libutils/arch_include/arm/utils/arch/ud.h

/*
 * Copyright 2017, Data61
 * Commonwealth Scientific and Industrial Research Organisation (CSIRO)
 * ABN 41 687 119 230.
 *
 * This software may be distributed and modified according to the terms of
 * the BSD 2-Clause license. Note that NO WARRANTY is provided.
 * See "LICENSE_BSD2.txt" for details.
 *
 * @TAG(DATA61_BSD)
 */

#pragma once

#include <utils/attribute.h>

#define UD_INSTRUCTION_SIZE 4

static inline void ALWAYS_INLINE utils_undefined_instruction(void) {
    /* Section §A8.8.247 of the ARM manual says that 'udf' can be used to generate an
       undefined instruction. Unfortunately this mnenomic is not present on armv8,
       but the opcode is still presently undefined. To work around this we use the raw
       opcode for the udf instruction, and rely on it still being undefined on armv8. */
    asm volatile (".word 0xe7f0def0");
}