码迷,mamicode.com
首页 > 其他好文 > 详细

dalvik启动过程

时间:2015-05-08 16:32:47      阅读:309      评论:0      收藏:0      [点我收藏+]

标签:android   虚拟机   dalvik   

Zygote进程启动过程分析过程中,我们知道,dalvik虚拟机的启动过程是从AndroidRuntime::startVm(JavaVM** pJavaVM, JNIEnv** pEnv)函数开始的,详细时序图如下:
技术分享
下面我们来逐步详细地分析一下每个步骤。

1.startVm(AndroidRuntime.cpp)

/*
 * Start the Dalvik Virtual Machine.
 *
 * Various arguments, most determined by system properties, are passed in.
 * The "mOptions" vector is updated.
 *
 * Returns 0 on success.
 */
int AndroidRuntime::startVm(JavaVM** pJavaVM, JNIEnv** pEnv)
{
    int result = -1;
    JavaVMInitArgs initArgs;
    JavaVMOption opt;
    char propBuf[PROPERTY_VALUE_MAX];
    char stackTraceFileBuf[PROPERTY_VALUE_MAX];
    char dexoptFlagsBuf[PROPERTY_VALUE_MAX];
    char enableAssertBuf[sizeof("-ea:")-1 + PROPERTY_VALUE_MAX];
    char jniOptsBuf[sizeof("-Xjniopts:")-1 + PROPERTY_VALUE_MAX];
    char heapstartsizeOptsBuf[sizeof("-Xms")-1 + PROPERTY_VALUE_MAX];
    char heapsizeOptsBuf[sizeof("-Xmx")-1 + PROPERTY_VALUE_MAX];
    char heapgrowthlimitOptsBuf[sizeof("-XX:HeapGrowthLimit=")-1 + PROPERTY_VALUE_MAX];
    char heapminfreeOptsBuf[sizeof("-XX:HeapMinFree=")-1 + PROPERTY_VALUE_MAX];
    char heapmaxfreeOptsBuf[sizeof("-XX:HeapMaxFree=")-1 + PROPERTY_VALUE_MAX];
    char heaptargetutilizationOptsBuf[sizeof("-XX:HeapTargetUtilization=")-1 + PROPERTY_VALUE_MAX];
    char jitcodecachesizeOptsBuf[sizeof("-Xjitcodecachesize:")-1 + PROPERTY_VALUE_MAX];
    char extraOptsBuf[PROPERTY_VALUE_MAX];
    char* stackTraceFile = NULL;
    bool checkJni = false;
    bool checkDexSum = false;
    bool logStdio = false;
    enum {
      kEMDefault,
      kEMIntPortable,
      kEMIntFast,
      kEMJitCompiler,
    } executionMode = kEMDefault;


    property_get("dalvik.vm.checkjni", propBuf, "");
    if (strcmp(propBuf, "true") == 0) {
        checkJni = true;
    } else if (strcmp(propBuf, "false") != 0) {
        /* property is neither true nor false; fall back on kernel parameter */
        property_get("ro.kernel.android.checkjni", propBuf, "");
        if (propBuf[0] == ‘1‘) {
            checkJni = true;
        }
    }

    property_get("dalvik.vm.execution-mode", propBuf, "");
    if (strcmp(propBuf, "int:portable") == 0) {
        executionMode = kEMIntPortable;
    } else if (strcmp(propBuf, "int:fast") == 0) {
        executionMode = kEMIntFast;
    } else if (strcmp(propBuf, "int:jit") == 0) {
        executionMode = kEMJitCompiler;
    }

    property_get("dalvik.vm.stack-trace-file", stackTraceFileBuf, "");

    property_get("dalvik.vm.check-dex-sum", propBuf, "");
    if (strcmp(propBuf, "true") == 0) {
        checkDexSum = true;
    }

    property_get("log.redirect-stdio", propBuf, "");
    if (strcmp(propBuf, "true") == 0) {
        logStdio = true;
    }

    strcpy(enableAssertBuf, "-ea:");
    property_get("dalvik.vm.enableassertions", enableAssertBuf+4, "");

    strcpy(jniOptsBuf, "-Xjniopts:");
    property_get("dalvik.vm.jniopts", jniOptsBuf+10, "");

