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      1 //===-- ModuleUtils.cpp - Functions to manipulate Modules -----------------===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 //
     10 // This family of functions perform manipulations on Modules.
     11 //
     12 //===----------------------------------------------------------------------===//
     13 
     14 #include "llvm/Transforms/Utils/ModuleUtils.h"
     15 #include "llvm/IR/DerivedTypes.h"
     16 #include "llvm/IR/Function.h"
     17 #include "llvm/IR/IRBuilder.h"
     18 #include "llvm/IR/Module.h"
     19 #include "llvm/Support/raw_ostream.h"
     20 
     21 using namespace llvm;
     22 
     23 static void appendToGlobalArray(const char *Array, Module &M, Function *F,
     24                                 int Priority, Constant *Data) {
     25   IRBuilder<> IRB(M.getContext());
     26   FunctionType *FnTy = FunctionType::get(IRB.getVoidTy(), false);
     27 
     28   // Get the current set of static global constructors and add the new ctor
     29   // to the list.
     30   SmallVector<Constant *, 16> CurrentCtors;
     31   StructType *EltTy;
     32   if (GlobalVariable *GVCtor = M.getNamedGlobal(Array)) {
     33     ArrayType *ATy = cast<ArrayType>(GVCtor->getValueType());
     34     StructType *OldEltTy = cast<StructType>(ATy->getElementType());
     35     // Upgrade a 2-field global array type to the new 3-field format if needed.
     36     if (Data && OldEltTy->getNumElements() < 3)
     37       EltTy = StructType::get(IRB.getInt32Ty(), PointerType::getUnqual(FnTy),
     38                               IRB.getInt8PtrTy(), nullptr);
     39     else
     40       EltTy = OldEltTy;
     41     if (Constant *Init = GVCtor->getInitializer()) {
     42       unsigned n = Init->getNumOperands();
     43       CurrentCtors.reserve(n + 1);
     44       for (unsigned i = 0; i != n; ++i) {
     45         auto Ctor = cast<Constant>(Init->getOperand(i));
     46         if (EltTy != OldEltTy)
     47           Ctor = ConstantStruct::get(
     48               EltTy, Ctor->getAggregateElement((unsigned)0),
     49               Ctor->getAggregateElement(1),
     50               Constant::getNullValue(IRB.getInt8PtrTy()), nullptr);
     51         CurrentCtors.push_back(Ctor);
     52       }
     53     }
     54     GVCtor->eraseFromParent();
     55   } else {
     56     // Use the new three-field struct if there isn't one already.
     57     EltTy = StructType::get(IRB.getInt32Ty(), PointerType::getUnqual(FnTy),
     58                             IRB.getInt8PtrTy(), nullptr);
     59   }
     60 
     61   // Build a 2 or 3 field global_ctor entry.  We don't take a comdat key.
     62   Constant *CSVals[3];
     63   CSVals[0] = IRB.getInt32(Priority);
     64   CSVals[1] = F;
     65   // FIXME: Drop support for the two element form in LLVM 4.0.
     66   if (EltTy->getNumElements() >= 3)
     67     CSVals[2] = Data ? ConstantExpr::getPointerCast(Data, IRB.getInt8PtrTy())
     68                      : Constant::getNullValue(IRB.getInt8PtrTy());
     69   Constant *RuntimeCtorInit =
     70       ConstantStruct::get(EltTy, makeArrayRef(CSVals, EltTy->getNumElements()));
     71 
     72   CurrentCtors.push_back(RuntimeCtorInit);
     73 
     74   // Create a new initializer.
     75   ArrayType *AT = ArrayType::get(EltTy, CurrentCtors.size());
     76   Constant *NewInit = ConstantArray::get(AT, CurrentCtors);
     77 
     78   // Create the new global variable and replace all uses of
     79   // the old global variable with the new one.
     80   (void)new GlobalVariable(M, NewInit->getType(), false,
     81                            GlobalValue::AppendingLinkage, NewInit, Array);
     82 }
     83 
     84 void llvm::appendToGlobalCtors(Module &M, Function *F, int Priority, Constant *Data) {
     85   appendToGlobalArray("llvm.global_ctors", M, F, Priority, Data);
     86 }
     87 
     88 void llvm::appendToGlobalDtors(Module &M, Function *F, int Priority, Constant *Data) {
     89   appendToGlobalArray("llvm.global_dtors", M, F, Priority, Data);
     90 }
     91 
     92 Function *llvm::checkSanitizerInterfaceFunction(Constant *FuncOrBitcast) {
     93   if (isa<Function>(FuncOrBitcast))
     94     return cast<Function>(FuncOrBitcast);
     95   FuncOrBitcast->dump();
     96   std::string Err;
     97   raw_string_ostream Stream(Err);
     98   Stream << "Sanitizer interface function redefined: " << *FuncOrBitcast;
     99   report_fatal_error(Err);
    100 }
    101 
    102 std::pair<Function *, Function *> llvm::createSanitizerCtorAndInitFunctions(
    103     Module &M, StringRef CtorName, StringRef InitName,
    104     ArrayRef<Type *> InitArgTypes, ArrayRef<Value *> InitArgs,
    105     StringRef VersionCheckName) {
    106   assert(!InitName.empty() && "Expected init function name");
    107   assert(InitArgTypes.size() == InitArgTypes.size() &&
    108          "Sanitizer's init function expects different number of arguments");
    109   Function *Ctor = Function::Create(
    110       FunctionType::get(Type::getVoidTy(M.getContext()), false),
    111       GlobalValue::InternalLinkage, CtorName, &M);
    112   BasicBlock *CtorBB = BasicBlock::Create(M.getContext(), "", Ctor);
    113   IRBuilder<> IRB(ReturnInst::Create(M.getContext(), CtorBB));
    114   Function *InitFunction =
    115       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
    116           InitName, FunctionType::get(IRB.getVoidTy(), InitArgTypes, false),
    117           AttributeSet()));
    118   InitFunction->setLinkage(Function::ExternalLinkage);
    119   IRB.CreateCall(InitFunction, InitArgs);
    120   if (!VersionCheckName.empty()) {
    121     Function *VersionCheckFunction =
    122         checkSanitizerInterfaceFunction(M.getOrInsertFunction(
    123             VersionCheckName, FunctionType::get(IRB.getVoidTy(), {}, false),
    124             AttributeSet()));
    125     IRB.CreateCall(VersionCheckFunction, {});
    126   }
    127   return std::make_pair(Ctor, InitFunction);
    128 }
    129