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/*
* Copyright (C) 2017 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 "jni_binder.h"
#include <dlfcn.h>
#include <inttypes.h>
#include <stdio.h>
#include "android-base/logging.h"
#include "android-base/stringprintf.h"
#include "jvmti_helper.h"
#include "scoped_local_ref.h"
#include "scoped_utf_chars.h"
#include "ti_utf.h"
namespace art {
static std::string MangleForJni(const std::string& s) {
std::string result;
size_t char_count = ti::CountModifiedUtf8Chars(s.c_str(), s.length());
const char* cp = &s[0];
for (size_t i = 0; i < char_count; ++i) {
uint32_t ch = ti::GetUtf16FromUtf8(&cp);
if ((ch >= 'A' && ch <= 'Z') || (ch >= 'a' && ch <= 'z') || (ch >= '0' && ch <= '9')) {
result.push_back(ch);
} else if (ch == '.' || ch == '/') {
result += "_";
} else if (ch == '_') {
result += "_1";
} else if (ch == ';') {
result += "_2";
} else if (ch == '[') {
result += "_3";
} else {
const uint16_t leading = ti::GetLeadingUtf16Char(ch);
const uint32_t trailing = ti::GetTrailingUtf16Char(ch);
android::base::StringAppendF(&result, "_0%04x", leading);
if (trailing != 0) {
android::base::StringAppendF(&result, "_0%04x", trailing);
}
}
}
return result;
}
static std::string GetJniShortName(const std::string& class_descriptor, const std::string& method) {
// Remove the leading 'L' and trailing ';'...
std::string class_name(class_descriptor);
CHECK_EQ(class_name[0], 'L') << class_name;
CHECK_EQ(class_name[class_name.size() - 1], ';') << class_name;
class_name.erase(0, 1);
class_name.erase(class_name.size() - 1, 1);
std::string short_name;
short_name += "Java_";
short_name += MangleForJni(class_name);
short_name += "_";
short_name += MangleForJni(method);
return short_name;
}
static void BindMethod(jvmtiEnv* jvmti_env, JNIEnv* env, jclass klass, jmethodID method) {
std::string name;
std::string signature;
std::string mangled_names[2];
{
char* name_cstr;
char* sig_cstr;
jvmtiError name_result = jvmti_env->GetMethodName(method, &name_cstr, &sig_cstr, nullptr);
CheckJvmtiError(jvmti_env, name_result);
CHECK(name_cstr != nullptr);
CHECK(sig_cstr != nullptr);
name = name_cstr;
signature = sig_cstr;
char* klass_name;
jvmtiError klass_result = jvmti_env->GetClassSignature(klass, &klass_name, nullptr);
CheckJvmtiError(jvmti_env, klass_result);
mangled_names[0] = GetJniShortName(klass_name, name);
// TODO: Long JNI name.
CheckJvmtiError(jvmti_env, Deallocate(jvmti_env, name_cstr));
CheckJvmtiError(jvmti_env, Deallocate(jvmti_env, sig_cstr));
CheckJvmtiError(jvmti_env, Deallocate(jvmti_env, klass_name));
}
for (const std::string& mangled_name : mangled_names) {
if (mangled_name.empty()) {
continue;
}
void* sym = dlsym(RTLD_DEFAULT, mangled_name.c_str());
if (sym == nullptr) {
continue;
}
JNINativeMethod native_method;
native_method.fnPtr = sym;
native_method.name = name.c_str();
native_method.signature = signature.c_str();
env->RegisterNatives(klass, &native_method, 1);
return;
}
LOG(FATAL) << "Could not find " << mangled_names[0];
}
static std::string DescriptorToDot(const char* descriptor) {
size_t length = strlen(descriptor);
if (length > 1) {
if (descriptor[0] == 'L' && descriptor[length - 1] == ';') {
// Descriptors have the leading 'L' and trailing ';' stripped.
std::string result(descriptor + 1, length - 2);
std::replace(result.begin(), result.end(), '/', '.');
return result;
} else {
// For arrays the 'L' and ';' remain intact.
std::string result(descriptor);
std::replace(result.begin(), result.end(), '/', '.');
return result;
}
}
// Do nothing for non-class/array descriptors.
