libnativeloader/library_namespaces.cpp - LeafOS-Project/android_art - Gitiles

 /*
  * Copyright (C) 2019 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.
  */

 #if defined(ART_TARGET_ANDROID)

 #include "library_namespaces.h"

 #include <dirent.h>
 #include <dlfcn.h>

 #include <regex>
 #include <string>
 #include <vector>

 #include <android-base/file.h>
 #include <android-base/logging.h>
 #include <android-base/macros.h>
 #include <android-base/result.h>
 #include <android-base/strings.h>
 #include <nativehelper/scoped_utf_chars.h>

 #include "nativeloader/dlext_namespaces.h"
 #include "public_libraries.h"
 #include "utils.h"

 namespace android::nativeloader {

 namespace {

 constexpr const char* kApexPath = "/apex/";

 // The device may be configured to have the vendor libraries loaded to a separate namespace.
 // For historical reasons this namespace was named sphal but effectively it is intended
 // to use to load vendor libraries to separate namespace with controlled interface between
 // vendor and system namespaces.
 constexpr const char* kVendorNamespaceName = "sphal";
 // Similar to sphal namespace, product namespace provides some product libraries.
 constexpr const char* kProductNamespaceName = "product";

 // vndk namespace for unbundled vendor apps
 constexpr const char* kVndkNamespaceName = "vndk";
 // vndk_product namespace for unbundled product apps
 constexpr const char* kVndkProductNamespaceName = "vndk_product";

 // classloader-namespace is a linker namespace that is created for the loaded
 // app. To be specific, it is created for the app classloader. When
 // System.load() is called from a Java class that is loaded from the
 // classloader, the classloader-namespace namespace associated with that
 // classloader is selected for dlopen. The namespace is configured so that its
 // search path is set to the app-local JNI directory and it is linked to the
 // system namespace with the names of libs listed in the public.libraries.txt.
 // This way an app can only load its own JNI libraries along with the public libs.
 constexpr const char* kClassloaderNamespaceName = "classloader-namespace";
 // Same thing for vendor APKs.
 constexpr const char* kVendorClassloaderNamespaceName = "vendor-classloader-namespace";
 // If the namespace is shared then add this suffix to form
 // "classloader-namespace-shared" or "vendor-classloader-namespace-shared",
 // respectively. A shared namespace (cf. ANDROID_NAMESPACE_TYPE_SHARED) has
 // inherited all the libraries of the parent classloader namespace, or the
 // system namespace for the main app classloader. It is used to give full
 // access to the platform libraries for apps bundled in the system image,
 // including their later updates installed in /data.
 constexpr const char* kSharedNamespaceSuffix = "-shared";

 // (http://b/27588281) This is a workaround for apps using custom classloaders and calling
 // System.load() with an absolute path which is outside of the classloader library search path.
 // This list includes all directories app is allowed to access this way.
 constexpr const char* kWhitelistedDirectories = "/data:/mnt/expand";

 constexpr const char* kVendorLibPath = "/vendor/" LIB;
 constexpr const char* kProductLibPath = "/product/" LIB ":/system/product/" LIB;

 const std::regex kVendorDexPathRegex("(^|:)/vendor/");
 const std::regex kProductDexPathRegex("(^|:)(/system)?/product/");

 // Define origin of APK if it is from vendor partition or product partition
 using ApkOrigin = enum {
   APK_ORIGIN_DEFAULT = 0,
   APK_ORIGIN_VENDOR = 1,
   APK_ORIGIN_PRODUCT = 2,
 };

 jobject GetParentClassLoader(JNIEnv* env, jobject class_loader) {
   jclass class_loader_class = env->FindClass("java/lang/ClassLoader");
   jmethodID get_parent =
       env->GetMethodID(class_loader_class, "getParent", "()Ljava/lang/ClassLoader;");

   return env->CallObjectMethod(class_loader, get_parent);
 }

 ApkOrigin GetApkOriginFromDexPath(const std::string& dex_path) {
   ApkOrigin apk_origin = APK_ORIGIN_DEFAULT;
   if (std::regex_search(dex_path, kVendorDexPathRegex)) {
     apk_origin = APK_ORIGIN_VENDOR;
   }
   if (std::regex_search(dex_path, kProductDexPathRegex)) {
     LOG_ALWAYS_FATAL_IF(apk_origin == APK_ORIGIN_VENDOR,
                         "Dex path contains both vendor and product partition : %s",
                         dex_path.c_str());

     apk_origin = APK_ORIGIN_PRODUCT;
   }
   return apk_origin;
 }

 }  // namespace

 void LibraryNamespaces::Initialize() {
   // Once public namespace is initialized there is no
   // point in running this code - it will have no effect
   // on the current list of public libraries.
   if (initialized_) {
     return;
   }