    /* route exit() to our handler */
    opt.extraInfo = (void*) runtime_exit;
    opt.optionString = "exit";
    mOptions.add(opt);

    /* route fprintf() to our handler */
    opt.extraInfo = (void*) runtime_vfprintf;
    opt.optionString = "vfprintf";
    mOptions.add(opt);

    /* register the framework-specific "is sensitive thread" hook */
    opt.extraInfo = (void*) runtime_isSensitiveThread;
    opt.optionString = "sensitiveThread";
    mOptions.add(opt);

    opt.extraInfo = NULL;

    /* enable verbose; standard options are { jni, gc, class } */
    //options[curOpt++].optionString = "-verbose:jni";
    opt.optionString = "-verbose:gc";
    mOptions.add(opt);
    //options[curOpt++].optionString = "-verbose:class";

    /*
     * The default starting and maximum size of the heap.  Larger
     * values should be specified in a product property override.
     */
    strcpy(heapstartsizeOptsBuf, "-Xms");
    property_get("dalvik.vm.heapstartsize", heapstartsizeOptsBuf+4, "4m");
    opt.optionString = heapstartsizeOptsBuf;
    mOptions.add(opt);
    strcpy(heapsizeOptsBuf, "-Xmx");
    property_get("dalvik.vm.heapsize", heapsizeOptsBuf+4, "16m");
    opt.optionString = heapsizeOptsBuf;
    mOptions.add(opt);

    // Increase the main thread‘s interpreter stack size for bug 6315322.
    opt.optionString = "-XX:mainThreadStackSize=24K";
    mOptions.add(opt);

    // Set the max jit code cache size.  Note: size of 0 will disable the JIT.
    strcpy(jitcodecachesizeOptsBuf, "-Xjitcodecachesize:");
    property_get("dalvik.vm.jit.codecachesize", jitcodecachesizeOptsBuf+19,  NULL);
    if (jitcodecachesizeOptsBuf[19] != ‘\0‘) {
      opt.optionString = jitcodecachesizeOptsBuf;
      mOptions.add(opt);
    }

    strcpy(heapgrowthlimitOptsBuf, "-XX:HeapGrowthLimit=");
    property_get("dalvik.vm.heapgrowthlimit", heapgrowthlimitOptsBuf+20, "");
    if (heapgrowthlimitOptsBuf[20] != ‘\0‘) {
        opt.optionString = heapgrowthlimitOptsBuf;
        mOptions.add(opt);
    }

    strcpy(heapminfreeOptsBuf, "-XX:HeapMinFree=");
    property_get("dalvik.vm.heapminfree", heapminfreeOptsBuf+16, "");
    if (heapminfreeOptsBuf[16] != ‘\0‘) {
        opt.optionString = heapminfreeOptsBuf;
        mOptions.add(opt);
    }

    strcpy(heapmaxfreeOptsBuf, "-XX:HeapMaxFree=");
    property_get("dalvik.vm.heapmaxfree", heapmaxfreeOptsBuf+16, "");
    if (heapmaxfreeOptsBuf[16] != ‘\0‘) {
        opt.optionString = heapmaxfreeOptsBuf;
        mOptions.add(opt);
    }

    strcpy(heaptargetutilizationOptsBuf, "-XX:HeapTargetUtilization=");
    property_get("dalvik.vm.heaptargetutilization", heaptargetutilizationOptsBuf+26, "");
    if (heaptargetutilizationOptsBuf[26] != ‘\0‘) {
        opt.optionString = heaptargetutilizationOptsBuf;
        mOptions.add(opt);
    }

    property_get("ro.config.low_ram", propBuf, "");
    if (strcmp(propBuf, "true") == 0) {
      opt.optionString = "-XX:LowMemoryMode";
      mOptions.add(opt);
    }

