Question

A friend sent me that code and alleges that it could damage the processor. Is that true?

void damage_processor() {
    while (true) {
        // Assembly code that sets the five control registers bits to ones which causes a bunch of exceptions in the system and then damages the processor
        Asm(
            "mov cr0, 0xffffffff \n\t"
            "mov cr1, 0xffffffff \n\t"
            "mov cr2, 0xffffffff \n\t"
            "mov cr3, 0xffffffff \n\t"
            "mov cr4, 0xffffffff \n\t"
        )
    }
}

Is that true?

Answer 1

From userspace code? No. It’ll cause a privilege exception and the kernel will terminate your program. From kernel code? I doubt it; you will be throwing exceptions, and you’d have to manually set up the fault handler to return to the code in question to keep doing it. There’s also a decent chance you’ll cause a triple fault if part of the CR3 move succeeds, since that controls the page table address and you’ll probably get faults on instruction fetch, handler fetch, and then the double fault handler fetch. The CPU should just shut down if that happens.

Check the Intel or AMD manuals for Systems programming, they’ll tell you which exceptions will be thrown when writing invalid bits to the control registers.