[cfe-dev] Dataflow Sanitizer ClCombinePointerLabelsOnStore option

[Peter Collingbourne]

On Thu, Sep 04, 2014 at 05:38:57PM -0500, Frederico Araujo wrote:
> Dear list,
> 
> Can someone help me understand how dfsan's combine labels on store semantics
> (ClCombinePointerLabelsOnStore option) work?
> 
> For discussion, here's an example (p is a pointer):
> 
> p = v1;
> p = v2;

Did you mean:

*p = v1;
*p = v2;

i.e. storing through the pointer p? Simply assigning to a pointer variable
propagates the label in the same way as for any other type of variable.

> Assume label(p)=LP, label(v1)=L1, and label(v2)=L2. Then, if my
> understanding is correct, this is how labels propagate:
> 
> Default semantics:
> 
> p = v1; // p* is labeled with L1
> p = v2; // p* is labeled with L2
> 
> Combine semantics (ClCombinePointerLabelsOnStore is set):
> 
> p = v1; // p* is labeled with L1 + LP
> p = v2; // p* is labeled with L2 + LP
> 
> Is this the correct behavior?

That is correct, assuming you meant *p instead of p.

Thanks,
-- 
Peter