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llvm-6502/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp
Peter Collingbourne a90d91fd1a DataFlowSanitizer: fix a use-after-free. Spotted by libgmalloc. 
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188216 91177308-0d34-0410-b5e6-96231b3b80d8
2013-08-12 22:38:39 +00:00

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//===-- DataFlowSanitizer.cpp - dynamic data flow analysis ----------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
/// \file
/// This file is a part of DataFlowSanitizer, a generalised dynamic data flow
/// analysis.
///
/// Unlike other Sanitizer tools, this tool is not designed to detect a specific
/// class of bugs on its own. Instead, it provides a generic dynamic data flow
/// analysis framework to be used by clients to help detect application-specific
/// issues within their own code.
///
/// The analysis is based on automatic propagation of data flow labels (also
/// known as taint labels) through a program as it performs computation. Each
/// byte of application memory is backed by two bytes of shadow memory which
/// hold the label. On Linux/x86_64, memory is laid out as follows:
///
/// +--------------------+ 0x800000000000 (top of memory)
/// | application memory |
/// +--------------------+ 0x700000008000 (kAppAddr)
/// | |
/// | unused |
/// | |
/// +--------------------+ 0x200200000000 (kUnusedAddr)
/// | union table |
/// +--------------------+ 0x200000000000 (kUnionTableAddr)
/// | shadow memory |
/// +--------------------+ 0x000000010000 (kShadowAddr)
/// | reserved by kernel |
/// +--------------------+ 0x000000000000
///
/// To derive a shadow memory address from an application memory address,
/// bits 44-46 are cleared to bring the address into the range
/// [0x000000008000,0x100000000000). Then the address is shifted left by 1 to
/// account for the double byte representation of shadow labels and move the
/// address into the shadow memory range. See the function
/// DataFlowSanitizer::getShadowAddress below.
///
/// For more information, please refer to the design document:
/// http://clang.llvm.org/docs/DataFlowSanitizerDesign.html
#include "llvm/Transforms/Instrumentation.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/DepthFirstIterator.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/IR/InlineAsm.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/MDBuilder.h"
#include "llvm/IR/Type.h"
#include "llvm/IR/Value.h"
#include "llvm/InstVisitor.h"
#include "llvm/Pass.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Transforms/Utils/SpecialCaseList.h"
#include <iterator>
using namespace llvm;
// The -dfsan-preserve-alignment flag controls whether this pass assumes that
// alignment requirements provided by the input IR are correct. For example,
// if the input IR contains a load with alignment 8, this flag will cause
// the shadow load to have alignment 16. This flag is disabled by default as
// we have unfortunately encountered too much code (including Clang itself;
// see PR14291) which performs misaligned access.
static cl::opt<bool> ClPreserveAlignment(
"dfsan-preserve-alignment",
cl::desc("respect alignment requirements provided by input IR"), cl::Hidden,
cl::init(false));
// The greylist file controls how shadow parameters are passed.
// The program acts as though every function in the greylist is passed
// parameters with zero shadow and that its return value also has zero shadow.
// This avoids the use of TLS or extra function parameters to pass shadow state
// and essentially makes the function conform to the "native" (i.e. unsanitized)
// ABI.
static cl::opt<std::string> ClGreylistFile(
"dfsan-greylist",
cl::desc("File containing the list of functions with a native ABI"),
cl::Hidden);
static cl::opt<bool> ClArgsABI(
"dfsan-args-abi",
cl::desc("Use the argument ABI rather than the TLS ABI"),
cl::Hidden);
namespace {
class DataFlowSanitizer : public ModulePass {
friend struct DFSanFunction;
friend class DFSanVisitor;
enum {
ShadowWidth = 16
};
enum InstrumentedABI {
IA_None,
IA_MemOnly,
IA_Args,
IA_TLS
};
DataLayout *DL;
Module *Mod;
LLVMContext *Ctx;
IntegerType *ShadowTy;
PointerType *ShadowPtrTy;
IntegerType *IntptrTy;
ConstantInt *ZeroShadow;
ConstantInt *ShadowPtrMask;
ConstantInt *ShadowPtrMul;
Constant *ArgTLS;
Constant *RetvalTLS;
void *(*GetArgTLSPtr)();
void *(*GetRetvalTLSPtr)();
Constant *GetArgTLS;
Constant *GetRetvalTLS;
FunctionType *DFSanUnionFnTy;
FunctionType *DFSanUnionLoadFnTy;
