[PATCH v2] tst: Add test for adjtime

[Lukasz Majewski <lukma@denx.de>]

This code provides test to check if time on target machine is properly
adjusted.
The time is altered only when cross-test-ssh.sh is executed with
--allow-time-setting flag.

As the delta added to clock is only 1 sec the original time is not
restored and further tests are executed with this bias.

It is important to note that adjtime() adjusts the system time with
small amounts in each second (it is in fact a wrapper on clock_adjtime
with modes = ADJ_OFFSET_SINGLESHOT). In other words some seconds
(may be a random value) needs to elapse until the required time offset
is added to the clock. It may take considerable time (in minutes) to
adjust clock by e.g. 1 second.

To handle that the struct timeval odelta is passed to adjtime (NULL,
&odelta) to get information of the still required delta to be added
to clock. This is done in loop until its members are equal to 0.

As a reference - CLOCK_MONOTONIC is used to check if CLOCK_REALTIME
has been adjusted. The difference between them is measured.

---
Changes for v2:
- Correct code indentation
---
 sysdeps/unix/sysv/linux/Makefile      |  3 +-
 sysdeps/unix/sysv/linux/tst-adjtime.c | 83 +++++++++++++++++++++++++++
 2 files changed, 85 insertions(+), 1 deletion(-)
 create mode 100644 sysdeps/unix/sysv/linux/tst-adjtime.c

diff --git a/sysdeps/unix/sysv/linux/Makefile b/sysdeps/unix/sysv/linux/Makefile
index ddc1e748e6..30c8629386 100644
--- a/sysdeps/unix/sysv/linux/Makefile
+++ b/sysdeps/unix/sysv/linux/Makefile
@@ -113,7 +113,8 @@ 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-ntp_gettime \
-	 tst-ntp_gettimex tst-sigtimedwait tst-futimes tst-lutimes
+	 tst-ntp_gettimex tst-sigtimedwait tst-futimes tst-lutimes \
+	 tst-adjtime
 
 # Test for the symbol version of fcntl that was replaced in glibc 2.28.
 ifeq ($(have-GLIBC_2.27)$(build-shared),yesyes)
diff --git a/sysdeps/unix/sysv/linux/tst-adjtime.c b/sysdeps/unix/sysv/linux/tst-adjtime.c
new file mode 100644
index 0000000000..4b24fcb890
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/tst-adjtime.c
@@ -0,0 +1,83 @@
+/* Test for adjtime.
+   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/time.h>
+#include <sys/timerfd.h>
+#include <support/check.h>
+#include <support/xunistd.h>
+#include <support/timespec.h>
+
+#define TIMEOUT (60*10)
+#define ADJTIME_LOOP_SLEEP 10000
+
+static int
+do_test (void)
+{
+  struct timespec tv_then, tv_now, tv_then_m, tv_now_m;
+  struct timeval delta, odelta;
+  int ret;
+
+  /* Check if altering target time is allowed.  */
+  if (getenv (SETTIME_ENV_NAME) == NULL)
+    FAIL_UNSUPPORTED ("adjtime is executed only when "\
+                      SETTIME_ENV_NAME" is set\n");
+
+  tv_then = xclock_now (CLOCK_REALTIME);
+  tv_then_m = xclock_now (CLOCK_MONOTONIC);
+
+  /* Setup time value to adjust - 1 sec. */
+  delta.tv_sec = 1;
+  delta.tv_usec = 0;
+
+  ret = adjtime (&delta, NULL);
+  if (ret == -1)
+    FAIL_EXIT1 ("adjtime failed: %m\n");
+
+  /* As adjtime adjust clock time gradually by some small percentage
+     of delta in each second one needs to check if this process has
+     been finished.  */
+  do
+    {
+      ret = adjtime (NULL, &odelta);
+      if (ret == -1)
+        FAIL_EXIT1 ("adjtime failed: %m\n");
+
+      ret = usleep (ADJTIME_LOOP_SLEEP);
+      if (ret != 0)
+        FAIL_EXIT1 ("usleep failed: %m\n");
+    }
+  while ( ! (odelta.tv_sec == 0 && odelta.tv_usec == 0));
+
+  tv_now = xclock_now (CLOCK_REALTIME);
+  tv_now_m = xclock_now (CLOCK_MONOTONIC);
+
+  /* Check if adjtime adjusted the system time.  */
+  struct timespec r = timespec_sub (tv_now, tv_then);
+  struct timespec r_m = timespec_sub (tv_now_m, tv_then_m);
+
+  struct timespec r_adjtime = timespec_sub (r, r_m);
+
+  TEST_COMPARE (support_timespec_check_in_range
+                ((struct timespec) { 1, 0 }, r_adjtime, 0.9, 1.1), 1);
+
+  return 0;
+}
+
+#include <support/test-driver.c>
-- 
2.20.1