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//===-- MemorySanitizer.cpp - detector of uninitialized reads -------------===//
//
// 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 MemorySanitizer, a detector of uninitialized
/// reads.
///
/// Status: early prototype.
///
/// The algorithm of the tool is similar to Memcheck
/// (http://goo.gl/QKbem). We associate a few shadow bits with every
/// byte of the application memory, poison the shadow of the malloc-ed
/// or alloca-ed memory, load the shadow bits on every memory read,
/// propagate the shadow bits through some of the arithmetic
/// instruction (including MOV), store the shadow bits on every memory
/// write, report a bug on some other instructions (e.g. JMP) if the
/// associated shadow is poisoned.
///
/// But there are differences too. The first and the major one:
/// compiler instrumentation instead of binary instrumentation. This
/// gives us much better register allocation, possible compiler
/// optimizations and a fast start-up. But this brings the major issue
/// as well: msan needs to see all program events, including system
/// calls and reads/writes in system libraries, so we either need to
/// compile *everything* with msan or use a binary translation
/// component (e.g. DynamoRIO) to instrument pre-built libraries.
/// Another difference from Memcheck is that we use 8 shadow bits per
/// byte of application memory and use a direct shadow mapping. This
/// greatly simplifies the instrumentation code and avoids races on
/// shadow updates (Memcheck is single-threaded so races are not a
/// concern there. Memcheck uses 2 shadow bits per byte with a slow
/// path storage that uses 8 bits per byte).
///
/// The default value of shadow is 0, which means "clean" (not poisoned).
///
/// Every module initializer should call __msan_init to ensure that the
/// shadow memory is ready. On error, __msan_warning is called. Since
/// parameters and return values may be passed via registers, we have a
/// specialized thread-local shadow for return values
/// (__msan_retval_tls) and parameters (__msan_param_tls).
///
/// Origin tracking.
///
/// MemorySanitizer can track origins (allocation points) of all uninitialized
/// values. This behavior is controlled with a flag (msan-track-origins) and is
/// disabled by default.
///
/// Origins are 4-byte values created and interpreted by the runtime library.
/// They are stored in a second shadow mapping, one 4-byte value for 4 bytes
/// of application memory. Propagation of origins is basically a bunch of
/// "select" instructions that pick the origin of a dirty argument, if an
/// instruction has one.
///
/// Every 4 aligned, consecutive bytes of application memory have one origin
/// value associated with them. If these bytes contain uninitialized data
/// coming from 2 different allocations, the last store wins. Because of this,
/// MemorySanitizer reports can show unrelated origins, but this is unlikely in
/// practice.
///
/// Origins are meaningless for fully initialized values, so MemorySanitizer
/// avoids storing origin to memory when a fully initialized value is stored.
/// This way it avoids needless overwritting origin of the 4-byte region on
/// a short (i.e. 1 byte) clean store, and it is also good for performance.
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "msan"
#include "llvm/Transforms/Instrumentation.h"
#include "llvm/ADT/DepthFirstIterator.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/ValueMap.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/InlineAsm.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/MDBuilder.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Type.h"
#include "llvm/InstVisitor.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/BlackList.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Transforms/Utils/ModuleUtils.h"
using namespace llvm;
static const uint64_t kShadowMask32 = 1ULL << 31;
static const uint64_t kShadowMask64 = 1ULL << 46;
static const uint64_t kOriginOffset32 = 1ULL << 30;
static const uint64_t kOriginOffset64 = 1ULL << 45;
static const unsigned kMinOriginAlignment = 4;
static const unsigned kShadowTLSAlignment = 8;
/// \brief Track origins of uninitialized values.
///
/// Adds a section to MemorySanitizer report that points to the allocation
/// (stack or heap) the uninitialized bits came from originally.
static cl::opt<bool> ClTrackOrigins("msan-track-origins",
cl::desc("Track origins (allocation sites) of poisoned memory"),
cl::Hidden, cl::init(false));
static cl::opt<bool> ClKeepGoing("msan-keep-going",
cl::desc("keep going after reporting a UMR"),
cl::Hidden, cl::init(false));
static cl::opt<bool> ClPoisonStack("msan-poison-stack",
cl::desc("poison uninitialized stack variables"),
cl::Hidden, cl::init(true));
static cl::opt<bool> ClPoisonStackWithCall("msan-poison-stack-with-call",
cl::desc("poison uninitialized stack variables with a call"),
cl::Hidden, cl::init(false));
static cl::opt<int> ClPoisonStackPattern("msan-poison-stack-pattern",
cl::desc("poison uninitialized stack variables with the given patter"),
cl::Hidden, cl::init(0xff));
static cl::opt<bool> ClHandleICmp("msan-handle-icmp",
cl::desc("propagate shadow through ICmpEQ and ICmpNE"),
cl::Hidden, cl::init(true));
static cl::opt<bool> ClHandleICmpExact("msan-handle-icmp-exact",
cl::desc("exact handling of relational integer ICmp"),
cl::Hidden, cl::init(false));
static cl::opt<bool> ClStoreCleanOrigin("msan-store-clean-origin",
cl::desc("store origin for clean (fully initialized) values"),
cl::Hidden, cl::init(false));
// This flag controls whether we check the shadow of the address
// operand of load or store. Such bugs are very rare, since load from
// a garbage address typically results in SEGV, but still happen
// (e.g. only lower bits of address are garbage, or the access happens
// early at program startup where malloc-ed memory is more likely to
// be zeroed. As of 2012-08-28 this flag adds 20% slowdown.
static cl::opt<bool> ClCheckAccessAddress("msan-check-access-address",
cl::desc("report accesses through a pointer which has poisoned shadow"),
cl::Hidden, cl::init(true));
static cl::opt<bool> ClDumpStrictInstructions("msan-dump-strict-instructions",
cl::desc("print out instructions with default strict semantics"),
cl::Hidden, cl::init(false));
static cl::opt<std::string> ClBlacklistFile("msan-blacklist",
cl::desc("File containing the list of functions where MemorySanitizer "
"should not report bugs"), cl::Hidden);
namespace {
/// \brief An instrumentation pass implementing detection of uninitialized
/// reads.
///
/// MemorySanitizer: instrument the code in module to find
/// uninitialized reads.
class MemorySanitizer : public FunctionPass {
public:
MemorySanitizer(bool TrackOrigins = false,
StringRef BlacklistFile = StringRef())
: FunctionPass(ID),
TrackOrigins(TrackOrigins || ClTrackOrigins),
TD(0),
WarningFn(0),
BlacklistFile(BlacklistFile.empty() ? ClBlacklistFile
: BlacklistFile) { }
const char *getPassName() const { return "MemorySanitizer"; }
bool runOnFunction(Function &F);
bool doInitialization(Module &M);
static char ID; // Pass identification, replacement for typeid.
private:
void initializeCallbacks(Module &M);
/// \brief Track origins (allocation points) of uninitialized values.
bool TrackOrigins;
DataLayout *TD;
LLVMContext *C;
Type *IntptrTy;
Type *OriginTy;
/// \brief Thread-local shadow storage for function parameters.
GlobalVariable *ParamTLS;
/// \brief Thread-local origin storage for function parameters.
GlobalVariable *ParamOriginTLS;
/// \brief Thread-local shadow storage for function return value.
GlobalVariable *RetvalTLS;
/// \brief Thread-local origin storage for function return value.
GlobalVariable *RetvalOriginTLS;
/// \brief Thread-local shadow storage for in-register va_arg function
/// parameters (x86_64-specific).
GlobalVariable *VAArgTLS;
/// \brief Thread-local shadow storage for va_arg overflow area
/// (x86_64-specific).
GlobalVariable *VAArgOverflowSizeTLS;
/// \brief Thread-local space used to pass origin value to the UMR reporting
/// function.
GlobalVariable *OriginTLS;
/// \brief The run-time callback to print a warning.
Value *WarningFn;
/// \brief Run-time helper that copies origin info for a memory range.
Value *MsanCopyOriginFn;
/// \brief Run-time helper that generates a new origin value for a stack
/// allocation.
Value *MsanSetAllocaOriginFn;
/// \brief Run-time helper that poisons stack on function entry.
Value *MsanPoisonStackFn;
/// \brief MSan runtime replacements for memmove, memcpy and memset.
Value *MemmoveFn, *MemcpyFn, *MemsetFn;
/// \brief Address mask used in application-to-shadow address calculation.
/// ShadowAddr is computed as ApplicationAddr & ~ShadowMask.
uint64_t ShadowMask;
/// \brief Offset of the origin shadow from the "normal" shadow.
/// OriginAddr is computed as (ShadowAddr + OriginOffset) & ~3ULL
uint64_t OriginOffset;
/// \brief Branch weights for error reporting.
MDNode *ColdCallWeights;
/// \brief Branch weights for origin store.
MDNode *OriginStoreWeights;
/// \bried Path to blacklist file.
SmallString<64> BlacklistFile;
/// \brief The blacklist.
OwningPtr<BlackList> BL;
/// \brief An empty volatile inline asm that prevents callback merge.
InlineAsm *EmptyAsm;
friend struct MemorySanitizerVisitor;
friend struct VarArgAMD64Helper;
};
} // namespace
char MemorySanitizer::ID = 0;
INITIALIZE_PASS(MemorySanitizer, "msan",
"MemorySanitizer: detects uninitialized reads.",
false, false)
FunctionPass *llvm::createMemorySanitizerPass(bool TrackOrigins,
StringRef BlacklistFile) {
return new MemorySanitizer(TrackOrigins, BlacklistFile);
}
/// \brief Create a non-const global initialized with the given string.
///
/// Creates a writable global for Str so that we can pass it to the
/// run-time lib. Runtime uses first 4 bytes of the string to store the
/// frame ID, so the string needs to be mutable.
static GlobalVariable *createPrivateNonConstGlobalForString(Module &M,
StringRef Str) {
Constant *StrConst = ConstantDataArray::getString(M.getContext(), Str);
return new GlobalVariable(M, StrConst->getType(), /*isConstant=*/false,
GlobalValue::PrivateLinkage, StrConst, "");
}
/// \brief Insert extern declaration of runtime-provided functions and globals.
void MemorySanitizer::initializeCallbacks(Module &M) {
// Only do this once.
if (WarningFn)
return;
IRBuilder<> IRB(*C);
// Create the callback.
// FIXME: this function should have "Cold" calling conv,
// which is not yet implemented.
