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/ADT/SmallPtrSet.h"
16 #include "llvm/IR/DerivedTypes.h"
17 #include "llvm/IR/Function.h"
18 #include "llvm/IR/IRBuilder.h"
19 #include "llvm/IR/Module.h"
20 #include "llvm/Support/raw_ostream.h"
21
22 using namespace llvm;
23
appendToGlobalArray(const char * Array,Module & M,Function * F,int Priority)24 static void appendToGlobalArray(const char *Array,
25 Module &M, Function *F, int Priority) {
26 IRBuilder<> IRB(M.getContext());
27 FunctionType *FnTy = FunctionType::get(IRB.getVoidTy(), false);
28
29 // Get the current set of static global constructors and add the new ctor
30 // to the list.
31 SmallVector<Constant *, 16> CurrentCtors;
32 StructType *EltTy;
33 if (GlobalVariable *GVCtor = M.getNamedGlobal(Array)) {
34 // If there is a global_ctors array, use the existing struct type, which can
35 // have 2 or 3 fields.
36 ArrayType *ATy = cast<ArrayType>(GVCtor->getType()->getElementType());
37 EltTy = cast<StructType>(ATy->getElementType());
38 if (Constant *Init = GVCtor->getInitializer()) {
39 unsigned n = Init->getNumOperands();
40 CurrentCtors.reserve(n + 1);
41 for (unsigned i = 0; i != n; ++i)
42 CurrentCtors.push_back(cast<Constant>(Init->getOperand(i)));
43 }
44 GVCtor->eraseFromParent();
45 } else {
46 // Use the new three-field struct if there isn't one already.
47 EltTy = StructType::get(IRB.getInt32Ty(), PointerType::getUnqual(FnTy),
48 IRB.getInt8PtrTy(), nullptr);
49 }
50
51 // Build a 2 or 3 field global_ctor entry. We don't take a comdat key.
52 Constant *CSVals[3];
53 CSVals[0] = IRB.getInt32(Priority);
54 CSVals[1] = F;
55 // FIXME: Drop support for the two element form in LLVM 4.0.
56 if (EltTy->getNumElements() >= 3)
57 CSVals[2] = llvm::Constant::getNullValue(IRB.getInt8PtrTy());
58 Constant *RuntimeCtorInit =
59 ConstantStruct::get(EltTy, makeArrayRef(CSVals, EltTy->getNumElements()));
60
61 CurrentCtors.push_back(RuntimeCtorInit);
62
63 // Create a new initializer.
64 ArrayType *AT = ArrayType::get(EltTy, CurrentCtors.size());
65 Constant *NewInit = ConstantArray::get(AT, CurrentCtors);
66
67 // Create the new global variable and replace all uses of
68 // the old global variable with the new one.
69 (void)new GlobalVariable(M, NewInit->getType(), false,
70 GlobalValue::AppendingLinkage, NewInit, Array);
71 }
72
appendToGlobalCtors(Module & M,Function * F,int Priority)73 void llvm::appendToGlobalCtors(Module &M, Function *F, int Priority) {
74 appendToGlobalArray("llvm.global_ctors", M, F, Priority);
75 }
76
appendToGlobalDtors(Module & M,Function * F,int Priority)77 void llvm::appendToGlobalDtors(Module &M, Function *F, int Priority) {
78 appendToGlobalArray("llvm.global_dtors", M, F, Priority);
79 }
80
81 GlobalVariable *
collectUsedGlobalVariables(Module & M,SmallPtrSetImpl<GlobalValue * > & Set,bool CompilerUsed)82 llvm::collectUsedGlobalVariables(Module &M, SmallPtrSetImpl<GlobalValue *> &Set,
83 bool CompilerUsed) {
84 const char *Name = CompilerUsed ? "llvm.compiler.used" : "llvm.used";
85 GlobalVariable *GV = M.getGlobalVariable(Name);
86 if (!GV || !GV->hasInitializer())
87 return GV;
88
89 const ConstantArray *Init = cast<ConstantArray>(GV->getInitializer());
90 for (unsigned I = 0, E = Init->getNumOperands(); I != E; ++I) {
91 Value *Op = Init->getOperand(I);
92 GlobalValue *G = cast<GlobalValue>(Op->stripPointerCastsNoFollowAliases());
93 Set.insert(G);
94 }
95 return GV;
96 }
97
checkSanitizerInterfaceFunction(Constant * FuncOrBitcast)98 Function *llvm::checkSanitizerInterfaceFunction(Constant *FuncOrBitcast) {
99 if (isa<Function>(FuncOrBitcast))
100 return cast<Function>(FuncOrBitcast);
101 FuncOrBitcast->dump();
102 std::string Err;
103 raw_string_ostream Stream(Err);
104 Stream << "Sanitizer interface function redefined: " << *FuncOrBitcast;
105 report_fatal_error(Err);
106 }
107
createSanitizerCtorAndInitFunctions(Module & M,StringRef CtorName,StringRef InitName,ArrayRef<Type * > InitArgTypes,ArrayRef<Value * > InitArgs,StringRef VersionCheckName)108 std::pair<Function *, Function *> llvm::createSanitizerCtorAndInitFunctions(
109 Module &M, StringRef CtorName, StringRef InitName,
110 ArrayRef<Type *> InitArgTypes, ArrayRef<Value *> InitArgs,
111 StringRef VersionCheckName) {
112 assert(!InitName.empty() && "Expected init function name");
113 assert(InitArgTypes.size() == InitArgTypes.size() &&
114 "Sanitizer's init function expects different number of arguments");
115 Function *Ctor = Function::Create(
116 FunctionType::get(Type::getVoidTy(M.getContext()), false),
117 GlobalValue::InternalLinkage, CtorName, &M);
118 BasicBlock *CtorBB = BasicBlock::Create(M.getContext(), "", Ctor);
119 IRBuilder<> IRB(ReturnInst::Create(M.getContext(), CtorBB));
120 Function *InitFunction =
121 checkSanitizerInterfaceFunction(M.getOrInsertFunction(
122 InitName, FunctionType::get(IRB.getVoidTy(), InitArgTypes, false),
123 AttributeSet()));
124 InitFunction->setLinkage(Function::ExternalLinkage);
125 IRB.CreateCall(InitFunction, InitArgs);
126 if (!VersionCheckName.empty()) {
127 Function *VersionCheckFunction =
128 checkSanitizerInterfaceFunction(M.getOrInsertFunction(
129 VersionCheckName, FunctionType::get(IRB.getVoidTy(), {}, false),
130 AttributeSet()));
131 IRB.CreateCall(VersionCheckFunction, {});
132 }
133 return std::make_pair(Ctor, InitFunction);
134 }
135
136