Constant *DFSanUnionFn;
Constant *DFSanUnionLoadFn;
MDNode *ColdCallWeights;
OwningPtr<SpecialCaseList> Greylist;
DenseMap<Value *, Function *> UnwrappedFnMap;
Value *getShadowAddress(Value *Addr, Instruction *Pos);
Value *combineShadows(Value *V1, Value *V2, Instruction *Pos);
FunctionType *getInstrumentedFunctionType(FunctionType *T);
InstrumentedABI getInstrumentedABI(Function *F);
InstrumentedABI getDefaultInstrumentedABI();
public:
DataFlowSanitizer(void *(*getArgTLS)() = 0, void *(*getRetValTLS)() = 0);
static char ID;
bool doInitialization(Module &M);
bool runOnModule(Module &M);
};
struct DFSanFunction {
DataFlowSanitizer &DFS;
Function *F;
DataFlowSanitizer::InstrumentedABI IA;
Value *ArgTLSPtr;
Value *RetvalTLSPtr;
DenseMap<Value *, Value *> ValShadowMap;
DenseMap<AllocaInst *, AllocaInst *> AllocaShadowMap;
std::vector<std::pair<PHINode *, PHINode *> > PHIFixups;
DenseSet<Instruction *> SkipInsts;
DFSanFunction(DataFlowSanitizer &DFS, Function *F)
: DFS(DFS), F(F), IA(DFS.getInstrumentedABI(F)), ArgTLSPtr(0),
RetvalTLSPtr(0) {}
Value *getArgTLSPtr();
Value *getArgTLS(unsigned Index, Instruction *Pos);
Value *getRetvalTLS();
Value *getShadow(Value *V);
void setShadow(Instruction *I, Value *Shadow);
Value *combineOperandShadows(Instruction *Inst);
Value *loadShadow(Value *ShadowAddr, uint64_t Size, uint64_t Align,
Instruction *Pos);
void storeShadow(Value *Addr, uint64_t Size, uint64_t Align, Value *Shadow,
Instruction *Pos);
};
class DFSanVisitor : public InstVisitor<DFSanVisitor> {
public:
DFSanFunction &DFSF;
DFSanVisitor(DFSanFunction &DFSF) : DFSF(DFSF) {}
void visitOperandShadowInst(Instruction &I);
void visitBinaryOperator(BinaryOperator &BO);
void visitCastInst(CastInst &CI);
void visitCmpInst(CmpInst &CI);
void visitGetElementPtrInst(GetElementPtrInst &GEPI);
void visitLoadInst(LoadInst &LI);
void visitStoreInst(StoreInst &SI);
void visitReturnInst(ReturnInst &RI);
void visitCallSite(CallSite CS);
void visitPHINode(PHINode &PN);
void visitExtractElementInst(ExtractElementInst &I);
void visitInsertElementInst(InsertElementInst &I);
void visitShuffleVectorInst(ShuffleVectorInst &I);
void visitExtractValueInst(ExtractValueInst &I);
void visitInsertValueInst(InsertValueInst &I);
void visitAllocaInst(AllocaInst &I);
void visitSelectInst(SelectInst &I);
void visitMemTransferInst(MemTransferInst &I);
};
}
char DataFlowSanitizer::ID;
INITIALIZE_PASS(DataFlowSanitizer, "dfsan",
"DataFlowSanitizer: dynamic data flow analysis.", false, false)
ModulePass *llvm::createDataFlowSanitizerPass(void *(*getArgTLS)(),
void *(*getRetValTLS)()) {
return new DataFlowSanitizer(getArgTLS, getRetValTLS);
}
DataFlowSanitizer::DataFlowSanitizer(void *(*getArgTLS)(),
void *(*getRetValTLS)())
: ModulePass(ID), GetArgTLSPtr(getArgTLS), GetRetvalTLSPtr(getRetValTLS),
Greylist(SpecialCaseList::createOrDie(ClGreylistFile)) {}
FunctionType *DataFlowSanitizer::getInstrumentedFunctionType(FunctionType *T) {
llvm::SmallVector<Type *, 4> ArgTypes;
std::copy(T->param_begin(), T->param_end(), std::back_inserter(ArgTypes));
for (unsigned i = 0, e = T->getNumParams(); i != e; ++i)
ArgTypes.push_back(ShadowTy);
if (T->isVarArg())
ArgTypes.push_back(ShadowPtrTy);
Type *RetType = T->getReturnType();
if (!RetType->isVoidTy())
RetType = StructType::get(RetType, ShadowTy, (Type *)0);
return FunctionType::get(RetType, ArgTypes, T->isVarArg());
}
bool DataFlowSanitizer::doInitialization(Module &M) {
DL = getAnalysisIfAvailable<DataLayout>();
if (!DL)
return false;
Mod = &M;
Ctx = &M.getContext();
ShadowTy = IntegerType::get(*Ctx, ShadowWidth);
ShadowPtrTy = PointerType::getUnqual(ShadowTy);
IntptrTy = DL->getIntPtrType(*Ctx);
ZeroShadow = ConstantInt::getSigned(ShadowTy, 0);
ShadowPtrMask = ConstantInt::getSigned(IntptrTy, ~0x700000000000LL);
ShadowPtrMul = ConstantInt::getSigned(IntptrTy, ShadowWidth / 8);
Type *DFSanUnionArgs[2] = { ShadowTy, ShadowTy };
DFSanUnionFnTy =
FunctionType::get(ShadowTy, DFSanUnionArgs, /*isVarArg=*/ false);
Type *DFSanUnionLoadArgs[2] = { ShadowPtrTy, IntptrTy };
DFSanUnionLoadFnTy =
FunctionType::get(ShadowTy, DFSanUnionLoadArgs, /*isVarArg=*/ false);
if (GetArgTLSPtr) {
Type *ArgTLSTy = ArrayType::get(ShadowTy, 64);
ArgTLS = 0;
GetArgTLS = ConstantExpr::getIntToPtr(
ConstantInt::get(IntptrTy, uintptr_t(GetArgTLSPtr)),
PointerType::getUnqual(
FunctionType::get(PointerType::getUnqual(ArgTLSTy), (Type *)0)));
}
if (GetRetvalTLSPtr) {
RetvalTLS = 0;
GetRetvalTLS = ConstantExpr::getIntToPtr(
ConstantInt::get(IntptrTy, uintptr_t(GetRetvalTLSPtr)),
