ASM圖片監控hook glide

ASM學習思路承接上篇，對照字節碼CV asm api確實很舒服，慢慢的也能理解一些字節碼，雖然不可能一下完全喫透，但是沒關係，邊學邊搜索。畢竟對於我這種菜雞來說寫代碼就是熟能生巧的過程。

擼個經典demo監控圖片大小，這裏就以Glide爲例了。源碼分析的文章很多，直接上結論：Glide的SingleRequest中，有一個requestListeners，圖片加載成功後會遍歷這個集合，回調RequestListener.onResourceReady()。那麼思路就很簡單了，requestListeners在SingleRequest構造方法中賦值，可以在構造方法結束時插入一個自定義的RequestListener做圖片監控。

先看源碼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;
    ...
    //插入邏輯
  }

老樣子，寫個工具類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構造方法結尾插入GlideUtil.addListener(requestListeners)

說實話，我還是不熟練手寫，先借助插件ASM Bytecode Viewer生成一下吧。寫個工具類HookUtil->build->右鍵class文件使用插件。

public class HookUtil {
    private List<RequestListener> requestListeners;

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

先看字節碼，精簡一下。

  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

對應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);

話不多說，CV到MethodVisitor。

ImageClassVisitor在visitMethod中判斷是否是SingleRequest的構造方法<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構造方法結束時插入上述字節碼。

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)
            }
        }
    }
}

跑個測試用例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???報錯了，咋肥事啊，之前學習的時候搜索了一番，很多人都這麼寫，咋就空指針了捏，流下了沒有技術的淚水T.T。

好吧，斷點調試一下Gradle 調試Transform代碼，確定進入方法是SingleRequest構造方法沒錯了。那麼只有一個可能，requestListeners在構造方法中傳過來時就爲空了。找到問題了就好辦了，加個判空處理，requestListeners爲空時，初始化一個數組，然後再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節碼

  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

對應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)
            }
        }
    }
}

保險起見測試用例也設置個requestListeners回調，防止插入if語句錯誤覆蓋用戶設置的回調。

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起來，查看log

好起來了，兩個回調都走了，插樁成功。接下來在GlideUtil自定義的RequestListener中就可以做圖片監控了。

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;
    }
}

彷佛又學到了一些，彷彿又還是很菜=。=感覺還是得抽時間系統的學習下字節碼，心中有底才能穩如泰山啊。

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