changeset 56217:db92a157dd70

8212117: Class.forName may return a reference to a loaded but not linked Class Reviewed-by: dholmes, mchung
author bchristi
date Mon, 09 Sep 2019 11:04:04 -0700
parents 734f7711f87c
children f894baf8d871
files make/hotspot/symbols/symbols-unix src/hotspot/share/include/jvm.h src/hotspot/share/prims/jni.cpp src/hotspot/share/prims/jvm.cpp src/hotspot/share/prims/jvm_misc.hpp src/hotspot/share/runtime/globals.hpp src/java.base/share/classes/java/lang/Class.java src/java.base/share/classes/java/lang/invoke/MethodHandles.java src/java.base/share/classes/sun/launcher/LauncherHelper.java src/java.base/share/native/libjava/Class.c test/hotspot/jtreg/gc/logging/TestMetaSpaceLog.java test/hotspot/jtreg/serviceability/jvmti/ClassStatus/ClassStatus.java test/hotspot/jtreg/serviceability/jvmti/ClassStatus/libClassStatus.c
diffstat 13 files changed, 342 insertions(+), 16 deletions(-) [+]
line wrap: on
line diff
--- a/make/hotspot/symbols/symbols-unix	Mon Sep 09 18:23:39 2019 +0100
+++ b/make/hotspot/symbols/symbols-unix	Mon Sep 09 11:04:04 2019 -0700
@@ -1,5 +1,5 @@
 #
-# Copyright (c) 2016, 2018, Oracle and/or its affiliates. All rights reserved.
+# Copyright (c) 2016, 2019, 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
@@ -149,6 +149,7 @@
 JVM_IsThreadAlive
 JVM_IsVMGeneratedMethodIx
 JVM_LatestUserDefinedLoader
+JVM_LinkClass
 JVM_LoadLibrary
 JVM_MaxMemory
 JVM_MaxObjectInspectionAge
--- a/src/hotspot/share/include/jvm.h	Mon Sep 09 18:23:39 2019 +0100
+++ b/src/hotspot/share/include/jvm.h	Mon Sep 09 11:04:04 2019 -0700
@@ -345,6 +345,11 @@
 JNIEXPORT jclass JNICALL
 JVM_FindPrimitiveClass(JNIEnv *env, const char *utf);
 
+/*
+ * Link the 'arg' class
+ */
+JNIEXPORT void JNICALL
+JVM_LinkClass(JNIEnv *env, jclass classClass, jclass arg);
 
 /*
  * Find a class from a boot class loader. Returns NULL if class not found.
--- a/src/hotspot/share/prims/jni.cpp	Mon Sep 09 18:23:39 2019 +0100
+++ b/src/hotspot/share/prims/jni.cpp	Mon Sep 09 11:04:04 2019 -0700
@@ -417,7 +417,7 @@
   }
 
   TempNewSymbol sym = SymbolTable::new_symbol(name);
-  result = find_class_from_class_loader(env, sym, true, loader,
+  result = find_class_from_class_loader(env, sym, true, true, loader,
                                         protection_domain, true, thread);
 
   if (log_is_enabled(Debug, class, resolve) && result != NULL) {
@@ -3289,7 +3289,7 @@
   Handle protection_domain; // null protection domain
 
   TempNewSymbol sym = SymbolTable::new_symbol(name);
-  jclass result =  find_class_from_class_loader(env, sym, true, loader, protection_domain, true, CHECK_NULL);
+  jclass result =  find_class_from_class_loader(env, sym, true, true, loader, protection_domain, true, CHECK_NULL);
 
   if (log_is_enabled(Debug, class, resolve) && result != NULL) {
     trace_class_resolution(java_lang_Class::as_Klass(JNIHandles::resolve_non_null(result)));
--- a/src/hotspot/share/prims/jvm.cpp	Mon Sep 09 18:23:39 2019 +0100
+++ b/src/hotspot/share/prims/jvm.cpp	Mon Sep 09 11:04:04 2019 -0700
@@ -717,6 +717,17 @@
 // Misc. class handling ///////////////////////////////////////////////////////////
 
