test/ti-agent/common_helper.cc - platform/art - Gitiles

 /*
  * Copyright (C) 2016 The Android Open Source Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *      http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 #include "ti-agent/common_helper.h"

 #include <dlfcn.h>
 #include <stdio.h>
 #include <sstream>
 #include <deque>

 #include "android-base/stringprintf.h"
 #include "art_method.h"
 #include "jni.h"
 #include "jni_internal.h"
 #include "openjdkjvmti/jvmti.h"
 #include "scoped_thread_state_change-inl.h"
 #include "ScopedLocalRef.h"
 #include "stack.h"
 #include "ti-agent/common_load.h"
 #include "utils.h"

 namespace art {
 bool RuntimeIsJVM;

 bool IsJVM() {
   return RuntimeIsJVM;
 }

 void SetAllCapabilities(jvmtiEnv* env) {
   jvmtiCapabilities caps;
   env->GetPotentialCapabilities(&caps);
   env->AddCapabilities(&caps);
 }

 bool JvmtiErrorToException(JNIEnv* env, jvmtiError error) {
   if (error == JVMTI_ERROR_NONE) {
     return false;
   }

   ScopedLocalRef<jclass> rt_exception(env, env->FindClass("java/lang/RuntimeException"));
   if (rt_exception.get() == nullptr) {
     // CNFE should be pending.
     return true;
   }

   char* err;
   jvmti_env->GetErrorName(error, &err);

   env->ThrowNew(rt_exception.get(), err);

   jvmti_env->Deallocate(reinterpret_cast<unsigned char*>(err));
   return true;
 }


 template <bool is_redefine>
 static void throwCommonRedefinitionError(jvmtiEnv* jvmti,
                                          JNIEnv* env,
                                          jint num_targets,
                                          jclass* target,
                                          jvmtiError res) {
   std::stringstream err;
   char* error = nullptr;
   jvmti->GetErrorName(res, &error);
   err << "Failed to " << (is_redefine ? "redefine" : "retransform") << " class";
   if (num_targets > 1) {
     err << "es";
   }
   err << " <";
   for (jint i = 0; i < num_targets; i++) {
     char* signature = nullptr;
     char* generic = nullptr;
     jvmti->GetClassSignature(target[i], &signature, &generic);
     if (i != 0) {
       err << ", ";
     }
     err << signature;
     jvmti->Deallocate(reinterpret_cast<unsigned char*>(signature));
     jvmti->Deallocate(reinterpret_cast<unsigned char*>(generic));
   }
   err << "> due to " << error;
   std::string message = err.str();
   jvmti->Deallocate(reinterpret_cast<unsigned char*>(error));
   env->ThrowNew(env->FindClass("java/lang/Exception"), message.c_str());
 }

 namespace common_redefine {

 static void throwRedefinitionError(jvmtiEnv* jvmti,
                                    JNIEnv* env,
                                    jint num_targets,
                                    jclass* target,
                                    jvmtiError res) {
   return throwCommonRedefinitionError<true>(jvmti, env, num_targets, target, res);
 }

 static void DoMultiClassRedefine(jvmtiEnv* jvmti_env,
                                  JNIEnv* env,
                                  jint num_redefines,
                                  jclass* targets,
                                  jbyteArray* class_file_bytes,
                                  jbyteArray* dex_file_bytes) {
   std::vector<jvmtiClassDefinition> defs;
   for (jint i = 0; i < num_redefines; i++) {
     jbyteArray desired_array = IsJVM() ? class_file_bytes[i] : dex_file_bytes[i];
     jint len = static_cast<jint>(env->GetArrayLength(desired_array));
     const unsigned char* redef_bytes = reinterpret_cast<const unsigned char*>(
         env->GetByteArrayElements(desired_array, nullptr));
     defs.push_back({targets[i], static_cast<jint>(len), redef_bytes});
   }
   jvmtiError res = jvmti_env->RedefineClasses(num_redefines, defs.data());
   if (res != JVMTI_ERROR_NONE) {
     throwRedefinitionError(jvmti_env, env, num_redefines, targets, res);
   }
 }

 static void DoClassRedefine(jvmtiEnv* jvmti_env,
                             JNIEnv* env,
                             jclass target,
                             jbyteArray class_file_bytes,
                             jbyteArray dex_file_bytes) {
   return DoMultiClassRedefine(jvmti_env, env, 1, &target, &class_file_bytes, &dex_file_bytes);
 }

