Wire up check JNI force copy mode.

Increase check JNI checks.
Break apart jni_internal.h in to jni_env_ext.h and java_vm_ext.h.
Fix the abuse of ScopedObjectAccess/annotalysis by ScopedCheck in the case
of VM routines.
Make class loader override and shared library class loader JNI global
references rather than mirror pointers.
Clean-ups to native bridge.

Change-Id: If7c6110b5aade7a402bfb67534af86a7b2cdeb55

1 files changed, 829 insertions, 0 deletions

diff --git a/runtime/java_vm_ext.cc b/runtime/java_vm_ext.cc
new file mode 100644
index 0000000000..9eab3fde13
--- /dev/null
+++ b/runtime/java_vm_ext.cc
@@ -0,0 +1,829 @@
+/*
+ * Copyright (C) 2011 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 "jni_internal.h"
+
+#include <dlfcn.h>
+
+#include "base/mutex.h"
+#include "base/stl_util.h"
+#include "check_jni.h"
+#include "indirect_reference_table-inl.h"
+#include "mirror/art_method.h"
+#include "mirror/class-inl.h"
+#include "mirror/class_loader.h"
+#include "native_bridge.h"
+#include "java_vm_ext.h"
+#include "parsed_options.h"
+#include "ScopedLocalRef.h"
+#include "scoped_thread_state_change.h"
+#include "thread-inl.h"
+#include "thread_list.h"
+
+namespace art {
+
+static const size_t kPinTableInitial = 16;  // Arbitrary.
+static const size_t kPinTableMax = 1024;  // Arbitrary sanity check.
+
+static size_t gGlobalsInitial = 512;  // Arbitrary.
+static size_t gGlobalsMax = 51200;  // Arbitrary sanity check. (Must fit in 16 bits.)
+
+static const size_t kWeakGlobalsInitial = 16;  // Arbitrary.
+static const size_t kWeakGlobalsMax = 51200;  // Arbitrary sanity check. (Must fit in 16 bits.)
+
+static bool IsBadJniVersion(int version) {
+  // We don't support JNI_VERSION_1_1. These are the only other valid versions.
+  return version != JNI_VERSION_1_2 && version != JNI_VERSION_1_4 && version != JNI_VERSION_1_6;
+}
+
+class SharedLibrary {
+ public:
+  SharedLibrary(JNIEnv* env, Thread* self, const std::string& path, void* handle,
+                jobject class_loader)
+      : path_(path),
+        handle_(handle),
+        needs_native_bridge_(false),
+        class_loader_(env->NewGlobalRef(class_loader)),
+        jni_on_load_lock_("JNI_OnLoad lock"),
+        jni_on_load_cond_("JNI_OnLoad condition variable", jni_on_load_lock_),
+        jni_on_load_thread_id_(self->GetThreadId()),
+        jni_on_load_result_(kPending) {
+  }
+
+  ~SharedLibrary() {
+    Thread* self = Thread::Current();
+    if (self != nullptr) {
+      self->GetJniEnv()->DeleteGlobalRef(class_loader_);
+    }
+  }
+
+  jobject GetClassLoader() const {
+    return class_loader_;
+  }
+
+  const std::string& GetPath() const {
+    return path_;
+  }
+
+  /*
+   * Check the result of an earlier call to JNI_OnLoad on this library.
+   * If the call has not yet finished in another thread, wait for it.
+   */
+  bool CheckOnLoadResult()
+      LOCKS_EXCLUDED(jni_on_load_lock_) {
+    Thread* self = Thread::Current();
+    bool okay;
+    {
+      MutexLock mu(self, jni_on_load_lock_);
+
+      if (jni_on_load_thread_id_ == self->GetThreadId()) {
+        // Check this so we don't end up waiting for ourselves.  We need to return "true" so the
+        // caller can continue.
