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Zygote process
2022-06-23 05:19:00 【xhBruce】
Zygote process
android12-release
Android The system starts
init process – What have you done
system/core/init/init.cpp
system/core/rootdir/init.rc
frameworks/base/cmds/app_process/app_main.cpp
frameworks/base/core/jni/AndroidRuntime.cpp
frameworks/base/core/java/com/android/internal/os/ZygoteInit.java
frameworks/base/core/java/com/android/internal/os/Zygote.java
Zygote.rc file
Zygote By init process Through analysis init.zygote.rc File ,zygote The corresponding executable program app_process, The corresponding source file is App_main.cpp, The process name is zygote.
init.zygote32.rc file
service zygote /system/bin/app_process -Xzygote /system/bin --zygote --start-system-server
class main
priority -20
user root
group root readproc reserved_disk
socket zygote stream 660 root system
socket usap_pool_primary stream 660 root system
onrestart exec_background - system system -- /system/bin/vdc volume abort_fuse
onrestart write /sys/power/state on
onrestart restart audioserver
onrestart restart cameraserver
onrestart restart media
onrestart restart netd
onrestart restart wificond
writepid /dev/cpuset/foreground/tasks
critical window=${zygote.critical_window.minute:-off} target=zygote-fatal
init.zygote64.rc file
service zygote /system/bin/app_process64 -Xzygote /system/bin --zygote --start-system-server
class main
priority -20
user root
group root readproc reserved_disk
socket zygote stream 660 root system
socket usap_pool_primary stream 660 root system
onrestart exec_background - system system -- /system/bin/vdc volume abort_fuse
onrestart write /sys/power/state on
onrestart restart audioserver
onrestart restart cameraserver
onrestart restart media
onrestart restart netd
onrestart restart wificond
writepid /dev/cpuset/foreground/tasks
critical window=${zygote.critical_window.minute:-off} target=zygote-fatal
Creation is called "zygote" Of service Structure ;
Create for "socket" communication socketinfo Structure ;
establish "onrestart" Of action Structure .Zygote Where the process can be restarted .
Zygote The service will follow main class Start while start ,zygote The corresponding executable file is /system/bin/app_processXX, By calling pid =fork() Create child process , adopt execve(svc->args[0], (char**)svc->args, (char**) ENV), Get into App_main.cpp Of main() function .
init analysis /system/etc/init/hw/init.${ro.zygote}.rc File to start the Zygote process 
Zygote The boot process
app_main#main
frameworks/base/cmds/app_process/app_main.cpp
strcmp(arg, "--zygote")zygote by true,niceName = ZYGOTE_NICE_NAMEdistinguish 32 position 、64 Bit systemstrcmp(arg, "--start-system-server")startSystemServer by trueruntime.setArgv0(niceName.string(), true /* setProcName */);Set the process nameruntime.start("com.android.internal.os.ZygoteInit", args, zygote);
#if defined(__LP64__)
static const char ABI_LIST_PROPERTY[] = "ro.product.cpu.abilist64";
static const char ZYGOTE_NICE_NAME[] = "zygote64";
#else
static const char ABI_LIST_PROPERTY[] = "ro.product.cpu.abilist32";
static const char ZYGOTE_NICE_NAME[] = "zygote";
#endif
int main(int argc, char* const argv[])
{
//... ...
while (i < argc) {
const char* arg = argv[i++];
if (strcmp(arg, "--zygote") == 0) {
zygote = true;
niceName = ZYGOTE_NICE_NAME;
} else if (strcmp(arg, "--start-system-server") == 0) {
startSystemServer = true;
} else if (strcmp(arg, "--application") == 0) {
application = true;
} else if (strncmp(arg, "--nice-name=", 12) == 0) {
niceName.setTo(arg + 12);
} else if (strncmp(arg, "--", 2) != 0) {
className.setTo(arg);
break;
} else {
--i;
break;
}
}
//... ...
if (startSystemServer) {
args.add(String8("start-system-server"));
}
//... ...
if (!niceName.isEmpty()) {
runtime.setArgv0(niceName.string(), true /* setProcName */);
}
if (zygote) {
runtime.start("com.android.internal.os.ZygoteInit", args, zygote);
} else if (className) {
runtime.start("com.android.internal.os.RuntimeInit", args, zygote);
} else {
fprintf(stderr, "Error: no class name or --zygote supplied.\n");
app_usage();
LOG_ALWAYS_FATAL("app_process: no class name or --zygote supplied.");
}
}
AndroidRuntime::start
frameworks/base/core/jni/include/android_runtime/AndroidRuntime.h
frameworks/base/core/jni/AndroidRuntime.cpp
primary_zygote = truestartVm()Create a start java virtual machinestartReg()register_jni_procs in JNI Methods registrationenv->CallStaticVoidMethod(startClass, startMeth, strArray)here startClass by "com.android.internal.os.ZygoteInit",startMeth by main() Methodfree(slashClassName)Free the memory space of the corresponding object
void AndroidRuntime::start(const char* className, const Vector<String8>& options, bool zygote)
{
//... ...
