[Nestmates] RFR (S): 8197915: [Nestmates] Implement receiver typecheck for private invokeinterface use
David Holmes
david.holmes at oracle.com
Fri May 4 07:24:23 UTC 2018
On 4/05/2018 5:10 PM, David Holmes wrote:
> On 4/05/2018 5:04 PM, Vladimir Ivanov wrote:
>>
>>>> http://cr.openjdk.java.net/~dholmes/8197915/webrev.v2/
>>
>> src/java.base/share/classes/java/lang/invoke/DirectMethodHandle.java
>>
>> + LambdaForm lform = preparedLambdaForm(member,
>> callerClass.isInterface());
>>
>> You need to handle "callerClass == null" case as well.
>
> I'm not sure I do now. I think we must always have a callerClass context
> when we hit this code. Can you see where a null may come from? So far
> testing has not produced any failures relating to a null callerClass. If
> we did ever get a null we'd be missing the receiver <: caller check, and
> that would be a bug requiring us to change the code to pass in the caller.
Just realized this is inconsistent with the immediately following:
if (callerClass != null) {
checkClass = callerClass; // potentially strengthen to caller class
}
So I'll have to change one of them. But I'd still prefer that the
callerClass can not be null.
Cheers,
David
> Thanks,
> David
>
>> Best regards,
>> Vladimir Ivanov
>>
>>>>
>>>> Changes:
>>>>
>>>> - DirectMethodHandles.java: new simple and direct approach to
>>>> dealing with LF_SPECIAL_IFC
>>>
>>> I like how java.lang.invoke part shapes out!
>>>
>>> Maybe rename adaptToSpecialIfc to needsReceiverCheck? That's what
>>> confused me in the first version: though it's an interface call
>>> (which always require receiver check against REFC), new checks only
>>> referred to LF_INVSPECIAL (since invocation mode is a direct call).
>>>
>>>> - New regression test for the final virtual call from an interface
>>>> bug introduced by 8200167.
>>>>
>>>> If necessary/desirable I can fix that part in mainline separately.
>>>> So far no tests (including jck/API/java/lang) seem to tickle it.
>>>
>>> Or file a bug. I have some ideas how to improve relevant code and
>>> make LF construction cleaner.
>>>
>>> Best regards,
>>> Vladimir Ivanov
>>>
>>>
>>>> Thanks,
>>>> David
>>>>
>>>> On 4/05/2018 11:41 AM, David Holmes wrote:
>>>>> Hi Karen,
>>>>>
>>>>> On 4/05/2018 6:39 AM, Karen Kinnear wrote:
>>>>>> David,
>>>>>>
>>>>>> Really delighted to see you near the end of the major functional
>>>>>> changes!
>>>>>
>>>>> Thanks for taking a look so quickly!
>>>>>
>>>>>> A couple minor comments, and then a question please:
>>>>>>
>>>>>> 1. MethodHandles.java
>>>>>
>>>>> DirectMethodHandle.java :)
>>>>>
>>>>>> 174 different “to” -> different “from” ?
>>>>>
>>>>> Changed. That's my UK upbringing :)
>>>>>
>>>>> https://en.oxforddictionaries.com/usage/different-from-than-or-to
>>>>>
>>>>>> 2. methodHandles.cpp
>>>>>> 300-301
>>>>>> Thank you for the comment.
>>>>>> Might it also be worth adding that direct call is used by:
>>>>>> invoke static, invokespecial, invokeinterface:local private,
>>>>>> invoke virtual:vfinal and private methods
>>>>>> (or are you concerned about getting out of sync if this changes?)
>>>>>
>>>>> It is not used by invokestatic. I'm not 100% sure of all the exact
>>>>> cases where an invokeinterface/invokevirtual becomes a direct call,
>>>>> so didn't want to say anything inaccurate. But the comment as it
>>>>> stands is awkward so I've expanded it:
>>>>>
>>>>> // "special" reflects that this is a direct call, not that it
>>>>> // necessarily originates from an invokespecial. We can also do
>>>>> // direct calls for private and/or final non-static methods.
