[PATCH] Expose llvm::linkShadowStackGC() via C bindings

[Mukul Sabharwal]

ping. any takers?

On Wed, Apr 1, 2015 at 9:31 PM, Mukul Sabharwal <mjsabby at gmail.com> wrote:

> Resending since I wasn't part of mailing list at the time
>
>
> On Wednesday, April 1, 2015, Mukul Sabharwal <mjsabby at gmail.com> wrote:
>
>> Hi reames,
>>
>> An LLVMSharp user filed a bug report (
>> https://github.com/mjsabby/LLVMSharp/issues/3) that using the library
>> they were unable to call SetGC("shadow-stack") on a function and then
>> subsequently ask MCJIT to finalize the object containing the function.
>>
>> They also created an LLVM bug report (
>> https://llvm.org/bugs/show_bug.cgi?id=23095) that demonstrates the
>> problem.
>>
>> I have investigated the root cause for this and it is because LLVMSharp
>> and other C binding users do not have access to llvm::linkShadowStackGC (in
>> addition to other GCs defined in llvm/include/llvm/CodeGen/GCs.h) which GC
>> clients of the C++ API would need to call in order to successfully complete
>> this scenario.
>>
>> I'm proposing to expose LLVMLinkShadowStackGC via the C bindings. The
>> ShadowStackGC is very useful functionality that is referenced in the
>> official documentation and likely to be beneficial to many users.
>>
>> I'm consciously choosing not to link other GCs, but maybe I should? Let
>> me know as part of the review feedback if I should also expose other GCs
>> (currently StatepointExample, Erlang, and Ocaml)
>>
>> REPOSITORY
>>   rL LLVM
>>
>> http://reviews.llvm.org/D8788
>>
>> Files:
>>   include/llvm-c/Core.h
>>   lib/IR/Core.cpp
>>
>> Index: include/llvm-c/Core.h
>> ===================================================================
>> --- include/llvm-c/Core.h
>> +++ include/llvm-c/Core.h
>> @@ -1921,6 +1921,13 @@
>>  void LLVMSetGC(LLVMValueRef Fn, const char *Name);
>>
>>  /**
>> +* Link the Shadow Stack GC
>> +*
>> +* @see llvm::linkShadowStackGC()
>> +*/
>> +void LLVMLinkShadowStackGC();
>> +
>> +/**
>>   * Add an attribute to a function.
>>   *
>>   * @see llvm::Function::addAttribute()
>> Index: lib/IR/Core.cpp
>> ===================================================================
>> --- lib/IR/Core.cpp
>> +++ lib/IR/Core.cpp
>> @@ -14,6 +14,7 @@
>>
>>  #include "llvm-c/Core.h"
>>  #include "llvm/Bitcode/ReaderWriter.h"
>> +#include "llvm/CodeGen/GCs.h"
>>  #include "llvm/IR/Attributes.h"
>>  #include "llvm/IR/CallSite.h"
>>  #include "llvm/IR/Constants.h"
>> @@ -1709,6 +1710,10 @@
>>      F->clearGC();
>>  }
>>
>> +void LLVMLinkShadowStackGC() {
>> +  llvm::linkShadowStackGC();
>> +}
>> +
>>  void LLVMAddFunctionAttr(LLVMValueRef Fn, LLVMAttribute PA) {
>>    Function *Func = unwrap<Function>(Fn);
>>    const AttributeSet PAL = Func->getAttributes();
>>
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>
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