runtime/native_bridge.cc - platform/art - Git at Google

 /*
  * Copyright (C) 2014 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 "native_bridge.h"

 #include <dlfcn.h>
 #include <stdio.h>
 #include "jni.h"

 #include "base/mutex.h"
 #include "mirror/art_method-inl.h"
 #include "mirror/class-inl.h"
 #include "scoped_thread_state_change.h"
 #include "ScopedLocalRef.h"
 #include "thread.h"

 #ifdef HAVE_ANDROID_OS
 #include "cutils/properties.h"
 #endif


 namespace art {

 // Is native-bridge support enabled?
 static constexpr bool kNativeBridgeEnabled = true;

 // Default library name for native-bridge.
 static constexpr const char* kDefaultNativeBridge = "libnativebridge.so";

 #ifdef HAVE_ANDROID_OS
 // TODO: This will be removed once we have native-bridge command-line arguments.

 // Property that defines the library name of native-bridge.
 static constexpr const char* kPropNativeBridge = "persist.native.bridge";

 // Property that enables native-bridge.
 static constexpr const char* kPropEnableNativeBridge = "persist.enable.native.bridge";
 #endif

 // The symbol name exposed by native-bridge with the type of NativeBridgeCallbacks.
 static constexpr const char* kNativeBridgeInterfaceSymbol = "NativeBridgeItf";

 // ART interfaces to native-bridge.
 struct NativeBridgeArtCallbacks {
   // Get shorty of a Java method. The shorty is supposed to be persistent in memory.
   //
   // Parameters:
   //   env [IN] pointer to JNIenv.
   //   mid [IN] Java methodID.
   // Returns:
   //   short descriptor for method.
   const char* (*getMethodShorty)(JNIEnv* env, jmethodID mid);

   // Get number of native methods for specified class.
   //
   // Parameters:
   //   env [IN] pointer to JNIenv.
   //   clazz [IN] Java class object.
   // Returns:
   //   number of native methods.
   int (*getNativeMethodCount)(JNIEnv* env, jclass clazz);

   // Get at most 'method_count' native methods for specified class 'clazz'. Results are outputed
   // via 'methods' [OUT]. The signature pointer in JNINativeMethod is reused as the method shorty.
   //
   // Parameters:
   //   env [IN] pointer to JNIenv.
   //   clazz [IN] Java class object.
   //   methods [OUT] array of method with the name, shorty, and fnPtr.
   //   method_count [IN] max number of elements in methods.
   // Returns:
   //   number of method it actually wrote to methods.
   int (*getNativeMethods)(JNIEnv* env, jclass clazz, JNINativeMethod* methods, uint32_t method_count);
 };

 // Native-bridge interfaces to ART
 struct NativeBridgeCallbacks {
   // Initialize native-bridge. Native-bridge's internal implementation must ensure MT safety and
   // that the native-bridge is initialized only once. Thus it is OK to call this interface for an
   // already initialized native-bridge.
   //
   // Parameters:
   //   art_cbs [IN] the pointer to NativeBridgeArtCallbacks.
   // Returns:
   //   true iff initialization was successful.
   bool (*initialize)(NativeBridgeArtCallbacks* art_cbs);

   // Load a shared library that is supported by the native-bridge.
   //
   // Parameters:
   //   libpath [IN] path to the shared library
   //   flag [IN] the stardard RTLD_XXX defined in bionic dlfcn.h
   // Returns:
   //   The opaque handle of the shared library if sucessful, otherwise NULL
   void* (*loadLibrary)(const char* libpath, int flag);

   // Get a native-bridge trampoline for specified native method. The trampoline has same
   // sigature as the native method.
   //
   // Parameters:
   //   handle [IN] the handle returned from loadLibrary
   //   shorty [IN] short descriptor of native method
   //   len [IN] length of shorty
   // Returns:
   //   address of trampoline if successful, otherwise NULL
   void* (*getTrampoline)(void* handle, const char* name, const char* shorty, uint32_t len);

   // Check whether native library is valid and is for an ABI that is supported by native-bridge.
   //
   // Parameters:
   //   libpath [IN] path to the shared library
   // Returns:
   //   TRUE if library is supported by native-bridge, FALSE otherwise
   bool (*isSupported)(const char* libpath);
 };

 static const char* GetMethodShorty(JNIEnv* env, jmethodID mid) {
   ScopedObjectAccess soa(env);
   StackHandleScope<1> scope(soa.Self());
   mirror::ArtMethod* m = soa.DecodeMethod(mid);
   MethodHelper mh(scope.NewHandle(m));
   return mh.GetShorty();
 }

 static int GetNativeMethodCount(JNIEnv* env, jclass clazz) {
   if (clazz == nullptr)
     return 0;