>>>>>
>>>>>> 3. DirectMethodHandle.java - this was subtle!
>>>>>
>>>>> More than you realise ;-)
>>>>>
>>>>>> I believe this is correct assuming that:
>>>>>> CallerClass is always and only set for invokespecial. Is this
>>>>>> accurate? Could you possibly add a comment?
>>>>>
>>>>> That's an excellent question and one that should have been asked
>>>>> before 8200167 was finalized. :( The short answer is "no" -
>>>>> callerClass can be non-null for any of the invocation modes. And
>>>>> yes the current mainline code is broken - seems there is a gap in
>>>>> the existing test coverage as we never call a final method from an
>>>>> interface method. If we do we get:
>>>>>
>>>>> Exception in thread "main" java.lang.InternalError: Should only be
>>>>> invoked on a subclass
>>>>> at
>>>>> java.base/java.lang.invoke.DirectMethodHandle.checkReceiver(DirectMethodHandle.java:441)
>>>>>
>>>>>
>>>>> <sigh>
>>>>>
>>>>> We only look at callerClass when dealing with LF_INVSPECIAL, which
>>>>> in mainline means we either have an invokespecial or an
>>>>> invokevirtual. For invokespecial this is fine of course. But the
>>>>> invokevirtual case was never encountered and so slipped by in
>>>>> error. With nestmates we also add invokeinterface to the mix -
>>>>> which is fine because if it is an invokeinterface then we want the
>>>>> check regardless. It doesn't matter if the check is enabled because
>>>>> of the (incidental) callerClass.isInterface check, or the explicit
>>>>> m.getDeclaringClass().isInterface(). But the logic is messy and far
>>>>> from clear and not correct by construction. So I will completely
>>>>> redo it in a simpler and more direct/explicit way.
>>>>>
>>>>> BTW another red-herring: the !m.isStatic() part of the condition
>>>>> was not needed. I was tracking down two failure modes before
>>>>> finalizing this. The first was a problem with a static interface
>>>>> method - fixed by the !m.isStatic(). The second was caused by
>>>>> missing parentheses in the overall condition - which once fixed
>>>>> precluded the static case, so the first fix was not needed (as we
>>>>> never use LF_INVSPECIAL with statics). If only I'd tackled them in
>>>>> the reverse order.
>>>>>
>>>>> I'll post an updated webrev later today once I've re-tested lots of
>>>>> things.
>>>>>
>>>>>> - agree with the theory that invokevirtual will never find a
>>>>>> private interface method (and ACC_FINAL is illegal for interfaces)
>>>>>
>>>>> Yes. More specifically as we're dealing with MH semantics:
>>>>> findVirtual for an interface method yields a MH with
>>>>> invokeInterface "kind", not one with invokeVirtual "kind".
>>>>>
>>>>> public MethodHandle findVirtual(Class<?> refc, String name,
>>>>> MethodType type) throws NoSuchMethodException,
>>>>> IllegalAccessException {
>>>>> ...
>>>>> byte refKind = (refc.isInterface() ? REF_invokeInterface :
>>>>> REF_invokeVirtual);
>>>>> ...
>>>>> }
>>>>>
>>>>>
>>>>>> 4. Test - I still need to study this
>>>>>> I have been writing down test cases to make sure we don’t test
>>>>>> cases we don’t want to, and I
>>>>>> need to double-check you have them covered. Will do that tomorrow.
>>>>>
>>>>> The testing is all "positive" in the sense that it ensures a
>>>>> receiver subtype check is in place when it "must be". In fact it
>>>>> must always be the case the receiver has a type that has the method
>>>>> being invoked. We were just missing a few cases that verified that
>>>>> (and some stronger conditions: ie receiver <: caller for
>>>>> invokespecial semantics).
>>>>>
>>>>> If you want to test that we don't insert the new explicit checks in
>>>>> cases where they are not needed, then I don't know how to do that -
>>>>> other than by adding tracing and running the test case and not
>>>>> seeing checkReceiver being called.
