android_frameworks_base/cmds/app_process/app_main.cpp

/*
 * Main entry of app process.
 *
 * Starts the interpreted runtime, then starts up the application.
 *
 */

#define LOG_TAG "appproc"

#include <binder/IPCThreadState.h>
#include <binder/ProcessState.h>
#include <utils/Log.h>
#include <cutils/process_name.h>
#include <cutils/memory.h>
#include <cutils/trace.h>
#include <android_runtime/AndroidRuntime.h>

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>

namespace android {

void app_usage()
{
    fprintf(stderr,
        "Usage: app_process [java-options] cmd-dir start-class-name [options]\n");
}

class AppRuntime : public AndroidRuntime
{
public:
    AppRuntime(char* argBlockStart, const size_t argBlockLength)
        : AndroidRuntime(argBlockStart, argBlockLength)
        , mParentDir(NULL)
        , mClassName(NULL)
        , mClass(NULL)
        , mArgC(0)
        , mArgV(NULL)
    {
    }

#if 0
    // this appears to be unused
    const char* getParentDir() const
    {
        return mParentDir;
    }
#endif

    const char* getClassName() const
    {
        return mClassName;
    }

    virtual void onVmCreated(JNIEnv* env)
    {
        if (mClassName == NULL) {
            return; // Zygote. Nothing to do here.
        }

        /*
         * This is a little awkward because the JNI FindClass call uses the
         * class loader associated with the native method we're executing in.
         * If called in onStarted (from RuntimeInit.finishInit because we're
         * launching "am", for example), FindClass would see that we're calling
         * from a boot class' native method, and so wouldn't look for the class
         * we're trying to look up in CLASSPATH. Unfortunately it needs to,
         * because the "am" classes are not boot classes.
         *
         * The easiest fix is to call FindClass here, early on before we start
         * executing boot class Java code and thereby deny ourselves access to
         * non-boot classes.
         */
        char* slashClassName = toSlashClassName(mClassName);
        mClass = env->FindClass(slashClassName);
        if (mClass == NULL) {
            ALOGE("ERROR: could not find class '%s'\n", mClassName);
        }
        free(slashClassName);

        mClass = reinterpret_cast<jclass>(env->NewGlobalRef(mClass));
    }

    virtual void onStarted()
    {
        sp<ProcessState> proc = ProcessState::self();
        ALOGV("App process: starting thread pool.\n");
        proc->startThreadPool();

        AndroidRuntime* ar = AndroidRuntime::getRuntime();
        ar->callMain(mClassName, mClass, mArgC, mArgV);

        IPCThreadState::self()->stopProcess();
    }

    virtual void onZygoteInit()
    {
        // Re-enable tracing now that we're no longer in Zygote.
        atrace_set_tracing_enabled(true);

        sp<ProcessState> proc = ProcessState::self();
        ALOGV("App process: starting thread pool.\n");
        proc->startThreadPool();
    }

    virtual void onExit(int code)
    {
        if (mClassName == NULL) {
            // if zygote
            IPCThreadState::self()->stopProcess();
        }

        AndroidRuntime::onExit(code);
    }


    const char* mParentDir;
    const char* mClassName;
    jclass mClass;
    int mArgC;
    const char* const* mArgV;
};

}

using namespace android;

static size_t computeArgBlockSize(int argc, char* const argv[]) {
    // TODO: This assumes that all arguments are allocated in
    // contiguous memory. There isn't any documented guarantee
    // that this is the case, but this is how the kernel does it
    // (see fs/exec.c).
    //
    // Also note that this is a constant for "normal" android apps.
    // Since they're forked from zygote, the size of their command line
    // is the size of the zygote command line.
    //
    // We change the process name of the process by over-writing
    // the start of the argument block (argv[0]) with the new name of
    // the process, so we'd mysteriously start getting truncated process
    // names if the zygote command line decreases in size.
    uintptr_t start = reinterpret_cast<uintptr_t>(argv[0]);
    uintptr_t end = reinterpret_cast<uintptr_t>(argv[argc - 1]);
    end += strlen(argv[argc - 1]);

    return (end - start);
}

int main(int argc, char* const argv[])
{
    AppRuntime runtime(argv[0], computeArgBlockSize(argc, argv));
    // Process command line arguments
    // ignore argv[0]
    argc--;
    argv++;

    // Everything up to '--' or first non '-' arg goes to the vm

    int i = runtime.addVmArguments(argc, argv);

    // Parse runtime arguments.  Stop at first unrecognized option.
    bool zygote = false;
    bool startSystemServer = false;
    bool application = false;
    const char* parentDir = NULL;
    const char* niceName = NULL;
    const char* className = NULL;
    while (i < argc) {
        const char* arg = argv[i++];
        if (!parentDir) {
            parentDir = arg;
        } else if (strcmp(arg, "--zygote") == 0) {
            zygote = true;
            niceName = "zygote";
        } 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 = arg + 12;
        } else {
            className = arg;
            break;
        }
    }

    if (niceName && *niceName) {
        runtime.setArgv0(niceName);
        set_process_name(niceName);
    }

    runtime.mParentDir = parentDir;

    if (zygote) {
        runtime.start("com.android.internal.os.ZygoteInit",
                startSystemServer ? "start-system-server" : "");
    } else if (className) {
        // Remainder of args get passed to startup class main()
        runtime.mClassName = className;
        runtime.mArgC = argc - i;
        runtime.mArgV = argv + i;
        runtime.start("com.android.internal.os.RuntimeInit",
                application ? "application" : "tool");
    } else {
        fprintf(stderr, "Error: no class name or --zygote supplied.\n");
        app_usage();
        LOG_ALWAYS_FATAL("app_process: no class name or --zygote supplied.");
        return 10;
    }
}