+        LOG(INFO) << *self << " recursive attempt to load library " << "\"" << path_ << "\"";
+        okay = true;
+      } else {
+        while (jni_on_load_result_ == kPending) {
+          VLOG(jni) << "[" << *self << " waiting for \"" << path_ << "\" " << "JNI_OnLoad...]";
+          jni_on_load_cond_.Wait(self);
+        }
+
+        okay = (jni_on_load_result_ == kOkay);
+        VLOG(jni) << "[Earlier JNI_OnLoad for \"" << path_ << "\" "
+            << (okay ? "succeeded" : "failed") << "]";
+      }
+    }
+    return okay;
+  }
+
+  void SetResult(bool result) LOCKS_EXCLUDED(jni_on_load_lock_) {
+    Thread* self = Thread::Current();
+    MutexLock mu(self, jni_on_load_lock_);
+
+    jni_on_load_result_ = result ? kOkay : kFailed;
+    jni_on_load_thread_id_ = 0;
+
+    // Broadcast a wakeup to anybody sleeping on the condition variable.
+    jni_on_load_cond_.Broadcast(self);
+  }
+
+  void SetNeedsNativeBridge() {
+    needs_native_bridge_ = true;
+  }
+
+  bool NeedsNativeBridge() const {
+    return needs_native_bridge_;
+  }
+
+  void* FindSymbol(const std::string& symbol_name) {
+    return dlsym(handle_, symbol_name.c_str());
+  }
+
+  void* FindSymbolWithNativeBridge(const std::string& symbol_name, const char* shorty) {
+    CHECK(NeedsNativeBridge());
+
+    uint32_t len = 0;
+    return NativeBridgeGetTrampoline(handle_, symbol_name.c_str(), shorty, len);
+  }
+
+ private:
+  enum JNI_OnLoadState {
+    kPending,
+    kFailed,
+    kOkay,
+  };
+
+  // Path to library "/system/lib/libjni.so".
+  const std::string path_;
+
+  // The void* returned by dlopen(3).
+  void* const handle_;
+
+  // True if a native bridge is required.
+  bool needs_native_bridge_;
+
+  // The ClassLoader this library is associated with, a global JNI reference that is
+  // created/deleted with the scope of the library.
+  const jobject class_loader_;
+
+  // Guards remaining items.
+  Mutex jni_on_load_lock_ DEFAULT_MUTEX_ACQUIRED_AFTER;
+  // Wait for JNI_OnLoad in other thread.
+  ConditionVariable jni_on_load_cond_ GUARDED_BY(jni_on_load_lock_);
+  // Recursive invocation guard.
+  uint32_t jni_on_load_thread_id_ GUARDED_BY(jni_on_load_lock_);
+  // Result of earlier JNI_OnLoad call.
+  JNI_OnLoadState jni_on_load_result_ GUARDED_BY(jni_on_load_lock_);
+};
+
+// This exists mainly to keep implementation details out of the header file.
+class Libraries {
+ public:
+  Libraries() {
+  }
+
+  ~Libraries() {
+    STLDeleteValues(&libraries_);
+  }
+
+  void Dump(std::ostream& os) const {
+    bool first = true;
+    for (const auto& library : libraries_) {
+      if (!first) {
+        os << ' ';
+      }
+      first = false;
+      os << library.first;
+    }
+  }
+
+  size_t size() const {
+    return libraries_.size();
+  }
+
+  SharedLibrary* Get(const std::string& path) {
+    auto it = libraries_.find(path);
+    return (it == libraries_.end()) ? nullptr : it->second;
+  }
+
+  void Put(const std::string& path, SharedLibrary* library) {
+    libraries_.Put(path, library);
+  }
+
+  // See section 11.3 "Linking Native Methods" of the JNI spec.
+  void* FindNativeMethod(mirror::ArtMethod* m, std::string& detail)
+      EXCLUSIVE_LOCKS_REQUIRED(Locks::jni_libraries_lock_)
+      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
+    std::string jni_short_name(JniShortName(m));
+    std::string jni_long_name(JniLongName(m));
+    const mirror::ClassLoader* declaring_class_loader = m->GetDeclaringClass()->GetClassLoader();
+    ScopedObjectAccessUnchecked soa(Thread::Current());
+    for (const auto& lib : libraries_) {
+      SharedLibrary* library = lib.second;
+      if (soa.Decode<mirror::ClassLoader*>(library->GetClassLoader()) != declaring_class_loader) {
+        // We only search libraries loaded by the appropriate ClassLoader.
+        continue;
+      }
+      // Try the short name then the long name...
