RFR(M): 8081674: EmptyStackException at startup if running with extended or unsupported charset
Mandy Chung
mandy.chung at oracle.com
Tue Jun 9 18:03:02 UTC 2015
Does my patch work fine on 8u? If it works fine, I prefer to get that
simple fix in 8u and take the time to have a better fix in 9 (jdk9 is
still under development and I have assumed that it's not a show stopper
to you. Let me know if it blocks you).
A question to Sherman - do we have adequate tests to verify the move of
System.loadLibrary("zip") from system initialization to ZipFile
initialization for 8u?
Mandy
On 06/09/2015 10:09 AM, Volker Simonis wrote:
> Hi Mandy,
>
> thanks for looking into this.
> Uunfortunately your fix only helps to fix "java -version" :(
>
> Running even a minimal HelloWorld will still fail with the following
> stack trace which is still caused by the same EmptyStackException:
>
> Error: A JNI error has occurred, please check your installation and try again
> Exception in thread "main" java.lang.ExceptionInInitializerError
> at sun.misc.Unsafe.ensureClassInitialized(Native Method)
> at sun.misc.SharedSecrets.getJavaUtilZipFileAccess(SharedSecrets.java:158)
> at sun.misc.URLClassPath$JarLoader.<clinit>(URLClassPath.java:765)
> at sun.misc.URLClassPath$3.run(URLClassPath.java:530)
> at sun.misc.URLClassPath$3.run(URLClassPath.java:520)
> at java.security.AccessController.doPrivileged(Native Method)
> at sun.misc.URLClassPath.getLoader(URLClassPath.java:519)
> at sun.misc.URLClassPath.getLoader(URLClassPath.java:492)
> at sun.misc.URLClassPath.getNextLoader(URLClassPath.java:457)
> at sun.misc.URLClassPath.access$100(URLClassPath.java:64)
> at sun.misc.URLClassPath$1.next(URLClassPath.java:239)
> at sun.misc.URLClassPath$1.hasMoreElements(URLClassPath.java:250)
> at java.net.URLClassLoader$3$1.run(URLClassLoader.java:601)
> at java.net.URLClassLoader$3$1.run(URLClassLoader.java:599)
> at java.security.AccessController.doPrivileged(Native Method)
> at java.net.URLClassLoader$3.next(URLClassLoader.java:598)
> at java.net.URLClassLoader$3.hasMoreElements(URLClassLoader.java:623)
> at sun.misc.CompoundEnumeration.next(CompoundEnumeration.java:45)
> at sun.misc.CompoundEnumeration.hasMoreElements(CompoundEnumeration.java:54)
> at sun.misc.CompoundEnumeration.next(CompoundEnumeration.java:45)
> at sun.misc.CompoundEnumeration.hasMoreElements(CompoundEnumeration.java:54)
> at java.util.ServiceLoader$LazyIterator.hasNextService(ServiceLoader.java:354)
> at java.util.ServiceLoader$LazyIterator.hasNext(ServiceLoader.java:393)
> at java.util.ServiceLoader$1.hasNext(ServiceLoader.java:474)
> at java.nio.charset.Charset$1.getNext(Charset.java:350)
> at java.nio.charset.Charset$1.hasNext(Charset.java:365)
> at java.nio.charset.Charset$2.run(Charset.java:410)
> at java.nio.charset.Charset$2.run(Charset.java:407)
> at java.security.AccessController.doPrivileged(Native Method)
> at java.nio.charset.Charset.lookupViaProviders(Charset.java:406)
> at java.nio.charset.Charset.lookup2(Charset.java:477)
> at java.nio.charset.Charset.lookup(Charset.java:464)
> at java.nio.charset.Charset.isSupported(Charset.java:505)
> at sun.launcher.LauncherHelper.makePlatformString(LauncherHelper.java:580)
> Caused by: java.util.EmptyStackException
> at java.util.Stack.peek(Stack.java:102)
> at java.lang.ClassLoader$NativeLibrary.getFromClass(ClassLoader.java:1759)
> at java.lang.ClassLoader$NativeLibrary.findBuiltinLib(Native Method)
> at java.lang.ClassLoader.loadLibrary0(ClassLoader.java:1870)
> at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1843)
> at java.lang.Runtime.loadLibrary0(Runtime.java:870)
> at java.lang.System.loadLibrary(System.java:1122)
> at java.util.zip.ZipFile.<clinit>(ZipFile.java:86)
> ... 34 more
>
> It's obvious that the way jni_FindClass is looking for the class
> context by calling the NativeLibrary::getFromClass method is hacky but
> I think that the proposed fix is the quite simple and non-intrusive.
