Review request for 8058313: Mismatch of method descriptor and MethodParameters.parameters_count should cause MalformedParameterException

[Eric McCorkle]

Please review this issue so that it can go in along with 8058322.  Thanks.

On 10/30/14 19:40, Eric McCorkle wrote:
> Thank you for the pointers.  I have applied your changes and refreshed
> the webrev.
> 
> http://cr.openjdk.java.net/~emc/8058313/
> 
> Also, I have posted the test for this and another patch here:
> http://cr.openjdk.java.net/~emc/8062556/
> 
> On 10/30/14 13:51, Jiangli Zhou wrote:
>> Hi Eric,
>>
>> On 10/30/2014 07:56 AM, Eric McCorkle wrote:
>>> On 10/29/14 20:36, Jiangli Zhou wrote:
>>>> Hi Eric,
>>>>
>>>> I wonder if we could specialize this particular case and avoid changing
>>>> the parsing code.  How about setting the _has_method_parameters flag in
>>>> the ConstMethod when encounter such MethodParameter, and changing
>>>> JVM_GetMethodParameters() to return non-NULL value for such case when
>>>> _has_method_parameters is true but method_parameters_length is 0. Would
>>>> that work?
>>> Which parser are you talking about?  The inline tables parser, or the
>>> class file parser.  The class file parser has to change, because it was
>>> previously ignoring MethodParameters attributes with parameter_count 0.
>>
>> It's the class parsing changes that I was referring to, mostly relate to
>> the initialization and checking against method_parameters_length. It's a
>> bit awkward to include the 0 case but also skipping it in the loop. For
>> example, the following code in classFileParser.cpp changed ">" to ">="
>> in the if check, but has no real effect and is not need.
>>
>> 2486   // Copy method parameters
>> 2487   if (method_parameters_length >= 0) {
>> 2488     MethodParametersElement* elem =
>> m->constMethod()->method_parameters_start();
>> 2489     for (int i = 0; i < method_parameters_length; i++) {
>> 2490       elem[i].name_cp_index =
>> Bytes::get_Java_u2(method_parameters_data);
>> 2491       method_parameters_data += 2;
>> 2492       elem[i].flags = Bytes::get_Java_u2(method_parameters_data);
>> 2493       method_parameters_data += 2;
>> 2494     }
>> 2495   }
>>
>>
>>>
>>> I don't think your proposal will work.  The inline tables' offsets are
>>> all dependent on what inline tables are actually present.  If
>>> _has_method_parameters is set, then the inline tables code expects the
>>> last u2 of the inline tables to be a u2 indicating the number of method
>>> parameters entries, preceeded by the array of method parameters data.
>>> If _has_method_parameters is false, then it expects that there is no
>>> method parameters information at all (including no length field).  If
>>> you were to set _has_method_parameters, but not store any information in
>>> the inline table, then it would cause errors for all the rest of the
>>> inline tables.
>>
>> Thank you for reminding me of the complexity of the inlined table
>> calculation in the ConstMethod. My proposal would require tweaks in that
>> area to correctly compute the table sizes. As it's easy to introduce
>> bugs in that area, it's not worth to change the table calculation code
>> for this purpose. I agree my proposal is not a better choice in this case.
>>
>>>    What I do for the parameter_count = 0 case is just store
>>> a 0 u2 for zero-length method parameters information, and no data.  All
>>> the existing inline tables code works fine with this case, so there
>>> aren't any serious changes to the inline tables code (other than
>>> allowing method parameters information to be stored when the array is
>>> length 0).  But you have to make some change to the inline table code,
>>> otherwise the information won't be stored.
>>
>> Ok. Could you please add comments to the change in constMethod.cpp to
>> explain above?
>>
>> In jvm.cpp, since -1 represents no method parameter now. Maybe checking
>> against explicity and add comments for the 0-length case.
>>
>> JVM_ENTRY(jobjectArray, JVM_GetMethodParameters(JNIEnv *env, jobject
>> method))
>> {
>> ...
>>   // No method parameter
>>   if (num_params == -1) {
>>     return (jobjectArray)NULL;
>>   }
>>
>>   /* handle the rest here */
>>   // make sure all the symbols are properly formatted
>>   for (int i = 0; i < num_params; i++) {
>>   ...
>> }
>>
>> Thanks,
>> Jiangli
>>
>>>
>>>> Thanks,
>>>> Jiangli
>>>>
>>>> On 10/29/2014 03:39 PM, Eric McCorkle wrote:
>>>>> Hello,
>>>>>
>>>>> Please review this fix for parameter reflection which addresses hotspot
>>>>> falsely ignoring zero-length MethodParameter attributes.  The JVMS
>>>>> allows a MethodParameters attribute with parameter_count = 0, and the
>>>>> parameter reflection spec states that a MalformedParametersException
>>>>> should be thrown if parameter_count does not match the number of real
>>>>> parameters to a method.  Hotspot currently ignores MethodParameters
>>>>> attributes with parameter_count = 0; however, in a case where a (bad)
>>>>> MethodParameters attribute has parameter_count = 0, but the method
>>>>> has a
>>>>> nonzero number of real parameters, hotspot will return null from
>>>>> JVM_GetMethodParameters, the result being that a
>>>>> MalformedParametersException is not thrown (rather, the reflection API
>>>>> acts like there is no MethodParameters attribute).
>>>>>
>>>>> This patch causes hotspot to record the fact that a zero-length
>>>>> MethodParameters attribute does exist, causing the exception to be
>>>>> thrown when it should be.
>>>>>
>>>>> The bug is here:
>>>>> https://bugs.openjdk.java.net/browse/JDK-8058313
>>>>>
>>>>> The webrev is here:
>>>>> http://cr.openjdk.java.net/~emc/8058313/
>>