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[ASan] Use llvm.global_ctors to insert init-order checking calls into ASan runtime.
Don't assume that dynamically initialized globals are all initialized from _GLOBAL__<module_name>I_ function. Instead, scan the llvm.global_ctors and insert poison/unpoison calls to each function there. Patch by Nico Weber! git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209780 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -391,6 +391,7 @@ class AddressSanitizerModule : public ModulePass {
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void initializeCallbacks(Module &M);
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bool ShouldInstrumentGlobal(GlobalVariable *G);
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void poisonOneInitializer(Function &GlobalInit, GlobalValue *ModuleName);
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void createInitializerPoisonCalls(Module &M, GlobalValue *ModuleName);
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size_t MinRedzoneSizeForGlobal() const {
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return RedzoneSizeForScale(Mapping.Scale);
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@ -851,48 +852,36 @@ void AddressSanitizer::instrumentAddress(Instruction *OrigIns,
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Crash->setDebugLoc(OrigIns->getDebugLoc());
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}
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void AddressSanitizerModule::createInitializerPoisonCalls(
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Module &M, GlobalValue *ModuleName) {
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// We do all of our poisoning and unpoisoning within a global constructor.
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// These are called _GLOBAL__(sub_)?I_.*.
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// TODO: Consider looking through the functions in
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// M.getGlobalVariable("llvm.global_ctors") instead of using this stringly
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// typed approach.
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Function *GlobalInit = nullptr;
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for (auto &F : M.getFunctionList()) {
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StringRef FName = F.getName();
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const char kGlobalPrefix[] = "_GLOBAL__";
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if (!FName.startswith(kGlobalPrefix))
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continue;
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FName = FName.substr(strlen(kGlobalPrefix));
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const char kOptionalSub[] = "sub_";
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if (FName.startswith(kOptionalSub))
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FName = FName.substr(strlen(kOptionalSub));
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if (FName.startswith("I_")) {
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GlobalInit = &F;
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break;
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}
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}
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// If that function is not present, this TU contains no globals, or they have
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// all been optimized away
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if (!GlobalInit)
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return;
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void AddressSanitizerModule::poisonOneInitializer(Function &GlobalInit,
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GlobalValue *ModuleName) {
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// Set up the arguments to our poison/unpoison functions.
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IRBuilder<> IRB(GlobalInit->begin()->getFirstInsertionPt());
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IRBuilder<> IRB(GlobalInit.begin()->getFirstInsertionPt());
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// Add a call to poison all external globals before the given function starts.
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Value *ModuleNameAddr = ConstantExpr::getPointerCast(ModuleName, IntptrTy);
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IRB.CreateCall(AsanPoisonGlobals, ModuleNameAddr);
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// Add calls to unpoison all globals before each return instruction.
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for (Function::iterator I = GlobalInit->begin(), E = GlobalInit->end();
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I != E; ++I) {
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if (ReturnInst *RI = dyn_cast<ReturnInst>(I->getTerminator())) {
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for (auto &BB : GlobalInit.getBasicBlockList())
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if (ReturnInst *RI = dyn_cast<ReturnInst>(BB.getTerminator()))
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CallInst::Create(AsanUnpoisonGlobals, "", RI);
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}
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void AddressSanitizerModule::createInitializerPoisonCalls(
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Module &M, GlobalValue *ModuleName) {
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GlobalVariable *GV = M.getGlobalVariable("llvm.global_ctors");
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ConstantArray *CA = cast<ConstantArray>(GV->getInitializer());
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for (Use &OP : CA->operands()) {
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if (isa<ConstantAggregateZero>(OP))
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continue;
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ConstantStruct *CS = cast<ConstantStruct>(OP);
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// Must have a function or null ptr.
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// (CS->getOperand(0) is the init priority.)
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if (Function* F = dyn_cast<Function>(CS->getOperand(1))) {
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if (F->getName() != kAsanModuleCtorName)
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poisonOneInitializer(*F, ModuleName);
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}
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}
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}
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@ -23,6 +23,8 @@ entry:
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ret void
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}
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@llvm.global_ctors = appending global [1 x { i32, void ()* }] [{ i32, void ()* } { i32 65535, void ()* @_GLOBAL__I_a }]
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define internal void @_GLOBAL__I_a() sanitize_address section ".text.startup" {
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entry:
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call void @__cxx_global_var_init()
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