   // Load the preloadable public libraries. Since libnativeloader is in the
   // com_android_art namespace, use OpenSystemLibrary rather than dlopen to
   // ensure the libraries are loaded in the system namespace.
   //
   // TODO(dimitry): this is a bit misleading since we do not know
   // if the vendor public library is going to be opened from /vendor/lib
   // we might as well end up loading them from /system/lib or /product/lib
   // For now we rely on CTS test to catch things like this but
   // it should probably be addressed in the future.
   for (const std::string& soname : android::base::Split(preloadable_public_libraries(), ":")) {
     void* handle = OpenSystemLibrary(soname.c_str(), RTLD_NOW | RTLD_NODELETE);
     LOG_ALWAYS_FATAL_IF(handle == nullptr,
                         "Error preloading public library %s: %s", soname.c_str(), dlerror());
   }
 }

 // "ALL" is a magic name that allows all public libraries even when the
 // target SDK is > 30. Currently this is used for (Java) shared libraries
 // which don't use <uses-native-library>
 // TODO(b/142191088) remove this hack
 static constexpr const char LIBRARY_ALL[] = "ALL";

 // Returns the colon-separated list of library names by filtering uses_libraries from
 // public_libraries. The returned names will actually be available to the app. If the app is pre-S
 // (<= 30), the filtering is not done; the entire public_libraries are provided.
 static const std::string filter_public_libraries(
     uint32_t target_sdk_version, const std::vector<std::string>& uses_libraries,
     const std::string& public_libraries) {
   // Apps targeting Android 11 or earlier gets all public libraries
   if (target_sdk_version <= 30) {
     return public_libraries;
   }
   if (std::find(uses_libraries.begin(), uses_libraries.end(), LIBRARY_ALL) !=
       uses_libraries.end()) {
     return public_libraries;
   }
   std::vector<std::string> filtered;
   std::vector<std::string> orig = android::base::Split(public_libraries, ":");
   for (const auto& lib : uses_libraries) {
     if (std::find(orig.begin(), orig.end(), lib) != orig.end()) {
       filtered.emplace_back(lib);
     }
   }
   return android::base::Join(filtered, ":");
 }

 Result<NativeLoaderNamespace*> LibraryNamespaces::Create(JNIEnv* env, uint32_t target_sdk_version,
                                                          jobject class_loader, bool is_shared,
                                                          jstring dex_path_j,
                                                          jstring java_library_path,
                                                          jstring java_permitted_path,
                                                          jstring uses_library_list) {
   std::string library_path;  // empty string by default.
   std::string dex_path;

   if (java_library_path != nullptr) {
     ScopedUtfChars library_path_utf_chars(env, java_library_path);
     library_path = library_path_utf_chars.c_str();
   }

   if (dex_path_j != nullptr) {
     ScopedUtfChars dex_path_chars(env, dex_path_j);
     dex_path = dex_path_chars.c_str();
   }

   std::vector<std::string> uses_libraries;
   if (uses_library_list != nullptr) {
     ScopedUtfChars names(env, uses_library_list);
     uses_libraries = android::base::Split(names.c_str(), ":");
   } else {
     // uses_library_list could be nullptr when System.loadLibrary is called from a
     // custom classloader. In that case, we don't know the list of public
     // libraries because we don't know which apk the classloader is for. Only
     // choices we can have are 1) allowing all public libs (as before), or 2)
     // not allowing all but NDK libs. Here we take #1 because #2 would surprise
     // developers unnecessarily.
     // TODO(b/142191088) finalize the policy here. We could either 1) allow all
     // public libs, 2) disallow any lib, or 3) use the libs that were granted to
     // the first (i.e. app main) classloader.
     uses_libraries.emplace_back(LIBRARY_ALL);
   }

   ApkOrigin apk_origin = GetApkOriginFromDexPath(dex_path);

   // (http://b/27588281) This is a workaround for apps using custom
   // classloaders and calling System.load() with an absolute path which
   // is outside of the classloader library search path.
   //
   // This part effectively allows such a classloader to access anything
   // under /data and /mnt/expand
   std::string permitted_path = kWhitelistedDirectories;

   if (java_permitted_path != nullptr) {
     ScopedUtfChars path(env, java_permitted_path);
     if (path.c_str() != nullptr && path.size() > 0) {
       permitted_path = permitted_path + ":" + path.c_str();
     }
   }

