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
appendToGlobalArray(const char * Array,Module & M,Function * F,int Priority,Constant * Data)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());
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 =
48 ConstantStruct::get(EltTy, Ctor->getAggregateElement((unsigned)0),
49 Ctor->getAggregateElement(1),
50 Constant::getNullValue(IRB.getInt8PtrTy()));
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());
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
appendToGlobalCtors(Module & M,Function * F,int Priority,Constant * Data)84 void llvm::appendToGlobalCtors(Module &M, Function *F, int Priority, Constant *Data) {
85 appendToGlobalArray("llvm.global_ctors", M, F, Priority, Data);
86 }
87
appendToGlobalDtors(Module & M,Function * F,int Priority,Constant * Data)88 void llvm::appendToGlobalDtors(Module &M, Function *F, int Priority, Constant *Data) {
89 appendToGlobalArray("llvm.global_dtors", M, F, Priority, Data);
90 }
91
appendToUsedList(Module & M,StringRef Name,ArrayRef<GlobalValue * > Values)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
appendToUsed(Module & M,ArrayRef<GlobalValue * > Values)122 void llvm::appendToUsed(Module &M, ArrayRef<GlobalValue *> Values) {
123 appendToUsedList(M, "llvm.used", Values);
124 }
125
appendToCompilerUsed(Module & M,ArrayRef<GlobalValue * > Values)126 void llvm::appendToCompilerUsed(Module &M, ArrayRef<GlobalValue *> Values) {
127 appendToUsedList(M, "llvm.compiler.used", Values);
128 }
129
checkSanitizerInterfaceFunction(Constant * FuncOrBitcast)130 Function *llvm::checkSanitizerInterfaceFunction(Constant *FuncOrBitcast) {
131 if (isa<Function>(FuncOrBitcast))
132 return cast<Function>(FuncOrBitcast);
133 FuncOrBitcast->print(errs());
134 errs() << '\n';
135 std::string Err;
136 raw_string_ostream Stream(Err);
137 Stream << "Sanitizer interface function redefined: " << *FuncOrBitcast;
138 report_fatal_error(Err);
139 }
140
declareSanitizerInitFunction(Module & M,StringRef InitName,ArrayRef<Type * > InitArgTypes)141 Function *llvm::declareSanitizerInitFunction(Module &M, StringRef InitName,
142 ArrayRef<Type *> InitArgTypes) {
143 assert(!InitName.empty() && "Expected init function name");
144 Function *F = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
145 InitName,
146 FunctionType::get(Type::getVoidTy(M.getContext()), InitArgTypes, false),
147 AttributeList()));
148 F->setLinkage(Function::ExternalLinkage);
149 return F;
150 }
151
createSanitizerCtorAndInitFunctions(Module & M,StringRef CtorName,StringRef InitName,ArrayRef<Type * > InitArgTypes,ArrayRef<Value * > InitArgs,StringRef VersionCheckName)152 std::pair<Function *, Function *> llvm::createSanitizerCtorAndInitFunctions(
153 Module &M, StringRef CtorName, StringRef InitName,
154 ArrayRef<Type *> InitArgTypes, ArrayRef<Value *> InitArgs,
155 StringRef VersionCheckName) {
156 assert(!InitName.empty() && "Expected init function name");
157 assert(InitArgs.size() == InitArgTypes.size() &&
158 "Sanitizer's init function expects different number of arguments");
159 Function *InitFunction =
160 declareSanitizerInitFunction(M, InitName, InitArgTypes);
161 Function *Ctor = Function::Create(
162 FunctionType::get(Type::getVoidTy(M.getContext()), false),
163 GlobalValue::InternalLinkage, CtorName, &M);
164 BasicBlock *CtorBB = BasicBlock::Create(M.getContext(), "", Ctor);
165 IRBuilder<> IRB(ReturnInst::Create(M.getContext(), CtorBB));
166 IRB.CreateCall(InitFunction, InitArgs);
167 if (!VersionCheckName.empty()) {
168 Function *VersionCheckFunction =
169 checkSanitizerInterfaceFunction(M.getOrInsertFunction(
170 VersionCheckName, FunctionType::get(IRB.getVoidTy(), {}, false),
171 AttributeList()));
172 IRB.CreateCall(VersionCheckFunction, {});
173 }
174 return std::make_pair(Ctor, InitFunction);
175 }
176
filterDeadComdatFunctions(Module & M,SmallVectorImpl<Function * > & DeadComdatFunctions)177 void llvm::filterDeadComdatFunctions(
178 Module &M, SmallVectorImpl<Function *> &DeadComdatFunctions) {
179 // Build a map from the comdat to the number of entries in that comdat we
180 // think are dead. If this fully covers the comdat group, then the entire
181 // group is dead. If we find another entry in the comdat group though, we'll
182 // have to preserve the whole group.
