test: XFAIL lockmem test if rawtp-arg-type uses CTF

To get rawtp arg types, we rely on CTF.  If CTF info is not available,
we fall back on a "trial and error" method simply for the number of args.
But we signal to the user if the trial-and-error method is failing due
to lockmem limits.

This test checked for that failure mode.  The test was skipped if
lockmem limits are not observed on the test system.

Skip the test also if CTF info *IS* available.

Signed-off-by: Eugene Loh <eugene.loh@oracle.com>
Reviewed-by: Kris Van Hees <kris.van.hees@oracle.com>

test/unittest/providers/rawtp/err.lockmem-too-low.r

@@ -0,0 +1,4 @@
+dtrace: invalid probe specifier rawtp:::sched_process_fork: Cannot retrieve argument count:
+	The kernel locked-memory limit is possibly too low.  Set a
+	higher limit with the DTrace option '-xlockmem=N'.  Or, use
+	'ulimit -l N' (Kbytes).  Or, make N the string 'unlimited'.

test/unittest/providers/rawtp/err.lockmem-too-low.sh

@@ -1,11 +1,23 @@
 #!/bin/bash
 #
 # Oracle Linux DTrace.
-# Copyright (c) 2021, Oracle and/or its affiliates. All rights reserved.
+# Copyright (c) 2023, Oracle and/or its affiliates. All rights reserved.
 # Licensed under the Universal Permissive License v 1.0 as shown at
 # http://oss.oracle.com/licenses/upl.
 #
 
+# The mechanism for discovering rawtp arg types relies first on CTF.
+# If CTF information is not available, we fall back to a "trial-and-error"
+# method, which really only tells us the number of args.  And that
+# method simply cannot work if trials error due to lockmem limits.
+# If lockmem limits are encountered, we want to signal that problem to the
+# user.
+#
+# This test checks that failure mode.  Therefore, two conditions
+# must be met for this test to work.  First, lockmem limits must be
+# respected.  Second, no CTF information should be available, so that
+# the trial-and-error method will be invoked.
+
 dtrace=$1
 
 # Determine whether the system respects setting the lockmem limit as root.
@@ -16,9 +28,28 @@ if $dtrace -xlockmem=1 -n 'BEGIN { exit(0); }' &> /dev/null; then
 fi
 
 $dtrace -xlockmem=1 -lvn rawtp:::sched_process_fork |& \
-    awk '{ print; }
+    awk 'BEGIN {
+	     err = 0;  # lockmem error messages
+	     CTF = 0;  # arg types indicating CTF info
+	     try = 0;  # arg types indicating trial-and-error
+	 }
+
+	 { print; }
+
 	 /Cannot retrieve argument count/ { err++; }
 	 /lockmem/ { err++; }
-	 END { exit(err == 2 ? 1 : 0); }'
+	 /^	*args\[[01]\]: struct task_struct \*$/ { CTF++ }
+	 /^	*args\[[01]\]: uint64_t$/ { try++ }
+
+	 END {
+	     # Skip this test if CTF info was found.
+	     if (err == 0 && CTF == 2 && try == 0) exit(67);
+
+	     # Report the expected fail if error message is found.
+	     if (err == 2 && CTF == 0 && try == 0) exit(1);
+
+	     # Indicate the expected fail did not occur.
+	     exit(0);
+	 }'
 
 exit $?