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

[Eric McCorkle]

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/
>