Patchwork [v5,2/3] y2038: Provide conversion helpers for struct __timespec64

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Submitter Lukasz Majewski
Date May 29, 2019, 4:18 p.m.
Message ID <20190529161850.30442-3-lukma@denx.de>
Download mbox | patch
Permalink /patch/32899/
State New
Headers show

Comments

Lukasz Majewski - May 29, 2019, 4:18 p.m.
Those functions allow easy conversion between Y2038 safe struct
__timespec64 and other time related data structures (like struct timeval).

Moreover, those functions are NOT compiled when 64 bit time support is
enabled (i.e. the __ASSUME_TIME64_SYSCALLS is defined) and are used only
in 32 bit wrappers (like e.g. __clock_settime()).

* 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.

---
Changes for v5:
- This code is now only compiled in when __ASSUME_TIME64_SYSCALLS is NOT
  defined. Previously it was depending on #if __TIMESIZE != 64.

Changes for v4:
- None

Changes for v3:
- Remove misleading comments regarding clearing tv_pad values during
  conversion (as Linux kernel on its own ignores upper 32 bits of tv_nsec).

Changes for v3:
- Remove timespec64_clear_padding function - as kernel ignores upper 32
  bits of tv_nsec when passed via syscall to the Linux kernel

Changes for v2:
- Add timespec64_clear_padding function
---
 include/time.h | 85 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 85 insertions(+)
Stepan Golosunov - May 31, 2019, 11:47 a.m.
29.05.2019 в 18:18:49 +0200 Lukasz Majewski написал:
> Those functions allow easy conversion between Y2038 safe struct
> __timespec64 and other time related data structures (like struct timeval).
> 
> Moreover, those functions are NOT compiled when 64 bit time support is
> enabled (i.e. the __ASSUME_TIME64_SYSCALLS is defined) and are used only
> in 32 bit wrappers (like e.g. __clock_settime()).


> Changes for v5:
> - This code is now only compiled in when __ASSUME_TIME64_SYSCALLS is NOT
>   defined. Previously it was depending on #if __TIMESIZE != 64.

That's wrong.  valid_timespec_to_timespec64 is used when __TIMESIZE !=
64.  Even when __ASSUME_TIME64_SYSCALLS is defined.

And when __ASSUME_TIME64_SYSCALLS is not defined __TIMESIZE should be
32.  (Supporting __TIMESIZE == 64 without __ASSUME_TIME64_SYSCALLS is
a bad idea.)

Also, it doesn't look like __ASSUME_TIME64_SYSCALLS can be defined by
any header included from include/time.h.
Lukasz Majewski - June 3, 2019, 9:18 a.m.
Hi Stepan,

> 29.05.2019 в 18:18:49 +0200 Lukasz Majewski написал:
> > Those functions allow easy conversion between Y2038 safe struct
> > __timespec64 and other time related data structures (like struct
> > timeval).
> > 
> > Moreover, those functions are NOT compiled when 64 bit time support
> > is enabled (i.e. the __ASSUME_TIME64_SYSCALLS is defined) and are
> > used only in 32 bit wrappers (like e.g. __clock_settime()).  
> 
> 
> > Changes for v5:
> > - This code is now only compiled in when __ASSUME_TIME64_SYSCALLS
> > is NOT defined. Previously it was depending on #if __TIMESIZE !=
> > 64.  
> 
> That's wrong.  valid_timespec_to_timespec64 is used when __TIMESIZE !=
> 64.  Even when __ASSUME_TIME64_SYSCALLS is defined.

Hmm.. Then I think that I should have kept [1]:

#if __TIMESIZE != 64

(helper functions)

#endif

> 
> And when __ASSUME_TIME64_SYSCALLS is not defined __TIMESIZE should be
> 32.  (Supporting __TIMESIZE == 64 without __ASSUME_TIME64_SYSCALLS is
> a bad idea.)

The above assumption is implicit. When __ASSUME_TIME64_SYSCALLS is
defined 64 bit versions of syscalls are used and hence we don't need
the conversion.

Shall I add more formalism here or just use #ifdef from [1] ?

> 
> Also, it doesn't look like __ASSUME_TIME64_SYSCALLS can be defined by
> any header included from include/time.h.

Ok.


Best regards,

Lukasz Majewski

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Patch

diff --git a/include/time.h b/include/time.h
index 33d0fcb0fe..1b38d019c8 100644
--- a/include/time.h
+++ b/include/time.h
@@ -181,5 +181,90 @@  in_time_t_range (__time64_t t)
   return s == t;
 }
 
+# ifndef __ASSUME_TIME64_SYSCALLS
+/* 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;
+}
+
+/* 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);
+  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