[glibc/azanella/y2038] support: Provide xclock_settime test helper function

[Adhemerval Zanella <azanella@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=9a6b42a1501f25f3c205a5d818c1d63e3c467c2b

commit 9a6b42a1501f25f3c205a5d818c1d63e3c467c2b
Author: Lukasz Majewski <lukma@denx.de>
Date:   Mon Jan 18 16:53:26 2021 +0100

    support: Provide xclock_settime test helper function
    
    The xclock_settime is a wrapper function on the clock_settime syscall
    to be used in the test code.
    
    It checks if the GLIBC_TEST_ALLOW_TIME_SETTING env variable is defined
    in the environment in which test is executed. If it is not - the test
    ends as unsupported. Otherwise, the clock-settime is executed and return
    value is assessed.

Diff:
---
 support/Makefile         |  1 +
 support/xclock_settime.c | 35 +++++++++++++++++++++++++++++++++++
 support/xtime.h          |  5 +++++
 3 files changed, 41 insertions(+)

diff --git a/support/Makefile b/support/Makefile
index bb9889efb4..8d63fbd5da 100644
--- a/support/Makefile
+++ b/support/Makefile
@@ -90,6 +90,7 @@ libsupport-routines = \
   xchdir \
   xchroot \
   xclock_gettime \
+  xclock_settime \
   xclose \
   xchmod \
   xconnect \
diff --git a/support/xclock_settime.c b/support/xclock_settime.c
new file mode 100644
index 0000000000..12a83b9d79
--- /dev/null
+++ b/support/xclock_settime.c
@@ -0,0 +1,35 @@
+/* clock_settime with error checking.
+   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 <stdlib.h>
+#include <support/check.h>
+#include <support/xtime.h>
+#include <support/xthread.h>
+
+void
+xclock_settime (clockid_t clockid,
+                const struct timespec *ts)
+{
+  if (getenv (SETTIME_ENV_NAME) == NULL)
+    FAIL_UNSUPPORTED ("clock_settime is executed only when "\
+                      SETTIME_ENV_NAME" is set\n");
+
+  const int ret = clock_settime (clockid, ts);
+  if (ret < 0)
+    FAIL_EXIT1 ("clock_settime (%d): %m", clockid);
+}
diff --git a/support/xtime.h b/support/xtime.h
index 2482837dee..b4ac3b59e2 100644
--- a/support/xtime.h
+++ b/support/xtime.h
@@ -23,10 +23,15 @@
 
 __BEGIN_DECLS
 
+/* Name of the env variable, which indicates if it is possible to
+   adjust time on target machine.  */
+#define SETTIME_ENV_NAME "GLIBC_TEST_ALLOW_TIME_SETTING"
+
 /* The following functions call the corresponding libc functions and
    terminate the process on error.  */
 
 void xclock_gettime (clockid_t clock, struct timespec *ts);
+void xclock_settime (clockid_t clock, const struct timespec *ts);
 
 /* This helper can often simplify tests by avoiding an explicit
    variable declaration or allowing that declaration to be const. */