linux-kernel - bad time after boot (read from absent hardware?): "Time: 165:165:165 Date: 165/165/65"

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Date:	Tue, 28 May 2013 10:19:45 +0200
From:	"Ulrich Windl" <Ulrich.Windl@...uni-regensburg.de>
To:	<linux-kernel@...r.kernel.org>
Subject: bad time after boot (read from absent hardware?): "Time:
 165:165:165  Date: 165/165/65"

Hi!

Some time ago I discovered strange output in boot messages, just as if the kernel trusts junk from hardware that is not present, like the RTC in a paravirtualized Xen guest (the guest has no /dev/rtc*). The message says:
<6>[    0.123524] Time: 165:165:165  Date: 165/165/65

Obviously, if there were some validity check, this wouldn't pass, so I guess there is none!

In Xen's message buffer (hypervisor) I only see this error (that seems unrelated):
(XEN) mm.c:833:d6 Non-privileged (6) attempt to map I/O space 000000f0

According to my source code the print originates from read_magic_time() in /drivers/base/power/trace.c.

I'm running kernel 3.0.74-0.6.8-xen (SLES11 SP2) on x86_64.

Regards,
Ulrich

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