test: add android demo example

Author: sanfengAndroid

demo/.gitignore

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+/build

demo/build.gradle

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+plugins {
+    id 'com.android.application'
+}
+
+android {
+    namespace 'com.sanfengandroid.demo'
+    compileSdk rootProject.targetSdk
+
+    defaultConfig {
+        minSdk 21
+        targetSdk rootProject.targetSdk
+        versionCode 100
+        versionName "1.0"
+
+        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
+        consumerProguardFiles "consumer-rules.pro"
+        externalNativeBuild {
+            cmake {
+                cppFlags ''
+            }
+        }
+    }
+
+    if (rootProject.hasSign) {
+        signingConfigs {
+            sign {
+                storeFile file(rootProject.storeFile)
+                storePassword rootProject.storePassword
+                keyAlias rootProject.keyAlias
+                keyPassword rootProject.keyPassword
+            }
+        }
+    }
+
+    buildTypes {
+        release {
+            minifyEnabled false
+            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
+        }
+    }
+    compileOptions {
+        sourceCompatibility JavaVersion.VERSION_1_8
+        targetCompatibility JavaVersion.VERSION_1_8
+    }
+    externalNativeBuild {
+        cmake {
+            path file('src/main/cpp/CMakeLists.txt')
+            version '3.22.1'
+        }
+    }
+}
+
+dependencies {
+    testImplementation 'junit:junit:4.13.2'
+    implementation(project(':library'))
+    androidTestImplementation 'androidx.test.ext:junit:1.2.1'
+    androidTestImplementation 'androidx.test.espresso:espresso-core:3.6.1'
+}

demo/consumer-rules.pro

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+# Add project specific ProGuard rules here.
+# You can control the set of applied configuration files using the
+# proguardFiles setting in build.gradle.
+#
+# For more details, see
+#   http://developer.android.com/guide/developing/tools/proguard.html
+
+# If your project uses WebView with JS, uncomment the following
+# and specify the fully qualified class name to the JavaScript interface
+# class:
+#-keepclassmembers class fqcn.of.javascript.interface.for.webview {
+#   public *;
+#}
+
+# Uncomment this to preserve the line number information for
+# debugging stack traces.
+#-keepattributes SourceFile,LineNumberTable
+
+# If you keep the line number information, uncomment this to
+# hide the original source file name.
+#-renamesourcefileattribute SourceFile

demo/proguard-rules.pro

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+package com.sanfengandroid.demo;
+
+import static org.junit.Assert.*;
+
+import android.content.Context;
+import androidx.test.ext.junit.runners.AndroidJUnit4;
+import androidx.test.platform.app.InstrumentationRegistry;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+/**
+ * Instrumented test, which will execute on an Android device.
+ *
+ * @see <a href="http://d.android.com/tools/testing">Testing documentation</a>
+ */
+@RunWith(AndroidJUnit4.class)
+public class ExampleInstrumentedTest {
+  @Test
+  public void useAppContext() {
+    // Context of the app under test.
+    Context appContext =
+        InstrumentationRegistry.getInstrumentation().getTargetContext();
+    assertEquals("com.sanfengandroid.demo.test", appContext.getPackageName());
+  }
+}

demo/src/androidTest/java/com/sanfengandroid/demo/ExampleInstrumentedTest.java

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+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android">
+
+    <application
+        android:allowBackup="true"
+        android:icon="@mipmap/ic_launcher"
+        android:label="@string/app_name"
+        android:roundIcon="@mipmap/ic_launcher_round"
+        android:supportsRtl="true"
+        android:theme="@style/Theme.FakelinkerDemo">
+        <activity
+            android:name=".MainActivity"
+            android:exported="true">
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN" />
+                <category android:name="android.intent.category.LAUNCHER" />
+            </intent-filter>
+        </activity>
+    </application>
+</manifest>

