llvm dev - Jun 2017 - How does sanitizers in compiler-rt work?

Can anybody give me any pointer on how compiler-rt, especially the
sanitizers work? Do they operate on IR as any other LLVM pass? Or are they
integral part of the frontend itself? I couldn't spot any documentation on
the internals of compiler-rt project? What happens (sequence of actions)
when I pass -fsanitizer=dataflow to clang?

Precisely, I intend to alter the behaviour of DFSan to suit my need.
Therefore, I need to know how it gets integrated in the tool-chain.
Initially, my idea was to insert the dfsan_set_label() calls to the IR and
pass it to DFSan. However, I am not sure if it's designed to run on the
source only, not on IR.

-- 

Thanks & Regards,
Dipanjan
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> On Jun 16, 2017, at 4:11 AM, Dipanjan Das via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
> 
> 
> Can anybody give me any pointer on how compiler-rt, especially the
sanitizers work? Do they operate on IR as any other LLVM pass? Or are they
integral part of the frontend itself? I couldn't spot any documentation on
the internals of compiler-rt project? What happens (sequence of actions) when I
pass -fsanitizer=dataflow to clang?
Passing -fsanitize=dataflow tells clang to insert the dataflow sanitizer's
instrumentation pass into the normal compilation pipeline. The instrumentation
occurs at the LLVM IR level. The pass may insert calls into runtime functions
which are provided by compiler-rt. Therefore, in order to link a program
compiled with -fsanitize=dataflow, the appropriate runtime library from
compiler-rt is required.

> Precisely, I intend to alter the behaviour of DFSan to suit my need.
What is your need, exactly?

> Therefore, I need to know how it gets integrated in the tool-chain.
Initially, my idea was to insert the dfsan_set_label() calls to the IR and pass
it to DFSan. However, I am not sure if it's designed to run on the source
only, not on IR.
You should take a look at lib/Transforms/Instrumentation/DataFlowSanitizer.cpp.
There doesn't appear to be much done at the source level.

best,
vedant
> 
> -- 
> Thanks & Regards,
> 
> Dipanjan
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
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Hi Vedant,

Thanks for the pointers. Please find my replies inline.

On 16 June 2017 at 14:48, Vedant Kumar <vsk at apple.com> wrote:
>
> On Jun 16, 2017, at 4:11 AM, Dipanjan Das via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>
> Can anybody give me any pointer on how compiler-rt, especially the
> sanitizers work? Do they operate on IR as any other LLVM pass? Or are they
> integral part of the frontend itself? I couldn't spot any documentation
on
> the internals of compiler-rt project? What happens (sequence of actions)
> when I pass -fsanitizer=dataflow to clang?
>
>
> Passing -fsanitize=dataflow tells clang to insert the dataflow
sanitizer's
> instrumentation pass into the normal compilation pipeline. The
> instrumentation occurs at the LLVM IR level. The pass may insert calls into
> runtime functions which are provided by compiler-rt. Therefore, in order to
> link a program compiled with -fsanitize=dataflow, the appropriate runtime
> library from compiler-rt is required.
>
>
> Precisely, I intend to alter the behaviour of DFSan to suit my need.
>
>
> What is your need, exactly?
>
>
Instead of manually inserting the dfsan_create_label() and
dfsan_set_label() calls in the source, I want to automatically insert those
calls in the IR for all the input variables in scanf(). I intend to run the
DFsan pass afterwards, thus instrumenting the IR further as required.

> Therefore, I need to know how it gets integrated in the tool-chain.
> Initially, my idea was to insert the dfsan_set_label() calls to the IR and
> pass it to DFSan. However, I am not sure if it's designed to run on the
> source only, not on IR.
>
>
> You should take a look at
lib/Transforms/Instrumentation/DataFlowSanitizer.cpp.
> There doesn't appear to be much done at the source level.
>
> best,
> vedant
>
>
> --
>
> Thanks & Regards,
> Dipanjan
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
>
>

-- 

Thanks & Regards,
Dipanjan
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