/* * 'startSystemServer == true' means runtime is obsolete and not run from * init.rc anymore, so we print out the boot start event here. */
for (size_t i = 0; i < options.size(); ++i) {
if (options[i] == startSystemServer) {
primary_zygote = true;
/* track our progress through the boot sequence */
const int LOG_BOOT_PROGRESS_START = 3000;
LOG_EVENT_LONG(LOG_BOOT_PROGRESS_START, ns2ms(systemTime(SYSTEM_TIME_MONOTONIC)));
}
}
//... ...
/* start the virtual machine */
JniInvocation jni_invocation;
jni_invocation.Init(NULL);
JNIEnv* env;
if (startVm(&mJavaVM, &env, zygote, primary_zygote) != 0) {
return;
}
onVmCreated(env);
/* * Register android functions. */
if (startReg(env) < 0) {
ALOGE("Unable to register all android natives\n");
return;
}
//... ...
/* * Start VM. This thread becomes the main thread of the VM, and will * not return until the VM exits. */
char* slashClassName = toSlashClassName(className != NULL ? className : "");
jclass startClass = env->FindClass(slashClassName);
if (startClass == NULL) {
ALOGE("JavaVM unable to locate class '%s'\n", slashClassName);
/* keep going */
} else {
jmethodID startMeth = env->GetStaticMethodID(startClass, "main",
"([Ljava/lang/String;)V");
if (startMeth == NULL) {
ALOGE("JavaVM unable to find main() in '%s'\n", className);
/* keep going */
} else {
env->CallStaticVoidMethod(startClass, startMeth, strArray);
#if 0
if (env->ExceptionCheck())
threadExitUncaughtException(env);
#endif
}
}
free(slashClassName);
ALOGD("Shutting down VM\n");
if (mJavaVM->DetachCurrentThread() != JNI_OK)
ALOGW("Warning: unable to detach main thread\n");
if (mJavaVM->DestroyJavaVM() != 0)
ALOGW("Warning: VM did not shut down cleanly\n");
}
JNI To Java layer
ZygoteInit.main
frameworks/base/core/java/com/android/internal/os/ZygoteInit.java
RuntimeInit.preForkInit()in RuntimeInit.enableDdms()startSystemServer = truezygoteServer = new ZygoteServer(isPrimaryZygote)by Zygote register socketforkSystemServer()start-up SystemServercaller = zygoteServer.runSelectLoop(abiList);Enter cycle mode ,Zygote Adopt efficient I/O Multiplexing mechanism , Ensure hibernation without client connection requests or data processing , Otherwise, respond to the client's request .
public static void main(String[] argv) {
ZygoteServer zygoteServer = null;
// Mark zygote start. This ensures that thread creation will throw
// an error.
ZygoteHooks.startZygoteNoThreadCreation();
// Zygote goes into its own process group.
try {
Os.setpgid(0, 0);
} catch (ErrnoException ex) {
throw new RuntimeException("Failed to setpgid(0,0)", ex);
}
Runnable caller;
try {
// Store now for StatsLogging later.
