Jigsaw Enhancement RFR round #3: 8159145 Add JVMTI function GetNamedModule
David Holmes
david.holmes at oracle.com
Wed Jun 29 02:17:34 UTC 2016
Hi Serguei,
Looks good to me. A couple of comments ...
On 29/06/2016 6:42 AM, serguei.spitsyn at oracle.com wrote:
> Dan,
>
> The updated webrev:
> http://cr.openjdk.java.net/~sspitsyn/webrevs/2016/hotspot/8159145-jigsaw-jvmti-pkg.6/
src/share/vm/classfile/modules.cpp
Nit:
+ const PackageEntry* const pkg_entry =
+ get_package_entry_by_name(package_sym, h_loader, THREAD);
indent on a line continuation should be 4 not 2. (no need to see updated
webrev).
---
src/share/vm/prims/jvmti.xml
+ or points to <code>NULL</code>.
I would have suggested "or is <code>NULL</code>." as per other email,
but I see that this terminology is pre-existing, so ignore that other email.
>
>
>> Has someone checked the generated glue code for completeness and
> proper checks?
>
> This is the generated upper layer function in the jvmtiEnter.cpp:
>
> 3185 static jvmtiError JNICALL
> 3186 jvmti_GetNamedModule(jvmtiEnv* env,
> 3187 jobject class_loader,
> 3188 const char* package_name,
> 3189 jobject* module_ptr) {
> 3190
> 3191 #if !INCLUDE_JVMTI
> 3192 return JVMTI_ERROR_NOT_AVAILABLE;
> 3193 #else
> 3194 if(!JvmtiEnv::is_vm_live()) {
> 3195 return JVMTI_ERROR_WRONG_PHASE;
> 3196 }
> 3197 Thread* this_thread = Thread::current_or_null();
> 3198 if (this_thread == NULL || !this_thread->is_Java_thread()) {
> 3199 return JVMTI_ERROR_UNATTACHED_THREAD;
> 3200 }
> 3201 JavaThread* current_thread = (JavaThread*)this_thread;
> 3202 ThreadInVMfromNative __tiv(current_thread);
> 3203 VM_ENTRY_BASE(jvmtiError, jvmti_GetNamedModule , current_thread)
> 3204 debug_only(VMNativeEntryWrapper __vew;)
> 3205 CautiouslyPreserveExceptionMark __em(this_thread);
> 3206 JvmtiEnv* jvmti_env = JvmtiEnv::JvmtiEnv_from_jvmti_env(env);
> 3207 if (!jvmti_env->is_valid()) {
> 3208 return JVMTI_ERROR_INVALID_ENVIRONMENT;
> 3209 }
> 3210 jvmtiError err;
> 3211 if (package_name == NULL) {
> 3212 return JVMTI_ERROR_NULL_POINTER;
> 3213 }
> 3214 if (module_ptr == NULL) {
> 3215 return JVMTI_ERROR_NULL_POINTER;
> 3216 }
> 3217 err = jvmti_env->GetNamedModule(class_loader, package_name,
> module_ptr);
> 3218 return err;
> 3219 #endif // INCLUDE_JVMTI
> 3220 }
>
>
> I do not see any problems in the above.
Looks good to me too.
Thanks,
David
>
> Thanks,
> Serguei
>
>
>
>
> On 6/28/16 11:19, Daniel D. Daugherty wrote:
>> On 6/28/16 10:37 AM, serguei.spitsyn at oracle.com wrote:
>>> Hi Harold,
>>>
>>> Thank you again for the comments!
>>> This is the updated webrev:
>>> http://cr.openjdk.java.net/~sspitsyn/webrevs/2016/hotspot/8159145-jigsaw-jvmti-pkg.5/
>>>
>>
>> make/test/JtregNative.gmk
>> No comments.
>>
>> src/share/vm/classfile/modules.hpp
>> No comments.
>>
>> src/share/vm/classfile/modules.cpp
>> L826: assert(h_loader.is_null() ||
>> java_lang_ClassLoader::is_subclass(h_loader->klass()),
>> L827: "Class loader is not a subclass of
>> java.lang.ClassLoader");
>> nit: indent on L827 is off by 1 space
>>
>> I'll have to check the upper layers of this API, but if an
>> agent can pass a bad 'class_loader' parameter and get this
>> assert() to fire, then that's not good. Hopefully a bad
>> 'class_loader' parameter is caught at a higher layer.
