1. (13 points) Recently, security experts revealed two critical hardware vulnerabilitiesn modern processors, Meltdown and Spectre. These hardware vulnerabilities allow programs to steal data which is currently processed on the computer. These two vulnerabilities have raised serious security concerns because they may affect many modern processors Let us discuss Meltdown. The following is the abstract from the paper published by the experts who revealed Meltdown: The security of computer systems fundamentally relies on memory isolation, e.g., kernel address ranges are marked as non-accessible and are protected from user access. In this paper, we present Meltdown. Meltdown exploits side effects of out-of-order execution on modern processors to read arbitrary kernel-memory locations including personal data and passwords. Out-of-order execution is an indispensable performance feature and present in a wide range of modern processors. The attack is independent of the operating system, and it does not rely on any software vulnerabilities. Meltdown breaks all security assumptions given by address space isolation as well as paravirtualized environments and, thus, every security mechanism building upon this foundation. On affected systems, Meltdown enables an adversary to read memory of other processes or virtual machines in the cloud without any permissions or privileges, affecting millions of customers and virtually every user of a personal computer. To understand this paper, the reader needs to be familiar with modern computer architecture. Please answer the following questions (a) [2 points] On a modern system, programs can run concurrently, but programs are typically not permitted to read the memory data from other programs. Please explain what architecture support is needed for this (b) [2 points] As mentioned in the abstract, Meltdown exploits side effects of out-of-order execution on modern processors. Please explain why out-of-order execution is an indispensable performance feature on modern processors