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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 "instruction_decoder.h"
#include <android-base/logging.h>
#include <atomic>
#include <jni.h>
#include <jvmti.h>
#include <map>
#include <memory>
#include <mutex>
// We could probably return a JNI_ERR here but lets crash instead if something fails.
#define CHECK_JVMTI_ERROR(jvmti, errnum) \
CHECK_EQ(JVMTI_ERROR_NONE, (errnum)) << GetJvmtiErrorString((jvmti), (errnum)) << (" ")
namespace titrace {
static const char* GetJvmtiErrorString(jvmtiEnv* jvmti, jvmtiError errnum) {
char* errnum_str = nullptr;
jvmti->GetErrorName(errnum, /*out*/ &errnum_str);
if (errnum_str == nullptr) {
return "Unknown";
}
return errnum_str;
}
// Type-safe wrapper for JVMTI-allocated memory.
// Deallocates with jvmtiEnv::Deallocate.
template <typename T>
struct TiMemory {
explicit TiMemory(jvmtiEnv* env, T* mem, size_t size) : env_(env), mem_(mem), size_(size) {
}
~TiMemory() {
if (mem_ != nullptr) {
env_->Deallocate(static_cast<unsigned char*>(mem_));
}
mem_ = nullptr;
}
TiMemory(const TiMemory& other) = delete;
TiMemory(TiMemory&& other) {
env_ = other.env_;
mem_ = other.mem_;
size_ = other.size_;
if (this != &other) {
other.env_ = nullptr;
other.mem_ = nullptr;
other.size_ = 0u;
}
}
TiMemory& operator=(TiMemory&& other) {
if (mem_ != other.mem_) {
TiMemory::~TiMemory();
}
new (this) TiMemory(std::move(other));
return *this;
}
T* GetMemory() {
return mem_;
}
size_t Size() {
return size_ / sizeof(T);
}
private:
jvmtiEnv* env_;
T* mem_;
size_t size_;
};
struct MethodBytecode {
explicit MethodBytecode(jvmtiEnv* env, unsigned char* memory, jint size)
: bytecode_(env, memory, static_cast<size_t>(size)) {
}
TiMemory<uint8_t> bytecode_;
};
struct TraceStatistics {
static void Initialize(jvmtiEnv* jvmti) {
TraceStatistics& stats = GetSingleton();
bool is_ri = true;
{
jvmtiError error;
char* value_ptr;
error = jvmti->GetSystemProperty("java.vm.name", /*out*/ &value_ptr);
CHECK_JVMTI_ERROR(jvmti, error) << "Failed to get property 'java.vm.name'";
CHECK(value_ptr != nullptr) << "Returned property was null for 'java.vm.name'";
if (strcmp("Dalvik", value_ptr) == 0) {
is_ri = false;
}
}
InstructionFileFormat format =
is_ri ? InstructionFileFormat::kClass : InstructionFileFormat::kDex;
stats.instruction_decoder_.reset(InstructionDecoder::NewInstance(format));
CHECK_GE(arraysize(stats.instruction_counter_),
stats.instruction_decoder_->GetMaximumOpcode());
}
static TraceStatistics& GetSingleton() {
static TraceStatistics stats;
return stats;
}
void Log() {
LOG(INFO) << "================================================";
LOG(INFO) << " TI Trace // Summary ";
LOG(INFO) << "++++++++++++++++++++++++++++++++++++++++++++++++";
LOG(INFO) << " * Single step counter: " << single_step_counter_;
LOG(INFO) << "+++++++++++ Instructions Count ++++++++++++";
size_t total = single_step_counter_;
for (size_t i = 0; i < arraysize(instruction_counter_); ++i) {
size_t inst_count = instruction_counter_[i];
if (inst_count > 0) {
const char* opcode_name = instruction_decoder_->GetName(i);
LOG(INFO) << " * " << opcode_name << "(op:" << i << "), count: " << inst_count
<< ", % of total: " << (100.0 * inst_count / total);
}
}
LOG(INFO) << "------------------------------------------------";
}
void OnSingleStep(jvmtiEnv* jvmti_env, jmethodID method, jlocation location) {
// Counters do not need a happens-before.
// Use the weakest memory order simply to avoid tearing.
single_step_counter_.fetch_add(1u, std::memory_order_relaxed);
MethodBytecode& bytecode = LookupBytecode(jvmti_env, method);
// Decode jlocation value that depends on the bytecode format.
size_t actual_location = instruction_decoder_->LocationToOffset(static_cast<size_t>(location));
// Decode the exact instruction and increment its counter.
CHECK_LE(actual_location, bytecode.bytecode_.Size());
RecordInstruction(bytecode.bytecode_.GetMemory() + actual_location);
}
private:
void RecordInstruction(const uint8_t* instruction) {
uint8_t opcode = instruction[0];
// Counters do not need a happens-before.