   LOG_ALWAYS_FATAL_IF(FindNamespaceByClassLoader(env, class_loader) != nullptr,
                       "There is already a namespace associated with this classloader");

   std::string system_exposed_libraries = default_public_libraries();
   std::string namespace_name = kClassloaderNamespaceName;
   ApkOrigin unbundled_app_origin = APK_ORIGIN_DEFAULT;
   if ((apk_origin == APK_ORIGIN_VENDOR ||
        (apk_origin == APK_ORIGIN_PRODUCT &&
         is_product_vndk_version_defined())) &&
       !is_shared) {
     unbundled_app_origin = apk_origin;
     // For vendor / product apks, give access to the vendor / product lib even though
     // they are treated as unbundled; the libs and apks are still bundled
     // together in the vendor / product partition.
     const char* origin_partition;
     const char* origin_lib_path;
     const char* llndk_libraries;

     switch (apk_origin) {
       case APK_ORIGIN_VENDOR:
         origin_partition = "vendor";
         origin_lib_path = kVendorLibPath;
         llndk_libraries = llndk_libraries_vendor().c_str();
         break;
       case APK_ORIGIN_PRODUCT:
         origin_partition = "product";
         origin_lib_path = kProductLibPath;
         llndk_libraries = llndk_libraries_product().c_str();
         break;
       default:
         origin_partition = "unknown";
         origin_lib_path = "";
         llndk_libraries = "";
     }
     library_path = library_path + ":" + origin_lib_path;
     permitted_path = permitted_path + ":" + origin_lib_path;

     // Also give access to LLNDK libraries since they are available to vendor or product
     system_exposed_libraries = system_exposed_libraries + ":" + llndk_libraries;

     // Different name is useful for debugging
     namespace_name = kVendorClassloaderNamespaceName;
     ALOGD("classloader namespace configured for unbundled %s apk. library_path=%s",
           origin_partition, library_path.c_str());
   } else {
     auto libs = filter_public_libraries(target_sdk_version, uses_libraries,
                                         extended_public_libraries());
     // extended public libraries are NOT available to vendor apks, otherwise it
     // would be system->vendor violation.
     if (!libs.empty()) {
       system_exposed_libraries = system_exposed_libraries + ':' + libs;
     }
   }

   if (is_shared) {
     // Show in the name that the namespace was created as shared, for debugging
     // purposes.
     namespace_name = namespace_name + kSharedNamespaceSuffix;
   }

   // Create the app namespace
   NativeLoaderNamespace* parent_ns = FindParentNamespaceByClassLoader(env, class_loader);
   // Heuristic: the first classloader with non-empty library_path is assumed to
   // be the main classloader for app
   // TODO(b/139178525) remove this heuristic by determining this in LoadedApk (or its
   // friends) and then passing it down to here.
   bool is_main_classloader = app_main_namespace_ == nullptr && !library_path.empty();
   // Policy: the namespace for the main classloader is also used as the
   // anonymous namespace.
   bool also_used_as_anonymous = is_main_classloader;
   // Note: this function is executed with g_namespaces_mutex held, thus no
   // racing here.
   auto app_ns = NativeLoaderNamespace::Create(
       namespace_name, library_path, permitted_path, parent_ns, is_shared,
       target_sdk_version < 24 /* is_exempt_list_enabled */, also_used_as_anonymous);
   if (!app_ns.ok()) {
     return app_ns.error();
   }
   // ... and link to other namespaces to allow access to some public libraries
   bool is_bridged = app_ns->IsBridged();

   auto system_ns = NativeLoaderNamespace::GetSystemNamespace(is_bridged);
   if (!system_ns.ok()) {
     return system_ns.error();
   }

   auto linked = app_ns->Link(&system_ns.value(), system_exposed_libraries);
   if (!linked.ok()) {
     return linked.error();
   }

   for (const auto&[apex_ns_name, public_libs] : apex_public_libraries()) {
     auto ns = NativeLoaderNamespace::GetExportedNamespace(apex_ns_name, is_bridged);
     // Even if APEX namespace is visible, it may not be available to bridged.
     if (ns.ok()) {
       linked = app_ns->Link(&ns.value(), public_libs);
       if (!linked.ok()) {
         return linked.error();
       }
     }
   }

   // Give access to VNDK-SP libraries from the 'vndk' namespace for unbundled vendor apps.
   if (unbundled_app_origin == APK_ORIGIN_VENDOR && !vndksp_libraries_vendor().empty()) {
     auto vndk_ns = NativeLoaderNamespace::GetExportedNamespace(kVndkNamespaceName, is_bridged);
     if (vndk_ns.ok()) {
       linked = app_ns->Link(&vndk_ns.value(), vndksp_libraries_vendor());
       if (!linked.ok()) {
         return linked.error();
       }
     }
   }