StringRef WarningFnName = ClKeepGoing ? "__msan_warning"
: "__msan_warning_noreturn";
WarningFn = M.getOrInsertFunction(WarningFnName, IRB.getVoidTy(), NULL);
MsanCopyOriginFn = M.getOrInsertFunction(
"__msan_copy_origin", IRB.getVoidTy(), IRB.getInt8PtrTy(),
IRB.getInt8PtrTy(), IntptrTy, NULL);
MsanSetAllocaOriginFn = M.getOrInsertFunction(
"__msan_set_alloca_origin", IRB.getVoidTy(), IRB.getInt8PtrTy(), IntptrTy,
IRB.getInt8PtrTy(), NULL);
MsanPoisonStackFn = M.getOrInsertFunction(
"__msan_poison_stack", IRB.getVoidTy(), IRB.getInt8PtrTy(), IntptrTy, NULL);
MemmoveFn = M.getOrInsertFunction(
"__msan_memmove", IRB.getInt8PtrTy(), IRB.getInt8PtrTy(),
IRB.getInt8PtrTy(), IntptrTy, NULL);
MemcpyFn = M.getOrInsertFunction(
"__msan_memcpy", IRB.getInt8PtrTy(), IRB.getInt8PtrTy(), IRB.getInt8PtrTy(),
IntptrTy, NULL);
MemsetFn = M.getOrInsertFunction(
"__msan_memset", IRB.getInt8PtrTy(), IRB.getInt8PtrTy(), IRB.getInt32Ty(),
IntptrTy, NULL);
// Create globals.
RetvalTLS = new GlobalVariable(
M, ArrayType::get(IRB.getInt64Ty(), 8), false,
GlobalVariable::ExternalLinkage, 0, "__msan_retval_tls", 0,
GlobalVariable::GeneralDynamicTLSModel);
RetvalOriginTLS = new GlobalVariable(
M, OriginTy, false, GlobalVariable::ExternalLinkage, 0,
"__msan_retval_origin_tls", 0, GlobalVariable::GeneralDynamicTLSModel);
ParamTLS = new GlobalVariable(
M, ArrayType::get(IRB.getInt64Ty(), 1000), false,
GlobalVariable::ExternalLinkage, 0, "__msan_param_tls", 0,
GlobalVariable::GeneralDynamicTLSModel);
ParamOriginTLS = new GlobalVariable(
M, ArrayType::get(OriginTy, 1000), false, GlobalVariable::ExternalLinkage,
0, "__msan_param_origin_tls", 0, GlobalVariable::GeneralDynamicTLSModel);
VAArgTLS = new GlobalVariable(
M, ArrayType::get(IRB.getInt64Ty(), 1000), false,
GlobalVariable::ExternalLinkage, 0, "__msan_va_arg_tls", 0,
GlobalVariable::GeneralDynamicTLSModel);
VAArgOverflowSizeTLS = new GlobalVariable(
M, IRB.getInt64Ty(), false, GlobalVariable::ExternalLinkage, 0,
"__msan_va_arg_overflow_size_tls", 0,
GlobalVariable::GeneralDynamicTLSModel);
OriginTLS = new GlobalVariable(
M, IRB.getInt32Ty(), false, GlobalVariable::ExternalLinkage, 0,
"__msan_origin_tls", 0, GlobalVariable::GeneralDynamicTLSModel);
// We insert an empty inline asm after __msan_report* to avoid callback merge.
EmptyAsm = InlineAsm::get(FunctionType::get(IRB.getVoidTy(), false),
StringRef(""), StringRef(""),
/*hasSideEffects=*/true);
}
/// \brief Module-level initialization.
///
/// inserts a call to __msan_init to the module's constructor list.
bool MemorySanitizer::doInitialization(Module &M) {
TD = getAnalysisIfAvailable<DataLayout>();
if (!TD)
return false;
BL.reset(new BlackList(BlacklistFile));
C = &(M.getContext());
unsigned PtrSize = TD->getPointerSizeInBits(/* AddressSpace */0);
switch (PtrSize) {
case 64:
ShadowMask = kShadowMask64;
OriginOffset = kOriginOffset64;
break;
case 32:
ShadowMask = kShadowMask32;
OriginOffset = kOriginOffset32;
break;
default:
report_fatal_error("unsupported pointer size");
break;
}
IRBuilder<> IRB(*C);
IntptrTy = IRB.getIntPtrTy(TD);
OriginTy = IRB.getInt32Ty();
ColdCallWeights = MDBuilder(*C).createBranchWeights(1, 1000);
OriginStoreWeights = MDBuilder(*C).createBranchWeights(1, 1000);
// Insert a call to __msan_init/__msan_track_origins into the module's CTORs.
appendToGlobalCtors(M, cast<Function>(M.getOrInsertFunction(
"__msan_init", IRB.getVoidTy(), NULL)), 0);
new GlobalVariable(M, IRB.getInt32Ty(), true, GlobalValue::WeakODRLinkage,
IRB.getInt32(TrackOrigins), "__msan_track_origins");
new GlobalVariable(M, IRB.getInt32Ty(), true, GlobalValue::WeakODRLinkage,
IRB.getInt32(ClKeepGoing), "__msan_keep_going");
return true;
}
namespace {
/// \brief A helper class that handles instrumentation of VarArg
/// functions on a particular platform.
///
/// Implementations are expected to insert the instrumentation
/// necessary to propagate argument shadow through VarArg function
/// calls. Visit* methods are called during an InstVisitor pass over
/// the function, and should avoid creating new basic blocks. A new
/// instance of this class is created for each instrumented function.
struct VarArgHelper {
/// \brief Visit a CallSite.
virtual void visitCallSite(CallSite &CS, IRBuilder<> &IRB) = 0;
/// \brief Visit a va_start call.
virtual void visitVAStartInst(VAStartInst &I) = 0;
/// \brief Visit a va_copy call.
virtual void visitVACopyInst(VACopyInst &I) = 0;
/// \brief Finalize function instrumentation.
///
/// This method is called after visiting all interesting (see above)
/// instructions in a function.
virtual void finalizeInstrumentation() = 0;
virtual ~VarArgHelper() {}
};
struct MemorySanitizerVisitor;
VarArgHelper*
CreateVarArgHelper(Function &Func, MemorySanitizer &Msan,
MemorySanitizerVisitor &Visitor);
/// This class does all the work for a given function. Store and Load
/// instructions store and load corresponding shadow and origin
/// values. Most instructions propagate shadow from arguments to their
/// return values. Certain instructions (most importantly, BranchInst)
/// test their argument shadow and print reports (with a runtime call) if it's
/// non-zero.
struct MemorySanitizerVisitor : public InstVisitor<MemorySanitizerVisitor> {
Function &F;
MemorySanitizer &MS;
SmallVector<PHINode *, 16> ShadowPHINodes, OriginPHINodes;
ValueMap<Value*, Value*> ShadowMap, OriginMap;
bool InsertChecks;
bool LoadShadow;
OwningPtr<VarArgHelper> VAHelper;
struct ShadowOriginAndInsertPoint {
Instruction *Shadow;
Instruction *Origin;
Instruction *OrigIns;
ShadowOriginAndInsertPoint(Instruction *S, Instruction *O, Instruction *I)
: Shadow(S), Origin(O), OrigIns(I) { }
ShadowOriginAndInsertPoint() : Shadow(0), Origin(0), OrigIns(0) { }
};
SmallVector<ShadowOriginAndInsertPoint, 16> InstrumentationList;
SmallVector<Instruction*, 16> StoreList;
MemorySanitizerVisitor(Function &F, MemorySanitizer &MS)
: F(F), MS(MS), VAHelper(CreateVarArgHelper(F, MS, *this)) {
LoadShadow = InsertChecks =
!MS.BL->isIn(F) &&
F.getAttributes().hasAttribute(AttributeSet::FunctionIndex,
Attribute::SanitizeMemory);
DEBUG(if (!InsertChecks)
dbgs() << "MemorySanitizer is not inserting checks into '"
<< F.getName() << "'\n");
}
void materializeStores() {
for (size_t i = 0, n = StoreList.size(); i < n; i++) {
StoreInst& I = *dyn_cast<StoreInst>(StoreList[i]);
IRBuilder<> IRB(&I);
Value *Val = I.getValueOperand();
Value *Addr = I.getPointerOperand();
Value *Shadow = getShadow(Val);
Value *ShadowPtr = getShadowPtr(Addr, Shadow->getType(), IRB);
StoreInst *NewSI =
IRB.CreateAlignedStore(Shadow, ShadowPtr, I.getAlignment());
DEBUG(dbgs() << " STORE: " << *NewSI << "\n");
(void)NewSI;
if (ClCheckAccessAddress)
insertCheck(Addr, &I);
if (MS.TrackOrigins) {
unsigned Alignment = std::max(kMinOriginAlignment, I.getAlignment());
if (ClStoreCleanOrigin || isa<StructType>(Shadow->getType())) {
IRB.CreateAlignedStore(getOrigin(Val), getOriginPtr(Addr, IRB),
Alignment);
} else {
Value *ConvertedShadow = convertToShadowTyNoVec(Shadow, IRB);
Constant *Cst = dyn_cast_or_null<Constant>(ConvertedShadow);
// TODO(eugenis): handle non-zero constant shadow by inserting an
// unconditional check (can not simply fail compilation as this could
// be in the dead code).
if (Cst)
continue;
Value *Cmp = IRB.CreateICmpNE(ConvertedShadow,
getCleanShadow(ConvertedShadow), "_mscmp");
Instruction *CheckTerm =
SplitBlockAndInsertIfThen(cast<Instruction>(Cmp), false,
MS.OriginStoreWeights);
IRBuilder<> IRBNew(CheckTerm);
IRBNew.CreateAlignedStore(getOrigin(Val), getOriginPtr(Addr, IRBNew),
Alignment);
}
}
}
}
void materializeChecks() {
for (size_t i = 0, n = InstrumentationList.size(); i < n; i++) {
Instruction *Shadow = InstrumentationList[i].Shadow;
Instruction *OrigIns = InstrumentationList[i].OrigIns;
IRBuilder<> IRB(OrigIns);
DEBUG(dbgs() << " SHAD0 : " << *Shadow << "\n");
Value *ConvertedShadow = convertToShadowTyNoVec(Shadow, IRB);
DEBUG(dbgs() << " SHAD1 : " << *ConvertedShadow << "\n");
Value *Cmp = IRB.CreateICmpNE(ConvertedShadow,
getCleanShadow(ConvertedShadow), "_mscmp");
Instruction *CheckTerm =
SplitBlockAndInsertIfThen(cast<Instruction>(Cmp),
/* Unreachable */ !ClKeepGoing,
MS.ColdCallWeights);
IRB.SetInsertPoint(CheckTerm);
if (MS.TrackOrigins) {
Instruction *Origin = InstrumentationList[i].Origin;
IRB.CreateStore(Origin ? (Value*)Origin : (Value*)IRB.getInt32(0),
MS.OriginTLS);
}
CallInst *Call = IRB.CreateCall(MS.WarningFn);
Call->setDebugLoc(OrigIns->getDebugLoc());
IRB.CreateCall(MS.EmptyAsm);
DEBUG(dbgs() << " CHECK: " << *Cmp << "\n");
}
DEBUG(dbgs() << "DONE:\n" << F);
}
/// \brief Add MemorySanitizer instrumentation to a function.
bool runOnFunction() {
MS.initializeCallbacks(*F.getParent());
if (!MS.TD) return false;
// In the presence of unreachable blocks, we may see Phi nodes with
// incoming nodes from such blocks. Since InstVisitor skips unreachable
// blocks, such nodes will not have any shadow value associated with them.