+      void* fn;
+      if (library->NeedsNativeBridge()) {
+        const char* shorty = m->GetShorty();
+        fn = library->FindSymbolWithNativeBridge(jni_short_name, shorty);
+        if (fn == nullptr) {
+          fn = library->FindSymbolWithNativeBridge(jni_long_name, shorty);
+        }
+      } else {
+        fn = library->FindSymbol(jni_short_name);
+        if (fn == nullptr) {
+          fn = library->FindSymbol(jni_long_name);
+        }
+      }
+      if (fn == nullptr) {
+        fn = library->FindSymbol(jni_long_name);
+      }
+      if (fn != nullptr) {
+        VLOG(jni) << "[Found native code for " << PrettyMethod(m)
+                  << " in \"" << library->GetPath() << "\"]";
+        return fn;
+      }
+    }
+    detail += "No implementation found for ";
+    detail += PrettyMethod(m);
+    detail += " (tried " + jni_short_name + " and " + jni_long_name + ")";
+    LOG(ERROR) << detail;
+    return nullptr;
+  }
+
+ private:
+  SafeMap<std::string, SharedLibrary*> libraries_;
+};
+
+
+class JII {
+ public:
+  static jint DestroyJavaVM(JavaVM* vm) {
+    if (vm == nullptr) {
+      return JNI_ERR;
+    }
+    JavaVMExt* raw_vm = reinterpret_cast<JavaVMExt*>(vm);
+    delete raw_vm->GetRuntime();
+    return JNI_OK;
+  }
+
+  static jint AttachCurrentThread(JavaVM* vm, JNIEnv** p_env, void* thr_args) {
+    return AttachCurrentThreadInternal(vm, p_env, thr_args, false);
+  }
+
+  static jint AttachCurrentThreadAsDaemon(JavaVM* vm, JNIEnv** p_env, void* thr_args) {
+    return AttachCurrentThreadInternal(vm, p_env, thr_args, true);
+  }
+
+  static jint DetachCurrentThread(JavaVM* vm) {
+    if (vm == nullptr || Thread::Current() == nullptr) {
+      return JNI_ERR;
+    }
+    JavaVMExt* raw_vm = reinterpret_cast<JavaVMExt*>(vm);
+    Runtime* runtime = raw_vm->GetRuntime();
+    runtime->DetachCurrentThread();
+    return JNI_OK;
+  }
+
+  static jint GetEnv(JavaVM* vm, void** env, jint version) {
+    // GetEnv always returns a JNIEnv* for the most current supported JNI version,
+    // and unlike other calls that take a JNI version doesn't care if you supply
+    // JNI_VERSION_1_1, which we don't otherwise support.
+    if (IsBadJniVersion(version) && version != JNI_VERSION_1_1) {
+      LOG(ERROR) << "Bad JNI version passed to GetEnv: " << version;
+      return JNI_EVERSION;
+    }
+    if (vm == nullptr || env == nullptr) {
+      return JNI_ERR;
+    }
+    Thread* thread = Thread::Current();
+    if (thread == nullptr) {
+      *env = nullptr;
+      return JNI_EDETACHED;
+    }
+    *env = thread->GetJniEnv();
+    return JNI_OK;
+  }
+
+ private:
+  static jint AttachCurrentThreadInternal(JavaVM* vm, JNIEnv** p_env, void* raw_args, bool as_daemon) {
+    if (vm == nullptr || p_env == nullptr) {
+      return JNI_ERR;
+    }
+
+    // Return immediately if we're already attached.
+    Thread* self = Thread::Current();
+    if (self != nullptr) {
+      *p_env = self->GetJniEnv();
+      return JNI_OK;
+    }
+
+    Runtime* runtime = reinterpret_cast<JavaVMExt*>(vm)->GetRuntime();
+
+    // No threads allowed in zygote mode.
