Messages in this thread Patch in this message | | | Date | Fri, 2 Jul 2021 16:10:54 +0200 | From | Alexandre Belloni <> | Subject | Re: [PATCH 1/1] x86/kernel/rtc: add sanity check for RTC date and time |
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On 30/06/2021 06:25:44+0000, Zeh, Werner wrote: > Hi Alexandre > > > 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 <werner.zeh@siemens.com> > > > --- > > > [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 <linux/export.h> > > > #include <linux/pnp.h> > > > #include <linux/of.h> > > > +#include <linux/rtc.h> > > > > > > #include <asm/vsyscall.h> > > > #include <asm/x86_init.h> > > > @@ -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? > > > CONFIG_RTC_LIB is already default enabled for x86, see arch/x86/Kconfig. > Do you have any other dependencies in mind I have overseen? >
Nope, everything is fine, it would be better if we could get rid of mach_get_cmos_time but I don't have any clue as to why this is necessary.
-- Alexandre Belloni, co-owner and COO, Bootlin Embedded Linux and Kernel engineering https://bootlin.com
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