return descriptor;
}
static jobject GetSystemClassLoader(JNIEnv* env) {
ScopedLocalRef<jclass> cl_klass(env, env->FindClass("java/lang/ClassLoader"));
CHECK(cl_klass.get() != nullptr);
jmethodID getsystemclassloader_method = env->GetStaticMethodID(cl_klass.get(),
"getSystemClassLoader",
"()Ljava/lang/ClassLoader;");
CHECK(getsystemclassloader_method != nullptr);
return env->CallStaticObjectMethod(cl_klass.get(), getsystemclassloader_method);
}
static jclass FindClassWithClassLoader(JNIEnv* env, const char* class_name, jobject class_loader) {
// 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"));
CHECK(c_klass.get() != nullptr);
jmethodID forname_method = env->GetStaticMethodID(
c_klass.get(),
"forName",
"(Ljava/lang/String;ZLjava/lang/ClassLoader;)Ljava/lang/Class;");
CHECK(forname_method != nullptr);
return static_cast<jclass>(env->CallStaticObjectMethod(c_klass.get(),
forname_method,
name_str.get(),
JNI_FALSE,
class_loader));
}
jclass GetClass(jvmtiEnv* jvmti_env, JNIEnv* env, const char* class_name, jobject class_loader) {
if (class_loader != nullptr) {
return FindClassWithClassLoader(env, class_name, class_loader);
}
jclass from_implied = env->FindClass(class_name);
if (from_implied != nullptr) {
return from_implied;
}
env->ExceptionClear();
ScopedLocalRef<jobject> system_class_loader(env, GetSystemClassLoader(env));
CHECK(system_class_loader.get() != nullptr);
jclass from_system = FindClassWithClassLoader(env, class_name, system_class_loader.get());
if (from_system != nullptr) {
return from_system;
}
env->ExceptionClear();
// Look at the context classloaders of all threads.
jint thread_count;
jthread* threads;
CheckJvmtiError(jvmti_env, jvmti_env->GetAllThreads(&thread_count, &threads));
JvmtiUniquePtr threads_uptr = MakeJvmtiUniquePtr(jvmti_env, threads);
jclass result = nullptr;
for (jint t = 0; t != thread_count; ++t) {
// Always loop over all elements, as we need to free the local references.
if (result == nullptr) {
jvmtiThreadInfo info;
CheckJvmtiError(jvmti_env, jvmti_env->GetThreadInfo(threads[t], &info));
CheckJvmtiError(jvmti_env, Deallocate(jvmti_env, info.name));
if (info.thread_group != nullptr) {
env->DeleteLocalRef(info.thread_group);
}
if (info.context_class_loader != nullptr) {
result = FindClassWithClassLoader(env, class_name, info.context_class_loader);
env->ExceptionClear();
env->DeleteLocalRef(info.context_class_loader);
}
}
env->DeleteLocalRef(threads[t]);
}
if (result != nullptr) {
return result;
}
// TODO: Implement scanning *all* classloaders.
LOG(WARNING) << "Scanning all classloaders unimplemented";
return nullptr;
}
void BindFunctionsOnClass(jvmtiEnv* jvmti_env, JNIEnv* env, jclass klass) {
// Use JVMTI to get the methods.
jint method_count;
jmethodID* methods;
jvmtiError methods_result = jvmti_env->GetClassMethods(klass, &method_count, &methods);
CheckJvmtiError(jvmti_env, methods_result);
// Check each method.
for (jint i = 0; i < method_count; ++i) {
jint modifiers;
jvmtiError mod_result = jvmti_env->GetMethodModifiers(methods[i], &modifiers);
CheckJvmtiError(jvmti_env, mod_result);
constexpr jint kNative = static_cast<jint>(0x0100);
if ((modifiers & kNative) != 0) {
BindMethod(jvmti_env, env, klass, methods[i]);
}
}
CheckJvmtiError(jvmti_env, Deallocate(jvmti_env, methods));
}
void BindFunctions(jvmtiEnv* jvmti_env, JNIEnv* env, const char* class_name, jobject class_loader) {
// Use JNI to load the class.
ScopedLocalRef<jclass> klass(env, GetClass(jvmti_env, env, class_name, class_loader));
CHECK(klass.get() != nullptr) << class_name;
BindFunctionsOnClass(jvmti_env, env, klass.get());
}
} // namespace art