> And we probably don't want a complete rework of this code for 8
> anyway. So why not fix it the proposed way in 8 and 9 for now? That
> will still leave us time to come up with a better clean-up at least
> for 9.
>
> What do you think?
>
> Regards,
> Volker
>
> On Tue, Jun 9, 2015 at 1:35 AM, Mandy Chung <mandy.chung at oracle.com> wrote:
>> Hi Volker,
>>
>> Your patch reminds me the question I have about loading zip library.
>>
>> In JDK 9 (and earlier release), zip library is loaded by the VM during
>> startup (see ClassLoader::load_zip_library). I think loadLibrary("zip") is
>> no longer needed to be called from System::initializeSystemClass method and
>> instead it can be loaded by java.util.zip.ZipFile static initializer.
>>
>> Do you mind to try the patch (below)? That may be a simpler fix.
>>
>> I never like the way jni_FindClass to look for the class context by calling
>> the NativeLibrary::getFromClass method. I will have to look deeper other
>> alternative to clean that up. If taking out loadLibrary("zip") resolves
>> your issue, this will give us time to come up with a better clean-up in the
>> future.
>>
>> Mandy
>> [1] https://bugs.openjdk.java.net/browse/JDK-4429040
>>
>> diff --git a/src/share/classes/java/lang/System.java
>> b/src/share/classes/java/lang/System.java
>> --- a/src/share/classes/java/lang/System.java
>> +++ b/src/share/classes/java/lang/System.java
>> @@ -1192,10 +1192,6 @@
>> setOut0(newPrintStream(fdOut,
>> props.getProperty("sun.stdout.encoding")));
>> setErr0(newPrintStream(fdErr,
>> props.getProperty("sun.stderr.encoding")));
>>
>> - // Load the zip library now in order to keep java.util.zip.ZipFile
>> - // from trying to use itself to load this library later.
>> - loadLibrary("zip");
>> -
>> // Setup Java signal handlers for HUP, TERM, and INT (where
>> available).
>> Terminator.setup();
>>
>> diff --git a/src/share/classes/java/util/zip/ZipFile.java
>> b/src/share/classes/java/util/zip/ZipFile.java
>> --- a/src/share/classes/java/util/zip/ZipFile.java
>> +++ b/src/share/classes/java/util/zip/ZipFile.java
>> @@ -83,6 +83,7 @@
>>
>> static {
>> /* Zip library is loaded from System.initializeSystemClass */
>> + System.loadLibrary("zip");
>> initIDs();
>>
>> }
>>
>>
>>
>> On 06/08/2015 07:23 AM, Volker Simonis wrote:
>>> Hi,
>>>
>>> can I please get a review at least for the part of this fix which is
>>> common for jdk8 and jdk9. It's only a few lines in
>>> src/share/vm/prims/jni.cpp for the hotspot repository and one line
>>> src/java.base/share/classes/java/lang/ClassLoader.java for the jdk
>>> repository.
>>>
>>> Thanks,
>>> Volker
>>>
>>>
>>> On Tue, Jun 2, 2015 at 6:12 PM, Volker Simonis <volker.simonis at gmail.com>
>>> wrote:
>>>> Hi,
>>>>
>>>> can I please have review (and a sponsor) for these changes:
>>>>
>>>> https://bugs.openjdk.java.net/browse/JDK-8081674
>>>> http://cr.openjdk.java.net/~simonis/webrevs/2015/8081674.jdk
>>>> http://cr.openjdk.java.net/~simonis/webrevs/2015/8081674.hs
>>>>
>>>> Please notice that the fix requires synchronous changes in the jdk and
>>>> the
>>>> hotspot forest.
