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

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

include/linux/time.h

+4 −0
Original line number Original line Diff line number Diff line
@@ -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, 
			    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

kernel/time.c

+18 −0
Original line number Original line Diff line number Diff line
@@ -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;

}