 
+JVM_ENTRY(void, JVM_LinkClass(JNIEnv* env, jclass classClass, jclass arg))
+  JVMWrapper("JVM_LinkClass");
+
+  oop r = JNIHandles::resolve(arg);
+  Klass* klass = java_lang_Class::as_Klass(r);
+
+  if (!ClassForNameDeferLinking && klass->is_instance_klass()) {
+    InstanceKlass::cast(klass)->link_class(CHECK);
+  }
+JVM_END
+
 JVM_ENTRY(jclass, JVM_GetCallerClass(JNIEnv* env))
   JVMWrapper("JVM_GetCallerClass");
 
@@ -827,9 +838,10 @@
 
   Handle h_loader(THREAD, loader_oop);
   Handle h_prot(THREAD, protection_domain);
-  jclass result = find_class_from_class_loader(env, h_name, init, h_loader,
+
+  jboolean link = !ClassForNameDeferLinking;
+  jclass result = find_class_from_class_loader(env, h_name, init, link, h_loader,
                                                h_prot, false, THREAD);
-
   if (log_is_enabled(Debug, class, resolve) && result != NULL) {
     trace_class_resolution(java_lang_Class::as_Klass(JNIHandles::resolve_non_null(result)));
   }
@@ -866,7 +878,7 @@
   }
   Handle h_loader(THREAD, class_loader);
   Handle h_prot  (THREAD, protection_domain);
-  jclass result = find_class_from_class_loader(env, h_name, init, h_loader,
+  jclass result = find_class_from_class_loader(env, h_name, init, false, h_loader,
                                                h_prot, true, thread);
 
   if (log_is_enabled(Debug, class, resolve) && result != NULL) {
@@ -3424,9 +3436,12 @@
 
 // Shared JNI/JVM entry points //////////////////////////////////////////////////////////////
 
-jclass find_class_from_class_loader(JNIEnv* env, Symbol* name, jboolean init,
+jclass find_class_from_class_loader(JNIEnv* env, Symbol* name, jboolean init, jboolean link,
                                     Handle loader, Handle protection_domain,
                                     jboolean throwError, TRAPS) {
+  // Initialization also implies linking - check for coherent args
+  assert((init && link) || !init, "incorrect use of init/link arguments");
+
   // Security Note:
   //   The Java level wrapper will perform the necessary security check allowing
   //   us to pass the NULL as the initiating class loader.  The VM is responsible for
@@ -3435,9 +3450,11 @@
   //   if there is no security manager in 3-arg Class.forName().
   Klass* klass = SystemDictionary::resolve_or_fail(name, loader, protection_domain, throwError != 0, CHECK_NULL);
 
-  // Check if we should initialize the class
+  // Check if we should initialize the class (which implies linking), or just link it
   if (init && klass->is_instance_klass()) {
     klass->initialize(CHECK_NULL);
+  } else if (link && klass->is_instance_klass()) {
+    InstanceKlass::cast(klass)->link_class(CHECK_NULL);
   }
   return (jclass) JNIHandles::make_local(env, klass->java_mirror());
 }
--- a/src/hotspot/share/prims/jvm_misc.hpp	Mon Sep 09 18:23:39 2019 +0100
+++ b/src/hotspot/share/prims/jvm_misc.hpp	Mon Sep 09 11:04:04 2019 -0700
@@ -31,7 +31,8 @@
 // Useful entry points shared by JNI and JVM interface.
 // We do not allow real JNI or JVM entry point to call each other.
 
