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Android系统10 RK3399 init进程启动(四十三) ROM定制开机自启动服务(C++程序)


配套系列教学视频链接:

      ​​安卓系列教程之ROM系统开发-百问100ask​​

说明

系统:Android10.0

设备: FireFly RK3399 (ROC-RK3399-PC-PLUS)

前言

Android init启动的rc脚本中包含了很多后台服务(service),这些服务负责不同功能, 比如netd负责网络管理, rild负责无线通信, installd负责app的安装等。在实际的系统ROM定制开发中, 我们需要定制化自己服务,本章节重点介绍如何编写一个Native服务,并完成开机自启动。

一, 需求

  1. 创造一个开机启动守护进程, 模仿init进程中建立epoll机制,可循环监听各种事件,如网络链接和数据处理,各种信号处理,文件的数据处理等。
  2. 本例主要建立模型, 只监听一个本地套接字,通过epoll监听套接字上的链接和数据。 后期需要监控其他事件,直接进行扩展即可。

二, 服务程序内容

用传统的epoll编程大体如下步骤:

#include <sys/epoll.h>
//创建一个epoll句柄
int epoll_create(int size);
//利用epoll_ctl在epoll例程内注册监视对象文件描述符。
int epoll_ctl(int epfd, int op, int fd, struct epoll_event* event);
//等待事件的产生
int epoll_wait(int epfd, struct epoll_event* events, int maxevents, int timeout);
//关闭epoll
int close(int fd);

编程例子(伪代码):

//创建一个epoll句柄
int epfd = epoll_create(EPOLL_SIZE);

//将需要监控的fd加入监控
int serv_sock = socket(PF_INET, SOCK_STREAM, 0);
struct epoll_event event;
event.events = EPOLLIN;
event.data.fd = serv_sock;
epoll_ctl(epfd, EPOLL_CTL_ADD, serv_sock, &event);

//开始监控
struct epoll_event * ep_events = malloc(sizeof(struct epoll_event) * EPOLL_SIZE);
while (1)
{
event_cnt = epoll_wait(epfd, ep_events, EPOLL_SIZE, -1);

if (ep_events[i].data.fd == serv_sock)
{
xxx
}
}

 而Android 的init代码中通过面向对象,封装了epoll, 用起来简单方便,扩展性好,代码路径在:

system/core/init/epoll.cpp

epoll.cpp, epoll.h, result.h都直接拷贝自system/core/init)

device/rockchip/qh100_rk3399/test_se/myservice/

├── Android.bp

├── client_main.cpp

├── epoll.cpp

├── epoll.h

├── main.cpp

├── myservice.rc

└── result.h

此处我主要列出守护进程主程序main.cpp:

#include <string.h>
#include <errno.h>
#include <sys/un.h>
#include <sys/types.h> /* See NOTES */
#include <sys/socket.h>
#include <sys/un.h>
#include <sys/types.h> /* See NOTES */
#include <sys/socket.h>

#include "result.h"
#include "epoll.h"
#include <cutils/sockets.h>


#define LOG_TAG "mysrv_test"
//#include <android/log.h>
#include <string.h>
#include <errno.h>
#include <sys/un.h>
#include <sys/types.h> /* See NOTES */
#include <sys/socket.h>
#include <sys/un.h>
#include <sys/types.h> /* See NOTES */
#include <sys/socket.h>

#include "result.h"
#include "epoll.h"
#include <cutils/sockets.h>


#define LOG_TAG "mysrv_test"
//#include <android/log.h>
#include <log/log.h>

using namespace android::init;

#define SOCKET_NAME_TEST "mysock"
static int s_fdListen = -1;

void handle_socket_fd()
{
int ret = -1;
int new_fd = -1;
char cmd[256];

if(s_fdListen > 0){
new_fd = accept(s_fdListen, nullptr, nullptr);
if (new_fd < 0) {
return;
}
bzero(cmd, sizeof(cmd));
ret = recv(new_fd, cmd, 256, 0);
if(ret < 0){
ALOGE("recv socket error : %s ", strerror(errno));
return;
}
cmd[ret] = '\0';
}

ALOGE("recv client cmd: %s \n",cmd);
close(new_fd);

}

void setup_socket(Epoll* epoll)
{
//s_fdListen = android_get_control_socket(SOCKET_NAME_TEST);
s_fdListen = socket(AF_LOCAL, SOCK_STREAM, 0);
if (s_fdListen < 0) {
ALOGE("get control socket error, name : %s", SOCKET_NAME_TEST);
exit(-1);
}
std::string path = "/dev/socket/mysocket" ;
unlink(path.c_str());

struct sockaddr_un addr;
addr.sun_family = AF_LOCAL;
strlcpy(addr.sun_path, path.c_str(), sizeof(addr.sun_path));
bind(s_fdListen, (const struct sockaddr *)&addr, sizeof(addr));

listen(s_fdListen, 4);

if (auto result = epoll->RegisterHandler(s_fdListen, handle_socket_fd); !result) {
ALOGE("epoll RegisterHandler error: %s", result.error().error_string.c_str());
exit(1);
}
}


int main(int argc, char *argv[])
{
//初始化epoll
Epoll epoll;
if (auto result = epoll.Open(); !result) {
ALOGE("epoll Open error: %s", result.error().error_string.c_str());
exit(1);
}

setup_socket(&epoll);
while(true){
auto epoll_timeout = std::optional<std::chrono::milliseconds>{};
if (auto result = epoll.Wait(epoll_timeout); !result) {
ALOGE("epoll Wait error: %s", result.error().error_string.c_str());
}
}

return 0;
}

 客户端测试程序client_main.cpp:

#include <fcntl.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>

#include <string.h>
#include <errno.h>
#include <sys/un.h>
#include <sys/socket.h>

#define LOG_TAG "mysrv_test"
#include <log/log.h>

#define SOCKET_NAME_TEST "mysock"

int main(int argc, char *argv[])
{
int fd = -1;
int ret = -1;

fd = socket(AF_LOCAL, SOCK_STREAM, 0);
if(fd < 0){
ALOGE("socket error: %s", strerror(errno));
exit(1);
}

struct sockaddr_un srv_addr;
srv_addr.sun_family = AF_LOCAL;
strlcpy(srv_addr.sun_path, "/dev/socket/mysocket", sizeof(srv_addr.sun_path));
ret = connect(fd, (struct sockaddr *)&srv_addr, sizeof(srv_addr));
if(ret < 0){
ALOGE("connect error: %s", strerror(errno));
exit(1);
}

char content[256];
snprintf(content, 256, "hello from client pid = %d", getpid());
ret = write(fd, content, 256);
if(ret < 0){
ALOGE("write error: %s", strerror(errno));
exit(1);
}

close(fd);

return 0;
}

对应编译规则(包含客户端测试程序):

cc_binary {

    name: "myservice",

    init_rc: ["myservice.rc"],


    srcs: [

                "main.cpp",

                "epoll.cpp"

        ],


    shared_libs: [

        "liblog",

        "libcutils",

        "libbase",

    ],


   proprietary: true,

    cflags: [

                "-Werror",

                "-Wno-unused-parameter"

        ],

}

cc_binary {

    name: "myclient_main",


    srcs: [

                "client_main.cpp",

        ],


    shared_libs: [

        "liblog",

        "libcutils",

        "libbase",

    ],


    cflags: [

                "-Werror",

                "-Wno-unused-parameter"

        ],

    proprietary: true,

}

 通过编译:

source FFTools/build.sh

lunch qh100_rk3399-userdebug

mmm device/rockchip/qh100_rk3399/test_se/myservice/

最后生成:

out/target/product/qh100_rk3399/vendor/bin/myservice

out/target/product/qh100_rk3399/vendor/bin/myclient_main

通过adb将两个程序push到开发版/vendor/bin进行运行验证代码逻辑是否有问题

 三,开机启动定制

1, 定义rc文件

device/rockchip/qh100_rk3399/test_se/myservice/myservice.rc

service mynativeservice /vendor/bin/myservice

    class main

    user root

    group root system log

2, Android.bp定义规则

Android.bp中init_rc用于指定当前模块编译的同时需要将rc文件也编译进系统:

cc_binary {

    name: "myservice",

   init_rc: ["myservice.rc"],

   //省略xxx

   proprietary: true,

}

3,编译生成

out/target/product/qh100_rk3399/vendor/vendor/etc/init/myservice.rc

4, 通过adb将rc文件push到开发版/vendor/etc/init, 开机重启测试是否启动:

adb root

adb remount

adb push .\myclient_main  /vendor/bin

adb push .\myservice  /vendor/bin

adb push .\myservice.rc /vendor/etc/init/

四, 配置selinux规则

 以上操作暂时还无法完成开机启动,需要配置selinux规则,没有规则,init在启动子进程的时候无法切换到指定的进程域中去。

device/rockchip/qh100_rk3399/test_se/sepolicy/myservice.te

# subject context in proccess status

type  myservice_dt, domain;


# object context as a file

type myservice_dt_exec, exec_type, vendor_file_type, file_type;


#grant perm as domain

init_daemon_domain(myservice_dt)

device/rockchip/qh100_rk3399/test_se/sepolicy/file_contexts

/dev/myse_dev    u:object_r:myse_testdev_t:s0


/vendor/bin/myse_test                   u:object_r:myse_test_dt_exec:s0


/vendor/bin/prop_test                   u:object_r:myprop_test_dt_exec:s0


/vendor/bin/myservice                   u:object_r:myservice_dt_exec:s0


编译:

make selinux_policy -j2 

更新开发板验证:按照我们之前的教程:​​Android系统10 RK3399 init进程启动(三十二) SeAndroid实战之策略更新和验证_旗浩替换 vendor和odm分区中的selinux目录文件,然后重启开发板查看:

 qh100_rk3399:/ $ ps -elf | grep my

root           338     1 0 15:06:41 ?     00:00:00 myservice

shell         2080  2074 8 15:12:01 pts/0 00:00:00 grep my

qh100_rk3399:/ $ getprop | grep my

[init.svc.mynativeservice]: [running]

[ro.boottime.mynativeservice]: [4325580126]

qh100_rk3399:/ $ su

:/ #  kill -9 338    //杀死进程

:/ # ps -elf | grep my //发现系统重新拉起

root          2157     1 79 15:13:03 ?    00:00:04 myservice

root          2167  2147 3 15:13:09 pts/1 00:00:00 grep my

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