>>>>
>>>> The changes themselves are by far not that big as this explanation but I
>>>> found the problem to be quite intricate so I tried to explain it as good
>>>> as
>>>> I could. I'd suggest to read the HTML-formatted explanation in the webrev
>>>> although the content is equal to the one in this mail:
>>>>
>>>> Using an unsupported character encoding (e.g. vi_VN.TCVN on Linux)
>>>> results
>>>> in an immediate VM failure with jdk 8 and 9:
>>>>
>>>> export LANG=vi_VN.TCVN
>>>> java -version
>>>> Error occurred during initialization of VM
>>>> java.util.EmptyStackException
>>>> at java.util.Stack.peek(Stack.java:102)
>>>> at
>>>> java.lang.ClassLoader$NativeLibrary.getFromClass(ClassLoader.java:1751)
>>>> at java.lang.ClassLoader$NativeLibrary.findBuiltinLib(Native
>>>> Method)
>>>> at java.lang.ClassLoader.loadLibrary0(ClassLoader.java:1862)
>>>> at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1835)
>>>> at java.lang.Runtime.loadLibrary0(Runtime.java:870)
>>>> at java.lang.System.loadLibrary(System.java:1119)
>>>> at java.lang.System.initializeSystemClass(System.java:1194)
>>>>
>>>> This is a consequence of "8005716: Enhance JNI specification to allow
>>>> support of static JNI libraries in Embedded JREs".
>>>>
>>>> With jdk 9 we get this error even if we're running with a supported
>>>> charset
>>>> which is in the ExtendedCharsets (as opposed to being in the
>>>> StandardCharsets) class which is a consequence of delegating the loading
>>>> of
>>>> the ExtendedCharsets class to the ServiceLoader in jdk 9.
>>>>
>>>> export LANG=eo.iso-8859-3
>>>> output-jdk9/images/jdk/bin/java -version
>>>> Error occurred during initialization of VM
>>>> java.util.EmptyStackException
>>>> at java.util.Stack.peek(Stack.java:102)
>>>> at
>>>> java.lang.ClassLoader$NativeLibrary.getFromClass(ClassLoader.java:1737)
>>>> at java.lang.ClassLoader$NativeLibrary.findBuiltinLib(Native
>>>> Method)
>>>> at java.lang.ClassLoader.loadLibrary0(ClassLoader.java:1866)
>>>> at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1840)
>>>> at java.lang.Runtime.loadLibrary0(Runtime.java:874)
>>>> at java.lang.System.loadLibrary(System.java:1111)
>>>> at java.lang.System.initializeSystemClass(System.java:1186)
>>>>
>>>> Here's why the exception happens for an unsupported charset (see the
>>>> mixed
>>>> stack trace below for the full details):
>>>>
>>>> java.lang.System.loadLibrary() wants to load libzip.so. It calls
>>>> java.lang.Runtime.loadLibrary0() which at the very beginning calls the
>>>> native method ClassLoader$NativeLibrary.findBuiltinLib() which checks if
>>>> the
>>>> corresponding library is already statically linked into the VM
>>>> (introduced
>>>> by 8005716).
>>>> Java_java_lang_ClassLoader_00024NativeLibrary_findBuiltinLib(),
>>>> the native implementation of findBuiltinLib() in Classloader.c calls
>>>> GetStringPlatformChars() to convert the library name into the native
>>>> platform encoding. GetStringPlatformChars() calls the helper function
>>>> jnuEncodingSupported() to check if the platform encoding which is stored
>>>> in
>>>> the property "sun.jnu.encoding" is supported by Java.