 // Magic JNI export that classes can use for redefining classes.
 // To use classes should declare this as a native function with signature (Ljava/lang/Class;[B[B)V
 extern "C" JNIEXPORT void JNICALL Java_Main_doCommonClassRedefinition(JNIEnv* env,
                                                                       jclass,
                                                                       jclass target,
                                                                       jbyteArray class_file_bytes,
                                                                       jbyteArray dex_file_bytes) {
   DoClassRedefine(jvmti_env, env, target, class_file_bytes, dex_file_bytes);
 }

 // Magic JNI export that classes can use for redefining classes.
 // To use classes should declare this as a native function with signature
 // ([Ljava/lang/Class;[[B[[B)V
 extern "C" JNIEXPORT void JNICALL Java_Main_doCommonMultiClassRedefinition(
     JNIEnv* env,
     jclass,
     jobjectArray targets,
     jobjectArray class_file_bytes,
     jobjectArray dex_file_bytes) {
   std::vector<jclass> classes;
   std::vector<jbyteArray> class_files;
   std::vector<jbyteArray> dex_files;
   jint len = env->GetArrayLength(targets);
   if (len != env->GetArrayLength(class_file_bytes) || len != env->GetArrayLength(dex_file_bytes)) {
     env->ThrowNew(env->FindClass("java/lang/IllegalArgumentException"),
                   "the three array arguments passed to this function have different lengths!");
     return;
   }
   for (jint i = 0; i < len; i++) {
     classes.push_back(static_cast<jclass>(env->GetObjectArrayElement(targets, i)));
     dex_files.push_back(static_cast<jbyteArray>(env->GetObjectArrayElement(dex_file_bytes, i)));
     class_files.push_back(static_cast<jbyteArray>(env->GetObjectArrayElement(class_file_bytes, i)));
   }
   return DoMultiClassRedefine(jvmti_env,
                               env,
                               len,
                               classes.data(),
                               class_files.data(),
                               dex_files.data());
 }

 // Get all capabilities except those related to retransformation.
 jint OnLoad(JavaVM* vm,
             char* options ATTRIBUTE_UNUSED,
             void* reserved ATTRIBUTE_UNUSED) {
   if (vm->GetEnv(reinterpret_cast<void**>(&jvmti_env), JVMTI_VERSION_1_0)) {
     printf("Unable to get jvmti env!\n");
     return 1;
   }
   jvmtiCapabilities caps;
   jvmti_env->GetPotentialCapabilities(&caps);
   caps.can_retransform_classes = 0;
   caps.can_retransform_any_class = 0;
   jvmti_env->AddCapabilities(&caps);
   return 0;
 }

 }  // namespace common_redefine

 namespace common_retransform {

 struct CommonTransformationResult {
   std::vector<unsigned char> class_bytes;
   std::vector<unsigned char> dex_bytes;

   CommonTransformationResult(size_t class_size, size_t dex_size)
       : class_bytes(class_size), dex_bytes(dex_size) {}

   CommonTransformationResult() = default;
   CommonTransformationResult(CommonTransformationResult&&) = default;
   CommonTransformationResult(CommonTransformationResult&) = default;
 };

 // Map from class name to transformation result.
 std::map<std::string, std::deque<CommonTransformationResult>> gTransformations;

 extern "C" JNIEXPORT void JNICALL Java_Main_addCommonTransformationResult(JNIEnv* env,
                                                                           jclass,
                                                                           jstring class_name,
                                                                           jbyteArray class_array,
                                                                           jbyteArray dex_array) {
   const char* name_chrs = env->GetStringUTFChars(class_name, nullptr);
   std::string name_str(name_chrs);
   env->ReleaseStringUTFChars(class_name, name_chrs);
   CommonTransformationResult trans(env->GetArrayLength(class_array),
                                    env->GetArrayLength(dex_array));
   if (env->ExceptionOccurred()) {
     return;
   }
   env->GetByteArrayRegion(class_array,
                           0,
                           env->GetArrayLength(class_array),
                           reinterpret_cast<jbyte*>(trans.class_bytes.data()));
   if (env->ExceptionOccurred()) {
     return;
   }
   env->GetByteArrayRegion(dex_array,
                           0,
                           env->GetArrayLength(dex_array),
                           reinterpret_cast<jbyte*>(trans.dex_bytes.data()));
   if (env->ExceptionOccurred()) {
     return;
   }
   if (gTransformations.find(name_str) == gTransformations.end()) {
     std::deque<CommonTransformationResult> list;
     gTransformations[name_str] = std::move(list);
   }
   gTransformations[name_str].push_back(std::move(trans));
 }

