[RFC PATCH 1/2] timekeeping: Add timekeeping_adjust_boottime

[Hikaru Nishida <hikalium@chromium.org>]

From: Hikaru Nishida <hikalium@chromium.org>

This introduces timekeeping_adjust_boottime() to give an interface to
modules that enables to advance CLOCK_BOOTTIME from userspace for
virtualized environments. Later patch introduces a sysfs interface
which calls this function.

Signed-off-by: Hikaru Nishida <hikalium@chromium.org>
---

 include/linux/timekeeping.h |  2 ++
 kernel/time/timekeeping.c   | 26 ++++++++++++++++++++++++++
 2 files changed, 28 insertions(+)

diff --git a/include/linux/timekeeping.h b/include/linux/timekeeping.h
index c6792cf01bc7..9bb91fbd945c 100644
--- a/include/linux/timekeeping.h
+++ b/include/linux/timekeeping.h
@@ -221,6 +221,8 @@ extern bool timekeeping_rtc_skipresume(void);
 
 extern void timekeeping_inject_sleeptime64(const struct timespec64 *delta);
 
+extern int timekeeping_adjust_boottime(const struct timespec64 *delta);
+
 /*
  * struct ktime_timestanps - Simultaneous mono/boot/real timestamps
  * @mono:	Monotonic timestamp
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 6aee5768c86f..02892deede62 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -1740,6 +1740,32 @@ void timekeeping_inject_sleeptime64(const struct timespec64 *delta)
 }
 #endif
 
+#if defined(CONFIG_BOOTTIME_ADJUSTMENT)
+/**
+ * timekeeping_adjust_boottime - Adjust CLOCK_BOOTTIME by adding a given delta
+ */
+int timekeeping_adjust_boottime(const struct timespec64 *delta)
+{
+	struct timekeeper *tk = &tk_core.timekeeper;
+	unsigned long flags;
+
+	if (!timespec64_valid_strict(delta))
+		return -EINVAL;
+
+	raw_spin_lock_irqsave(&timekeeper_lock, flags);
+	write_seqcount_begin(&tk_core.seq);
+
+	tk_update_sleep_time(tk, timespec64_to_ktime(*delta));
+	timekeeping_update(tk, TK_CLEAR_NTP | TK_MIRROR | TK_CLOCK_WAS_SET);
+
+	write_seqcount_end(&tk_core.seq);
+	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(timekeeping_adjust_boottime);
+#endif
+
 /**
  * timekeeping_resume - Resumes the generic timekeeping subsystem.
  */
-- 
2.30.0.478.g8a0d178c01-goog