+    if (runtime->IsZygote()) {
+      LOG(ERROR) << "Attempt to attach a thread in the zygote";
+      return JNI_ERR;
+    }
+
+    JavaVMAttachArgs* args = static_cast<JavaVMAttachArgs*>(raw_args);
+    const char* thread_name = nullptr;
+    jobject thread_group = nullptr;
+    if (args != nullptr) {
+      if (IsBadJniVersion(args->version)) {
+        LOG(ERROR) << "Bad JNI version passed to "
+                   << (as_daemon ? "AttachCurrentThreadAsDaemon" : "AttachCurrentThread") << ": "
+                   << args->version;
+        return JNI_EVERSION;
+      }
+      thread_name = args->name;
+      thread_group = args->group;
+    }
+
+    if (!runtime->AttachCurrentThread(thread_name, as_daemon, thread_group, !runtime->IsCompiler())) {
+      *p_env = nullptr;
+      return JNI_ERR;
+    } else {
+      *p_env = Thread::Current()->GetJniEnv();
+      return JNI_OK;
+    }
+  }
+};
+
+const JNIInvokeInterface gJniInvokeInterface = {
+  nullptr,  // reserved0
+  nullptr,  // reserved1
+  nullptr,  // reserved2
+  JII::DestroyJavaVM,
+  JII::AttachCurrentThread,
+  JII::DetachCurrentThread,
+  JII::GetEnv,
+  JII::AttachCurrentThreadAsDaemon
+};
+
+JavaVMExt::JavaVMExt(Runtime* runtime, ParsedOptions* options)
+    : runtime_(runtime),
+      check_jni_abort_hook_(nullptr),
+      check_jni_abort_hook_data_(nullptr),
+      check_jni_(false),  // Initialized properly in the constructor body below.
+      force_copy_(options->force_copy_),
+      tracing_enabled_(!options->jni_trace_.empty() || VLOG_IS_ON(third_party_jni)),
+      trace_(options->jni_trace_),
+      pins_lock_("JNI pin table lock", kPinTableLock),
+      pin_table_("pin table", kPinTableInitial, kPinTableMax),
+      globals_lock_("JNI global reference table lock"),
+      globals_(gGlobalsInitial, gGlobalsMax, kGlobal),
+      libraries_(new Libraries),
+      unchecked_functions_(&gJniInvokeInterface),
+      weak_globals_lock_("JNI weak global reference table lock"),
+      weak_globals_(kWeakGlobalsInitial, kWeakGlobalsMax, kWeakGlobal),
+      allow_new_weak_globals_(true),
+      weak_globals_add_condition_("weak globals add condition", weak_globals_lock_) {
+  functions = unchecked_functions_;
+  if (options->check_jni_) {
+    SetCheckJniEnabled(true);
+  }
+}
+
+JavaVMExt::~JavaVMExt() {
+}
+
+void JavaVMExt::JniAbort(const char* jni_function_name, const char* msg) {
+  Thread* self = Thread::Current();
+  ScopedObjectAccess soa(self);
+  mirror::ArtMethod* current_method = self->GetCurrentMethod(nullptr);
+
+  std::ostringstream os;
+  os << "JNI DETECTED ERROR IN APPLICATION: " << msg;
+
+  if (jni_function_name != nullptr) {
+    os << "\n    in call to " << jni_function_name;
+  }
+  // TODO: is this useful given that we're about to dump the calling thread's stack?
+  if (current_method != nullptr) {
+    os << "\n    from " << PrettyMethod(current_method);
+  }
+  os << "\n";
+  self->Dump(os);
+
+  if (check_jni_abort_hook_ != nullptr) {
+    check_jni_abort_hook_(check_jni_abort_hook_data_, os.str());
+  } else {
+    // Ensure that we get a native stack trace for this thread.
+    self->TransitionFromRunnableToSuspended(kNative);
+    LOG(FATAL) << os.str();
+    self->TransitionFromSuspendedToRunnable();  // Unreachable, keep annotalysis happy.
+  }
+}
+
+void JavaVMExt::JniAbortV(const char* jni_function_name, const char* fmt, va_list ap) {
+  std::string msg;
+  StringAppendV(&msg, fmt, ap);
+  JniAbort(jni_function_name, msg.c_str());
+}
+
+void JavaVMExt::JniAbortF(const char* jni_function_name, const char* fmt, ...) {
+  va_list args;
+  va_start(args, fmt);
+  JniAbortV(jni_function_name, fmt, args);
+  va_end(args);
+}
+
+bool JavaVMExt::ShouldTrace(mirror::ArtMethod* method) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
+  // Fast where no tracing is enabled.
+  if (trace_.empty() && !VLOG_IS_ON(third_party_jni)) {
+    return false;
+  }
+  // Perform checks based on class name.
