selftests/ftrace: Add dynamic events argument limitation test case

Add argument limitation test case for dynamic events.
This is a boudary check for the maximum number of the probe
event arguments.

Link: https://lore.kernel.org/all/174055078295.4079315.14702008939511417359.stgit@mhiramat.tok.corp.google.com/

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>

Author: mhiramat

tools/testing/selftests/ftrace/test.d/dynevent/dynevent_limitations.tc

@@ -0,0 +1,42 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+# description: Checking dynamic events limitations
+# requires: dynamic_events "imm-value":README
+
+# Max arguments limitation
+MAX_ARGS=128
+EXCEED_ARGS=$((MAX_ARGS + 1))
+
+check_max_args() { # event_header
+  TEST_STRING=$1
+  # Acceptable
+  for i in `seq 1 $MAX_ARGS`; do
+    TEST_STRING="$TEST_STRING \\$i"
+  done
+  echo "$TEST_STRING" >> dynamic_events
+  echo > dynamic_events
+  # Error
+  TEST_STRING="$TEST_STRING \\$EXCEED_ARGS"
+  ! echo "$TEST_STRING" >> dynamic_events
+  return 0
+}
+
+# Kprobe max args limitation
+if grep -q "kprobe_events" README; then
+  check_max_args "p vfs_read"
+fi
+
+# Fprobe max args limitation
+if grep -q "f[:[<group>/][<event>]] <func-name>[%return] [<args>]" README; then
+  check_max_args "f vfs_read"
+fi
+
+# Tprobe max args limitation
+if grep -q "t[:[<group>/][<event>]] <tracepoint> [<args>]" README; then
+  check_max_args "t kfree"
+fi
+
+# Uprobe max args limitation
+if grep -q "uprobe_events" README; then
+  check_max_args "p /bin/sh:10"
+fi