ASM图片监控hook glide

ASM学习思路承接上篇，对照字节码CV asm api确实很舒服，慢慢的也能理解一些字节码，虽然不可能一下完全吃透，但是没关系，边学边搜索。毕竟对于我这种菜鸡来说写代码就是熟能生巧的过程。

撸个经典demo监控图片大小，这里就以Glide为例了。源码分析的文章很多，直接上结论：Glide的SingleRequest中，有一个requestListeners，图片加载成功后会遍历这个集合，回调RequestListener.onResourceReady()。那么思路就很简单了，requestListeners在SingleRequest构造方法中赋值，可以在构造方法结束时插入一个自定义的RequestListener做图片监控。

先看源码SingleRequest

  private SingleRequest(
      Context context,
      GlideContext glideContext,
      @NonNull Object requestLock,
      @Nullable Object model,
      Class<R> transcodeClass,
      BaseRequestOptions<?> requestOptions,
      int overrideWidth,
      int overrideHeight,
      Priority priority,
      Target<R> target,
      @Nullable RequestListener<R> targetListener,
      @Nullable List<RequestListener<R>> requestListeners,
      RequestCoordinator requestCoordinator,
      Engine engine,
      TransitionFactory<? super R> animationFactory,
      Executor callbackExecutor) {
    ...
    this.requestListeners = requestListeners;
    ...
    //插入逻辑
  }

老样子，写个工具类GlideUtil

public class GlideUtil {

    public static List addListener(List<RequestListener> requestListeners) {
        requestListeners.add(new RequestListener() {
            @Override
            public boolean onLoadFailed(@Nullable GlideException e, Object model, Target target, boolean isFirstResource) {
                return false;
            }

            @Override
            public boolean onResourceReady(Object resource, Object model, Target target, DataSource dataSource, boolean isFirstResource) {
                Log.d("chenxuan----->", "GlideHook");
                return false;
            }
        });
        return requestListeners;
    }
}

只需在SingleRequest构造方法结尾插入GlideUtil.addListener(requestListeners)

说实话，我还是不熟练手写，先借助插件ASM Bytecode Viewer生成一下吧。写个工具类HookUtil->build->右键class文件使用插件。

public class HookUtil {
    private List<RequestListener> requestListeners;

    private void hook() {
        GlideUtil.addListener(requestListeners);
    }
}
HookUtil.class

先看字节码，精简一下。

  private hook()V
   L0
    ALOAD 0
    GETFIELD com/chenxuan/hook/HookUtil.requestListeners : Ljava/util/List;
    INVOKESTATIC com/chenxuan/hook/GlideUtil.addListener (Ljava/util/List;)Ljava/util/List;
    POP

对应asm api

            methodVisitor.visitVarInsn(ALOAD, 0);
            methodVisitor.visitFieldInsn(GETFIELD, "com/chenxuan/hook/HookUtil", "requestListeners", "Ljava/util/List;");
            methodVisitor.visitMethodInsn(INVOKESTATIC, "com/chenxuan/hook/GlideUtil", "addListener", "(Ljava/util/List;)Ljava/util/List;", false);
            methodVisitor.visitInsn(POP);

话不多说，CV到MethodVisitor。

ImageClassVisitor在visitMethod中判断是否是SingleRequest的构造方法<init>。

class ImageClassVisitor(classVisitor: ClassVisitor) : ClassVisitor(Opcodes.ASM9, classVisitor) {
    private var target: String? = null

    override fun visit(
        version: Int,
        access: Int,
        name: String?,
        signature: String?,
        superName: String?,
        interfaces: Array<out String>?
    ) {
        target = name
        super.visit(version, access, name, signature, superName, interfaces)
    }

    override fun visitMethod(
        access: Int,
        name: String?,
        descriptor: String?,
        signature: String?,
        exceptions: Array<out String>?
    ): MethodVisitor {
        val mv = cv.visitMethod(access, name, descriptor, signature, exceptions)
        if (target == "com/bumptech/glide/request/SingleRequest" && name == "<init>" && descriptor != null) {
            return ImageMethodVisitor(mv, access, name, descriptor)
        }
        return mv
    }
}

