorithm (ASPLO…

Note that this is a follow-on project from the earlier Dettrace system, which was applied mainly to reproducible builds (as in the academic paper, https://dl.acm.org/doi/10.1145/33…

This has been the culmination of several years of work intercepting and sanitizing the Linux system call API. It's now open source.

Hmm, why is this a good thing compared to just using Nix / nix-pkgs to manage JS packages?