 // The hook we are using.
 void JNICALL CommonClassFileLoadHookRetransformable(jvmtiEnv* jvmti_env,
                                                     JNIEnv* jni_env ATTRIBUTE_UNUSED,
                                                     jclass class_being_redefined ATTRIBUTE_UNUSED,
                                                     jobject loader ATTRIBUTE_UNUSED,
                                                     const char* name,
                                                     jobject protection_domain ATTRIBUTE_UNUSED,
                                                     jint class_data_len ATTRIBUTE_UNUSED,
                                                     const unsigned char* class_dat ATTRIBUTE_UNUSED,
                                                     jint* new_class_data_len,
                                                     unsigned char** new_class_data) {
   std::string name_str(name);
   if (gTransformations.find(name_str) != gTransformations.end() &&
       gTransformations[name_str].size() > 0) {
     CommonTransformationResult& res = gTransformations[name_str][0];
     const std::vector<unsigned char>& desired_array = IsJVM() ? res.class_bytes : res.dex_bytes;
     unsigned char* new_data;
     CHECK_EQ(JVMTI_ERROR_NONE, jvmti_env->Allocate(desired_array.size(), &new_data));
     memcpy(new_data, desired_array.data(), desired_array.size());
     *new_class_data = new_data;
     *new_class_data_len = desired_array.size();
     gTransformations[name_str].pop_front();
   }
 }

 extern "C" JNIEXPORT void Java_Main_enableCommonRetransformation(JNIEnv* env,
                                                                  jclass,
                                                                  jboolean enable) {
   jvmtiError res = jvmti_env->SetEventNotificationMode(enable ? JVMTI_ENABLE : JVMTI_DISABLE,
                                                        JVMTI_EVENT_CLASS_FILE_LOAD_HOOK,
                                                        nullptr);
   if (res != JVMTI_ERROR_NONE) {
     JvmtiErrorToException(env, res);
   }
 }

 static void throwRetransformationError(jvmtiEnv* jvmti,
                                        JNIEnv* env,
                                        jint num_targets,
                                        jclass* targets,
                                        jvmtiError res) {
   return throwCommonRedefinitionError<false>(jvmti, env, num_targets, targets, res);
 }

 static void DoClassRetransformation(jvmtiEnv* jvmti_env, JNIEnv* env, jobjectArray targets) {
   std::vector<jclass> classes;
   jint len = env->GetArrayLength(targets);
   for (jint i = 0; i < len; i++) {
     classes.push_back(static_cast<jclass>(env->GetObjectArrayElement(targets, i)));
   }
   jvmtiError res = jvmti_env->RetransformClasses(len, classes.data());
   if (res != JVMTI_ERROR_NONE) {
     throwRetransformationError(jvmti_env, env, len, classes.data(), res);
   }
 }

 // TODO Write something useful.
 extern "C" JNIEXPORT void JNICALL Java_Main_doCommonClassRetransformation(JNIEnv* env,
                                                                           jclass,
                                                                           jobjectArray targets) {
   DoClassRetransformation(jvmti_env, env, targets);
 }

 // Get all capabilities except those related to retransformation.
 jint OnLoad(JavaVM* vm,
             char* options ATTRIBUTE_UNUSED,
             void* reserved ATTRIBUTE_UNUSED) {
   if (vm->GetEnv(reinterpret_cast<void**>(&jvmti_env), JVMTI_VERSION_1_0)) {
     printf("Unable to get jvmti env!\n");
     return 1;
   }
   SetAllCapabilities(jvmti_env);
   jvmtiEventCallbacks cb;
   memset(&cb, 0, sizeof(cb));
   cb.ClassFileLoadHook = CommonClassFileLoadHookRetransformable;
   if (jvmti_env->SetEventCallbacks(&cb, sizeof(cb)) != JVMTI_ERROR_NONE) {
     printf("Unable to set class file load hook cb!\n");
     return 1;
   }
   return 0;
 }