>>>>>
>>>>> That said, once I've reworked the logic it will be blindingly
>>>>> obvious when the new explicit check is being added.
>>>>>
>>>>> Thanks,
>>>>> David
>>>>>
>>>>>
>>>>>> thanks,
>>>>>> Karen
>>>>>>
>>>>>>> On May 3, 2018, at 6:21 AM, David Holmes
>>>>>>> <david.holmes at oracle.com> wrote:
>>>>>>>
>>>>>>> bug id: https://bugs.openjdk.java.net/browse/JDK-8197915
>>>>>>> webrev: http://cr.openjdk.java.net/~dholmes/8197915/webrev/
>>>>>>>
>>>>>>> JDK-8174962 implemented receiver typechecks for invokeinterface
>>>>>>> within the interpreter (templateTable), compilers and for
>>>>>>> MethodHandles. In nestmates invokeinterface can now be used for
>>>>>>> private interface methods - which result in direct calls. So we
>>>>>>> need to extend the receiver subtype checks to cover the new cases.
>>>>>>>
>>>>>>> Summary of changes:
>>>>>>>
>>>>>>> - src/hotspot/cpu/<cpu>/templateTable_<cpu>.cpp
>>>>>>>
>>>>>>> In the templateTable the 8174962 checks come after the private
>>>>>>> interface method invocation logic ("vfinal") we already had in
>>>>>>> place for the nestmate changes, and they rely on itable
>>>>>>> information that doesn't exist for private methods. So we insert
>>>>>>> a direct subtype check.
>>>>>>>
>>>>>>> I've provided code for all CPU's but only x86 and sparc have been
>>>>>>> tested. I'll be soliciting aid on the other ports before
>>>>>>> nestmates goes to mainline later this month.
>>>>>>>
>>>>>>> - src/hotspot/share/oops/cpCache.cpp
>>>>>>>
>>>>>>> We have to pass the interface klass* so it's available for the
>>>>>>> typecheck.
>>>>>>>
>>>>>>> - src/hotspot/share/oops/klassVtable.cpp
>>>>>>>
>>>>>>> Updated a comment that's no longer accurate.
>>>>>>>
>>>>>>> - src/hotspot/share/opto/doCall.cpp
>>>>>>>
>>>>>>> This code was provided by Vladimir Ivanov (thank you!) and
>>>>>>> expands the existing "invokespecial" support for receiver
>>>>>>> typechecks in C2, to "invokeinterface" as well.
>>>>>>>
>>>>>>> Aside: no changes were needed for C1. It's seems all the receiver
>>>>>>> typechecks for C1 are being handled at a higher level (through
>>>>>>> linkResolver and/or cpCache logic).
>>>>>>>
>>>>>>> - src/hotspot/share/prims/methodHandles.cpp
>>>>>>>
>>>>>>> Comment clarifying JVM_REF_invokeSpecial doesn't necessarily mean
>>>>>>> it relates to an actual "invokespecial" - it is used for all
>>>>>>> direct calls.
>>>>>>>
>>>>>>> -
>>>>>>> src/java.base/share/classes/java/lang/invoke/DirectMethodHandle.java
>>>>>>>
>>>>>>> Add clarifying comments regarding how "kind" can vary if a direct
>>>>>>> call is involved.
>>>>>>>
>>>>>>> Expand the condition to switch from LF_INVSPECIAL to
>>>>>>> LF_INVSPECIAL_IFC (which adds the additional receiver typecheck)
>>>>>>> to account for the invokeinterface case.
>>>>>>>
>>>>>>> - test/jdk/java/lang/invoke/PrivateInterfaceCall.java
>>>>>>>
>>>>>>> New test for invokeinterface semantics that mirrors the existing
>>>>>>> SpecialInterfaceCall test for invokespecial.
>>>>>>>
>>>>>>> This is the last of the significant functional changes for
>>>>>>> nestmates.
>>>>>>>
>>>>>>> Thanks,
>>>>>>> David
>>>>>>
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