Binder（四）system_server中binder的初始化

最新推荐文章于 2025-10-24 15:25:40 发布

原创

最新推荐文章于 2025-10-24 15:25:40 发布 · 1k 阅读

0 ·

CC 4.0 BY-SA版权

文章标签：

#android #android studio #java

本文详细解析了Android系统中System Server的启动过程，从Zygote进程出发，通过forkSystemServer方法创建System Server进程，深入探讨了Java层和Native层的关键步骤。

本文基于Android_9.0、kernel_3.18源码

引言

由Zygote进程简介，我们知道android进程之间的关系；system_server是由zygote进程fork出来的，那它中间是怎样操作的呢？

Binder（四）system_server中binder的初始化

frameworks/base/cmds/app_process/app_main.cpp
frameworks/base/core/java/com/android/internal/os/ZygoteInit.java
frameworks/base/core/java/com/android/internal/os/Zygote.java
frameworks/base/core/jni/com_android_internal_os_Zygote.cpp
frameworks/base/core/java/com/android/internal/os/ZygoteConnection.java
frameworks/base/core/jni/AndroidRuntime.cpp
frameworks/native/libs/binder/ProcessState.cpp
frameworks/native/libs/binder/IPCThreadState.cpp
frameworks/native/include/binder/IPCThreadState.h

system_server进程创建过程

1、app_main.cpp->main()

int main(int argc, char* const argv[]){
    ........
    AppRuntime runtime(argv[0], computeArgBlockSize(argc, argv));
    ........
    if (zygote) {
        // 拉起com.android.internal.os.ZygoteInit.java
        runtime.start("com.android.internal.os.ZygoteInit", args, zygote);
    } else if (className) {} else {}
}

在app_main.cpp->main()方法中，通过runtime.start()拉起ZygoteInit.java；AppRuntime是AndroidRuntime的子类，start方法会开启虚拟机，并且调用className的main方法。

// 开启Android虚拟机， 并调用className的main方法
void AndroidRuntime::start(const char* className, const Vector<String8>& options, bool zygote){}

2、ZygoteInit.java->main()

public static void main(String argv[]) {
    ZygoteServer zygoteServer = new ZygoteServer();
    ........
    // 注册socket
    zygoteServer.registerServerSocketFromEnv(socketName);
    ........
    // In some configurations, we avoid preloading resources and classes eagerly.
    // In such cases, we will preload things prior to our first fork.
    if (!enableLazyPreload) {
        bootTimingsTraceLog.traceBegin("ZygotePreload");
        EventLog.writeEvent(LOG_BOOT_PROGRESS_PRELOAD_START,
            SystemClock.uptimeMillis());
        // 预加载资源
        preload(bootTimingsTraceLog);
        EventLog.writeEvent(LOG_BOOT_PROGRESS_PRELOAD_END,
            SystemClock.uptimeMillis());
        bootTimingsTraceLog.traceEnd(); // ZygotePreload
    } else {
        Zygote.resetNicePriority();
    }
    ........
    if (startSystemServer) {
        // 启动system_server
        Runnable r = forkSystemServer(abiList, socketName, zygoteServer);
        // {@code r == null} in the parent (zygote) process, and {@code r != null} in the
        // child (system_server) process.
        if (r != null) {
            r.run();
            return;
        }
    }
    ....