Jigsaw Enhancement RFR round #3: 8159145 Add JVMTI function GetNamedModule
Daniel D. Daugherty
daniel.daugherty at oracle.com
Tue Jun 28 18:19:51 UTC 2016
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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