Modules: Introduce a generic DFM native library loading system

DFMs that include both Java and native code will probably use JNI. This
change introduces a reusable mechanism to load the native library and
register its JNI methods.

Key points:

- There are 3 build variants supported:
  1. Production builds with lld-generated partitions.
  2. Component build (with feature code in a component).
  3. Fallback release build (feature code in the main library)

- For consistency, explicit JNI registration is done in both
  ChromeModern and Monochrome.

- The Test Dummy module is moved over to use this new system. VR will
  join the fun in a follow-on change.

- Currently, modules must supply an explicit JNI registration method.
  Common code will locate this method and call it, at the appropriate
  time, on behalf of the module.

Bug: 870055
Change-Id: Id400ff00b4be65f71536a4acffdfcf93cc3bea58
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1822846
Commit-Queue: Christopher Grant <cjgrant@chromium.org>
Reviewed-by: Tibor Goldschwendt <tiborg@chromium.org>
Reviewed-by: Andrew Grieve <agrieve@chromium.org>
Cr-Commit-Position: refs/heads/master@{#700276}

base/android/bundle_utils.cc

@@ -62,12 +62,6 @@ bool BundleUtils::IsBundle() {
   return Java_BundleUtils_isBundle(base::android::AttachCurrentThread());
 }
 
-// static
-void* BundleUtils::DlOpenModuleLibrary(const std::string& library_name) {
-  std::string library_path = ResolveLibraryPath(library_name);
-  return dlopen(library_path.c_str(), RTLD_LOCAL);
-}
-
 // static
 void* BundleUtils::DlOpenModuleLibraryPartition(
     const std::string& library_name) {

base/android/bundle_utils.h

@@ -18,9 +18,6 @@ class BASE_EXPORT BundleUtils {
   // Returns true if the current build is a bundle.
   static bool IsBundle();
 
-  // dlopen wrapper that works for native libraries in dynamic feature modules.
-  static void* DlOpenModuleLibrary(const std::string& libary_name);
-
   // dlopen wrapper that works for partitioned native libraries in dynamic
   // feature modules. This routine looks up the partition's address space in a
   // table of main library symbols, and uses it when loading the feature

build/android/gyp/generate_linker_version_script.py

@@ -42,6 +42,10 @@ def main():
       dest='whitelists',
       help='Path to an input file containing a whitelist of extra symbols to '
       'export, one symbol per line. Multiple files may be specified.')
+  parser.add_argument(
+      '--export-feature-registrations',
+      action='store_true',
+      help='Export JNI_OnLoad_* methods')
   options = parser.parse_args()
 
   # JNI_OnLoad is always exported.
@@ -52,6 +56,9 @@ def main():
   if options.export_java_symbols:
     symbol_list.append('Java_*')
 
+  if options.export_feature_registrations:
+    symbol_list.append('JNI_OnLoad_*')
+
   for whitelist in options.whitelists:
     with open(whitelist, 'rt') as f:
       for line in f:

build/config/android/linker_version_script.gni

@@ -27,6 +27,11 @@ template("generate_linker_version_script") {
       args += [ "--export-java-symbols" ]
     }
 
+    if (defined(invoker.export_feature_registrations) &&
+        invoker.export_feature_registrations) {
+      args += [ "--export-feature-registrations" ]
+    }
+
     if (defined(invoker.export_symbol_whitelist_files)) {
       foreach(file_, invoker.export_symbol_whitelist_files) {
         inputs += [ file_ ]

chrome/android/BUILD.gn

@@ -1195,7 +1195,6 @@ chrome_common_shared_library("libchrome") {
   if (enable_vr) {
     deps += [ "//chrome/browser/android/vr:module_factory" ]
   }
-  deps += [ "//chrome/android/features/test_dummy/internal:base_module_native" ]
 
