[LLVMdev] Re:question about Insert callInst to call a function in library

[Zhang Qiuyu]

Thanks Chris, but the method you mentioned is not what I want. Maybe I didn't make it clear.
As you said, /runtime/libprofile is runtime library for the following function.
    llvm_start_func_profiling
    llvm_start_block_profiling
    llvm_start_basic_block_tracing
    llvm_trace_basic_block

And those above functions can be inserted into basic block etc for getting profile. However, those functions are wroten by C/C++ which just statistic some data. 
What I want is to write a Pass in external library. You know for the Pass, it will use LLVM methods. I can write a pass but I just don't know how to put the pass into external library and insert CallInst to call it like llvm_start_func_profiling.  I mean I could insert a CallInst into *.bc to call function in the exernal library, but is it possible that the function in library will use LLVM method and will use itself bytecode file  as input file? 

for example: m.bc is orignal bytecode.
mutated bytecode is m1.bc. I would like to insert a CallInst to call decode function to recover original bytecode m.bc. Actually, I would to compile m1.bc and decode library to executed file, and once I run m1, at first the decode function at entry of main should be run before any code running. So now the decode part is llvm pass, could I do it like what I want? Thanks

Qiuyu

decode pass:

using namespace llvm;
#define endl "\n"
namespace {
  struct DecodeStr : public FunctionPass{
    virtual bool runOnFunction(Function &F);
  private:
    void DecodeString(Module *M);
    void get_randKey(Module *M);
    Constant *randKey;
  };
  RegisterOpt<DecodeStr> X("DecodeStr", "Decode to visible string");
}

bool DecodeStr::runOnFunction(Function &F){
  get_randKey(F.getParent());  
  DecodeString(F.getParent()); 
  return true;
}
void DecodeStr::get_randKey(Module *M){
  for(Module::giterator gI=M->gbegin(),gE=M->gend();gI!=gE;++gI){
    std::string GVname = gI->getName();
    if(strcmp(GVname.c_str(),"Gvkey")==0){
      randKey =(gI->getInitializer());
    }
  }
}

void DecodeStr::DecodeString(Module *M){
  std::cerr<<"filename "<<M->getModuleIdentifier()<<endl;
  for(Module::giterator gI = M->gbegin(),gE=M->gend();gI!=gE;++gI){
    unsigned i=0;
    if(ConstantArray *Cstr = dyn_cast<ConstantArray>(gI->getInitializer())){
      if(Cstr->getType()->getElementType()->isInteger())
      {
 std::vector<Constant*> HideString;
   Constant *Key=ConstantInt::get(Cstr->getType()->getElementType(),randKey);
  for(unsigned i=0;i<Cstr->getNumOperands();++i){
   HideString.push_back(ConstantExpr::getXor(Cstr->getOperand(i),randKey));
 }
 gI->setInitializer(ConstantArray::get(Cstr->getType(),HideString));
 std::cerr<<"after set "<<*(gI->getInitializer())<<endl;
      }
    }
  }
}





> On Sun, 17 Oct 2004, Zhang Qiuyu wrote:
> 
> > Hi,
> >
> > Thanks Chris. Following your suggestion, I wrote the code to hide the
> > visible string. Thanks again. Finially, I just realized my LLVM still is
> > 1.2, not 1.3. Now I update it to 1.3.
> 
> ok.
> 
> > > > > 5. Insert the for loop that translates the string when main runs.
> > > > >
> > > > > For #5, write the for loop you want, compile it with llvmgcc, then figure
> > > > > out how to generate it at compile time.  Alternatively, you could put the
> > > > > 'decryption' routine in a library and just insert a call to the library.
> >
> > For decode part. I can write a pass to decode the hide-string bytecode(
> > after hide string pass, I create a globalvariable to store the Key for
> > decode routine. And on the decode pass, I use this Key to recover the
> > orignal bytecode.
> 
> Sure.
> 
> > It seems not good way to decode. The better way should be to embed the
> > decode routine into the bytecode in the entry of main. So the question
> > is how to do it?
> 
> That's fine, take a look at how the profiling instrumentation code works
> in lib/Transforms/Instrumentation.  That should give you examples of how
> to insert function calls.  grep for 'new CallInst'.
> 
> > What I can do is that,
> >     I can create call instruction and insert it into entry BB of main.
> > And this call function is able to call the a function of the external
> > library which I could create as I want( just using C style). And I can
> > write decode pass, but I don't know how to build a library as the way
> > you mentioned. Actually, I was thinking the pass I wrote is a dynamic
> > library as libdecode.so. So could I use it? if not, how to build the
> > library you mentioned? I thought the library you mentioned should be
> > similar with the pass. However, I have no idea how combine them?
> 
> Yes, this is no problem.  The profiling instrumentation inserts function
> calls which get resolved to the llvm/runtime/libprofile library.  Please
> look at how that works and you can pattern off of that.
> 
> -Chris
>