[PATCH v3 7/7] y2038: linux: Provide ___gettimeofday64 implementation

[Lukasz Majewski]

In the glibc the gettimeofday can use vDSO (on power and x86 the
USE_IFUNC_GETTIMEOFDAY is defined), gettimeofday syscall or 'default'
___gettimeofday() from ./time/gettime.c (as a fallback).

In this patch the last function (___gettimeofday) has been reimplemented and
moved to ./sysdeps/unix/sysv/linux/gettimeofday.c to be Linux specific.

The new ___gettimeofday64 explicit 64 bit function for getting 64 bit time from
the kernel (by internally calling __clock_gettime64) has been introduced.

Moreover, a 32 bit version - ___gettimeofday has been refactored to internally
use __gettimeofday64.

The ___gettimeofday is now supposed to be used on systems still supporting 32
bit time (__TIMESIZE != 64) - hence the necessary check for time_t potential
overflow and conversion of struct __timeval64 to 32 bit struct timespec.

The alpha port is a bit problematic for this change - it supports 64 bit time
and can safely use gettimeofday implementation from ./time/gettimeofday.c as it
has ./sysdeps/unix/sysv/linux/alpha/gettimeofday.c, which includes
./time/gettimeofday.c, so the Linux specific one can be avoided.
For that reason the code to set default gettimeofday symbol has not been moved
to ./sysdeps/unix/sysv/linux/gettimeofday.c as only alpha defines
VERSION_gettimeofday.


Build tests:
./src/scripts/build-many-glibcs.py glibcs

Run-time tests:
- 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

Above tests were performed with Y2038 redirection applied as well as without
to test proper usage of both ___gettimeofday64 and __gettimeofday.

---
Changes for v3:
- New patch
---
 include/time.h                         |  4 +++
 sysdeps/unix/sysv/linux/gettimeofday.c | 46 +++++++++++++++++++++++++-
 2 files changed, 49 insertions(+), 1 deletion(-)

diff --git a/include/time.h b/include/time.h
index 0345803db2..931c9a3bd7 100644
--- a/include/time.h
+++ b/include/time.h
@@ -227,10 +227,14 @@ libc_hidden_proto (__sched_rr_get_interval64);
 
 #if __TIMESIZE == 64
 # define __settimeofday64 __settimeofday
+# define ___gettimeofday64 ___gettimeofday
 #else
 extern int __settimeofday64 (const struct __timeval64 *tv,
                              const struct timezone *tz);
 libc_hidden_proto (__settimeofday64)
+extern int ___gettimeofday64 (struct __timeval64 *restrict tv,
+                              void *restrict tz);
+libc_hidden_proto (___gettimeofday64)
 #endif
 
 /* Compute the `struct tm' representation of T,
diff --git a/sysdeps/unix/sysv/linux/gettimeofday.c b/sysdeps/unix/sysv/linux/gettimeofday.c
index d5cdb22495..728ef45eed 100644
--- a/sysdeps/unix/sysv/linux/gettimeofday.c
+++ b/sysdeps/unix/sysv/linux/gettimeofday.c
@@ -54,5 +54,49 @@ __gettimeofday (struct timeval *restrict tv, void *restrict tz)
 # endif
 weak_alias (__gettimeofday, gettimeofday)
 #else /* USE_IFUNC_GETTIMEOFDAY  */
-# include <time/gettimeofday.c>
+/* Conversion of gettimeofday function to support 64 bit time on archs
+   with __WORDSIZE == 32 and __TIMESIZE == 32/64  */
+#include <errno.h>
+
+int
+___gettimeofday64 (struct __timeval64 *restrict tv, void *restrict tz)
+{
+  if (__glibc_unlikely (tz != 0))
+    memset (tz, 0, sizeof (struct timezone));
+
+  struct __timespec64 ts64;
+  int ret = __clock_gettime64 (CLOCK_REALTIME, &ts64);
+
+  if (ret == 0 && tv)
+    *tv = timespec64_to_timeval64 (ts64);
+
+  return ret;
+}
+
+# if __TIMESIZE != 64
+libc_hidden_def (___gettimeofday64)
+
+int
+___gettimeofday (struct timeval *restrict tv, void *restrict tz)
+{
+  struct __timeval64 tv64;
+  int ret = ___gettimeofday64 (&tv64, tz);
+
+  if (ret == 0)
+    {
+      if (! in_time_t_range (tv64.tv_sec))
+        {
+          __set_errno (EOVERFLOW);
+          return -1;
+        }
+
+      if (tv)
+        *tv = valid_timeval64_to_timeval (tv64);
+    }
+
+  return ret;
+}
+# endif
+strong_alias (___gettimeofday, __gettimeofday)
+weak_alias (___gettimeofday, gettimeofday)
 #endif
-- 
2.20.1