+  StringPiece class_name(method->GetDeclaringClassDescriptor());
+  if (!trace_.empty() && class_name.find(trace_) != std::string::npos) {
+    return true;
+  }
+  if (!VLOG_IS_ON(third_party_jni)) {
+    return false;
+  }
+  // Return true if we're trying to log all third-party JNI activity and 'method' doesn't look
+  // like part of Android.
+  static const char* gBuiltInPrefixes[] = {
+      "Landroid/",
+      "Lcom/android/",
+      "Lcom/google/android/",
+      "Ldalvik/",
+      "Ljava/",
+      "Ljavax/",
+      "Llibcore/",
+      "Lorg/apache/harmony/",
+  };
+  for (size_t i = 0; i < arraysize(gBuiltInPrefixes); ++i) {
+    if (class_name.starts_with(gBuiltInPrefixes[i])) {
+      return false;
+    }
+  }
+  return true;
+}
+
+jobject JavaVMExt::AddGlobalRef(Thread* self, mirror::Object* obj) {
+  // Check for null after decoding the object to handle cleared weak globals.
+  if (obj == nullptr) {
+    return nullptr;
+  }
+  WriterMutexLock mu(self, globals_lock_);
+  IndirectRef ref = globals_.Add(IRT_FIRST_SEGMENT, obj);
+  return reinterpret_cast<jobject>(ref);
+}
+
+jweak JavaVMExt::AddWeakGlobalRef(Thread* self, mirror::Object* obj) {
+  if (obj == nullptr) {
+    return nullptr;
+  }
+  MutexLock mu(self, weak_globals_lock_);
+  while (UNLIKELY(!allow_new_weak_globals_)) {
+    weak_globals_add_condition_.WaitHoldingLocks(self);
+  }
+  IndirectRef ref = weak_globals_.Add(IRT_FIRST_SEGMENT, obj);
+  return reinterpret_cast<jweak>(ref);
+}
+
+void JavaVMExt::DeleteGlobalRef(Thread* self, jobject obj) {
+  if (obj == nullptr) {
+    return;
+  }
+  WriterMutexLock mu(self, globals_lock_);
+  if (!globals_.Remove(IRT_FIRST_SEGMENT, obj)) {
+    LOG(WARNING) << "JNI WARNING: DeleteGlobalRef(" << obj << ") "
+                 << "failed to find entry";
+  }
+}
+
+void JavaVMExt::DeleteWeakGlobalRef(Thread* self, jweak obj) {
+  if (obj == nullptr) {
+    return;
+  }
+  MutexLock mu(self, weak_globals_lock_);
+  if (!weak_globals_.Remove(IRT_FIRST_SEGMENT, obj)) {
+    LOG(WARNING) << "JNI WARNING: DeleteWeakGlobalRef(" << obj << ") "
+                 << "failed to find entry";
+  }
+}
+
+static void ThreadEnableCheckJni(Thread* thread, void* arg) {
+  bool* check_jni = reinterpret_cast<bool*>(arg);
+  thread->GetJniEnv()->SetCheckJniEnabled(*check_jni);
+}
+
+bool JavaVMExt::SetCheckJniEnabled(bool enabled) {
+  bool old_check_jni = check_jni_;
+  check_jni_ = enabled;
+  functions = enabled ? GetCheckJniInvokeInterface() : unchecked_functions_;
+  MutexLock mu(Thread::Current(), *Locks::thread_list_lock_);
+  runtime_->GetThreadList()->ForEach(ThreadEnableCheckJni, &check_jni_);
+  return old_check_jni;
+}
+
+void JavaVMExt::DumpForSigQuit(std::ostream& os) {
+  os << "JNI: CheckJNI is " << (check_jni_ ? "on" : "off");
+  if (force_copy_) {
+    os << " (with forcecopy)";
+  }
+  Thread* self = Thread::Current();
+  {
+    MutexLock mu(self, pins_lock_);
+    os << "; pins=" << pin_table_.Size();
+  }
+  {
+    ReaderMutexLock mu(self, globals_lock_);
+    os << "; globals=" << globals_.Capacity();
+  }
+  {
+    MutexLock mu(self, weak_globals_lock_);
+    if (weak_globals_.Capacity() > 0) {
+      os << " (plus " << weak_globals_.Capacity() << " weak)";
+    }
+  }
+  os << '\n';
+
+  {
+    MutexLock mu(self, *Locks::jni_libraries_lock_);