ImageMethodVisitor在SingleRequest构造方法结束时插入上述字节码。

object ImageMethodVisitor {

    operator fun invoke(
        mv: MethodVisitor,
        access: Int,
        name: String?,
        descriptor: String?,
    ): MethodVisitor {
        return object : AdviceAdapter(Opcodes.ASM9, mv, access, name, descriptor) {

            override fun onMethodExit(opcode: Int) {
                mv.visitVarInsn(ALOAD, 0)
                mv.visitFieldInsn(
                    GETFIELD,
                    "com/bumptech/glide/request/SingleRequest",
                    "requestListeners",
                    "Ljava/util/List;"
                )
                mv.visitMethodInsn(
                    INVOKESTATIC,
                    "com/chenxuan/hook/GlideUtil",
                    "addListener",
                    "(Ljava/util/List;)Ljava/util/List;",
                    false
                )
                mv.visitInsn(POP)
                super.onMethodExit(opcode)
            }
        }
    }
}

跑个测试用例MainActivity

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        Glide
            .with(this)
            .load("https://pic.3gbizhi.com/2014/0430/20140430043839656.jpg")
            .into(findViewById(R.id.ivAvatar))
    }
}

wtf???报错了，咋肥事啊，之前学习的时候搜索了一番，很多人都这么写，咋就空指针了捏，流下了没有技术的泪水T.T。

NullPointerException

好吧，断点调试一下Gradle 调试Transform代码，确定进入方法是SingleRequest构造方法没错了。那么只有一个可能，requestListeners在构造方法中传过来时就为空了。找到问题了就好办了，加个判空处理，requestListeners为空时，初始化一个数组，然后再addListener。

修改HookUtil

public class HookUtil {
    private List<RequestListener> requestListeners;

    private void hook() {
        if (requestListeners == null) requestListeners = new ArrayList<>();
        GlideUtil.addListener(requestListeners);
    }
}

再看一下插件生成的字节码

  private hook()V
   L0
    ALOAD 0
    GETFIELD com/chenxuan/hook/HookUtil.requestListeners : Ljava/util/List;
    IFNONNULL L1
    ALOAD 0
    NEW java/util/ArrayList
    DUP
    INVOKESPECIAL java/util/ArrayList.<init> ()V
    PUTFIELD com/chenxuan/hook/HookUtil.requestListeners : Ljava/util/List;
   L1

   FRAME SAME
    ALOAD 0
    GETFIELD com/chenxuan/hook/HookUtil.requestListeners : Ljava/util/List;
    INVOKESTATIC com/chenxuan/hook/GlideUtil.addListener (Ljava/util/List;)Ljava/util/List;
    POP

对应asm api

            methodVisitor.visitVarInsn(ALOAD, 0);
            methodVisitor.visitFieldInsn(GETFIELD, "com/chenxuan/hook/HookUtil", "requestListeners", "Ljava/util/List;");
            Label label1 = new Label();
            methodVisitor.visitJumpInsn(IFNONNULL, label1);
            methodVisitor.visitVarInsn(ALOAD, 0);
            methodVisitor.visitTypeInsn(NEW, "java/util/ArrayList");
            methodVisitor.visitInsn(DUP);
            methodVisitor.visitMethodInsn(INVOKESPECIAL, "java/util/ArrayList", "<init>", "()V", false);
            methodVisitor.visitFieldInsn(PUTFIELD, "com/chenxuan/hook/HookUtil", "requestListeners", "Ljava/util/List;");
            methodVisitor.visitLabel(label1);
            methodVisitor.visitFrame(Opcodes.F_SAME, 0, null, 0, null);
            methodVisitor.visitVarInsn(ALOAD, 0);
            methodVisitor.visitFieldInsn(GETFIELD, "com/chenxuan/hook/HookUtil", "requestListeners", "Ljava/util/List;");
            methodVisitor.visitMethodInsn(INVOKESTATIC, "com/chenxuan/hook/GlideUtil", "addListener", "(Ljava/util/List;)Ljava/util/List;", false);
            methodVisitor.visitInsn(POP);

