2 files changed, 13 insertions, 1 deletions

diff --git a/include/linux/timex.h b/include/linux/timex.h
index d23999f9499d..aa60fe7b6ed6 100644
--- a/include/linux/timex.h
+++ b/include/linux/timex.h
@@ -73,7 +73,7 @@ struct timex {
         long tolerance;         /* clock frequency tolerance (ppm)
                                  * (read only)
                                  */
-        struct timeval time;    /* (read only) */
+        struct timeval time;    /* (read only, except for ADJ_SETOFFSET) */
         long tick;              /* (modified) usecs between clock ticks */
 
         long ppsfreq;           /* pps frequency (scaled ppm) (ro) */
@@ -102,6 +102,7 @@ struct timex {
 #define ADJ_STATUS              0x0010  /* clock status */
 #define ADJ_TIMECONST           0x0020  /* pll time constant */
 #define ADJ_TAI                 0x0080  /* set TAI offset */
+#define ADJ_SETOFFSET           0x0100  /* add 'time' to current time */
 #define ADJ_MICRO               0x1000  /* select microsecond resolution */
 #define ADJ_NANO                0x2000  /* select nanosecond resolution */
 #define ADJ_TICK                0x4000  /* tick value */
diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c
index ed8cfdf16983..5ac593267a26 100644
--- a/kernel/time/ntp.c
+++ b/kernel/time/ntp.c
@@ -648,6 +648,17 @@ int do_adjtimex(struct timex *txc)
                         hrtimer_cancel(&leap_timer);
         }
 
+        if (txc->modes & ADJ_SETOFFSET) {
+                struct timespec delta;
+                if ((unsigned long)txc->time.tv_usec >= NSEC_PER_SEC)
+                        return -EINVAL;
+                delta.tv_sec  = txc->time.tv_sec;
+                delta.tv_nsec = txc->time.tv_usec;
+                if (!(txc->modes & ADJ_NANO))
+                        delta.tv_nsec *= 1000;
+                timekeeping_inject_offset(&delta);
+        }
+
         getnstimeofday(&ts);
 
         write_seqlock_irq(&xtime_lock);