// It's easier to remove unreachable blocks than deal with missing shadow.
removeUnreachableBlocks(F);
// Iterate all BBs in depth-first order and create shadow instructions
// for all instructions (where applicable).
// For PHI nodes we create dummy shadow PHIs which will be finalized later.
for (df_iterator<BasicBlock*> DI = df_begin(&F.getEntryBlock()),
DE = df_end(&F.getEntryBlock()); DI != DE; ++DI) {
BasicBlock *BB = *DI;
visit(*BB);
}
// Finalize PHI nodes.
for (size_t i = 0, n = ShadowPHINodes.size(); i < n; i++) {
PHINode *PN = ShadowPHINodes[i];
PHINode *PNS = cast<PHINode>(getShadow(PN));
PHINode *PNO = MS.TrackOrigins ? cast<PHINode>(getOrigin(PN)) : 0;
size_t NumValues = PN->getNumIncomingValues();
for (size_t v = 0; v < NumValues; v++) {
PNS->addIncoming(getShadow(PN, v), PN->getIncomingBlock(v));
if (PNO)
PNO->addIncoming(getOrigin(PN, v), PN->getIncomingBlock(v));
}
}
VAHelper->finalizeInstrumentation();
// Delayed instrumentation of StoreInst.
// This may add new checks to be inserted later.
materializeStores();
// Insert shadow value checks.
materializeChecks();
return true;
}
/// \brief Compute the shadow type that corresponds to a given Value.
Type *getShadowTy(Value *V) {
return getShadowTy(V->getType());
}
/// \brief Compute the shadow type that corresponds to a given Type.
Type *getShadowTy(Type *OrigTy) {
if (!OrigTy->isSized()) {
return 0;
}
// For integer type, shadow is the same as the original type.
// This may return weird-sized types like i1.
if (IntegerType *IT = dyn_cast<IntegerType>(OrigTy))
return IT;
if (VectorType *VT = dyn_cast<VectorType>(OrigTy)) {
uint32_t EltSize = MS.TD->getTypeSizeInBits(VT->getElementType());
return VectorType::get(IntegerType::get(*MS.C, EltSize),
VT->getNumElements());
}
if (StructType *ST = dyn_cast<StructType>(OrigTy)) {
SmallVector<Type*, 4> Elements;
for (unsigned i = 0, n = ST->getNumElements(); i < n; i++)
Elements.push_back(getShadowTy(ST->getElementType(i)));
StructType *Res = StructType::get(*MS.C, Elements, ST->isPacked());
DEBUG(dbgs() << "getShadowTy: " << *ST << " ===> " << *Res << "\n");
return Res;
}
uint32_t TypeSize = MS.TD->getTypeSizeInBits(OrigTy);
return IntegerType::get(*MS.C, TypeSize);
}
/// \brief Flatten a vector type.
Type *getShadowTyNoVec(Type *ty) {
if (VectorType *vt = dyn_cast<VectorType>(ty))
return IntegerType::get(*MS.C, vt->getBitWidth());
return ty;
}
/// \brief Convert a shadow value to it's flattened variant.
Value *convertToShadowTyNoVec(Value *V, IRBuilder<> &IRB) {
Type *Ty = V->getType();
Type *NoVecTy = getShadowTyNoVec(Ty);
if (Ty == NoVecTy) return V;
return IRB.CreateBitCast(V, NoVecTy);
}
/// \brief Compute the shadow address that corresponds to a given application
/// address.
///
/// Shadow = Addr & ~ShadowMask.
Value *getShadowPtr(Value *Addr, Type *ShadowTy,
IRBuilder<> &IRB) {
Value *ShadowLong =
IRB.CreateAnd(IRB.CreatePointerCast(Addr, MS.IntptrTy),
ConstantInt::get(MS.IntptrTy, ~MS.ShadowMask));
return IRB.CreateIntToPtr(ShadowLong, PointerType::get(ShadowTy, 0));
}
/// \brief Compute the origin address that corresponds to a given application
/// address.
///
/// OriginAddr = (ShadowAddr + OriginOffset) & ~3ULL
Value *getOriginPtr(Value *Addr, IRBuilder<> &IRB) {
Value *ShadowLong =
IRB.CreateAnd(IRB.CreatePointerCast(Addr, MS.IntptrTy),
ConstantInt::get(MS.IntptrTy, ~MS.ShadowMask));
Value *Add =
IRB.CreateAdd(ShadowLong,
ConstantInt::get(MS.IntptrTy, MS.OriginOffset));
Value *SecondAnd =
IRB.CreateAnd(Add, ConstantInt::get(MS.IntptrTy, ~3ULL));
return IRB.CreateIntToPtr(SecondAnd, PointerType::get(IRB.getInt32Ty(), 0));
}
/// \brief Compute the shadow address for a given function argument.
///
/// Shadow = ParamTLS+ArgOffset.
Value *getShadowPtrForArgument(Value *A, IRBuilder<> &IRB,
int ArgOffset) {
Value *Base = IRB.CreatePointerCast(MS.ParamTLS, MS.IntptrTy);
Base = IRB.CreateAdd(Base, ConstantInt::get(MS.IntptrTy, ArgOffset));
return IRB.CreateIntToPtr(Base, PointerType::get(getShadowTy(A), 0),
"_msarg");
}
/// \brief Compute the origin address for a given function argument.
Value *getOriginPtrForArgument(Value *A, IRBuilder<> &IRB,
int ArgOffset) {
if (!MS.TrackOrigins) return 0;
Value *Base = IRB.CreatePointerCast(MS.ParamOriginTLS, MS.IntptrTy);
Base = IRB.CreateAdd(Base, ConstantInt::get(MS.IntptrTy, ArgOffset));
return IRB.CreateIntToPtr(Base, PointerType::get(MS.OriginTy, 0),
"_msarg_o");
}
/// \brief Compute the shadow address for a retval.
Value *getShadowPtrForRetval(Value *A, IRBuilder<> &IRB) {
Value *Base = IRB.CreatePointerCast(MS.RetvalTLS, MS.IntptrTy);
return IRB.CreateIntToPtr(Base, PointerType::get(getShadowTy(A), 0),
"_msret");
}
/// \brief Compute the origin address for a retval.
Value *getOriginPtrForRetval(IRBuilder<> &IRB) {
// We keep a single origin for the entire retval. Might be too optimistic.
return MS.RetvalOriginTLS;
}
/// \brief Set SV to be the shadow value for V.
void setShadow(Value *V, Value *SV) {
assert(!ShadowMap.count(V) && "Values may only have one shadow");
ShadowMap[V] = SV;
}
/// \brief Set Origin to be the origin value for V.
void setOrigin(Value *V, Value *Origin) {
if (!MS.TrackOrigins) return;
assert(!OriginMap.count(V) && "Values may only have one origin");
DEBUG(dbgs() << "ORIGIN: " << *V << " ==> " << *Origin << "\n");
OriginMap[V] = Origin;
}
/// \brief Create a clean shadow value for a given value.
///
/// Clean shadow (all zeroes) means all bits of the value are defined
/// (initialized).
Value *getCleanShadow(Value *V) {
Type *ShadowTy = getShadowTy(V);
if (!ShadowTy)
return 0;
return Constant::getNullValue(ShadowTy);
}
/// \brief Create a dirty shadow of a given shadow type.
Constant *getPoisonedShadow(Type *ShadowTy) {
assert(ShadowTy);
if (isa<IntegerType>(ShadowTy) || isa<VectorType>(ShadowTy))
return Constant::getAllOnesValue(ShadowTy);
StructType *ST = cast<StructType>(ShadowTy);
SmallVector<Constant *, 4> Vals;
for (unsigned i = 0, n = ST->getNumElements(); i < n; i++)
Vals.push_back(getPoisonedShadow(ST->getElementType(i)));
return ConstantStruct::get(ST, Vals);
}
/// \brief Create a clean (zero) origin.
Value *getCleanOrigin() {
return Constant::getNullValue(MS.OriginTy);
}
/// \brief Get the shadow value for a given Value.
///
/// This function either returns the value set earlier with setShadow,
/// or extracts if from ParamTLS (for function arguments).
Value *getShadow(Value *V) {
if (Instruction *I = dyn_cast<Instruction>(V)) {
// For instructions the shadow is already stored in the map.
Value *Shadow = ShadowMap[V];
if (!Shadow) {
DEBUG(dbgs() << "No shadow: " << *V << "\n" << *(I->getParent()));
(void)I;
assert(Shadow && "No shadow for a value");
}
return Shadow;
}
if (UndefValue *U = dyn_cast<UndefValue>(V)) {
Value *AllOnes = getPoisonedShadow(getShadowTy(V));
DEBUG(dbgs() << "Undef: " << *U << " ==> " << *AllOnes << "\n");
(void)U;
return AllOnes;
}
if (Argument *A = dyn_cast<Argument>(V)) {
// For arguments we compute the shadow on demand and store it in the map.