   allow_partitions = true
   module_descs = chrome_modern_module_descs
@@ -1212,7 +1211,6 @@ chrome_common_shared_library("libchromefortest") {
     ":chrome_jni_for_test_registration($default_toolchain)",
     "//base/test:test_support",
     "//chrome:chrome_android_core",
-    "//chrome/android/features/test_dummy/internal:base_module_native",
     "//chrome/browser/android/metrics:ukm_utils_for_test",
     "//components/autofill_assistant/browser:test_support",
     "//components/crash/android:crash_android",
@@ -1226,6 +1224,10 @@ chrome_common_shared_library("libchromefortest") {
   if (enable_vr) {
     deps += [ "//chrome/browser/android/vr:test_support" ]
   }
+
+  # TODO(http://crbug.com/1008123): Include module native code by enumerating
+  # module descriptors.
+  deps += [ "//chrome/android/modules/test_dummy/internal:native" ]
 }
 
 # Ensure that .pak files are built only once (build them in the default
@@ -1461,8 +1463,6 @@ template("libmonochrome_apk_or_bundle_tmpl") {
     if (enable_vr) {
       deps += [ "//chrome/browser/android/vr:module_factory" ]
     }
-    deps +=
-        [ "//chrome/android/features/test_dummy/internal:base_module_native" ]
 
     is_monochrome = true
     allow_partitions = true

chrome/android/chrome_common_shared_library.gni

@@ -40,8 +40,9 @@ template("chrome_common_shared_library") {
 
   # Create a partitioned libraries if the build config supports it, and the
   # invoker wants partitions.
-  _generate_partitions = defined(invoker.allow_partitions) &&
-                         invoker.allow_partitions && use_native_modules
+  _allow_partitions =
+      defined(invoker.allow_partitions) && invoker.allow_partitions
+  _generate_partitions = _allow_partitions && use_native_modules
   if (_generate_partitions) {
     assert(defined(invoker.module_descs))
   } else {
@@ -55,6 +56,7 @@ template("chrome_common_shared_library") {
     linker_script = _linker_script
     export_java_symbols = _export_java_symbols
     if (_generate_partitions) {
+      export_feature_registrations = true
       export_symbol_whitelist_files = []
       foreach(_module_desc, invoker.module_descs) {
         if (defined(_module_desc.native_entrypoints)) {
@@ -105,7 +107,7 @@ template("chrome_common_shared_library") {
       }
     }
 
-    if (_generate_partitions) {
+    if (_allow_partitions) {
       partitions = []
       foreach(_module_desc, invoker.module_descs) {
         if (defined(_module_desc.native_deps)) {

chrome/android/features/test_dummy/internal/BUILD.gn

@@ -22,16 +22,19 @@ android_library("java") {
   ]
   java_files =
       [ "java/src/org/chromium/chrome/features/test_dummy/TestDummyImpl.java" ]
+
+  annotation_processor_deps = [ "//base/android/jni_generator:jni_processor" ]
+  deps += [ "//base:jni_java" ]
 }
 
 source_set("native") {
   sources = [
-    "test_dummy.cc",
+    "test_dummy_impl.cc",
   ]
 
   deps = [
+    ":jni_headers",
     "//base",
-    "//chrome/android/features/test_dummy/public:native",
   ]
 }
 
@@ -48,33 +51,11 @@ android_library("base_module_java") {
   ]
   java_files = [
     "java/src/org/chromium/chrome/features/test_dummy/TestDummyActivity.java",
-    "java/src/org/chromium/chrome/features/test_dummy/TestDummySupport.java",
-  ]
-
-  annotation_processor_deps = [ "//base/android/jni_generator:jni_processor" ]
-  deps += [ "//base:jni_java" ]
-}
-
-buildflag_header("buildflags") {
-  header = "buildflags.h"
-  flags = [ "USE_NATIVE_MODULES=$use_native_modules" ]
-}
-
-source_set("base_module_native") {
-  sources = [
-    "test_dummy_client.cc",
-  ]
-  deps = [
-    ":test_dummy_jni_headers",
-    "//base",
-  ]
-  public_deps = [
-    ":buildflags",
   ]
 }
 
-generate_jni("test_dummy_jni_headers") {
+generate_jni("jni_headers") {
   sources = [
-    "java/src/org/chromium/chrome/features/test_dummy/TestDummySupport.java",
+    "java/src/org/chromium/chrome/features/test_dummy/TestDummyImpl.java",
   ]
 }

chrome/android/features/test_dummy/internal/java/src/org/chromium/chrome/features/test_dummy/TestDummyImpl.java