+    os << "Libraries: " << Dumpable<Libraries>(*libraries_) << " (" << libraries_->size() << ")\n";
+  }
+}
+
+void JavaVMExt::DisallowNewWeakGlobals() {
+  MutexLock mu(Thread::Current(), weak_globals_lock_);
+  allow_new_weak_globals_ = false;
+}
+
+void JavaVMExt::AllowNewWeakGlobals() {
+  Thread* self = Thread::Current();
+  MutexLock mu(self, weak_globals_lock_);
+  allow_new_weak_globals_ = true;
+  weak_globals_add_condition_.Broadcast(self);
+}
+
+mirror::Object* JavaVMExt::DecodeGlobal(Thread* self, IndirectRef ref) {
+  return globals_.SynchronizedGet(self, &globals_lock_, ref);
+}
+
+mirror::Object* JavaVMExt::DecodeWeakGlobal(Thread* self, IndirectRef ref) {
+  MutexLock mu(self, weak_globals_lock_);
+  while (UNLIKELY(!allow_new_weak_globals_)) {
+    weak_globals_add_condition_.WaitHoldingLocks(self);
+  }
+  return weak_globals_.Get(ref);
+}
+
+void JavaVMExt::PinPrimitiveArray(Thread* self, mirror::Array* array) {
+  MutexLock mu(self, pins_lock_);
+  pin_table_.Add(array);
+}
+
+void JavaVMExt::UnpinPrimitiveArray(Thread* self, mirror::Array* array) {
+  MutexLock mu(self, pins_lock_);
+  pin_table_.Remove(array);
+}
+
+void JavaVMExt::DumpReferenceTables(std::ostream& os) {
+  Thread* self = Thread::Current();
+  {
+    ReaderMutexLock mu(self, globals_lock_);
+    globals_.Dump(os);
+  }
+  {
+    MutexLock mu(self, weak_globals_lock_);
+    weak_globals_.Dump(os);
+  }
+  {
+    MutexLock mu(self, pins_lock_);
+    pin_table_.Dump(os);
+  }
+}
+
+bool JavaVMExt::LoadNativeLibrary(JNIEnv* env, const std::string& path, jobject class_loader,
+                                  std::string* error_msg) {
+  error_msg->clear();
+
+  // See if we've already loaded this library.  If we have, and the class loader
+  // matches, return successfully without doing anything.
+  // TODO: for better results we should canonicalize the pathname (or even compare
+  // inodes). This implementation is fine if everybody is using System.loadLibrary.
+  SharedLibrary* library;
+  Thread* self = Thread::Current();
+  {
+    // TODO: move the locking (and more of this logic) into Libraries.
+    MutexLock mu(self, *Locks::jni_libraries_lock_);
+    library = libraries_->Get(path);
+  }
+  if (library != nullptr) {
+    if (env->IsSameObject(library->GetClassLoader(), class_loader) == JNI_FALSE) {
+      // The library will be associated with class_loader. The JNI
+      // spec says we can't load the same library into more than one
+      // class loader.
+      StringAppendF(error_msg, "Shared library \"%s\" already opened by "
+          "ClassLoader %p; can't open in ClassLoader %p",
+          path.c_str(), library->GetClassLoader(), class_loader);
+      LOG(WARNING) << error_msg;
+      return false;
+    }
+    VLOG(jni) << "[Shared library \"" << path << "\" already loaded in "
+              << " ClassLoader " << class_loader << "]";
+    if (!library->CheckOnLoadResult()) {
+      StringAppendF(error_msg, "JNI_OnLoad failed on a previous attempt "
+          "to load \"%s\"", path.c_str());
+      return false;
+    }
+    return true;
+  }
+
+  // Open the shared library.  Because we're using a full path, the system
+  // doesn't have to search through LD_LIBRARY_PATH.  (It may do so to
+  // resolve this library's dependencies though.)
+
+  // Failures here are expected when java.library.path has several entries
+  // and we have to hunt for the lib.
