os_kernel/kernel/mem.c

// #include <stdio.h>
int main()
{
    int in_a = 1, in_b = 2, out_sum;
    // printf("in_b is %d\n", in_b);
    asm("movb %b0, %1;" ::"a"(in_a), "m"(in_b));
    // printf("in_b now is %d\n", in_b);
    return 0;
}