[PATCH v3 4/4] vdso/gettimeofday: Add support for CLOCK_REALTIME_ALARM

[Thomas Weißschuh]

CLOCK_REALTIME_ALARM behaves exactly as CLOCK_REALTIME as far as the
vDSO is concerned. The vDSO library can handle it automatically
correctly. Only the basetime needs to be maintained during the tick.

Reuse the CLOCK_REALTIME basetime for CLOCK_REALTIME_ALARM and update
the userspace hres clock mask to include CLOCK_REALTIME_ALARM.

Signed-off-by: Thomas Weißschuh <linux@xxxxxxxxxxxxxx>
---
 include/vdso/datapage.h | 3 ++-
 kernel/time/vsyscall.c  | 4 ++++
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/include/vdso/datapage.h b/include/vdso/datapage.h
index 49f388a54e6a..a239a2861d0e 100644
--- a/include/vdso/datapage.h
+++ b/include/vdso/datapage.h
@@ -40,7 +40,8 @@ struct vdso_arch_data {
 			 BIT(CLOCK_MONOTONIC_COARSE))
 #define VDSO_RAW	(BIT(CLOCK_MONOTONIC_RAW))
 #define VDSO_AUX	__GENMASK(CLOCK_AUX_LAST, CLOCK_AUX)
-#define VDSO_ALARM	BIT(CLOCK_BOOTTIME_ALARM)
+#define VDSO_ALARM	(BIT(CLOCK_BOOTTIME_ALARM)	| \
+			 BIT(CLOCK_REALTIME_ALARM))
 
 /**
  * struct vdso_timestamp - basetime per clock_id
diff --git a/kernel/time/vsyscall.c b/kernel/time/vsyscall.c
index 4231b04aec2c..2125c462913b 100644
--- a/kernel/time/vsyscall.c
+++ b/kernel/time/vsyscall.c
@@ -81,6 +81,10 @@ static inline void update_vdso_time_data(struct vdso_time_data *vdata, struct ti
 	vdso_ts		= &vdata->hres_coarse.basetime[CLOCK_TAI];
 	vdso_ts->sec	= tk->xtime_sec + (s64)tk->tai_offset;
 	vdso_ts->nsec	= tk->tkr_mono.xtime_nsec;
+
+	/* CLOCK_REALTIME_ALARM, copy of CLOCK_REALTIME */
+	vdso_ts		= &vdata->hres_coarse.basetime[CLOCK_REALTIME_ALARM];
+	*vdso_ts	= vdata->hres_coarse.basetime[CLOCK_REALTIME];
 }
 
 void update_vsyscall(struct timekeeper *tk)

-- 
2.56.0