[PATCH v3 2/2] sysdeps/clock_gettime: Use clock_gettime64 if avaliable

[Alistair Francis <alistair dot francis at wdc dot com>]

With the clock_gettime64 call we prefer to use vDSO. There is no call
to clock_gettime64 on glibc with older headers and kernel 5.1+ if it
doesn't support vDSO.
---
This was patch was runtime tested with RV32 and RV64
It was build tested using the ./scripts/build-many-glibcs.py script.

I also ran:
$ make ; make install ; make check
tests on native ARM (32-bit) with the following three confiugrations:
 - 4.19 Kernel and 4.19 Headers
 - 5.2 Kernel and 4.19 Headers
 - 5.2 Kernel and 5.2 Headers
and didn't see any regressions

v3:
 - Assume HAVE_CLOCK_GETTIME64_VSYSCALL means we have __NR_clock_gettime64
 - Change code style to be more glibc-ish
v2:
 - Add commit message
 - Change ret_64 to int

 include/time.h                          |  3 ++
 sysdeps/unix/sysv/linux/clock_gettime.c | 44 ++++++++++++++++++++++++-
 2 files changed, 46 insertions(+), 1 deletion(-)

diff --git a/include/time.h b/include/time.h
index d7800eb30f..c19c73ae09 100644
--- a/include/time.h
+++ b/include/time.h
@@ -211,11 +211,14 @@ extern double __difftime (time_t time1, time_t time0);
 
 #if __TIMESIZE == 64
 # define __clock_nanosleep_time64 __clock_nanosleep
+# define __clock_gettime64 __clock_gettime
 #else
 extern int __clock_nanosleep_time64 (clockid_t clock_id,
                                      int flags, const struct __timespec64 *req,
                                      struct __timespec64 *rem);
 libc_hidden_proto (__clock_nanosleep_time64)
+extern int __clock_gettime64 (clockid_t clock_id, struct __timespec64 *tp);
+libc_hidden_proto (__clock_gettime64)
 #endif
 
 /* Use in the clock_* functions.  Size of the field representing the
diff --git a/sysdeps/unix/sysv/linux/clock_gettime.c b/sysdeps/unix/sysv/linux/clock_gettime.c
index ca40983f6c..875c4fe905 100644
--- a/sysdeps/unix/sysv/linux/clock_gettime.c
+++ b/sysdeps/unix/sysv/linux/clock_gettime.c
@@ -17,6 +17,7 @@
    <https://www.gnu.org/licenses/>.  */
 
 #include <sysdep.h>
+#include <kernel-features.h>
 #include <errno.h>
 #include <time.h>
 #include "kernel-posix-cpu-timers.h"
@@ -30,10 +31,51 @@
 
 /* Get current value of CLOCK and store it in TP.  */
 int
+__clock_gettime64 (clockid_t clock_id, struct __timespec64 *tp)
+{
+#ifdef __ASSUME_TIME64_SYSCALLS
+# ifndef __NR_clock_gettime64
+#  define __NR_clock_gettime64   __NR_clock_gettime
+#  define __vdso_clock_gettime64 __vdso_clock_gettime
+# endif
+   return INLINE_VSYSCALL (clock_gettime64, 2, clock_id, tp);
+#else
+# if defined HAVE_CLOCK_GETTIME64_VSYSCALL
+  int ret64 = INLINE_VSYSCALL (clock_gettime64, 2, clock_id, tp);
+  if (ret64 == 0 || errno != ENOSYS)
+    return ret64;
+# endif
+  struct timespec tp32;
+  int ret = INLINE_VSYSCALL (clock_gettime, 2, clock_id, &tp32);
+  if (ret == 0)
+    *tp = valid_timespec_to_timespec64 (tp32);
+  return ret;
+#endif
+}
+
+#if __TIMESIZE != 64
+int
 __clock_gettime (clockid_t clock_id, struct timespec *tp)
 {
-  return INLINE_VSYSCALL (clock_gettime, 2, clock_id, tp);
+  int ret;
+  struct __timespec64 tp64;
+
+  ret = __clock_gettime64 (clock_id, &tp64);
+
+  if (ret == 0)
+    {
+      if (! in_time_t_range (tp64.tv_sec))
+        {
+          __set_errno (EOVERFLOW);
+          return -1;
+        }
+
+      *tp = valid_timespec64_to_timespec (tp64);
+    }
+
+  return ret;
 }
+#endif
 libc_hidden_def (__clock_gettime)
 
 versioned_symbol (libc, __clock_gettime, clock_gettime, GLIBC_2_17);
-- 
2.24.0