X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FCodeGen%2FStackProtector.cpp;h=f0a44abaf5cda1b4d4267752a46fc73f18a2a492;hb=2b33f4cbad43dcaca944d02a6ea67991ff9db9cf;hp=12d56c44b2a301afc207883de387c4ce3188acae;hpb=4a3a8511827ecdee7e606bdd4dc3733dcac41064;p=oota-llvm.git diff --git a/lib/CodeGen/StackProtector.cpp b/lib/CodeGen/StackProtector.cpp index 12d56c44b2a..f0a44abaf5c 100644 --- a/lib/CodeGen/StackProtector.cpp +++ b/lib/CodeGen/StackProtector.cpp @@ -16,215 +16,245 @@ #define DEBUG_TYPE "stack-protector" #include "llvm/CodeGen/Passes.h" +#include "llvm/Analysis/Dominators.h" +#include "llvm/Attributes.h" #include "llvm/Constants.h" #include "llvm/DerivedTypes.h" #include "llvm/Function.h" #include "llvm/Instructions.h" +#include "llvm/Intrinsics.h" #include "llvm/Module.h" #include "llvm/Pass.h" -#include "llvm/ADT/APInt.h" #include "llvm/Support/CommandLine.h" #include "llvm/Target/TargetData.h" #include "llvm/Target/TargetLowering.h" using namespace llvm; -// Enable stack protectors. +// SSPBufferSize - The lower bound for a buffer to be considered for stack +// smashing protection. static cl::opt SSPBufferSize("stack-protector-buffer-size", cl::init(8), - cl::desc("The lower bound for a buffer to be considered for " - "stack smashing protection.")); + cl::desc("Lower bound for a buffer to be considered for " + "stack protection")); namespace { - class VISIBILITY_HIDDEN StackProtector : public FunctionPass { - /// Level - The level of stack protection. - SSP::StackProtectorLevel Level; - + class StackProtector : public FunctionPass { /// TLI - Keep a pointer of a TargetLowering to consult for determining /// target type sizes. const TargetLowering *TLI; - /// FailBB - Holds the basic block to jump to when the stack protector check - /// fails. - BasicBlock *FailBB; - - /// StackProtFrameSlot - The place on the stack that the stack protector - /// guard is kept. - AllocaInst *StackProtFrameSlot; - - /// StackGuardVar - The global variable for the stack guard. - Constant *StackGuardVar; - Function *F; Module *M; - /// InsertStackProtectorPrologue - Insert code into the entry block that - /// stores the __stack_chk_guard variable onto the stack. - void InsertStackProtectorPrologue(); + DominatorTree* DT; - /// InsertStackProtectorEpilogue - Insert code before the return - /// instructions checking the stack value that was stored in the - /// prologue. If it isn't the same as the original value, then call a - /// "failure" function. - void InsertStackProtectorEpilogue(); + /// InsertStackProtectors - Insert code into the prologue and epilogue of + /// the function. + /// + /// - The prologue code loads and stores the stack guard onto the stack. + /// - The epilogue checks the value stored in the prologue against the + /// original value. It calls __stack_chk_fail if they differ. + bool InsertStackProtectors(); /// CreateFailBB - Create a basic block to jump to when the stack protector /// check fails. - void CreateFailBB(); + BasicBlock *CreateFailBB(); /// 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), Level(SSP::OFF), TLI(0), FailBB(0) {} - StackProtector(SSP::StackProtectorLevel lvl, const TargetLowering *tli) - : FunctionPass(&ID), Level(lvl), TLI(tli), FailBB(0) {} + StackProtector() : FunctionPass(ID), TLI(0) { + initializeStackProtectorPass(*PassRegistry::getPassRegistry()); + } + StackProtector(const TargetLowering *tli) + : FunctionPass(ID), TLI(tli) { + initializeStackProtectorPass(*PassRegistry::getPassRegistry()); + } + + virtual void getAnalysisUsage(AnalysisUsage &AU) const { + AU.addPreserved(); + } virtual bool runOnFunction(Function &Fn); }; } // end anonymous namespace char StackProtector::ID = 0; -static