@@ -11,6 +11,7 @@ import android.support.v7.app.AlertDialog;
 import androidx.annotation.IntDef;
 
 import org.chromium.base.Log;
+import org.chromium.base.annotations.NativeMethods;
 
 import java.io.IOException;
 import java.io.InputStream;
@@ -49,6 +50,11 @@ public class TestDummyImpl implements TestDummy {
         }
     }
 
+    @NativeMethods
+    interface Natives {
+        int execute();
+    }
+
     private void showDoneDialog(Activity activity, @TestCase int testCase, boolean pass) {
         String message = "Test Case %d: " + (pass ? "pass" : "fail");
         AlertDialog.Builder builder = new AlertDialog.Builder(activity);
@@ -63,8 +69,9 @@ public class TestDummyImpl implements TestDummy {
     }
 
     private void executeNative(Activity activity) {
-        boolean result = TestDummySupport.openAndVerifyNativeLibrary();
-        showDoneDialog(activity, TestCase.EXECUTE_NATIVE, result);
+        int value = TestDummyImplJni.get().execute();
+        boolean pass = (value == 123);
+        showDoneDialog(activity, TestCase.EXECUTE_NATIVE, pass);
     }
 
     private void loadJavaResource(Activity activity) {

chrome/android/features/test_dummy/internal/java/src/org/chromium/chrome/features/test_dummy/TestDummySupport.java

-// Copyright 2019 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-package org.chromium.chrome.features.test_dummy;
-
-import org.chromium.base.annotations.NativeMethods;
-
-/** Support class to proxy JNI calls from module Java to module native. */
-//@MainDex
-public class TestDummySupport {
-    /** JNI calls for exercising native parts of the DFM. */
-    @NativeMethods
-    public interface Natives {
-        boolean openAndVerifyNativeLibrary();
-    }
-
-    public static boolean openAndVerifyNativeLibrary() {
-        return TestDummySupportJni.get().openAndVerifyNativeLibrary();
-    }
-}

chrome/android/features/test_dummy/internal/test_dummy_client.cc

-// Copyright 2019 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#include <android/dlext.h>
-#include <dlfcn.h>
-
-#include "base/android/bundle_utils.h"
-#include "base/logging.h"
-#include "chrome/android/features/test_dummy/internal/buildflags.h"
-#include "chrome/android/features/test_dummy/internal/test_dummy_jni_headers/TestDummySupport_jni.h"
-
-static jboolean JNI_TestDummySupport_OpenAndVerifyNativeLibrary(JNIEnv* env) {
-#if BUILDFLAG(USE_NATIVE_MODULES)
-  // Note that the library opened here is not closed. dlclosing() libraries has
-  // proven to be problematic. See https://crbug.com/994029.
-  void* handle =
-      base::android::BundleUtils::DlOpenModuleLibraryPartition("test_dummy");
-  if (handle == nullptr) {
-    LOG(ERROR) << "Cannot open test library: " << dlerror();
-    return false;
-  }
-
-  void* symbol = dlsym(handle, "TestDummyEntrypoint");
-  if (symbol == nullptr) {
-    LOG(ERROR) << "Cannot find test library symbol";
-    return false;
-  }
-
-  typedef int TestFunction();
-  TestFunction* test_function = reinterpret_cast<TestFunction*>(symbol);
-  if (test_function() != 123) {
-    LOG(ERROR) << "Unexpected value from test library";
-    return false;
-  }
-#endif
-
-  return true;
-}

chrome/android/features/test_dummy/internal/test_dummy.cc → chrome/android/features/test_dummy/internal/test_dummy_impl.cc

@@ -2,17 +2,10 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "chrome/android/features/test_dummy/public/test_dummy.h"
-
 #include "base/logging.h"
+#include "chrome/android/features/test_dummy/internal/jni_headers/TestDummyImpl_jni.h"
 