Value **ShadowPtr = &ShadowMap[V];
if (*ShadowPtr)
return *ShadowPtr;
Function *F = A->getParent();
IRBuilder<> EntryIRB(F->getEntryBlock().getFirstNonPHI());
unsigned ArgOffset = 0;
for (Function::arg_iterator AI = F->arg_begin(), AE = F->arg_end();
AI != AE; ++AI) {
if (!AI->getType()->isSized()) {
DEBUG(dbgs() << "Arg is not sized\n");
continue;
}
unsigned Size = AI->hasByValAttr()
? MS.TD->getTypeAllocSize(AI->getType()->getPointerElementType())
: MS.TD->getTypeAllocSize(AI->getType());
if (A == AI) {
Value *Base = getShadowPtrForArgument(AI, EntryIRB, ArgOffset);
if (AI->hasByValAttr()) {
// ByVal pointer itself has clean shadow. We copy the actual
// argument shadow to the underlying memory.
Value *Cpy = EntryIRB.CreateMemCpy(
getShadowPtr(V, EntryIRB.getInt8Ty(), EntryIRB),
Base, Size, AI->getParamAlignment());
DEBUG(dbgs() << " ByValCpy: " << *Cpy << "\n");
(void)Cpy;
*ShadowPtr = getCleanShadow(V);
} else {
*ShadowPtr = EntryIRB.CreateLoad(Base);
}
DEBUG(dbgs() << " ARG: " << *AI << " ==> " <<
**ShadowPtr << "\n");
if (MS.TrackOrigins) {
Value* OriginPtr = getOriginPtrForArgument(AI, EntryIRB, ArgOffset);
setOrigin(A, EntryIRB.CreateLoad(OriginPtr));
}
}
ArgOffset += DataLayout::RoundUpAlignment(Size, 8);
}
assert(*ShadowPtr && "Could not find shadow for an argument");
return *ShadowPtr;
}
// For everything else the shadow is zero.
return getCleanShadow(V);
}
/// \brief Get the shadow for i-th argument of the instruction I.
Value *getShadow(Instruction *I, int i) {
return getShadow(I->getOperand(i));
}
/// \brief Get the origin for a value.
Value *getOrigin(Value *V) {
if (!MS.TrackOrigins) return 0;
if (isa<Instruction>(V) || isa<Argument>(V)) {
Value *Origin = OriginMap[V];
if (!Origin) {
DEBUG(dbgs() << "NO ORIGIN: " << *V << "\n");
Origin = getCleanOrigin();
}
return Origin;
}
return getCleanOrigin();
}
/// \brief Get the origin for i-th argument of the instruction I.
Value *getOrigin(Instruction *I, int i) {
return getOrigin(I->getOperand(i));
}
/// \brief Remember the place where a shadow check should be inserted.
///
/// This location will be later instrumented with a check that will print a
/// UMR warning in runtime if the value is not fully defined.
void insertCheck(Value *Val, Instruction *OrigIns) {
assert(Val);
if (!InsertChecks) return;
Instruction *Shadow = dyn_cast_or_null<Instruction>(getShadow(Val));
if (!Shadow) return;
#ifndef NDEBUG
Type *ShadowTy = Shadow->getType();
assert((isa<IntegerType>(ShadowTy) || isa<VectorType>(ShadowTy)) &&
"Can only insert checks for integer and vector shadow types");
#endif
Instruction *Origin = dyn_cast_or_null<Instruction>(getOrigin(Val));
InstrumentationList.push_back(
ShadowOriginAndInsertPoint(Shadow, Origin, OrigIns));
}
// ------------------- Visitors.
/// \brief Instrument LoadInst
///
/// Loads the corresponding shadow and (optionally) origin.
/// Optionally, checks that the load address is fully defined.
void visitLoadInst(LoadInst &I) {
assert(I.getType()->isSized() && "Load type must have size");
IRBuilder<> IRB(&I);
Type *ShadowTy = getShadowTy(&I);
Value *Addr = I.getPointerOperand();
if (LoadShadow) {
Value *ShadowPtr = getShadowPtr(Addr, ShadowTy, IRB);
setShadow(&I,
IRB.CreateAlignedLoad(ShadowPtr, I.getAlignment(), "_msld"));
} else {
setShadow(&I, getCleanShadow(&I));
}
if (ClCheckAccessAddress)
insertCheck(I.getPointerOperand(), &I);
if (MS.TrackOrigins) {
if (LoadShadow) {
unsigned Alignment = std::max(kMinOriginAlignment, I.getAlignment());
setOrigin(&I,
IRB.CreateAlignedLoad(getOriginPtr(Addr, IRB), Alignment));
} else {
setOrigin(&I, getCleanOrigin());
}
}
}
/// \brief Instrument StoreInst
///
/// Stores the corresponding shadow and (optionally) origin.
/// Optionally, checks that the store address is fully defined.
void visitStoreInst(StoreInst &I) {
StoreList.push_back(&I);
}
// Vector manipulation.
void visitExtractElementInst(ExtractElementInst &I) {
insertCheck(I.getOperand(1), &I);
IRBuilder<> IRB(&I);
setShadow(&I, IRB.CreateExtractElement(getShadow(&I, 0), I.getOperand(1),
"_msprop"));
setOrigin(&I, getOrigin(&I, 0));
}
void visitInsertElementInst(InsertElementInst &I) {
insertCheck(I.getOperand(2), &I);
IRBuilder<> IRB(&I);
setShadow(&I, IRB.CreateInsertElement(getShadow(&I, 0), getShadow(&I, 1),
I.getOperand(2), "_msprop"));
setOriginForNaryOp(I);
}
void visitShuffleVectorInst(ShuffleVectorInst &I) {
insertCheck(I.getOperand(2), &I);
IRBuilder<> IRB(&I);
setShadow(&I, IRB.CreateShuffleVector(getShadow(&I, 0), getShadow(&I, 1),
I.getOperand(2), "_msprop"));
setOriginForNaryOp(I);
}
// Casts.
void visitSExtInst(SExtInst &I) {
IRBuilder<> IRB(&I);
setShadow(&I, IRB.CreateSExt(getShadow(&I, 0), I.getType(), "_msprop"));
setOrigin(&I, getOrigin(&I, 0));
}
void visitZExtInst(ZExtInst &I) {
IRBuilder<> IRB(&I);
setShadow(&I, IRB.CreateZExt(getShadow(&I, 0), I.getType(), "_msprop"));
setOrigin(&I, getOrigin(&I, 0));
}
void visitTruncInst(TruncInst &I) {
IRBuilder<> IRB(&I);
setShadow(&I, IRB.CreateTrunc(getShadow(&I, 0), I.getType(), "_msprop"));
setOrigin(&I, getOrigin(&I, 0));
}
void visitBitCastInst(BitCastInst &I) {
IRBuilder<> IRB(&I);
setShadow(&I, IRB.CreateBitCast(getShadow(&I, 0), getShadowTy(&I)));
setOrigin(&I, getOrigin(&I, 0));
}
void visitPtrToIntInst(PtrToIntInst &I) {
IRBuilder<> IRB(&I);
setShadow(&I, IRB.CreateIntCast(getShadow(&I, 0), getShadowTy(&I), false,
"_msprop_ptrtoint"));
setOrigin(&I, getOrigin(&I, 0));
}
void visitIntToPtrInst(IntToPtrInst &I) {
IRBuilder<> IRB(&I);
setShadow(&I, IRB.CreateIntCast(getShadow(&I, 0), getShadowTy(&I), false,
"_msprop_inttoptr"));
setOrigin(&I, getOrigin(&I, 0));
}
void visitFPToSIInst(CastInst& I) { handleShadowOr(I); }
void visitFPToUIInst(CastInst& I) { handleShadowOr(I); }
void visitSIToFPInst(CastInst& I) { handleShadowOr(I); }
void visitUIToFPInst(CastInst& I) { handleShadowOr(I); }
void visitFPExtInst(CastInst& I) { handleShadowOr(I); }
void visitFPTruncInst(CastInst& I) { handleShadowOr(I); }
/// \brief Propagate shadow for bitwise AND.
///
/// This code is exact, i.e. if, for example, a bit in the left argument
/// is defined and 0, then neither the value not definedness of the
/// corresponding bit in B don't affect the resulting shadow.
void visitAnd(BinaryOperator &I) {
IRBuilder<> IRB(&I);
// "And" of 0 and a poisoned value results in unpoisoned value.
// 1&1 => 1; 0&1 => 0; p&1 => p;
// 1&0 => 0; 0&0 => 0; p&0 => 0;
// 1&p => p; 0&p => 0; p&p => p;
// S = (S1 & S2) | (V1 & S2) | (S1 & V2)
Value *S1 = getShadow(&I, 0);
Value *S2 = getShadow(&I, 1);
Value *V1 = I.getOperand(0);
Value *V2 = I.getOperand(1);
if (V1->getType() != S1->getType()) {
V1 = IRB.CreateIntCast(V1, S1->getType(), false);
V2 = IRB.CreateIntCast(V2, S2->getType(), false);
}
Value *S1S2 = IRB.CreateAnd(S1, S2);
Value *V1S2 = IRB.CreateAnd(V1, S2);
Value *S1V2 = IRB.CreateAnd(S1, V2);
setShadow(&I, IRB.CreateOr(S1S2, IRB.CreateOr(V1S2, S1V2)));
setOriginForNaryOp(I);
}
void visitOr(BinaryOperator &I) {
IRBuilder<> IRB(&I);
// "Or" of 1 and a poisoned value results in unpoisoned value.
// 1|1 => 1; 0|1 => 1; p|1 => 1;
// 1|0 => 1; 0|0 => 0; p|0 => p;
// 1|p => 1; 0|p => p; p|p => p;
// S = (S1 & S2) | (~V1 & S2) | (S1 & ~V2)
Value *S1 = getShadow(&I, 0);
Value *S2 = getShadow(&I, 1);
Value *V1 = IRB.CreateNot(I.getOperand(0));
Value *V2 = IRB.CreateNot(I.getOperand(1));
if (V1->getType() != S1->getType()) {
V1 = IRB.CreateIntCast(V1, S1->getType(), false);
V2 = IRB.CreateIntCast(V2, S2->getType(), false);
}
Value *S1S2 = IRB.CreateAnd(S1, S2);
Value *V1S2 = IRB.CreateAnd(V1, S2);
Value *S1V2 = IRB.CreateAnd(S1, V2);
setShadow(&I, IRB.CreateOr(S1S2, IRB.CreateOr(V1S2, S1V2)));
setOriginForNaryOp(I);
}
/// \brief Default propagation of shadow and/or origin.
