Android at its core has a process they call the “Zygote”, which starts up at init. It gets it’s name from dictionary definition: “It is the initial cell formed when a new organism is produced”. This process is a “Warmed-up” process, which means it’s a process that’s been initialized and has all the core libraries linked in.
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- Zygote is a special process in Android which handles the forking of each new application process. These processes are simply regular Linux processes.
- In Linux systems one can easily inject any code or library with modifying LD_PRELOAD but in Android JVM is already forked from zygote once an app is running.
- This method is called once every time the Application Zygote is started. It is normally started the first time an isolated service that uses it is started.
- Zygote is launched by "app_process"
- Zygote loads all needed Java Classes.
- It opens a socket, to listen other applications starting (/dev/socket/zygote)
- Android Zygote Introduction, Programmer All, we have been working hard to make a technical sharing website that all programmers love.
- Zygote isn't really bound up with Dalvik, it's just an init process. Zygote is the method Android uses to start apps.
- [Weakness] As of Android 12, Zygote will only process one command per read() call, dropping any extra bytes.
- Zygote translates as “fertilized eggs.” In Android, the process of incubating the new process is Zygote, and the other applications on Andre are hatched by it.
- 0) { className.setTo(arg); break; } else { --i; break; }} if (zygote) {// If zygote is true, call AndroidRuntime start. And into the "com. Android.
- The process Zygote starts up during Android initialization. Zygote is a system service for launching apps.
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Q. how does zygote exactly fork Dalvik VM?Short Answer:
The Zygote process cold boots a Java VM on system start up. It then listens to a socket for incoming commands. Other processes (e.g. ActivityManagerService) write commands to this socket whenever a new process is needed for an application. These commands are read by the Zygote process which calls fork() as necessary. Child processes get a pre-warmed VM in which to run. This is how Zygote forks the Dalvik VM.Long answer: After the kernel is loaded, is parsed and native services are started. Then ) is run. This eventually calls , passing it the parameters and .The starts a Java VM then calls , passing it the parameter . registers the Zygote socket (which the Zygote process listens to for incoming commands, and on receiving new command, spawns a new process as requested). It then preloads a lot of classes (as listed in frameworks/base/preloaded-classes, over 4500 in Android 8.0) and all the system-wide resources like drawables, xmls, etc. Then it calls which forks a new process for . This fork is special and is not done in the same manner as the usual forks the Zygote performs on behalf of requesting processes.After SystemServer is forked the function is called. This is a loop which establishes a with the Zygote socket and waits for commands on it. When a command is received, is called. then calls which then calls a native function to do the actual fork. Thus, like in the case of SystemServer, a child process is created which inherits a pre-warmed Dalvik VM for itself.Q. why it is not possible to run multiple applications in the same
Dalvik VM?This is a design decision as far as I know. The Android guys just decided to fork a new VM per process for security via sandboxing.
init.rc/system/bin/app_processAndroidRuntime.start()com.android.internal.os.ZygoteInitstart-system-serverAndroidRuntime.start()ZygoteInit.main()start-system-serverZygoteInit.main()startSystemServer()com.android.server.SystemServerrunSelectLoopMode()while(true)ZygoteConnectionZygoteConnection.runOnce()ZygoteConnection.runOnce()Zygote.forkAndSpecialize()