-namespace test_dummy {
-
-int TestDummy() {
-  // Log something to utilize base library code. This is necessary to ensure
-  // that calls to base code are linked properly.
-  LOG(WARNING) << "Running test dummy native library.";
+static int JNI_TestDummyImpl_Execute(JNIEnv* env) {
+  LOG(INFO) << "Running test dummy native library";
   return 123;
 }
-
-}  // namespace test_dummy

chrome/android/features/test_dummy/public/BUILD.gn

@@ -8,9 +8,3 @@ android_library("java") {
   java_files =
       [ "java/src/org/chromium/chrome/features/test_dummy/TestDummy.java" ]
 }
-
-source_set("native") {
-  sources = [
-    "test_dummy.h",
-  ]
-}

chrome/android/features/test_dummy/public/test_dummy.h

-// Copyright 2019 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#ifndef CHROME_ANDROID_FEATURES_TEST_DUMMY_PUBLIC_TEST_DUMMY_H_
-#define CHROME_ANDROID_FEATURES_TEST_DUMMY_PUBLIC_TEST_DUMMY_H_
-
-namespace test_dummy {
-
-// The test_dummy feature's token native entrypoint.
-int TestDummy();
-
-}  // namespace test_dummy
-
-#endif  // CHROME_ANDROID_FEATURES_TEST_DUMMY_PUBLIC_TEST_DUMMY_H_

chrome/android/java/src/org/chromium/chrome/browser/ChromeActivity.java

@@ -162,6 +162,7 @@ import org.chromium.chrome.browser.widget.textbubble.TextBubble;
 import org.chromium.components.bookmarks.BookmarkId;
 import org.chromium.components.feature_engagement.EventConstants;
 import org.chromium.components.feature_engagement.Tracker;
+import org.chromium.components.module_installer.Module;
 import org.chromium.content_public.browser.LoadUrlParams;
 import org.chromium.content_public.browser.SelectionPopupController;
 import org.chromium.content_public.browser.WebContents;
@@ -1391,6 +1392,9 @@ public abstract class ChromeActivity<C extends ChromeActivityComponent>
         maybeRemoveWindowBackground();
         DownloadManagerService.getDownloadManagerService().onActivityLaunched();
 
+        // TODO(https://crbug.com/1008162): Have the Module system register its own observer.
+        Module.doDeferredNativeRegistrations();
+
         VrModuleProvider.maybeInit();
         VrModuleProvider.getDelegate().onNativeLibraryAvailable();
         ArDelegate arDelegate = ArDelegateProvider.getDelegate();

chrome/android/modules/chrome_feature_module_tmpl.gni

@@ -65,7 +65,8 @@ template("chrome_feature_module") {
       _loadable_modules_64_bit += _module_desc.loadable_modules_64_bit
     }
 
-    if (defined(_module_desc.native_deps) && _module_desc.native_deps != []) {
+    if (use_native_modules && defined(_module_desc.native_deps) &&
+        _module_desc.native_deps != []) {
       _arch = ""
       _toolchain = ""
       _root_out_dir = root_out_dir

chrome/android/modules/test_dummy/internal/BUILD.gn

@@ -3,6 +3,7 @@
 # found in the LICENSE file.
 
 import("//build/config/android/rules.gni")
+import("//chrome/android/modules/buildflags.gni")
 
 android_library("java") {
   java_files = [ "java/src/org/chromium/chrome/modules/test_dummy/TestDummyProviderImpl.java" ]
@@ -14,15 +15,66 @@ android_library("java") {
   ]
 }
 
-source_set("native") {
+# This group is effectively alias representing the module's native code,
+# allowing it to be named "native" for clarity in module descriptors. The
+# component target must be named according to the feature, so that the component
+# build's .cr.co library is named properly (ie. libtest_dummy.cr.so).
+group("native") {
+  deps = [
+    ":test_dummy",
+  ]
+}
+
+component("test_dummy") {
   sources = [
     "entrypoints.cc",
   ]
-
   deps = [
-    "//chrome/android/features/test_dummy/public:native",
+    "//base",
+    "//chrome/android/features/test_dummy/internal:native",
   ]
 
