From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D0500C49361 for ; Mon, 28 Jun 2021 16:34:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B6B82613C2 for ; Mon, 28 Jun 2021 16:34:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231800AbhF1QhC (ORCPT ); Mon, 28 Jun 2021 12:37:02 -0400 Received: from relay1-d.mail.gandi.net ([217.70.183.193]:51335 "EHLO relay1-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231743AbhF1Qg6 (ORCPT ); Mon, 28 Jun 2021 12:36:58 -0400 Received: (Authenticated sender: alexandre.belloni@bootlin.com) by relay1-d.mail.gandi.net (Postfix) with ESMTPSA id ECDD7240003; Mon, 28 Jun 2021 16:34:30 +0000 (UTC) Date: Mon, 28 Jun 2021 18:34:30 +0200 From: Alexandre Belloni To: Werner Zeh Cc: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, x86@kernel.org, a.zummo@towertech.it, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/1] x86/kernel/rtc: add sanity check for RTC date and time Message-ID: References: <20210614110946.15587-1-werner.zeh@siemens.com> <20210624081507.15602-1-werner.zeh@siemens.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210624081507.15602-1-werner.zeh@siemens.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, On 24/06/2021 10:15:07+0200, Werner Zeh wrote: > The timekeeper is synchronized with the CMOS RTC when it is initialized. > If the RTC buffering is bad (not buffered at all, empty battery) the RTC > registers can contain random data. In order to avoid date and time > being completely rubbish check the sanity of the registers before > calling mktime64. If the values are not valid, set tv_sec to 0 so that > at least the starting time is valid. > > Signed-off-by: Werner Zeh > --- > [resent due to wrong lkml address] > [added RTC maintainers to the recipients] > This change introduces the same validity check that is already done in > drivers/rtc/interface.c. If it is not done here, the timekeeper can be > set up wrongly in the first run and won't be corrected once the RTC driver > is started because the validity check in the RTC driver drops the time and > date due to invalid entries. > > arch/x86/kernel/rtc.c | 12 +++++++++++- > 1 file changed, 11 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kernel/rtc.c b/arch/x86/kernel/rtc.c > index 586f718b8e95..f4af7b18c6c0 100644 > --- a/arch/x86/kernel/rtc.c > +++ b/arch/x86/kernel/rtc.c > @@ -9,6 +9,7 @@ > #include > #include > #include > +#include > > #include > #include > @@ -64,6 +65,7 @@ void mach_get_cmos_time(struct timespec64 *now) > { > unsigned int status, year, mon, day, hour, min, sec, century = 0; > unsigned long flags; > + struct rtc_time tm = {0}; > > /* > * If pm_trace abused the RTC as storage, set the timespec to 0, > @@ -118,7 +120,15 @@ void mach_get_cmos_time(struct timespec64 *now) > } else > year += CMOS_YEARS_OFFS; > > - now->tv_sec = mktime64(year, mon, day, hour, min, sec); > + tm.tm_sec = sec; > + tm.tm_min = min; > + tm.tm_hour = hour; > + tm.tm_mday = day; > + tm.tm_mon = mon; > + tm.tm_year = year; > + now->tv_sec = 0; > + if (rtc_valid_tm(&tm) == 0) Doesn't that make the x86 architecture depend on CONFIG_RTC_LIB? -- Alexandre Belloni, co-owner and COO, Bootlin Embedded Linux and Kernel engineering https://bootlin.com