You're quite right, it's very possible. The product I work on does pretty much exactly this - we need it because our debugger time travels and we can't allow h

You're quite right, it's very possible. The product I work on does pretty much exactly this - we need it because our debugger time travels and we can't allow history to be altered! I wrote some words here: https://medium.com/time-travel-debugging/calling-functions-in-the-past-4bb03bdc124d https://medium.com/time-travel-debugging/calling-functions-i... But it's basically exactly what you propose. We didn't sandbox the syscalls but you could do that too.