   # Test dummy native entrypoints belong in the partition.
-  cflags = [ "-fsymbol-partition=libtest_dummy.so" ]
+  if (use_native_modules) {
+    cflags = [ "-fsymbol-partition=libtest_dummy.so" ]
+  }
+
+  if (current_toolchain != default_toolchain) {
+    deps += [ ":jni_registration_secondary($default_toolchain)" ]
+  } else {
+    deps += [ ":jni_registration($default_toolchain)" ]
+  }
+}
+
+# TODO(https://crbug.com/1008109): Adapt JNI registration to point at a Java
+# target, instead of an APK/module target. This JNI registration target
+# points at ChromeModern's module, but it's used by Monochrome as well, since
+# both variants do explicit JNI registration in DFMs (for consistency).
+#
+# Alternatively, move to lazy JNI init for DFMs in Monochrome, by conditionally
+# including a registration stub, as Chrome's base library does. That requires
+# two sets of registration targets, so that the feature module template can
+# selectively pull in the real version or a stub.
+if (current_toolchain == default_toolchain) {
+  generate_jni_registration("jni_registration") {
+    target =
+        "//chrome/android:chrome_modern_public_bundle__test_dummy_bundle_module"
+    header_output = "$target_gen_dir/jni_registration.h"
+    namespace = "test_dummy"
+  }
+
+  # Note also: We cannot currently build JNI registration on secondary ABI
+  # toolchain (dependency issues). Therefore, for Monochrome's 32-bit library,
+  # we need to use the 64-bit side registration header that ChromeModern uses.
+  # However, it's in the 64-bit output directory. We need to also generate a copy
+  # for the 32-bit directory.
+  if (android_64bit_target_cpu) {
+    generate_jni_registration("jni_registration_secondary") {
+      target = "//chrome/android:chrome_modern_public_bundle__test_dummy_bundle_module"
+      header_output =
+          get_label_info(":native($android_secondary_abi_toolchain)",
+                         "target_gen_dir") + "/jni_registration.h"
+      namespace = "test_dummy"
+    }
+  }
 }

chrome/android/modules/test_dummy/internal/entrypoints.cc

@@ -2,12 +2,21 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "chrome/android/features/test_dummy/public/test_dummy.h"
+#include "base/android/jni_utils.h"
+#include "chrome/android/modules/test_dummy/internal/jni_registration.h"
 
 extern "C" {
-
-__attribute__((visibility("default"))) int TestDummyEntrypoint() {
-  return test_dummy::TestDummy();
+// This JNI registration method is found and called by module framework code.
+// Ideally, this code would be generated by the build.
+__attribute__((visibility("default"))) bool JNI_OnLoad_test_dummy(JNIEnv* env) {
+  if (!base::android::IsSelectiveJniRegistrationEnabled(env) &&
+      !test_dummy::RegisterNonMainDexNatives(env)) {
+    return false;
+  }
+  if (!test_dummy::RegisterMainDexNatives(env)) {
+    return false;
+  }
+  return true;
 }
 
 }  // extern "C"

chrome/android/modules/test_dummy/internal/entrypoints.lst

-TestDummyEntrypoint

chrome/android/modules/test_dummy/test_dummy_module.gni

@@ -13,12 +13,8 @@ test_dummy_module_desc = {
     "//chrome/android/modules/test_dummy/internal:java",
   ]
 
-  if (use_native_modules) {
-    native_deps = [
-      "//chrome/android/features/test_dummy/internal:native",
-      "//chrome/android/modules/test_dummy/internal:native",
-    ]
-    native_entrypoints =
-        "//chrome/android/modules/test_dummy/internal/entrypoints.lst"
-  }
+  native_deps = [
+    "//chrome/android/features/test_dummy/internal:native",
+    "//chrome/android/modules/test_dummy/internal:native",
+  ]
 }

chrome/browser/BUILD.gn

@@ -2911,6 +2911,7 @@ jumbo_split_static_library("browser") {
       "//components/feed:feature_list",
       "//components/invalidation/impl:feature_list",
       "//components/language/android:language_bridge",
+      "//components/module_installer/android:native",
       "//components/omnibox/browser",
       "//components/page_load_metrics/browser",
       "//components/payments/content/android",

components/module_installer/android/BUILD.gn

@@ -3,6 +3,7 @@
 # found in the LICENSE file.
 