   ScopedObjectAccess soa(env);
   mirror::Class* c = soa.Decode<mirror::Class*>(clazz);

   size_t method_count = 0;
   for (size_t i = 0; i < c->NumDirectMethods(); ++i) {
     mirror::ArtMethod* m = c->GetDirectMethod(i);
     if (m->IsNative())
       method_count++;
   }
   for (size_t i = 0; i < c->NumVirtualMethods(); ++i) {
     mirror::ArtMethod* m = c->GetVirtualMethod(i);
     if (m->IsNative())
       method_count++;
   }
   return method_count;
 }

 static int GetNativeMethods(JNIEnv* env, jclass clazz, JNINativeMethod* methods,
                             uint32_t method_count) {
   if ((clazz == nullptr) || (methods == nullptr))
     return 0;

   ScopedObjectAccess soa(env);
   mirror::Class* c = soa.Decode<mirror::Class*>(clazz);

   size_t count = 0;
   for (size_t i = 0; i < c->NumDirectMethods(); ++i) {
     mirror::ArtMethod* m = c->GetDirectMethod(i);
     if (m->IsNative() && count < method_count) {
       methods[count].name = m->GetName();
       methods[count].signature = m->GetShorty();
       methods[count].fnPtr = const_cast<void*>(m->GetNativeMethod());
       count++;
     }
   }
   for (size_t i = 0; i < c->NumVirtualMethods(); ++i) {
     mirror::ArtMethod* m = c->GetVirtualMethod(i);
     if (m->IsNative() && count < method_count) {
       methods[count].name = m->GetName();
       methods[count].signature = m->GetShorty();
       methods[count].fnPtr = const_cast<void*>(m->GetNativeMethod());
       count++;
     }
   }
   return count;
 }

 NativeBridgeArtCallbacks NativeBridgeArtItf = {
   GetMethodShorty,
   GetNativeMethodCount,
   GetNativeMethods
 };

 void NativeBridge::SetNativeBridgeLibraryString(std::string& native_bridge_library_string) {
   native_bridge_library_string_ = native_bridge_library_string;
   // TODO: when given an empty string, set initialized_ to true and available_ to false. This
   //       change is dependent on the property removal in Initialize().
 }

 bool NativeBridge::Initialize() {
   if (!kNativeBridgeEnabled) {
     return false;
   }

   MutexLock mu(Thread::Current(), lock_);

   if (initialized_) {
     // Somebody did it before.
     return available_;
   }

   available_ = false;

   const char* libnb_path;

   if (!native_bridge_library_string_.empty()) {
     libnb_path = native_bridge_library_string_.c_str();
   } else {
     // TODO: Remove this once the frameworks side is completely implemented.

     libnb_path = kDefaultNativeBridge;
 #ifdef HAVE_ANDROID_OS
     char prop_buf[PROP_VALUE_MAX];
     property_get(kPropEnableNativeBridge, prop_buf, "false");
     if (strcmp(prop_buf, "true") != 0) {
       initialized_ = true;
       return false;
     }

     // If prop persist.native.bridge set, overwrite the default name.
     int name_len = property_get(kPropNativeBridge, prop_buf, kDefaultNativeBridge);
     if (name_len > 0)
       libnb_path = prop_buf;
 #endif
   }

   void* handle = dlopen(libnb_path, RTLD_LAZY);
   if (handle != nullptr) {
     callbacks_ = reinterpret_cast<NativeBridgeCallbacks*>(dlsym(handle,
                                                                 kNativeBridgeInterfaceSymbol));

     if (callbacks_ != nullptr) {
       available_ = callbacks_->initialize(&NativeBridgeArtItf);
     }

     if (!available_) {
       dlclose(handle);
     }
   }

   initialized_ = true;

   return available_;
 }

 void* NativeBridge::LoadLibrary(const char* libpath, int flag) {
   if (Initialize())
     return callbacks_->loadLibrary(libpath, flag);
   return nullptr;
 }

 void* NativeBridge::GetTrampoline(void* handle, const char* name, const char* shorty,
                                   uint32_t len) {
   if (Initialize())
     return callbacks_->getTrampoline(handle, name, shorty, len);
   return nullptr;
 }

 bool NativeBridge::IsSupported(const char* libpath) {
   if (Initialize())
     return callbacks_->isSupported(libpath);
   return false;
 }

 bool NativeBridge::available_ = false;
 bool NativeBridge::initialized_ = false;
 Mutex NativeBridge::lock_("native bridge lock");
 std::string NativeBridge::native_bridge_library_string_ = "";
 NativeBridgeCallbacks* NativeBridge::callbacks_ = nullptr;