    /*
     * Enable or disable dexopt features, such as bytecode verification and
     * calculation of register maps for precise GC.
     */
    property_get("dalvik.vm.dexopt-flags", dexoptFlagsBuf, "");
    if (dexoptFlagsBuf[0] != ‘\0‘) {
        const char* opc;
        const char* val;

        opc = strstr(dexoptFlagsBuf, "v=");     /* verification */
        if (opc != NULL) {
            switch (*(opc+2)) {
            case ‘n‘:   val = "-Xverify:none";      break;
            case ‘r‘:   val = "-Xverify:remote";    break;
            case ‘a‘:   val = "-Xverify:all";       break;
            default:    val = NULL;                 break;
            }

            if (val != NULL) {
                opt.optionString = val;
                mOptions.add(opt);
            }
        }

        opc = strstr(dexoptFlagsBuf, "o=");     /* optimization */
        if (opc != NULL) {
            switch (*(opc+2)) {
            case ‘n‘:   val = "-Xdexopt:none";      break;
            case ‘v‘:   val = "-Xdexopt:verified";  break;
            case ‘a‘:   val = "-Xdexopt:all";       break;
            case ‘f‘:   val = "-Xdexopt:full";      break;
            default:    val = NULL;                 break;
            }

            if (val != NULL) {
                opt.optionString = val;
                mOptions.add(opt);
            }
        }

        opc = strstr(dexoptFlagsBuf, "m=y");    /* register map */
        if (opc != NULL) {
            opt.optionString = "-Xgenregmap";
            mOptions.add(opt);

            /* turn on precise GC while we‘re at it */
            opt.optionString = "-Xgc:precise";
            mOptions.add(opt);
        }
    }

    /* enable debugging; set suspend=y to pause during VM init */
    /* use android ADB transport */
    opt.optionString =
        "-agentlib:jdwp=transport=dt_android_adb,suspend=n,server=y";
    mOptions.add(opt);

    ALOGD("CheckJNI is %s\n", checkJni ? "ON" : "OFF");
    if (checkJni) {
        /* extended JNI checking */
        opt.optionString = "-Xcheck:jni";
        mOptions.add(opt);

        /* set a cap on JNI global references */
        opt.optionString = "-Xjnigreflimit:2000";
        mOptions.add(opt);

        /* with -Xcheck:jni, this provides a JNI function call trace */
        //opt.optionString = "-verbose:jni";
        //mOptions.add(opt);
    }

    char lockProfThresholdBuf[sizeof("-Xlockprofthreshold:") + sizeof(propBuf)];
    property_get("dalvik.vm.lockprof.threshold", propBuf, "");
    if (strlen(propBuf) > 0) {
      strcpy(lockProfThresholdBuf, "-Xlockprofthreshold:");
      strcat(lockProfThresholdBuf, propBuf);
      opt.optionString = lockProfThresholdBuf;
      mOptions.add(opt);
    }

    /* Force interpreter-only mode for selected opcodes. Eg "1-0a,3c,f1-ff" */
    char jitOpBuf[sizeof("-Xjitop:") + PROPERTY_VALUE_MAX];
    property_get("dalvik.vm.jit.op", propBuf, "");
    if (strlen(propBuf) > 0) {
        strcpy(jitOpBuf, "-Xjitop:");
        strcat(jitOpBuf, propBuf);
        opt.optionString = jitOpBuf;
        mOptions.add(opt);
    }

    /* Force interpreter-only mode for selected methods */
    char jitMethodBuf[sizeof("-Xjitmethod:") + PROPERTY_VALUE_MAX];
    property_get("dalvik.vm.jit.method", propBuf, "");
    if (strlen(propBuf) > 0) {
        strcpy(jitMethodBuf, "-Xjitmethod:");
        strcat(jitMethodBuf, propBuf);
        opt.optionString = jitMethodBuf;
        mOptions.add(opt);
    }

    if (executionMode == kEMIntPortable) {
        opt.optionString = "-Xint:portable";
        mOptions.add(opt);
    } else if (executionMode == kEMIntFast) {
        opt.optionString = "-Xint:fast";
        mOptions.add(opt);
    } else if (executionMode == kEMJitCompiler) {
        opt.optionString = "-Xint:jit";
        mOptions.add(opt);
    }

    if (checkDexSum) {
        /* perform additional DEX checksum tests */
        opt.optionString = "-Xcheckdexsum";
        mOptions.add(opt);
    }