RegisterPass -X("stack-protector", "Insert stack protectors"); +INITIALIZE_PASS(StackProtector, "stack-protector", + "Insert stack protectors", false, false) -FunctionPass *llvm::createStackProtectorPass(SSP::StackProtectorLevel lvl, - const TargetLowering *tli) { - return new StackProtector(lvl, tli); +FunctionPass *llvm::createStackProtectorPass(const TargetLowering *tli) { + return new StackProtector(tli); } bool StackProtector::runOnFunction(Function &Fn) { F = &Fn; M = F->getParent(); + DT = getAnalysisIfAvailable(); if (!RequiresStackProtector()) return false; - InsertStackProtectorPrologue(); - InsertStackProtectorEpilogue(); - - // Cleanup. - FailBB = 0; - StackProtFrameSlot = 0; - StackGuardVar = 0; - return true; + return InsertStackProtectors(); } -/// InsertStackProtectorPrologue - Insert code into the entry block that stores -/// the __stack_chk_guard variable onto the stack. -void StackProtector::InsertStackProtectorPrologue() { - BasicBlock &Entry = F->getEntryBlock(); - Instruction &InsertPt = Entry.front(); - const PointerType *GuardTy = PointerType::getUnqual(Type::Int8Ty); - - StackGuardVar = M->getOrInsertGlobal("__stack_chk_guard", GuardTy); - StackProtFrameSlot = new AllocaInst(GuardTy, "StackProt_Frame", &InsertPt); - LoadInst *LI = new LoadInst(StackGuardVar, "StackGuard", false, &InsertPt); - new StoreInst(LI, StackProtFrameSlot, false, &InsertPt); +/// 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)) + return true; + + if (!F->hasFnAttr(Attribute::StackProtect)) + return false; + + const TargetData *TD = TLI->getTargetData(); + + for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) { + BasicBlock *BB = I; + + for (BasicBlock::iterator + II = BB->begin(), IE = BB->end(); II != IE; ++II) + if (AllocaInst *AI = dyn_cast(II)) { + if (AI->isArrayAllocation()) + // This is a call to alloca with a variable size. Emit stack + // protectors. + return true; + + if (const ArrayType *AT = dyn_cast(AI->getAllocatedType())) { + // We apparently only care about character arrays. + if (!AT->getElementType()->isIntegerTy(8)) + continue; + + // If an array has more than SSPBufferSize bytes of allocated space, + // then we emit stack protectors. + if (SSPBufferSize <= TD->getTypeAllocSize(AT)) + return true; + } + } + } + + return false; } -/// InsertStackProtectorEpilogue - Insert code before the return instructions -/// checking the stack value that was stored in the prologue. If it isn't the -/// same as the original value, then call a "failure" function. -void StackProtector::InsertStackProtectorEpilogue() { - // Create the basic block to jump to when the guard check fails. - CreateFailBB(); - - Function::iterator I = F->begin(), E = F->end(); - std::vector ReturnBBs; - ReturnBBs.reserve(F->size()); - - for (; I != E; ++I) - if (isa(I->getTerminator())) - ReturnBBs.push_back(I); - - if (ReturnBBs.empty()) return; // Odd, but could happen. . . - - // Loop through the basic blocks that have return instructions. Convert this: - // - // return: - // ... - // ret ... - // - // into this: - // - // return: - // ... - // %1 = load __stack_chk_guard - // %2 = load - // %3 = cmp i1 %1, %2 - // br i1 %3, label %SPRet, label %CallStackCheckFailBlk - // - // SP_return: - // ret ... - // - // CallStackCheckFailBlk: - // call void @__stack_chk_fail() - // unreachable - // - for (std::vector::iterator - II = ReturnBBs.begin(), IE = ReturnBBs.end(); II != IE; ++II) { - BasicBlock *BB = *II; - ReturnInst *RI = cast(BB->getTerminator()); - Function::iterator InsPt = BB; ++InsPt; // Insertion point for new BB. +/// InsertStackProtectors - Insert code into the prologue and epilogue of the +/// function. +/// +/// - The prologue code loads and stores