///
/// This class implements the general case of shadow propagation, used in all
/// cases where we don't know and/or don't care about what the operation
/// actually does. It converts all input shadow values to a common type
/// (extending or truncating as necessary), and bitwise OR's them.
///
/// This is much cheaper than inserting checks (i.e. requiring inputs to be
/// fully initialized), and less prone to false positives.
///
/// This class also implements the general case of origin propagation. For a
/// Nary operation, result origin is set to the origin of an argument that is
/// not entirely initialized. If there is more than one such arguments, the
/// rightmost of them is picked. It does not matter which one is picked if all
/// arguments are initialized.
template <bool CombineShadow>
class Combiner {
Value *Shadow;
Value *Origin;
IRBuilder<> &IRB;
MemorySanitizerVisitor *MSV;
public:
Combiner(MemorySanitizerVisitor *MSV, IRBuilder<> &IRB) :
Shadow(0), Origin(0), IRB(IRB), MSV(MSV) {}
/// \brief Add a pair of shadow and origin values to the mix.
Combiner &Add(Value *OpShadow, Value *OpOrigin) {
if (CombineShadow) {
assert(OpShadow);
if (!Shadow)
Shadow = OpShadow;
else {
OpShadow = MSV->CreateShadowCast(IRB, OpShadow, Shadow->getType());
Shadow = IRB.CreateOr(Shadow, OpShadow, "_msprop");
}
}
if (MSV->MS.TrackOrigins) {
assert(OpOrigin);
if (!Origin) {
Origin = OpOrigin;
} else {
Value *FlatShadow = MSV->convertToShadowTyNoVec(OpShadow, IRB);
Value *Cond = IRB.CreateICmpNE(FlatShadow,
MSV->getCleanShadow(FlatShadow));
Origin = IRB.CreateSelect(Cond, OpOrigin, Origin);
}
}
return *this;
}
/// \brief Add an application value to the mix.
Combiner &Add(Value *V) {
Value *OpShadow = MSV->getShadow(V);
Value *OpOrigin = MSV->MS.TrackOrigins ? MSV->getOrigin(V) : 0;
return Add(OpShadow, OpOrigin);
}
/// \brief Set the current combined values as the given instruction's shadow
/// and origin.
void Done(Instruction *I) {
if (CombineShadow) {
assert(Shadow);
Shadow = MSV->CreateShadowCast(IRB, Shadow, MSV->getShadowTy(I));
MSV->setShadow(I, Shadow);
}
if (MSV->MS.TrackOrigins) {
assert(Origin);
MSV->setOrigin(I, Origin);
}
}
};
typedef Combiner<true> ShadowAndOriginCombiner;
typedef Combiner<false> OriginCombiner;
/// \brief Propagate origin for arbitrary operation.
void setOriginForNaryOp(Instruction &I) {
if (!MS.TrackOrigins) return;
IRBuilder<> IRB(&I);
OriginCombiner OC(this, IRB);
for (Instruction::op_iterator OI = I.op_begin(); OI != I.op_end(); ++OI)
OC.Add(OI->get());
OC.Done(&I);
}
size_t VectorOrPrimitiveTypeSizeInBits(Type *Ty) {
assert(!(Ty->isVectorTy() && Ty->getScalarType()->isPointerTy()) &&
"Vector of pointers is not a valid shadow type");
return Ty->isVectorTy() ?
Ty->getVectorNumElements() * Ty->getScalarSizeInBits() :
Ty->getPrimitiveSizeInBits();
}
/// \brief Cast between two shadow types, extending or truncating as
/// necessary.
Value *CreateShadowCast(IRBuilder<> &IRB, Value *V, Type *dstTy) {
Type *srcTy = V->getType();
if (dstTy->isIntegerTy() && srcTy->isIntegerTy())
return IRB.CreateIntCast(V, dstTy, false);
if (dstTy->isVectorTy() && srcTy->isVectorTy() &&
dstTy->getVectorNumElements() == srcTy->getVectorNumElements())
return IRB.CreateIntCast(V, dstTy, false);
size_t srcSizeInBits = VectorOrPrimitiveTypeSizeInBits(srcTy);
size_t dstSizeInBits = VectorOrPrimitiveTypeSizeInBits(dstTy);
Value *V1 = IRB.CreateBitCast(V, Type::getIntNTy(*MS.C, srcSizeInBits));
Value *V2 =
IRB.CreateIntCast(V1, Type::getIntNTy(*MS.C, dstSizeInBits), false);
return IRB.CreateBitCast(V2, dstTy);
// TODO: handle struct types.
}
/// \brief Propagate shadow for arbitrary operation.
void handleShadowOr(Instruction &I) {
IRBuilder<> IRB(&I);
ShadowAndOriginCombiner SC(this, IRB);
for (Instruction::op_iterator OI = I.op_begin(); OI != I.op_end(); ++OI)
SC.Add(OI->get());
SC.Done(&I);
}
void visitFAdd(BinaryOperator &I) { handleShadowOr(I); }
void visitFSub(BinaryOperator &I) { handleShadowOr(I); }
void visitFMul(BinaryOperator &I) { handleShadowOr(I); }
void visitAdd(BinaryOperator &I) { handleShadowOr(I); }
void visitSub(BinaryOperator &I) { handleShadowOr(I); }
void visitXor(BinaryOperator &I) { handleShadowOr(I); }
void visitMul(BinaryOperator &I) { handleShadowOr(I); }
void handleDiv(Instruction &I) {
IRBuilder<> IRB(&I);
// Strict on the second argument.
insertCheck(I.getOperand(1), &I);
setShadow(&I, getShadow(&I, 0));
setOrigin(&I, getOrigin(&I, 0));
}
void visitUDiv(BinaryOperator &I) { handleDiv(I); }
void visitSDiv(BinaryOperator &I) { handleDiv(I); }
void visitFDiv(BinaryOperator &I) { handleDiv(I); }
void visitURem(BinaryOperator &I) { handleDiv(I); }
void visitSRem(BinaryOperator &I) { handleDiv(I); }
void visitFRem(BinaryOperator &I) { handleDiv(I); }
/// \brief Instrument == and != comparisons.
///
/// Sometimes the comparison result is known even if some of the bits of the
/// arguments are not.
void handleEqualityComparison(ICmpInst &I) {
IRBuilder<> IRB(&I);
Value *A = I.getOperand(0);
Value *B = I.getOperand(1);
Value *Sa = getShadow(A);
Value *Sb = getShadow(B);
// Get rid of pointers and vectors of pointers.
// For ints (and vectors of ints), types of A and Sa match,
// and this is a no-op.
A = IRB.CreatePointerCast(A, Sa->getType());
B = IRB.CreatePointerCast(B, Sb->getType());
// A == B <==> (C = A^B) == 0
// A != B <==> (C = A^B) != 0
// Sc = Sa | Sb
Value *C = IRB.CreateXor(A, B);
Value *Sc = IRB.CreateOr(Sa, Sb);
// Now dealing with i = (C == 0) comparison (or C != 0, does not matter now)
// Result is defined if one of the following is true
// * there is a defined 1 bit in C
// * C is fully defined
// Si = !(C & ~Sc) && Sc
Value *Zero = Constant::getNullValue(Sc->getType());
Value *MinusOne = Constant::getAllOnesValue(Sc->getType());
Value *Si =
IRB.CreateAnd(IRB.CreateICmpNE(Sc, Zero),
IRB.CreateICmpEQ(
IRB.CreateAnd(IRB.CreateXor(Sc, MinusOne), C), Zero));
Si->setName("_msprop_icmp");
setShadow(&I, Si);
setOriginForNaryOp(I);
}
/// \brief Build the lowest possible value of V, taking into account V's
/// uninitialized bits.
Value *getLowestPossibleValue(IRBuilder<> &IRB, Value *A, Value *Sa,
bool isSigned) {
if (isSigned) {
// Split shadow into sign bit and other bits.
Value *SaOtherBits = IRB.CreateLShr(IRB.CreateShl(Sa, 1), 1);
Value *SaSignBit = IRB.CreateXor(Sa, SaOtherBits);
// Maximise the undefined shadow bit, minimize other undefined bits.
return
IRB.CreateOr(IRB.CreateAnd(A, IRB.CreateNot(SaOtherBits)), SaSignBit);
} else {
// Minimize undefined bits.
return IRB.CreateAnd(A, IRB.CreateNot(Sa));
}
}
/// \brief Build the highest possible value of V, taking into account V's
/// uninitialized bits.
Value *getHighestPossibleValue(IRBuilder<> &IRB, Value *A, Value *Sa,
bool isSigned) {
if (isSigned) {
// Split shadow into sign bit and other bits.
Value *SaOtherBits = IRB.CreateLShr(IRB.CreateShl(Sa, 1), 1);
Value *SaSignBit = IRB.CreateXor(Sa, SaOtherBits);
// Minimise the undefined shadow bit, maximise other undefined bits.
return
IRB.CreateOr(IRB.CreateAnd(A, IRB.CreateNot(SaSignBit)), SaOtherBits);
} else {
// Maximize undefined bits.
return IRB.CreateOr(A, Sa);
}
}
/// \brief Instrument relational comparisons.
///
/// This function does exact shadow propagation for all relational
/// comparisons of integers, pointers and vectors of those.
/// FIXME: output seems suboptimal when one of the operands is a constant
void handleRelationalComparisonExact(ICmpInst &I) {
IRBuilder<> IRB(&I);
Value *A = I.getOperand(0);
Value *B = I.getOperand(1);
Value *Sa = getShadow(A);
Value *Sb = getShadow(B);
// Get rid of pointers and vectors of pointers.
// For ints (and vectors of ints), types of A and Sa match,
// and this is a no-op.
A = IRB.CreatePointerCast(A, Sa->getType());
B = IRB.CreatePointerCast(B, Sb->getType());
// Let [a0, a1] be the interval of possible values of A, taking into account
// its undefined bits. Let [b0, b1] be the interval of possible values of B.
// Then (A cmp B) is defined iff (a0 cmp b1) == (a1 cmp b0).
bool IsSigned = I.isSigned();
Value *S1 = IRB.CreateICmp(I.getPredicate(),
getLowestPossibleValue(IRB, A, Sa, IsSigned),
getHighestPossibleValue(IRB, B, Sb, IsSigned));
Value *S2 = IRB.CreateICmp(I.getPredicate(),
getHighestPossibleValue(IRB, A, Sa, IsSigned),
getLowestPossibleValue(IRB, B, Sb, IsSigned));
Value *Si = IRB.CreateXor(S1, S2);
setShadow(&I, Si);
setOriginForNaryOp(I);
}
/// \brief Instrument signed relational comparisons.
///
/// Handle (x<0) and (x>=0) comparisons (essentially, sign bit tests) by
/// propagating the highest bit of the shadow. Everything else is delegated
/// to handleShadowOr().
void handleSignedRelationalComparison(ICmpInst &I) {
Constant *constOp0 = dyn_cast<Constant>(I.getOperand(0));
Constant *constOp1 = dyn_cast<Constant>(I.getOperand(1));
Value* op = NULL;
CmpInst::Predicate pre = I.getPredicate();
if (constOp0 && constOp0->isNullValue() &&
(pre == CmpInst::ICMP_SGT || pre == CmpInst::ICMP_SLE)) {
op = I.getOperand(1);
} else if (constOp1 && constOp1->isNullValue() &&
(pre == CmpInst::ICMP_SLT || pre == CmpInst::ICMP_SGE)) {
op = I.getOperand(0);
}
if (op) {
IRBuilder<> IRB(&I);
Value* Shadow =
IRB.CreateICmpSLT(getShadow(op), getCleanShadow(op), "_msprop_icmpslt");
setShadow(&I, Shadow);
setOrigin(&I, getOrigin(op));
} else {
handleShadowOr(I);
}
}
void visitICmpInst(ICmpInst &I) {
if (!ClHandleICmp) {
handleShadowOr(I);
return;
}
if (I.isEquality()) {
handleEqualityComparison(I);
return;
}
assert(I.isRelational());
if (ClHandleICmpExact) {
handleRelationalComparisonExact(I);
return;
}
if (I.isSigned()) {
handleSignedRelationalComparison(I);
return;
}
assert(I.isUnsigned());
if ((isa<Constant>(I.getOperand(0)) || isa<Constant>(I.getOperand(1)))) {
handleRelationalComparisonExact(I);
return;
}
handleShadowOr(I);
}
void visitFCmpInst(FCmpInst &I) {
handleShadowOr(I);
}
void handleShift(BinaryOperator &I) {
IRBuilder<> IRB(&I);
// If any of the S2 bits are poisoned, the whole thing is poisoned.
// Otherwise perform the same shift on S1.
Value *S1 = getShadow(&I, 0);
Value *S2 = getShadow(&I, 1);
Value *S2Conv = IRB.CreateSExt(IRB.CreateICmpNE(S2, getCleanShadow(S2)),
S2->getType());
Value *V2 = I.getOperand(1);
Value *Shift = IRB.CreateBinOp(I.getOpcode(), S1, V2);
setShadow(&I, IRB.CreateOr(Shift, S2Conv));
setOriginForNaryOp(I);
}
void visitShl(BinaryOperator &I) { handleShift(I); }
void visitAShr(BinaryOperator &I) { handleShift(I); }
void visitLShr(BinaryOperator &I) { handleShift(I); }
/// \brief Instrument llvm.memmove
///
/// At this point we don't know if llvm.memmove will be inlined or not.
/// If we don't instrument it and it gets inlined,
/// our interceptor will not kick in and we will lose the memmove.
/// If we instrument the call here, but it does not get inlined,
/// we will memove the shadow twice: which is bad in case
/// of overlapping regions. So, we simply lower the intrinsic to a call.
///
/// Similar situation exists for memcpy and memset.
void visitMemMoveInst(MemMoveInst &I) {
IRBuilder<> IRB(&I);
IRB.CreateCall3(
MS.MemmoveFn,
IRB.CreatePointerCast(I.getArgOperand(0), IRB.getInt8PtrTy()),
IRB.CreatePointerCast(I.getArgOperand(1), IRB.getInt8PtrTy()),
IRB.CreateIntCast(I.getArgOperand(2), MS.IntptrTy, false));
I.eraseFromParent();
}
// Similar to memmove: avoid copying shadow twice.
// This is somewhat unfortunate as it may slowdown small constant memcpys.
// FIXME: consider doing manual inline for small constant sizes and proper
// alignment.
void visitMemCpyInst(MemCpyInst &I) {
IRBuilder<> IRB(&I);
IRB.CreateCall3(
MS.MemcpyFn,
IRB.CreatePointerCast(I.getArgOperand(0), IRB.getInt8PtrTy()),
IRB.CreatePointerCast(I.getArgOperand(1), IRB.getInt8PtrTy()),
IRB.CreateIntCast(I.getArgOperand(2), MS.IntptrTy, false));
I.eraseFromParent();
}
// Same as memcpy.
void visitMemSetInst(MemSetInst &I) {
IRBuilder<> IRB(&I);
IRB.CreateCall3(
MS.MemsetFn,
IRB.CreatePointerCast(I.getArgOperand(0), IRB.getInt8PtrTy()),
IRB.CreateIntCast(I.getArgOperand(1), IRB.getInt32Ty(), false),
IRB.CreateIntCast(I.getArgOperand(2), MS.IntptrTy, false));
I.eraseFromParent();
}
void visitVAStartInst(VAStartInst &I) {
VAHelper->visitVAStartInst(I);
}
void visitVACopyInst(VACopyInst &I) {
VAHelper->visitVACopyInst(I);
}
enum IntrinsicKind {
IK_DoesNotAccessMemory,
IK_OnlyReadsMemory,
IK_WritesMemory
};
static IntrinsicKind getIntrinsicKind(Intrinsic::ID iid) {
const int DoesNotAccessMemory = IK_DoesNotAccessMemory;
const int OnlyReadsArgumentPointees = IK_OnlyReadsMemory;
const int OnlyReadsMemory = IK_OnlyReadsMemory;
const int OnlyAccessesArgumentPointees = IK_WritesMemory;
const int UnknownModRefBehavior = IK_WritesMemory;
#define GET_INTRINSIC_MODREF_BEHAVIOR
#define ModRefBehavior IntrinsicKind
#include "llvm/IR/Intrinsics.gen"
#undef ModRefBehavior
#undef GET_INTRINSIC_MODREF_BEHAVIOR
}
/// \brief Handle vector store-like intrinsics.
///
/// Instrument intrinsics that look like a simple SIMD store: writes memory,
/// has 1 pointer argument and 1 vector argument, returns void.
bool handleVectorStoreIntrinsic(IntrinsicInst &I) {
IRBuilder<> IRB(&I);
Value* Addr = I.getArgOperand(0);
Value *Shadow = getShadow(&I, 1);
Value *ShadowPtr = getShadowPtr(Addr, Shadow->getType(), IRB);
// We don't know the pointer alignment (could be unaligned SSE store!).
// Have to assume to worst case.
IRB.CreateAlignedStore(Shadow, ShadowPtr, 1);
if (ClCheckAccessAddress)
insertCheck(Addr, &I);
// FIXME: use ClStoreCleanOrigin
// FIXME: factor out common code from materializeStores
if (MS.TrackOrigins)
IRB.CreateStore(getOrigin(&I, 1), getOriginPtr(Addr, IRB));
return true;
}
/// \brief Handle vector load-like intrinsics.
///
/// Instrument intrinsics that look like a simple SIMD load: reads memory,
/// has 1 pointer argument, returns a vector.
bool handleVectorLoadIntrinsic(IntrinsicInst &I) {
IRBuilder<> IRB(&I);
Value *Addr = I.getArgOperand(0);
Type *ShadowTy = getShadowTy(&I);
if (LoadShadow) {
Value *ShadowPtr = getShadowPtr(Addr, ShadowTy, IRB);
// We don't know the pointer alignment (could be unaligned SSE load!).
// Have to assume to worst case.
setShadow(&I, IRB.CreateAlignedLoad(ShadowPtr, 1, "_msld"));
} else {
setShadow(&I, getCleanShadow(&I));
}
if (ClCheckAccessAddress)
insertCheck(Addr, &I);
if (MS.TrackOrigins) {
if (LoadShadow)
setOrigin(&I, IRB.CreateLoad(getOriginPtr(Addr, IRB)));
else
setOrigin(&I, getCleanOrigin());
}
return true;
}
/// \brief Handle (SIMD arithmetic)-like intrinsics.
///
/// Instrument intrinsics with any number of arguments of the same type,
/// equal to the return type. The type should be simple (no aggregates or
/// pointers; vectors are fine).
/// Caller guarantees that this intrinsic does not access memory.
bool maybeHandleSimpleNomemIntrinsic(IntrinsicInst &I) {
Type *RetTy = I.getType();
if (!(RetTy->isIntOrIntVectorTy() ||
RetTy->isFPOrFPVectorTy() ||
RetTy->isX86_MMXTy()))
return false;
unsigned NumArgOperands = I.getNumArgOperands();
for (unsigned i = 0; i < NumArgOperands; ++i) {
Type *Ty = I.getArgOperand(i)->getType();
if (Ty != RetTy)
return false;
}
IRBuilder<> IRB(&I);
ShadowAndOriginCombiner SC(this, IRB);
for (unsigned i = 0; i < NumArgOperands; ++i)
SC.Add(I.getArgOperand(i));
SC.Done(&I);
return true;
}
/// \brief Heuristically instrument unknown intrinsics.
///
/// The main purpose of this code is to do something reasonable with all
/// random intrinsics we might encounter, most importantly - SIMD intrinsics.
/// We recognize several classes of intrinsics by their argument types and
/// ModRefBehaviour and apply special intrumentation when we are reasonably
/// sure that we know what the intrinsic does.
///
/// We special-case intrinsics where this approach fails. See llvm.bswap
/// handling as an example of that.
bool handleUnknownIntrinsic(IntrinsicInst &I) {
unsigned NumArgOperands = I.getNumArgOperands();
if (NumArgOperands == 0)
return false;
Intrinsic::ID iid = I.getIntrinsicID();
IntrinsicKind IK = getIntrinsicKind(iid);
bool OnlyReadsMemory = IK == IK_OnlyReadsMemory;
bool WritesMemory = IK == IK_WritesMemory;
assert(!(OnlyReadsMemory && WritesMemory));
if (NumArgOperands == 2 &&
I.getArgOperand(0)->getType()->isPointerTy() &&
I.getArgOperand(1)->getType()->isVectorTy() &&
I.getType()->isVoidTy() &&
WritesMemory) {
// This looks like a vector store.
return handleVectorStoreIntrinsic(I);
}
if (NumArgOperands == 1 &&
I.getArgOperand(0)->getType()->isPointerTy() &&
I.getType()->isVectorTy() &&
OnlyReadsMemory) {
// This looks like a vector load.
return handleVectorLoadIntrinsic(I);
}
if (!OnlyReadsMemory && !WritesMemory)
if (maybeHandleSimpleNomemIntrinsic(I))
return true;
// FIXME: detect and handle SSE maskstore/maskload
return false;
}
void handleBswap(IntrinsicInst &I) {
IRBuilder<> IRB(&I);
Value *Op = I.getArgOperand(0);
Type *OpType = Op->getType();
Function *BswapFunc = Intrinsic::getDeclaration(
F.getParent(), Intrinsic::bswap, ArrayRef<Type*>(&OpType, 1));
setShadow(&I, IRB.CreateCall(BswapFunc, getShadow(Op)));
setOrigin(&I, getOrigin(Op));
}
void visitIntrinsicInst(IntrinsicInst &I) {
switch (I.getIntrinsicID()) {
case llvm::Intrinsic::bswap:
handleBswap(I);
break;
default:
if (!handleUnknownIntrinsic(I))
visitInstruction(I);
break;
}
}
void visitCallSite(CallSite CS) {
Instruction &I = *CS.getInstruction();
assert((CS.isCall() || CS.isInvoke()) && "Unknown type of CallSite");
if (CS.isCall()) {
CallInst *Call = cast<CallInst>(&I);
// For inline asm, do the usual thing: check argument shadow and mark all
// outputs as clean. Note that any side effects of the inline asm that are
// not immediately visible in its constraints are not handled.
if (Call->isInlineAsm()) {
visitInstruction(I);
return;
}
// Allow only tail calls with the same types, otherwise
// we may have a false positive: shadow for a non-void RetVal
// will get propagated to a void RetVal.
if (Call->isTailCall() && Call->getType() != Call->getParent()->getType())
Call->setTailCall(false);
assert(!isa<IntrinsicInst>(&I) && "intrinsics are handled elsewhere");
// We are going to insert code that relies on the fact that the callee
// will become a non-readonly function after it is instrumented by us. To
// prevent this code from being optimized out, mark that function
// non-readonly in advance.
if (Function *Func = Call->getCalledFunction()) {
// Clear out readonly/readnone attributes.
AttrBuilder B;
B.addAttribute(Attribute::ReadOnly)
.addAttribute(Attribute::ReadNone);
Func->removeAttributes(AttributeSet::FunctionIndex,
AttributeSet::get(Func->getContext(),
AttributeSet::FunctionIndex,
B));
}
}
IRBuilder<> IRB(&I);
unsigned ArgOffset = 0;
DEBUG(dbgs() << " CallSite: " << I << "\n");
for (CallSite::arg_iterator ArgIt = CS.arg_begin(), End = CS.arg_end();
ArgIt != End; ++ArgIt) {
Value *A = *ArgIt;
unsigned i = ArgIt - CS.arg_begin();
if (!A->getType()->isSized()) {
DEBUG(dbgs() << "Arg " << i << " is not sized: " << I << "\n");
continue;
}
unsigned Size = 0;
Value *Store = 0;
// Compute the Shadow for arg even if it is ByVal, because
// in that case getShadow() will copy the actual arg shadow to
// __msan_param_tls.
Value *ArgShadow = getShadow(A);
Value *ArgShadowBase = getShadowPtrForArgument(A, IRB, ArgOffset);
DEBUG(dbgs() << " Arg#" << i << ": " << *A <<
" Shadow: " << *ArgShadow << "\n");
if (CS.paramHasAttr(i + 1, Attribute::ByVal)) {
assert(A->getType()->isPointerTy() &&
"ByVal argument is not a pointer!");
Size = MS.TD->getTypeAllocSize(A->getType()->getPointerElementType());
unsigned Alignment = CS.getParamAlignment(i + 1);
Store = IRB.CreateMemCpy(ArgShadowBase,
getShadowPtr(A, Type::getInt8Ty(*MS.C), IRB),
Size, Alignment);
} else {
Size = MS.TD->getTypeAllocSize(A->getType());
Store = IRB.CreateAlignedStore(ArgShadow, ArgShadowBase,
kShadowTLSAlignment);
}
if (MS.TrackOrigins)
IRB.CreateStore(getOrigin(A),
getOriginPtrForArgument(A, IRB, ArgOffset));
(void)Store;
assert(Size != 0 && Store != 0);
DEBUG(dbgs() << " Param:" << *Store << "\n");
ArgOffset += DataLayout::RoundUpAlignment(Size, 8);
}
DEBUG(dbgs() << " done with call args\n");
FunctionType *FT =
cast<FunctionType>(CS.getCalledValue()->getType()-> getContainedType(0));
if (FT->isVarArg()) {
VAHelper->visitCallSite(CS, IRB);
}
// Now, get the shadow for the RetVal.
if (!I.getType()->isSized()) return;
IRBuilder<> IRBBefore(&I);
// Untill we have full dynamic coverage, make sure the retval shadow is 0.
Value *Base = getShadowPtrForRetval(&I, IRBBefore);
IRBBefore.CreateAlignedStore(getCleanShadow(&I), Base, kShadowTLSAlignment);
Instruction *NextInsn = 0;
if (CS.isCall()) {
NextInsn = I.getNextNode();
} else {
BasicBlock *NormalDest = cast<InvokeInst>(&I)->getNormalDest();
if (!NormalDest->getSinglePredecessor()) {
// FIXME: this case is tricky, so we are just conservative here.
// Perhaps we need to split the edge between this BB and NormalDest,
// but a naive attempt to use SplitEdge leads to a crash.
setShadow(&I, getCleanShadow(&I));
setOrigin(&I, getCleanOrigin());
return;
}
NextInsn = NormalDest->getFirstInsertionPt();
assert(NextInsn &&
"Could not find insertion point for retval shadow load");
}
IRBuilder<> IRBAfter(NextInsn);
Value *RetvalShadow =
IRBAfter.CreateAlignedLoad(getShadowPtrForRetval(&I, IRBAfter),
kShadowTLSAlignment, "_msret");
setShadow(&I, RetvalShadow);
if (MS.TrackOrigins)
setOrigin(&I, IRBAfter.CreateLoad(getOriginPtrForRetval(IRBAfter)));
}
void visitReturnInst(ReturnInst &I) {
IRBuilder<> IRB(&I);
if (Value *RetVal = I.getReturnValue()) {
// Set the shadow for the RetVal.
Value *Shadow = getShadow(RetVal);
Value *ShadowPtr = getShadowPtrForRetval(RetVal, IRB);
DEBUG(dbgs() << "Return: " << *Shadow << "\n" << *ShadowPtr << "\n");
IRB.CreateAlignedStore(Shadow, ShadowPtr, kShadowTLSAlignment);
if (MS.TrackOrigins)
IRB.CreateStore(getOrigin(RetVal), getOriginPtrForRetval(IRB));
}
}
void visitPHINode(PHINode &I) {
IRBuilder<> IRB(&I);
ShadowPHINodes.push_back(&I);
setShadow(&I, IRB.CreatePHI(getShadowTy(&I), I.getNumIncomingValues(),
"_msphi_s"));
if (MS.TrackOrigins)
setOrigin(&I, IRB.CreatePHI(MS.OriginTy, I.getNumIncomingValues(),
"_msphi_o"));
}
void visitAllocaInst(AllocaInst &I) {
setShadow(&I, getCleanShadow(&I));
if (!ClPoisonStack) return;
IRBuilder<> IRB(I.getNextNode());
uint64_t Size = MS.TD->getTypeAllocSize(I.getAllocatedType());
if (ClPoisonStackWithCall) {
IRB.CreateCall2(MS.MsanPoisonStackFn,
IRB.CreatePointerCast(&I, IRB.getInt8PtrTy()),
ConstantInt::get(MS.IntptrTy, Size));
} else {
Value *ShadowBase = getShadowPtr(&I, Type::getInt8PtrTy(*MS.C), IRB);
IRB.CreateMemSet(ShadowBase, IRB.getInt8(ClPoisonStackPattern),
Size, I.getAlignment());
}
if (MS.TrackOrigins) {
setOrigin(&I, getCleanOrigin());
SmallString<2048> StackDescriptionStorage;
raw_svector_ostream StackDescription(StackDescriptionStorage);
// We create a string with a description of the stack allocation and
// pass it into __msan_set_alloca_origin.
// It will be printed by the run-time if stack-originated UMR is found.
// The first 4 bytes of the string are set to '----' and will be replaced
// by __msan_va_arg_overflow_size_tls at the first call.
StackDescription << "----" << I.getName() << "@" << F.getName();
Value *Descr =
createPrivateNonConstGlobalForString(*F.getParent(),
StackDescription.str());
IRB.CreateCall3(MS.MsanSetAllocaOriginFn,
IRB.CreatePointerCast(&I, IRB.getInt8PtrTy()),
ConstantInt::get(MS.IntptrTy, Size),
IRB.CreatePointerCast(Descr, IRB.getInt8PtrTy()));
}
}
void visitSelectInst(SelectInst& I) {
IRBuilder<> IRB(&I);
setShadow(&I, IRB.CreateSelect(I.getCondition(),
getShadow(I.getTrueValue()), getShadow(I.getFalseValue()),
"_msprop"));
if (MS.TrackOrigins) {
// Origins are always i32, so any vector conditions must be flattened.
// FIXME: consider tracking vector origins for app vectors?
Value *Cond = I.getCondition();
if (Cond->getType()->isVectorTy()) {
Value *ConvertedShadow = convertToShadowTyNoVec(Cond, IRB);
Cond = IRB.CreateICmpNE(ConvertedShadow,
getCleanShadow(ConvertedShadow), "_mso_select");
}
setOrigin(&I, IRB.CreateSelect(Cond,
getOrigin(I.getTrueValue()), getOrigin(I.getFalseValue())));
}
}
void visitLandingPadInst(LandingPadInst &I) {
// Do nothing.
// See http://code.google.com/p/memory-sanitizer/issues/detail?id=1
setShadow(&I, getCleanShadow(&I));
setOrigin(&I, getCleanOrigin());
}
void visitGetElementPtrInst(GetElementPtrInst &I) {
handleShadowOr(I);
}
void visitExtractValueInst(ExtractValueInst &I) {
IRBuilder<> IRB(&I);
Value *Agg = I.getAggregateOperand();
DEBUG(dbgs() << "ExtractValue: " << I << "\n");
Value *AggShadow = getShadow(Agg);
DEBUG(dbgs() << " AggShadow: " << *AggShadow << "\n");
Value *ResShadow = IRB.CreateExtractValue(AggShadow, I.getIndices());
DEBUG(dbgs() << " ResShadow: " << *ResShadow << "\n");
setShadow(&I, ResShadow);
setOrigin(&I, getCleanOrigin());
}
void visitInsertValueInst(InsertValueInst &I) {
IRBuilder<> IRB(&I);
DEBUG(dbgs() << "InsertValue: " << I << "\n");
Value *AggShadow = getShadow(I.getAggregateOperand());
Value *InsShadow = getShadow(I.getInsertedValueOperand());
DEBUG(dbgs() << " AggShadow: " << *AggShadow << "\n");
DEBUG(dbgs() << " InsShadow: " << *InsShadow << "\n");
Value *Res = IRB.CreateInsertValue(AggShadow, InsShadow, I.getIndices());
DEBUG(dbgs() << " Res: " << *Res << "\n");
setShadow(&I, Res);
setOrigin(&I, getCleanOrigin());
}
void dumpInst(Instruction &I) {
if (CallInst *CI = dyn_cast<CallInst>(&I)) {
errs() << "ZZZ call " << CI->getCalledFunction()->getName() << "\n";
} else {
errs() << "ZZZ " << I.getOpcodeName() << "\n";
}
errs() << "QQQ " << I << "\n";
}
void visitResumeInst(ResumeInst &I) {
DEBUG(dbgs() << "Resume: " << I << "\n");
// Nothing to do here.
}
void visitInstruction(Instruction &I) {
// Everything else: stop propagating and check for poisoned shadow.
if (ClDumpStrictInstructions)
dumpInst(I);
DEBUG(dbgs() << "DEFAULT: " << I << "\n");
for (size_t i = 0, n = I.getNumOperands(); i < n; i++)
insertCheck(I.getOperand(i), &I);
setShadow(&I, getCleanShadow(&I));
setOrigin(&I, getCleanOrigin());
}
};
/// \brief AMD64-specific implementation of VarArgHelper.
struct VarArgAMD64Helper : public VarArgHelper {
// An unfortunate workaround for asymmetric lowering of va_arg stuff.
// See a comment in visitCallSite for more details.
static const unsigned AMD64GpEndOffset = 48; // AMD64 ABI Draft 0.99.6 p3.5.7
static const unsigned AMD64FpEndOffset = 176;
Function &F;
MemorySanitizer &MS;
MemorySanitizerVisitor &MSV;
Value *VAArgTLSCopy;
Value *VAArgOverflowSize;
SmallVector<CallInst*, 16> VAStartInstrumentationList;
VarArgAMD64Helper(Function &F, MemorySanitizer &MS,
MemorySanitizerVisitor &MSV)
: F(F), MS(MS), MSV(MSV), VAArgTLSCopy(0), VAArgOverflowSize(0) { }
enum ArgKind { AK_GeneralPurpose, AK_FloatingPoint, AK_Memory };
ArgKind classifyArgument(Value* arg) {
// A very rough approximation of X86_64 argument classification rules.
Type *T = arg->getType();
if (T->isFPOrFPVectorTy() || T->isX86_MMXTy())
return AK_FloatingPoint;
if (T->isIntegerTy() && T->getPrimitiveSizeInBits() <= 64)
return AK_GeneralPurpose;
if (T->isPointerTy())
return AK_GeneralPurpose;
return AK_Memory;
}
// For VarArg functions, store the argument shadow in an ABI-specific format
// that corresponds to va_list layout.
// We do this because Clang lowers va_arg in the frontend, and this pass
// only sees the low level code that deals with va_list internals.
// A much easier alternative (provided that Clang emits va_arg instructions)
// would have been to associate each live instance of va_list with a copy of
// MSanParamTLS, and extract shadow on va_arg() call in the argument list
// order.
void visitCallSite(CallSite &CS, IRBuilder<> &IRB) {
unsigned GpOffset = 0;
unsigned FpOffset = AMD64GpEndOffset;
unsigned OverflowOffset = AMD64FpEndOffset;
for (CallSite::arg_iterator ArgIt = CS.arg_begin(), End = CS.arg_end();
ArgIt != End; ++ArgIt) {
Value *A = *ArgIt;
ArgKind AK = classifyArgument(A);
if (AK == AK_GeneralPurpose && GpOffset >= AMD64GpEndOffset)
AK = AK_Memory;
if (AK == AK_FloatingPoint && FpOffset >= AMD64FpEndOffset)
AK = AK_Memory;
Value *Base;
switch (AK) {
case AK_GeneralPurpose:
Base = getShadowPtrForVAArgument(A, IRB, GpOffset);
GpOffset += 8;
break;
case AK_FloatingPoint:
Base = getShadowPtrForVAArgument(A, IRB, FpOffset);
FpOffset += 16;
break;
case AK_Memory:
uint64_t ArgSize = MS.TD->getTypeAllocSize(A->getType());
Base = getShadowPtrForVAArgument(A, IRB, OverflowOffset);
OverflowOffset += DataLayout::RoundUpAlignment(ArgSize, 8);
}
IRB.CreateAlignedStore(MSV.getShadow(A), Base, kShadowTLSAlignment);
}
Constant *OverflowSize =
ConstantInt::get(IRB.getInt64Ty(), OverflowOffset - AMD64FpEndOffset);
IRB.CreateStore(OverflowSize, MS.VAArgOverflowSizeTLS);
}
/// \brief Compute the shadow address for a given va_arg.
Value *getShadowPtrForVAArgument(Value *A, IRBuilder<> &IRB,
int ArgOffset) {
Value *Base = IRB.CreatePointerCast(MS.VAArgTLS, MS.IntptrTy);
Base = IRB.CreateAdd(Base, ConstantInt::get(MS.IntptrTy, ArgOffset));
return IRB.CreateIntToPtr(Base, PointerType::get(MSV.getShadowTy(A), 0),
"_msarg");
}
void visitVAStartInst(VAStartInst &I) {
IRBuilder<> IRB(&I);
VAStartInstrumentationList.push_back(&I);
Value *VAListTag = I.getArgOperand(0);
Value *ShadowPtr = MSV.getShadowPtr(VAListTag, IRB.getInt8Ty(), IRB);
// Unpoison the whole __va_list_tag.
// FIXME: magic ABI constants.
IRB.CreateMemSet(ShadowPtr, Constant::getNullValue(IRB.getInt8Ty()),
/* size */24, /* alignment */8, false);
}
void visitVACopyInst(VACopyInst &I) {
IRBuilder<> IRB(&I);
Value *VAListTag = I.getArgOperand(0);
Value *ShadowPtr = MSV.getShadowPtr(VAListTag, IRB.getInt8Ty(), IRB);
// Unpoison the whole __va_list_tag.
// FIXME: magic ABI constants.
IRB.CreateMemSet(ShadowPtr, Constant::getNullValue(IRB.getInt8Ty()),
/* size */24, /* alignment */8, false);
}
void finalizeInstrumentation() {
assert(!VAArgOverflowSize && !VAArgTLSCopy &&
"finalizeInstrumentation called twice");
if (!VAStartInstrumentationList.empty()) {
// If there is a va_start in this function, make a backup copy of
// va_arg_tls somewhere in the function entry block.
IRBuilder<> IRB(F.getEntryBlock().getFirstNonPHI());
VAArgOverflowSize = IRB.CreateLoad(MS.VAArgOverflowSizeTLS);
Value *CopySize =
IRB.CreateAdd(ConstantInt::get(MS.IntptrTy, AMD64FpEndOffset),
VAArgOverflowSize);
VAArgTLSCopy = IRB.CreateAlloca(Type::getInt8Ty(*MS.C), CopySize);
IRB.CreateMemCpy(VAArgTLSCopy, MS.VAArgTLS, CopySize, 8);
}
// Instrument va_start.
// Copy va_list shadow from the backup copy of the TLS contents.
for (size_t i = 0, n = VAStartInstrumentationList.size(); i < n; i++) {
CallInst *OrigInst = VAStartInstrumentationList[i];
IRBuilder<> IRB(OrigInst->getNextNode());
Value *VAListTag = OrigInst->getArgOperand(0);
Value *RegSaveAreaPtrPtr =
IRB.CreateIntToPtr(
IRB.CreateAdd(IRB.CreatePtrToInt(VAListTag, MS.IntptrTy),
ConstantInt::get(MS.IntptrTy, 16)),
Type::getInt64PtrTy(*MS.C));
Value *RegSaveAreaPtr = IRB.CreateLoad(RegSaveAreaPtrPtr);
Value *RegSaveAreaShadowPtr =
MSV.getShadowPtr(RegSaveAreaPtr, IRB.getInt8Ty(), IRB);
IRB.CreateMemCpy(RegSaveAreaShadowPtr, VAArgTLSCopy,
AMD64FpEndOffset, 16);
Value *OverflowArgAreaPtrPtr =
IRB.CreateIntToPtr(
IRB.CreateAdd(IRB.CreatePtrToInt(VAListTag, MS.IntptrTy),
ConstantInt::get(MS.IntptrTy, 8)),
Type::getInt64PtrTy(*MS.C));
Value *OverflowArgAreaPtr = IRB.CreateLoad(OverflowArgAreaPtrPtr);
Value *OverflowArgAreaShadowPtr =
MSV.getShadowPtr(OverflowArgAreaPtr, IRB.getInt8Ty(), IRB);
Value *SrcPtr =
getShadowPtrForVAArgument(VAArgTLSCopy, IRB, AMD64FpEndOffset);
IRB.CreateMemCpy(OverflowArgAreaShadowPtr, SrcPtr, VAArgOverflowSize, 16);
}
}
};
VarArgHelper* CreateVarArgHelper(Function &Func, MemorySanitizer &Msan,
MemorySanitizerVisitor &Visitor) {
return new VarArgAMD64Helper(Func, Msan, Visitor);
}
} // namespace
bool MemorySanitizer::runOnFunction(Function &F) {
MemorySanitizerVisitor Visitor(F, *this);
// Clear out readonly/readnone attributes.
AttrBuilder B;
B.addAttribute(Attribute::ReadOnly)
.addAttribute(Attribute::ReadNone);
F.removeAttributes(AttributeSet::FunctionIndex,
AttributeSet::get(F.getContext(),
AttributeSet::FunctionIndex, B));
return Visitor.runOnFunction();
}