    if (logStdio) {
        /* convert stdout/stderr to log messages */
        opt.optionString = "-Xlog-stdio";
        mOptions.add(opt);
    }

    if (enableAssertBuf[4] != ‘\0‘) {
        /* accept "all" to mean "all classes and packages" */
        if (strcmp(enableAssertBuf+4, "all") == 0)
            enableAssertBuf[3] = ‘\0‘;
        ALOGI("Assertions enabled: ‘%s‘\n", enableAssertBuf);
        opt.optionString = enableAssertBuf;
        mOptions.add(opt);
    } else {
        ALOGV("Assertions disabled\n");
    }

    if (jniOptsBuf[10] != ‘\0‘) {
        ALOGI("JNI options: ‘%s‘\n", jniOptsBuf);
        opt.optionString = jniOptsBuf;
        mOptions.add(opt);
    }

    if (stackTraceFileBuf[0] != ‘\0‘) {
        static const char* stfOptName = "-Xstacktracefile:";

        stackTraceFile = (char*) malloc(strlen(stfOptName) +
            strlen(stackTraceFileBuf) +1);
        strcpy(stackTraceFile, stfOptName);
        strcat(stackTraceFile, stackTraceFileBuf);
        opt.optionString = stackTraceFile;
        mOptions.add(opt);
    }

    /* extra options; parse this late so it overrides others */
    property_get("dalvik.vm.extra-opts", extraOptsBuf, "");
    parseExtraOpts(extraOptsBuf);

    /* Set the properties for locale */
    {
        char langOption[sizeof("-Duser.language=") + 3];
        char regionOption[sizeof("-Duser.region=") + 3];
        strcpy(langOption, "-Duser.language=");
        strcpy(regionOption, "-Duser.region=");
        readLocale(langOption, regionOption);
        opt.extraInfo = NULL;
        opt.optionString = langOption;
        mOptions.add(opt);
        opt.optionString = regionOption;
        mOptions.add(opt);
    }

    /*
     * We don‘t have /tmp on the device, but we often have an SD card.  Apps
     * shouldn‘t use this, but some test suites might want to exercise it.
     */
    opt.optionString = "-Djava.io.tmpdir=/sdcard";
    mOptions.add(opt);

    initArgs.version = JNI_VERSION_1_4;
    initArgs.options = mOptions.editArray();
    initArgs.nOptions = mOptions.size();
    initArgs.ignoreUnrecognized = JNI_FALSE;

    /*
     * Initialize the VM.
     *
     * The JavaVM* is essentially per-process, and the JNIEnv* is per-thread.
     * If this call succeeds, the VM is ready, and we can start issuing
     * JNI calls.
     */
    if (JNI_CreateJavaVM(pJavaVM, pEnv, &initArgs) < 0) {
        ALOGE("JNI_CreateJavaVM failed\n");
        goto bail;
    }

    result = 0;

bail:
    free(stackTraceFile);
    return result;
}

startVm的大部分逻辑是在收集虚拟机的配置参数,并将这些配置信心存储到mOptions中,接着将mOptions收集的配置信息赋值给initArgs,initArgs是一个JavaVMInitArgs的对象,从名字就可以猜到该对象管理着虚拟机初始化需要的参数。收集好初始化参数后,就调用JNI_CreateJavaVM开始真刀真枪地创建虚拟机了。

2.JNI_CreateJavaVM(Jni.cpp)

/*
 * Create a new VM instance.
 *
 * The current thread becomes the main VM thread.  We return immediately,
 * which effectively means the caller is executing in a native method.
 */
jint JNI_CreateJavaVM(JavaVM** p_vm, JNIEnv** p_env, void* vm_args) {
    const JavaVMInitArgs* args = (JavaVMInitArgs*) vm_args;
    if (dvmIsBadJniVersion(args->version)) {
        ALOGE("Bad JNI version passed to CreateJavaVM: %d", args->version);
        return JNI_EVERSION;
    }

    // TODO: don‘t allow creation of multiple VMs -- one per customer for now

    /* zero globals; not strictly necessary the first time a VM is started */
    memset(&gDvm, 0, sizeof(gDvm));

