Android jdwp 原理

jdwp

Android jdwp 原理

jdwp 工做原理

• 在setCommandLineDefaults 里面设置了开关，默认开启。

• 在dvmJdwpStartup 里面会设置sock或者adb 方式打开监听

JNI_CreateJavaVM 建立虚拟机

实际是使用dvmStartup 去建立核心类，基础线程等工做。

1 JNIEnvExt* pEnv = (JNIEnvExt*) dvmCreateJNIEnv(NULL); 

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2 

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3 /* Initialize VM. */ 

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4 gDvm.initializing = true; 

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5 std:: string status = 

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6 dvmStartup(argc, argv.get(), args->ignoreUnrecognized, (JNIEnv*)pEnv); 

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7 gDvm.initializing = false; 

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调用setCommandLineDefault，设置默认启动参数

1 std:: string dvmStartup(int argc, const char* const argv[], 

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2 bool ignoreUnrecognized, JNIEnv* pEnv) 

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3 { 

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4 ScopedShutdown scopedShutdown; 

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5 assert(gDvm.initializing); 

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6 LOGV( "VM init args (%d):", argc); 

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7 for ( int i = 0; i < argc; i++) { 

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8 LOGV( " %d: '%s'", i, argv[i]); 

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9 } 

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10 //这里会设置一些默认参数。 

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11 setCommandLineDefaults(); 

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12 ...... 

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13 if (gDvm.zygote) { 

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14 if (!initZygote()) { 

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15 return "initZygote failed"; 

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16 } 

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17 } else { 

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18 if (! dvmInitAfterZygote()) { 

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19 return "dvmInitAfterZygote failed"; 

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20 } 

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21 } 

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22 ...... 

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23} 

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须要注意的是CLASSPATH路径填充，和jdwp启动开关

1 static void setCommandLineDefaults() 

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2 { 

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3 const char* envStr = getenv( "CLASSPATH"); 

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4 if (envStr != NULL) { 

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5 gDvm.classPathStr = strdup(envStr); 

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6 } else { 

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7 gDvm.classPathStr = strdup( "."); 

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8 } 

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9 envStr = getenv( "BOOTCLASSPATH"); 

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10 if (envStr != NULL) { 

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11 gDvm.bootClassPathStr = strdup(envStr); 

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12 } else { 

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13 gDvm.bootClassPathStr = strdup( "."); 

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14 } 

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15 ...... 

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16 gDvm.concurrentMarkSweep = true; 

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17 /* gDvm.jdwpSuspend = true; */ 

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18 //这里设置是否开启jdwp 

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19 /* allowed unless zygote config doesn't allow it */ 

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20 gDvm.jdwpAllowed = true; 

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21} 

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具体的配置参数，由启动参数传进

1 static void showJdwpHelp() 

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2 { 

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3 dvmFprintf(stderr, 

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4 "Example: -Xrunjdwp:transport=dt_socket,address=8000,server=y\n"); 

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5 dvmFprintf(stderr, 

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6 "Example: -Xrunjdwp:transport=dt_socket,address=localhost:6500,server=n\n"); 

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7} 

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1 static bool handleJdwpOption(const char* name, const char* value) 

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2 { 

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3 if ( strcmp(name, "transport") == 0) { 

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4 //这里决定使用adb方式，仍是socket方式。 

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5 if ( strcmp(value, "dt_socket") == 0) { 

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6 gDvm.jdwpTransport = kJdwpTransportSocket; 

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7 } else if ( strcmp(value, "dt_android_adb") == 0) { 

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8 gDvm.jdwpTransport = kJdwpTransportAndroidAdb; 

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9 } else { 

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10 LOGE( "JDWP transport '%s' not supported", value); 

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11 return false; 

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12 } 

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13 //是否启动服务 

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14 } else if ( strcmp(name, "server") == 0) { 

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15 if (*value == 'n') 

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16 gDvm.jdwpServer = false; 

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17 else if (*value == 'y') 

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18 gDvm.jdwpServer = true; 

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19 else { 

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20 LOGE( "JDWP option 'server' must be 'y' or 'n'"); 

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21 return false; 

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22 } 

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23 //启动后是否挂起 

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24 } else if ( strcmp(name, "suspend") == 0) { 

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25 if (*value == 'n') 

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26 gDvm.jdwpSuspend = false; 

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27 else if (*value == 'y') 

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28 gDvm.jdwpSuspend = true; 

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29 else { 

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30 LOGE( "JDWP option 'suspend' must be 'y' or 'n'"); 

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31 return false; 

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32 } 

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33 //绑定地址 

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34 } else if ( strcmp(name, "address") == 0) { 

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35 ...... 

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36} 

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dvmInitAfterZygote 里面会调用initJdwp去初始化jdwp。

1 static bool initJdwp() 

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2 { 

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3 assert(!gDvm.zygote); 

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4 /× 

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5 * 这里设置是否开启jdwp 服务。 

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6 */ 

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7 if (gDvm.jdwpAllowed && gDvm.jdwpConfigured) { 

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8 JdwpStartupParams params; 

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9 

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10 if (gDvm.jdwpHost != NULL) { 

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11 if ( strlen(gDvm.jdwpHost) >= sizeof(params.host)- 1) { 

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12 LOGE( "ERROR: hostname too long: '%s'", gDvm.jdwpHost); 

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13 return false; 

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14 } 

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15 strcpy(params.host, gDvm.jdwpHost); 

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16 } else { 

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17 params.host[ 0] = '\0'; 

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18 } 

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19 params.transport = gDvm.jdwpTransport; 

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20 params.server = gDvm.jdwpServer; 

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21 params.suspend = gDvm.jdwpSuspend; 

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22 params.port = gDvm.jdwpPort; 

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23 

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24 gDvm.jdwpState = dvmJdwpStartup(&params); 

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25 ...... 

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26} 

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启动端口监听

adb会使用dvmJdwpAndroidAdbTransport绑定jdwp调用接口，socket会使用dvmJdwpSocketTransport，dvmJdwpNetStartup是实际调用的地方。

1JdwpState* dvmJdwpStartup( const JdwpStartupParams* pParams) 

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2{ 

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3 JdwpState* state = NULL; 

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4 /* comment this out when debugging JDWP itself */ 

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5 android_setMinPriority(LOG_TAG, ANDROID_LOG_DEBUG); 

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6 state = (JdwpState*) calloc( 1, sizeof(JdwpState)); 

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7 ...... 

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8 switch (pParams->transport) { 

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9 case kJdwpTransportSocket: 

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10 // LOGD("prepping for JDWP over TCP"); 

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11 state->transport = dvmJdwpSocketTransport(); 

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12 break; 

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13 case kJdwpTransportAndroidAdb: 

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14 // LOGD("prepping for JDWP over ADB"); 

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15 state->transport = dvmJdwpAndroidAdbTransport(); 

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16 /* TODO */ 

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17 break; 

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18 default: 

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19 LOGE( "Unknown transport %d", pParams->transport); 

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20 assert( false); 

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21 goto fail; 

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22 } 

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23 

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24 if (! dvmJdwpNetStartup(state, pParams)) 

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25 ...... 

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26}