-jclass find_class_from_class_loader(JNIEnv* env, Symbol* name, jboolean init, Handle loader, Handle protection_domain, jboolean throwError, TRAPS);
+jclass find_class_from_class_loader(JNIEnv* env, Symbol* name, jboolean init, jboolean link,
+                                    Handle loader, Handle protection_domain, jboolean throwError, TRAPS);
 
 void trace_class_resolution(Klass* to_class);
 
--- a/src/hotspot/share/runtime/globals.hpp	Mon Sep 09 18:23:39 2019 +0100
+++ b/src/hotspot/share/runtime/globals.hpp	Mon Sep 09 11:04:04 2019 -0700
@@ -2164,6 +2164,9 @@
           "Maximum total size of NIO direct-buffer allocations")            \
           range(0, max_jlong)                                               \
                                                                             \
+  product(bool, ClassForNameDeferLinking, false,                            \
+          "Revert to not linking in Class.forName()")                       \
+                                                                            \
   /* Flags used for temporary code during development  */                   \
                                                                             \
   diagnostic(bool, UseNewCode, false,                                       \
--- a/src/java.base/share/classes/java/lang/Class.java	Mon Sep 09 18:23:39 2019 +0100
+++ b/src/java.base/share/classes/java/lang/Class.java	Mon Sep 09 11:04:04 2019 -0700
@@ -392,6 +392,10 @@
      *
      * @see       java.lang.Class#forName(String)
      * @see       java.lang.ClassLoader
+     *
+     * @jls 12.2 Loading of Classes and Interfaces
+     * @jls 12.3 Linking of Classes and Interfaces
+     * @jls 12.4 Initialization of Classes and Interfaces
      * @since     1.2
      */
     @CallerSensitive
@@ -438,6 +442,10 @@
      * <p> This method does not check whether the requested class is
      * accessible to its caller. </p>
      *
+     * <p> Note that this method throws errors related to loading and linking as
+     * specified in Sections 12.2 and 12.3 of <em>The Java Language
+     * Specification</em>.
+     *
      * @apiNote
      * This method returns {@code null} on failure rather than
      * throwing a {@link ClassNotFoundException}, as is done by
@@ -465,6 +473,8 @@
      *         in a module.</li>
      *         </ul>
      *
+     * @jls 12.2 Loading of Classes and Interfaces
+     * @jls 12.3 Linking of Classes and Interfaces
      * @since 9
      * @spec JPMS
      */
@@ -488,13 +498,21 @@
             cl = module.getClassLoader();
         }
 
+        Class<?> ret;
         if (cl != null) {
-            return cl.loadClass(module, name);
+            ret = cl.loadClass(module, name);
         } else {
-            return BootLoader.loadClass(module, name);
+            ret = BootLoader.loadClass(module, name);
         }
+        if (ret != null) {
+            // The loaded class should also be linked
+            linkClass(ret);
+        }
+        return ret;
     }
 
+    private static native void linkClass(Class<?> c);
+
     /**
      * Creates a new instance of the class represented by this {@code Class}
      * object.  The class is instantiated as if by a {@code new}
--- a/src/java.base/share/classes/java/lang/invoke/MethodHandles.java	Mon Sep 09 18:23:39 2019 +0100
+++ b/src/java.base/share/classes/java/lang/invoke/MethodHandles.java	Mon Sep 09 11:04:04 2019 -0700
@@ -1927,12 +1927,17 @@
         }
 