PointerType::getUnqual(
FunctionType::get(PointerType::getUnqual(ShadowTy), (Type *)0)));
}
ColdCallWeights = MDBuilder(*Ctx).createBranchWeights(1, 1000);
return true;
}
DataFlowSanitizer::InstrumentedABI
DataFlowSanitizer::getInstrumentedABI(Function *F) {
if (Greylist->isIn(*F))
return IA_MemOnly;
else
return getDefaultInstrumentedABI();
}
DataFlowSanitizer::InstrumentedABI
DataFlowSanitizer::getDefaultInstrumentedABI() {
return ClArgsABI ? IA_Args : IA_TLS;
}
bool DataFlowSanitizer::runOnModule(Module &M) {
if (!DL)
return false;
if (!GetArgTLSPtr) {
Type *ArgTLSTy = ArrayType::get(ShadowTy, 64);
ArgTLS = Mod->getOrInsertGlobal("__dfsan_arg_tls", ArgTLSTy);
if (GlobalVariable *G = dyn_cast<GlobalVariable>(ArgTLS))
G->setThreadLocalMode(GlobalVariable::InitialExecTLSModel);
}
if (!GetRetvalTLSPtr) {
RetvalTLS = Mod->getOrInsertGlobal("__dfsan_retval_tls", ShadowTy);
if (GlobalVariable *G = dyn_cast<GlobalVariable>(RetvalTLS))
G->setThreadLocalMode(GlobalVariable::InitialExecTLSModel);
}
DFSanUnionFn = Mod->getOrInsertFunction("__dfsan_union", DFSanUnionFnTy);
if (Function *F = dyn_cast<Function>(DFSanUnionFn)) {
F->addAttribute(AttributeSet::FunctionIndex, Attribute::ReadNone);
F->addAttribute(AttributeSet::ReturnIndex, Attribute::ZExt);
F->addAttribute(1, Attribute::ZExt);
F->addAttribute(2, Attribute::ZExt);
}
DFSanUnionLoadFn =
Mod->getOrInsertFunction("__dfsan_union_load", DFSanUnionLoadFnTy);
if (Function *F = dyn_cast<Function>(DFSanUnionLoadFn)) {
F->addAttribute(AttributeSet::ReturnIndex, Attribute::ZExt);
}
std::vector<Function *> FnsToInstrument;
for (Module::iterator i = M.begin(), e = M.end(); i != e; ++i) {
if (!i->isIntrinsic() && i != DFSanUnionFn && i != DFSanUnionLoadFn)
FnsToInstrument.push_back(&*i);
}
// First, change the ABI of every function in the module. Greylisted
// functions keep their original ABI and get a wrapper function.
for (std::vector<Function *>::iterator i = FnsToInstrument.begin(),
e = FnsToInstrument.end();
i != e; ++i) {
Function &F = **i;
FunctionType *FT = F.getFunctionType();
FunctionType *NewFT = getInstrumentedFunctionType(FT);
// If the function types are the same (i.e. void()), we don't need to do
// anything here.
if (FT != NewFT) {
switch (getInstrumentedABI(&F)) {
case IA_Args: {
Function *NewF = Function::Create(NewFT, F.getLinkage(), "", &M);
NewF->setCallingConv(F.getCallingConv());
NewF->setAttributes(F.getAttributes().removeAttributes(
*Ctx, AttributeSet::ReturnIndex,
AttributeFuncs::typeIncompatible(NewFT->getReturnType(),
AttributeSet::ReturnIndex)));
for (Function::arg_iterator FArg = F.arg_begin(),
NewFArg = NewF->arg_begin(),
FArgEnd = F.arg_end();
FArg != FArgEnd; ++FArg, ++NewFArg) {
FArg->replaceAllUsesWith(NewFArg);
}
NewF->getBasicBlockList().splice(NewF->begin(), F.getBasicBlockList());
for (Function::use_iterator ui = F.use_begin(), ue = F.use_end();
ui != ue;) {
BlockAddress *BA = dyn_cast<BlockAddress>(ui.getUse().getUser());
++ui;
if (BA) {
BA->replaceAllUsesWith(
BlockAddress::get(NewF, BA->getBasicBlock()));
delete BA;
}
}
F.replaceAllUsesWith(
ConstantExpr::getBitCast(NewF, PointerType::getUnqual(FT)));
NewF->takeName(&F);
F.eraseFromParent();
*i = NewF;
break;
}
case IA_MemOnly: {
assert(!FT->isVarArg() && "varargs not handled here yet");
assert(getDefaultInstrumentedABI() == IA_Args);
Function *NewF =
Function::Create(NewFT, GlobalValue::LinkOnceODRLinkage,
std::string("dfsw$") + F.getName(), &M);
NewF->setCallingConv(F.getCallingConv());
NewF->setAttributes(F.getAttributes());
BasicBlock *BB = BasicBlock::Create(*Ctx, "entry", NewF);
std::vector<Value *> Args;
unsigned n = FT->getNumParams();
for (Function::arg_iterator i = NewF->arg_begin(); n != 0; ++i, --n)
Args.push_back(&*i);
CallInst *CI = CallInst::Create(&F, Args, "", BB);
if (FT->getReturnType()->isVoidTy())
ReturnInst::Create(*Ctx, BB);
else {
Value *InsVal = InsertValueInst::Create(
UndefValue::get(NewFT->getReturnType()), CI, 0, "", BB);
Value *InsShadow =
InsertValueInst::Create(InsVal, ZeroShadow, 1, "", BB);
ReturnInst::Create(*Ctx, InsShadow, BB);
}
Value *WrappedFnCst =
ConstantExpr::getBitCast(NewF, PointerType::getUnqual(FT));
F.replaceAllUsesWith(WrappedFnCst);
UnwrappedFnMap[WrappedFnCst] = &F;
break;
}
default:
break;
}
}
}
for (std::vector<Function *>::iterator i = FnsToInstrument.begin(),
e = FnsToInstrument.end();
i != e; ++i) {
if ((*i)->isDeclaration())
continue;
removeUnreachableBlocks(**i);
DFSanFunction DFSF(*this, *i);
// DFSanVisitor may create new basic blocks, which confuses df_iterator.