+
+  // Below we dlopen but there is no paired dlclose, this would be necessary if we supported
+  // class unloading. Libraries will only be unloaded when the reference count (incremented by
+  // dlopen) becomes zero from dlclose.
+
+  Locks::mutator_lock_->AssertNotHeld(self);
+  const char* path_str = path.empty() ? nullptr : path.c_str();
+  void* handle = dlopen(path_str, RTLD_LAZY);
+  bool needs_native_bridge = false;
+  if (handle == nullptr) {
+    if (NativeBridgeIsSupported(path_str)) {
+      handle = NativeBridgeLoadLibrary(path_str, RTLD_LAZY);
+      needs_native_bridge = true;
+    }
+  }
+
+  VLOG(jni) << "[Call to dlopen(\"" << path << "\", RTLD_LAZY) returned " << handle << "]";
+
+  if (handle == nullptr) {
+    *error_msg = dlerror();
+    LOG(ERROR) << "dlopen(\"" << path << "\", RTLD_LAZY) failed: " << *error_msg;
+    return false;
+  }
+
+  if (env->ExceptionCheck() == JNI_TRUE) {
+    LOG(ERROR) << "Unexpected exception:";
+    env->ExceptionDescribe();
+    env->ExceptionClear();
+  }
+  // Create a new entry.
+  // TODO: move the locking (and more of this logic) into Libraries.
+  bool created_library = false;
+  {
+    // Create SharedLibrary ahead of taking the libraries lock to maintain lock ordering.
+    std::unique_ptr<SharedLibrary> new_library(
+        new SharedLibrary(env, self, path, handle, class_loader));
+    MutexLock mu(self, *Locks::jni_libraries_lock_);
+    library = libraries_->Get(path);
+    if (library == nullptr) {  // We won race to get libraries_lock.
+      library = new_library.release();
+      libraries_->Put(path, library);
+      created_library = true;
+    }
+  }
+  if (!created_library) {
+    LOG(INFO) << "WOW: we lost a race to add shared library: "
+        << "\"" << path << "\" ClassLoader=" << class_loader;
+    return library->CheckOnLoadResult();
+  }
+  VLOG(jni) << "[Added shared library \"" << path << "\" for ClassLoader " << class_loader << "]";
+
+  bool was_successful = false;
+  void* sym;
+  if (needs_native_bridge) {
+    library->SetNeedsNativeBridge();
+    sym = library->FindSymbolWithNativeBridge("JNI_OnLoad", nullptr);
+  } else {
+    sym = dlsym(handle, "JNI_OnLoad");
+  }
+  if (sym == nullptr) {
+    VLOG(jni) << "[No JNI_OnLoad found in \"" << path << "\"]";
+    was_successful = true;
+  } else {
+    // Call JNI_OnLoad.  We have to override the current class
+    // loader, which will always be "null" since the stuff at the
+    // top of the stack is around Runtime.loadLibrary().  (See
+    // the comments in the JNI FindClass function.)
+    ScopedLocalRef<jobject> old_class_loader(env, env->NewLocalRef(self->GetClassLoaderOverride()));
+    self->SetClassLoaderOverride(class_loader);
+
+    VLOG(jni) << "[Calling JNI_OnLoad in \"" << path << "\"]";
+    typedef int (*JNI_OnLoadFn)(JavaVM*, void*);
+    JNI_OnLoadFn jni_on_load = reinterpret_cast<JNI_OnLoadFn>(sym);
+    int version = (*jni_on_load)(this, nullptr);
+
+    self->SetClassLoaderOverride(old_class_loader.get());
+
+    if (version == JNI_ERR) {
+      StringAppendF(error_msg, "JNI_ERR returned from JNI_OnLoad in \"%s\"", path.c_str());
+    } else if (IsBadJniVersion(version)) {
+      StringAppendF(error_msg, "Bad JNI version returned from JNI_OnLoad in \"%s\": %d",
+                    path.c_str(), version);
+      // It's unwise to call dlclose() here, but we can mark it
+      // as bad and ensure that future load attempts will fail.
+      // We don't know how far JNI_OnLoad got, so there could
+      // be some partially-initialized stuff accessible through
+      // newly-registered native method calls.  We could try to
+      // unregister them, but that doesn't seem worthwhile.