         /**
-         * Looks up a class by name from the lookup context defined by this {@code Lookup} object. The static
+         * Looks up a class by name from the lookup context defined by this {@code Lookup} object.
+         * This method attempts to locate, load, and link the class, and then determines whether
+         * the class is accessible to this {@code Lookup} object.  The static
          * initializer of the class is not run.
          * <p>
          * The lookup context here is determined by the {@linkplain #lookupClass() lookup class}, its class
-         * loader, and the {@linkplain #lookupModes() lookup modes}. In particular, the method first attempts to
-         * load the requested class, and then determines whether the class is accessible to this lookup object.
+         * loader, and the {@linkplain #lookupModes() lookup modes}.
+         * <p>
+         * Note that this method throws errors related to loading and linking as
+         * specified in Sections 12.2 and 12.3 of <em>The Java Language
+         * Specification</em>.
          *
          * @param targetName the fully qualified name of the class to be looked up.
          * @return the requested class.
@@ -1944,6 +1949,9 @@
          * modes.
          * @exception SecurityException if a security manager is present and it
          *                              <a href="MethodHandles.Lookup.html#secmgr">refuses access</a>
+         *
+         * @jls 12.2 Loading of Classes and Interfaces
+         * @jls 12.3 Linking of Classes and Interfaces
          * @since 9
          */
         public Class<?> findClass(String targetName) throws ClassNotFoundException, IllegalAccessException {
--- a/src/java.base/share/classes/sun/launcher/LauncherHelper.java	Mon Sep 09 18:23:39 2019 +0100
+++ b/src/java.base/share/classes/sun/launcher/LauncherHelper.java	Mon Sep 09 11:04:04 2019 -0700
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2007, 2018, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2007, 2019, 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
@@ -62,6 +62,7 @@
 import java.nio.file.DirectoryStream;
 import java.nio.file.Files;
 import java.nio.file.Path;
+import java.security.AccessControlException;
 import java.text.Normalizer;
 import java.text.MessageFormat;
 import java.util.ArrayList;
@@ -724,6 +725,9 @@
         } catch (LinkageError le) {
             abort(null, "java.launcher.module.error3", mainClass, m.getName(),
                     le.getClass().getName() + ": " + le.getLocalizedMessage());
+        } catch (AccessControlException ace) {
+            abort(ace, "java.launcher.module.error5", mainClass, m.getName(),
+                    ace.getClass().getName(), ace.getLocalizedMessage());
         }
         if (c == null) {
             abort(null, "java.launcher.module.error2", mainClass, mainModule);
@@ -780,6 +784,9 @@
         } catch (LinkageError le) {
             abort(le, "java.launcher.cls.error6", cn,
                     le.getClass().getName() + ": " + le.getLocalizedMessage());
+        } catch (AccessControlException ace) {
+            abort(ace, "java.launcher.cls.error7", cn,
+                    ace.getClass().getName(), ace.getLocalizedMessage());
         }
         return mainClass;
     }
--- a/src/java.base/share/native/libjava/Class.c	Mon Sep 09 18:23:39 2019 +0100
+++ b/src/java.base/share/native/libjava/Class.c	Mon Sep 09 11:04:04 2019 -0700
@@ -76,6 +76,7 @@
     {"getRawTypeAnnotations", "()" BA,      (void *)&JVM_GetClassTypeAnnotations},
     {"getNestHost0",         "()" CLS,      (void *)&JVM_GetNestHost},
     {"getNestMembers0",      "()[" CLS,     (void *)&JVM_GetNestMembers},
+    {"linkClass",            "(" CLS ")V",  (void *)&JVM_LinkClass},
 };
 