>>
>> Update: Yes, passing a non-NULL jobject as the class_loader
>> parameter
>> when the jobject does not refer to a "class loader" is caught
>> at the upper layer.
>>
>> L828: assert(package_str != NULL, "the package_str should not be
>> NULL");
>> Same concern about the package_str parameter.
>>
>> Update: Yes, the generated JVM/TI glue code should catch a
>> NULL package_name/package_str at the upper layers.
>>
>>
>> src/share/vm/prims/jvmti.xml
>> L6550: <param id="module_ptr">
>> L6551: <outptr><jobject/></outptr>
>> L6552: <description>
>> L6553: On return, points to a
>> <code>java.lang.reflect.Module</code> object.
>> L6554: </description>
>> L6555: </param>
>>
>> The above wording doesn't allow for module_ptr to be NULL which
>> is a mismatch with the description.
>>
>> L2518: function can be used to map class loader and package
>> name to a module.
>> Typo: 'map class loader and package name'
>> -> 'map a class loader and a package name'
>>
>>
>> src/share/vm/prims/jvmtiEnv.cpp
>> L204: // class_loader - NULL is a valid value, must be pre-checked
>> L205: // package_name - pre-checked for NULL
>> L206: // module_ptr - pre-checked for NULL
>> The jvmti.xml file doesn't mark package_name or module_ptr
>> with <nullok> so both of those should be checked by the
>> generated glue code.
>>
>> class_loader is marked with <nullok> so a NULL class_loader
>> will get to here:
>>
>> L217: jobject module = Modules::get_named_module(h_loader,
>> package_name, THREAD);
>>
>> and it looks like all the code paths in get_named_module()
>> properly account for both NULL and non-NULL h_loader. Cool.
>>
>> test/serviceability/jvmti/GetNamedModule/MyPackage/GetNamedModuleTest.java
>>
>> L42: System.err.println("java.library.path:"
>> nit: a space between the ':' and '"' would make the
>> output more readable
>>
>> test/serviceability/jvmti/GetNamedModule/libGetNamedModuleTest.c
>> L81: res = JNI_ENV_PTR(jvm)->GetEnv(JNI_ENV_ARG(jvm, (void **)
>> &jvmti),
>> L82: JVMTI_VERSION_1_1);
>> I was expecting this test to ask for the JVM/TI version that
>> includes support for GetAllModules() and GetNamesModule().
>> Looks like that is version 9.0.0 or newer aka JVMTI_VERSION_9.
>>
>> L360: if (module != NULL || mod_name !=NULL) {
>> bit: space after '!=' and before NULL
>>
>> Has someone checked the generated glue code for completeness and
>> proper checks?
>>
>> Dan
>>
>>
>>>
>>> Thanks,
>>> Serguei
>>>
>>>
>>> On 6/28/16 07:32, harold seigel wrote:
>>>>
>>>> Hi Serguei,
>>>>
>>>> Looks good.
>>>>
>>>> 1. In modules.cpp, the first assert in get_named_module() has the
>>>> wrong function name:
>>>>
>>>> 825 assert(ModuleEntryTable::javabase_defined(),
>>>> 826 "Attempt to call *get_module_by_package_name* before java.base
>>>> is defined");
>>>>
>>>> 2. Also, is a check needed to ensure that package_str is not null?
>>>>
>>>> 3. Is the ResourceMark(THREAD) needed at line 824?
>>>>
>>>> Thanks, Harold
>>>>
>>>> On 6/28/2016 4:54 AM, serguei.spitsyn at oracle.com wrote:
>>>>> Hi David,
>>>>>
>>>>> Thank you for the comments!
>>>>> I agree with you.
>>>>>
>>>>> Updated Hotspot webrev:
>>>>> http://cr.openjdk.java.net/~sspitsyn/webrevs/2016/hotspot/8159145-jigsaw-jvmti-pkg.4/
>>>>>
>>>>>
>>>>>
>>>>> Thanks,
>>>>> Serguei
>>>>>
>>>>>
>>>>>
>>>>> On 6/27/16 22:06, David Holmes wrote:
>>>>>> Hi Serguei,
>>>>>>
>>>>>> Overall this looks a lot clearer/simpler.