    /*
     * Set up structures for JNIEnv and VM.
     */
    JavaVMExt* pVM = (JavaVMExt*) calloc(1, sizeof(JavaVMExt));
    pVM->funcTable = &gInvokeInterface;
    pVM->envList = NULL;
    dvmInitMutex(&pVM->envListLock);

    UniquePtr<const char*[]> argv(new const char*[args->nOptions]);
    memset(argv.get(), 0, sizeof(char*) * (args->nOptions));

    /*
     * Convert JNI args to argv.
     *
     * We have to pull out vfprintf/exit/abort, because they use the
     * "extraInfo" field to pass function pointer "hooks" in.  We also
     * look for the -Xcheck:jni stuff here.
     */
    int argc = 0;
    for (int i = 0; i < args->nOptions; i++) {
        const char* optStr = args->options[i].optionString;
        if (optStr == NULL) {
            dvmFprintf(stderr, "ERROR: CreateJavaVM failed: argument %d was NULL\n", i);
            return JNI_ERR;
        } else if (strcmp(optStr, "vfprintf") == 0) {
            gDvm.vfprintfHook = (int (*)(FILE *, const char*, va_list))args->options[i].extraInfo;
        } else if (strcmp(optStr, "exit") == 0) {
            gDvm.exitHook = (void (*)(int)) args->options[i].extraInfo;
        } else if (strcmp(optStr, "abort") == 0) {
            gDvm.abortHook = (void (*)(void))args->options[i].extraInfo;
        } else if (strcmp(optStr, "sensitiveThread") == 0) {
            gDvm.isSensitiveThreadHook = (bool (*)(void))args->options[i].extraInfo;
        } else if (strcmp(optStr, "-Xcheck:jni") == 0) {
            gDvmJni.useCheckJni = true;
        } else if (strncmp(optStr, "-Xjniopts:", 10) == 0) {
            char* jniOpts = strdup(optStr + 10);
            size_t jniOptCount = 1;
            for (char* p = jniOpts; *p != 0; ++p) {
                if (*p == ‘,‘) {
                    ++jniOptCount;
                    *p = 0;
                }
            }
            char* jniOpt = jniOpts;
            for (size_t i = 0; i < jniOptCount; ++i) {
                if (strcmp(jniOpt, "warnonly") == 0) {
                    gDvmJni.warnOnly = true;
                } else if (strcmp(jniOpt, "forcecopy") == 0) {
                    gDvmJni.forceCopy = true;
                } else if (strcmp(jniOpt, "logThirdPartyJni") == 0) {
                    gDvmJni.logThirdPartyJni = true;
                } else {
                    dvmFprintf(stderr, "ERROR: CreateJavaVM failed: unknown -Xjniopts option ‘%s‘\n",
                            jniOpt);
                    free(pVM);
                    free(jniOpts);
                    return JNI_ERR;
                }
                jniOpt += strlen(jniOpt) + 1;
            }
            free(jniOpts);
        } else {
            /* regular option */
            argv[argc++] = optStr;
        }
    }

    if (gDvmJni.useCheckJni) {
        dvmUseCheckedJniVm(pVM);
    }

    if (gDvmJni.jniVm != NULL) {
        dvmFprintf(stderr, "ERROR: Dalvik only supports one VM per process\n");
        free(pVM);
        return JNI_ERR;
    }
    gDvmJni.jniVm = (JavaVM*) pVM;

    /*
     * Create a JNIEnv for the main thread.  We need to have something set up
     * here because some of the class initialization we do when starting
     * up the VM will call into native code.
     */
    JNIEnvExt* pEnv = (JNIEnvExt*) dvmCreateJNIEnv(NULL);

    /* Initialize VM. */
    gDvm.initializing = true;
    std::string status =
            dvmStartup(argc, argv.get(), args->ignoreUnrecognized, (JNIEnv*)pEnv);
    gDvm.initializing = false;

    if (!status.empty()) {
        free(pEnv);
        free(pVM);
        ALOGW("CreateJavaVM failed: %s", status.c_str());
        return JNI_ERR;
    }