// Build a copy of the list before iterating over it.
llvm::SmallVector<BasicBlock *, 4> BBList;
std::copy(df_begin(&(*i)->getEntryBlock()), df_end(&(*i)->getEntryBlock()),
std::back_inserter(BBList));
for (llvm::SmallVector<BasicBlock *, 4>::iterator i = BBList.begin(),
e = BBList.end();
i != e; ++i) {
Instruction *Inst = &(*i)->front();
while (1) {
// DFSanVisitor may split the current basic block, changing the current
// instruction's next pointer and moving the next instruction to the
// tail block from which we should continue.
Instruction *Next = Inst->getNextNode();
// DFSanVisitor may delete Inst, so keep track of whether it was a
// terminator.
bool IsTerminator = isa<TerminatorInst>(Inst);
if (!DFSF.SkipInsts.count(Inst))
DFSanVisitor(DFSF).visit(Inst);
if (IsTerminator)
break;
Inst = Next;
}
}
for (std::vector<std::pair<PHINode *, PHINode *> >::iterator
i = DFSF.PHIFixups.begin(),
e = DFSF.PHIFixups.end();
i != e; ++i) {
for (unsigned val = 0, n = i->first->getNumIncomingValues(); val != n;
++val) {
i->second->setIncomingValue(
val, DFSF.getShadow(i->first->getIncomingValue(val)));
}
}
}
return false;
}
Value *DFSanFunction::getArgTLSPtr() {
if (ArgTLSPtr)
return ArgTLSPtr;
if (DFS.ArgTLS)
return ArgTLSPtr = DFS.ArgTLS;
IRBuilder<> IRB(F->getEntryBlock().begin());
return ArgTLSPtr = IRB.CreateCall(DFS.GetArgTLS);
}
Value *DFSanFunction::getRetvalTLS() {
if (RetvalTLSPtr)
return RetvalTLSPtr;
if (DFS.RetvalTLS)
return RetvalTLSPtr = DFS.RetvalTLS;
IRBuilder<> IRB(F->getEntryBlock().begin());
return RetvalTLSPtr = IRB.CreateCall(DFS.GetRetvalTLS);
}
Value *DFSanFunction::getArgTLS(unsigned Idx, Instruction *Pos) {
IRBuilder<> IRB(Pos);
return IRB.CreateConstGEP2_64(getArgTLSPtr(), 0, Idx);
}
Value *DFSanFunction::getShadow(Value *V) {
if (!isa<Argument>(V) && !isa<Instruction>(V))
return DFS.ZeroShadow;
Value *&Shadow = ValShadowMap[V];
if (!Shadow) {
if (Argument *A = dyn_cast<Argument>(V)) {
switch (IA) {
case DataFlowSanitizer::IA_TLS: {
Value *ArgTLSPtr = getArgTLSPtr();
Instruction *ArgTLSPos =
DFS.ArgTLS ? &*F->getEntryBlock().begin()
: cast<Instruction>(ArgTLSPtr)->getNextNode();
IRBuilder<> IRB(ArgTLSPos);
Shadow = IRB.CreateLoad(getArgTLS(A->getArgNo(), ArgTLSPos));
break;
}
case DataFlowSanitizer::IA_Args: {
unsigned ArgIdx = A->getArgNo() + F->getArgumentList().size() / 2;
Function::arg_iterator i = F->arg_begin();
while (ArgIdx--)
++i;
Shadow = i;
break;
}
default:
Shadow = DFS.ZeroShadow;
break;
}
} else {
Shadow = DFS.ZeroShadow;
}
}
return Shadow;
}
void DFSanFunction::setShadow(Instruction *I, Value *Shadow) {
assert(!ValShadowMap.count(I));
assert(Shadow->getType() == DFS.ShadowTy);
ValShadowMap[I] = Shadow;
}
Value *DataFlowSanitizer::getShadowAddress(Value *Addr, Instruction *Pos) {
assert(Addr != RetvalTLS && "Reinstrumenting?");
IRBuilder<> IRB(Pos);
return IRB.CreateIntToPtr(
IRB.CreateMul(
IRB.CreateAnd(IRB.CreatePtrToInt(Addr, IntptrTy), ShadowPtrMask),
ShadowPtrMul),
ShadowPtrTy);
}
// Generates IR to compute the union of the two given shadows, inserting it
// before Pos. Returns the computed union Value.
