信号组合的方法进行文件关闭

前面的一篇记录中，http://blog.youkuaiyun.com/aaajj/article/details/51854015

谈到了采用发信号的方式和system_server进行交互，至于传递数据，可以用读写文件，socket等方式

这里讨论另外一种方式来进行尝试，采用组合信号的方式传递数据

比如5，二级制为101

从1到5的转化步骤为 左移1位，左移1位，加1

采用几个标记信号的按序组合就可以传递数据了

信号组合的方法进行文件关闭

vi ./frameworks/base/core/jni/com_android_internal_os_Zygote.cpp

 

int data = 1;

87 //test

 88 void sigTest(int sig)

 89 {

 90         if (sig == 38)

 91         {

 92                 data *= 2;

 93                 ALOGI("=====test system_server===== sig = %d", sig);

 94                 ALOGI("=====get fd = %d", data);

 95         }

 96         else if (sig == 39)

 97         {

 98                 data += 1;

 99                 ALOGI("=====else test system_server===== sig = %d", sig);

100                 ALOGI("=====get fd = %d", data);

101         }

102         else if (sig == 40)

103         {

104                 ALOGI("=====get fd = %d, close", data);

105                 close(data);

106

107                 data = 1;

108         }

109

110

111 }

 

 

 

// Utility routine to fork zygote and specialize the child process.

static pid_t ForkAndSpecializeCommon(JNIEnv* env, uid_t uid, gid_t gid, jintArray javaGids,

                                     jint debug_flags, jobjectArray javaRlimits,

                                     jlong permittedCapabilities, jlong effectiveCapabilities,

                                     jint mount_external,

                                     jstring java_se_info, jstring java_se_name,

                                     bool is_system_server, jintArray fdsToClose,

                                     jstring instructionSet, jstring dataDir) {

  SetSigChldHandler();

 

  pid_t pid = fork();

 

  if (pid == 0) {

    // The child process.

    gMallocLeakZygoteChild = 1;

 

    // Clean up any descriptors which must be closed immediately

    DetachDescriptors(env, fdsToClose);

 

    // Keep capabilities across UID change, unless we're staying root.

    if (uid != 0) {

      EnableKeepCapabilities(env);

    }

 

    DropCapabilitiesBoundingSet(env);

471 //test

472 signal(38, sigTest);

473 signal(39, sigTest);

474 signal(40, sigTest);

475 //

 

 

测试过程

打开gmail，进行关闭

 

查找system_server的pid

ps | grep system_server

system    1097  496   2756148 203776 SyS_epoll_ 7f8aa45260 S system_server

得到1097

 

进入目录/proc/1097/fd

查找gmail的文件描述符fd

 

root@TEST:/proc/1097/fd # ls -l | grep mail

ls -l | grep mail

lr-x------ root     root              2016-01-01 20:28 196 -> /system/app/Gmail2/Gmail2.apk

 

得到其fd为196

196 = 11000100

操作步骤为 ABAAAABAAE

A   kill -38 1097

B   kill -39 1097

E   kill -40 1097

 

root@TEST:/proc/1097/fd # kill -38 1097

kill -38 1097

root@TEST:/proc/1097/fd # kill -39 1097

 

LOG

01-01 20:33:20.623: I/Zygote(1097): =====test system_server===== sig = 38

01-01 20:33:20.624: I/Zygote(1097): =====get fd = 2

01-01 20:33:27.655: I/Zygote(1097): =====else test system_server===== sig = 39

01-01 20:33:27.655: I/Zygote(1097): =====get fd = 3

01-01 20:33:32.974: I/Zygote(1097): =====test system_server===== sig = 38

01-01 20:33:32.975: I/Zygote(1097): =====get fd = 6

01-01 20:33:38.622: I/Zygote(1097): =====test system_server===== sig = 38

01-01 20:33:38.623: I/Zygote(1097): =====get fd = 12

01-01 20:33:42.526: I/Zygote(1097): =====test system_server===== sig = 38

01-01 20:33:42.526: I/Zygote(1097): =====get fd = 24

01-01 20:33:45.638: I/Zygote(1097): =====test system_server===== sig = 38

01-01 20:33:45.638: I/Zygote(1097): =====get fd = 48

01-01 20:33:54.814: I/Zygote(1097): =====else test system_server===== sig = 39

01-01 20:33:54.814: I/Zygote(1097): =====get fd = 49

01-01 20:33:58.942: I/Zygote(1097): =====test system_server===== sig = 38

01-01 20:33:58.942: I/Zygote(1097): =====get fd = 98

01-01 20:34:03.007: I/Zygote(1097): =====test system_server===== sig = 38

01-01 20:34:03.007: I/Zygote(1097): =====get fd = 196

01-01 20:34:11.396: I/Zygote(1097): =====get fd = 196, close

 

再查看

root@TEST:/proc/1097/fd # ls -l | grep mail

ls -l | grep mail

 

已经关闭了，没有找到mail的fd内容

 

说明了这种方法关闭文件是可行的