>>>> jnuEncodingSupported()
>>>> is implemented as follows:
>>>>
>>>> static jboolean isJNUEncodingSupported = JNI_FALSE;
>>>> static jboolean jnuEncodingSupported(JNIEnv *env) {
>>>> jboolean exe;
>>>> if (isJNUEncodingSupported == JNI_TRUE) {
>>>> return JNI_TRUE;
>>>> }
>>>> isJNUEncodingSupported = (jboolean) JNU_CallStaticMethodByName (
>>>> env, &exe,
>>>> "java/nio/charset/Charset",
>>>> "isSupported",
>>>> "(Ljava/lang/String;)Z",
>>>> jnuEncoding).z;
>>>> return isJNUEncodingSupported;
>>>> }
>>>>
>>>> Once the function finds that the platform encoding is supported (by
>>>> calling
>>>> java.nio.charset.Charset.isSupported()) it caches this value and always
>>>> returns it on following calls. However if the platform encoding is not
>>>> supported, it ALWAYS calls java.nio.charset.Charset.isSupported() an
>>>> every
>>>> subsequent invocation.
>>>>
>>>> In order to call the Java method Charset.isSupported() (in
>>>> JNU_CallStaticMethodByName() in file jni_util.c), we have to call
>>>> jni_FindClass() to convert the symbolic class name
>>>> "java.nio.charset.Charset" into a class reference.
>>>>
>>>> But unfortunately, jni_FindClass() (from jni.cpp in libjvm.so) has a
>>>> special
>>>> handling if called from java.lang.ClassLoader$NativeLibrary to ensure
>>>> that
>>>> JNI_OnLoad/JNI_OnUnload are executed in the correct class context:
>>>>
>>>> instanceKlassHandle k (THREAD, thread->security_get_caller_class(0));
>>>> if (k.not_null()) {
>>>> loader = Handle(THREAD, k->class_loader());
>>>> // Special handling to make sure JNI_OnLoad and JNI_OnUnload are
>>>> executed
>>>> // in the correct class context.
>>>> if (loader.is_null() &&
>>>> k->name() == vmSymbols::java_lang_ClassLoader_NativeLibrary()) {
>>>> JavaValue result(T_OBJECT);
>>>> JavaCalls::call_static(&result, k,
>>>> vmSymbols::getFromClass_name(),
>>>> vmSymbols::void_class_signature(),
>>>> thread);
>>>> if (HAS_PENDING_EXCEPTION) {
>>>> Handle ex(thread, thread->pending_exception());
>>>> CLEAR_PENDING_EXCEPTION;
>>>> THROW_HANDLE_0(ex);
>>>> }
>>>>
>>>> So if that's the case and jni_FindClass() was reallycalled from
>>>> ClassLoader$NativeLibrary, then jni_FindClass() calles
>>>> ClassLoader$NativeLibrary().getFromClass() to find out the corresponding
>>>> context class which is supposed to be saved there in a field of type
>>>> java.util.Stack named "nativeLibraryContext":
>>>>
>>>> // Invoked in the VM to determine the context class in
>>>> // JNI_Load/JNI_Unload
>>>> static Class<?> getFromClass() {
>>>> return ClassLoader.nativeLibraryContext.peek().fromClass;
>>>> }
>>>>
>>>> Unfortunately, "nativeLibraryContext" doesn't contain any entry at this
>>>> point and the invocation of Stack.peek() will throw the exception shown
>>>> before. In general, the "nativeLibraryContext" stack will be filled later
>>>> on
>>>> in Runtime.loadLibrary0() like this:
>>>>
>>>> NativeLibrary lib = new NativeLibrary(fromClass, name, isBuiltin);
>>>> nativeLibraryContext.push(lib);
>>>> try {
>>>> lib.load(name, isBuiltin);
>>>> } finally {
>>>> nativeLibraryContext.pop();
>>>> }
>>>>
>>>> such that it always contains at least one element later when
>>>> jni_FindClass()
>>>> will be invoked.
>>>>
>>>> So in summary, the problem is that the implementors of 8005716 didn't
>>>> took
>>>> into account that calling ClassLoader$NativeLibrary.findBuiltinLib() may
>>>> trigger a call to jni_FindClass() if we are running on a system with an
>>>> unsupported character encoding.
>>>>
>>>> I'd suggest the following fix for this problem:
>>>>
>>>> Change ClassLoader$NativeLibrary().getFromClass() to return null if the
>>>> stack is empty instead of throwing an exception:
>>>>
>>>> static Class<?> getFromClass() {
>>>> return ClassLoader.nativeLibraryContext.empty() ?