 #undef OBJ
--- a/test/hotspot/jtreg/gc/logging/TestMetaSpaceLog.java	Mon Sep 09 18:23:39 2019 +0100
+++ b/test/hotspot/jtreg/gc/logging/TestMetaSpaceLog.java	Mon Sep 09 11:04:04 2019 -0700
@@ -130,7 +130,7 @@
     public static void loadClass(WhiteBox wb) {
       try {
         URLClassLoader ucl = new URLClassLoader(urls);
-        Class.forName("case00", false, ucl);
+        ucl.loadClass("case00");
       } catch (Exception e) {
         e.printStackTrace();
       }
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/hotspot/jtreg/serviceability/jvmti/ClassStatus/ClassStatus.java	Mon Sep 09 11:04:04 2019 -0700
@@ -0,0 +1,92 @@
+/*
+ * Copyright (c) 2019, 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.
+ */
+
+/**
+ * @test
+ * @bug 8212117
+ * @summary Verify JVMTI GetClassStatus returns CLASS_PREPARE after call to Class.forName()
+ * @run main/othervm/native -agentlib:ClassStatus ClassStatus
+ */
+
+
+public class ClassStatus {
+    static {
+        try {
+            System.out.println("ClassStatus static block");
+            System.loadLibrary("ClassStatus");
+        } catch (UnsatisfiedLinkError ule) {
+            System.err.println("Could not load ClassStatus library");
+            System.err.println("java.library.path: "
+                + System.getProperty("java.library.path"));
+            throw ule;
+        }
+    }
+
+    static native int check(Class klass);
+
+    public static void main(String[] args) throws ClassNotFoundException {
+        ClassLoader loader = ClassStatus.class.getClassLoader();
+        Module module = loader.getUnnamedModule();
+
+        // Load class, but don't initialize it
+        Class foo2 = Class.forName(module, "Foo2");
+        Class foo3 = Class.forName("Foo3", false, loader);
+
+        System.out.println("Loaded: " + foo2);
+        System.out.println("Loaded: " + foo3);
+
+        int status2 = check(foo2);
+        int status3 = check(foo3);
+
+        new Foo2().bar();
+        new Foo3().bar();
+
+        if (status2 != 0) {
+            System.out.println("The agent returned non-zero exit status for Foo2: " + status2);
+        }
+        if (status3 != 0) {
+            System.out.println("The agent returned non-zero exit status for Foo3: " + status3);
+        }
+        if (status2 != 0 || status3 != 0) {
+            throw new RuntimeException("Non-zero status returned from the agent");
+        }
+    }
+}
+
+class Foo2 {
+    static {
+        System.out.println("Foo2 is initialized");
+    }
+    void bar() {
+        System.out.println("Foo2.bar() is called");
+    }
+}
+
+class Foo3 {
+    static {
+        System.out.println("Foo3 is initialized");
+    }
+    void bar() {
+        System.out.println("Foo3.bar() is called");
+    }
+}
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/hotspot/jtreg/serviceability/jvmti/ClassStatus/libClassStatus.c	Mon Sep 09 11:04:04 2019 -0700
@@ -0,0 +1,173 @@
+/*
+ * Copyright (c) 2019, 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.
+ */
+
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include "jvmti.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#ifndef JNI_ENV_ARG
+
+#ifdef __cplusplus
+#define JNI_ENV_ARG(x, y) y
+#define JNI_ENV_PTR(x) x
+#else
+#define JNI_ENV_ARG(x,y) x, y
+#define JNI_ENV_PTR(x) (*x)
+#endif
+
+#endif
+
+#define PASSED 0
+#define FAILED 2
+
+static jvmtiEnv* jvmti = NULL;
+
+static jint Agent_Initialize(JavaVM *jvm, char *options, void *reserved);
+
+JNIEXPORT jint JNICALL
+Agent_OnLoad(JavaVM *jvm, char *options, void *reserved) {
+    return Agent_Initialize(jvm, options, reserved);
+}
+
