1 /*
2 * Copyright (C) 2017 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #include "jni_binder.h"
18
19 #include <dlfcn.h>
20 #include <inttypes.h>
21 #include <stdio.h>
22
23 #include "android-base/logging.h"
24 #include "android-base/stringprintf.h"
25
26 #include "jvmti_helper.h"
27 #include "scoped_local_ref.h"
28 #include "scoped_utf_chars.h"
29 #include "ti_utf.h"
30
31 namespace art {
32
MangleForJni(const std::string & s)33 static std::string MangleForJni(const std::string& s) {
34 std::string result;
35 size_t char_count = ti::CountModifiedUtf8Chars(s.c_str(), s.length());
36 const char* cp = &s[0];
37 for (size_t i = 0; i < char_count; ++i) {
38 uint32_t ch = ti::GetUtf16FromUtf8(&cp);
39 if ((ch >= 'A' && ch <= 'Z') || (ch >= 'a' && ch <= 'z') || (ch >= '0' && ch <= '9')) {
40 result.push_back(ch);
41 } else if (ch == '.' || ch == '/') {
42 result += "_";
43 } else if (ch == '_') {
44 result += "_1";
45 } else if (ch == ';') {
46 result += "_2";
47 } else if (ch == '[') {
48 result += "_3";
49 } else {
50 const uint16_t leading = ti::GetLeadingUtf16Char(ch);
51 const uint32_t trailing = ti::GetTrailingUtf16Char(ch);
52
53 android::base::StringAppendF(&result, "_0%04x", leading);
54 if (trailing != 0) {
55 android::base::StringAppendF(&result, "_0%04x", trailing);
56 }
57 }
58 }
59 return result;
60 }
61
GetJniShortName(const std::string & class_descriptor,const std::string & method)62 static std::string GetJniShortName(const std::string& class_descriptor, const std::string& method) {
63 // Remove the leading 'L' and trailing ';'...
64 std::string class_name(class_descriptor);
65 CHECK_EQ(class_name[0], 'L') << class_name;
66 CHECK_EQ(class_name[class_name.size() - 1], ';') << class_name;
67 class_name.erase(0, 1);
68 class_name.erase(class_name.size() - 1, 1);
69
70 std::string short_name;
71 short_name += "Java_";
72 short_name += MangleForJni(class_name);
73 short_name += "_";
74 short_name += MangleForJni(method);
75 return short_name;
76 }
77
BindMethod(jvmtiEnv * jvmti_env,JNIEnv * env,jclass klass,jmethodID method)78 static void BindMethod(jvmtiEnv* jvmti_env, JNIEnv* env, jclass klass, jmethodID method) {
79 std::string name;
80 std::string signature;
81 std::string mangled_names[2];
82 {
83 char* name_cstr;
84 char* sig_cstr;
85 jvmtiError name_result = jvmti_env->GetMethodName(method, &name_cstr, &sig_cstr, nullptr);
86 CheckJvmtiError(jvmti_env, name_result);
87 CHECK(name_cstr != nullptr);
88 CHECK(sig_cstr != nullptr);
89 name = name_cstr;
90 signature = sig_cstr;
91
92 char* klass_name;
93 jvmtiError klass_result = jvmti_env->GetClassSignature(klass, &klass_name, nullptr);
94 CheckJvmtiError(jvmti_env, klass_result);
95
96 mangled_names[0] = GetJniShortName(klass_name, name);
97 // TODO: Long JNI name.
98
99 CheckJvmtiError(jvmti_env, Deallocate(jvmti_env, name_cstr));
100 CheckJvmtiError(jvmti_env, Deallocate(jvmti_env, sig_cstr));
101 CheckJvmtiError(jvmti_env, Deallocate(jvmti_env, klass_name));
102 }
103
104 for (const std::string& mangled_name : mangled_names) {
105 if (mangled_name.empty()) {
106 continue;
107 }
108 void* sym = dlsym(RTLD_DEFAULT, mangled_name.c_str());
109 if (sym == nullptr) {
110 continue;
111 }
112
113 JNINativeMethod native_method;
114 native_method.fnPtr = sym;
115 native_method.name = name.c_str();
116 native_method.signature = signature.c_str();
117
118 env->RegisterNatives(klass, &native_method, 1);
119
120 return;
121 }
122
123 LOG(FATAL) << "Could not find " << mangled_names[0];
124 }
125
DescriptorToDot(const char * descriptor)126 static std::string DescriptorToDot(const char* descriptor) {
127 size_t length = strlen(descriptor);
128 if (length > 1) {
129 if (descriptor[0] == 'L' && descriptor[length - 1] == ';') {
130 // Descriptors have the leading 'L' and trailing ';' stripped.
131 std::string result(descriptor + 1, length - 2);
132 std::replace(result.begin(), result.end(), '/', '.');
133 return result;
134 } else {
135 // For arrays the 'L' and ';' remain intact.
136 std::string result(descriptor);
137 std::replace(result.begin(), result.end(), '/', '.');
138 return result;
139 }
140 }
141 // Do nothing for non-class/array descriptors.
