test/data: add mount_flags.py helper script

Add a new helper script to check if a mount / file-system was
mounted with specific flags. Currently only "ro", "nosuid",
"nodev" and "noexec" flags are supported. This script is in
test/data since it will be used from other tests and is itself
not a test per se.

test/data/README.md

@@ -41,3 +41,7 @@ do not allow comments, this file shortly describes their purpose.
    This directory contains test-data for runtime tests of the source-engines. It
    contains a directory that is served via HTTP in the tests, and a directory of
    test-cases what to expect when using the attached `sources.json`.
+
+ * `scripts`:
+   This directory contains scripts used from other tests, i.e. although they are
+   executables they are at the same time test-data to the actual (unit) tests.

test/data/scripts/mount_flags.py

@@ -0,0 +1,50 @@
+#!/usr/bin/python3
+#
+# Small script that returns 0 if all the requested mount flags
+# are present for a given mount and returns 1 otherwise
+
+import argparse
+import os
+import sys
+
+
+# from /usr/include/sys/mount.h
+# these are file-system independent
+MS_RDONLY = 1
+MS_NOSUID = 2
+MS_NODEV = 4
+MS_NOEXEC = 8
+
+KNOWN_FLAGS = {
+    "ro": MS_RDONLY,
+    "nosuid": MS_NOSUID,
+    "nodev": MS_NODEV,
+    "noexec": MS_NOEXEC
+}
+
+
+def main():
+    parser = argparse.ArgumentParser(description="Check for mount flags")
+    parser.add_argument("path", metavar="PATH",
+                        help="path for the file-system to check for read-only status")
+    parser.add_argument("flags", metavar="FLAGS",
+                        help="comma separated list of flags to check for")
+    args = parser.parse_args(sys.argv[1:])
+
+    want = 0
+    strflags = [x.strip() for x in args.flags.split(",")]
+    for flag in strflags:
+        num = KNOWN_FLAGS.get(flag, None)
+        if flag is None:
+            print(f"Unknown flag: '{flag}'")
+            sys.exit(2)
+        want |= num
+
+    sb = os.statvfs(args.path)
+    have = sb.f_flag
+    ok = (have & want) == want
+    sys.exit(0 if ok else 1)
+
+
+if __name__ == "__main__":
+    main()