Avoid hardcoding ART struct layout

Author: yujincheng08

library/src/main/java/org/lsposed/hiddenapibypass/HiddenApiBypass.java

@@ -26,6 +26,7 @@
 
 import org.lsposed.hiddenapibypass.library.BuildConfig;
 
+import java.io.File;
 import java.lang.invoke.MethodHandle;
 import java.lang.invoke.MethodHandles;
 import java.lang.reflect.Constructor;
@@ -41,9 +42,24 @@
 import java.util.Set;
 import java.util.stream.Collectors;
 
+import dalvik.system.PathClassLoader;
 import dalvik.system.VMRuntime;
 import sun.misc.Unsafe;
 
+class ChildFirstClassLoader extends PathClassLoader {
+    public ChildFirstClassLoader(String dexPath, ClassLoader parent) {
+        super(dexPath, parent);
+    }
+
+    @Override
+    public Class<?> loadClass(String name) throws ClassNotFoundException {
+        if ("java.lang.Object".equals(name)) {
+            return Object.class;
+        }
+        return findClass(name);
+    }
+}
+
 @RequiresApi(Build.VERSION_CODES.P)
 public final class HiddenApiBypass {
     private static final String TAG = "HiddenApiBypass";
@@ -65,12 +81,21 @@ public final class HiddenApiBypass {
             //noinspection JavaReflectionMemberAccess DiscouragedPrivateApi
             unsafe = (Unsafe) Unsafe.class.getDeclaredMethod("getUnsafe").invoke(null);
             assert unsafe != null;
-            methodOffset = unsafe.objectFieldOffset(Helper.Executable.class.getDeclaredField("artMethod"));
-            classOffset = unsafe.objectFieldOffset(Helper.Executable.class.getDeclaredField("declaringClass"));
-            artOffset = unsafe.objectFieldOffset(Helper.MethodHandle.class.getDeclaredField("artFieldOrMethod"));
-            methodsOffset = unsafe.objectFieldOffset(Helper.Class.class.getDeclaredField("methods"));
-            iFieldOffset = unsafe.objectFieldOffset(Helper.Class.class.getDeclaredField("iFields"));
-            sFieldOffset = unsafe.objectFieldOffset(Helper.Class.class.getDeclaredField("sFields"));
+            ClassLoader bootClassloader = null;
+            try {
+                if (new File("/apex/com.android.art/javalib/core-oj.jar").exists()) {
+                    bootClassloader = new ChildFirstClassLoader("/apex/com.android.art/javalib/core-oj.jar", null);
+                } else if (new File("/apex/com.android.runtime/javalib/core-oj.jar").exists()) {
+                    bootClassloader = new ChildFirstClassLoader("/apex/com.android.runtime/javalib/core-oj.jar", null);
+                }
+            } catch (Throwable ignored) {
+            }
+            methodOffset = unsafe.objectFieldOffset((bootClassloader != null ? bootClassloader.loadClass(Executable.class.getName()) : Helper.Executable.class).getDeclaredField("artMethod"));
+            classOffset = unsafe.objectFieldOffset((bootClassloader != null ? bootClassloader.loadClass(Executable.class.getName()) : Helper.Executable.class).getDeclaredField("declaringClass"));
+            artOffset = unsafe.objectFieldOffset((bootClassloader != null ? bootClassloader.loadClass(MethodHandle.class.getName()) : Helper.MethodHandle.class).getDeclaredField("artFieldOrMethod"));
+            methodsOffset = unsafe.objectFieldOffset((bootClassloader != null ? bootClassloader.loadClass(Class.class.getName()) : Helper.Class.class).getDeclaredField("methods"));
+            iFieldOffset = unsafe.objectFieldOffset((bootClassloader != null ? bootClassloader.loadClass(Class.class.getName()) : Helper.Class.class).getDeclaredField("iFields"));
+            sFieldOffset = unsafe.objectFieldOffset((bootClassloader != null ? bootClassloader.loadClass(Class.class.getName()) : Helper.Class.class).getDeclaredField("sFields"));
             Method mA = Helper.NeverCall.class.getDeclaredMethod("a");
             Method mB = Helper.NeverCall.class.getDeclaredMethod("b");
             mA.setAccessible(true);
@@ -233,7 +258,7 @@ public static List<Executable> getDeclaredMethods(@NonNull Class<?> clazz) {
      * @param parameterTypes argument types of the expected method with name {@code methodName}
      * @return the found method
      * @throws NoSuchMethodException when no method matches the given parameters
-     * @see Class#getDeclaredMethod(String, Class[]) 
+     * @see Class#getDeclaredMethod(String, Class[])
      */
     @NonNull
     public static Method getDeclaredMethod(@NonNull Class<?> clazz, @NonNull String methodName, @NonNull Class<?>... parameterTypes) throws NoSuchMethodException {