base/android: replace dlopen() w/System.loadLibrary()

Because it is shorter and seems to work.

Bug: 1154224
Change-Id: I2e69ad5d016ef0e5a050613097645c66111da059
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2616158
Commit-Queue: Egor Pasko <pasko@chromium.org>
Reviewed-by: Egor Pasko <pasko@chromium.org>
Reviewed-by: Andrew Grieve <agrieve@chromium.org>
Cr-Commit-Position: refs/heads/master@{#843737}

base/android/java/src/org/chromium/base/library_loader/ModernLinker.java

@@ -40,10 +40,7 @@ class ModernLinker extends Linker {
         long loadAddress = isFixedAddressPermitted ? mBaseLoadAddress : 0;
 
         if (loadNoRelro) {
-            // Cannot use System.loadLibrary(), as the library name is transformed (adding the "lib"
-            // prefix and ".so" suffix), making the name incorrect.
-            boolean ok = nativeLoadLibraryNoRelros(libFilePath);
-            if (!ok) resetAndThrow("Cannot load without relro sharing");
+            // System.loadLibrary() below implements the fallback.
             mState = State.DONE;
         } else if (provideRelro) {
             // Create the shared RELRO, and store it.
@@ -54,7 +51,7 @@ class ModernLinker extends Linker {
                         libInfo.mLoadAddress, libInfo.mLoadSize);
             } else {
                 Log.e(TAG, "Unable to load with ModernLinker, using the system linker instead");
-                nativeLoadLibraryNoRelros(libFilePath);
+                // System.loadLibrary() below implements the fallback.
                 libInfo.mRelroFd = -1;
             }
             mLibInfo = libInfo;
@@ -94,8 +91,8 @@ class ModernLinker extends Linker {
         try {
             System.loadLibrary(library);
         } catch (UnsatisfiedLinkError e) {
-            throw new UnsatisfiedLinkError(
-                    "Unable to load the library a second time with the system linker");
+            if (loadNoRelro || provideRelro) resetAndThrow("Cannot load without relro sharing");
+            resetAndThrow("Unable to load the library a second time with the system linker");
         }
     }
 
@@ -125,7 +122,6 @@ class ModernLinker extends Linker {
         throw new UnsatisfiedLinkError(message);
     }
 
-    private static native boolean nativeLoadLibraryNoRelros(String dlopenExtPath);
     private static native boolean nativeLoadLibrary(
             String dlopenExtPath, long loadAddress, LibInfo libInfo, boolean spawnRelroRegion);
     private static native boolean nativeUseRelros(LibInfo libInfo);

base/android/linker/modern_linker_jni.cc

@@ -235,19 +235,6 @@ bool CallJniOnLoad(void* handle) {
   return true;
 }
 
-bool LoadNoSharedRelocations(const String& path) {
-  void* handle = dlopen(path.c_str(), RTLD_NOW);
-  if (!handle) {
-    LOG_ERROR("dlopen: %s", dlerror());
-    return false;
-  }
-
-  if (!CallJniOnLoad(handle))
-    return false;
-
-  return true;
-}
-
 }  // namespace
 
 void NativeLibInfo::ExportLoadInfoToJava() const {
@@ -634,15 +621,6 @@ Java_org_chromium_base_library_1loader_ModernLinker_nativeUseRelros(
   return true;
 }
 
-JNI_GENERATOR_EXPORT jboolean
-Java_org_chromium_base_library_1loader_ModernLinker_nativeLoadLibraryNoRelros(
-    JNIEnv* env,
-    jclass clazz,
-    jstring jdlopen_ext_path) {
-  String library_path(env, jdlopen_ext_path);
-  return LoadNoSharedRelocations(library_path);
-}
-
 JNI_GENERATOR_EXPORT jint
 Java_org_chromium_base_library_1loader_ModernLinker_nativeGetRelroSharingResult(
     JNIEnv* env,