 import("//build/config/android/rules.gni")
+import("//chrome/android/modules/buildflags.gni")
 
 android_library("module_installer_java") {
   java_files = [
@@ -22,6 +23,7 @@ android_library("module_installer_java") {
 
   deps = [
     "//base:base_java",
+    "//base:jni_java",
     "//components/crash/android:java",
     "//third_party/google_android_play_core:com_google_android_play_core_java",
   ]
@@ -29,6 +31,8 @@ android_library("module_installer_java") {
   srcjar_deps = [ ":module_installer_build_config" ]
 
   jar_excluded_patterns = [ "*/ModuleInstallerConfig.class" ]
+
+  annotation_processor_deps = [ "//base/android/jni_generator:jni_processor" ]
 }
 
 android_library("module_installer_test_java") {
@@ -94,3 +98,29 @@ java_cpp_template("module_installer_apk_build_config") {
   ]
   defines = [ "IS_APK_BUILD" ]
 }
+
+source_set("native") {
+  sources = [
+    "module.cc",
+  ]
+  deps = [
+    ":jni_headers",
+    "//base",
+  ]
+
+  # The method used to load and register JNI for native libraries depends
+  # heavily on build type.
+  if (use_native_modules) {
+    defines = [ "LOAD_FROM_PARTITIONS" ]
+  } else if (is_component_build) {
+    defines = [ "LOAD_FROM_COMPONENTS" ]
+  } else {
+    defines = [ "LOAD_FROM_BASE_LIBRARY" ]
+  }
+}
+
+generate_jni("jni_headers") {
+  sources = [
+    "java/src/org/chromium/components/module_installer/Module.java",
+  ]
+}

components/module_installer/android/java/src/org/chromium/components/module_installer/Module.java

@@ -6,6 +6,8 @@ package org.chromium.components.module_installer;
 
 import org.chromium.base.StrictModeContext;
 import org.chromium.base.VisibleForTesting;
+import org.chromium.base.annotations.JNINamespace;
+import org.chromium.base.annotations.NativeMethods;
 
 import java.util.HashSet;
 import java.util.Set;
@@ -17,9 +19,12 @@ import java.util.Set;
  *
  * @param <T> The interface of the module/
  */
+@JNINamespace("module_installer")
 public class Module<T> {
     private static final Set<String> sInstantiatedModuleNames = new HashSet<>();
     private static final Set<String> sModulesUninstalledForTesting = new HashSet<>();
+    private static final Set<String> sPendingNativeRegistrations = new HashSet<>();
+    private static boolean sNativeInitialized;
     private final String mName;
     private final Class<T> mInterfaceClass;
     private final String mImplClassName;
@@ -34,13 +39,31 @@ public class Module<T> {
         sModulesUninstalledForTesting.add(moduleName);
     }
 
+    @NativeMethods
+    interface Natives {
+        void loadNativeLibrary(String name);
+    }
+
+    /**
+     * To be called after the main native library has been loaded. Any module instances
+     * created before the native library is loaded have their native component queued
+     * for loading and registration. Calling this methed completes that process.
+     **/
+    public static void doDeferredNativeRegistrations() {
+        for (String name : sPendingNativeRegistrations) {
+            loadNativeLibrary(name);
+        }
+        sPendingNativeRegistrations.clear();
+        sNativeInitialized = true;
+    }
+
     /**
      * Instantiates a module.
      *
      * @param name The module's name as used with {@link ModuleInstaller}.
      * @param interfaceClass {@link Class} object of the module interface.
      * @param implClassName fully qualified class name of the implementation of the module's
-     *interface.
+     *        interface.
      **/
     public Module(String name, Class<T> interfaceClass, String implClassName) {
         mName = name;
@@ -97,8 +120,24 @@ public class Module<T> {
                         | IllegalArgumentException e) {
                     throw new RuntimeException(e);
                 }
+
+                // Load the module's native library if there's one present, and the Chrome native
+                // library itself has been loaded.
+                if (sNativeInitialized) {
+                    loadNativeLibrary(mName);
+                } else {
+                    sPendingNativeRegistrations.add(mName);
+                }
             }
             return mImpl;
         }
     }
+
+    private static void loadNativeLibrary(String name) {
+        // TODO(https://crbug.com/870055): Whitelist modules, until each module explicitly indicates
+        // its need for library loading through this system.
+        if (!"test_dummy".equals(name)) return;
+
+        ModuleJni.get().loadNativeLibrary(name);
+    }
 }

