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/**
* Copyright 2015 Google Inc. All Rights Reserved.
*
* 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 "jvm_class_metadata_reader.h"
#include <algorithm>
#include "jni_utils.h"
#include "jvm_instance_field_reader.h"
#include "jvm_static_field_reader.h"
#include "jvmti_buffer.h"
#include "jni_proxy_object.h"
namespace devtools {
namespace cdbg {
static void ReleaseEntryRefs(jobject cls, ClassMetadataReader::Entry* entry) {
for (auto& static_field_reader : entry->static_fields) {
static_field_reader->ReleaseRef();
}
}
JvmClassMetadataReader::JvmClassMetadataReader(
MemberVisibilityPolicy* member_visibility_policy)
: member_visibility_policy_(member_visibility_policy),
cls_cache_(ReleaseEntryRefs) {
}
JvmClassMetadataReader::~JvmClassMetadataReader() {
}
const ClassMetadataReader::Entry&
JvmClassMetadataReader::GetClassMetadata(jclass cls) {
// Safeguard against null references.
DCHECK(cls != nullptr);
if (cls == nullptr) {
static Entry empty_class_metadata;
return empty_class_metadata;
}
// Case 1: the class information is cached.
{
MutexLock reader_lock(&mu_);
const Entry* metadata = cls_cache_.Find(cls);
if (metadata != nullptr) {
// It is safe to return reference to "jobject_map" entry. "jobject_map"
// guarantees that the elements are not moved when data structure is
// expanded or contracted.
return *metadata;
}
}
// Case 2: we need to load the class information.
{
Entry metadata;
LoadClassMetadata(cls, &metadata);
{
MutexLock writer_lock(&mu_);
cls_cache_.Insert(cls, std::move(metadata));
// Return currently or previously inserted entry. Returning reference to
// "jobject_map" entry as in case 1.
return *cls_cache_.Find(cls);
}
}
}
void JvmClassMetadataReader::LoadClassMetadata(jclass cls, Entry* metadata) {
string signature = GetClassSignature(cls);
if (signature.empty()) {
return;
}
metadata->signature = JSignatureFromSignature(signature);
// Start from the current class and go down the inheritance chain.
JniLocalRef current_class_ref = JniNewLocalRef(cls);
// Maintain set of methods we discovered in superclasses to ignore those
// in base classes. The pair stores method name and signature.
std::set<std::pair<string, string>> registered_methods;
while (current_class_ref != nullptr) {
LoadSingleClassMetadata(
static_cast<jclass>(current_class_ref.get()),
®istered_methods,
metadata);
LoadImplementedInterfacesMetadata(
static_cast<jclass>(current_class_ref.get()),
®istered_methods,
metadata);
// Free the current local reference and allocate a new local reference
// corresponding to the superclass of "current_class_ref".
JniLocalRef next(
jni()->GetSuperclass(static_cast<jclass>(current_class_ref.get())));
// Don't skip "java.lang.Object" even if "cls" is an interface.
if ((next == nullptr) &&
!jni()->IsSameObject(current_class_ref.get(),
jniproxy::Object()->GetClass())) {
LoadSingleClassMetadata(
jniproxy::Object()->GetClass(),
®istered_methods,
metadata);
}
current_class_ref = std::move(next);
}
// Reverse the the lists to accomodate for LoadFieldInfo appending new
// elements to the end of the list.
std::reverse(
metadata->instance_fields.begin(),
metadata->instance_fields.end());
std::reverse(
metadata->static_fields.begin(),
metadata->static_fields.end());
}
void JvmClassMetadataReader::LoadImplementedInterfacesMetadata(
jclass parent,
std::set<std::pair<string, string>>* registered_methods,
Entry* metadata) {
jvmtiError err = JVMTI_ERROR_NONE;
jint count = 0;
JvmtiBuffer<jclass> interfaces;
err = jvmti()->GetImplementedInterfaces(parent, &count, interfaces.ref());
if (err != JVMTI_ERROR_NONE) {
LOG(ERROR) << "GetImplementedInterfaces failed, error: " << err;
return;
}
for (int i = 0; i < count; ++i) {
jclass interface = interfaces.get()[i];
LoadSingleClassMetadata(interface, registered_methods, metadata);
LoadImplementedInterfacesMetadata(interface, registered_methods, metadata);
}
}
void JvmClassMetadataReader::LoadSingleClassMetadata(
jclass cls,
std::set<std::pair<string, string>>* registered_methods,
Entry* metadata) {
jvmtiError err = JVMTI_ERROR_NONE;
string class_signature = GetClassSignature(cls);
if (class_signature.empty()) {
return;
}
// Load list of all the fields of the class. This includes both member
// and static fields.
