[PATCH v2 1/2] tst: Add test for ntp_gettime

[Lukasz Majewski <lukma@denx.de>]

This code provides test to check if time on target machine is properly
read via ntp_gettime syscall.

---
Changes for v2:
- Check time before and after calling ntp_gettime{x} to avoid situation
  when seconds rollover between call to ntp_gettime and wrapper providing
  current time.
---
 sysdeps/unix/sysv/linux/Makefile          |  2 +-
 sysdeps/unix/sysv/linux/tst-ntp_gettime.c | 56 +++++++++++++++++++++++
 2 files changed, 57 insertions(+), 1 deletion(-)
 create mode 100644 sysdeps/unix/sysv/linux/tst-ntp_gettime.c

diff --git a/sysdeps/unix/sysv/linux/Makefile b/sysdeps/unix/sysv/linux/Makefile
index b8c1caa505..8a07870cb4 100644
--- a/sysdeps/unix/sysv/linux/Makefile
+++ b/sysdeps/unix/sysv/linux/Makefile
@@ -113,7 +113,7 @@ tests += tst-clone tst-clone2 tst-clone3 tst-fanotify tst-personality \
 	 tst-tgkill tst-sysvsem-linux tst-sysvmsg-linux tst-sysvshm-linux \
 	 tst-timerfd tst-ppoll tst-futimens tst-utime tst-utimes \
 	 tst-clock_adjtime tst-adjtimex tst-ntp_adjtime tst-futimes \
-	 tst-lutimes
+	 tst-lutimes tst-ntp_gettime
 tests-internal += tst-ofdlocks-compat tst-sigcontext-get_pc
 tests-time64 += \
   tst-futimes-time64\
diff --git a/sysdeps/unix/sysv/linux/tst-ntp_gettime.c b/sysdeps/unix/sysv/linux/tst-ntp_gettime.c
new file mode 100644
index 0000000000..6cd3a0ec2c
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/tst-ntp_gettime.c
@@ -0,0 +1,56 @@
+/* Test for ntp_gettime
+   Copyright (C) 2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <time.h>
+#include <stdlib.h>
+#include <sys/timex.h>
+#include <support/check.h>
+#include <support/xtime.h>
+
+#ifndef NTP_GETTIME_SYSCALL
+# define NTP_GETTIME_SYSCALL ntp_gettime
+#endif
+
+#define STR(__s) #__s
+
+static int
+do_test (void)
+{
+  struct timespec tv_before_ntp, tv_after_ntp;
+  struct ntptimeval ntv;
+
+  /* To prevent seconds rollover (which is very unlikely though),
+     loop until we do match seconds values before and after
+     call to ntp_gettime.  */
+  do {
+    tv_before_ntp = xclock_now (CLOCK_REALTIME);
+
+    int ret = NTP_GETTIME_SYSCALL (&ntv);
+    if (ret == -1)
+      FAIL_EXIT1 (STR(NTP_GETTIME_SYSCALL)" failed: %m\n");
+
+    tv_after_ntp = xclock_now (CLOCK_REALTIME);
+  } while (tv_after_ntp.tv_sec != tv_before_ntp.tv_sec);
+
+  if (tv_after_ntp.tv_sec != ntv.time.tv_sec)
+    FAIL_EXIT1 (STR(NTP_GETTIME_SYSCALL)" provided wrong time!\n");
+
+  return 0;
+}
+
+#include <support/test-driver.c>
-- 
2.20.1