llvm dev - Jun 2016 - Fatpointer Pass already existing?

Hi everyone,

After spending 2 months on LLVM generally speaking and more specifically on
security passes (ASan, SAFECode, BoundsChecking) I wanted to know if there
were an available implementation of strictly fat-pointer based approach to
enforce bounds?

If not, I wanted to implement one. I think it is interessant to have such a
tool available even if there are better designs (SoftBound does have a
fat-pointer approach with separated metadata accessible by hash table or
shadow space which allows to have compatibility).

Thanks for your advice,
Pierre
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On 9 Jun 2016, at 10:57, Pierre Gagelin via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
> 
> After spending 2 months on LLVM generally speaking and more specifically on
security passes (ASan, SAFECode, BoundsChecking) I wanted to know if there were
an available implementation of strictly fat-pointer based approach to enforce
bounds?
> 
> If not, I wanted to implement one. I think it is interessant to have such a
tool available even if there are better designs (SoftBound does have a
fat-pointer approach with separated metadata accessible by hash table or shadow
space which allows to have compatibility).
I had a student implement one a couple of years ago, though I don’t think his
code will work with a recent LLVM.  Note that it’s quite difficult to do in the
general case, because (for inline metadata) you must do whole-program analysis
to know which allocations need to be bigger, which function signatures need
changing to pass the metadata, and so on.  His work included generating
ABI-compilant unsafe wrappers for the memory-save modified versions.

It’s also difficult to get the atomicity guarantees that most code expects (i.e.
that any thread will see either the before or after view of a pointer).

David

Hi David,

I am still working on the model to define it clearly so thanks for these
leads, I'll might contact you again to have a deeper discussion on some
points if that doesn't bother you. For the moment I am just establishing
the theoretical model, didn't had a look on the technical issues (like
multi-threaded applications for instance) yet.

If it is possible to have an access to the source code of your student's
project it would be welcome!

Thanks,
Pierre
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