On Dec 2, 4:06 am, bacchus <[email protected]> wrote:
> By startup, I mean to understand how the Android Runtime is setup and
> Dalvik is started.
>
> Throughout the code reading process I've found VMRuntime.
VMRuntime doesn't have a whole lot to do with that. It just has some
utility functions. The class is defined here:
dalvik/libcore/dalvik/src/main/java/dalvik/system/VMRuntime.java
The native methods it refers to are defined here:
dalvik/vm/native/dalvik_system_VMRuntime.c
The VM is created by frameworks/base/core/jni/AndroidRuntime.cpp:
if (JNI_CreateJavaVM(pJavaVM, pEnv, &initArgs) < 0) {
The runtime initialization does a bunch of jumping around, some of
which is cruft from the days before the "zygote" stuff existed.
Here's a part of an explanation I wrote about a week ago when
discussing something related:
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AndroidRuntime.cpp starts the VM, calls into RuntimeInit.main().
Crazy things happen. We end up in ZygoteInit.main(), which has been
requested to call Zygote.forkSystemServer() to create system_server.
The zygote goes to sleep on a socket.
(All of the magic forking and such happens in dalvik/vm/native/
dalvik_system_Zygote.c .)
At this point we have two processes: zygote (a VM with a single thread
that is listening on a socket) and system_server (which was forked
from zygote and is now busily doing stuff). When system_server
decides it wants to create a new app process, it sends an IPC to the
zygote process, which calls Zygote.forkAndSpecialize().
The forkAndSpecialize call takes a bunch of arguments, mostly having
to do with what uid and capabilities the new process should have.
(zygote runs as root.) When the child process returns to Java-land,
it reads some more stuff from the command socket, then closes it.
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