stack_align
tf->tf_sp = (intptr_t)stack_align(stack);
return (char *)stack_align((intptr_t)l->l_sigstk.ss_sp + l->l_sigstk.ss_size);
return (void *)(intptr_t)stack_align(tf->tf_sp);
tf->tf_sp = stack_align((intptr_t)stack + stacksize);