 };  // namespace art
	/*
	* Copyright (C) 2014 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 "native_bridge.h"

	#include <dlfcn.h>
	#include <stdio.h>
	#include "jni.h"

	#include "base/mutex.h"
	#include "mirror/art_method-inl.h"
	#include "mirror/class-inl.h"
	#include "scoped_thread_state_change.h"
	#include "ScopedLocalRef.h"
	#include "thread.h"

	#ifdef HAVE_ANDROID_OS
	#include "cutils/properties.h"
	#endif


	namespace art {

	// Is native-bridge support enabled?
	static constexpr bool kNativeBridgeEnabled = true;

	// Default library name for native-bridge.
	static constexpr const char* kDefaultNativeBridge = "libnativebridge.so";

	#ifdef HAVE_ANDROID_OS
	// TODO: This will be removed once we have native-bridge command-line arguments.

	// Property that defines the library name of native-bridge.
	static constexpr const char* kPropNativeBridge = "persist.native.bridge";

	// Property that enables native-bridge.
	static constexpr const char* kPropEnableNativeBridge = "persist.enable.native.bridge";
	#endif

	// The symbol name exposed by native-bridge with the type of NativeBridgeCallbacks.
	static constexpr const char* kNativeBridgeInterfaceSymbol = "NativeBridgeItf";

	// ART interfaces to native-bridge.
	struct NativeBridgeArtCallbacks {
	// Get shorty of a Java method. The shorty is supposed to be persistent in memory.
	//
	// Parameters:
	// env [IN] pointer to JNIenv.
	// mid [IN] Java methodID.
	// Returns:
	// short descriptor for method.
	const char* (getMethodShorty)(JNIEnv env, jmethodID mid);

	// Get number of native methods for specified class.
	//
	// Parameters:
	// env [IN] pointer to JNIenv.
	// clazz [IN] Java class object.
	// Returns:
	// number of native methods.
	int (getNativeMethodCount)(JNIEnv env, jclass clazz);

	// Get at most 'method_count' native methods for specified class 'clazz'. Results are outputed
	// via 'methods' [OUT]. The signature pointer in JNINativeMethod is reused as the method shorty.
	//
	// Parameters:
	// env [IN] pointer to JNIenv.
	// clazz [IN] Java class object.
	// methods [OUT] array of method with the name, shorty, and fnPtr.
	// method_count [IN] max number of elements in methods.
	// Returns:
	// number of method it actually wrote to methods.
	int (getNativeMethods)(JNIEnv env, jclass clazz, JNINativeMethod* methods, uint32_t method_count);
	};

	// Native-bridge interfaces to ART
	struct NativeBridgeCallbacks {
	// Initialize native-bridge. Native-bridge's internal implementation must ensure MT safety and
	// that the native-bridge is initialized only once. Thus it is OK to call this interface for an
	// already initialized native-bridge.
	//
	// Parameters:
	// art_cbs [IN] the pointer to NativeBridgeArtCallbacks.
	// Returns:
	// true iff initialization was successful.
	bool (initialize)(NativeBridgeArtCallbacks art_cbs);

	// Load a shared library that is supported by the native-bridge.
	//
	// Parameters:
	// libpath [IN] path to the shared library
	// flag [IN] the stardard RTLD_XXX defined in bionic dlfcn.h
	// Returns:
	// The opaque handle of the shared library if sucessful, otherwise NULL
	void* (loadLibrary)(const char libpath, int flag);

	// Get a native-bridge trampoline for specified native method. The trampoline has same
	// sigature as the native method.
	//
	// Parameters:
	// handle [IN] the handle returned from loadLibrary
	// shorty [IN] short descriptor of native method
	// len [IN] length of shorty
	// Returns:
	// address of trampoline if successful, otherwise NULL
	void* (getTrampoline)(void handle, const char* name, const char* shorty, uint32_t len);

	// Check whether native library is valid and is for an ABI that is supported by native-bridge.
	//
	// Parameters:
	// libpath [IN] path to the shared library
	// Returns:
	// TRUE if library is supported by native-bridge, FALSE otherwise
	bool (isSupported)(const char libpath);
	};

	static const char* GetMethodShorty(JNIEnv* env, jmethodID mid) {
	ScopedObjectAccess soa(env);
	StackHandleScope<1> scope(soa.Self());
	mirror::ArtMethod* m = soa.DecodeMethod(mid);
	MethodHelper mh(scope.NewHandle(m));
	return mh.GetShorty();
	}

	static int GetNativeMethodCount(JNIEnv* env, jclass clazz) {
	if (clazz == nullptr)
	return 0;