demo/src/main/AndroidManifest.xml

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+
+# For more information about using CMake with Android Studio, read the
+# documentation: https://d.android.com/studio/projects/add-native-code.html.
+# For more examples on how to use CMake, see https://github.com/android/ndk-samples.
+
+# Sets the minimum CMake version required for this project.
+cmake_minimum_required(VERSION 3.4.1)
+project("demo")
+
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+set(CMAKE_CXX_STANDARD 17)
+
+if(${CMAKE_BUILD_TYPE} STREQUAL "Debug")
+  set(FAKELINKER_LOG_LEVEL 0)
+endif()
+
+set(FAKELINKER_DIR ${CMAKE_CURRENT_SOURCE_DIR}/../../../../library/src/main/cpp)
+
+add_subdirectory(${FAKELINKER_DIR} lib)
+
+find_library(log-lib log)
+
+add_library(static_demo SHARED
+  static_demo.cpp
+)
+
+target_link_libraries(static_demo
+  PRIVATE
+  fakelinker_static
+  ${log-lib}
+)
+
+set_target_properties(static_demo PROPERTIES
+  LINK_FLAGS
+  "${LINK_FLAGS} -Wl,--gc-sections,--version-script=\"${CMAKE_CURRENT_SOURCE_DIR}/symbol.map.txt\""
+)
+
+add_library(shared_demo SHARED
+  shared_demo.cpp
+)
+
+target_link_libraries(shared_demo
+  PRIVATE
+  fakelinker
+  ${log-lib}
+)
+
+set_target_properties(shared_demo PROPERTIES
+  LINK_FLAGS
+  "${LINK_FLAGS} -Wl,--gc-sections,--version-script=\"${CMAKE_CURRENT_SOURCE_DIR}/symbol.map.txt\""
+)
+
+add_library(native_test SHARED
+  native_test.cpp
+)
+target_link_libraries(native_test PRIVATE
+  ${log-lib}
+)

demo/src/main/cpp/CMakeLists.txt

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+//
+// Created by beichen on 2025/3/12.
+//
+#include <android/log.h>
+#include <jni.h>
+#include <unistd.h>
+
+#define LOG_TAG           "NativeTest"
+
+#define LOGE(format, ...) __android_log_print(ANDROID_LOG_ERROR, LOG_TAG, format, ##__VA_ARGS__);
+
+extern "C" JNIEXPORT jint JNI_OnLoad(JavaVM *vm, void *reserved) {
+  JNIEnv *env;
+  if (vm->GetEnv(reinterpret_cast<void **>(&env), JNI_VERSION_1_6) != JNI_OK) {
+    LOGE("JNI environment error");
+    return JNI_EVERSION;
+  }
+
+  if (access("/test/hook/path", F_OK) != 0) {
+    LOGE("hook module error");
+    return JNI_ERR;
+  }
+  return JNI_VERSION_1_6;
+}

demo/src/main/cpp/native_test.cpp

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+//
+// Created by beichen on 2025/3/12.
+//
+#include <string.h>
+
+#include <alog.h>
+#include <fake_linker.h>
+#include <macros.h>
+
+static int (*orig_access)(const char *pathname, int mode) = nullptr;
+
+int g_log_level = 0;
+
+C_API API_PUBLIC int access(const char *pathname, int mode) {
+  LOGW("shared hook access function path: %s, mode: %d", pathname, mode);
+  if (strncmp(pathname, "/test/hook/path", 15) == 0) {
+    LOGW("fake access /test/hook/path");
+    return 0;
+  }
+  // Does not block other calls
+  return orig_access(pathname, mode);
+}
+
+C_API JNIEXPORT void fakelinker_module_init(JNIEnv *env, SoinfoPtr fake_soinfo, const FakeLinker *fake_linker) {
+  if (!fake_linker->is_init_success()) {
+    LOGE("fakelinker environment initialization failed, cannot continue testing");
+    return;
+  }
+  SoinfoPtr libc = fake_linker->soinfo_find(SoinfoFindType::kSTName, "libc.so", nullptr);
+  if (!libc) {
+    LOGE("fakelinker find libc soinfo failed");
+    return;
+  }
+
+  orig_access = reinterpret_cast<int (*)(const char *pathname, int mode)>(
+    fake_linker->soinfo_get_export_symbol_address(libc, "access", nullptr));
+  if (!orig_access) {
+    LOGE("fakelinker find libc symbol access failed");
+    return;
+  }
+  // Use so itself as a global library and hook all so loaded later
+  if (!fake_linker->soinfo_add_to_global(fake_soinfo)) {
+    LOGE("fakelinker add global soinfo failed");
+    return;
+  }
+  const char *loaded_libs[] = {
+    "libjavacore.so",
+  };
+  // Since libjavacore has been loaded before we load it, symbol relocation will not be triggered.
+  // At this time, manually relocate it to make the hook take effect.
+  if (!fake_linker->call_manual_relocation_by_names(fake_soinfo, 1, loaded_libs)) {
+    LOGE("relocation libjavacore.so failed");
+    return;
+  }
+  LOGW("fakelinker shared load successfully");
+}

