linux-kernel - Re: [PATCH 00/51] rtc: stop using rtc deprecated functions

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Tue, 20 Jun 2017 23:38:59 +0100
From:   Russell King - ARM Linux <linux@...linux.org.uk>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
        Benjamin Gaignard <benjamin.gaignard@...aro.org>,
        Baruch Siach <baruch@...s.co.il>,
        "patches@...nsource.wolfsonmicro.com" 
        <patches@...nsource.wolfsonmicro.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Pavel Machek <pavel@....cz>, "x86@...nel.org" <x86@...nel.org>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Chen-Yu Tsai <wens@...e.org>, Ingo Molnar <mingo@...hat.com>,
        Sylvain Lemieux <slemieux.tyco@...il.com>,
        Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
        Len Brown <len.brown@...el.com>,
        "linaro-kernel@...ts.linaro.org" <linaro-kernel@...ts.linaro.org>,
        Jason Cooper <jason@...edaemon.net>,
        "rtc-linux@...glegroups.com" <rtc-linux@...glegroups.com>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        Hans Ulli Kroll <ulli.kroll@...glemail.com>,
        "adi-buildroot-devel@...ts.sourceforge.net" 
        <adi-buildroot-devel@...ts.sourceforge.net>,
        Vladimir Zapolskiy <vz@...ia.com>,
        John Stultz <john.stultz@...aro.org>,
        Gregory Clement <gregory.clement@...e-electrons.com>,
        Michael Chan <michael.chan@...adcom.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        Alessandro Zummo <a.zummo@...ertech.it>,
        Barry Song <baohua@...nel.org>,
        Support Opensource <Support.Opensource@...semi.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Steve Twiss <stwiss.opensource@...semi.com>,
        Maxime Ripard <maxime.ripard@...e-electrons.com>
Subject: Re: [PATCH 00/51] rtc: stop using rtc deprecated functions

On Wed, Jun 21, 2017 at 12:00:30AM +0200, Thomas Gleixner wrote:
> Yes, but there are still quite some issues to solve there:
> 
>      1) How do you tell the system that it should apply the offset in the
>      	first place, i.e at boot time before NTP or any other mechanism can
>      	correct it?
> 
>      2) Deal with creative vendors who have their own idea about the 'start
>      	of the epoch'
> 	
>      3) Add the information of wraparound time to the rtc device which
>      	needs to be filled in for each device. That way the rtc_***
>      	accessor functions can deal with them whether they wrap in 2038 or
>      	2100 or whatever.
> 
> #3 is the simplest problem of them :)	

Well, if there's additional non-volatile storage, you can store
additional information in there, but you still need the RTC
subsystem to be aware that the hardware is only 32-bit capable.

You'd also still need something along the lines I detailed
(redefining what dates the past 32-bit values indicate) to cope
with the RTC being set backwards after the machine thinks (possibly
incorrectly) that the date has jumped forwards.

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
according to speedtest.net.