>>>> null : ClassLoader.nativeLibraryContext.peek().fromClass;
>>>> }
>>>>
>>>> Unfortunately this also requires a HotSpot change in jni_FindClass() in
>>>> order to properly handle the new 'null' return value:
>>>>
>>>> if (k.not_null()) {
>>>> loader = Handle(THREAD, k->class_loader());
>>>> // Special handling to make sure JNI_OnLoad and JNI_OnUnload are
>>>> executed
>>>> // in the correct class context.
>>>> if (loader.is_null() &&
>>>> k->name() == vmSymbols::java_lang_ClassLoader_NativeLibrary()) {
>>>> JavaValue result(T_OBJECT);
>>>> JavaCalls::call_static(&result, k,
>>>> vmSymbols::getFromClass_name(),
>>>> vmSymbols::void_class_signature(),
>>>> thread);
>>>> if (HAS_PENDING_EXCEPTION) {
>>>> Handle ex(thread, thread->pending_exception());
>>>> CLEAR_PENDING_EXCEPTION;
>>>> THROW_HANDLE_0(ex);
>>>> }
>>>> oop mirror = (oop) result.get_jobject();
>>>> if (oopDesc::is_null(mirror)) {
>>>> loader = Handle(THREAD, SystemDictionary::java_system_loader());
>>>> } else {
>>>> loader = Handle(THREAD,
>>>>
>>>> InstanceKlass::cast(java_lang_Class::as_Klass(mirror))->class_loader());
>>>> protection_domain = Handle(THREAD,
>>>>
>>>>
>>>> InstanceKlass::cast(java_lang_Class::as_Klass(mirror))->protection_domain());
>>>> }
>>>> }
>>>> } else {
>>>> // We call ClassLoader.getSystemClassLoader to obtain the system
>>>> class
>>>> loader.
>>>> loader = Handle(THREAD, SystemDictionary::java_system_loader());
>>>> }
>>>>
>>>> These changes are sufficient to solve the problem in Java 8.
>>>> Unfortunately,
>>>> that's still not enough in Java 9 because there the loading of the
>>>> extended
>>>> charsets has been delegated to ServiceLoader. But ServiceLoader calls
>>>> ClassLoader.getBootstrapResources() which calls
>>>> sun.misc.Launcher.getBootstrapClassPath(). This leads to another problem
>>>> during class initialization of sun.misc.Launcher if running on an
>>>> unsupported locale.
>>>>
>>>> The first thing done in sun.misc.Launcher.<clinit> is the initialisation
>>>> of
>>>> the bootstrap URLClassPath in the Launcher. However this initialisation
>>>> will
>>>> eventually call Charset.isSupported() and if we are running on an
>>>> unsupported locale this will inevitably end in another recursive call to
>>>> ServiceLoader. But as explained below, ServiceLoader will query the
>>>> Launcher's bootstrap URLClassPath which will be still uninitialized at
>>>> that
>>>> point.
>>>>
>>>> So we'll have to additionally guard guard against this situation on JDK 9
>>>> like this:
>>>>
>>>> private static Charset lookupExtendedCharset(String charsetName) {
>>>> if (!sun.misc.VM.isBooted() || // see
>>>> lookupViaProviders()
>>>> sun.misc.Launcher.getBootstrapClassPath() == null)
>>>> return null;
>>>>
>>>> This fixes the crashes, but still at the price of not having the extended
>>>> charsets available during initialization until
>>>> Launcher.getBootstrapClassPath is set up properly. This may be still a
>>>> problem if the jdk is installed in a directory which contains characters
>>>> specific to an extended encoding or if we have such characters in the
>>>> command line arguments.
