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-rw-r--r--llvm/lib/Transforms/Instrumentation/SafeStack.cpp149
1 files changed, 106 insertions, 43 deletions
diff --git a/llvm/lib/Transforms/Instrumentation/SafeStack.cpp b/llvm/lib/Transforms/Instrumentation/SafeStack.cpp
index f8c4058ae22..4441663fc6d 100644
--- a/llvm/lib/Transforms/Instrumentation/SafeStack.cpp
+++ b/llvm/lib/Transforms/Instrumentation/SafeStack.cpp
@@ -57,6 +57,7 @@ STATISTIC(NumUnsafeStackRestorePointsFunctions,
STATISTIC(NumAllocas, "Total number of allocas");
STATISTIC(NumUnsafeStaticAllocas, "Number of unsafe static allocas");
STATISTIC(NumUnsafeDynamicAllocas, "Number of unsafe dynamic allocas");
+STATISTIC(NumUnsafeByValArguments, "Number of unsafe byval arguments");
STATISTIC(NumUnsafeStackRestorePoints, "Number of setjmps and landingpads");
} // namespace llvm
@@ -68,14 +69,14 @@ namespace {
///
/// The implementation simply replaces all mentions of the alloca with zero.
class AllocaOffsetRewriter : public SCEVRewriteVisitor<AllocaOffsetRewriter> {
- const AllocaInst *AI;
+ const Value *AllocaPtr;
public:
- AllocaOffsetRewriter(ScalarEvolution &SE, const AllocaInst *AI)
- : SCEVRewriteVisitor(SE), AI(AI) {}
+ AllocaOffsetRewriter(ScalarEvolution &SE, const Value *AllocaPtr)
+ : SCEVRewriteVisitor(SE), AllocaPtr(AllocaPtr) {}
const SCEV *visitUnknown(const SCEVUnknown *Expr) {
- if (Expr->getValue() == AI)
+ if (Expr->getValue() == AllocaPtr)
return SE.getZero(Expr->getType());
return Expr;
}
@@ -115,6 +116,7 @@ class SafeStack : public FunctionPass {
/// given function and append them to the respective vectors.
void findInsts(Function &F, SmallVectorImpl<AllocaInst *> &StaticAllocas,
SmallVectorImpl<AllocaInst *> &DynamicAllocas,
+ SmallVectorImpl<Argument *> &ByValArguments,
SmallVectorImpl<ReturnInst *> &Returns,
SmallVectorImpl<Instruction *> &StackRestorePoints);
@@ -130,6 +132,7 @@ class SafeStack : public FunctionPass {
/// allocas are allocated.
Value *moveStaticAllocasToUnsafeStack(IRBuilder<> &IRB, Function &F,
ArrayRef<AllocaInst *> StaticAllocas,
+ ArrayRef<Argument *> ByValArguments,
ArrayRef<ReturnInst *> Returns);
/// \brief Generate code to restore the stack after all stack restore points
@@ -149,11 +152,12 @@ class SafeStack : public FunctionPass {
AllocaInst *DynamicTop,
ArrayRef<AllocaInst *> DynamicAllocas);
- bool IsSafeStackAlloca(const AllocaInst *AI);
+ bool IsSafeStackAlloca(const Value *AllocaPtr, uint64_t AllocaSize);
bool IsMemIntrinsicSafe(const MemIntrinsic *MI, const Use &U,
- const AllocaInst *AI);
- bool IsAccessSafe(Value *Addr, uint64_t Size, const AllocaInst *AI);
+ const Value *AllocaPtr, uint64_t AllocaSize);
+ bool IsAccessSafe(Value *Addr, uint64_t Size, const Value *AllocaPtr,
+ uint64_t AllocaSize);
public:
static char ID; // Pass identification, replacement for typeid.
@@ -192,20 +196,23 @@ uint64_t SafeStack::getStaticAllocaAllocationSize(const AllocaInst* AI) {
return Size;
}
-bool SafeStack::IsAccessSafe(Value *Addr, uint64_t Size, const AllocaInst *AI) {
- AllocaOffsetRewriter Rewriter(*SE, AI);
+bool SafeStack::IsAccessSafe(Value *Addr, uint64_t AccessSize,
+ const Value *AllocaPtr, uint64_t AllocaSize) {
+ AllocaOffsetRewriter Rewriter(*SE, AllocaPtr);
const SCEV *Expr = Rewriter.visit(SE->getSCEV(Addr));
uint64_t BitWidth = SE->getTypeSizeInBits(Expr->getType());
ConstantRange AccessStartRange = SE->getUnsignedRange(Expr);
ConstantRange SizeRange =
- ConstantRange(APInt(BitWidth, 0), APInt(BitWidth, Size));
+ ConstantRange(APInt(BitWidth, 0), APInt(BitWidth, AccessSize));
ConstantRange AccessRange = AccessStartRange.add(SizeRange);
- ConstantRange AllocaRange = ConstantRange(
- APInt(BitWidth, 0), APInt(BitWidth, getStaticAllocaAllocationSize(AI)));
+ ConstantRange AllocaRange =
+ ConstantRange(APInt(BitWidth, 0), APInt(BitWidth, AllocaSize));
bool Safe = AllocaRange.contains(AccessRange);
- DEBUG(dbgs() << "[SafeStack] Alloca " << *AI << "\n"
+ DEBUG(dbgs() << "[SafeStack] "
+ << (isa<AllocaInst>(AllocaPtr) ? "Alloca " : "ByValArgument ")
+ << *AllocaPtr << "\n"
<< " Access " << *Addr << "\n"
<< " SCEV " << *Expr
<< " U: " << SE->getUnsignedRange(Expr)
@@ -218,36 +225,38 @@ bool SafeStack::IsAccessSafe(Value *Addr, uint64_t Size, const AllocaInst *AI) {
}
bool SafeStack::IsMemIntrinsicSafe(const MemIntrinsic *MI, const Use &U,
- const AllocaInst *AI) {
+ const Value *AllocaPtr,
+ uint64_t AllocaSize) {
// All MemIntrinsics have destination address in Arg0 and size in Arg2.
if (MI->getRawDest() != U) return true;
const auto *Len = dyn_cast<ConstantInt>(MI->getLength());
// Non-constant size => unsafe. FIXME: try SCEV getRange.
if (!Len) return false;
- return IsAccessSafe(U, Len->getZExtValue(), AI);
+ return IsAccessSafe(U, Len->getZExtValue(), AllocaPtr, AllocaSize);
}
-/// Check whether a given alloca instruction (AI) should be put on the safe
+/// Check whether a given allocation must be put on the safe
/// stack or not. The function analyzes all uses of AI and checks whether it is
/// only accessed in a memory safe way (as decided statically).
-bool SafeStack::IsSafeStackAlloca(const AllocaInst *AI) {
+bool SafeStack::IsSafeStackAlloca(const Value *AllocaPtr, uint64_t AllocaSize) {
// Go through all uses of this alloca and check whether all accesses to the
// allocated object are statically known to be memory safe and, hence, the
// object can be placed on the safe stack.
SmallPtrSet<const Value *, 16> Visited;
- SmallVector<const Instruction *, 8> WorkList;
- WorkList.push_back(AI);
+ SmallVector<const Value *, 8> WorkList;
+ WorkList.push_back(AllocaPtr);
// A DFS search through all uses of the alloca in bitcasts/PHI/GEPs/etc.
while (!WorkList.empty()) {
- const Instruction *V = WorkList.pop_back_val();
+ const Value *V = WorkList.pop_back_val();
for (const Use &UI : V->uses()) {
auto I = cast<const Instruction>(UI.getUser());
assert(V == UI.get());
switch (I->getOpcode()) {
case Instruction::Load: {
- if (!IsAccessSafe(UI, DL->getTypeStoreSize(I->getType()), AI))
+ if (!IsAccessSafe(UI, DL->getTypeStoreSize(I->getType()), AllocaPtr,
+ AllocaSize))
return false;
break;
}
@@ -257,13 +266,13 @@ bool SafeStack::IsSafeStackAlloca(const AllocaInst *AI) {
case Instruction::Store: {
if (V == I->getOperand(0)) {
// Stored the pointer - conservatively assume it may be unsafe.
- DEBUG(dbgs() << "[SafeStack] Unsafe alloca: " << *AI
+ DEBUG(dbgs() << "[SafeStack] Unsafe alloca: " << *AllocaPtr
<< "\n store of address: " << *I << "\n");
return false;
}
- if (!IsAccessSafe(
- UI, DL->getTypeStoreSize(I->getOperand(0)->getType()), AI))
+ if (!IsAccessSafe(UI, DL->getTypeStoreSize(I->getOperand(0)->getType()),
+ AllocaPtr, AllocaSize))
return false;
break;
}
@@ -283,8 +292,8 @@ bool SafeStack::IsSafeStackAlloca(const AllocaInst *AI) {
}
if (const MemIntrinsic *MI = dyn_cast<MemIntrinsic>(I)) {
- if (!IsMemIntrinsicSafe(MI, UI, AI)) {
- DEBUG(dbgs() << "[SafeStack] Unsafe alloca: " << *AI
+ if (!IsMemIntrinsicSafe(MI, UI, AllocaPtr, AllocaSize)) {
+ DEBUG(dbgs() << "[SafeStack] Unsafe alloca: " << *AllocaPtr
<< "\n unsafe memintrinsic: " << *I
<< "\n");
return false;
@@ -302,9 +311,9 @@ bool SafeStack::IsSafeStackAlloca(const AllocaInst *AI) {
ImmutableCallSite::arg_iterator B = CS.arg_begin(), E = CS.arg_end();
for (ImmutableCallSite::arg_iterator A = B; A != E; ++A)
if (A->get() == V)
- if (!(CS.doesNotCapture(A - B) &&
- (CS.doesNotAccessMemory(A - B) || CS.doesNotAccessMemory()))) {
- DEBUG(dbgs() << "[SafeStack] Unsafe alloca: " << *AI
+ if (!(CS.doesNotCapture(A - B) && (CS.doesNotAccessMemory(A - B) ||
+ CS.doesNotAccessMemory()))) {
+ DEBUG(dbgs() << "[SafeStack] Unsafe alloca: " << *AllocaPtr
<< "\n unsafe call: " << *I << "\n");
return false;
}
@@ -355,13 +364,15 @@ Value *SafeStack::getOrCreateUnsafeStackPtr(IRBuilder<> &IRB, Function &F) {
void SafeStack::findInsts(Function &F,
SmallVectorImpl<AllocaInst *> &StaticAllocas,
SmallVectorImpl<AllocaInst *> &DynamicAllocas,
+ SmallVectorImpl<Argument *> &ByValArguments,
SmallVectorImpl<ReturnInst *> &Returns,
SmallVectorImpl<Instruction *> &StackRestorePoints) {
for (Instruction &I : instructions(&F)) {
if (auto AI = dyn_cast<AllocaInst>(&I)) {
++NumAllocas;
- if (IsSafeStackAlloca(AI))
+ uint64_t Size = getStaticAllocaAllocationSize(AI);
+ if (IsSafeStackAlloca(AI, Size))
continue;
if (AI->isStaticAlloca()) {
@@ -386,6 +397,17 @@ void SafeStack::findInsts(Function &F,
"gcroot intrinsic not compatible with safestack attribute");
}
}
+ for (Argument &Arg : F.args()) {
+ if (!Arg.hasByValAttr())
+ continue;
+ uint64_t Size =
+ DL->getTypeStoreSize(Arg.getType()->getPointerElementType());
+ if (IsSafeStackAlloca(&Arg, Size))
+ continue;
+
+ ++NumUnsafeByValArguments;
+ ByValArguments.push_back(&Arg);
+ }
}
AllocaInst *
@@ -420,7 +442,7 @@ SafeStack::createStackRestorePoints(IRBuilder<> &IRB, Function &F,
for (Instruction *I : StackRestorePoints) {
++NumUnsafeStackRestorePoints;
- IRB.SetInsertPoint(cast<Instruction>(I->getNextNode()));
+ IRB.SetInsertPoint(I->getNextNode());
Value *CurrentTop = DynamicTop ? IRB.CreateLoad(DynamicTop) : StaticTop;
IRB.CreateStore(CurrentTop, UnsafeStackPtr);
}
@@ -428,11 +450,10 @@ SafeStack::createStackRestorePoints(IRBuilder<> &IRB, Function &F,
return DynamicTop;
}
-Value *
-SafeStack::moveStaticAllocasToUnsafeStack(IRBuilder<> &IRB, Function &F,
- ArrayRef<AllocaInst *> StaticAllocas,
- ArrayRef<ReturnInst *> Returns) {
- if (StaticAllocas.empty())
+Value *SafeStack::moveStaticAllocasToUnsafeStack(
+ IRBuilder<> &IRB, Function &F, ArrayRef<AllocaInst *> StaticAllocas,
+ ArrayRef<Argument *> ByValArguments, ArrayRef<ReturnInst *> Returns) {
+ if (StaticAllocas.empty() && ByValArguments.empty())
return nullptr;
DIBuilder DIB(*F.getParent());
@@ -454,6 +475,13 @@ SafeStack::moveStaticAllocasToUnsafeStack(IRBuilder<> &IRB, Function &F,
// Compute maximum alignment among static objects on the unsafe stack.
unsigned MaxAlignment = 0;
+ for (Argument *Arg : ByValArguments) {
+ Type *Ty = Arg->getType()->getPointerElementType();
+ unsigned Align = std::max((unsigned)DL->getPrefTypeAlignment(Ty),
+ Arg->getParamAlignment());
+ if (Align > MaxAlignment)
+ MaxAlignment = Align;
+ }
for (AllocaInst *AI : StaticAllocas) {
Type *Ty = AI->getAllocatedType();
unsigned Align =
@@ -465,15 +493,46 @@ SafeStack::moveStaticAllocasToUnsafeStack(IRBuilder<> &IRB, Function &F,
if (MaxAlignment > StackAlignment) {
// Re-align the base pointer according to the max requested alignment.
assert(isPowerOf2_32(MaxAlignment));
- IRB.SetInsertPoint(cast<Instruction>(BasePointer->getNextNode()));
+ IRB.SetInsertPoint(BasePointer->getNextNode());
BasePointer = cast<Instruction>(IRB.CreateIntToPtr(
IRB.CreateAnd(IRB.CreatePtrToInt(BasePointer, IntPtrTy),
ConstantInt::get(IntPtrTy, ~uint64_t(MaxAlignment - 1))),
StackPtrTy));
}
- // Allocate space for every unsafe static AllocaInst on the unsafe stack.
int64_t StaticOffset = 0; // Current stack top.
+ IRB.SetInsertPoint(BasePointer->getNextNode());
+
+ for (Argument *Arg : ByValArguments) {
+ Type *Ty = Arg->getType()->getPointerElementType();
+
+ uint64_t Size = DL->getTypeStoreSize(Ty);
+ if (Size == 0)
+ Size = 1; // Don't create zero-sized stack objects.
+
+ // Ensure the object is properly aligned.
+ unsigned Align = std::max((unsigned)DL->getPrefTypeAlignment(Ty),
+ Arg->getParamAlignment());
+
+ // Add alignment.
+ // NOTE: we ensure that BasePointer itself is aligned to >= Align.
+ StaticOffset += Size;
+ StaticOffset = RoundUpToAlignment(StaticOffset, Align);
+
+ Value *Off = IRB.CreateGEP(BasePointer, // BasePointer is i8*
+ ConstantInt::get(Int32Ty, -StaticOffset));
+ Value *NewArg = IRB.CreateBitCast(Off, Arg->getType(),
+ Arg->getName() + ".unsafe-byval");
+
+ // Replace alloc with the new location.
+ replaceDbgDeclare(Arg, BasePointer, BasePointer->getNextNode(), DIB,
+ /*Deref=*/true, -StaticOffset);
+ Arg->replaceAllUsesWith(NewArg);
+ IRB.SetInsertPoint(cast<Instruction>(NewArg)->getNextNode());
+ IRB.CreateMemCpy(Off, Arg, Size, Arg->getParamAlignment());
+ }
+
+ // Allocate space for every unsafe static AllocaInst on the unsafe stack.
for (AllocaInst *AI : StaticAllocas) {
IRB.SetInsertPoint(AI);
@@ -509,7 +568,7 @@ SafeStack::moveStaticAllocasToUnsafeStack(IRBuilder<> &IRB, Function &F,
StaticOffset = RoundUpToAlignment(StaticOffset, StackAlignment);
// Update shadow stack pointer in the function epilogue.
- IRB.SetInsertPoint(cast<Instruction>(BasePointer->getNextNode()));
+ IRB.SetInsertPoint(BasePointer->getNextNode());
Value *StaticTop =
IRB.CreateGEP(BasePointer, ConstantInt::get(Int32Ty, -StaticOffset),
@@ -621,6 +680,7 @@ bool SafeStack::runOnFunction(Function &F) {
SmallVector<AllocaInst *, 16> StaticAllocas;
SmallVector<AllocaInst *, 4> DynamicAllocas;
+ SmallVector<Argument *, 4> ByValArguments;
SmallVector<ReturnInst *, 4> Returns;
// Collect all points where stack gets unwound and needs to be restored
@@ -632,13 +692,15 @@ bool SafeStack::runOnFunction(Function &F) {
// Find all static and dynamic alloca instructions that must be moved to the
// unsafe stack, all return instructions and stack restore points.
- findInsts(F, StaticAllocas, DynamicAllocas, Returns, StackRestorePoints);
+ findInsts(F, StaticAllocas, DynamicAllocas, ByValArguments, Returns,
+ StackRestorePoints);
if (StaticAllocas.empty() && DynamicAllocas.empty() &&
- StackRestorePoints.empty())
+ ByValArguments.empty() && StackRestorePoints.empty())
return false; // Nothing to do in this function.
- if (!StaticAllocas.empty() || !DynamicAllocas.empty())
+ if (!StaticAllocas.empty() || !DynamicAllocas.empty() ||
+ !ByValArguments.empty())
++NumUnsafeStackFunctions; // This function has the unsafe stack.
if (!StackRestorePoints.empty())
@@ -648,7 +710,8 @@ bool SafeStack::runOnFunction(Function &F) {
UnsafeStackPtr = getOrCreateUnsafeStackPtr(IRB, F);
// The top of the unsafe stack after all unsafe static allocas are allocated.
- Value *StaticTop = moveStaticAllocasToUnsafeStack(IRB, F, StaticAllocas, Returns);
+ Value *StaticTop = moveStaticAllocasToUnsafeStack(IRB, F, StaticAllocas,
+ ByValArguments, Returns);
// Safe stack object that stores the current unsafe stack top. It is updated
// as unsafe dynamic (non-constant-sized) allocas are allocated and freed.
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