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// Copyright (C) 2020 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 <jni.h>
#include <jvmti.h>
#include <iostream>
#include <string_view>
namespace enablevlog {
namespace {
// Special art ti-version number. We will use this as a fallback if we cannot get a regular JVMTI
// env.
static constexpr jint kArtTiVersion = JVMTI_VERSION_1_2 | 0x40000000;
// The extension that lets us change the VLOG flags.
static constexpr std::string_view kSetVerboseExtensionName =
"com.android.art.misc.set_verbose_flag_ext";
// Extension prototype
using SetVerboseFlagExt = jvmtiError (*)(jvmtiEnv*, const char*, jboolean);
template <typename T>
static inline jvmtiError Deallocate(jvmtiEnv* env, T* mem) {
return env->Deallocate(reinterpret_cast<unsigned char*>(mem));
}
template <typename T>
void Dealloc(jvmtiEnv* env, T* t) {
env->Deallocate(reinterpret_cast<unsigned char*>(t));
}
template <typename T, typename... Rest>
void Dealloc(jvmtiEnv* env, T* t, Rest... rs) {
Dealloc(env, t);
Dealloc(env, rs...);
}
void DeallocParams(jvmtiEnv* env, jvmtiParamInfo* params, jint n_params) {
for (jint i = 0; i < n_params; i++) {
Dealloc(env, params[i].name);
}
}
template <typename T>
T GetExtensionFunction(jvmtiEnv* jvmti, const std::string_view& name) {
jint n_ext = 0;
void* res = nullptr;
jvmtiExtensionFunctionInfo* infos = nullptr;
if (jvmti->GetExtensionFunctions(&n_ext, &infos) != JVMTI_ERROR_NONE) {
LOG(FATAL) << "Unable to get extensions";
}
for (jint i = 0; i < n_ext; i++) {
const jvmtiExtensionFunctionInfo& info = infos[i];
if (name == info.id) {
res = reinterpret_cast<void*>(info.func);
}
DeallocParams(jvmti, info.params, info.param_count);
Dealloc(jvmti, info.short_description, info.errors, info.id, info.params);
}
Dealloc(jvmti, infos);
return reinterpret_cast<T>(res);
}
static jint SetupJvmtiEnv(JavaVM* vm, jvmtiEnv** jvmti) {
jint res = 0;
res = vm->GetEnv(reinterpret_cast<void**>(jvmti), JVMTI_VERSION_1_1);
if (res != JNI_OK || *jvmti == nullptr) {
LOG(ERROR) << "Unable to access JVMTI, error code " << res;
return vm->GetEnv(reinterpret_cast<void**>(jvmti), kArtTiVersion);
}
return res;
}
} // namespace
static jint AgentStart(JavaVM* vm, char* options, void* reserved ATTRIBUTE_UNUSED) {
jvmtiEnv* jvmti = nullptr;
if (SetupJvmtiEnv(vm, &jvmti) != JNI_OK) {
LOG(ERROR) << "Could not get JVMTI env or ArtTiEnv!";
return JNI_ERR;
}
SetVerboseFlagExt svfe = GetExtensionFunction<SetVerboseFlagExt>(jvmti, kSetVerboseExtensionName);
if (svfe == nullptr) {
LOG(ERROR) << "Could not find extension " << kSetVerboseExtensionName;
return JNI_ERR;
} else if (svfe(jvmti, options, true) != JVMTI_ERROR_NONE) {
return JNI_ERR;
} else {
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(vm, options, reserved);
}
// Early attachment
extern "C" JNIEXPORT jint JNICALL Agent_OnLoad(JavaVM* jvm, char* options, void* reserved) {
return AgentStart(jvm, options, reserved);
}
} // namespace enablevlog
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