1 // Copyright (C) 2020 The Android Open Source Project
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 // http://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14
15 #include <android-base/logging.h>
16 #include <jni.h>
17 #include <jvmti.h>
18
19 #include <iostream>
20 #include <string_view>
21
22 namespace enablevlog {
23
24 namespace {
25
26 // Special art ti-version number. We will use this as a fallback if we cannot get a regular JVMTI
27 // env.
28 static constexpr jint kArtTiVersion = JVMTI_VERSION_1_2 | 0x40000000;
29
30 // The extension that lets us change the VLOG flags.
31 static constexpr std::string_view kSetVerboseExtensionName =
32 "com.android.art.misc.set_verbose_flag_ext";
33
34 // Extension prototype
35 using SetVerboseFlagExt = jvmtiError (*)(jvmtiEnv*, const char*, jboolean);
36
37 template <typename T>
Deallocate(jvmtiEnv * env,T * mem)38 static inline jvmtiError Deallocate(jvmtiEnv* env, T* mem) {
39 return env->Deallocate(reinterpret_cast<unsigned char*>(mem));
40 }
41
42 template <typename T>
Dealloc(jvmtiEnv * env,T * t)43 void Dealloc(jvmtiEnv* env, T* t) {
44 env->Deallocate(reinterpret_cast<unsigned char*>(t));
45 }
46
47 template <typename T, typename... Rest>
Dealloc(jvmtiEnv * env,T * t,Rest...rs)48 void Dealloc(jvmtiEnv* env, T* t, Rest... rs) {
49 Dealloc(env, t);
50 Dealloc(env, rs...);
51 }
52
DeallocParams(jvmtiEnv * env,jvmtiParamInfo * params,jint n_params)53 void DeallocParams(jvmtiEnv* env, jvmtiParamInfo* params, jint n_params) {
54 for (jint i = 0; i < n_params; i++) {
55 Dealloc(env, params[i].name);
56 }
57 }
58
59 template <typename T>
GetExtensionFunction(jvmtiEnv * jvmti,const std::string_view & name)60 T GetExtensionFunction(jvmtiEnv* jvmti, const std::string_view& name) {
61 jint n_ext = 0;
62 void* res = nullptr;
63 jvmtiExtensionFunctionInfo* infos = nullptr;
64 if (jvmti->GetExtensionFunctions(&n_ext, &infos) != JVMTI_ERROR_NONE) {
65 LOG(FATAL) << "Unable to get extensions";
66 }
67 for (jint i = 0; i < n_ext; i++) {
68 const jvmtiExtensionFunctionInfo& info = infos[i];
69 if (name == info.id) {
70 res = reinterpret_cast<void*>(info.func);
71 }
72 DeallocParams(jvmti, info.params, info.param_count);
73 Dealloc(jvmti, info.short_description, info.errors, info.id, info.params);
74 }
75 Dealloc(jvmti, infos);
76 return reinterpret_cast<T>(res);
77 }
78
SetupJvmtiEnv(JavaVM * vm,jvmtiEnv ** jvmti)79 static jint SetupJvmtiEnv(JavaVM* vm, jvmtiEnv** jvmti) {
80 jint res = 0;
81 res = vm->GetEnv(reinterpret_cast<void**>(jvmti), JVMTI_VERSION_1_1);
82
83 if (res != JNI_OK || *jvmti == nullptr) {
84 LOG(ERROR) << "Unable to access JVMTI, error code " << res;
85 return vm->GetEnv(reinterpret_cast<void**>(jvmti), kArtTiVersion);
86 }
87 return res;
88 }
89
90 } // namespace
91
AgentStart(JavaVM * vm,char * options,void * reserved ATTRIBUTE_UNUSED)92 static jint AgentStart(JavaVM* vm, char* options, void* reserved ATTRIBUTE_UNUSED) {
93 jvmtiEnv* jvmti = nullptr;
94 if (SetupJvmtiEnv(vm, &jvmti) != JNI_OK) {
95 LOG(ERROR) << "Could not get JVMTI env or ArtTiEnv!";
96 return JNI_ERR;
97 }
98 SetVerboseFlagExt svfe = GetExtensionFunction<SetVerboseFlagExt>(jvmti, kSetVerboseExtensionName);
99 if (svfe == nullptr) {
100 LOG(ERROR) << "Could not find extension " << kSetVerboseExtensionName;
101 return JNI_ERR;
102 } else if (svfe(jvmti, options, true) != JVMTI_ERROR_NONE) {
103 return JNI_ERR;
104 } else {
105 return JNI_OK;
106 }
107 }
108
109 // Late attachment (e.g. 'am attach-agent').
Agent_OnAttach(JavaVM * vm,char * options,void * reserved)110 extern "C" JNIEXPORT jint JNICALL Agent_OnAttach(JavaVM* vm, char* options, void* reserved) {
111 return AgentStart(vm, options, reserved);
112 }
113
114 // Early attachment
Agent_OnLoad(JavaVM * jvm,char * options,void * reserved)115 extern "C" JNIEXPORT jint JNICALL Agent_OnLoad(JavaVM* jvm, char* options, void* reserved) {
116 return AgentStart(jvm, options, reserved);
117 }
118
119 } // namespace enablevlog
120