 }  // namespace common_retransform

 static void BindMethod(jvmtiEnv* jenv,
                        JNIEnv* env,
                        jclass klass,
                        jmethodID method) {
   char* name;
   char* signature;
   jvmtiError name_result = jenv->GetMethodName(method, &name, &signature, nullptr);
   if (name_result != JVMTI_ERROR_NONE) {
     LOG(FATAL) << "Could not get methods";
   }

   ArtMethod* m = jni::DecodeArtMethod(method);

   std::string names[2];
   {
     ScopedObjectAccess soa(Thread::Current());
     names[0] = m->JniShortName();
     names[1] = m->JniLongName();
   }
   for (const std::string& mangled_name : names) {
     void* sym = dlsym(RTLD_DEFAULT, mangled_name.c_str());
     if (sym == nullptr) {
       continue;
     }

     JNINativeMethod native_method;
     native_method.fnPtr = sym;
     native_method.name = name;
     native_method.signature = signature;

     env->RegisterNatives(klass, &native_method, 1);

     jenv->Deallocate(reinterpret_cast<unsigned char*>(name));
     jenv->Deallocate(reinterpret_cast<unsigned char*>(signature));
     return;
   }

   LOG(FATAL) << "Could not find " << names[0];
 }

 static jclass FindClassWithSystemClassLoader(JNIEnv* env, const char* class_name) {
   // Find the system classloader.
   ScopedLocalRef<jclass> cl_klass(env, env->FindClass("java/lang/ClassLoader"));
   if (cl_klass.get() == nullptr) {
     return nullptr;
   }
   jmethodID getsystemclassloader_method = env->GetStaticMethodID(cl_klass.get(),
                                                                  "getSystemClassLoader",
                                                                  "()Ljava/lang/ClassLoader;");
   if (getsystemclassloader_method == nullptr) {
     return nullptr;
   }
   ScopedLocalRef<jobject> cl(env, env->CallStaticObjectMethod(cl_klass.get(),
                                                               getsystemclassloader_method));
   if (cl.get() == nullptr) {
     return nullptr;
   }

   // Create a String of the name.
   std::string descriptor = android::base::StringPrintf("L%s;", class_name);
   std::string dot_name = DescriptorToDot(descriptor.c_str());
   ScopedLocalRef<jstring> name_str(env, env->NewStringUTF(dot_name.c_str()));

   // Call Class.forName with it.
   ScopedLocalRef<jclass> c_klass(env, env->FindClass("java/lang/Class"));
   if (c_klass.get() == nullptr) {
     return nullptr;
   }
   jmethodID forname_method = env->GetStaticMethodID(
       c_klass.get(),
       "forName",
       "(Ljava/lang/String;ZLjava/lang/ClassLoader;)Ljava/lang/Class;");
   if (forname_method == nullptr) {
     return nullptr;
   }

   return reinterpret_cast<jclass>(env->CallStaticObjectMethod(c_klass.get(),
                                                               forname_method,
                                                               name_str.get(),
                                                               JNI_FALSE,
                                                               cl.get()));
 }

 void BindFunctions(jvmtiEnv* jenv, JNIEnv* env, const char* class_name) {
   // Use JNI to load the class.
   ScopedLocalRef<jclass> klass(env, env->FindClass(class_name));
   if (klass.get() == nullptr) {
     // We may be called with the wrong classloader. Try explicitly using the system classloader.
     env->ExceptionClear();
     klass.reset(FindClassWithSystemClassLoader(env, class_name));
     if (klass.get() == nullptr) {
       LOG(FATAL) << "Could not load " << class_name;
     }
   }

   // Use JVMTI to get the methods.
   jint method_count;
   jmethodID* methods;
   jvmtiError methods_result = jenv->GetClassMethods(klass.get(), &method_count, &methods);
   if (methods_result != JVMTI_ERROR_NONE) {
     LOG(FATAL) << "Could not get methods";
   }

   // Check each method.
   for (jint i = 0; i < method_count; ++i) {
     jint modifiers;
     jvmtiError mod_result = jenv->GetMethodModifiers(methods[i], &modifiers);
     if (mod_result != JVMTI_ERROR_NONE) {
       LOG(FATAL) << "Could not get methods";
     }
     constexpr jint kNative = static_cast<jint>(kAccNative);
     if ((modifiers & kNative) != 0) {
       BindMethod(jenv, env, klass.get(), methods[i]);
     }
   }

   jenv->Deallocate(reinterpret_cast<unsigned char*>(methods));
 }

 }  // namespace art
	/*
	* Copyright (C) 2016 The Android Open Source Project
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	#include "ti-agent/common_helper.h"