Value *DataFlowSanitizer::combineShadows(Value *V1, Value *V2,
Instruction *Pos) {
if (V1 == ZeroShadow)
return V2;
if (V2 == ZeroShadow)
return V1;
if (V1 == V2)
return V1;
IRBuilder<> IRB(Pos);
BasicBlock *Head = Pos->getParent();
Value *Ne = IRB.CreateICmpNE(V1, V2);
Instruction *NeInst = dyn_cast<Instruction>(Ne);
if (NeInst) {
BranchInst *BI = cast<BranchInst>(SplitBlockAndInsertIfThen(
NeInst, /*Unreachable=*/ false, ColdCallWeights));
IRBuilder<> ThenIRB(BI);
CallInst *Call = ThenIRB.CreateCall2(DFSanUnionFn, V1, V2);
Call->addAttribute(AttributeSet::ReturnIndex, Attribute::ZExt);
Call->addAttribute(1, Attribute::ZExt);
Call->addAttribute(2, Attribute::ZExt);
BasicBlock *Tail = BI->getSuccessor(0);
PHINode *Phi = PHINode::Create(ShadowTy, 2, "", Tail->begin());
Phi->addIncoming(Call, Call->getParent());
Phi->addIncoming(ZeroShadow, Head);
Pos = Phi;
return Phi;
} else {
assert(0 && "todo");
return 0;
}
}
// A convenience function which folds the shadows of each of the operands
// of the provided instruction Inst, inserting the IR before Inst. Returns
// the computed union Value.
Value *DFSanFunction::combineOperandShadows(Instruction *Inst) {
if (Inst->getNumOperands() == 0)
return DFS.ZeroShadow;
Value *Shadow = getShadow(Inst->getOperand(0));
for (unsigned i = 1, n = Inst->getNumOperands(); i != n; ++i) {
Shadow = DFS.combineShadows(Shadow, getShadow(Inst->getOperand(i)), Inst);
}
return Shadow;
}
void DFSanVisitor::visitOperandShadowInst(Instruction &I) {
Value *CombinedShadow = DFSF.combineOperandShadows(&I);
DFSF.setShadow(&I, CombinedShadow);
}
// Generates IR to load shadow corresponding to bytes [Addr, Addr+Size), where
// Addr has alignment Align, and take the union of each of those shadows.
Value *DFSanFunction::loadShadow(Value *Addr, uint64_t Size, uint64_t Align,
Instruction *Pos) {
if (AllocaInst *AI = dyn_cast<AllocaInst>(Addr)) {
llvm::DenseMap<AllocaInst *, AllocaInst *>::iterator i =
AllocaShadowMap.find(AI);
if (i != AllocaShadowMap.end()) {
IRBuilder<> IRB(Pos);
return IRB.CreateLoad(i->second);
}
}
uint64_t ShadowAlign = Align * DFS.ShadowWidth / 8;
SmallVector<Value *, 2> Objs;
GetUnderlyingObjects(Addr, Objs, DFS.DL);
bool AllConstants = true;
for (SmallVector<Value *, 2>::iterator i = Objs.begin(), e = Objs.end();
i != e; ++i) {
if (isa<Function>(*i) || isa<BlockAddress>(*i))
continue;
if (isa<GlobalVariable>(*i) && cast<GlobalVariable>(*i)->isConstant())
continue;
AllConstants = false;
break;
}
if (AllConstants)
return DFS.ZeroShadow;
Value *ShadowAddr = DFS.getShadowAddress(Addr, Pos);
switch (Size) {
case 0:
return DFS.ZeroShadow;
case 1: {
LoadInst *LI = new LoadInst(ShadowAddr, "", Pos);
LI->setAlignment(ShadowAlign);
return LI;
}
case 2: {
IRBuilder<> IRB(Pos);
Value *ShadowAddr1 =
IRB.CreateGEP(ShadowAddr, ConstantInt::get(DFS.IntptrTy, 1));
return DFS.combineShadows(IRB.CreateAlignedLoad(ShadowAddr, ShadowAlign),
IRB.CreateAlignedLoad(ShadowAddr1, ShadowAlign),
Pos);
}
}
if (Size % (64 / DFS.ShadowWidth) == 0) {
// Fast path for the common case where each byte has identical shadow: load
// shadow 64 bits at a time, fall out to a __dfsan_union_load call if any
// shadow is non-equal.
BasicBlock *FallbackBB = BasicBlock::Create(*DFS.Ctx, "", F);
IRBuilder<> FallbackIRB(FallbackBB);
CallInst *FallbackCall = FallbackIRB.CreateCall2(
DFS.DFSanUnionLoadFn, ShadowAddr, ConstantInt::get(DFS.IntptrTy, Size));
FallbackCall->addAttribute(AttributeSet::ReturnIndex, Attribute::ZExt);
// Compare each of the shadows stored in the loaded 64 bits to each other,
// by computing (WideShadow rotl ShadowWidth) == WideShadow.
IRBuilder<> IRB(Pos);
Value *WideAddr =
IRB.CreateBitCast(ShadowAddr, Type::getInt64PtrTy(*DFS.Ctx));
Value *WideShadow = IRB.CreateAlignedLoad(WideAddr, ShadowAlign);
Value *TruncShadow = IRB.CreateTrunc(WideShadow, DFS.ShadowTy);
Value *ShlShadow = IRB.CreateShl(WideShadow, DFS.ShadowWidth);
Value *ShrShadow = IRB.CreateLShr(WideShadow, 64 - DFS.ShadowWidth);
Value *RotShadow = IRB.CreateOr(ShlShadow, ShrShadow);
Value *ShadowsEq = IRB.CreateICmpEQ(WideShadow, RotShadow);
BasicBlock *Head = Pos->getParent();
BasicBlock *Tail = Head->splitBasicBlock(Pos);
// In the following code LastBr will refer to the previous basic block's
// conditional branch instruction, whose true successor is fixed up to point
// to the next block during the loop below or to the tail after the final
// iteration.
