From 43fe500f3b619cfdfe110069515994513c30069c Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Sun, 31 Aug 2008 08:09:53 -0700
Subject: [PATCH] --- yaml --- r: 117593 b: refs/heads/master c:
 df0cc0539b4127bd02f64de2c335b4af1fdb3845 h: refs/heads/master i:   117591:
 91e3efb4cf90d2b803cbd35dd676a5c1c159e6b0 v: v3

---
 [refs]                     |  2 +-
 trunk/include/linux/time.h |  4 ++++
 trunk/kernel/time.c        | 18 ++++++++++++++++++
 3 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/[refs] b/[refs]
index 81ce37d6bacc..c7951adcebff 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 7bb67439bf6bd3782f07f1d7be1e63406453d5de
+refs/heads/master: df0cc0539b4127bd02f64de2c335b4af1fdb3845
diff --git a/trunk/include/linux/time.h b/trunk/include/linux/time.h
index e15206a7e82e..726976478480 100644
--- a/trunk/include/linux/time.h
+++ b/trunk/include/linux/time.h
@@ -38,6 +38,8 @@ struct timezone {
 #define NSEC_PER_SEC	1000000000L
 #define FSEC_PER_SEC	1000000000000000L
 
+#define TIME_T_MAX	(time_t)((1UL << ((sizeof(time_t) << 3) - 1)) - 1)
+
 static inline int timespec_equal(const struct timespec *a,
                                  const struct timespec *b)
 {
@@ -72,6 +74,8 @@ extern unsigned long mktime(const unsigned int year, const unsigned int mon,
 			    const unsigned int min, const unsigned int sec);
 
 extern void set_normalized_timespec(struct timespec *ts, time_t sec, long nsec);
+extern struct timespec timespec_add_safe(const struct timespec lhs,
+					 const struct timespec rhs);
 
 /*
  * sub = lhs - rhs, in normalized form
diff --git a/trunk/kernel/time.c b/trunk/kernel/time.c
index 6a08660b4fac..d63a4336fad6 100644
--- a/trunk/kernel/time.c
+++ b/trunk/kernel/time.c
@@ -669,3 +669,21 @@ EXPORT_SYMBOL(get_jiffies_64);
 #endif
 
 EXPORT_SYMBOL(jiffies);
+
+/*
+ * Add two timespec values and do a safety check for overflow.
+ * It's assumed that both values are valid (>= 0)
+ */
+struct timespec timespec_add_safe(const struct timespec lhs,
+				  const struct timespec rhs)
+{
+	struct timespec res;
+
+	set_normalized_timespec(&res, lhs.tv_sec + rhs.tv_sec,
+				lhs.tv_nsec + rhs.tv_nsec);
+
+	if (res.tv_sec < lhs.tv_sec || res.tv_sec < rhs.tv_sec)
+		res.tv_sec = TIME_T_MAX;
+
+	return res;
+}