y2038: linux: Provide __clock_settime64 implementation

This patch provides new __clock_settime64 explicit 64 bit function for
setting the time. Moreover, a 32 bit version - __clock_settime has been
refactored to internally use __clock_settime64.

The __clock_settime is now supposed to be used on 32 bit systems -
hence the necessary checks and conversion to 64 bit type. After this
change it is intrinsically Y2038 safe.

The new 64 bit syscall (clock_settime64) available from Linux
5.1+ has been used when applicable on 32 bit systems.
The execution path on 64 bit systems has not been changed or affected in
any way.

Tests:
- The code has been tested with x86_64/x86 (native compilation):
make PARALLELMFLAGS="-j8" && make xcheck PARALLELMFLAGS="-j8"

- Run specific tests on ARM/x86 32bit systems (qemu):
https://github.com/lmajewski/meta-y2038
and run tests:
https://github.com/lmajewski/y2038-tests/commits/master
on kernels with and without 64 bit time support.

No regressions were observed.

* include/time.h (__clock_settime64):
  Add __clock_settime alias according to __TIMESIZE define
* sysdeps/unix/sysv/linux/clock_settime.c (__clock_settime):
  Refactor this function to be used only on 32 bit machines as a wrapper
  on __clock_settime64.
* sysdeps/unix/sysv/linux/clock_settime.c (__clock_settime64): Add
* sysdeps/unix/sysv/linux/clock_settime.c (__clock_settime64):
  Use clock_settime64 kernel syscall (available from 5.1-rc1+ Linux) by
  32 bit Y2038 safe systems

include/time.h

@@ -124,6 +124,14 @@ extern __time64_t __timegm64 (struct tm *__tp) __THROW;
 libc_hidden_proto (__timegm64)
 #endif
 
+#if __TIMESIZE == 64
+# define __clock_settime64 __clock_settime
+#else
+extern int __clock_settime64 (clockid_t clock_id,
+                              const struct __timespec64 *tp);
+libc_hidden_proto (__clock_settime64)
+#endif
+
 /* Compute the `struct tm' representation of T,
    offset OFFSET seconds east of UTC,
    and store year, yday, mon, mday, wday, hour, min, sec into *TP.

sysdeps/unix/sysv/linux/clock_settime.c

@@ -19,11 +19,9 @@
 #include <sysdep.h>
 #include <time.h>
 
-#include "kernel-posix-cpu-timers.h"
-
 /* Set CLOCK to value TP.  */
 int
-__clock_settime (clockid_t clock_id, const struct timespec *tp)
+__clock_settime64 (clockid_t clock_id, const struct __timespec64 *tp)
 {
   /* Make sure the time cvalue is OK.  */
   if (tp->tv_nsec < 0 || tp->tv_nsec >= 1000000000)
@@ -32,6 +30,36 @@ __clock_settime (clockid_t clock_id, const struct timespec *tp)
       return -1;
     }
 
+#if defined (__TIMESIZE) && __TIMESIZE != 64
+# if defined __NR_clock_settime64
+  /* Make sure that passed __timespec64 struct pad is 0.  */
+  struct __timespec64 ts = *tp;
+  ts.tv_pad = 0;
+  return INLINE_SYSCALL_CALL (clock_settime64, clock_id, &ts);
+# else
+  struct timespec ts32;
+  valid_timespec64_to_timespec(tp, &ts32);
+  return INLINE_SYSCALL_CALL (clock_settime, clock_id, &ts32);
+# endif
+#else
   return INLINE_SYSCALL_CALL (clock_settime, clock_id, tp);
+#endif
 }
 weak_alias (__clock_settime, clock_settime)
+
+#if __TIMESIZE != 64
+int
+__clock_settime (clockid_t clock_id, const struct timespec *tp)
+{
+  struct __timespec64 ts64;
+
+  if (! in_time_t_range (tp->tv_sec))
+    {
+      __set_errno (EOVERFLOW);
+      return -1;
+    }
+
+  valid_timespec_to_timespec64 (tp, &ts64);
+  return __clock_settime64 (clock_id, &ts64);
+}
+#endif