    /*
     * Success!  Return stuff to caller.
     */
    dvmChangeStatus(NULL, THREAD_NATIVE);
    *p_env = (JNIEnv*) pEnv;
    *p_vm = (JavaVM*) pVM;
    ALOGV("CreateJavaVM succeeded");
    return JNI_OK;
}

JNI_CreateJavaVM的逻辑可以分为4步
1.创建JavaVMExt对象,并初始化;
2.将部分初始化参数存储到全局对象gDvm和gDvmJni中,方便后续需要的时候直接从gDvm和gDvmJni中读取;部分初始化参数存储到argv中,供第四步dvmStartup使用;
3.调用dvmCreateJNIEnv创建JNIEnvExt对象,该对象就是主线程的JNIEnv对象;
4.调用dvmStartup启动虚拟机的各个模块;此致,虚拟机的创建工作基本完成。

这里有几个问题是值得我们注意的:
JavaVM和JNIEnv的作用
JavaVM就是虚拟机对象,它的作用简单说就是解释执行java代码,每个android app进程都会有一个虚拟机实例;JNIEnv是与线程相关的对象,每个线程对应一个JNIEnv对象,它是native世界与java世界的桥梁,native通过JNIEnv提供的接口来访问java世界。

JavaVMExt与JavaVM的关系
从文章dalvik核心数据结构我们可以看到,JavaVM其实就是一个JNIInvokeInterface的指针,JNIInvokeInterface定义了一些虚拟机操作相关的函数,JavaVMExt是JavaVM的扩展,它的第一个成员也是一个JNIInvokeInterface的指针,另外扩展了几个成员,对于开发者来说,一般是通过JavaVM来调用相关接口,而不用关注JavaVMExt是如何实现这些接口的。

JNIEnvExt与JNIEnv的关系
JNIEnvExt与JNIEnv的关系,跟JavaVMExt与JavaVM的关系是类似的,JNIEnv提供的接口定义在JNINativeInterface结构体中。

3.dvmCreateJNIEnv(Jni.cpp)

/*
 * Create a new JNIEnv struct and add it to the VM‘s list.
 *
 * "self" will be NULL for the main thread, since the VM hasn‘t started
 * yet; the value will be filled in later.
 */
JNIEnv* dvmCreateJNIEnv(Thread* self) {
    JavaVMExt* vm = (JavaVMExt*) gDvmJni.jniVm;

    //if (self != NULL)
    //    ALOGI("Ent CreateJNIEnv: threadid=%d %p", self->threadId, self);

    assert(vm != NULL);

    JNIEnvExt* newEnv = (JNIEnvExt*) calloc(1, sizeof(JNIEnvExt));
    newEnv->funcTable = &gNativeInterface;
    if (self != NULL) {
        dvmSetJniEnvThreadId((JNIEnv*) newEnv, self);
        assert(newEnv->envThreadId != 0);
    } else {
        /* make it obvious if we fail to initialize these later */
        newEnv->envThreadId = 0x77777775;
        newEnv->self = (Thread*) 0x77777779;
    }
    if (gDvmJni.useCheckJni) {
        dvmUseCheckedJniEnv(newEnv);
    }

    ScopedPthreadMutexLock lock(&vm->envListLock);

    /* insert at head of list */
    newEnv->next = vm->envList;
    assert(newEnv->prev == NULL);
    if (vm->envList == NULL) {
        // rare, but possible
        vm->envList = newEnv;
    } else {
        vm->envList->prev = newEnv;
    }
    vm->envList = newEnv;

    //if (self != NULL)
    //    ALOGI("Xit CreateJNIEnv: threadid=%d %p", self->threadId, self);
    return (JNIEnv*) newEnv;
}

dvmCreateJNIEnv的逻辑比较简单,就是单纯地创建JNIEnvExt并初始化,最后返回新创建的JNIEnvExt对象;envThreadId和self分辨赋值为0x77777775和0x77777779,这两个值表示该JNIEnvExt还未和任何线程绑定。

4.dvmStartup(Init.cpp)

/*
 * VM initialization.  Pass in any options provided on the command line.
 * Do not pass in the class name or the options for the class.
 *
 * Returns 0 on success.
 */
std::string dvmStartup(int argc, const char* const argv[],
        bool ignoreUnrecognized, JNIEnv* pEnv)
{
    ScopedShutdown scopedShutdown;

    assert(gDvm.initializing);

