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 static void appendToUsedList(Module &M, StringRef Name, ArrayRef<GlobalValue *> Values) {
93   GlobalVariable *GV = M.getGlobalVariable(Name);
94   SmallPtrSet<Constant *, 16> InitAsSet;
95   SmallVector<Constant *, 16> Init;
96   if (GV) {
97     ConstantArray *CA = dyn_cast<ConstantArray>(GV->getInitializer());
98     for (auto &Op : CA->operands()) {
99       Constant *C = cast_or_null<Constant>(Op);
100       if (InitAsSet.insert(C).second)
101         Init.push_back(C);
102     }
103     GV->eraseFromParent();
104   }
105 
106   Type *Int8PtrTy = llvm::Type::getInt8PtrTy(M.getContext());
107   for (auto *V : Values) {
108     Constant *C = ConstantExpr::getBitCast(V, Int8PtrTy);
109     if (InitAsSet.insert(C).second)
110       Init.push_back(C);
111   }
112 
113   if (Init.empty())
114     return;
115 
116   ArrayType *ATy = ArrayType::get(Int8PtrTy, Init.size());
117   GV = new llvm::GlobalVariable(M, ATy, false, GlobalValue::AppendingLinkage,
118                                 ConstantArray::get(ATy, Init), Name);
119   GV->setSection("llvm.metadata");
120 }
121 
122 void llvm::appendToUsed(Module &M, ArrayRef<GlobalValue *> Values) {
123   appendToUsedList(M, "llvm.used", Values);
124 }
125 
126 void llvm::appendToCompilerUsed(Module &M, ArrayRef<GlobalValue *> Values) {
127   appendToUsedList(M, "llvm.compiler.used", Values);
128 }
129 
130 Function *llvm::checkSanitizerInterfaceFunction(Constant *FuncOrBitcast) {
131   if (isa<Function>(FuncOrBitcast))
132     return cast<Function>(FuncOrBitcast);
133   FuncOrBitcast->dump();
134   std::string Err;
135   raw_string_ostream Stream(Err);
136   Stream << "Sanitizer interface function redefined: " << *FuncOrBitcast;
137   report_fatal_error(Err);
138 }
139 
140 std::pair<Function *, Function *> llvm::createSanitizerCtorAndInitFunctions(
141     Module &M, StringRef CtorName, StringRef InitName,
142     ArrayRef<Type *> InitArgTypes, ArrayRef<Value *> InitArgs,
143     StringRef VersionCheckName) {
144   assert(!InitName.empty() && "Expected init function name");
145   assert(InitArgs.size() == InitArgTypes.size() &&
146          "Sanitizer's init function expects different number of arguments");
147   Function *Ctor = Function::Create(
148       FunctionType::get(Type::getVoidTy(M.getContext()), false),
149       GlobalValue::InternalLinkage, CtorName, &M);
150   BasicBlock *CtorBB = BasicBlock::Create(M.getContext(), "", Ctor);
151   IRBuilder<> IRB(ReturnInst::Create(M.getContext(), CtorBB));
152   Function *InitFunction =
153       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
154           InitName, FunctionType::get(IRB.getVoidTy(), InitArgTypes, false),
155           AttributeSet()));
156   InitFunction->setLinkage(Function::ExternalLinkage);
157   IRB.CreateCall(InitFunction, InitArgs);
158   if (!VersionCheckName.empty()) {
159     Function *VersionCheckFunction =
160         checkSanitizerInterfaceFunction(M.getOrInsertFunction(
161             VersionCheckName, FunctionType::get(IRB.getVoidTy(), {}, false),
162             AttributeSet()));
163     IRB.CreateCall(VersionCheckFunction, {});
164   }
165   return std::make_pair(Ctor, InitFunction);
166 }
167