components/module_installer/android/module.cc

+// Copyright 2019 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include <dlfcn.h>
+
+#include "base/android/bundle_utils.h"
+#include "base/android/jni_android.h"
+#include "base/android/jni_string.h"
+#include "base/logging.h"
+#include "base/strings/utf_string_conversions.h"
+#include "components/module_installer/android/jni_headers/Module_jni.h"
+
+using base::android::BundleUtils;
+
+#if defined(LOAD_FROM_BASE_LIBRARY)
+extern "C" {
+
+// These methods are forward-declared here for the build case where
+// partitioned libraries are disabled, and module code is pulled into the main
+// library. In that case, there is no current way of dlsym()'ing for this
+// JNI registration method, and hence it's referred to directly.
+// This list could be auto-generated in the future.
+extern bool JNI_OnLoad_test_dummy(JNIEnv* env);
+
+}  // extern "C"
+#endif  // LOAD_FROM_BASE_LIBRARY
+
+namespace module_installer {
+
+typedef bool JniRegistrationFunction(JNIEnv* env);
+
+static void JNI_Module_LoadNativeLibrary(
+    JNIEnv* env,
+    const base::android::JavaParamRef<jstring>& jtext) {
+  std::string library_name;
+  base::android::ConvertJavaStringToUTF8(env, jtext, &library_name);
+
+  JniRegistrationFunction* registration_function = nullptr;
+
+#if defined(LOAD_FROM_PARTITIONS) || defined(LOAD_FROM_COMPONENTS)
+#if defined(LOAD_FROM_PARTITIONS)
+  // The partition library must be opened via native code (using
+  // android_dlopen_ext() under the hood). There is no need to repeat the
+  // operation on the Java side, because JNI registration is done explicitly
+  // (hence there is no reason for the Java ClassLoader to be aware of the
+  // library, for lazy JNI registration).
+  void* library_handle =
+      BundleUtils::DlOpenModuleLibraryPartition(library_name);
+#else   // defined(LOAD_FROM_PARTITIONS)
+  const std::string lib_name = "lib" + library_name + ".cr.so";
+  void* library_handle = dlopen(lib_name.c_str(), RTLD_LOCAL);
+#endif  // defined(LOAD_FROM_PARTITIONS)
+  CHECK(library_handle != nullptr)
+      << "Could not open feature library:" << dlerror();
+
+  const std::string registration_name = "JNI_OnLoad_" + library_name;
+  // Find the module's JNI registration method from the feature library.
+  void* symbol = dlsym(library_handle, registration_name.c_str());
+  CHECK(symbol != nullptr) << "Could not find JNI registration method: "
+                           << dlerror();
+  registration_function = reinterpret_cast<JniRegistrationFunction*>(symbol);
+#else   // defined(LOAD_FROM_PARTITIONS) || defined(LOAD_FROM_COMPONENTS)
+  // TODO(https://crbug.com/870055): Similar to the declarations above, this map
+  // could be auto-generated.
+  const std::map<std::string, JniRegistrationFunction*> modules = {
+      {"test_dummy", JNI_OnLoad_test_dummy}};
+  registration_function = modules.at(library_name);
+#endif  // defined(LOAD_FROM_PARTITIONS) || defined(LOAD_FROM_COMPONENTS)
+
+  CHECK(registration_function(env))
+      << "JNI registration failed: " << library_name;
+}
+
+}  // namespace module_installer