timekeeping: Ignore the bogus sleep time if pm_trace is enabled

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 a4f8f6667f09 ("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 <tglx@linutronix.de>
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Acked-by: Pavel Machek <pavel@ucw.cz>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Xunlei Pang <xlpang@redhat.com>
Cc: Len Brown <lenb@kernel.org>
Link: http://lkml.kernel.org/r/1480372524-15181-3-git-send-email-john.stultz@linaro.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/arch/x86/kernel/rtc.c b/arch/x86/kernel/rtc.c
index 79c6311cd91252b9fe6b618b88d95b6ec4036bd2..5b21cb7d84d67773c6d4bfb86ab414bf7bc1c465 100644 (file)
--- a/arch/x86/kernel/rtc.c
+++ b/arch/x86/kernel/rtc.c
@@ -64,6 +64,15 @@ void mach_get_cmos_time(struct timespec *now)
        unsigned int status, year, mon, day, hour, min, sec, century = 0;
        unsigned long flags;
 
+       /*
+        * If pm_trace abused the RTC as storage, set the timespec to 0,
+        * which tells the caller that this RTC value is unusable.
+        */
+       if (!pm_trace_rtc_valid()) {
+               now->tv_sec = now->tv_nsec = 0;
+               return;
+       }
+
        spin_lock_irqsave(&rtc_lock, flags);
 
        /*

diff --git a/drivers/base/power/trace.c b/drivers/base/power/trace.c
index efec10b49d59a72234ec3544b63edd9d5ab144c4..1cda505d6a852bb9b9e698a9c2788e5def59f30e 100644 (file)
--- a/drivers/base/power/trace.c
+++ b/drivers/base/power/trace.c
@@ -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;
 }
 

diff --git a/drivers/rtc/rtc-cmos.c b/drivers/rtc/rtc-cmos.c
index dd3d59806ffa02ef955660390533881d9f6cee62..b27a18968a1adf6001bd8b6a4d079f39acafcdda 100644 (file)
--- a/drivers/rtc/rtc-cmos.c
+++ b/drivers/rtc/rtc-cmos.c
@@ -191,6 +191,13 @@ static inline void cmos_write_bank2(unsigned char val, unsigned char addr)
 
 static int cmos_read_time(struct device *dev, struct rtc_time *t)
 {
+       /*
+        * If pm_trace abused the RTC for storage, set the timespec to 0,
+        * which tells the caller that this RTC value is unusable.
+        */
+       if (!pm_trace_rtc_valid())
+               return -EIO;
+
        /* REVISIT:  if the clock has a "century" register, use
         * that instead of the heuristic in mc146818_get_time().
         * That'll make Y3K compatility (year > 2070) easy!

diff --git a/include/linux/mc146818rtc.h b/include/linux/mc146818rtc.h
index a585b4b5fa0ef70e21cac6b02b0c4150ed3cc68b..0661af17a75846cdc320f5a41fa0295922859dcf 100644 (file)
--- a/include/linux/mc146818rtc.h
+++ b/include/linux/mc146818rtc.h
@@ -16,6 +16,7 @@
 #include <asm/mc146818rtc.h>           /* register access macros */
 #include <linux/bcd.h>
 #include <linux/delay.h>
+#include <linux/pm-trace.h>
 
 #ifdef __KERNEL__
 #include <linux/spinlock.h>            /* spinlock_t */

diff --git a/include/linux/pm-trace.h b/include/linux/pm-trace.h
index ecbde7a5548ec3008e0dfa0955540ffac245287f..7b78793f07d7df692aea26feae8b756185016ab8 100644 (file)
--- a/include/linux/pm-trace.h
+++ b/include/linux/pm-trace.h
@@ -1,11 +1,17 @@
 #ifndef PM_TRACE_H
 #define PM_TRACE_H
 
+#include <linux/types.h>
 #ifdef CONFIG_PM_TRACE
 #include <asm/pm-trace.h>
-#include <linux/types.h>
 
 extern int pm_trace_enabled;
+extern bool pm_trace_rtc_abused;
+
+static inline bool pm_trace_rtc_valid(void)
+{
+       return !pm_trace_rtc_abused;
+}
 
 static inline int pm_trace_is_enabled(void)
 {
@@ -24,6 +30,7 @@ extern int show_trace_dev_match(char *buf, size_t size);
 
 #else
 
+static inline bool pm_trace_rtc_valid(void) { return true; }
 static inline int pm_trace_is_enabled(void) { return 0; }
 
 #define TRACE_DEVICE(dev) do { } while (0)