+JNIEXPORT jint JNICALL
+Agent_OnAttach(JavaVM *jvm, char *options, void *reserved) {
+    return Agent_Initialize(jvm, options, reserved);
+}
+
+JNIEXPORT jint JNICALL
+JNI_OnLoad(JavaVM *jvm, void *reserved) {
+    return JNI_VERSION_9;
+}
+
+static void
+check_jvmti_error(jvmtiEnv *jvmti, char* fname, jvmtiError err) {
+    if (err != JVMTI_ERROR_NONE) {
+        printf("  ## %s error: %d\n", fname, err);
+        fflush(0);
+        exit(err);
+    }
+}
+
+static char*
+get_class_signature(jvmtiEnv *jvmti, jclass klass) {
+    char* sign = NULL;
+    jvmtiError err = (*jvmti)->GetClassSignature(jvmti, klass, &sign, NULL);
+
+    check_jvmti_error(jvmti, "GetClassSignature", err);
+    return sign;
+}
+
+static jboolean
+is_class_status_prepared(jvmtiEnv *jvmti, jclass klass) {
+    char* sign = get_class_signature(jvmti, klass);
+    jint status = 0;
+    jvmtiError err = (*jvmti)->GetClassStatus(jvmti, klass, &status);
+
+    check_jvmti_error(jvmti, "GetClassStatus", err);
+    printf("    Class %s status: 0x%08x\n", sign, status);
+    printf("    Class %s is prepared: %d\n", sign, (status & JVMTI_CLASS_STATUS_PREPARED) != 0);
+    fflush(0);
+
+    return (status & JVMTI_CLASS_STATUS_PREPARED) != 0;
+}
+
+static jboolean
+is_class_in_loaded_classes(JNIEnv *env, jclass klass) {
+    char* sign = get_class_signature(jvmti, klass);
+    jint class_count = 0;
+    jclass* classes = NULL;
+    jvmtiError err = (*jvmti)->GetLoadedClasses(jvmti, &class_count, &classes);
+
+    check_jvmti_error(jvmti, "GetLoadedClasses", err);
+
+    for (int i = 0; i < class_count; i++) {
+        jclass cls = classes[i];
+        jboolean same = (*env)->IsSameObject(env, cls, klass);
+        if (same) {
+            printf("Found class %s in the list of loaded classes\n", sign);
+            fflush(0);
+            return JNI_TRUE;
+        }
+    }
+    printf("Error: Have not found class %s in the list of loaded classes\n", sign);
+    fflush(0);
+    return JNI_FALSE;
+}
+
+static void JNICALL
+ClassPrepare(jvmtiEnv *jvmti, JNIEnv *env, jthread thread, jclass klass) {
+    char* sign = get_class_signature(jvmti, klass);
+
+    sign = (sign == NULL) ? "NULL" : sign;
+
+    if (strcmp(sign, "LFoo2;") == 0 || strcmp(sign, "LFoo3;") == 0) {
+        printf("ClassPrepare event for class: %s\n", sign);
+        fflush(0);
+    }
+}
+
+static jint
+Agent_Initialize(JavaVM *jvm, char *options, void *reserved) {
+    jvmtiError err;
+    jint size;
+    jint res;
+    jvmtiEventCallbacks callbacks;
+
+    printf("Agent_Initialize started\n");
+    fflush(0);
+    res = JNI_ENV_PTR(jvm)->GetEnv(JNI_ENV_ARG(jvm, (void **) &jvmti), JVMTI_VERSION_9);
+    if (res != JNI_OK || jvmti == NULL) {
+        printf("## Agent_Initialize: Error in GetEnv: res: %d, jvmti env: %p\n", res, jvmti);
+        return JNI_ERR;
+    }
+
+    size = (jint)sizeof(callbacks);
+    memset(&callbacks, 0, size);
+    callbacks.ClassPrepare = ClassPrepare;
+
+    err = (*jvmti)->SetEventCallbacks(jvmti, &callbacks, size);
+    check_jvmti_error(jvmti, "## Agent_Initialize: SetEventCallbacks", err);
+
+    err = (*jvmti)->SetEventNotificationMode(jvmti, JVMTI_ENABLE, JVMTI_EVENT_CLASS_PREPARE, NULL);
+    check_jvmti_error(jvmti, "## Agent_Initialize: SetEventNotificationMode CLASS_PREPARE", err);
+    return JNI_OK;
+}
+
+JNIEXPORT jint JNICALL
+Java_ClassStatus_check(JNIEnv *env, jclass cls, jclass klass) {
+    if (is_class_in_loaded_classes(env, klass) != JNI_TRUE ||
+        is_class_status_prepared(jvmti, klass)  != JNI_TRUE) {
+        return FAILED;
+    }
+    return PASSED;
+}
+
+#ifdef __cplusplus
+}
+#endif