1 /*
2  * Copyright (C) 2008 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 "java_lang_VMClassLoader.h"
18 
19 #include "base/zip_archive.h"
20 #include "class_linker.h"
21 #include "base/transform_iterator.h"
22 #include "base/stl_util.h"
23 #include "dex/descriptors_names.h"
24 #include "dex/dex_file_loader.h"
25 #include "dex/utf.h"
26 #include "handle_scope-inl.h"
27 #include "jni/jni_internal.h"
28 #include "mirror/class_loader.h"
29 #include "mirror/object-inl.h"
30 #include "mirror/object_array-alloc-inl.h"
31 #include "native_util.h"
32 #include "nativehelper/jni_macros.h"
33 #include "nativehelper/scoped_local_ref.h"
34 #include "nativehelper/scoped_utf_chars.h"
35 #include "obj_ptr.h"
36 #include "scoped_fast_native_object_access-inl.h"
37 #include "string_array_utils.h"
38 #include "thread-inl.h"
39 #include "well_known_classes-inl.h"
40 
41 namespace art HIDDEN {
42 
43 // A class so we can be friends with ClassLinker and access internal methods.
44 class VMClassLoader {
45  public:
LookupClass(ClassLinker * cl,Thread * self,const char * descriptor,size_t hash,ObjPtr<mirror::ClassLoader> class_loader)46   static ObjPtr<mirror::Class> LookupClass(ClassLinker* cl,
47                                            Thread* self,
48                                            const char* descriptor,
49                                            size_t hash,
50                                            ObjPtr<mirror::ClassLoader> class_loader)
51       REQUIRES(!Locks::classlinker_classes_lock_)
52       REQUIRES_SHARED(Locks::mutator_lock_) {
53     return cl->LookupClass(self, descriptor, hash, class_loader);
54   }
55 
FindClassInPathClassLoader(ClassLinker * cl,Thread * self,const char * descriptor,size_t hash,Handle<mirror::ClassLoader> class_loader)56   static ObjPtr<mirror::Class> FindClassInPathClassLoader(ClassLinker* cl,
57                                                           Thread* self,
58                                                           const char* descriptor,
59                                                           size_t hash,
60                                                           Handle<mirror::ClassLoader> class_loader)
61       REQUIRES_SHARED(Locks::mutator_lock_) {
62     ObjPtr<mirror::Class> result;
63     if (cl->FindClassInBaseDexClassLoader(self, descriptor, hash, class_loader, &result)) {
64       DCHECK(!self->IsExceptionPending());
65       return result;
66     }
67     if (self->IsExceptionPending()) {
68       self->ClearException();
69     }
70     return nullptr;
71   }
72 };
73 
VMClassLoader_findLoadedClass(JNIEnv * env,jclass,jobject javaLoader,jstring javaName)74 static jclass VMClassLoader_findLoadedClass(JNIEnv* env, jclass, jobject javaLoader,
75                                             jstring javaName) {
76   ScopedFastNativeObjectAccess soa(env);
77   ObjPtr<mirror::ClassLoader> loader = soa.Decode<mirror::ClassLoader>(javaLoader);
78   ScopedUtfChars name(env, javaName);
79   if (name.c_str() == nullptr) {
80     return nullptr;
81   }
82   ClassLinker* cl = Runtime::Current()->GetClassLinker();
83 
84   // Compute hash once.
85   std::string descriptor(DotToDescriptor(name.c_str()));
86   const size_t descriptor_hash = ComputeModifiedUtf8Hash(descriptor.c_str());
87 
88   ObjPtr<mirror::Class> c = VMClassLoader::LookupClass(cl,
89                                                        soa.Self(),
90                                                        descriptor.c_str(),
91                                                        descriptor_hash,
92                                                        loader);
93   if (c != nullptr && c->IsResolved()) {
94     return soa.AddLocalReference<jclass>(c);
95   }
96   // If class is erroneous, throw the earlier failure, wrapped in certain cases. See b/28787733.
