RFR(XS): 8144852: Corrupted oop in nmethod

[Vladimir Ivanov]

> Vladimir, are you OK with keeping the changes in method?  If so, I will
> push what I have.
I'm fine with leaving oopDesc::print_* as is.

Best regards,
Vladimir Ivanov

> On 12/16/2015 3:38 PM, Ioi Lam wrote:
>> Currently non_oop_word is used only in the nmethod code. If this value
>> is assigned to an oop or a metadata* elsewhere we would probably see
>> massive crashes. Adding non_oop_word to oopDesc::print_*_on would
>> imply that it's OK to assign this value in a more general context,
>> which is not true.
>>
>> So I would suggest keeping knowledge of non_oop_word inside nmethod
>> for now, and we can revisit this if other places start to use
>> non_oop_word.
>>
>> Thanks
>> - Ioi
>>
>> On 12/16/15 12:41 PM, Dean Long wrote:
>>> Ping.
>>>
>>> Could runtime folks please comment on Vladimir's suggestion to have
>>> oopDesc::print_*_on and
>>> Metadata::print_*_maybe_null support Universe::non_oop_word() values
>>> without crashing, or if I should keep this change in nmethod only.
>>>
>>> thanks,
>>>
>>> dl
>>>
>>> On 12/11/2015 11:18 AM, Dean Long wrote:
>>>> [adding hotspot-runtime-dev]
>>>>
>>>> On 12/11/2015 3:49 AM, Vladimir Ivanov wrote:
>>>>> Dean, thanks for taking care of it.
>>>>>
>>>>> Can oopDesc::print_value_on and print_value_on_maybe_null be
>>>>> enhanced instead to handle non_oop_word case (in addition to NULL
>>>>> case)?
>>>>>
>>>>
>>>> I thought of that, but didn't want to add
>>>> print_value_on_maybe_null_or_non_oop :-)
>>>>
>>>> If you feel strongly about that, then I should probably get input
>>>> from runtime too, since I think they own that code.
>>>>
>>>>> Also, the following is slightly misleading since metadata pointers
>>>>> aren't oops:
>>>>>  void nmethod::print_recorded_metadata() {
>>>>> +    if (m == (Metadata*)Universe::non_oop_word()) {
>>>>> +      tty->print("non-oop word");
>>>>>
>>>>
>>>> Would "non-metadata word" be better?
>>>>
>>>> dl
>>>>
>>>>> Best regards,
>>>>> Vladimir Ivanov
>>>>>
>>>>> On 12/11/15 6:36 AM, Dean Long wrote:
>>>>>> https://bugs.openjdk.java.net/browse/JDK-8144852
>>>>>> http://cr.openjdk.java.net/~dlong//8144852/webrev/
>>>>>>
>>>>>> The fix for [1] introduced new functions nmethod::print_recorded_oops
>>>>>> and nmethod::print_recorded_metadata that print all oop and metadata
>>>>>> values in an nmethod.  Currently NULL values are handled OK, but
>>>>>> Universe::non_oop_word values cause a crash.
>>>>>>
>>>>>> (This bug is marked confidential because it was reported against
>>>>>> one of
>>>>>> our closed ports.)
>>>>>>
>>>>>> dl
>>>>>>
>>>>>> [1]     JDK-8072008: Emit direct call instead of linkTo* for
>>>>>> recursive
>>>>>> indy/MH.invoke* calls
>>>>
>>>
>>
>