rem: if (frame == NULL)
add: if (frame == NULL) {
context: arch_check_syscall_restart(struct thread *t){	struct iframe *frame = i386_get_current_iframe();	if (frame == NULL)		// this thread is obviously new; we didn't come from an interrupt		return;	if ((status_t)frame->orig_eax >= 0 && (status_t)frame->eax == EINTR) {		frame->eax = frame->orig_eax;		frame->edx = frame->orig_edx;		frame->eip -= 2;			// undos the "int $99" syscall interrupt (so that it'll be called again)	}}