   // Give access to VNDK-SP libraries from the 'vndk_product' namespace for unbundled product apps.
   if (unbundled_app_origin == APK_ORIGIN_PRODUCT && !vndksp_libraries_product().empty()) {
     auto vndk_ns = NativeLoaderNamespace::GetExportedNamespace(kVndkProductNamespaceName, is_bridged);
     if (vndk_ns.ok()) {
       linked = app_ns->Link(&vndk_ns.value(), vndksp_libraries_product());
       if (!linked.ok()) {
         return linked.error();
       }
     }
   }

   for (const std::string& each_jar_path : android::base::Split(dex_path, ":")) {
     auto apex_ns_name = FindApexNamespaceName(each_jar_path);
     if (apex_ns_name.ok()) {
       const auto& jni_libs = apex_jni_libraries(*apex_ns_name);
       if (jni_libs != "") {
         auto apex_ns = NativeLoaderNamespace::GetExportedNamespace(*apex_ns_name, is_bridged);
         if (apex_ns.ok()) {
           linked = app_ns->Link(&apex_ns.value(), jni_libs);
           if (!linked.ok()) {
             return linked.error();
           }
         }
       }
     }
   }

   auto vendor_libs = filter_public_libraries(target_sdk_version, uses_libraries,
                                              vendor_public_libraries());
   if (!vendor_libs.empty()) {
     auto vendor_ns = NativeLoaderNamespace::GetExportedNamespace(kVendorNamespaceName, is_bridged);
     // when vendor_ns is not configured, link to the system namespace
     auto target_ns = vendor_ns.ok() ? vendor_ns : system_ns;
     if (target_ns.ok()) {
       linked = app_ns->Link(&target_ns.value(), vendor_libs);
       if (!linked.ok()) {
         return linked.error();
       }
     }
   }

   auto product_libs = filter_public_libraries(target_sdk_version, uses_libraries,
                                               product_public_libraries());
   if (!product_libs.empty()) {
     auto target_ns = system_ns;
     if (is_product_vndk_version_defined()) {
       // If ro.product.vndk.version is defined, product namespace provides the product libraries.
       target_ns = NativeLoaderNamespace::GetExportedNamespace(kProductNamespaceName, is_bridged);
     }
     if (target_ns.ok()) {
       linked = app_ns->Link(&target_ns.value(), product_libs);
       if (!linked.ok()) {
         return linked.error();
       }
     } else {
       // The linkerconfig must have a problem on defining the product namespace in the system
       // section. Skip linking product namespace. This will not affect most of the apps. Only the
       // apps that requires the product public libraries will fail.
       ALOGW("Namespace for product libs not found: %s", target_ns.error().message().c_str());
     }
   }

   auto& emplaced = namespaces_.emplace_back(
       std::make_pair(env->NewWeakGlobalRef(class_loader), *app_ns));
   if (is_main_classloader) {
     app_main_namespace_ = &emplaced.second;
   }
   return &emplaced.second;
 }

 NativeLoaderNamespace* LibraryNamespaces::FindNamespaceByClassLoader(JNIEnv* env,
                                                                      jobject class_loader) {
   auto it = std::find_if(namespaces_.begin(), namespaces_.end(),
                          [&](const std::pair<jweak, NativeLoaderNamespace>& value) {
                            return env->IsSameObject(value.first, class_loader);
                          });
   if (it != namespaces_.end()) {
     return &it->second;
   }

   return nullptr;
 }

 NativeLoaderNamespace* LibraryNamespaces::FindParentNamespaceByClassLoader(JNIEnv* env,
                                                                            jobject class_loader) {
   jobject parent_class_loader = GetParentClassLoader(env, class_loader);

   while (parent_class_loader != nullptr) {
     NativeLoaderNamespace* ns;
     if ((ns = FindNamespaceByClassLoader(env, parent_class_loader)) != nullptr) {
       return ns;
     }

     parent_class_loader = GetParentClassLoader(env, parent_class_loader);
   }

   return nullptr;
 }

 base::Result<std::string> FindApexNamespaceName(const std::string& location) {
   // Lots of implicit assumptions here: we expect `location` to be of the form:
   // /apex/modulename/...
   //
   // And we extract from it 'modulename', and then apply mangling rule to get namespace name for it.
   if (android::base::StartsWith(location, kApexPath)) {
     size_t start_index = strlen(kApexPath);
     size_t slash_index = location.find_first_of('/', start_index);
     LOG_ALWAYS_FATAL_IF((slash_index == std::string::npos),
                         "Error finding namespace of apex: no slash in path %s", location.c_str());
     std::string name = location.substr(start_index, slash_index - start_index);
     std::replace(name.begin(), name.end(), '.', '_');
     return name;
   }
   return base::Error();
 }