97   if (c != nullptr && c->IsErroneous()) {
98     cl->ThrowEarlierClassFailure(c);
99     Thread* self = soa.Self();
100     ObjPtr<mirror::Class> exception_class = self->GetException()->GetClass();
101     if (exception_class == WellKnownClasses::java_lang_IllegalAccessError ||
102         exception_class == WellKnownClasses::java_lang_NoClassDefFoundError) {
103       self->ThrowNewWrappedException("Ljava/lang/ClassNotFoundException;",
104                                      c->PrettyDescriptor().c_str());
105     }
106     return nullptr;
107   }
108 
109   // Hard-coded performance optimization: We know that all failed libcore calls to findLoadedClass
110   //                                      are followed by a call to the the classloader to actually
111   //                                      load the class.
112   if (loader != nullptr) {
113     // Try the common case.
114     StackHandleScope<1> hs(soa.Self());
115     c = VMClassLoader::FindClassInPathClassLoader(cl,
116                                                   soa.Self(),
117                                                   descriptor.c_str(),
118                                                   descriptor_hash,
119                                                   hs.NewHandle(loader));
120     if (c != nullptr) {
121       return soa.AddLocalReference<jclass>(c);
122     }
123   }
124 
125   // The class wasn't loaded, yet, and our fast-path did not apply (e.g., we didn't understand the
126   // classloader chain).
127   return nullptr;
128 }
129 
130 /*
131  * Returns an array of entries from the boot classpath that could contain resources.
132  */
VMClassLoader_getBootClassPathEntries(JNIEnv * env,jclass)133 static jobjectArray VMClassLoader_getBootClassPathEntries(JNIEnv* env, jclass) {
134   ClassLinker* class_linker = Runtime::Current()->GetClassLinker();
135   const std::vector<const DexFile*>& path = class_linker->GetBootClassPath();
136   auto is_base_dex = [](const DexFile* dex_file) {
137     return !DexFileLoader::IsMultiDexLocation(dex_file->GetLocation());
138   };
139   size_t jar_count = std::count_if(path.begin(), path.end(), is_base_dex);
140 
141   const DexFile* last_dex_file = nullptr;
142   auto dchecked_is_base_dex = [&](const DexFile* dex_file) {
143     // For multidex locations, e.g., x.jar!classes2.dex, we want to look into x.jar.
144     // But we do not need to look into the base dex file more than once so we filter
145     // out multidex locations using the fact that they follow the base location.
146     if (kIsDebugBuild) {
147       if (is_base_dex(dex_file)) {
148         CHECK_EQ(DexFileLoader::GetBaseLocation(dex_file->GetLocation().c_str()),
149                  dex_file->GetLocation());
150       } else {
151         CHECK(last_dex_file != nullptr);
152         CHECK_EQ(DexFileLoader::GetBaseLocation(dex_file->GetLocation().c_str()),
153                  DexFileLoader::GetBaseLocation(last_dex_file->GetLocation().c_str()));
154       }
155       last_dex_file = dex_file;
156     }
157     return is_base_dex(dex_file);
158   };
159   auto get_location = [](const DexFile* dex_file) { return dex_file->GetLocation(); };
160   ScopedObjectAccess soa(Thread::ForEnv(env));
161   return soa.AddLocalReference<jobjectArray>(CreateStringArray(
162       soa.Self(),
163       jar_count,
164       MakeTransformRange(Filter(path, dchecked_is_base_dex), get_location)));
165 }
166 
167 static JNINativeMethod gMethods[] = {
168   FAST_NATIVE_METHOD(VMClassLoader, findLoadedClass, "(Ljava/lang/ClassLoader;Ljava/lang/String;)Ljava/lang/Class;"),
169   NATIVE_METHOD(VMClassLoader, getBootClassPathEntries, "()[Ljava/lang/String;"),
170 };
171 
register_java_lang_VMClassLoader(JNIEnv * env)172 void register_java_lang_VMClassLoader(JNIEnv* env) {
173   REGISTER_NATIVE_METHODS("java/lang/VMClassLoader");
174 }
175 
176 }  // namespace art
177