[PATCHv3 03/27] timens: Introduce CLOCK_MONOTONIC offsets

[Dmitry Safonov <dima@xxxxxxxxxx>]

From: Andrei Vagin <avagin@xxxxxxxxxx>

Add monotonic time virtualisation for time namespace.
Introduce timespec for monotionic clock into timens offsets and wire
clock_gettime() syscall.

Signed-off-by: Andrei Vagin <avagin@xxxxxxxxxx>
Co-developed-by: Dmitry Safonov <dima@xxxxxxxxxx>
Signed-off-by: Dmitry Safonov <dima@xxxxxxxxxx>
---
 include/linux/time_namespace.h |  8 ++++++++
 include/linux/timens_offsets.h |  1 +
 include/uapi/linux/time.h      |  2 ++
 kernel/time/posix-stubs.c      |  2 ++
 kernel/time/posix-timers.c     | 11 +++++++++--
 5 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/include/linux/time_namespace.h b/include/linux/time_namespace.h
index b6985aa87479..8f75d34cf34a 100644
--- a/include/linux/time_namespace.h
+++ b/include/linux/time_namespace.h
@@ -40,6 +40,13 @@ static inline void put_time_ns(struct time_namespace *ns)
 	kref_put(&ns->kref, free_time_ns);
 }
 
+static inline void timens_add_monotonic(struct timespec64 *ts)
+{
+        struct timens_offsets *ns_offsets = current->nsproxy->time_ns->offsets;
+
+        if (ns_offsets)
+                *ts = timespec64_add(*ts, ns_offsets->monotonic_time_offset);
+}
 
 #else
 static inline struct time_namespace *get_time_ns(struct time_namespace *ns)
@@ -65,6 +72,7 @@ static inline int timens_on_fork(struct nsproxy *nsproxy, struct task_struct *ts
 	return 0;
 }
 
+static inline void timens_add_monotonic(struct timespec64 *ts) {}
 #endif
 
 #endif /* _LINUX_TIMENS_H */
diff --git a/include/linux/timens_offsets.h b/include/linux/timens_offsets.h
index 7d7cb68ea778..248b0c0bb92a 100644
--- a/include/linux/timens_offsets.h
+++ b/include/linux/timens_offsets.h
@@ -3,6 +3,7 @@
 #define _LINUX_TIME_OFFSETS_H
 
 struct timens_offsets {
+	struct timespec64  monotonic_time_offset;
 };
 
 #endif
diff --git a/include/uapi/linux/time.h b/include/uapi/linux/time.h
index 958932effc5e..32abadc68f72 100644
--- a/include/uapi/linux/time.h
+++ b/include/uapi/linux/time.h
@@ -65,6 +65,8 @@ struct itimerval {
 #define CLOCKS_MASK			(CLOCK_REALTIME | CLOCK_MONOTONIC)
 #define CLOCKS_MONO			CLOCK_MONOTONIC
 
+#define CLOCK_TIMENS			1024
+
 /*
  * The various flags for setting POSIX.1b interval timers:
  */
diff --git a/kernel/time/posix-stubs.c b/kernel/time/posix-stubs.c
index 67df65f887ac..17c67e0aecd8 100644
--- a/kernel/time/posix-stubs.c
+++ b/kernel/time/posix-stubs.c
@@ -14,6 +14,7 @@
 #include <linux/ktime.h>
 #include <linux/timekeeping.h>
 #include <linux/posix-timers.h>
+#include <linux/time_namespace.h>
 #include <linux/compat.h>
 
 #ifdef CONFIG_ARCH_HAS_SYSCALL_WRAPPER
@@ -77,6 +78,7 @@ int do_clock_gettime(clockid_t which_clock, struct timespec64 *tp)
 		break;
 	case CLOCK_MONOTONIC:
 		ktime_get_ts64(tp);
+		timens_add_monotonic(tp);
 		break;
 	case CLOCK_BOOTTIME:
 		ktime_get_boottime_ts64(tp);
diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c
index 29176635991f..a047d6b7c768 100644
--- a/kernel/time/posix-timers.c
+++ b/kernel/time/posix-timers.c
@@ -30,6 +30,7 @@
 #include <linux/hashtable.h>
 #include <linux/compat.h>
 #include <linux/nospec.h>
+#include <linux/time_namespace.h>
 
 #include "timekeeping.h"
 #include "posix-timers.h"
@@ -190,6 +191,8 @@ static int posix_clock_realtime_adj(const clockid_t which_clock,
 static int posix_ktime_get_ts(clockid_t which_clock, struct timespec64 *tp)
 {
 	ktime_get_ts64(tp);
+	if (which_clock & CLOCK_TIMENS)
+		timens_add_monotonic(tp);
 	return 0;
 }
 
@@ -199,6 +202,8 @@ static int posix_ktime_get_ts(clockid_t which_clock, struct timespec64 *tp)
 static int posix_get_monotonic_raw(clockid_t which_clock, struct timespec64 *tp)
 {
 	ktime_get_raw_ts64(tp);
+	if (which_clock & CLOCK_TIMENS)
+		timens_add_monotonic(tp);
 	return 0;
 }
 
@@ -213,6 +218,8 @@ static int posix_get_monotonic_coarse(clockid_t which_clock,
 						struct timespec64 *tp)
 {
 	ktime_get_coarse_ts64(tp);
+	if (which_clock & CLOCK_TIMENS)
+		timens_add_monotonic(tp);
 	return 0;
 }
 
@@ -1039,7 +1046,7 @@ SYSCALL_DEFINE2(clock_gettime, const clockid_t, which_clock,
 	if (!kc)
 		return -EINVAL;
 
-	error = kc->clock_get(which_clock, &kernel_tp);
+	error = kc->clock_get(which_clock | CLOCK_TIMENS, &kernel_tp);
 
 	if (!error && put_timespec64(&kernel_tp, tp))
 		error = -EFAULT;
@@ -1121,7 +1128,7 @@ SYSCALL_DEFINE2(clock_gettime32, clockid_t, which_clock,
 	if (!kc)
 		return -EINVAL;
 
-	err = kc->clock_get(which_clock, &ts);
+	err = kc->clock_get(which_clock | CLOCK_TIMENS, &ts);
 
 	if (!err && put_old_timespec32(&ts, tp))
 		err = -EFAULT;
-- 
2.21.0