On Friday, April 27, 2012 2:08:45 AM UTC-4, andria wrote:
>
> Maybe I'm wrong but I think they are not shared because applications run 
> in different processes.


The question regarded threads rather than processes.  On Linux threads are 
implemented as lightweight processes, but part of what makes them 
lightweight is that they share the same view of and access rights to memory 
- there is no real privacy between them, at most a "choosing not to look" 
or "not being exactly sure where to look, without searching".  

My suspicion is that as a matter of convenience each thread would have it's 
own VM registers, but I am confident that any thread within a process can 
discover the values of the DVM registers, at least to the degree they exist 
in memory (vs. being optimized away by JIT), for any given build of the DVM 
which an exploit author has chosen to study in detail.  I'd expect an 
exploit author could also preclude the use of JIT in order to make the task 
simpler.

At any rate (and I missed this too when first replying) the question is off 
topic for the Kernel group, as Dalvik is not part of the kernel and does 
not run in kernel mode.  As far as the kernel is concerned, a DVM is just a 
random user-mode process.

 
 

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