the stack guard onto the stack. +/// - The epilogue checks the value stored in the prologue against the original +/// 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. + 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(BB->getTerminator()); + if (!RI) continue; + + if (!FailBB) { + // Insert code into the entry block that stores the __stack_chk_guard + // variable onto the stack: + // + // entry: + // StackGuardSlot = alloca i8* + // StackGuard = load __stack_chk_guard + // call void @llvm.stackprotect.create(StackGuard, StackGuardSlot) + // + const 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(); + + AI = new AllocaInst(PtrTy, "StackGuardSlot", InsPt); + LoadInst *LI = new LoadInst(StackGuardVar, "StackGuard", false, InsPt); + + Value *Args[] = { LI, AI }; + CallInst:: + Create(Intrinsic::getDeclaration(M, Intrinsic::stackprotector), + &Args[0], array_endof(Args), "", InsPt); + + // Create the basic block to jump to when the guard check fails. + FailBB = CreateFailBB(); + } + + // For each block with a return instruction, convert this: + // + // return: + // ... + // ret ... + // + // into this: + // + // return: + // ... + // %1 = load __stack_chk_guard + // %2 = load StackGuardSlot + // %3 = cmp i1 %1, %2 + // br i1 %3, label %SP_return, label %CallStackCheckFailBlk + // + // SP_return: + // ret ... + // + // CallStackCheckFailBlk: + // call void @__stack_chk_fail() + // unreachable // 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(); + // Move the newly created basic block to the point right after the old basic - // block. - NewBB->removeFromParent(); - F->getBasicBlockList().insert(InsPt, NewBB); + // block so that it's in the "fall through" position. + NewBB->moveAfter(BB); // Generate the stack protector instructions in the old basic block. - LoadInst *LI2 = new LoadInst(StackGuardVar, "", false, BB); - LoadInst *LI1 = new LoadInst(StackProtFrameSlot, "", true, BB); - ICmpInst *Cmp = new ICmpInst(CmpInst::ICMP_EQ, LI1, LI2, "", BB); + LoadInst *LI1 = new LoadInst(StackGuardVar, "", false, BB); + LoadInst *LI2 = new LoadInst(AI, "", true, BB); + ICmpInst *Cmp = new ICmpInst(*BB, CmpInst::ICMP_EQ, LI1, LI2, ""); BranchInst::Create(NewBB, FailBB, Cmp, BB); } + + // Return if we didn't modify any basic blocks. I.e., there are no return + // 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. -void StackProtector::CreateFailBB() { - assert(!FailBB && "Failure basic block already created?!"); - FailBB = BasicBlock::Create("CallStackCheckFailBlk", F); - std::vector Params; +BasicBlock *StackProtector::CreateFailBB() { + 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); -} - -/// RequiresStackProtector - Check whether or not this function needs a stack -/// protector based upon the stack protector level. -bool StackProtector::RequiresStackProtector() const { - switch (Level) { - default: return false; - case SSP::ALL: return true; - case SSP::SOME: { - // If the size of the local variables allocated on the stack is greater than - // SSPBufferSize, then we require a stack protector. - uint64_t StackSize = 0; - const TargetData *TD = TLI->getTargetData(); - - for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) { - BasicBlock *BB = I; - - for (BasicBlock::iterator - II = BB->begin(), IE = BB->end(); II != IE; ++II) - if (AllocaInst *AI = dyn_cast(II)) { - if (ConstantInt *CI = dyn_cast(AI->getArraySize())) { - uint64_t Bytes = TD->getTypeSizeInBits(AI->getAllocatedType()) / 8; - const APInt &Size = CI->getValue(); - StackSize += Bytes * Size.getZExtValue(); - - if (SSPBufferSize <= StackSize) - return true; - } - } - } - - return false; - } - } + new UnreachableInst(F->getContext(), FailBB); + return FailBB; }