Microprocessor protected against stack overflow

Abstract

A microprocessor includes a central processing unit, at least one call stack, a stack pointer, an address bus, and a data bus. The microprocessor further includes a hardware monitor configured to supply protection codes, insert the protection codes in the stack or let the central processing unit insert them, and then generate an error signal in response to an attempt to modify a protection code present in the stack.

Description

BACKGROUND[0001]1. Technical Field[0002]The present disclosure relates to the protection of a microprocessor against stack overflow. The call stack of a microprocessor is a volatile memory zone directed to the storage of data concerning functions executed by the microprocessor. In particular, the stack allows the storage of an address to which the microprocessor should return after having executed a function.[0003]2. Description of the Related Art[0004]When a first function or “call function” calls a second function or “called function”, the call function places its return address in the stack. When the called function has finished the task for which it was designed, it fetches the return address from the stack. When the functions call each other, return addresses accumulate in the stack and are fetched one after the other after the execution of a function. Besides return addresses, the stack receives data associated with call or called functions, such as local variables of the call...

AI Technical Summary

Benefits of technology

The invention is about a microprocessor with a special hardware monitor that can generate protection codes and insert them in the stack or in the central processing unit (CPU). The monitor can also detect if someone tries to modify a protection code or read it from the stack. The monitor can be set up to generate random or pseudo-random protection codes, or deterministic and reproducible ones. It can also monitor the address bus and detect if an address of a stored protection code appears on it. The monitor can erase the protection code after verifying it. Overall, this invention provides enhanced security and protection for the microprocessor.

Problems solved by technology

This technique considerably increases the difficulty of exploiting stack overflow, since it relates to the attacker taking control of the instruction pointer by complex means.

Nevertheless, this technique is not infallible because it entirely depends on the provision of canary insertion and verification instructions in the program executed by the microprocessor.

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