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219 lines
8.1 KiB
219 lines
8.1 KiB
// Copyright (C) 2018 The Android Open Source Project
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//
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#include <android-base/logging.h>
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#include <atomic>
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#include <iomanip>
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#include <iostream>
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#include <istream>
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#include <jni.h>
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#include <jvmti.h>
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#include <memory>
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#include <sstream>
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#include <string.h>
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#include <string>
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#include <vector>
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namespace fieldnull {
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#define CHECK_JVMTI(x) CHECK_EQ((x), JVMTI_ERROR_NONE)
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// Special art ti-version number. We will use this as a fallback if we cannot get a regular JVMTI
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// env.
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static constexpr jint kArtTiVersion = JVMTI_VERSION_1_2 | 0x40000000;
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static JavaVM* java_vm = nullptr;
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// Field is "Lclass/name/here;.field_name:Lfield/type/here;"
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static std::pair<jclass, jfieldID> SplitField(JNIEnv* env, const std::string& field_id) {
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CHECK_EQ(field_id[0], 'L');
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env->PushLocalFrame(1);
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std::istringstream is(field_id);
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std::string class_name;
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std::string field_name;
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std::string field_type;
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std::getline(is, class_name, '.');
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std::getline(is, field_name, ':');
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std::getline(is, field_type, '\0');
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jclass klass = reinterpret_cast<jclass>(
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env->NewGlobalRef(env->FindClass(class_name.substr(1, class_name.size() - 2).c_str())));
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jfieldID field = env->GetFieldID(klass, field_name.c_str(), field_type.c_str());
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CHECK(klass != nullptr);
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CHECK(field != nullptr);
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LOG(INFO) << "listing field " << field_id;
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env->PopLocalFrame(nullptr);
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return std::make_pair(klass, field);
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}
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static std::vector<std::pair<jclass, jfieldID>> GetRequestedFields(JNIEnv* env,
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const std::string& args) {
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std::vector<std::pair<jclass, jfieldID>> res;
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std::stringstream args_stream(args);
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std::string item;
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while (std::getline(args_stream, item, ',')) {
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if (item == "") {
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continue;
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}
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res.push_back(SplitField(env, item));
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}
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return res;
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}
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static jint SetupJvmtiEnv(JavaVM* vm, jvmtiEnv** jvmti) {
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jint res = 0;
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res = vm->GetEnv(reinterpret_cast<void**>(jvmti), JVMTI_VERSION_1_1);
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if (res != JNI_OK || *jvmti == nullptr) {
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LOG(ERROR) << "Unable to access JVMTI, error code " << res;
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return vm->GetEnv(reinterpret_cast<void**>(jvmti), kArtTiVersion);
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}
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return res;
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}
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struct RequestList {
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std::vector<std::pair<jclass, jfieldID>> fields_;
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};
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static void DataDumpRequestCb(jvmtiEnv* jvmti) {
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JNIEnv* env = nullptr;
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CHECK_EQ(java_vm->GetEnv(reinterpret_cast<void**>(&env), JNI_VERSION_1_6), JNI_OK);
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LOG(INFO) << "Dumping counts of null fields.";
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LOG(INFO) << "\t" << "Field name"
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<< "\t" << "null count"
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<< "\t" << "total count";
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RequestList* list;
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CHECK_JVMTI(jvmti->GetEnvironmentLocalStorage(reinterpret_cast<void**>(&list)));
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for (std::pair<jclass, jfieldID>& p : list->fields_) {
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jclass klass = p.first;
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jfieldID field = p.second;
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// Make sure all instances of the class are tagged with the klass ptr value. Since this is a
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// global ref it's guaranteed to be unique.
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CHECK_JVMTI(jvmti->IterateOverInstancesOfClass(
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p.first,
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// We need to do this to all objects every time since we might be looking for multiple
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// fields in classes that are subtypes of each other.