demo/src/main/cpp/shared_demo.cpp

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+//
+// Created by beichen on 2025/3/12.
+//
+#include <string.h>
+
+#include <alog.h>
+#include <fake_linker.h>
+#include <macros.h>
+
+static int (*orig_access)(const char *pathname, int mode) = nullptr;
+
+C_API API_PUBLIC int access(const char *pathname, int mode) {
+  LOGW("static hook access function path: %s, mode: %d", pathname, mode);
+  if (strncmp(pathname, "/test/hook/path", 15) == 0) {
+    LOGW("fake access /test/hook/path");
+    return 0;
+  }
+  // Does not block other calls
+  return orig_access(pathname, mode);
+}
+
+C_API JNIEXPORT jint JNI_OnLoad(JavaVM *vm, void *reserved) {
+  JNIEnv *env;
+  if (vm->GetEnv(reinterpret_cast<void **>(&env), JNI_VERSION_1_6) != JNI_OK) {
+    LOGE("JNI environment error");
+    return JNI_EVERSION;
+  }
+  if (init_fakelinker(env,
+                      static_cast<FakeLinkerMode>(FakeLinkerMode::kFMSoinfo | FakeLinkerMode::kFMNativeHook |
+                                                  FakeLinkerMode::kFMJavaRegister),
+                      nullptr) != 0) {
+    LOGE("fakelinker environment error");
+    return JNI_ERR;
+  }
+
+  const FakeLinker *fake_linker = get_fakelinker();
+
+  SoinfoPtr libc = fake_linker->soinfo_find(SoinfoFindType::kSTName, "libc.so", nullptr);
+  if (!libc) {
+    LOGE("fakelinker find libc soinfo failed");
+    return JNI_ERR;
+  }
+
+  orig_access = reinterpret_cast<int (*)(const char *pathname, int mode)>(
+    fake_linker->soinfo_get_export_symbol_address(libc, "access", nullptr));
+  if (!orig_access) {
+    LOGE("fakelinker find libc symbol access failed");
+    return JNI_ERR;
+  }
+
+  SoinfoPtr fake_soinfo = fake_linker->soinfo_find(SoinfoFindType::kSTAddress, nullptr, nullptr);
+  if (fake_soinfo == nullptr) {
+    LOGE("find self soinfo failed");
+    return JNI_ERR;
+  }
+
+  // Use so itself as a global library and hook all so loaded later
+  if (!fake_linker->soinfo_add_to_global(fake_soinfo)) {
+    LOGE("fakelinker add global soinfo failed");
+    return JNI_ERR;
+  }
+  const char *loaded_libs[] = {
+    "libjavacore.so",
+  };
+  // Since libjavacore has been loaded before we load it, symbol relocation will not be triggered.
+  // At this time, manually relocate it to make the hook take effect.
+  if (!fake_linker->call_manual_relocation_by_names(fake_soinfo, 1, loaded_libs)) {
+    LOGE("relocation libjavacore.so failed");
+    return JNI_ERR;
+  }
+  LOGW("fakelinker static load successfully");
+  return JNI_VERSION_1_6;
+}