BranchInst *LastBr = BranchInst::Create(FallbackBB, FallbackBB, ShadowsEq);
ReplaceInstWithInst(Head->getTerminator(), LastBr);
for (uint64_t Ofs = 64 / DFS.ShadowWidth; Ofs != Size;
Ofs += 64 / DFS.ShadowWidth) {
BasicBlock *NextBB = BasicBlock::Create(*DFS.Ctx, "", F);
IRBuilder<> NextIRB(NextBB);
WideAddr = NextIRB.CreateGEP(WideAddr, ConstantInt::get(DFS.IntptrTy, 1));
Value *NextWideShadow = NextIRB.CreateAlignedLoad(WideAddr, ShadowAlign);
ShadowsEq = NextIRB.CreateICmpEQ(WideShadow, NextWideShadow);
LastBr->setSuccessor(0, NextBB);
LastBr = NextIRB.CreateCondBr(ShadowsEq, FallbackBB, FallbackBB);
}
LastBr->setSuccessor(0, Tail);
FallbackIRB.CreateBr(Tail);
PHINode *Shadow = PHINode::Create(DFS.ShadowTy, 2, "", &Tail->front());
Shadow->addIncoming(FallbackCall, FallbackBB);
Shadow->addIncoming(TruncShadow, LastBr->getParent());
return Shadow;
}
IRBuilder<> IRB(Pos);
CallInst *FallbackCall = IRB.CreateCall2(
DFS.DFSanUnionLoadFn, ShadowAddr, ConstantInt::get(DFS.IntptrTy, Size));
FallbackCall->addAttribute(AttributeSet::ReturnIndex, Attribute::ZExt);
return FallbackCall;
}
void DFSanVisitor::visitLoadInst(LoadInst &LI) {
uint64_t Size = DFSF.DFS.DL->getTypeStoreSize(LI.getType());
uint64_t Align;
if (ClPreserveAlignment) {
Align = LI.getAlignment();
if (Align == 0)
Align = DFSF.DFS.DL->getABITypeAlignment(LI.getType());
} else {
Align = 1;
}
IRBuilder<> IRB(&LI);
Value *LoadedShadow =
DFSF.loadShadow(LI.getPointerOperand(), Size, Align, &LI);
Value *PtrShadow = DFSF.getShadow(LI.getPointerOperand());
DFSF.setShadow(&LI, DFSF.DFS.combineShadows(LoadedShadow, PtrShadow, &LI));
}
void DFSanFunction::storeShadow(Value *Addr, uint64_t Size, uint64_t Align,
Value *Shadow, Instruction *Pos) {
if (AllocaInst *AI = dyn_cast<AllocaInst>(Addr)) {
llvm::DenseMap<AllocaInst *, AllocaInst *>::iterator i =
AllocaShadowMap.find(AI);
if (i != AllocaShadowMap.end()) {
IRBuilder<> IRB(Pos);
IRB.CreateStore(Shadow, i->second);
return;
}
}
uint64_t ShadowAlign = Align * DFS.ShadowWidth / 8;
IRBuilder<> IRB(Pos);
Value *ShadowAddr = DFS.getShadowAddress(Addr, Pos);
if (Shadow == DFS.ZeroShadow) {
IntegerType *ShadowTy = IntegerType::get(*DFS.Ctx, Size * DFS.ShadowWidth);
Value *ExtZeroShadow = ConstantInt::get(ShadowTy, 0);
Value *ExtShadowAddr =
IRB.CreateBitCast(ShadowAddr, PointerType::getUnqual(ShadowTy));
IRB.CreateAlignedStore(ExtZeroShadow, ExtShadowAddr, ShadowAlign);
return;
}
const unsigned ShadowVecSize = 128 / DFS.ShadowWidth;
uint64_t Offset = 0;
if (Size >= ShadowVecSize) {
VectorType *ShadowVecTy = VectorType::get(DFS.ShadowTy, ShadowVecSize);
Value *ShadowVec = UndefValue::get(ShadowVecTy);
for (unsigned i = 0; i != ShadowVecSize; ++i) {
ShadowVec = IRB.CreateInsertElement(
ShadowVec, Shadow, ConstantInt::get(Type::getInt32Ty(*DFS.Ctx), i));
}
Value *ShadowVecAddr =
IRB.CreateBitCast(ShadowAddr, PointerType::getUnqual(ShadowVecTy));
do {
Value *CurShadowVecAddr = IRB.CreateConstGEP1_32(ShadowVecAddr, Offset);
IRB.CreateAlignedStore(ShadowVec, CurShadowVecAddr, ShadowAlign);
Size -= ShadowVecSize;
++Offset;
} while (Size >= ShadowVecSize);
Offset *= ShadowVecSize;
}
while (Size > 0) {
Value *CurShadowAddr = IRB.CreateConstGEP1_32(ShadowAddr, Offset);
IRB.CreateAlignedStore(Shadow, CurShadowAddr, ShadowAlign);
--Size;
++Offset;
}
}
void DFSanVisitor::visitStoreInst(StoreInst &SI) {
uint64_t Size =
DFSF.DFS.DL->getTypeStoreSize(SI.getValueOperand()->getType());
uint64_t Align;
if (ClPreserveAlignment) {
Align = SI.getAlignment();
if (Align == 0)
Align = DFSF.DFS.DL->getABITypeAlignment(SI.getValueOperand()->getType());
} else {
Align = 1;
}
DFSF.storeShadow(SI.getPointerOperand(), Size, Align,
