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[PATCH v2 3/7] y2038: Provide conversion helpers for struct __timespec64


Those functions allow easy conversion between Y2038 safe struct
 __timespec64 and other time related data structures.

An inline function has been added to clear padding of struct
__timespec64. This function shall be used when Y2038 safe system
passes the data to Linux kernel (as it expects upper 32 bits of
tv_nsec being zeroed).

Moreover, those functions are NOT compiled when one runs 64 bit
system (the __TIMESIZE == 64) and are used only for 32 bit
wrappers (like __clock_gettime).

* include/time.h (valid_timeval_to_timespec64): Add.
* include/time.h (valid_timespec_to_timespec64): Likewise.
* include/time.h (valid_timespec64_to_timespec): Likewise.
* include/time.h (valid_timespec64_to_timeval): Likewise.
* include/time.h (IS_VALID_NANOSECONDS): Likewise.
* include/time.h (timespec_to_timespec64): Likewise.
* include/time.h (timespec64_to_timespec): Likewise.
* include/time.h (timespec64_to_timeval): Likewise.
* include/time.h (timespec64_clear_padding): Likewise.

---
Changes for v2:
- Add timespec64_clear_padding function
---
 include/time.h | 102 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 102 insertions(+)

diff --git a/include/time.h b/include/time.h
index 7540ac0f8b..9827d2f045 100644
--- a/include/time.h
+++ b/include/time.h
@@ -3,6 +3,7 @@
 
 #ifndef _ISOMAC
 # include <bits/types/locale_t.h>
+# include <stdbool.h>
 # include <endian.h>
 
 extern __typeof (strftime_l) __strftime_l;
@@ -177,5 +178,106 @@ extern double __difftime (time_t time1, time_t time0);
    actual clock ID.  */
 #define CLOCK_IDFIELD_SIZE	3
 
+/* Check whether T fits in time_t.  */
+static inline bool
+in_time_t_range (__time64_t t)
+{
+  time_t s = t;
+  return s == t;
+}
+
+# if __TIMESIZE != 64
+/* Set to zero the struct __timespec64's tv_pad.  */
+static inline void
+timespec64_clear_padding (const struct __timespec64 *tp)
+{
+  ((struct __timespec64*)tp)->tv_pad = 0;
+}
+/* Convert a known valid struct timeval into a struct __timespec64.  */
+static inline void
+valid_timeval_to_timespec64 (const struct timeval *tv32,
+			     struct __timespec64 *ts64)
+{
+  ts64->tv_sec = tv32->tv_sec;
+  ts64->tv_nsec = tv32->tv_usec * 1000;
+}
+
+/* Convert a known valid struct timespec into a struct __timespec64.  */
+static inline void
+valid_timespec_to_timespec64 (const struct timespec *ts32,
+			      struct __timespec64 *ts64)
+{
+  ts64->tv_sec = ts32->tv_sec;
+  ts64->tv_nsec = ts32->tv_nsec;
+  /* We only need to zero ts64->tv_pad if we pass it to the kernel.  */
+}
+
+/* Convert a known valid struct __timespec64 into a struct timespec.  */
+static inline void
+valid_timespec64_to_timespec (const struct __timespec64 *ts64,
+			      struct timespec *ts32)
+{
+  ts32->tv_sec = (time_t) ts64->tv_sec;
+  ts32->tv_nsec = ts64->tv_nsec;
+}
+
+/* Convert a known valid struct __timespec64 into a struct timeval.  */
+static inline void
+valid_timespec64_to_timeval (const struct __timespec64 *ts64,
+			     struct timeval *tv32)
+{
+  tv32->tv_sec = (time_t) ts64->tv_sec;
+  tv32->tv_usec = ts64->tv_nsec / 1000;
+}
+
+/* Check if a value lies with the valid nanoseconds range.  */
+#define IS_VALID_NANOSECONDS(ns) ((ns) >= 0 && (ns) <= 999999999)
+
+/* Check and convert a struct timespec into a struct __timespec64.  */
+static inline bool
+timespec_to_timespec64 (const struct timespec *ts32,
+                        struct __timespec64 *ts64)
+{
+  /* Check that ts32 holds a valid count of nanoseconds.  */
+  if (! IS_VALID_NANOSECONDS (ts32->tv_nsec))
+    return false;
+  /* All ts32 fields can fit in ts64, so copy them.  */
+  valid_timespec_to_timespec64 (ts32, ts64);
+  /* We only need to zero ts64->tv_pad if we pass it to the kernel.  */
+  return true;
+}
+
+/* Check and convert a struct __timespec64 into a struct timespec.  */
+static inline bool
+timespec64_to_timespec (const struct __timespec64 *ts64,
+                        struct timespec *ts32)
+{
+  /* Check that tv_nsec holds a valid count of nanoseconds.  */
+  if (! IS_VALID_NANOSECONDS (ts64->tv_nsec))
+    return false;
+  /* Check that tv_sec can fit in a __time_t.  */
+  if (! in_time_t_range (ts64->tv_sec))
+    return false;
+  /* All ts64 fields can fit in ts32, so copy them.  */
+  valid_timespec64_to_timespec (ts64, ts32);
+  return true;
+}
+
+/* Check and convert a struct __timespec64 into a struct timeval.  */
+static inline bool
+timespec64_to_timeval (const struct __timespec64 *ts64,
+                       struct timeval *tv32)
+{
+  /* Check that tv_nsec holds a valid count of nanoseconds.  */
+  if (! IS_VALID_NANOSECONDS (ts64->tv_nsec))
+    return false;
+  /* Check that tv_sec can fit in a __time_t.  */
+  if (! in_time_t_range (ts64->tv_sec))
+    return false;
+  /* All ts64 fields can fit in tv32, so copy them.  */
+  valid_timespec64_to_timeval (ts64, tv32);
+  return true;
+}
+# endif
 #endif
 #endif
-- 
2.11.0


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