How to properly insert a function call using LLVM? - llvm

Question

I'm trying to set up a pass that will insert a couple of global variables as well as a couple of function calls at the beginning of main. However, I believe I have an issue with setting up the function description correctly. My code compiles, but when I try to run the pass I get this error:
void llvm::CallInst::init(llvm::Value*, llvm::ArrayRef<llvm::Value*>, const llvm::Twine&):
Assertion `(Args.size() == FTy->getNumParams() || (FTy->isVarArg() && Args.size() > FTy-
>getNumParams())) && "Calling a function with bad signature!"' failed.
Here is the code I have written so far:
#include "llvm/IR/Instructions.h"
#include "llvm/Pass.h"
#include "llvm/Support/InstIterator.h"
#include "llvm/IR/Function.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/Value.h"
#include "llvm/IR/GlobalValue.h"
#include "llvm/IR/GlobalVariable.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/Type.h"
#include "llvm/IR/Module.h"
using namespace llvm;
namespace{
struct fun_insert : public FunctionPass{
static char ID;
fun_insert():FunctionPass(ID){}
virtual bool runOnFunction(Function &F){
if (F.getName() == "main"){
for (inst_iterator I = inst_begin(F), E= inst_end(F); I != E; ++I){
Instruction *inst = &*I;
if(dyn_cast<AllocaInst> (inst)){
errs() << "test" << "\n";
GlobalVariable *virtAddr = new GlobalVariable(*F.getParent(),
Type::getInt8PtrTy(F.getContext()), false,
GlobalValue::ExternalLinkage, 0, "virt_addr");
virtAddr->setAlignment(4);
Module *M = F.getParent();
Constant *c = M->getOrInsertFunction("open",
IntegerType::get(F.getContext(),32),
PointerType::get(Type::getInt8PtrTy(F.getContext(), 8),8),
IntegerType::get(F.getContext(),32), NULL);
Function *open = cast<Function>(c);
//ConstantInt *a = ConstantInt::get(M->getContext(), APInt(32, 9437184));
IRBuilder<> builder(inst);
Value *strPtr = builder.CreateGlobalStringPtr("/dev/mem", ".str");
ConstantInt *a = builder.getInt32(9437184);
//CallInst *openRet = builder.CreateCall2(open, strPtr, a, "open");
builder.CreateCall2(open, strPtr, a, "open");
}
errs() << *inst <<"\n";
}
}
return false;
}
};
}
char fun_insert::ID=0;
static RegisterPass<fun_insert>
X("fun_insert", "Insert Function Test", false, false);
Thanks for any help!

Answer 1

I believe I have resolved the issue. The issue did lie with the function declaration and call. I adjusted the code as follows:
Constant *c = M->getOrInsertFunction("open",
FunctionType::getInt32Ty(F.getContext()),
Type::getInt8PtrTy(F.getContext()),
Type::getInt32Ty(F.getContext()),
NULL);
Function *open = cast<Function>(c);
IRBuilder<> builder(inst);
Value *strPtr = builder.CreateGlobalStringPtr("/dev/mem", ".str");
ConstantInt *a = builder.getInt32(9437184);
builder.CreateCall2(open,strPtr,a);