>>>>
>>>> Thank you and best regards,
>>>> Volker
>>>>
>>>>
>>>> Mixed stack trace of the initial EmptyStackException for unsupported
>>>> charsets described before:
>>>>
>>>> Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native
>>>> code)
>>>> j java.util.Stack.peek()Ljava/lang/Object;+1
>>>> j java.lang.ClassLoader$NativeLibrary.getFromClass()Ljava/lang/Class;+3
>>>> v ~StubRoutines::call_stub
>>>> V [libjvm.so+0x9d279a] JavaCalls::call_helper(JavaValue*,
>>>> methodHandle*,
>>>> JavaCallArguments*, Thread*)+0x6b4
>>>> V [libjvm.so+0xcad591] os::os_exception_wrapper(void (*)(JavaValue*,
>>>> methodHandle*, JavaCallArguments*, Thread*), JavaValue*, methodHandle*,
>>>> JavaCallArguments*, Thread*)+0x45
>>>> V [libjvm.so+0x9d20cf] JavaCalls::call(JavaValue*, methodHandle,
>>>> JavaCallArguments*, Thread*)+0x8b
>>>> V [libjvm.so+0x9d1d3b] JavaCalls::call_static(JavaValue*, KlassHandle,
>>>> Symbol*, Symbol*, JavaCallArguments*, Thread*)+0x139
>>>> V [libjvm.so+0x9d1e3f] JavaCalls::call_static(JavaValue*, KlassHandle,
>>>> Symbol*, Symbol*, Thread*)+0x9d
>>>> V [libjvm.so+0x9e6588] jni_FindClass+0x428
>>>> C [libjava.so+0x20208] JNU_CallStaticMethodByName+0xff
>>>> C [libjava.so+0x21cae] jnuEncodingSupported+0x61
>>>> C [libjava.so+0x22125] JNU_GetStringPlatformChars+0x125
>>>> C [libjava.so+0xedcd]
>>>> Java_java_lang_ClassLoader_00024NativeLibrary_findBuiltinLib+0x8b
>>>> j
>>>>
>>>> java.lang.ClassLoader$NativeLibrary.findBuiltinLib(Ljava/lang/String;)Ljava/lang/String;+0
>>>> j java.lang.ClassLoader.loadLibrary0(Ljava/lang/Class;Ljava/io/File;)Z+4
>>>> j
>>>>
>>>> java.lang.ClassLoader.loadLibrary(Ljava/lang/Class;Ljava/lang/String;Z)V+228
>>>> j
>>>> java.lang.Runtime.loadLibrary0(Ljava/lang/Class;Ljava/lang/String;)V+54
>>>> j java.lang.System.loadLibrary(Ljava/lang/String;)V+7
>>>> j java.lang.System.initializeSystemClass()V+113
>>>> v ~StubRoutines::call_stub
>>>> V [libjvm.so+0x9d279a] JavaCalls::call_helper(JavaValue*,
>>>> methodHandle*,
>>>> JavaCallArguments*, Thread*)+0x6b4
>>>> V [libjvm.so+0xcad591] os::os_exception_wrapper(void (*)(JavaValue*,
>>>> methodHandle*, JavaCallArguments*, Thread*), JavaValue*, methodHandle*,
>>>> JavaCallArguments*, Thread*)+0x45
>>>> V [libjvm.so+0x9d20cf] JavaCalls::call(JavaValue*, methodHandle,
>>>> JavaCallArguments*, Thread*)+0x8b
>>>> V [libjvm.so+0x9d1d3b] JavaCalls::call_static(JavaValue*, KlassHandle,
>>>> Symbol*, Symbol*, JavaCallArguments*, Thread*)+0x139
>>>> V [libjvm.so+0x9d1e3f] JavaCalls::call_static(JavaValue*, KlassHandle,
>>>> Symbol*, Symbol*, Thread*)+0x9d
>>>> V [libjvm.so+0xe3cceb] call_initializeSystemClass(Thread*)+0xb0
>>>> V [libjvm.so+0xe44444]
>>>> Threads::initialize_java_lang_classes(JavaThread*,
>>>> Thread*)+0x21a
>>>> V [libjvm.so+0xe44b12] Threads::create_vm(JavaVMInitArgs*, bool*)+0x4a6
>>>> V [libjvm.so+0xa19bd7] JNI_CreateJavaVM+0xc7
>>>> C [libjli.so+0xa520] InitializeJVM+0x154
>>>> C [libjli.so+0x8024] JavaMain+0xcc
>>>>
>>>>
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