	#include <dlfcn.h>
	#include <stdio.h>
	#include <sstream>
	#include <deque>

	#include "android-base/stringprintf.h"
	#include "art_method.h"
	#include "jni.h"
	#include "jni_internal.h"
	#include "openjdkjvmti/jvmti.h"
	#include "scoped_thread_state_change-inl.h"
	#include "ScopedLocalRef.h"
	#include "stack.h"
	#include "ti-agent/common_load.h"
	#include "utils.h"

	namespace art {
	bool RuntimeIsJVM;

	bool IsJVM() {
	return RuntimeIsJVM;
	}

	void SetAllCapabilities(jvmtiEnv* env) {
	jvmtiCapabilities caps;
	env->GetPotentialCapabilities(&caps);
	env->AddCapabilities(&caps);
	}

	bool JvmtiErrorToException(JNIEnv* env, jvmtiError error) {
	if (error == JVMTI_ERROR_NONE) {
	return false;
	}

	ScopedLocalRef<jclass> rt_exception(env, env->FindClass("java/lang/RuntimeException"));
	if (rt_exception.get() == nullptr) {
	// CNFE should be pending.
	return true;
	}

	char* err;
	jvmti_env->GetErrorName(error, &err);

	env->ThrowNew(rt_exception.get(), err);

	jvmti_env->Deallocate(reinterpret_cast<unsigned char*>(err));
	return true;
	}


	template <bool is_redefine>
	static void throwCommonRedefinitionError(jvmtiEnv* jvmti,
	JNIEnv* env,
	jint num_targets,
	jclass* target,
	jvmtiError res) {
	std::stringstream err;
	char* error = nullptr;
	jvmti->GetErrorName(res, &error);
	err << "Failed to " << (is_redefine ? "redefine" : "retransform") << " class";
	if (num_targets > 1) {
	err << "es";
	}
	err << " <";
	for (jint i = 0; i < num_targets; i++) {
	char* signature = nullptr;
	char* generic = nullptr;
	jvmti->GetClassSignature(target[i], &signature, &generic);
	if (i != 0) {
	err << ", ";
	}
	err << signature;
	jvmti->Deallocate(reinterpret_cast<unsigned char*>(signature));
	jvmti->Deallocate(reinterpret_cast<unsigned char*>(generic));
	}
	err << "> due to " << error;
	std::string message = err.str();
	jvmti->Deallocate(reinterpret_cast<unsigned char*>(error));
	env->ThrowNew(env->FindClass("java/lang/Exception"), message.c_str());
	}

	namespace common_redefine {

	static void throwRedefinitionError(jvmtiEnv* jvmti,
	JNIEnv* env,
	jint num_targets,
	jclass* target,
	jvmtiError res) {
	return throwCommonRedefinitionError<true>(jvmti, env, num_targets, target, res);
	}

	static void DoMultiClassRedefine(jvmtiEnv* jvmti_env,
	JNIEnv* env,
	jint num_redefines,
	jclass* targets,
	jbyteArray* class_file_bytes,
	jbyteArray* dex_file_bytes) {
	std::vector<jvmtiClassDefinition> defs;
	for (jint i = 0; i < num_redefines; i++) {
	jbyteArray desired_array = IsJVM() ? class_file_bytes[i] : dex_file_bytes[i];
	jint len = static_cast<jint>(env->GetArrayLength(desired_array));
	const unsigned char* redef_bytes = reinterpret_cast<const unsigned char*>(
	env->GetByteArrayElements(desired_array, nullptr));
	defs.push_back({targets[i], static_cast<jint>(len), redef_bytes});
	}
	jvmtiError res = jvmti_env->RedefineClasses(num_redefines, defs.data());
	if (res != JVMTI_ERROR_NONE) {
	throwRedefinitionError(jvmti_env, env, num_redefines, targets, res);
	}
	}

	static void DoClassRedefine(jvmtiEnv* jvmti_env,
	JNIEnv* env,
	jclass target,
	jbyteArray class_file_bytes,
	jbyteArray dex_file_bytes) {
	return DoMultiClassRedefine(jvmti_env, env, 1, &target, &class_file_bytes, &dex_file_bytes);
	}