 }  // namespace android::nativeloader

 #endif  // defined(ART_TARGET_ANDROID)
	/*
	* Copyright (C) 2019 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.
	*/

	#if defined(ART_TARGET_ANDROID)

	#include "library_namespaces.h"

	#include <dirent.h>
	#include <dlfcn.h>

	#include <regex>
	#include <string>
	#include <vector>

	#include <android-base/file.h>
	#include <android-base/logging.h>
	#include <android-base/macros.h>
	#include <android-base/result.h>
	#include <android-base/strings.h>
	#include <nativehelper/scoped_utf_chars.h>

	#include "nativeloader/dlext_namespaces.h"
	#include "public_libraries.h"
	#include "utils.h"

	namespace android::nativeloader {

	namespace {

	constexpr const char* kApexPath = "/apex/";

	// The device may be configured to have the vendor libraries loaded to a separate namespace.
	// For historical reasons this namespace was named sphal but effectively it is intended
	// to use to load vendor libraries to separate namespace with controlled interface between
	// vendor and system namespaces.
	constexpr const char* kVendorNamespaceName = "sphal";
	// Similar to sphal namespace, product namespace provides some product libraries.
	constexpr const char* kProductNamespaceName = "product";

	// vndk namespace for unbundled vendor apps
	constexpr const char* kVndkNamespaceName = "vndk";
	// vndk_product namespace for unbundled product apps
	constexpr const char* kVndkProductNamespaceName = "vndk_product";

	// classloader-namespace is a linker namespace that is created for the loaded
	// app. To be specific, it is created for the app classloader. When
	// System.load() is called from a Java class that is loaded from the
	// classloader, the classloader-namespace namespace associated with that
	// classloader is selected for dlopen. The namespace is configured so that its
	// search path is set to the app-local JNI directory and it is linked to the
	// system namespace with the names of libs listed in the public.libraries.txt.
	// This way an app can only load its own JNI libraries along with the public libs.
	constexpr const char* kClassloaderNamespaceName = "classloader-namespace";
	// Same thing for vendor APKs.
	constexpr const char* kVendorClassloaderNamespaceName = "vendor-classloader-namespace";
	// If the namespace is shared then add this suffix to form
	// "classloader-namespace-shared" or "vendor-classloader-namespace-shared",
	// respectively. A shared namespace (cf. ANDROID_NAMESPACE_TYPE_SHARED) has
	// inherited all the libraries of the parent classloader namespace, or the
	// system namespace for the main app classloader. It is used to give full
	// access to the platform libraries for apps bundled in the system image,
	// including their later updates installed in /data.
	constexpr const char* kSharedNamespaceSuffix = "-shared";

	// (http://b/27588281) This is a workaround for apps using custom classloaders and calling
	// System.load() with an absolute path which is outside of the classloader library search path.
	// This list includes all directories app is allowed to access this way.
	constexpr const char* kWhitelistedDirectories = "/data:/mnt/expand";

	constexpr const char* kVendorLibPath = "/vendor/" LIB;
	constexpr const char* kProductLibPath = "/product/" LIB ":/system/product/" LIB;

	const std::regex kVendorDexPathRegex("(^\|:)/vendor/");
	const std::regex kProductDexPathRegex("(^\|:)(/system)?/product/");

	// Define origin of APK if it is from vendor partition or product partition
	using ApkOrigin = enum {
	APK_ORIGIN_DEFAULT = 0,
	APK_ORIGIN_VENDOR = 1,
	APK_ORIGIN_PRODUCT = 2,
	};

	jobject GetParentClassLoader(JNIEnv* env, jobject class_loader) {
	jclass class_loader_class = env->FindClass("java/lang/ClassLoader");
	jmethodID get_parent =
	env->GetMethodID(class_loader_class, "getParent", "()Ljava/lang/ClassLoader;");

	return env->CallObjectMethod(class_loader, get_parent);
	}

	ApkOrigin GetApkOriginFromDexPath(const std::string& dex_path) {
	ApkOrigin apk_origin = APK_ORIGIN_DEFAULT;
	if (std::regex_search(dex_path, kVendorDexPathRegex)) {
	apk_origin = APK_ORIGIN_VENDOR;
	}
	if (std::regex_search(dex_path, kProductDexPathRegex)) {
	LOG_ALWAYS_FATAL_IF(apk_origin == APK_ORIGIN_VENDOR,
	"Dex path contains both vendor and product partition : %s",
	dex_path.c_str());

	apk_origin = APK_ORIGIN_PRODUCT;
	}
	return apk_origin;
	}

	} // namespace

	void LibraryNamespaces::Initialize() {
	// Once public namespace is initialized there is no
	// point in running this code - it will have no effect
	// on the current list of public libraries.
	if (initialized_) {
	return;
	}

