[safestack] Fix handling of array allocas.
The current code does not take alloca array size into account and,
as a result, considers any access past the first array element to be
unsafe.
llvm-svn: 254350
diff --git a/llvm/lib/Transforms/Instrumentation/SafeStack.cpp b/llvm/lib/Transforms/Instrumentation/SafeStack.cpp
index 6071ca5..f8c4058 100644
--- a/llvm/lib/Transforms/Instrumentation/SafeStack.cpp
+++ b/llvm/lib/Transforms/Instrumentation/SafeStack.cpp
@@ -118,6 +118,10 @@
SmallVectorImpl<ReturnInst *> &Returns,
SmallVectorImpl<Instruction *> &StackRestorePoints);
+ /// \brief Calculate the allocation size of a given alloca. Returns 0 if the
+ /// size can not be statically determined.
+ uint64_t getStaticAllocaAllocationSize(const AllocaInst* AI);
+
/// \brief Allocate space for all static allocas in \p StaticAllocas,
/// replace allocas with pointers into the unsafe stack and generate code to
/// restore the stack pointer before all return instructions in \p Returns.
@@ -177,6 +181,17 @@
bool runOnFunction(Function &F) override;
}; // class SafeStack
+uint64_t SafeStack::getStaticAllocaAllocationSize(const AllocaInst* AI) {
+ uint64_t Size = DL->getTypeAllocSize(AI->getAllocatedType());
+ if (AI->isArrayAllocation()) {
+ auto C = dyn_cast<ConstantInt>(AI->getArraySize());
+ if (!C)
+ return 0;
+ Size *= C->getZExtValue();
+ }
+ return Size;
+}
+
bool SafeStack::IsAccessSafe(Value *Addr, uint64_t Size, const AllocaInst *AI) {
AllocaOffsetRewriter Rewriter(*SE, AI);
const SCEV *Expr = Rewriter.visit(SE->getSCEV(Addr));
@@ -187,8 +202,7 @@
ConstantRange(APInt(BitWidth, 0), APInt(BitWidth, Size));
ConstantRange AccessRange = AccessStartRange.add(SizeRange);
ConstantRange AllocaRange = ConstantRange(
- APInt(BitWidth, 0),
- APInt(BitWidth, DL->getTypeStoreSize(AI->getAllocatedType())));
+ APInt(BitWidth, 0), APInt(BitWidth, getStaticAllocaAllocationSize(AI)));
bool Safe = AllocaRange.contains(AccessRange);
DEBUG(dbgs() << "[SafeStack] Alloca " << *AI << "\n"
@@ -463,10 +477,8 @@
for (AllocaInst *AI : StaticAllocas) {
IRB.SetInsertPoint(AI);
- auto CArraySize = cast<ConstantInt>(AI->getArraySize());
Type *Ty = AI->getAllocatedType();
-
- uint64_t Size = DL->getTypeAllocSize(Ty) * CArraySize->getZExtValue();
+ uint64_t Size = getStaticAllocaAllocationSize(AI);
if (Size == 0)
Size = 1; // Don't create zero-sized stack objects.