	// Magic JNI export that classes can use for redefining classes.
	// To use classes should declare this as a native function with signature (Ljava/lang/Class;[B[B)V
	extern "C" JNIEXPORT void JNICALL Java_Main_doCommonClassRedefinition(JNIEnv* env,
	jclass,
	jclass target,
	jbyteArray class_file_bytes,
	jbyteArray dex_file_bytes) {
	DoClassRedefine(jvmti_env, env, target, class_file_bytes, dex_file_bytes);
	}

	// Magic JNI export that classes can use for redefining classes.
	// To use classes should declare this as a native function with signature
	// ([Ljava/lang/Class;[[B[[B)V
	extern "C" JNIEXPORT void JNICALL Java_Main_doCommonMultiClassRedefinition(
	JNIEnv* env,
	jclass,
	jobjectArray targets,
	jobjectArray class_file_bytes,
	jobjectArray dex_file_bytes) {
	std::vector<jclass> classes;
	std::vector<jbyteArray> class_files;
	std::vector<jbyteArray> dex_files;
	jint len = env->GetArrayLength(targets);
	if (len != env->GetArrayLength(class_file_bytes) \|\| len != env->GetArrayLength(dex_file_bytes)) {
	env->ThrowNew(env->FindClass("java/lang/IllegalArgumentException"),
	"the three array arguments passed to this function have different lengths!");
	return;
	}
	for (jint i = 0; i < len; i++) {
	classes.push_back(static_cast<jclass>(env->GetObjectArrayElement(targets, i)));
	dex_files.push_back(static_cast<jbyteArray>(env->GetObjectArrayElement(dex_file_bytes, i)));
	class_files.push_back(static_cast<jbyteArray>(env->GetObjectArrayElement(class_file_bytes, i)));
	}
	return DoMultiClassRedefine(jvmti_env,
	env,
	len,
	classes.data(),
	class_files.data(),
	dex_files.data());
	}

	// Get all capabilities except those related to retransformation.
	jint OnLoad(JavaVM* vm,
	char* options ATTRIBUTE_UNUSED,
	void* reserved ATTRIBUTE_UNUSED) {
	if (vm->GetEnv(reinterpret_cast<void**>(&jvmti_env), JVMTI_VERSION_1_0)) {
	printf("Unable to get jvmti env!\n");
	return 1;
	}
	jvmtiCapabilities caps;
	jvmti_env->GetPotentialCapabilities(&caps);
	caps.can_retransform_classes = 0;
	caps.can_retransform_any_class = 0;
	jvmti_env->AddCapabilities(&caps);
	return 0;
	}

	} // namespace common_redefine

	namespace common_retransform {

	struct CommonTransformationResult {
	std::vector<unsigned char> class_bytes;
	std::vector<unsigned char> dex_bytes;

	CommonTransformationResult(size_t class_size, size_t dex_size)
	: class_bytes(class_size), dex_bytes(dex_size) {}

	CommonTransformationResult() = default;
	CommonTransformationResult(CommonTransformationResult&&) = default;
	CommonTransformationResult(CommonTransformationResult&) = default;
	};

	// Map from class name to transformation result.
	std::map<std::string, std::deque<CommonTransformationResult>> gTransformations;

	extern "C" JNIEXPORT void JNICALL Java_Main_addCommonTransformationResult(JNIEnv* env,
	jclass,
	jstring class_name,
	jbyteArray class_array,
	jbyteArray dex_array) {
	const char* name_chrs = env->GetStringUTFChars(class_name, nullptr);
	std::string name_str(name_chrs);
	env->ReleaseStringUTFChars(class_name, name_chrs);
	CommonTransformationResult trans(env->GetArrayLength(class_array),
	env->GetArrayLength(dex_array));
	if (env->ExceptionOccurred()) {
	return;
	}
	env->GetByteArrayRegion(class_array,
	0,
	env->GetArrayLength(class_array),
	reinterpret_cast<jbyte*>(trans.class_bytes.data()));
	if (env->ExceptionOccurred()) {
	return;
	}
	env->GetByteArrayRegion(dex_array,
	0,
	env->GetArrayLength(dex_array),
	reinterpret_cast<jbyte*>(trans.dex_bytes.data()));
	if (env->ExceptionOccurred()) {
	return;
	}
	if (gTransformations.find(name_str) == gTransformations.end()) {
	std::deque<CommonTransformationResult> list;
	gTransformations[name_str] = std::move(list);
	}
	gTransformations[name_str].push_back(std::move(trans));
	}