CV到ImageMethodVisitor

object ImageMethodVisitor {

    operator fun invoke(
        mv: MethodVisitor,
        access: Int,
        name: String?,
        descriptor: String?,
    ): MethodVisitor {
        return object : AdviceAdapter(Opcodes.ASM9, mv, access, name, descriptor) {

            override fun onMethodExit(opcode: Int) {
                mv.visitVarInsn(ALOAD, 0)
                mv.visitFieldInsn(
                    GETFIELD,
                    "com/bumptech/glide/request/SingleRequest",
                    "requestListeners",
                    "Ljava/util/List;"
                )
                val label1 = Label()
                mv.visitJumpInsn(IFNONNULL, label1)
                mv.visitVarInsn(ALOAD, 0)
                mv.visitTypeInsn(NEW, "java/util/ArrayList")
                mv.visitInsn(DUP)
                mv.visitMethodInsn(
                    INVOKESPECIAL,
                    "java/util/ArrayList",
                    "<init>",
                    "()V",
                    false
                )
                mv.visitFieldInsn(
                    PUTFIELD,
                    "com/bumptech/glide/request/SingleRequest",
                    "requestListeners",
                    "Ljava/util/List;"
                )
                mv.visitLabel(label1)
                mv.visitFrame(F_SAME, 0, null, 0, null)
                mv.visitVarInsn(ALOAD, 0)
                mv.visitFieldInsn(
                    GETFIELD,
                    "com/bumptech/glide/request/SingleRequest",
                    "requestListeners",
                    "Ljava/util/List;"
                )
                mv.visitMethodInsn(
                    INVOKESTATIC,
                    "com/chenxuan/hook/GlideUtil",
                    "addListener",
                    "(Ljava/util/List;)Ljava/util/List;",
                    false
                )
                mv.visitInsn(POP)
                super.onMethodExit(opcode)
            }
        }
    }
}

保险起见测试用例也设置个requestListeners回调，防止插入if语句错误覆盖用户设置的回调。

override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        Glide
            .with(this)
            .load("https://pic.3gbizhi.com/2014/0430/20140430043839656.jpg")
            .listener(object : RequestListener<Drawable> {
                override fun onResourceReady(
                    resource: Drawable?,
                    model: Any?,
                    target: Target<Drawable>?,
                    dataSource: DataSource?,
                    isFirstResource: Boolean
                ): Boolean {
                    Log.d("chenxuan----->", "onResourceReady")
                    return false
                }

                override fun onLoadFailed(
                    e: GlideException?,
                    model: Any?,
                    target: Target<Drawable>?,
                    isFirstResource: Boolean
                ): Boolean {
                    return false
                }

            })
            .into(findViewById(R.id.ivAvatar))
    }

run起来，查看log


log

好起来了，两个回调都走了，插桩成功。接下来在GlideUtil自定义的RequestListener中就可以做图片监控了。

public class GlideUtil {

    public static List addListener(List<RequestListener> requestListeners) {
        requestListeners.add(new RequestListener() {
            @Override
            public boolean onLoadFailed(@Nullable GlideException e, Object model, Target target, boolean isFirstResource) {
                return false;
            }

            @Override
            public boolean onResourceReady(Object resource, Object model, Target target, DataSource dataSource, boolean isFirstResource) {
                if (resource instanceof BitmapDrawable) {
                    ((BitmapDrawable) resource).getBitmap();
                }
                return false;
            }
        });
        return requestListeners;
    }
}

彷佛又学到了一些，仿佛又还是很菜=。=感觉还是得抽时间系统的学习下字节码，心中有底才能稳如泰山啊。

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