final long startTime = SystemClock.elapsedRealtime();
final boolean isRuntimeRestarted = "1".equals(
SystemProperties.get("sys.boot_completed"));
String bootTimeTag = Process.is64Bit() ? "Zygote64Timing" : "Zygote32Timing";
TimingsTraceLog bootTimingsTraceLog = new TimingsTraceLog(bootTimeTag,
Trace.TRACE_TAG_DALVIK);
bootTimingsTraceLog.traceBegin("ZygoteInit");
RuntimeInit.preForkInit();
boolean startSystemServer = false;
String zygoteSocketName = "zygote";
String abiList = null;
boolean enableLazyPreload = false;
for (int i = 1; i < argv.length; i++) {
if ("start-system-server".equals(argv[i])) {
startSystemServer = true;
} else if ("--enable-lazy-preload".equals(argv[i])) {
enableLazyPreload = true;
} else if (argv[i].startsWith(ABI_LIST_ARG)) {
abiList = argv[i].substring(ABI_LIST_ARG.length());
} else if (argv[i].startsWith(SOCKET_NAME_ARG)) {
zygoteSocketName = argv[i].substring(SOCKET_NAME_ARG.length());
} else {
throw new RuntimeException("Unknown command line argument: " + argv[i]);
}
}
final boolean isPrimaryZygote = zygoteSocketName.equals(Zygote.PRIMARY_SOCKET_NAME);
if (!isRuntimeRestarted) {
if (isPrimaryZygote) {
FrameworkStatsLog.write(FrameworkStatsLog.BOOT_TIME_EVENT_ELAPSED_TIME_REPORTED,
BOOT_TIME_EVENT_ELAPSED_TIME__EVENT__ZYGOTE_INIT_START,
startTime);
} else if (zygoteSocketName.equals(Zygote.SECONDARY_SOCKET_NAME)) {
FrameworkStatsLog.write(FrameworkStatsLog.BOOT_TIME_EVENT_ELAPSED_TIME_REPORTED,
BOOT_TIME_EVENT_ELAPSED_TIME__EVENT__SECONDARY_ZYGOTE_INIT_START,
startTime);
}
}
if (abiList == null) {
throw new RuntimeException("No ABI list supplied.");
}
// 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());
preload(bootTimingsTraceLog);
EventLog.writeEvent(LOG_BOOT_PROGRESS_PRELOAD_END,
SystemClock.uptimeMillis());
bootTimingsTraceLog.traceEnd(); // ZygotePreload
}
// Do an initial gc to clean up after startup
bootTimingsTraceLog.traceBegin("PostZygoteInitGC");
gcAndFinalize();
bootTimingsTraceLog.traceEnd(); // PostZygoteInitGC
bootTimingsTraceLog.traceEnd(); // ZygoteInit
Zygote.initNativeState(isPrimaryZygote);
ZygoteHooks.stopZygoteNoThreadCreation();
zygoteServer = new ZygoteServer(isPrimaryZygote);
if (startSystemServer) {
Runnable r = forkSystemServer(abiList, zygoteSocketName, 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;
}
}
Log.i(TAG, "Accepting command socket connections");
// The select loop returns early in the child process after a fork and
// loops forever in the zygote.
caller = zygoteServer.runSelectLoop(abiList);
} catch (Throwable ex) {
Log.e(TAG, "System zygote died with fatal exception", ex);
throw ex;
} finally {
if (zygoteServer != null) {
zygoteServer.closeServerSocket();
}
}
// We're in the child process and have exited the select loop. Proceed to execute the
// command.
if (caller != null) {
caller.run();
}
}
forkSystemServer
pid = Zygote.forkSystemServerPrepare parameters and fork New process , As can be seen from the above SystemServer The process parameter information is uid=1000,gid=1000, The process name is sytem_server,
private static Runnable forkSystemServer(String abiList, String socketName,
ZygoteServer zygoteServer) {
//... ...
/* Hardcoded command line to start the system server */
String[] args = {
"--setuid=1000",
"--setgid=1000",
"--setgroups=1001,1002,1003,1004,1005,1006,1007,1008,1009,1010,1018,1021,1023,"
+ "1024,1032,1065,3001,3002,3003,3006,3007,3009,3010,3011",
"--capabilities=" + capabilities + "," + capabilities,
"--nice-name=system_server",
"--runtime-args",
"--target-sdk-version=" + VMRuntime.SDK_VERSION_CUR_DEVELOPMENT,
"com.android.server.SystemServer",
};
ZygoteArguments parsedArgs;
//... ...
/* Request to fork the system server process */
pid = Zygote.forkSystemServer(
parsedArgs.mUid, parsedArgs.mGid,
parsedArgs.mGids,
parsedArgs.mRuntimeFlags,
null,
parsedArgs.mPermittedCapabilities,
parsedArgs.mEffectiveCapabilities);
} catch (IllegalArgumentException ex) {
throw new RuntimeException(ex);
}
/* For child process */
if (pid == 0) {
if (hasSecondZygote(abiList)) {
waitForSecondaryZygote(socketName);
}
zygoteServer.closeServerSocket();
return handleSystemServerProcess(parsedArgs);
}
return null;
}
frameworks/base/core/java/com/android/internal/os/Zygote.java
static int forkSystemServer(int uid, int gid, int[] gids, int runtimeFlags,
int[][] rlimits, long permittedCapabilities, long effectiveCapabilities) {
ZygoteHooks.preFork();
int pid = nativeForkSystemServer(
uid, gid, gids, runtimeFlags, rlimits,
permittedCapabilities, effectiveCapabilities);
// Set the Java Language thread priority to the default value for new apps.
Thread.currentThread().setPriority(Thread.NORM_PRIORITY);
ZygoteHooks.postForkCommon();
return pid;
}
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