app_main.cpp

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

#define LOG_TAG "appproc"

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

#if PLATFORM_SDK_VERSION >= 16
#include <sys/personality.h>
#endif

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

#include "xposed.h"
#include <dlfcn.h>

static bool isXposedLoaded = false;


namespace android {

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

void _atrace_set_tracing_enabled(bool enabled)
{
    if (xposed::getSdkVersion() < 18)
        return;

    dlerror(); // Clear existing errors

    void (*PTR_atrace_set_tracing_enabled)(bool);
    *(void **) (&PTR_atrace_set_tracing_enabled) = dlsym(RTLD_DEFAULT, "atrace_set_tracing_enabled");

    const char *error;
    if ((error = dlerror()) != NULL) {
        ALOGE("Could not find address for function atrace_set_tracing_enabled: %s", error);
    } else {
        PTR_atrace_set_tracing_enabled(enabled);
    }
}

class AppRuntime : public AndroidRuntime
{
public:
    AppRuntime()
        : 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 (isXposedLoaded)
            xposed::onVmCreated(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;

/*
 * sets argv0 to as much of newArgv0 as will fit
 */
static void setArgv0(const char *argv0, const char *newArgv0)
{
    strlcpy(const_cast<char *>(argv0), newArgv0, strlen(argv0));
}

int main(int argc, char* const argv[])
{
    if (xposed::handleOptions(argc, argv))
        return 0;

#if PLATFORM_SDK_VERSION >= 16
#ifdef __arm__
    /*
     * b/7188322 - Temporarily revert to the compat memory layout
     * to avoid breaking third party apps.
     *
     * THIS WILL GO AWAY IN A FUTURE ANDROID RELEASE.
     *
     * http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=7dbaa466
     * changes the kernel mapping from bottom up to top-down.
     * This breaks some programs which improperly embed
     * an out of date copy of Android's linker.
     */
    char value[PROPERTY_VALUE_MAX];
    property_get("ro.kernel.qemu", value, "");
    bool is_qemu = (strcmp(value, "1") == 0);
    if ((getenv("NO_ADDR_COMPAT_LAYOUT_FIXUP") == NULL) && !is_qemu) {
        int current = personality(0xFFFFFFFF);
        if ((current & ADDR_COMPAT_LAYOUT) == 0) {
            personality(current | ADDR_COMPAT_LAYOUT);
            setenv("NO_ADDR_COMPAT_LAYOUT_FIXUP", "1", 1);
            execv("/system/bin/app_process", argv);
            return -1;
        }
    }
    unsetenv("NO_ADDR_COMPAT_LAYOUT_FIXUP");
#endif
#endif

    // These are global variables in ProcessState.cpp
    mArgC = argc;
    mArgV = argv;

    mArgLen = 0;
    for (int i=0; i<argc; i++) {
        mArgLen += strlen(argv[i]) + 1;
    }
    mArgLen--;

    AppRuntime runtime;
    const char* argv0 = argv[0];

    // 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) {
        setArgv0(argv0, niceName);
        set_process_name(niceName);
    }

    runtime.mParentDir = parentDir;

    isXposedLoaded = xposed::initialize(zygote, startSystemServer, className, argc, argv);
    if (zygote) {
        runtime.start(isXposedLoaded ? XPOSED_CLASS_DOTS_ZYGOTE : "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(isXposedLoaded ? XPOSED_CLASS_DOTS_TOOLS : "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;
    }
}