jint cls_fields_count = 0;
JvmtiBuffer<jfieldID> cls_fields;
err = jvmti()->GetClassFields(cls, &cls_fields_count, cls_fields.ref());
if (err != JVMTI_ERROR_NONE) {
LOG(ERROR) << "GetClassFields failed, error: " << err;
} else {
// Walk fields in reverse order so that the fields from the base class
// show up before the fields from the subclass.
for (int i = cls_fields_count - 1; i >= 0; --i) {
LoadFieldInfo(
cls,
class_signature,
cls_fields.get()[i],
metadata);
}
}
// Load list of all the methods of the class.
jint methods_count = 0;
JvmtiBuffer<jmethodID> methods;
err = jvmti()->GetClassMethods(
cls,
&methods_count,
methods.ref());
if (err != JVMTI_ERROR_NONE) {
LOG(ERROR) << "GetClassMethods failed, error: " << err;
} else {
// Load metadata of each method. We don't care about the order of methods
// in the list.
for (int i = 0; i < methods_count; ++i) {
Method method_metadata = LoadMethodInfo(
cls,
class_signature,
methods.get()[i]);
if (method_metadata.name.empty()) {
continue;
}
// If two instance methods have the same arguments, the one in the
// superclass overrides the one in the base class. This will be true
// even if return types are difference (this is called covariance).
std::pair<string, string> key;
if (method_metadata.is_static()) {
key = {
method_metadata.name,
method_metadata.signature
};
} else {
key = {
method_metadata.name,
TrimReturnType(method_metadata.signature)
};
}
// Skip base class methods that the inherited classes overwrote.
if (registered_methods->find(key) != registered_methods->end()) {
continue;
}
// Add the method to the registry.
registered_methods->insert(std::move(key));
metadata->methods.push_back(std::move(method_metadata));
}
}
}
void JvmClassMetadataReader::LoadFieldInfo(
jclass cls,
const string& class_signature,
jfieldID field_id,
Entry* metadata) {
int err = JVMTI_ERROR_NONE;
jint field_modifiers = 0;
err = jvmti()->GetFieldModifiers(cls, field_id, &field_modifiers);
if (err != JVMTI_ERROR_NONE) {
LOG(ERROR) << "GetFieldModifiers failed, error: " << err;
return;
}
JvmtiBuffer<char> field_name_buffer;
JvmtiBuffer<char> field_signature_buffer;
err = jvmti()->GetFieldName(
cls,
field_id,
field_name_buffer.ref(),
field_signature_buffer.ref(),
nullptr);
if (err != JVMTI_ERROR_NONE) {
LOG(ERROR) << "GetFieldName failed, error: " << err;
return;
}
if ((field_signature_buffer.get() == nullptr) ||
(field_signature_buffer.get()[0] == '\0')) {
LOG(ERROR) << "Empty field signature is unexpected";
return;
}
string field_name = field_name_buffer.get();
string field_signature = field_signature_buffer.get();
if (!member_visibility_policy_->IsFieldDebuggerVisible(
cls,
class_signature,
field_modifiers,
field_name,
field_signature)) {
if ((field_modifiers & JVM_ACC_STATIC) == 0) {
metadata->instance_fields_omitted = true;
}
return; // Field is invisible.
}
if ((field_modifiers & JVM_ACC_STATIC) == 0) {
// Instance field.
std::unique_ptr<InstanceFieldReader> reader(
new JvmInstanceFieldReader(
field_name,
field_id,
JSignatureFromSignature(field_signature)));
metadata->instance_fields.push_back(std::move(reader));
} else {
// Static field.
std::unique_ptr<StaticFieldReader> reader(
new JvmStaticFieldReader(
cls,
field_name,
field_id,
JSignatureFromSignature(field_signature)));
metadata->static_fields.push_back(std::move(reader));
}
}
JvmClassMetadataReader::Method JvmClassMetadataReader::LoadMethodInfo(
jclass cls,
const string& class_signature,
jmethodID method_id) {
int err = JVMTI_ERROR_NONE;
JvmtiBuffer<char> method_name;
JvmtiBuffer<char> method_signature;
err = jvmti()->GetMethodName(
method_id,
method_name.ref(),
method_signature.ref(),
nullptr);
if (err != JVMTI_ERROR_NONE) {
LOG(ERROR) << "GetMethodName failed, error: " << err;
return Method();
}
jint method_modifiers = 0;
err = jvmti()->GetMethodModifiers(method_id, &method_modifiers);
if (err != JVMTI_ERROR_NONE) {
LOG(ERROR) << "GetMethodModifiers failed, error: " << err;
return Method();
}
Method method;
method.class_signature = JSignatureFromSignature(class_signature);
method.name = method_name.get();
method.signature = method_signature.get();
method.modifiers = method_modifiers;
if (!member_visibility_policy_->IsMethodDebuggerVisible(
cls,
class_signature,
method_modifiers,
method.name,
method.signature)) {
return Method(); // Method is invisible.
}
return method;
}
} // namespace cdbg
} // namespace devtools
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