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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 <android-base/logging.h>
#include <dlfcn.h>
#include <jni.h>
#include <jvmti.h>
#include <atomic>
#include <fstream>
#include <iomanip>
#include <iostream>
#include <memory>
#include <mutex>
#include <sstream>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <vector>
namespace chainagents {
static constexpr const char* kChainFile = "chain_agents.txt";
static constexpr const char* kOnLoad = "Agent_OnLoad";
static constexpr const char* kOnAttach = "Agent_OnAttach";
static constexpr const char* kOnUnload = "Agent_OnUnload";
using AgentLoadFunction = jint (*)(JavaVM*, const char*, void*);
using AgentUnloadFunction = jint (*)(JavaVM*);
// Global namespace. Shared by every usage of this wrapper unfortunately.
// We need to keep track of them to call Agent_OnUnload.
static std::mutex unload_mutex;
struct Unloader {
AgentUnloadFunction unload;
};
static std::vector<Unloader> unload_functions;
enum class StartType {
OnAttach,
OnLoad,
};
static std::pair<std::string, std::string> Split(std::string source, char delim) {
std::string first(source.substr(0, source.find(delim)));
if (source.find(delim) == std::string::npos) {
return std::pair(first, "");
} else {
return std::pair(first, source.substr(source.find(delim) + 1));
}
}
static jint Load(StartType start,
JavaVM* vm,
void* reserved,
const std::pair<std::string, std::string>& lib_and_args,
/*out*/ std::string* err) {
void* handle = dlopen(lib_and_args.first.c_str(), RTLD_LAZY);
std::ostringstream oss;
if (handle == nullptr) {
oss << "Failed to dlopen due to " << dlerror();
*err = oss.str();
return JNI_ERR;
}
AgentLoadFunction alf = reinterpret_cast<AgentLoadFunction>(
dlsym(handle, start == StartType::OnLoad ? kOnLoad : kOnAttach));
if (alf == nullptr) {
oss << "Failed to dlsym " << (start == StartType::OnLoad ? kOnLoad : kOnAttach) << " due to "
<< dlerror();
*err = oss.str();
return JNI_ERR;
}
jint res = alf(vm, lib_and_args.second.c_str(), reserved);
if (res != JNI_OK) {
*err = "load function failed!";
return res;
}
AgentUnloadFunction auf = reinterpret_cast<AgentUnloadFunction>(dlsym(handle, kOnUnload));
if (auf != nullptr) {
unload_functions.push_back({ auf });
}
return JNI_OK;
}
static jint AgentStart(StartType start, JavaVM* vm, char* options, void* reserved) {
std::string input_file(options);
input_file = input_file + "/" + kChainFile;
std::ifstream input(input_file);
std::string line;
std::lock_guard<std::mutex> mu(unload_mutex);
while (std::getline(input, line)) {
std::pair<std::string, std::string> lib_and_args(Split(line, '='));
std::string err;
jint new_res = Load(start, vm, reserved, lib_and_args, &err);
if (new_res != JNI_OK) {
PLOG(WARNING) << "Failed to load library " << lib_and_args.first
<< " (arguments: " << lib_and_args.second << ") due to " << err;
}
}
return JNI_OK;
}
// Late attachment (e.g. 'am attach-agent').
extern "C" JNIEXPORT jint JNICALL Agent_OnAttach(JavaVM* vm, char* options, void* reserved) {
return AgentStart(StartType::OnAttach, vm, options, reserved);
}
// Early attachment
// (e.g. 'java
// -agentpath:/path/to/libwrapagentproperties.so=/path/to/propfile,/path/to/wrapped.so=[ops]').
extern "C" JNIEXPORT jint JNICALL Agent_OnLoad(JavaVM* jvm, char* options, void* reserved) {
return AgentStart(StartType::OnLoad, jvm, options, reserved);
}
extern "C" JNIEXPORT void JNICALL Agent_OnUnload(JavaVM* jvm) {
std::lock_guard<std::mutex> lk(unload_mutex);
for (const Unloader& u : unload_functions) {
u.unload(jvm);
// Don't dlclose since some agents expect to still have code loaded after this.
}
unload_functions.clear();
}
} // namespace chainagents
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