	// The hook we are using.
	void JNICALL CommonClassFileLoadHookRetransformable(jvmtiEnv* jvmti_env,
	JNIEnv* jni_env ATTRIBUTE_UNUSED,
	jclass class_being_redefined ATTRIBUTE_UNUSED,
	jobject loader ATTRIBUTE_UNUSED,
	const char* name,
	jobject protection_domain ATTRIBUTE_UNUSED,
	jint class_data_len ATTRIBUTE_UNUSED,
	const unsigned char* class_dat ATTRIBUTE_UNUSED,
	jint* new_class_data_len,
	unsigned char** new_class_data) {
	std::string name_str(name);
	if (gTransformations.find(name_str) != gTransformations.end() &&
	gTransformations[name_str].size() > 0) {
	CommonTransformationResult& res = gTransformations[name_str][0];
	const std::vector<unsigned char>& desired_array = IsJVM() ? res.class_bytes : res.dex_bytes;
	unsigned char* new_data;
	CHECK_EQ(JVMTI_ERROR_NONE, jvmti_env->Allocate(desired_array.size(), &new_data));
	memcpy(new_data, desired_array.data(), desired_array.size());
	*new_class_data = new_data;
	*new_class_data_len = desired_array.size();
	gTransformations[name_str].pop_front();
	}
	}

	extern "C" JNIEXPORT void Java_Main_enableCommonRetransformation(JNIEnv* env,
	jclass,
	jboolean enable) {
	jvmtiError res = jvmti_env->SetEventNotificationMode(enable ? JVMTI_ENABLE : JVMTI_DISABLE,
	JVMTI_EVENT_CLASS_FILE_LOAD_HOOK,
	nullptr);
	if (res != JVMTI_ERROR_NONE) {
	JvmtiErrorToException(env, res);
	}
	}

	static void throwRetransformationError(jvmtiEnv* jvmti,
	JNIEnv* env,
	jint num_targets,
	jclass* targets,
	jvmtiError res) {
	return throwCommonRedefinitionError<false>(jvmti, env, num_targets, targets, res);
	}

	static void DoClassRetransformation(jvmtiEnv* jvmti_env, JNIEnv* env, jobjectArray targets) {
	std::vector<jclass> classes;
	jint len = env->GetArrayLength(targets);
	for (jint i = 0; i < len; i++) {
	classes.push_back(static_cast<jclass>(env->GetObjectArrayElement(targets, i)));
	}
	jvmtiError res = jvmti_env->RetransformClasses(len, classes.data());
	if (res != JVMTI_ERROR_NONE) {
	throwRetransformationError(jvmti_env, env, len, classes.data(), res);
	}
	}

	// TODO Write something useful.
	extern "C" JNIEXPORT void JNICALL Java_Main_doCommonClassRetransformation(JNIEnv* env,
	jclass,
	jobjectArray targets) {
	DoClassRetransformation(jvmti_env, env, targets);
	}

	// Get all capabilities except those related to retransformation.
	jint OnLoad(JavaVM* vm,
	char* options ATTRIBUTE_UNUSED,
	void* reserved ATTRIBUTE_UNUSED) {
	if (vm->GetEnv(reinterpret_cast<void**>(&jvmti_env), JVMTI_VERSION_1_0)) {
	printf("Unable to get jvmti env!\n");
	return 1;
	}
	SetAllCapabilities(jvmti_env);
	jvmtiEventCallbacks cb;
	memset(&cb, 0, sizeof(cb));
	cb.ClassFileLoadHook = CommonClassFileLoadHookRetransformable;
	if (jvmti_env->SetEventCallbacks(&cb, sizeof(cb)) != JVMTI_ERROR_NONE) {
	printf("Unable to set class file load hook cb!\n");
	return 1;
	}
	return 0;
	}

