Commit df0cc053 authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Arjan van de Ven

select: add a timespec_add_safe() function

For the select() rework, it's important to be able to add timespec
structures in an overflow-safe manner.

This patch adds a timespec_add_safe() function for this which is similar in
operation to ktime_add_safe(), but works on a struct timespec.
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarArjan van de Ven <arjan@linux.intel.com>
parent 7bb67439
...@@ -38,6 +38,8 @@ struct timezone { ...@@ -38,6 +38,8 @@ struct timezone {
#define NSEC_PER_SEC 1000000000L #define NSEC_PER_SEC 1000000000L
#define FSEC_PER_SEC 1000000000000000L #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, static inline int timespec_equal(const struct timespec *a,
const struct timespec *b) const struct timespec *b)
{ {
...@@ -72,6 +74,8 @@ extern unsigned long mktime(const unsigned int year, const unsigned int mon, ...@@ -72,6 +74,8 @@ extern unsigned long mktime(const unsigned int year, const unsigned int mon,
const unsigned int min, const unsigned int sec); const unsigned int min, const unsigned int sec);
extern void set_normalized_timespec(struct timespec *ts, time_t sec, long nsec); 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 * sub = lhs - rhs, in normalized form
......
...@@ -669,3 +669,21 @@ EXPORT_SYMBOL(get_jiffies_64); ...@@ -669,3 +669,21 @@ EXPORT_SYMBOL(get_jiffies_64);
#endif #endif
EXPORT_SYMBOL(jiffies); 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;
}
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