	// Load the preloadable public libraries. Since libnativeloader is in the
	// com_android_art namespace, use OpenSystemLibrary rather than dlopen to
	// ensure the libraries are loaded in the system namespace.
	//
	// TODO(dimitry): this is a bit misleading since we do not know
	// if the vendor public library is going to be opened from /vendor/lib
	// we might as well end up loading them from /system/lib or /product/lib
	// For now we rely on CTS test to catch things like this but
	// it should probably be addressed in the future.
	for (const std::string& soname : android::base::Split(preloadable_public_libraries(), ":")) {
	void* handle = OpenSystemLibrary(soname.c_str(), RTLD_NOW \| RTLD_NODELETE);
	LOG_ALWAYS_FATAL_IF(handle == nullptr,
	"Error preloading public library %s: %s", soname.c_str(), dlerror());
	}
	}

	// "ALL" is a magic name that allows all public libraries even when the
	// target SDK is > 30. Currently this is used for (Java) shared libraries
	// which don't use <uses-native-library>
	// TODO(b/142191088) remove this hack
	static constexpr const char LIBRARY_ALL[] = "ALL";

	// Returns the colon-separated list of library names by filtering uses_libraries from
	// public_libraries. The returned names will actually be available to the app. If the app is pre-S
	// (<= 30), the filtering is not done; the entire public_libraries are provided.
	static const std::string filter_public_libraries(
	uint32_t target_sdk_version, const std::vector<std::string>& uses_libraries,
	const std::string& public_libraries) {
	// Apps targeting Android 11 or earlier gets all public libraries
	if (target_sdk_version <= 30) {
	return public_libraries;
	}
	if (std::find(uses_libraries.begin(), uses_libraries.end(), LIBRARY_ALL) !=
	uses_libraries.end()) {
	return public_libraries;
	}
	std::vector<std::string> filtered;
	std::vector<std::string> orig = android::base::Split(public_libraries, ":");
	for (const auto& lib : uses_libraries) {
	if (std::find(orig.begin(), orig.end(), lib) != orig.end()) {
	filtered.emplace_back(lib);
	}
	}
	return android::base::Join(filtered, ":");
	}

	Result<NativeLoaderNamespace> LibraryNamespaces::Create(JNIEnv env, uint32_t target_sdk_version,
	jobject class_loader, bool is_shared,
	jstring dex_path_j,
	jstring java_library_path,
	jstring java_permitted_path,
	jstring uses_library_list) {
	std::string library_path; // empty string by default.
	std::string dex_path;

	if (java_library_path != nullptr) {
	ScopedUtfChars library_path_utf_chars(env, java_library_path);
	library_path = library_path_utf_chars.c_str();
	}

	if (dex_path_j != nullptr) {
	ScopedUtfChars dex_path_chars(env, dex_path_j);
	dex_path = dex_path_chars.c_str();
	}

	std::vector<std::string> uses_libraries;
	if (uses_library_list != nullptr) {
	ScopedUtfChars names(env, uses_library_list);
	uses_libraries = android::base::Split(names.c_str(), ":");
	} else {
	// uses_library_list could be nullptr when System.loadLibrary is called from a
	// custom classloader. In that case, we don't know the list of public
	// libraries because we don't know which apk the classloader is for. Only
	// choices we can have are 1) allowing all public libs (as before), or 2)
	// not allowing all but NDK libs. Here we take #1 because #2 would surprise
	// developers unnecessarily.
	// TODO(b/142191088) finalize the policy here. We could either 1) allow all
	// public libs, 2) disallow any lib, or 3) use the libs that were granted to
	// the first (i.e. app main) classloader.
	uses_libraries.emplace_back(LIBRARY_ALL);
	}

	ApkOrigin apk_origin = GetApkOriginFromDexPath(dex_path);

	// (http://b/27588281) This is a workaround for apps using custom
	// classloaders and calling System.load() with an absolute path which
	// is outside of the classloader library search path.
	//
	// This part effectively allows such a classloader to access anything
	// under /data and /mnt/expand
	std::string permitted_path = kWhitelistedDirectories;

	if (java_permitted_path != nullptr) {
	ScopedUtfChars path(env, java_permitted_path);
	if (path.c_str() != nullptr && path.size() > 0) {
	permitted_path = permitted_path + ":" + path.c_str();
	}
	}

