>>646
copy_thread関数での以下の個所

int copy_thread(int nr, unsigned long clone_flags, unsigned long esp,
    unsigned long unused,
    struct task_struct * p, struct pt_regs * regs)
{
    struct pt_regs * childregs;

    childregs = ((struct pt_regs *) (THREAD_SIZE + (unsigned long) p)) - 1;
                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ここ