142 return descriptor;
143 }
144
GetSystemClassLoader(JNIEnv * env)145 static jobject GetSystemClassLoader(JNIEnv* env) {
146 ScopedLocalRef<jclass> cl_klass(env, env->FindClass("java/lang/ClassLoader"));
147 CHECK(cl_klass.get() != nullptr);
148 jmethodID getsystemclassloader_method = env->GetStaticMethodID(cl_klass.get(),
149 "getSystemClassLoader",
150 "()Ljava/lang/ClassLoader;");
151 CHECK(getsystemclassloader_method != nullptr);
152 return env->CallStaticObjectMethod(cl_klass.get(), getsystemclassloader_method);
153 }
154
FindClassWithClassLoader(JNIEnv * env,const char * class_name,jobject class_loader)155 static jclass FindClassWithClassLoader(JNIEnv* env, const char* class_name, jobject class_loader) {
156 // Create a String of the name.
157 std::string descriptor = android::base::StringPrintf("L%s;", class_name);
158 std::string dot_name = DescriptorToDot(descriptor.c_str());
159 ScopedLocalRef<jstring> name_str(env, env->NewStringUTF(dot_name.c_str()));
160
161 // Call Class.forName with it.
162 ScopedLocalRef<jclass> c_klass(env, env->FindClass("java/lang/Class"));
163 CHECK(c_klass.get() != nullptr);
164 jmethodID forname_method = env->GetStaticMethodID(
165 c_klass.get(),
166 "forName",
167 "(Ljava/lang/String;ZLjava/lang/ClassLoader;)Ljava/lang/Class;");
168 CHECK(forname_method != nullptr);
169
170 return static_cast<jclass>(env->CallStaticObjectMethod(c_klass.get(),
171 forname_method,
172 name_str.get(),
173 JNI_FALSE,
174 class_loader));
175 }
176
FindClass(jvmtiEnv * jvmti_env,JNIEnv * env,const char * class_name,jobject class_loader)177 jclass FindClass(jvmtiEnv* jvmti_env, JNIEnv* env, const char* class_name, jobject class_loader) {
178 if (class_loader != nullptr) {
179 return FindClassWithClassLoader(env, class_name, class_loader);
180 }
181
182 jclass from_implied = env->FindClass(class_name);
183 if (from_implied != nullptr) {
184 return from_implied;
185 }
186 env->ExceptionClear();
187
188 ScopedLocalRef<jobject> system_class_loader(env, GetSystemClassLoader(env));
189 CHECK(system_class_loader.get() != nullptr);
190 jclass from_system = FindClassWithClassLoader(env, class_name, system_class_loader.get());
191 if (from_system != nullptr) {
192 return from_system;
193 }
194 env->ExceptionClear();
195
196 // Look at the context classloaders of all threads.
197 jint thread_count;
198 jthread* threads;
199 CheckJvmtiError(jvmti_env, jvmti_env->GetAllThreads(&thread_count, &threads));
200 JvmtiUniquePtr threads_uptr = MakeJvmtiUniquePtr(jvmti_env, threads);
201
202 jclass result = nullptr;
203 for (jint t = 0; t != thread_count; ++t) {
204 // Always loop over all elements, as we need to free the local references.
205 if (result == nullptr) {
206 jvmtiThreadInfo info;
207 CheckJvmtiError(jvmti_env, jvmti_env->GetThreadInfo(threads[t], &info));
208 CheckJvmtiError(jvmti_env, Deallocate(jvmti_env, info.name));
209 if (info.thread_group != nullptr) {
210 env->DeleteLocalRef(info.thread_group);
211 }
212 if (info.context_class_loader != nullptr) {
213 result = FindClassWithClassLoader(env, class_name, info.context_class_loader);
214 env->ExceptionClear();
215 env->DeleteLocalRef(info.context_class_loader);
216 }
217 }
218 env->DeleteLocalRef(threads[t]);
219 }
220
221 if (result != nullptr) {
222 return result;
223 }
224
225 // TODO: Implement scanning *all* classloaders.
226 LOG(FATAL) << "Unimplemented";
227
228 return nullptr;
229 }
230
BindFunctionsOnClass(jvmtiEnv * jvmti_env,JNIEnv * env,jclass klass)231 void BindFunctionsOnClass(jvmtiEnv* jvmti_env, JNIEnv* env, jclass klass) {
232 // Use JVMTI to get the methods.
233 jint method_count;
234 jmethodID* methods;
235 jvmtiError methods_result = jvmti_env->GetClassMethods(klass, &method_count, &methods);
236 CheckJvmtiError(jvmti_env, methods_result);
237
238 // Check each method.
239 for (jint i = 0; i < method_count; ++i) {
240 jint modifiers;
241 jvmtiError mod_result = jvmti_env->GetMethodModifiers(methods[i], &modifiers);
242 CheckJvmtiError(jvmti_env, mod_result);
243 constexpr jint kNative = static_cast<jint>(0x0100);
244 if ((modifiers & kNative) != 0) {
245 BindMethod(jvmti_env, env, klass, methods[i]);
246 }
247 }
248
249 CheckJvmtiError(jvmti_env, Deallocate(jvmti_env, methods));
250 }
251
BindFunctions(jvmtiEnv * jvmti_env,JNIEnv * env,const char * class_name,jobject class_loader)252 void BindFunctions(jvmtiEnv* jvmti_env, JNIEnv* env, const char* class_name, jobject class_loader) {
253 // Use JNI to load the class.
254 ScopedLocalRef<jclass> klass(env, FindClass(jvmti_env, env, class_name, class_loader));
255 CHECK(klass.get() != nullptr) << class_name;
256 BindFunctionsOnClass(jvmti_env, env, klass.get());
257 }
258
259 } // namespace art
260