DFSF.getShadow(SI.getValueOperand()), &SI);
}
void DFSanVisitor::visitBinaryOperator(BinaryOperator &BO) {
visitOperandShadowInst(BO);
}
void DFSanVisitor::visitCastInst(CastInst &CI) { visitOperandShadowInst(CI); }
void DFSanVisitor::visitCmpInst(CmpInst &CI) { visitOperandShadowInst(CI); }
void DFSanVisitor::visitGetElementPtrInst(GetElementPtrInst &GEPI) {
visitOperandShadowInst(GEPI);
}
void DFSanVisitor::visitExtractElementInst(ExtractElementInst &I) {
visitOperandShadowInst(I);
}
void DFSanVisitor::visitInsertElementInst(InsertElementInst &I) {
visitOperandShadowInst(I);
}
void DFSanVisitor::visitShuffleVectorInst(ShuffleVectorInst &I) {
visitOperandShadowInst(I);
}
void DFSanVisitor::visitExtractValueInst(ExtractValueInst &I) {
visitOperandShadowInst(I);
}
void DFSanVisitor::visitInsertValueInst(InsertValueInst &I) {
visitOperandShadowInst(I);
}
void DFSanVisitor::visitAllocaInst(AllocaInst &I) {
bool AllLoadsStores = true;
for (Instruction::use_iterator i = I.use_begin(), e = I.use_end(); i != e;
++i) {
if (isa<LoadInst>(*i))
continue;
if (StoreInst *SI = dyn_cast<StoreInst>(*i)) {
if (SI->getPointerOperand() == &I)
continue;
}
AllLoadsStores = false;
break;
}
if (AllLoadsStores) {
IRBuilder<> IRB(&I);
DFSF.AllocaShadowMap[&I] = IRB.CreateAlloca(DFSF.DFS.ShadowTy);
}
DFSF.setShadow(&I, DFSF.DFS.ZeroShadow);
}
void DFSanVisitor::visitSelectInst(SelectInst &I) {
Value *CondShadow = DFSF.getShadow(I.getCondition());
Value *TrueShadow = DFSF.getShadow(I.getTrueValue());
Value *FalseShadow = DFSF.getShadow(I.getFalseValue());
if (isa<VectorType>(I.getCondition()->getType())) {
DFSF.setShadow(
&I, DFSF.DFS.combineShadows(
CondShadow,
DFSF.DFS.combineShadows(TrueShadow, FalseShadow, &I), &I));
} else {
Value *ShadowSel;
if (TrueShadow == FalseShadow) {
ShadowSel = TrueShadow;
} else {
ShadowSel =
SelectInst::Create(I.getCondition(), TrueShadow, FalseShadow, "", &I);
}
DFSF.setShadow(&I, DFSF.DFS.combineShadows(CondShadow, ShadowSel, &I));
}
}
void DFSanVisitor::visitMemTransferInst(MemTransferInst &I) {
IRBuilder<> IRB(&I);
Value *DestShadow = DFSF.DFS.getShadowAddress(I.getDest(), &I);
Value *SrcShadow = DFSF.DFS.getShadowAddress(I.getSource(), &I);
Value *LenShadow = IRB.CreateMul(
I.getLength(),
ConstantInt::get(I.getLength()->getType(), DFSF.DFS.ShadowWidth / 8));
Value *AlignShadow;
if (ClPreserveAlignment) {
AlignShadow = IRB.CreateMul(I.getAlignmentCst(),
ConstantInt::get(I.getAlignmentCst()->getType(),
DFSF.DFS.ShadowWidth / 8));
} else {
AlignShadow = ConstantInt::get(I.getAlignmentCst()->getType(),
DFSF.DFS.ShadowWidth / 8);
}
Type *Int8Ptr = Type::getInt8PtrTy(*DFSF.DFS.Ctx);
DestShadow = IRB.CreateBitCast(DestShadow, Int8Ptr);
SrcShadow = IRB.CreateBitCast(SrcShadow, Int8Ptr);
IRB.CreateCall5(I.getCalledValue(), DestShadow, SrcShadow, LenShadow,
AlignShadow, I.getVolatileCst());
}
void DFSanVisitor::visitReturnInst(ReturnInst &RI) {
if (RI.getReturnValue()) {
switch (DFSF.IA) {
case DataFlowSanitizer::IA_TLS: {
Value *S = DFSF.getShadow(RI.getReturnValue());
IRBuilder<> IRB(&RI);
IRB.CreateStore(S, DFSF.getRetvalTLS());
break;
}
case DataFlowSanitizer::IA_Args: {
IRBuilder<> IRB(&RI);
Type *RT = DFSF.F->getFunctionType()->getReturnType();
Value *InsVal =
IRB.CreateInsertValue(UndefValue::get(RT), RI.getReturnValue(), 0);
Value *InsShadow =
IRB.CreateInsertValue(InsVal, DFSF.getShadow(RI.getReturnValue()), 1);
RI.setOperand(0, InsShadow);
break;
}
default:
break;
}
}
}
void DFSanVisitor::visitCallSite(CallSite CS) {
Function *F = CS.getCalledFunction();
if ((F && F->isIntrinsic()) || isa<InlineAsm>(CS.getCalledValue())) {
visitOperandShadowInst(*CS.getInstruction());
return;
