8359593: JFR: Instrumentation of java.lang.String corrupts recording

Reviewed-by: mgronlun
Backport-of: 2f2acb2

Author: egahlin

src/jdk.jfr/share/classes/jdk/jfr/internal/tracing/ExcludeList.java

@@ -24,38 +24,46 @@
  */
 package jdk.jfr.internal.tracing;
 
+import java.util.Set;
+
 // // The JVM will skip all classes in the jdk.jfr module, so it's not added here.
 public final class ExcludeList {
     private static final String[] EXCLUDED_CLASSES = {
         // Used by MethodTiming event to accumulate invocations.
         "java/util/concurrent/atomic/AtomicLong",
-        // Used by EventWriter
+        // Used by EventWriter, directly or indirectly.
         "sun/misc/Unsafe",
-        "jdk/internal/misc/Unsafe;",
+        "jdk/internal/misc/Unsafe",
+        "java/lang/StringLatin1",
+        "java/lang/StringUTF16",
     };
 
     private static final String[] EXCLUDED_PREFIX = {
         // Used by MethodTiming event to store invocations, including inner classes.
         "java/util/concurrent/ConcurrentHashMap",
         // Can't trigger <clinit> of these classes during PlatformTracer::onMethodTrace(...)
-        "jdk/internal/", // jdk/internal/classfile, jdk/internal/loader and jdk/internal/foreign
+        // Also to avoid recursion with EventWriter::putString
+        "jdk/internal/", // jdk/internal/classfile, // jdk/internal/vm, jdk/internal/util, jdk/internal/loader and jdk/internal/foreign
         "java/lang/classfile/"
     };
 
-    private static final String[] EXCLUDED_METHODS = {
+    private static final Set<String> EXCLUDED_METHODS = Set.of(
         // Long used by MethodTiming event when looking up entry for timing entry
         "java.lang.Long::<init>",
         "java.lang.Long::valueOf",
-        "java.lang.Number::<init>"
-    };
+        "java.lang.Number::<init>",
+        // Used by EventWriter::putString, directly or indirectly.
+        "java.lang.String::charAt",
+        "java.lang.String::length",
+        "java.lang.String::coder", // Used by charAt(int)
+        "java.lang.String::checkIndex", // Used by charAt(int)
+        "java.lang.String::isLatin1", // Used by charAt()
+        "java.lang.String::equals", // Used by StringPool
+        "java.lang.String::hashCode" // Used by StringPool
+    );
 
     public static boolean containsMethod(String methodName) {
-        for (String method : EXCLUDED_METHODS) {
-            if (method.equals(methodName)) {
-                return true;
-            }
-        }
-        return false;
+        return EXCLUDED_METHODS.contains(methodName);
     }
 
     public static boolean containsClass(String className) {

test/jdk/jdk/jfr/event/tracing/TestTracedString.java

@@ -0,0 +1,97 @@
+/*
+ * Copyright (c) 2025, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code 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 General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+package jdk.jfr.event.tracing;
+
+import java.nio.file.Path;
+
+import jdk.jfr.Configuration;
+import jdk.jfr.Name;
+import jdk.jfr.Recording;
+import jdk.jfr.consumer.RecordedEvent;
+import jdk.jfr.consumer.RecordingFile;
+
+/**
+ * @test
+ * @summary Tests that java.lang.String can be traced.
+ * @requires vm.flagless
+ * @requires vm.hasJFR
+ * @library /test/lib
+ * @run main/othervm jdk.jfr.event.tracing.TestTracedString
+ **/
+public class TestTracedString {
+    private static long SEED = System.currentTimeMillis();
+
+    @Name("Message")
+    static class MessageEvent extends jdk.jfr.Event {
+        String message;
+        long checkSum;
+    }
+
+    public static void main(String[] args) throws Exception {
+        Configuration c = Configuration.getConfiguration("default");
+        Path file = Path.of("recording.jfr");
+        try (Recording r = new Recording(c)) {
+            r.enable("jdk.MethodTrace").with("filter", "java.lang.String");
+            r.start();
+            emit(100, "");
+            emit(100, "short");
+            emit(100, "medium medium medium medium medium medium 1");
+            emit(100, "medium medium medium medium medium medium 2");
+            emit(100, "long".repeat(100));
+            r.stop();
+            r.dump(file);
+            int count = 0;
+            for (RecordedEvent e : RecordingFile.readAllEvents(file)) {
+                if (e.getEventType().getName().equals("Message")) {
+                    String text = e.getString("message");
+                    long checkSum = e.getLong("checkSum");
+                    if (checkSum(text) != checkSum) {
+                        throw new Exception("Incorrect checksum for text " + text);
+                    }
+                    count++;
+                }
+            }
+            if (count != 500) {
+                throw new Exception("Expected 500 Message events. Got " + count);
+            }
+        }
+    }
+
+    private static void emit(int count, String text) {
+        long checkSum = checkSum(text);
+        for (int i = 0; i < count; i++) {
+            MessageEvent m = new MessageEvent();
+            m.message = text;
+            m.checkSum = checkSum;
+            m.commit();
+        }
+    }
+
+    private static long checkSum(String text) {
+        long checkSum = SEED;
+        for (int i = 0; i < text.length(); i++) {
+            checkSum += 17 * text.charAt(i);
+        }
+        return checkSum;
+    }
+}