>>>>>>
>>>>>> On 28/06/2016 2:20 PM, serguei.spitsyn at oracle.com wrote:
>>>>>>> On 6/27/16 21:08, serguei.spitsyn at oracle.com wrote:
>>>>>>>> Please, review the Jigsaw fix for the enhancement:
>>>>>>>> https://bugs.openjdk.java.net/browse/JDK-8159145
>>>>>>>>
>>>>>>>>
>>>>>>>> The Hotspot webrev:
>>>>>>>>
>>>>>>>> http://cr.openjdk.java.net/~sspitsyn/webrevs/2016/hotspot/8159145-jigsaw-jvmti-pkg.3/
>>>>>>>>
>>>>>>
>>>>>> Are there intended to be other callers of
>>>>>> Module::get_named_module? If not it seems odd to go to all the
>>>>>> trouble of throwing exceptions, just to have the caller clear them
>>>>>> and return an error code. Or you could move all that argument
>>>>>> checking code into the JVMTI function directly - if called
>>>>>> internally you would just assert that arguments are as expected.
>>>>>>
>>>>>>
>>>>>> src/share/vm/prims/jvmti.xml
>>>>>>
>>>>>> + otherwise the <code>NULL</code> is returned.
>>>>>>
>>>>>> Delete "the".
>>>>>>
>>>>>> Otherwise all looks good to me.
>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> The Jdk webrev is the same:
>>>>>>>>
>>>>>>>> http://cr.openjdk.java.net/~sspitsyn/webrevs/2016/hotspot/8159145-jigsaw-jvmti-pkg.jdk1/
>>>>>>>>
>>>>>>>
>>>>>>> Sorry, the Jdk webrev changed as well:
>>>>>>>
>>>>>>> http://cr.openjdk.java.net/~sspitsyn/webrevs/2016/hotspot/8159145-jigsaw-jvmti-pkg.jdk3/
>>>>>>>
>>>>>>
>>>>>> Looks fine.
>>>>>>
>>>>>> Thanks,
>>>>>> David
>>>>>>
>>>>>>>
>>>>>>> Thanks,
>>>>>>> Serguei
>>>>>>>
>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> Summary:
>>>>>>>>
>>>>>>>> This is the review round #3.
>>>>>>>> Alan suggested to replace the function GetModuleByPackageName
>>>>>>>> with
>>>>>>>> the GetNamedModule.
>>>>>>>> New function will return NULL if the package is not in a module
>>>>>>>> defined to the class loader.
>>>>>>>> It simplifies the API and makes it easier to specify.
>>>>>>>> JVM TI agents that instrument code in named modules need the
>>>>>>>> Module
>>>>>>>> at class load time.
>>>>>>>>
>>>>>>>> One question that came from the function semantics change.
>>>>>>>> I had to implement the Modules::get_named_module() from scratch
>>>>>>>> independently of the existing
>>>>>>>> Modules::get_module_by_package_name() and Modules::get_module().
>>>>>>>> The issue is that the Modules::get_module() can return the
>>>>>>>> unnamed
>>>>>>>> module whereas the
>>>>>>>> JVMTI helper Modules::get_named_module() should return NULL
>>>>>>>> instead
>>>>>>>> of the unnamed module.
>>>>>>>> Please, let me know if it is Ok or if you have better ideas
>>>>>>>> how to
>>>>>>>> share the code.
>>>>>>>>
>>>>>>>> This is the Summary from review round #1:
>>>>>>>>
>>>>>>>> One way to do this is by introducing a new ClassFileLoadHook that
>>>>>>>> takes an additional parameter but this approach is disruptive.
>>>>>>>> The alternative option is a JVM TI function that maps a
>>>>>>>> classloader
>>>>>>>> + package name to a module.
>>>>>>>> We were initially not confident with this approach so we
>>>>>>>> introduced
>>>>>>>> it as JVM function JVM_GetModuleByPackageName.
>>>>>>>> Based on experience to date then this approach seems okay and so
>>>>>>>> this function needs to be promoted to a JVMTI function.
>>>>>>>>
>>>>>>>> It includes new jtreg test with native JVMTI agent.
>>>>>>>>
>>>>>>>>
>>>>>>>> Testing:
>>>>>>>> Run newly developed jtreg test.
>>>>>>>>
>>>>>>>> Thanks,
>>>>>>>> Serguei
>>>>>>>
>>>>>
>>>>
>>>
>>
>
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