	LOG_ALWAYS_FATAL_IF(FindNamespaceByClassLoader(env, class_loader) != nullptr,
	"There is already a namespace associated with this classloader");

	std::string system_exposed_libraries = default_public_libraries();
	std::string namespace_name = kClassloaderNamespaceName;
	ApkOrigin unbundled_app_origin = APK_ORIGIN_DEFAULT;
	if ((apk_origin == APK_ORIGIN_VENDOR \|\|
	(apk_origin == APK_ORIGIN_PRODUCT &&
	is_product_vndk_version_defined())) &&
	!is_shared) {
	unbundled_app_origin = apk_origin;
	// For vendor / product apks, give access to the vendor / product lib even though
	// they are treated as unbundled; the libs and apks are still bundled
	// together in the vendor / product partition.
	const char* origin_partition;
	const char* origin_lib_path;
	const char* llndk_libraries;

	switch (apk_origin) {
	case APK_ORIGIN_VENDOR:
	origin_partition = "vendor";
	origin_lib_path = kVendorLibPath;
	llndk_libraries = llndk_libraries_vendor().c_str();
	break;
	case APK_ORIGIN_PRODUCT:
	origin_partition = "product";
	origin_lib_path = kProductLibPath;
	llndk_libraries = llndk_libraries_product().c_str();
	break;
	default:
	origin_partition = "unknown";
	origin_lib_path = "";
	llndk_libraries = "";
	}
	library_path = library_path + ":" + origin_lib_path;
	permitted_path = permitted_path + ":" + origin_lib_path;

	// Also give access to LLNDK libraries since they are available to vendor or product
	system_exposed_libraries = system_exposed_libraries + ":" + llndk_libraries;

	// Different name is useful for debugging
	namespace_name = kVendorClassloaderNamespaceName;
	ALOGD("classloader namespace configured for unbundled %s apk. library_path=%s",
	origin_partition, library_path.c_str());
	} else {
	auto libs = filter_public_libraries(target_sdk_version, uses_libraries,
	extended_public_libraries());
	// extended public libraries are NOT available to vendor apks, otherwise it
	// would be system->vendor violation.
	if (!libs.empty()) {
	system_exposed_libraries = system_exposed_libraries + ':' + libs;
	}
	}

	if (is_shared) {
	// Show in the name that the namespace was created as shared, for debugging
	// purposes.
	namespace_name = namespace_name + kSharedNamespaceSuffix;
	}

	// Create the app namespace
	NativeLoaderNamespace* parent_ns = FindParentNamespaceByClassLoader(env, class_loader);
	// Heuristic: the first classloader with non-empty library_path is assumed to
	// be the main classloader for app
	// TODO(b/139178525) remove this heuristic by determining this in LoadedApk (or its
	// friends) and then passing it down to here.
	bool is_main_classloader = app_main_namespace_ == nullptr && !library_path.empty();
	// Policy: the namespace for the main classloader is also used as the
	// anonymous namespace.
	bool also_used_as_anonymous = is_main_classloader;
	// Note: this function is executed with g_namespaces_mutex held, thus no
	// racing here.
	auto app_ns = NativeLoaderNamespace::Create(
	namespace_name, library_path, permitted_path, parent_ns, is_shared,
	target_sdk_version < 24 /* is_exempt_list_enabled */, also_used_as_anonymous);
	if (!app_ns.ok()) {
	return app_ns.error();
	}
	// ... and link to other namespaces to allow access to some public libraries
	bool is_bridged = app_ns->IsBridged();

	auto system_ns = NativeLoaderNamespace::GetSystemNamespace(is_bridged);
	if (!system_ns.ok()) {
	return system_ns.error();
	}

	auto linked = app_ns->Link(&system_ns.value(), system_exposed_libraries);
	if (!linked.ok()) {
	return linked.error();
	}

	for (const auto&[apex_ns_name, public_libs] : apex_public_libraries()) {
	auto ns = NativeLoaderNamespace::GetExportedNamespace(apex_ns_name, is_bridged);
	// Even if APEX namespace is visible, it may not be available to bridged.
	if (ns.ok()) {
	linked = app_ns->Link(&ns.value(), public_libs);
	if (!linked.ok()) {
	return linked.error();
	}
	}
	}

	// Give access to VNDK-SP libraries from the 'vndk' namespace for unbundled vendor apps.
	if (unbundled_app_origin == APK_ORIGIN_VENDOR && !vndksp_libraries_vendor().empty()) {
	auto vndk_ns = NativeLoaderNamespace::GetExportedNamespace(kVndkNamespaceName, is_bridged);
	if (vndk_ns.ok()) {
	linked = app_ns->Link(&vndk_ns.value(), vndksp_libraries_vendor());
	if (!linked.ok()) {
	return linked.error();
	}
	}
	}

