#define DEBUG_TYPE "stack-protector"
#include "llvm/CodeGen/Passes.h"
+#include "llvm/ADT/Triple.h"
+#include "llvm/Analysis/Dominators.h"
#include "llvm/Attributes.h"
#include "llvm/Constants.h"
+#include "llvm/DataLayout.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Function.h"
#include "llvm/Instructions.h"
#include "llvm/Module.h"
#include "llvm/Pass.h"
#include "llvm/Support/CommandLine.h"
-#include "llvm/Target/TargetData.h"
#include "llvm/Target/TargetLowering.h"
+#include "llvm/Target/TargetOptions.h"
using namespace llvm;
-// SSPBufferSize - The lower bound for a buffer to be considered for stack
-// smashing protection.
-static cl::opt<unsigned>
-SSPBufferSize("stack-protector-buffer-size", cl::init(8),
- cl::desc("Lower bound for a buffer to be considered for "
- "stack protection"));
-
namespace {
- class VISIBILITY_HIDDEN StackProtector : public FunctionPass {
+ class StackProtector : public FunctionPass {
/// TLI - Keep a pointer of a TargetLowering to consult for determining
/// target type sizes.
const TargetLowering *TLI;
Function *F;
Module *M;
+ DominatorTree *DT;
+
/// InsertStackProtectors - Insert code into the prologue and epilogue of
/// the function.
///
/// check fails.
BasicBlock *CreateFailBB();
+ /// ContainsProtectableArray - Check whether the type either is an array or
+ /// contains an array of sufficient size so that we need stack protectors
+ /// for it.
+ bool ContainsProtectableArray(Type *Ty, bool InStruct = false) const;
+
/// RequiresStackProtector - Check whether or not this function needs a
/// stack protector based upon the stack protector level.
bool RequiresStackProtector() const;
public:
static char ID; // Pass identification, replacement for typeid.
- StackProtector() : FunctionPass(&ID), TLI(0) {}
+ StackProtector() : FunctionPass(ID), TLI(0) {
+ initializeStackProtectorPass(*PassRegistry::getPassRegistry());
+ }
StackProtector(const TargetLowering *tli)
- : FunctionPass(&ID), TLI(tli) {}
+ : FunctionPass(ID), TLI(tli) {
+ initializeStackProtectorPass(*PassRegistry::getPassRegistry());
+ }
+
+ virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.addPreserved<DominatorTree>();
+ }
virtual bool runOnFunction(Function &Fn);
};
} // end anonymous namespace
char StackProtector::ID = 0;
-static RegisterPass<StackProtector>
-X("stack-protector", "Insert stack protectors");
+INITIALIZE_PASS(StackProtector, "stack-protector",
+ "Insert stack protectors", false, false)
FunctionPass *llvm::createStackProtectorPass(const TargetLowering *tli) {
return new StackProtector(tli);
bool StackProtector::runOnFunction(Function &Fn) {
F = &Fn;
M = F->getParent();
+ DT = getAnalysisIfAvailable<DominatorTree>();
if (!RequiresStackProtector()) return false;
-
+
return InsertStackProtectors();
}
+/// ContainsProtectableArray - Check whether the type either is an array or
+/// contains a char array of sufficient size so that we need stack protectors
+/// for it.
+bool StackProtector::ContainsProtectableArray(Type *Ty, bool InStruct) const {
+ if (!Ty) return false;
+ if (ArrayType *AT = dyn_cast<ArrayType>(Ty)) {
+ const TargetMachine &TM = TLI->getTargetMachine();
+ if (!AT->getElementType()->isIntegerTy(8)) {
+ Triple Trip(TM.getTargetTriple());
+
+ // If we're on a non-Darwin platform or we're inside of a structure, don't
+ // add stack protectors unless the array is a character array.
+ if (InStruct || !Trip.isOSDarwin())
+ return false;
+ }
+
+ // If an array has more than SSPBufferSize bytes of allocated space, then we
+ // emit stack protectors.
