[foreign-memaccess] RFR 8227107: Add missing toString implementation to MemorySegmentImp

[Maurizio Cimadamore]

On 02/07/2019 21:58, John Rose wrote:
> On Jul 2, 2019, at 9:29 AM, Maurizio Cimadamore 
> <maurizio.cimadamore at oracle.com 
> <mailto:maurizio.cimadamore at oracle.com>> wrote:
>>
>> toString() method can't reveal sensitive pointer info
>
> I wonder if there is a way to sanitize the pointer value, into a hash 
> code.
> Some JVMs use the raw object address as an input to the identity hash 
> code.
> We could do something similar.  The hash could be kept small, to (say) 
> 5 hex digits,
> and would serve to separate the segments for debugging purposes.
> Since the default Object.toString does something like this I'm 
> thinking we could
> emulate that.
>
> (How to hash the address?  First take a 64-bit address and another 64 
> bits of
> nonce secret to the current JVM instance.  Then mix them together, using
> xxhash or a similar algorithm.  Then throw away all but a few, say 20, 
> bits
> of result.  The result will provide no useful information to 
> attackers, other than
> a likely discrimination between different base pointers.)
>
That's a nice suggestion!

Maurizio

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