[llvm-dev] Implementing Data Flow Integrity
John Criswell via llvm-dev
llvm-dev at lists.llvm.org
Mon Aug 1 12:58:48 PDT 2016
On 7/31/16 11:48 AM, Fee via llvm-dev wrote:
> Dear all,
> I want to implement a pass that provides some kind of data flow
> integrity similar to Write Integrity Testing
> This approach statically determines for each memory write the
> (conservative, overapproximated) points-to set of locations that can be
> written by the instruction. Further, it instruments the memory write
> instruction to prevent a write to a location not in the points-to set.
Correct. I would also point out that their use of Anderson's analysis
is (most likely) unnecessary. Because they unify points-to sets before
instrumenting, they are modifying the end-result of the inclusion-based
analysis to be what unification-based points-to analysis would have
computed. It is not clear to me that anything can be gained by using
inclusion-based analysis over unification-based analysis.
> How can I get the points-to set, including locations from
> stack/heap/static variables?
> How do I approach this problem in general?
To the best of my knowledge, the existing LLVM alias analysis passes
only provide a mod/ref and aliasing query interface. I don't believe
they provide a shape graph or points-to sets that can be easily used.
You might want to check CFL-AA to see what it provides, but I have
personally never used it.
You could use DSA located in the poolalloc project which provides a
shape graph. The original SAFECode essentially did what WIT does
(except that it also protected memory reads and used a very different
run-time check mechanism, plus it could optimize away provably type-safe
checks). SAFECode used DSA's shape graphs to segregate the heap, find
points-to sets, and learn memory object type information. However, in
its current shape, you'd need to run DSA prior to most LLVM
optimizations to get good field sensitivity. Otherwise, DSA will lose
field sensitivity and provide poor precision in its results.
As I need something similar for my research work, my research group will
be working on either improving or replacing DSA. However, it'll be
awhile, so if you need something now, either CFL-AA or DSA will be your
> I am new to LLVM.
Welcome to the club.
> Thank you!
> – Fredi
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
Department of Computer Science, University of Rochester
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