    ALOGV("VM init args (%d):", argc);
    for (int i = 0; i < argc; i++) {
        ALOGV("  %d: ‘%s‘", i, argv[i]);
    }
    setCommandLineDefaults();

    /*
     * Process the option flags (if any).
     */
    int cc = processOptions(argc, argv, ignoreUnrecognized);
    if (cc != 0) {
        if (cc < 0) {
            dvmFprintf(stderr, "\n");
            usage("dalvikvm");
        }
        return "syntax error";
    }

#if WITH_EXTRA_GC_CHECKS > 1
    /* only "portable" interp has the extra goodies */
    if (gDvm.executionMode != kExecutionModeInterpPortable) {
        ALOGI("Switching to ‘portable‘ interpreter for GC checks");
        gDvm.executionMode = kExecutionModeInterpPortable;
    }
#endif

    /* Configure group scheduling capabilities */
    if (!access("/dev/cpuctl/tasks", F_OK)) {
        ALOGV("Using kernel group scheduling");
        gDvm.kernelGroupScheduling = 1;
    } else {
        ALOGV("Using kernel scheduler policies");
    }

    /* configure signal handling */
    if (!gDvm.reduceSignals)
        blockSignals();

    /* verify system page size */
    if (sysconf(_SC_PAGESIZE) != SYSTEM_PAGE_SIZE) {
        return StringPrintf("expected page size %d, got %d",
                SYSTEM_PAGE_SIZE, (int) sysconf(_SC_PAGESIZE));
    }

    /* mterp setup */
    ALOGV("Using executionMode %d", gDvm.executionMode);
    dvmCheckAsmConstants();

    /*
     * Initialize components.
     */
    dvmQuasiAtomicsStartup();
    if (!dvmAllocTrackerStartup()) {
        return "dvmAllocTrackerStartup failed";
    }
    if (!dvmGcStartup()) {
        return "dvmGcStartup failed";
    }
    if (!dvmThreadStartup()) {
        return "dvmThreadStartup failed";
    }
    if (!dvmInlineNativeStartup()) {
        return "dvmInlineNativeStartup";
    }
    if (!dvmRegisterMapStartup()) {
        return "dvmRegisterMapStartup failed";
    }
    if (!dvmInstanceofStartup()) {
        return "dvmInstanceofStartup failed";
    }
    if (!dvmClassStartup()) {
        return "dvmClassStartup failed";
    }

    /*
     * At this point, the system is guaranteed to be sufficiently
     * initialized that we can look up classes and class members. This
     * call populates the gDvm instance with all the class and member
     * references that the VM wants to use directly.
     */
    if (!dvmFindRequiredClassesAndMembers()) {
        return "dvmFindRequiredClassesAndMembers failed";
    }

    if (!dvmStringInternStartup()) {
        return "dvmStringInternStartup failed";
    }
    if (!dvmNativeStartup()) {
        return "dvmNativeStartup failed";
    }
    if (!dvmInternalNativeStartup()) {
        return "dvmInternalNativeStartup failed";
    }
    if (!dvmJniStartup()) {
        return "dvmJniStartup failed";
    }
    if (!dvmProfilingStartup()) {
        return "dvmProfilingStartup failed";
    }

    /*
     * Create a table of methods for which we will substitute an "inline"
     * version for performance.
     */
    if (!dvmCreateInlineSubsTable()) {
        return "dvmCreateInlineSubsTable failed";
    }

    /*
     * Miscellaneous class library validation.
     */
    if (!dvmValidateBoxClasses()) {
        return "dvmValidateBoxClasses failed";
    }

    /*
     * Do the last bits of Thread struct initialization we need to allow
     * JNI calls to work.
     */
    if (!dvmPrepMainForJni(pEnv)) {
        return "dvmPrepMainForJni failed";
    }

    /*
     * Explicitly initialize java.lang.Class.  This doesn‘t happen
     * automatically because it‘s allocated specially (it‘s an instance
     * of itself).  Must happen before registration of system natives,
     * which make some calls that throw assertions if the classes they
     * operate on aren‘t initialized.
     */
    if (!dvmInitClass(gDvm.classJavaLangClass)) {
        return "couldn‘t initialized java.lang.Class";
    }

