> Why not kill the process instantly on a prohibited read, then? Do these prohibited reads happen too often to switch from "oh, that's okay, you can try again a

> Why not kill the process instantly on a prohibited read, then? Do these prohibited reads happen too often to switch from "oh, that's okay, you can try again and do other stuff" to "the punishment is death"? It's an interesting question. The pedantic answer is that they technically do actually happen all the time, that's just a page-fault. However in the page-fault handler you could just check what address they were looking at (And we already do, since we have to decide if we need to map a page, or throw a SIGSEGV), so effectively you could block them by checking the address. But it's actually fundamentally a lot worse. On its own, meltdown might be preventable that way, but you can combine meltdown with similar patterns to the spectre exploit to achieve the meltdown exploit without raising the exception. The kernel then can't prevent this, because no exception is raised, so it doesn't actually know anything happened.