}
DenseMap<Value *, Function *>::iterator i =
DFSF.DFS.UnwrappedFnMap.find(CS.getCalledValue());
if (i != DFSF.DFS.UnwrappedFnMap.end()) {
CS.setCalledFunction(i->second);
DFSF.setShadow(CS.getInstruction(), DFSF.DFS.ZeroShadow);
return;
}
IRBuilder<> IRB(CS.getInstruction());
FunctionType *FT = cast<FunctionType>(
CS.getCalledValue()->getType()->getPointerElementType());
if (DFSF.DFS.getDefaultInstrumentedABI() == DataFlowSanitizer::IA_TLS) {
for (unsigned i = 0, n = FT->getNumParams(); i != n; ++i) {
IRB.CreateStore(DFSF.getShadow(CS.getArgument(i)),
DFSF.getArgTLS(i, CS.getInstruction()));
}
}
Instruction *Next = 0;
if (!CS.getType()->isVoidTy()) {
if (InvokeInst *II = dyn_cast<InvokeInst>(CS.getInstruction())) {
if (II->getNormalDest()->getSinglePredecessor()) {
Next = II->getNormalDest()->begin();
} else {
BasicBlock *NewBB =
SplitEdge(II->getParent(), II->getNormalDest(), &DFSF.DFS);
Next = NewBB->begin();
}
} else {
Next = CS->getNextNode();
}
if (DFSF.DFS.getDefaultInstrumentedABI() == DataFlowSanitizer::IA_TLS) {
IRBuilder<> NextIRB(Next);
LoadInst *LI = NextIRB.CreateLoad(DFSF.getRetvalTLS());
DFSF.SkipInsts.insert(LI);
DFSF.setShadow(CS.getInstruction(), LI);
}
}
// Do all instrumentation for IA_Args down here to defer tampering with the
// CFG in a way that SplitEdge may be able to detect.
if (DFSF.DFS.getDefaultInstrumentedABI() == DataFlowSanitizer::IA_Args) {
FunctionType *NewFT = DFSF.DFS.getInstrumentedFunctionType(FT);
Value *Func =
IRB.CreateBitCast(CS.getCalledValue(), PointerType::getUnqual(NewFT));
std::vector<Value *> Args;
CallSite::arg_iterator i = CS.arg_begin(), e = CS.arg_end();
for (unsigned n = FT->getNumParams(); n != 0; ++i, --n)
Args.push_back(*i);
i = CS.arg_begin();
for (unsigned n = FT->getNumParams(); n != 0; ++i, --n)
Args.push_back(DFSF.getShadow(*i));
if (FT->isVarArg()) {
unsigned VarArgSize = CS.arg_size() - FT->getNumParams();
ArrayType *VarArgArrayTy = ArrayType::get(DFSF.DFS.ShadowTy, VarArgSize);
AllocaInst *VarArgShadow =
new AllocaInst(VarArgArrayTy, "", DFSF.F->getEntryBlock().begin());
Args.push_back(IRB.CreateConstGEP2_32(VarArgShadow, 0, 0));
for (unsigned n = 0; i != e; ++i, ++n) {
IRB.CreateStore(DFSF.getShadow(*i),
IRB.CreateConstGEP2_32(VarArgShadow, 0, n));
Args.push_back(*i);
}
}
CallSite NewCS;
if (InvokeInst *II = dyn_cast<InvokeInst>(CS.getInstruction())) {
NewCS = IRB.CreateInvoke(Func, II->getNormalDest(), II->getUnwindDest(),
Args);
} else {
NewCS = IRB.CreateCall(Func, Args);
}
NewCS.setCallingConv(CS.getCallingConv());
NewCS.setAttributes(CS.getAttributes().removeAttributes(
*DFSF.DFS.Ctx, AttributeSet::ReturnIndex,
AttributeFuncs::typeIncompatible(NewCS.getInstruction()->getType(),
AttributeSet::ReturnIndex)));
if (Next) {
ExtractValueInst *ExVal =
ExtractValueInst::Create(NewCS.getInstruction(), 0, "", Next);
DFSF.SkipInsts.insert(ExVal);
ExtractValueInst *ExShadow =
ExtractValueInst::Create(NewCS.getInstruction(), 1, "", Next);
DFSF.SkipInsts.insert(ExShadow);
DFSF.setShadow(ExVal, ExShadow);
CS.getInstruction()->replaceAllUsesWith(ExVal);
}
CS.getInstruction()->eraseFromParent();
}
}
void DFSanVisitor::visitPHINode(PHINode &PN) {
PHINode *ShadowPN =
PHINode::Create(DFSF.DFS.ShadowTy, PN.getNumIncomingValues(), "", &PN);
// Give the shadow phi node valid predecessors to fool SplitEdge into working.
Value *UndefShadow = UndefValue::get(DFSF.DFS.ShadowTy);
for (PHINode::block_iterator i = PN.block_begin(), e = PN.block_end(); i != e;
++i) {
ShadowPN->addIncoming(UndefShadow, *i);
}
DFSF.PHIFixups.push_back(std::make_pair(&PN, ShadowPN));
DFSF.setShadow(&PN, ShadowPN);
}
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