+ if (TM.Options.SSPBufferSize <= TLI->getDataLayout()->getTypeAllocSize(AT))
+ return true;
+ }
+
+ const StructType *ST = dyn_cast<StructType>(Ty);
+ if (!ST) return false;
+
+ for (StructType::element_iterator I = ST->element_begin(),
+ E = ST->element_end(); I != E; ++I)
+ if (ContainsProtectableArray(*I, true))
+ return true;
+
+ return false;
+}
+
/// RequiresStackProtector - Check whether or not this function needs a stack
/// protector based upon the stack protector level. The heuristic we use is to
/// add a guard variable to functions that call alloca, and functions with
/// buffers larger than SSPBufferSize bytes.
bool StackProtector::RequiresStackProtector() const {
- if (F->hasFnAttr(Attribute::StackProtectReq))
+ if (F->getAttributes().hasAttribute(AttributeSet::FunctionIndex,
+ Attribute::StackProtectReq))
return true;
- if (!F->hasFnAttr(Attribute::StackProtect))
+ if (!F->getAttributes().hasAttribute(AttributeSet::FunctionIndex,
+ Attribute::StackProtect))
return false;
- const TargetData *TD = TLI->getTargetData();
-
for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) {
BasicBlock *BB = I;
// protectors.
return true;
- if (const ArrayType *AT = dyn_cast<ArrayType>(AI->getAllocatedType()))
- // If an array has more than SSPBufferSize bytes of allocated space,
- // then we emit stack protectors.
- if (SSPBufferSize <= TD->getTypeAllocSize(AT))
- return true;
+ if (ContainsProtectableArray(AI->getAllocatedType()))
+ return true;
}
}
/// value. It calls __stack_chk_fail if they differ.
bool StackProtector::InsertStackProtectors() {
BasicBlock *FailBB = 0; // The basic block to jump to if check fails.
+ BasicBlock *FailBBDom = 0; // FailBB's dominator.
AllocaInst *AI = 0; // Place on stack that stores the stack guard.
- Constant *StackGuardVar = 0; // The stack guard variable.
+ Value *StackGuardVar = 0; // The stack guard variable.
for (Function::iterator I = F->begin(), E = F->end(); I != E; ) {
BasicBlock *BB = I++;
-
ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator());
if (!RI) continue;
// StackGuardSlot = alloca i8*
// StackGuard = load __stack_chk_guard
// call void @llvm.stackprotect.create(StackGuard, StackGuardSlot)
- //
- PointerType *PtrTy = PointerType::getUnqual(Type::Int8Ty);
- StackGuardVar = M->getOrInsertGlobal("__stack_chk_guard", PtrTy);
+ //
+ PointerType *PtrTy = Type::getInt8PtrTy(RI->getContext());
+ unsigned AddressSpace, Offset;
+ if (TLI->getStackCookieLocation(AddressSpace, Offset)) {
+ Constant *OffsetVal =
+ ConstantInt::get(Type::getInt32Ty(RI->getContext()), Offset);
+
+ StackGuardVar = ConstantExpr::getIntToPtr(OffsetVal,
+ PointerType::get(PtrTy, AddressSpace));
+ } else {
+ StackGuardVar = M->getOrInsertGlobal("__stack_chk_guard", PtrTy);
+ }
BasicBlock &Entry = F->getEntryBlock();
Instruction *InsPt = &Entry.front();
Value *Args[] = { LI, AI };
CallInst::
Create(Intrinsic::getDeclaration(M, Intrinsic::stackprotector),
- &Args[0], array_endof(Args), "", InsPt);
+ Args, "", InsPt);
// Create the basic block to jump to when the guard check fails.
FailBB = CreateFailBB();
// Split the basic block before the return instruction.
BasicBlock *NewBB = BB->splitBasicBlock(RI, "SP_return");
+ if (DT && DT->isReachableFromEntry(BB)) {
+ DT->addNewBlock(NewBB, BB);
+ FailBBDom = FailBBDom ? DT->findNearestCommonDominator(FailBBDom, BB) :BB;
+ }
+
// Remove default branch instruction to the new BB.
BB->getTerminator()->eraseFromParent();
// statements in the function.
if (!FailBB) return false;
+ if (DT && FailBBDom)
+ DT->addNewBlock(FailBB, FailBBDom);
+
return true;
}
/// CreateFailBB - Create a basic block to jump to when the stack protector
/// check fails.
BasicBlock *StackProtector::CreateFailBB() {
- BasicBlock *FailBB = BasicBlock::Create("CallStackCheckFailBlk", F);
+ BasicBlock *FailBB = BasicBlock::Create(F->getContext(),
+ "CallStackCheckFailBlk", F);
Constant *StackChkFail =
- M->getOrInsertFunction("__stack_chk_fail", Type::VoidTy, NULL);
+ M->getOrInsertFunction("__stack_chk_fail",
+ Type::getVoidTy(F->getContext()), NULL);
CallInst::Create(StackChkFail, "", FailBB);
- new UnreachableInst(FailBB);
+ new UnreachableInst(F->getContext(), FailBB);
return FailBB;
}
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