	ScopedObjectAccess soa(env);
	mirror::Class* c = soa.Decode<mirror::Class*>(clazz);

	size_t method_count = 0;
	for (size_t i = 0; i < c->NumDirectMethods(); ++i) {
	mirror::ArtMethod* m = c->GetDirectMethod(i);
	if (m->IsNative())
	method_count++;
	}
	for (size_t i = 0; i < c->NumVirtualMethods(); ++i) {
	mirror::ArtMethod* m = c->GetVirtualMethod(i);
	if (m->IsNative())
	method_count++;
	}
	return method_count;
	}

	static int GetNativeMethods(JNIEnv* env, jclass clazz, JNINativeMethod* methods,
	uint32_t method_count) {
	if ((clazz == nullptr) \|\| (methods == nullptr))
	return 0;

	ScopedObjectAccess soa(env);
	mirror::Class* c = soa.Decode<mirror::Class*>(clazz);

	size_t count = 0;
	for (size_t i = 0; i < c->NumDirectMethods(); ++i) {
	mirror::ArtMethod* m = c->GetDirectMethod(i);
	if (m->IsNative() && count < method_count) {
	methods[count].name = m->GetName();
	methods[count].signature = m->GetShorty();
	methods[count].fnPtr = const_cast<void*>(m->GetNativeMethod());
	count++;
	}
	}
	for (size_t i = 0; i < c->NumVirtualMethods(); ++i) {
	mirror::ArtMethod* m = c->GetVirtualMethod(i);
	if (m->IsNative() && count < method_count) {
	methods[count].name = m->GetName();
	methods[count].signature = m->GetShorty();
	methods[count].fnPtr = const_cast<void*>(m->GetNativeMethod());
	count++;
	}
	}
	return count;
	}

	NativeBridgeArtCallbacks NativeBridgeArtItf = {
	GetMethodShorty,
	GetNativeMethodCount,
	GetNativeMethods
	};

	void NativeBridge::SetNativeBridgeLibraryString(std::string& native_bridge_library_string) {
	native_bridge_library_string_ = native_bridge_library_string;
	// TODO: when given an empty string, set initialized_ to true and available_ to false. This
	// change is dependent on the property removal in Initialize().
	}

	bool NativeBridge::Initialize() {
	if (!kNativeBridgeEnabled) {
	return false;
	}

	MutexLock mu(Thread::Current(), lock_);

	if (initialized_) {
	// Somebody did it before.
	return available_;
	}

	available_ = false;

	const char* libnb_path;

	if (!native_bridge_library_string_.empty()) {
	libnb_path = native_bridge_library_string_.c_str();
	} else {
	// TODO: Remove this once the frameworks side is completely implemented.

	libnb_path = kDefaultNativeBridge;
	#ifdef HAVE_ANDROID_OS
	char prop_buf[PROP_VALUE_MAX];
	property_get(kPropEnableNativeBridge, prop_buf, "false");
	if (strcmp(prop_buf, "true") != 0) {
	initialized_ = true;
	return false;
	}

	// If prop persist.native.bridge set, overwrite the default name.
	int name_len = property_get(kPropNativeBridge, prop_buf, kDefaultNativeBridge);
	if (name_len > 0)
	libnb_path = prop_buf;
	#endif
	}

	void* handle = dlopen(libnb_path, RTLD_LAZY);
	if (handle != nullptr) {
	callbacks_ = reinterpret_cast<NativeBridgeCallbacks*>(dlsym(handle,
	kNativeBridgeInterfaceSymbol));

	if (callbacks_ != nullptr) {
	available_ = callbacks_->initialize(&NativeBridgeArtItf);
	}

	if (!available_) {
	dlclose(handle);
	}
	}

	initialized_ = true;

	return available_;
	}

	void* NativeBridge::LoadLibrary(const char* libpath, int flag) {
	if (Initialize())
	return callbacks_->loadLibrary(libpath, flag);
	return nullptr;
	}

	void* NativeBridge::GetTrampoline(void* handle, const char* name, const char* shorty,
	uint32_t len) {
	if (Initialize())
	return callbacks_->getTrampoline(handle, name, shorty, len);
	return nullptr;
	}

	bool NativeBridge::IsSupported(const char* libpath) {
	if (Initialize())
	return callbacks_->isSupported(libpath);
	return false;
	}

	bool NativeBridge::available_ = false;
	bool NativeBridge::initialized_ = false;
	Mutex NativeBridge::lock_("native bridge lock");
	std::string NativeBridge::native_bridge_library_string_ = "";
	NativeBridgeCallbacks* NativeBridge::callbacks_ = nullptr;

	}; // namespace art