// Use the weakest memory order simply to avoid tearing.
instruction_counter_[opcode].fetch_add(1u, std::memory_order_relaxed);
}
MethodBytecode& LookupBytecode(jvmtiEnv* jvmti_env, jmethodID method) {
jvmtiError error;
std::lock_guard<std::mutex> lock(bytecode_cache_mutex_);
auto it = bytecode_cache_.find(method);
if (it == bytecode_cache_.end()) {
jint bytecode_count_ptr = 0;
unsigned char* bytecodes_ptr = nullptr;
error = jvmti_env->GetBytecodes(method, &bytecode_count_ptr, &bytecodes_ptr);
CHECK_JVMTI_ERROR(jvmti_env, error) << "Failed to get bytecodes for method " << method;
CHECK(bytecodes_ptr != nullptr) << "Bytecode ptr was null for method " << method;
CHECK_GE(bytecode_count_ptr, 0) << "Bytecode size too small for method " << method;
// std::pair<iterator, bool inserted>
auto&& pair = bytecode_cache_.insert(
std::make_pair(method, MethodBytecode(jvmti_env, bytecodes_ptr, bytecode_count_ptr)));
it = pair.first;
}
// Returning the address is safe. if map is resized, the contents will not move.
return it->second;
}
std::unique_ptr<InstructionDecoder> instruction_decoder_;
std::atomic<size_t> single_step_counter_{0u};
std::atomic<size_t> instruction_counter_[256]{};
// Cache the bytecode to avoid calling into JVMTI repeatedly.
// TODO: invalidate if the bytecode was updated?
std::map<jmethodID, MethodBytecode> bytecode_cache_;
// bytecode cache is thread-safe.
std::mutex bytecode_cache_mutex_;
};
struct EventCallbacks {
static void SingleStep(jvmtiEnv* jvmti_env,
JNIEnv* jni_env ATTRIBUTE_UNUSED,
jthread thread ATTRIBUTE_UNUSED,
jmethodID method,
jlocation location) {
TraceStatistics& stats = TraceStatistics::GetSingleton();
stats.OnSingleStep(jvmti_env, method, location);
}
// Use "kill -SIGQUIT" to generate a data dump request.
// Useful when running an android app since it doesn't go through
// a normal Agent_OnUnload.
static void DataDumpRequest(jvmtiEnv* jvmti_env ATTRIBUTE_UNUSED) {
TraceStatistics& stats = TraceStatistics::GetSingleton();
stats.Log();
}
};
} // namespace titrace
// Late attachment (e.g. 'am attach-agent').
JNIEXPORT jint JNICALL Agent_OnAttach(JavaVM *vm, char* options, void* reserved) {
return Agent_OnLoad(vm, options, reserved);
}
// Early attachment (e.g. 'java -agent[lib|path]:filename.so').
JNIEXPORT jint JNICALL Agent_OnLoad(JavaVM* jvm,
char* /* options */,
void* /* reserved */) {
using namespace titrace; // NOLINT [build/namespaces] [5]
android::base::InitLogging(/* argv */nullptr);
jvmtiEnv* jvmti = nullptr;
{
jint res = 0;
res = jvm->GetEnv(reinterpret_cast<void**>(&jvmti), JVMTI_VERSION_1_1);
if (res != JNI_OK || jvmti == nullptr) {
LOG(FATAL) << "Unable to access JVMTI, error code " << res;
}
}
LOG(INFO) << "Agent_OnLoad: Hello World";
{
// Initialize our instruction file-format decoder.
TraceStatistics::Initialize(jvmti);
}
jvmtiError error{};
// Set capabilities.
{
jvmtiCapabilities caps = {};
caps.can_generate_single_step_events = 1;
caps.can_get_bytecodes = 1;
error = jvmti->AddCapabilities(&caps);
CHECK_JVMTI_ERROR(jvmti, error)
<< "Unable to get necessary JVMTI capabilities";
}
// Set callbacks.
{
jvmtiEventCallbacks callbacks = {};
callbacks.SingleStep = &EventCallbacks::SingleStep;
callbacks.DataDumpRequest = &EventCallbacks::DataDumpRequest;
error = jvmti->SetEventCallbacks(&callbacks,
static_cast<jint>(sizeof(callbacks)));
CHECK_JVMTI_ERROR(jvmti, error) << "Unable to set event callbacks";
}
// Enable events notification.
{
error = jvmti->SetEventNotificationMode(JVMTI_ENABLE,
JVMTI_EVENT_SINGLE_STEP,
nullptr /* all threads */);
CHECK_JVMTI_ERROR(jvmti, error)
<< "Failed to enable SINGLE_STEP notification";
error = jvmti->SetEventNotificationMode(JVMTI_ENABLE,
JVMTI_EVENT_DATA_DUMP_REQUEST,
nullptr /* all threads */);
CHECK_JVMTI_ERROR(jvmti, error)
<< "Failed to enable DATA_DUMP_REQUEST notification";
}
return JNI_OK;
}
// Note: This is not called for normal Android apps,
// use "kill -SIGQUIT" instead to generate a data dump request.
JNIEXPORT void JNICALL Agent_OnUnload(JavaVM* vm ATTRIBUTE_UNUSED) {
using namespace titrace; // NOLINT [build/namespaces] [5]
LOG(INFO) << "Agent_OnUnload: Goodbye";
TraceStatistics::GetSingleton().Log();
}