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timekeeping: Ignore the bogus sleep time if pm_trace is enabled

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Power management suspend/resume tracing (ab)uses the RTC to store
suspend/resume information persistently. As a consequence the RTC value is
clobbered when timekeeping is resumed and tries to inject the sleep time.

Commit a4f8f6667f ("timekeeping: Cap array access in timekeeping_debug")
plugged a out of bounds array access in the timekeeping debug code which
was caused by the clobbered RTC value, but we still use the clobbered RTC
value for sleep time injection into kernel timekeeping, which will result
in random adjustments depending on the stored "hash" value.

To prevent this keep track of the RTC clobbering and ignore the invalid RTC
timestamp at resume. If the system resumed successfully clear the flag,
which marks the RTC as unusable, warn the user about the RTC clobber and
recommend to adjust the RTC with 'ntpdate' or 'rdate'.

[jstultz: Fixed up pr_warn formating, and implemented suggestions from Ingo]
[ tglx: Rewrote changelog ]

Originally-from: Thomas Gleixner <[email protected]>
Signed-off-by: Chen Yu <[email protected]>
Signed-off-by: John Stultz <[email protected]>
Acked-by: Pavel Machek <[email protected]>
Acked-by: Thomas Gleixner <[email protected]>
Cc: Prarit Bhargava <[email protected]>
Cc: "Rafael J. Wysocki" <[email protected]>
Cc: Richard Cochran <[email protected]>
Cc: Xunlei Pang <[email protected]>
Cc: Len Brown <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Thomas Gleixner <[email protected]>
This commit is contained in:
Chen Yu 2016-11-28 14:35:19 -08:00 • committed by Thomas Gleixner
commit ba58d1020a
5 changed files with 52 additions and 1 deletions
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27
drivers/base/power/trace.c
View file

@ -10,6 +10,7 @@
#include <linux/pm-trace.h>
#include <linux/export.h>
#include <linux/rtc.h>
#include <linux/suspend.h>
#include <linux/mc146818rtc.h>
@ -74,6 +75,9 @@
#define DEVSEED (7919)
bool pm_trace_rtc_abused __read_mostly;
EXPORT_SYMBOL_GPL(pm_trace_rtc_abused);
static unsigned int dev_hash_value;
static int set_magic_time(unsigned int user, unsigned int file, unsigned int device)
@ -104,6 +108,7 @@ static int set_magic_time(unsigned int user, unsigned int file, unsigned int dev
time.tm_min = (n % 20) * 3;
n /= 20;
mc146818_set_time(&time);
pm_trace_rtc_abused = true;
return n ? -1 : 0;
}
@ -239,9 +244,31 @@ int show_trace_dev_match(char *buf, size_t size)
return ret;
}
static int
pm_trace_notify(struct notifier_block *nb, unsigned long mode, void *_unused)
{
switch (mode) {
case PM_POST_HIBERNATION:
case PM_POST_SUSPEND:
if (pm_trace_rtc_abused) {
pm_trace_rtc_abused = false;
pr_warn("Possible incorrect RTC due to pm_trace, please use 'ntpdate' or 'rdate' to reset it.\n");
}
break;
default:
break;
}
return 0;
}
static struct notifier_block pm_trace_nb = {
.notifier_call = pm_trace_notify,
};
static int early_resume_init(void)
{
hash_value_early_read = read_magic_time();
register_pm_notifier(&pm_trace_nb);
return 0;
}