Question

A.3 Is it ever safe for a user program to use registers \(k0 or \)k1?

Short answer

No, it's not safer for a user to use register $k0 or $k1.

Step-by-step solution

MIPS

The MIPS processor's assembly language is simply known as MIPS assembly language. MIPS is an acronym for Microprocessor without Interlocked Pipeline Stages. Learning the MIPS assembly language is quite beneficial. Knowing how to code in this language allows you to gain a better knowledge of how these systems work on a more fundamental level.MIPS features a total of 64 registers, including 32 general-purpose registers and 32 floating-point registers. The dollar symbol ($) appears on all registers. $f0, $f1,..., $f31 are the names of the floating-point registers. The general-purpose registers are given below and include both names and numbers. It is usually advisable to utilize the register names while programming in the MIPS assembler.

Usage of registers $k0 and $k1

$k0 and $k1 are used as aliases for registers $26 and $27.

The k registers are set aside for use by the operating system kernel. They can change at any time since interrupt handlers use them. The interrupt handler is allowed to use without having to save or restore its values. The OS can use it for whatever it wants. They Can be useful as scratch registers that can be used without any obligations of corrupting the user-space state. This allows just enough leeway to start saving registers, as well as making returning from the interrupt handler possible. The $K0 and $K1 cannot be used for the user program, This is because exceptions occur asynchronously with a program, and these registers $k0 and $k1 are the only safe registers reserved for the exception handler. As $k0 and $k1 are solely used as exception handling registers, using them in a normal user program will not be safe.