    /*
     * Register the system native methods, which are registered through JNI.
     */
    if (!registerSystemNatives(pEnv)) {
        return "couldn‘t register system natives";
    }

    /*
     * Do some "late" initialization for the memory allocator.  This may
     * allocate storage and initialize classes.
     */
    if (!dvmCreateStockExceptions()) {
        return "dvmCreateStockExceptions failed";
    }

    /*
     * At this point, the VM is in a pretty good state.  Finish prep on
     * the main thread (specifically, create a java.lang.Thread object to go
     * along with our Thread struct).  Note we will probably be executing
     * some interpreted class initializer code in here.
     */
    if (!dvmPrepMainThread()) {
        return "dvmPrepMainThread failed";
    }

    /*
     * Make sure we haven‘t accumulated any tracked references.  The main
     * thread should be starting with a clean slate.
     */
    if (dvmReferenceTableEntries(&dvmThreadSelf()->internalLocalRefTable) != 0)
    {
        ALOGW("Warning: tracked references remain post-initialization");
        dvmDumpReferenceTable(&dvmThreadSelf()->internalLocalRefTable, "MAIN");
    }

    /* general debugging setup */
    if (!dvmDebuggerStartup()) {
        return "dvmDebuggerStartup failed";
    }

    if (!dvmGcStartupClasses()) {
        return "dvmGcStartupClasses failed";
    }

    /*
     * Init for either zygote mode or non-zygote mode.  The key difference
     * is that we don‘t start any additional threads in Zygote mode.
     */
    if (gDvm.zygote) {
        if (!initZygote()) {
            return "initZygote failed";
        }
    } else {
        if (!dvmInitAfterZygote()) {
            return "dvmInitAfterZygote failed";
        }
    }


#ifndef NDEBUG
    if (!dvmTestHash())
        ALOGE("dvmTestHash FAILED");
    if (false /*noisy!*/ && !dvmTestIndirectRefTable())
        ALOGE("dvmTestIndirectRefTable FAILED");
#endif

    if (dvmCheckException(dvmThreadSelf())) {
        dvmLogExceptionStackTrace();
        return "Exception pending at end of VM initialization";
    }

    scopedShutdown.disarm();
    return "";
}

dvmStartup主要是启动dalvik虚拟机的各个子模块,具体每个子模块的作用可以参考Dalvik虚拟机的启动过程分析

至此,dalvik虚拟机已经完成了模块初始化。

5.startReg(AndroidRuntime.cpp)

/*
 * Register android native functions with the VM.
 */
/*static*/ int AndroidRuntime::startReg(JNIEnv* env)
{
    /*
     * This hook causes all future threads created in this process to be
     * attached to the JavaVM.  (This needs to go away in favor of JNI
     * Attach calls.)
     */
    androidSetCreateThreadFunc((android_create_thread_fn) javaCreateThreadEtc);

    ALOGV("--- registering native functions ---\n");

    /*
     * Every "register" function calls one or more things that return
     * a local reference (e.g. FindClass).  Because we haven‘t really
     * started the VM yet, they‘re all getting stored in the base frame
     * and never released.  Use Push/Pop to manage the storage.
     */
    env->PushLocalFrame(200);

    if (register_jni_procs(gRegJNI, NELEM(gRegJNI), env) < 0) {
        env->PopLocalFrame(NULL);
        return -1;
    }
    env->PopLocalFrame(NULL);

    //createJavaThread("fubar", quickTest, (void*) "hello");

    return 0;
}

startReg就是注册一些android核心类的native函数。

流程走到这里,dalvik虚拟机已经完成创建和初始化工作,可以开始执行java代码了。

dalvik启动过程

标签:android   虚拟机   dalvik   

原文地址:http://blog.csdn.net/ericming200409/article/details/45581331

(0)
(0)
   
举报
评论 一句话评论(0
登录后才能评论!
© 2014 mamicode.com 版权所有  联系我们:gaon5@hotmail.com
迷上了代码!