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

[Mukul Sabharwal]

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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