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JVMTI_HEAP_OBJECT_EITHER,
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/* class_tag, size, tag_ptr, user_data*/
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[](jlong, jlong, jlong* tag_ptr, void* klass) -> jvmtiIterationControl {
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*tag_ptr = static_cast<jlong>(reinterpret_cast<intptr_t>(klass));
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return JVMTI_ITERATION_CONTINUE;
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},
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klass));
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jobject* obj_list;
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jint obj_len;
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jlong tag = static_cast<jlong>(reinterpret_cast<intptr_t>(klass));
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CHECK_JVMTI(jvmti->GetObjectsWithTags(1, &tag, &obj_len, &obj_list, nullptr));
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uint64_t null_cnt = 0;
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for (jint i = 0; i < obj_len; i++) {
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if (env->GetObjectField(obj_list[i], field) == nullptr) {
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null_cnt++;
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}
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}
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char* field_name;
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char* field_sig;
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char* class_name;
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CHECK_JVMTI(jvmti->GetFieldName(klass, field, &field_name, &field_sig, nullptr));
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CHECK_JVMTI(jvmti->GetClassSignature(klass, &class_name, nullptr));
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LOG(INFO) << "\t" << class_name << "." << field_name << ":" << field_sig
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<< "\t" << null_cnt
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<< "\t" << obj_len;
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CHECK_JVMTI(jvmti->Deallocate(reinterpret_cast<unsigned char*>(field_name)));
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CHECK_JVMTI(jvmti->Deallocate(reinterpret_cast<unsigned char*>(field_sig)));
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CHECK_JVMTI(jvmti->Deallocate(reinterpret_cast<unsigned char*>(class_name)));
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}
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}
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static void VMDeathCb(jvmtiEnv* jvmti, JNIEnv* env ATTRIBUTE_UNUSED) {
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DataDumpRequestCb(jvmti);
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RequestList* list = nullptr;
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CHECK_JVMTI(jvmti->GetEnvironmentLocalStorage(reinterpret_cast<void**>(&list)));
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delete list;
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}
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static void CreateFieldList(jvmtiEnv* jvmti, JNIEnv* env, const std::string& args) {
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RequestList* list = nullptr;
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CHECK_JVMTI(jvmti->Allocate(sizeof(*list), reinterpret_cast<unsigned char**>(&list)));
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new (list) RequestList { .fields_ = GetRequestedFields(env, args), };
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CHECK_JVMTI(jvmti->SetEnvironmentLocalStorage(list));
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}
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static void VMInitCb(jvmtiEnv* jvmti, JNIEnv* env, jobject thr ATTRIBUTE_UNUSED) {
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char* args = nullptr;
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CHECK_JVMTI(jvmti->GetEnvironmentLocalStorage(reinterpret_cast<void**>(&args)));
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CHECK_JVMTI(jvmti->SetEnvironmentLocalStorage(nullptr));
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CreateFieldList(jvmti, env, args);
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CHECK_JVMTI(jvmti->SetEventNotificationMode(JVMTI_ENABLE, JVMTI_EVENT_VM_DEATH, nullptr));
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CHECK_JVMTI(jvmti->SetEventNotificationMode(JVMTI_ENABLE,
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JVMTI_EVENT_DATA_DUMP_REQUEST,
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nullptr));
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CHECK_JVMTI(jvmti->Deallocate(reinterpret_cast<unsigned char*>(args)));
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}
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static jint AgentStart(JavaVM* vm, char* options, bool is_onload) {
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android::base::InitLogging(/* argv= */nullptr);
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java_vm = vm;
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jvmtiEnv* jvmti = nullptr;
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if (SetupJvmtiEnv(vm, &jvmti) != JNI_OK) {
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LOG(ERROR) << "Could not get JVMTI env or ArtTiEnv!";
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return JNI_ERR;
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}
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jvmtiCapabilities caps { .can_tag_objects = 1, };
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CHECK_JVMTI(jvmti->AddCapabilities(&caps));
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jvmtiEventCallbacks cb {
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.VMInit = VMInitCb,
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.VMDeath = VMDeathCb,
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.DataDumpRequest = DataDumpRequestCb,
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};
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CHECK_JVMTI(jvmti->SetEventCallbacks(&cb, sizeof(cb)));
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if (is_onload) {
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unsigned char* ptr = nullptr;
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CHECK_JVMTI(jvmti->Allocate(strlen(options) + 1, &ptr));
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strcpy(reinterpret_cast<char*>(ptr), options);
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CHECK_JVMTI(jvmti->SetEnvironmentLocalStorage(ptr));
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CHECK_JVMTI(jvmti->SetEventNotificationMode(JVMTI_ENABLE, JVMTI_EVENT_VM_INIT, nullptr));
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} else {
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JNIEnv* env = nullptr;
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CHECK_EQ(vm->GetEnv(reinterpret_cast<void**>(&env), JNI_VERSION_1_6), JNI_OK);
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CreateFieldList(jvmti, env, options);
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CHECK_JVMTI(jvmti->SetEventNotificationMode(JVMTI_ENABLE, JVMTI_EVENT_VM_DEATH, nullptr));
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CHECK_JVMTI(jvmti->SetEventNotificationMode(JVMTI_ENABLE,
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JVMTI_EVENT_DATA_DUMP_REQUEST,
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nullptr));
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}
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return JNI_OK;
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}
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// Late attachment (e.g. 'am attach-agent').
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extern "C" JNIEXPORT jint JNICALL Agent_OnAttach(JavaVM *vm,
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char* options,
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void* reserved ATTRIBUTE_UNUSED) {
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return AgentStart(vm, options, /*is_onload=*/false);
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}
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// Early attachment
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extern "C" JNIEXPORT jint JNICALL Agent_OnLoad(JavaVM* jvm,
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char* options,
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void* reserved ATTRIBUTE_UNUSED) {
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return AgentStart(jvm, options, /*is_onload=*/true);
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}
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} // namespace fieldnull
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