Intel® Memory Protection Extensions Enabling Guide

Abstract: This document describes Intel® Memory Protection Extensions (Intel® MPX), its motivation, and programming model. It also describes the enabling requirements and the current status of enabling in the supported OSs: Linux* and Windows* and compilers: Intel® C++ Compiler, GCC, and Visual C++*. Finally, the paper describes how ISVs can incrementally enable bounds checking in their Intel MPX applications.

Introduction

C/C++ pointer arithmetic is a convenient language construct often used to step through an array of data structures. If an iterative write operation does not take into consideration the bounds of the destination, then adjacent memory locations may get corrupted. Such modification of adjacent data not intended by the developer is referred as a Buffer Overflow. Similarly, uncontrolled reads could reveal cryptographic keys and passwords. Buffer overflows have been known to be exploited, causing Denial of Service (DOS) attacks and system crashes. More sinister attacks, which do not immediately draw the attention of the user or system administrator, alter the code execution path, such as modifying the return address in the stack frame, to execute malicious code or script.

Intel’s Execute Disable Bit and similar hardware features from other vendors have blocked all buffer overflow attacks that redirected the execution to malicious code stored as data. Various other techniques adopted by compiler vendors to mitigate buffer overflow problems can be found in the references.

Intel® MPX technology consists of new Intel® architecture instructions and registers that C/C++ compilers can use to check the bounds of a pointer before it is used. This new hardware technology will be enabled in future Intel® processors. The supported compilers are Intel® C/C++ compiler, GCC (GNU C/C++ compiler) and Microsoft* Visual C++* .

For more complete information about compiler optimizations, see our Optimization Notice.
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