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
| ||
|
Date: Thu, 25 Apr 2013 15:02:31 -0600 From: Jason Gunthorpe <jgunthorpe@...idianresearch.com> To: John Stultz <john.stultz@...aro.org> Cc: Alexander Holler <holler@...oftware.de>, Kay Sievers <kay@...y.org>, LKML <linux-kernel@...r.kernel.org>, Feng Tang <feng.tang@...el.com> Subject: Re: CONFIG_RTC_HCTOSYS lost on x86 with ALWAYS_USE_PERSISTENT_CLOCK changes? On Thu, Apr 25, 2013 at 01:03:00PM -0700, John Stultz wrote: > On 04/25/2013 11:33 AM, Jason Gunthorpe wrote: > >John mentioned they might be kept for embedded - eg size reduction. > >The issue with that idea is if you do not enable the class RTC > >subsystem then there is no way for a small embedded userspace to set > >the RTC. The /dev/rtc* device obviously goes away, but it also turns > >out that that CONFIG_GENERIC_CMOS_UPDATE only works when combined with > >a heavy weight userspace NTPD that runs the kernel PLL properly. The > >kernel NTP code is enormously conservative and it is actually quite > >hard to get it to write to the RTC. An RTC that cannot be set is > >useless, so these days I feel CONFIG_RTC is pragmatically mandatory - > >and my space constrained embedded systems do set it, for these > >reasons. > > So I mentioned that the size-reduciton focused folks might not like > the generic rtc core over the persistent_clock code, but I'm not > convinced that's a reason to keep the persistent clock code (which What I mean is you can't actually choose to use persistent_clock over rtc core, that is not a choice. The only choice these days it to omit the user space interface to the RTC (eg rtc core). On some platforms the RTC will still get *read* during boot via persisent_clock, but no platform has a way for userspace to *set* via persisent_clock. update_persisent_clock is not connected to userspace anymore. An unsettable RTC is useless, IMHO. > I only noted it, because it has come up prior as a complaint when > switching to the RTC core was proposed. Sure, but, AFAIK, that was a general concern of /dev/rtc vs /dev/rtc0 - however since then we have lost /dev/rtc completely. That means there is no longer any way to access the persistent_clock functions from userspace. Jason -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists