hard_reset.c

#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <machine/cpufunc.h>

int main() {
    /* Opening /dev/io grants the process permission to use outb/inb 
       instructions on FreeBSD x86/amd64 systems. */
    int fd = open("/dev/io", O_RDWR);
    if (fd == -1) {
        perror("open /dev/io (Are you root?)");
        printf("Note: Ensure 'io' device is available or use 'kldload io'\n");
        return 1;
    }

    printf("Permission granted. Triggering hard reset via port 0xcf9...\n");

    /* * Port 0xcf9: Reset Control Register
     * Value 0x06: 
     * Bit 1 (SYS_RST): System Reset
     * Bit 2 (RST_CPU): Reset CPU
     */
    outb(0xcf9, 0x06);

    /* If it hasn't rebooted yet, the CPU might need a moment to process */
    usleep(10000);
    
    close(fd);
    return 0;
}