	} // namespace common_retransform

	static void BindMethod(jvmtiEnv* jenv,
	JNIEnv* env,
	jclass klass,
	jmethodID method) {
	char* name;
	char* signature;
	jvmtiError name_result = jenv->GetMethodName(method, &name, &signature, nullptr);
	if (name_result != JVMTI_ERROR_NONE) {
	LOG(FATAL) << "Could not get methods";
	}

	ArtMethod* m = jni::DecodeArtMethod(method);

	std::string names[2];
	{
	ScopedObjectAccess soa(Thread::Current());
	names[0] = m->JniShortName();
	names[1] = m->JniLongName();
	}
	for (const std::string& mangled_name : names) {
	void* sym = dlsym(RTLD_DEFAULT, mangled_name.c_str());
	if (sym == nullptr) {
	continue;
	}

	JNINativeMethod native_method;
	native_method.fnPtr = sym;
	native_method.name = name;
	native_method.signature = signature;

	env->RegisterNatives(klass, &native_method, 1);

	jenv->Deallocate(reinterpret_cast<unsigned char*>(name));
	jenv->Deallocate(reinterpret_cast<unsigned char*>(signature));
	return;
	}

	LOG(FATAL) << "Could not find " << names[0];
	}

	static jclass FindClassWithSystemClassLoader(JNIEnv* env, const char* class_name) {
	// Find the system classloader.
	ScopedLocalRef<jclass> cl_klass(env, env->FindClass("java/lang/ClassLoader"));
	if (cl_klass.get() == nullptr) {
	return nullptr;
	}
	jmethodID getsystemclassloader_method = env->GetStaticMethodID(cl_klass.get(),
	"getSystemClassLoader",
	"()Ljava/lang/ClassLoader;");
	if (getsystemclassloader_method == nullptr) {
	return nullptr;
	}
	ScopedLocalRef<jobject> cl(env, env->CallStaticObjectMethod(cl_klass.get(),
	getsystemclassloader_method));
	if (cl.get() == nullptr) {
	return nullptr;
	}

	// Create a String of the name.
	std::string descriptor = android::base::StringPrintf("L%s;", class_name);
	std::string dot_name = DescriptorToDot(descriptor.c_str());
	ScopedLocalRef<jstring> name_str(env, env->NewStringUTF(dot_name.c_str()));

	// Call Class.forName with it.
	ScopedLocalRef<jclass> c_klass(env, env->FindClass("java/lang/Class"));
	if (c_klass.get() == nullptr) {
	return nullptr;
	}
	jmethodID forname_method = env->GetStaticMethodID(
	c_klass.get(),
	"forName",
	"(Ljava/lang/String;ZLjava/lang/ClassLoader;)Ljava/lang/Class;");
	if (forname_method == nullptr) {
	return nullptr;
	}

	return reinterpret_cast<jclass>(env->CallStaticObjectMethod(c_klass.get(),
	forname_method,
	name_str.get(),
	JNI_FALSE,
	cl.get()));
	}

	void BindFunctions(jvmtiEnv* jenv, JNIEnv* env, const char* class_name) {
	// Use JNI to load the class.
	ScopedLocalRef<jclass> klass(env, env->FindClass(class_name));
	if (klass.get() == nullptr) {
	// We may be called with the wrong classloader. Try explicitly using the system classloader.
	env->ExceptionClear();
	klass.reset(FindClassWithSystemClassLoader(env, class_name));
	if (klass.get() == nullptr) {
	LOG(FATAL) << "Could not load " << class_name;
	}
	}

	// Use JVMTI to get the methods.
	jint method_count;
	jmethodID* methods;
	jvmtiError methods_result = jenv->GetClassMethods(klass.get(), &method_count, &methods);
	if (methods_result != JVMTI_ERROR_NONE) {
	LOG(FATAL) << "Could not get methods";
	}

	// Check each method.
	for (jint i = 0; i < method_count; ++i) {
	jint modifiers;
	jvmtiError mod_result = jenv->GetMethodModifiers(methods[i], &modifiers);
	if (mod_result != JVMTI_ERROR_NONE) {
	LOG(FATAL) << "Could not get methods";
	}
	constexpr jint kNative = static_cast<jint>(kAccNative);
	if ((modifiers & kNative) != 0) {
	BindMethod(jenv, env, klass.get(), methods[i]);
	}
	}

	jenv->Deallocate(reinterpret_cast<unsigned char*>(methods));
	}

	} // namespace art