RFR (S) 8158851: MH.publicLookup() init circularity, triggered by custom SecurityManager with String concat and -limitmods java.base

[Jim Laskey (Oracle)]

If it’s in the jimage, I/O should not be an issue (defineClass from a direct memory mapped buffer) vs assembling and assigning a byte array.  Measure first?


> On Jun 7, 2016, at 12:44 PM, Aleksey Shipilev <aleksey.shipilev at oracle.com> wrote:
> 
> On 06/07/2016 06:09 PM, Jim Laskey (Oracle) wrote:
>> Generally I disagree with this kind of hack. It will bite you in the
>> @$$ at some point. Why not just have a class file containing the bytes?
> 
> What's the difference between a small binary blob in a
> filesystem/resource vs a small binary blob inlined? Apart from the
> additional hassle of packing things into resources (which probably
> requires dealing with build?), hitting the I/O for loading it (which
> probably defeats the purpose of constructing the class on the fly), etc.
> 
> I wonder if the whole LookupHelper business is here to stay: Alan said
> that part of mechanics is up to a reimplementation?
> 
> Thanks,
> -Aleksey
> 
>>> On Jun 7, 2016, at 11:56 AM, Aleksey Shipilev <aleksey.shipilev at oracle.com> wrote:
>>> 
>>> On 06/07/2016 04:51 PM, Alan Bateman wrote:
>>>> On 07/06/2016 14:38, Aleksey Shipilev wrote:
>>>>> Please review a fix for a MH.publicLookup() circularity, which is
>>>>> triggered if you run existing String concat tests with -limitmods
>>>>> java.base:
>>>>>  https://bugs.openjdk.java.net/browse/JDK-8158851
>>>>> 
>>>>> Webrev:
>>>>>  http://cr.openjdk.java.net/~shade/8158851/webrev.01/
>>>> As a short term fix then this looks okay. It may be (once there is
>>>> another round of work on MethodHandles w/modules) that PL moves back to
>>>> java.lang.Object but that has many discussion points for another thread.
>>>> 
>>>> If you want then the doPriv in LookupHelper can do away as it is not
>>>> required when you can guarantee that it is initialized before a security
>>>> manager is set.
>>> 
>>> Done so.
>>> 
>>>> One downside to initializing PL early is that is LookupHelper will
>>>> trigger some ASM to be loaded. This could avoid by generating it at link
>>>> time and loading the class bytes as resource. Hard to know if it's worth
>>>> it as the first lambda usage is going to trigger these classes to load
>>>> anyway.
>>> 
>>> Yes. I agree with Claes here, can't we inline the bytecode to avoid
>>> messing with ASM?
>>> 
>>> See:
>>> http://cr.openjdk.java.net/~shade/8158851/webrev.02/
>>> 
>>> Still passes all java/lang tests.
>>> 
>>> Thanks,
>>> -Aleksey
>>> 
>>> 
>> 
> 
>