ServiceManager的启动

启动进程
启动Binder机制
发布自己的服务
等待并响应请求

启动配置文件：init.rc

service servicemenager /system/bin/servicemanager  class core  user system  group system  critical

入口函数：frameworks\native\cmds\servicemanager\service_manager.c::main

int main(int argc, char **argv){  struct binder_state *bs;  //打开binder驱动  bs = binder_open(128*1024);  //把自己注册成上下文管理者  binder_become_context_manager(bs);  //进入loop循环，等待并响应请求  binder_loop(bs, svcmgr_handler);  return 0;}

打开binder驱动：frameworks\native\cmds\servicemanager\binder.c::binder_open

struct binder_state *binder_open(size_t mapsize){  struct binder_state *bs;  bs = malloc(sizeof(*bs));  //打开binder驱动  bs->fd = open("/dev/binder", O_RDWR);  bs->mapsize = mapsize;  //用mmap把bs->fd映射到一块内存  bs->mapped = mmap(NULL, mapsize, PROT_READ, MAP_PRIVATE, bs->fd, 0);  return bs;}

把自己注册成上下文管理者:
frameworks\native\cmds\servicemanager\binder.c::binder_become_context_manager

int binder_become_context_manager(struct binder_state *bs){  return ioctl(bs->fd, BINDER_SET_CONTEXT_MGR, 0);}

这个函数的意思是：告诉binder驱动：管理者已经就绪了。

frameworks\native\cmds\servicemanager\binder.c::binder_become_context_manager

void binder_loop(struct binder_state *bs, binder_handler func){  uint32_t readbuff[32];  //告诉驱动：当前线程是处理binder请求的线程  readbuff[0] = BC_ENTER_LOOPER;  binder_write(bs, readbuff, sizeof(uint32_t));    for(;;){    bwr.read_size = sizeof(readbuf);    bwr.read_buffer = (uintptr_t)readbuff;    ioctl(bs->fd, BINDER_WRITE_READ, &bwr);    binder_parse(bs, 0, (uintptr_t)readbuf, bwr.read_consumed, func);  }}int binder_write(struct binder_state *bs, void *data, size_t len){  struct binder_write_read bwr;  bwr.write_size = len;  bwr.write_consumed = 0;  bwr.write_buffer = (uintptr_t)data;  bwr.read_size = 0;  res = ioctl(bs->fd, BINDER_WRITE_READ, &bwr);  return res;}

如何获取ServiceManager?

如SurfaceFlinger的启动：
frameworks\native\services\surfaceflinger\main_surfaceflinger.cpp::main

int main(int, char**){  sp<ProcessState> ps(ProcessState::self());  ps->startThreadPool();  sp<SuffaceFlinger> flinger = new SurfaceFlinger();  flinger->init();  sp<IServiceManager> sm(defaultServiceManager());  //P1  sm->addService(String16(SurfaceFlinger::getServiceManagerName()), flinger, false);  flinger->run();  return 0;}

P1展开：
frameworks\native\libs\binder\IServiceManager.cpp::defaultServiceManager

sp<IServiceManager> defaultServiceManager(){  if (gDefaultServiceManager != NULL) return gDefaultServiceManager;  {    AutoMutex _l(gDefaultServiceManagerLock);    while (gDefaultServiceManager == NULL) {      gDefaultServiceManager = interface_cast<IServiceManager>(        //P2        ProcessState::self()->getContextObject(NULL));      if (gDefaultServiceManager == NULL)        sleep(1);    }  }  return gDefaultServiceManager;}

P2展开：
frameworks\native\libs\binder\ProcessState.cpp::getContextObject

sp<IBinder> ProcessState::getContextObject(const sp<IBinder>& /*caller*/){    return getStrongProxyForHandle(0);}sp<IBinder> ProcessState::getStrongProxyForHandle(int32_t handle){  handle_entry* e = lookupHandleLocked(handle);  IBinder* b = e->binder;  if(b == NULL){    b = new BpBinder(handle);    e->binder = b;  }  return b}

怎么添加Service?

frameworks\native\libs\binder\IServiceManager.cpp::addService

status_t addService(const String16& name, const sp<IBinder>& service, bool allowIsolated){  ……  status_t err = remote()->transact(ADD_SERVICE_TRANSACTION, data, &reply);}

frameworks\native\libs\binder\BpBinder.cpp::transact

status_t BpBinder::transact(uint32_t code, const Parcel& data, Parcel* reply, uint32_t flags){  //IPCThreadState是线程的单例，负责跟binder驱动交互  IPCThreadState::self()->transact(mHandle, code, data, reply, flags);}

ServiceManager是怎么处理请求的：

int svcmgr_handler(struct binder_state *bs, struct binder_transaction_data *txn,...){  switch(txn->code) {    ……    case SVC_MGR_ADD_SERVICE:      ……      do_add_service(bs, s, len, handle, ...)      break;  }  ……}

怎么获取Service?

frameworks\base\core\java\android\os\ServiceManager.java::getService

public static IBinder getService(String name){  IBinder service = sCache.get(name);  if(service != null){    return service;  }else{    return getIServiceManager().getServcie(name);  }  return null;}

ServiceManager是怎么处理请求的：
frameworks\native\cmds\servicemanager\service_manager.c

int svcmgr_handler(struct binder_state *bs, struct binder_transaction_data *txn,...){  uint32_t handle  switch(txn->code) {    ……    case SVC_MGR_GET_SERVICE:      s = bio_get_string16(msg, &len);      handle = do_find_service(bs, s, len, ...);      bio_put_ref(reply, handle);      return 0;  }  ……}

总结

ServiceManager启动流程是怎样的？
a)启动进程;
b)启动binder机制（打开binder驱动，映射内存，注册binder线程）;
c)向binder驱动注册（成为管理者）；
d)进入loop循环（等待并处理请求）
怎么获取ServiceManager的binder对象
a)根据0号binder用了一个BpBinder
怎么向ServiceManager添加服务？
a)首先获取ServiceManager的binder对象；
b)然后发起一个addService的binder调用；(参数：服务名称、binder服务对象)
怎么从ServiceManager获取服务？
a)首先获取ServiceManager的binder对象；
b)然后发起一个getService的binder调用；(参数：服务名称)

【Android话题-2.5系统服务】ServiceManager启动和工作原理是怎样的

ServiceManager的启动

如何获取ServiceManager?

怎么添加Service?

怎么获取Service?

总结

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