time: Add do_timens_ktime_to_host() helper

[linux-2.6-microblaze.git] / kernel / time / namespace.c

diff --git a/kernel/time/namespace.c b/kernel/time/namespace.c
index c2a58e4..1a0fbaa 100644 (file)
--- a/kernel/time/namespace.c
+++ b/kernel/time/namespace.c
@@ -16,6 +16,42 @@
 #include <linux/err.h>
 #include <linux/mm.h>
 
+ktime_t do_timens_ktime_to_host(clockid_t clockid, ktime_t tim,
+                               struct timens_offsets *ns_offsets)
+{
+       ktime_t offset;
+
+       switch (clockid) {
+       case CLOCK_MONOTONIC:
+               offset = timespec64_to_ktime(ns_offsets->monotonic);
+               break;
+       case CLOCK_BOOTTIME:
+       case CLOCK_BOOTTIME_ALARM:
+               offset = timespec64_to_ktime(ns_offsets->boottime);
+               break;
+       default:
+               return tim;
+       }
+
+       /*
+        * Check that @tim value is in [offset, KTIME_MAX + offset]
+        * and subtract offset.
+        */
+       if (tim < offset) {
+               /*
+                * User can specify @tim *absolute* value - if it's lesser than
+                * the time namespace's offset - it's already expired.
+                */
+               tim = 0;
+       } else {
+               tim = ktime_sub(tim, offset);
+               if (unlikely(tim > KTIME_MAX))
+                       tim = KTIME_MAX;
+       }
+
+       return tim;
+}
+
 static struct ucounts *inc_time_namespaces(struct user_namespace *ns)
 {
        return inc_ucount(ns, current_euid(), UCOUNT_TIME_NAMESPACES);