	// Give access to VNDK-SP libraries from the 'vndk_product' namespace for unbundled product apps.
	if (unbundled_app_origin == APK_ORIGIN_PRODUCT && !vndksp_libraries_product().empty()) {
	auto vndk_ns = NativeLoaderNamespace::GetExportedNamespace(kVndkProductNamespaceName, is_bridged);
	if (vndk_ns.ok()) {
	linked = app_ns->Link(&vndk_ns.value(), vndksp_libraries_product());
	if (!linked.ok()) {
	return linked.error();
	}
	}
	}

	for (const std::string& each_jar_path : android::base::Split(dex_path, ":")) {
	auto apex_ns_name = FindApexNamespaceName(each_jar_path);
	if (apex_ns_name.ok()) {
	const auto& jni_libs = apex_jni_libraries(*apex_ns_name);
	if (jni_libs != "") {
	auto apex_ns = NativeLoaderNamespace::GetExportedNamespace(*apex_ns_name, is_bridged);
	if (apex_ns.ok()) {
	linked = app_ns->Link(&apex_ns.value(), jni_libs);
	if (!linked.ok()) {
	return linked.error();
	}
	}
	}
	}
	}

	auto vendor_libs = filter_public_libraries(target_sdk_version, uses_libraries,
	vendor_public_libraries());
	if (!vendor_libs.empty()) {
	auto vendor_ns = NativeLoaderNamespace::GetExportedNamespace(kVendorNamespaceName, is_bridged);
	// when vendor_ns is not configured, link to the system namespace
	auto target_ns = vendor_ns.ok() ? vendor_ns : system_ns;
	if (target_ns.ok()) {
	linked = app_ns->Link(&target_ns.value(), vendor_libs);
	if (!linked.ok()) {
	return linked.error();
	}
	}
	}

	auto product_libs = filter_public_libraries(target_sdk_version, uses_libraries,
	product_public_libraries());
	if (!product_libs.empty()) {
	auto target_ns = system_ns;
	if (is_product_vndk_version_defined()) {
	// If ro.product.vndk.version is defined, product namespace provides the product libraries.
	target_ns = NativeLoaderNamespace::GetExportedNamespace(kProductNamespaceName, is_bridged);
	}
	if (target_ns.ok()) {
	linked = app_ns->Link(&target_ns.value(), product_libs);
	if (!linked.ok()) {
	return linked.error();
	}
	} else {
	// The linkerconfig must have a problem on defining the product namespace in the system
	// section. Skip linking product namespace. This will not affect most of the apps. Only the
	// apps that requires the product public libraries will fail.
	ALOGW("Namespace for product libs not found: %s", target_ns.error().message().c_str());
	}
	}

	auto& emplaced = namespaces_.emplace_back(
	std::make_pair(env->NewWeakGlobalRef(class_loader), *app_ns));
	if (is_main_classloader) {
	app_main_namespace_ = &emplaced.second;
	}
	return &emplaced.second;
	}

	NativeLoaderNamespace* LibraryNamespaces::FindNamespaceByClassLoader(JNIEnv* env,
	jobject class_loader) {
	auto it = std::find_if(namespaces_.begin(), namespaces_.end(),
	[&](const std::pair<jweak, NativeLoaderNamespace>& value) {
	return env->IsSameObject(value.first, class_loader);
	});
	if (it != namespaces_.end()) {
	return &it->second;
	}

	return nullptr;
	}

	NativeLoaderNamespace* LibraryNamespaces::FindParentNamespaceByClassLoader(JNIEnv* env,
	jobject class_loader) {
	jobject parent_class_loader = GetParentClassLoader(env, class_loader);

	while (parent_class_loader != nullptr) {
	NativeLoaderNamespace* ns;
	if ((ns = FindNamespaceByClassLoader(env, parent_class_loader)) != nullptr) {
	return ns;
	}

	parent_class_loader = GetParentClassLoader(env, parent_class_loader);
	}

	return nullptr;
	}

	base::Result<std::string> FindApexNamespaceName(const std::string& location) {
	// Lots of implicit assumptions here: we expect `location` to be of the form:
	// /apex/modulename/...
	//
	// And we extract from it 'modulename', and then apply mangling rule to get namespace name for it.
	if (android::base::StartsWith(location, kApexPath)) {
	size_t start_index = strlen(kApexPath);
	size_t slash_index = location.find_first_of('/', start_index);
	LOG_ALWAYS_FATAL_IF((slash_index == std::string::npos),
	"Error finding namespace of apex: no slash in path %s", location.c_str());
	std::string name = location.substr(start_index, slash_index - start_index);
	std::replace(name.begin(), name.end(), '.', '_');
	return name;
	}
	return base::Error();
	}

	} // namespace android::nativeloader

	#endif // defined(ART_TARGET_ANDROID)