+    } else {
+      was_successful = true;
+    }
+    VLOG(jni) << "[Returned " << (was_successful ? "successfully" : "failure")
+              << " from JNI_OnLoad in \"" << path << "\"]";
+  }
+
+  library->SetResult(was_successful);
+  return was_successful;
+}
+
+void* JavaVMExt::FindCodeForNativeMethod(mirror::ArtMethod* m) {
+  CHECK(m->IsNative());
+  mirror::Class* c = m->GetDeclaringClass();
+  // If this is a static method, it could be called before the class has been initialized.
+  CHECK(c->IsInitializing()) << c->GetStatus() << " " << PrettyMethod(m);
+  std::string detail;
+  void* native_method;
+  Thread* self = Thread::Current();
+  {
+    MutexLock mu(self, *Locks::jni_libraries_lock_);
+    native_method = libraries_->FindNativeMethod(m, detail);
+  }
+  // Throwing can cause libraries_lock to be reacquired.
+  if (native_method == nullptr) {
+    ThrowLocation throw_location = self->GetCurrentLocationForThrow();
+    self->ThrowNewException(throw_location, "Ljava/lang/UnsatisfiedLinkError;", detail.c_str());
+  }
+  return native_method;
+}
+
+void JavaVMExt::SweepJniWeakGlobals(IsMarkedCallback* callback, void* arg) {
+  MutexLock mu(Thread::Current(), weak_globals_lock_);
+  for (mirror::Object** entry : weak_globals_) {
+    // Since this is called by the GC, we don't need a read barrier.
+    mirror::Object* obj = *entry;
+    mirror::Object* new_obj = callback(obj, arg);
+    if (new_obj == nullptr) {
+      new_obj = kClearedJniWeakGlobal;
+    }
+    *entry = new_obj;
+  }
+}
+
+void JavaVMExt::VisitRoots(RootCallback* callback, void* arg) {
+  Thread* self = Thread::Current();
+  {
+    ReaderMutexLock mu(self, globals_lock_);
+    globals_.VisitRoots(callback, arg, 0, kRootJNIGlobal);
+  }
+  {
+    MutexLock mu(self, pins_lock_);
+    pin_table_.VisitRoots(callback, arg, 0, kRootVMInternal);
+  }
+  // The weak_globals table is visited by the GC itself (because it mutates the table).
+}
+
+// JNI Invocation interface.
+
+extern "C" jint JNI_CreateJavaVM(JavaVM** p_vm, JNIEnv** p_env, void* vm_args) {
+  const JavaVMInitArgs* args = static_cast<JavaVMInitArgs*>(vm_args);
+  if (IsBadJniVersion(args->version)) {
+    LOG(ERROR) << "Bad JNI version passed to CreateJavaVM: " << args->version;
+    return JNI_EVERSION;
+  }
+  RuntimeOptions options;
+  for (int i = 0; i < args->nOptions; ++i) {
+    JavaVMOption* option = &args->options[i];
+    options.push_back(std::make_pair(std::string(option->optionString), option->extraInfo));
+  }
+  bool ignore_unrecognized = args->ignoreUnrecognized;
+  if (!Runtime::Create(options, ignore_unrecognized)) {
+    return JNI_ERR;
+  }
+  Runtime* runtime = Runtime::Current();
+  bool started = runtime->Start();
+  if (!started) {
+    delete Thread::Current()->GetJniEnv();
+    delete runtime->GetJavaVM();
+    LOG(WARNING) << "CreateJavaVM failed";
+    return JNI_ERR;
+  }
+  *p_env = Thread::Current()->GetJniEnv();
+  *p_vm = runtime->GetJavaVM();
+  return JNI_OK;
+}
+
+extern "C" jint JNI_GetCreatedJavaVMs(JavaVM** vms, jsize, jsize* vm_count) {
+  Runtime* runtime = Runtime::Current();
+  if (runtime == nullptr) {
+    *vm_count = 0;
+  } else {
+    *vm_count = 1;
+    vms[0] = runtime->GetJavaVM();
+  }
+  return JNI_OK;
+}
+
+// Historically unsupported.
+extern "C" jint JNI_GetDefaultJavaVMInitArgs(void* /*vm_args*/) {
+  return JNI_ERR;
+}
+
+}  // namespace art