183 SmallDenseMap<Comdat *, int, 16> ComdatEntriesCovered;
184 for (Function *F : DeadComdatFunctions) {
185 Comdat *C = F->getComdat();
186 assert(C && "Expected all input GVs to be in a comdat!");
187 ComdatEntriesCovered[C] += 1;
188 }
189
190 auto CheckComdat = [&](Comdat &C) {
191 auto CI = ComdatEntriesCovered.find(&C);
192 if (CI == ComdatEntriesCovered.end())
193 return;
194
195 // If this could have been covered by a dead entry, just subtract one to
196 // account for it.
197 if (CI->second > 0) {
198 CI->second -= 1;
199 return;
200 }
201
202 // If we've already accounted for all the entries that were dead, the
203 // entire comdat is alive so remove it from the map.
204 ComdatEntriesCovered.erase(CI);
205 };
206
207 auto CheckAllComdats = [&] {
208 for (Function &F : M.functions())
209 if (Comdat *C = F.getComdat()) {
210 CheckComdat(*C);
211 if (ComdatEntriesCovered.empty())
212 return;
213 }
214 for (GlobalVariable &GV : M.globals())
215 if (Comdat *C = GV.getComdat()) {
216 CheckComdat(*C);
217 if (ComdatEntriesCovered.empty())
218 return;
219 }
220 for (GlobalAlias &GA : M.aliases())
221 if (Comdat *C = GA.getComdat()) {
222 CheckComdat(*C);
223 if (ComdatEntriesCovered.empty())
224 return;
225 }
226 };
227 CheckAllComdats();
228
229 if (ComdatEntriesCovered.empty()) {
230 DeadComdatFunctions.clear();
231 return;
232 }
233
234 // Remove the entries that were not covering.
235 erase_if(DeadComdatFunctions, [&](GlobalValue *GV) {
236 return ComdatEntriesCovered.find(GV->getComdat()) ==
237 ComdatEntriesCovered.end();
238 });
239 }
240
getUniqueModuleId(Module * M)241 std::string llvm::getUniqueModuleId(Module *M) {
242 MD5 Md5;
243 bool ExportsSymbols = false;
244 auto AddGlobal = [&](GlobalValue &GV) {
245 if (GV.isDeclaration() || GV.getName().startswith("llvm.") ||
246 !GV.hasExternalLinkage() || GV.hasComdat())
247 return;
248 ExportsSymbols = true;
249 Md5.update(GV.getName());
250 Md5.update(ArrayRef<uint8_t>{0});
251 };
252
253 for (auto &F : *M)
254 AddGlobal(F);
255 for (auto &GV : M->globals())
256 AddGlobal(GV);
257 for (auto &GA : M->aliases())
258 AddGlobal(GA);
259 for (auto &IF : M->ifuncs())
260 AddGlobal(IF);
261
262 if (!ExportsSymbols)
263 return "";
264
265 MD5::MD5Result R;
266 Md5.final(R);
267
268 SmallString<32> Str;
269 MD5::stringifyResult(R, Str);
270 return ("$" + Str).str();
271 }
272