X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FCodeGen%2FShadowStackGC.cpp;h=b412532e331037a16e2f8069cd948d2b2e8ffda4;hb=c5b19b21d84814d19692a6bbea11fbd135f4b094;hp=850c00542ce6ddd01ab66e5620533786d1cbece1;hpb=5a29c9eed157af51a8d338b5a225b146881819e8;p=oota-llvm.git diff --git a/lib/CodeGen/ShadowStackGC.cpp b/lib/CodeGen/ShadowStackGC.cpp index 850c00542ce..b412532e331 100644 --- a/lib/CodeGen/ShadowStackGC.cpp +++ b/lib/CodeGen/ShadowStackGC.cpp @@ -1,4 +1,4 @@ -//===-- ShadowStackCollector.cpp - GC support for uncooperative targets ---===// +//===-- ShadowStackGC.cpp - GC support for uncooperative targets ----------===// // // The LLVM Compiler Infrastructure // @@ -9,7 +9,7 @@ // // This file implements lowering for the llvm.gc* intrinsics for targets that do // not natively support them (which includes the C backend). Note that the code -// generated is not quite as efficient as collectors which generate stack maps +// generated is not quite as efficient as algorithms which generate stack maps // to identify roots. // // This pass implements the code transformation described in this paper: @@ -17,7 +17,7 @@ // Fergus Henderson, ISMM, 2002 // // In runtime/GC/SemiSpace.cpp is a prototype runtime which is compatible with -// this collector. +// ShadowStackGC. // // In order to support this particular transformation, all stack roots are // coallocated in the stack. This allows a fully target-independent stack map @@ -31,96 +31,98 @@ #include "llvm/CodeGen/GCStrategy.h" #include "llvm/IntrinsicInst.h" #include "llvm/Module.h" +#include "llvm/Support/Compiler.h" #include "llvm/Support/IRBuilder.h" using namespace llvm; namespace { - - class VISIBILITY_HIDDEN ShadowStackCollector : public Collector { + + class VISIBILITY_HIDDEN ShadowStackGC : public GCStrategy { /// RootChain - This is the global linked-list that contains the chain of GC /// roots. GlobalVariable *Head; - + /// StackEntryTy - Abstract type of a link in the shadow stack. - /// + /// const StructType *StackEntryTy; - + /// Roots - GC roots in the current function. Each is a pair of the /// intrinsic call and its corresponding alloca. std::vector > Roots; - + public: - ShadowStackCollector(); - + ShadowStackGC(); + bool initializeCustomLowering(Module &M); bool performCustomLowering(Function &F); - + private: bool IsNullValue(Value *V); Constant *GetFrameMap(Function &F); const Type* GetConcreteStackEntryType(Function &F); void CollectRoots(Function &F); - static GetElementPtrInst *CreateGEP(IRBuilder<> &B, Value *BasePtr, + static GetElementPtrInst *CreateGEP(LLVMContext &Context, + IRBuilder<> &B, Value *BasePtr, int Idx1, const char *Name); - static GetElementPtrInst *CreateGEP(IRBuilder<> &B, Value *BasePtr, + static GetElementPtrInst *CreateGEP(LLVMContext &Context, + IRBuilder<> &B, Value *BasePtr, int Idx1, int Idx2, const char *Name); }; } - -static CollectorRegistry::Add -Y("shadow-stack", - "Very portable collector for uncooperative code generators"); - + +static GCRegistry::Add +X("shadow-stack", "Very portable GC for uncooperative code generators"); + namespace { /// EscapeEnumerator - This is a little algorithm to find all escape points /// from a function so that "finally"-style code can be inserted. In addition /// to finding the existing return and unwind instructions, it also (if /// necessary) transforms any call instructions into invokes and sends them to /// a landing pad. - /// + /// /// It's wrapped up in a state machine using the same transform C# uses for /// 'yield return' enumerators, This transform allows it to be non-allocating. class VISIBILITY_HIDDEN EscapeEnumerator { Function &F; const char *CleanupBBName; - + // State. int State; Function::iterator StateBB, StateE; IRBuilder<> Builder; - + public: EscapeEnumerator(Function &F, const char *N = "cleanup") - : F(F), CleanupBBName(N), State(0) {} - + : F(F), CleanupBBName(N), State(0), Builder(F.getContext()) {} + IRBuilder<> *Next() { switch (State) { default: return 0; - + case 0: StateBB = F.begin(); StateE = F.end(); State = 1; - + case 1: // Find all 'return' and 'unwind' instructions. while (StateBB != StateE) { BasicBlock *CurBB = StateBB++; - + // Branches and invokes do not escape, only unwind and return do. TerminatorInst *TI = CurBB->getTerminator(); if (!isa(TI) && !isa(TI)) continue; - + Builder.SetInsertPoint(TI->getParent(), TI); return &Builder; } - + State = 2; - + // Find all 'call' instructions. SmallVector Calls; for (Function::iterator BB = F.begin(), @@ -131,67 +133,63 @@ namespace { if (!CI->getCalledFunction() || !CI->getCalledFunction()->getIntrinsicID()) Calls.push_back(CI); - + if (Calls.empty()) return 0; - + // Create a cleanup block. BasicBlock *CleanupBB = BasicBlock::Create(CleanupBBName, &F); UnwindInst *UI = new UnwindInst(CleanupBB); - + // Transform the 'call' instructions into 'invoke's branching to the // cleanup block. Go in reverse order to make prettier BB names. SmallVector Args; for (unsigned I = Calls.size(); I != 0; ) { CallInst *CI = cast(Calls[--I]); - + // Split the basic block containing the function call. BasicBlock *CallBB = CI->getParent(); BasicBlock *NewBB = CallBB->splitBasicBlock(CI, CallBB->getName() + ".cont"); - + // Remove the unconditional branch inserted at the end of CallBB. CallBB->getInstList().pop_back(); NewBB->getInstList().remove(CI); - + // Create a new invoke instruction. Args.clear(); Args.append(CI->op_begin() + 1, CI->op_end()); - + InvokeInst *II = InvokeInst::Create(CI->getOperand(0), NewBB, CleanupBB, Args.begin(), Args.end(), CI->getName(), CallBB); II->setCallingConv(CI->getCallingConv()); - II->setParamAttrs(CI->getParamAttrs()); + II->setAttributes(CI->getAttributes()); CI->replaceAllUsesWith(II); delete CI; } - + Builder.SetInsertPoint(UI->getParent(), UI); return &Builder; } } }; - } // ----------------------------------------------------------------------------- -Collector *llvm::createShadowStackCollector() { - return new ShadowStackCollector(); -} +void llvm::linkShadowStackGC() { } -ShadowStackCollector::ShadowStackCollector() : Head(0), StackEntryTy(0) { +ShadowStackGC::ShadowStackGC() : Head(0), StackEntryTy(0) { InitRoots = true; CustomRoots = true; } -Constant *ShadowStackCollector::GetFrameMap(Function &F) { +Constant *ShadowStackGC::GetFrameMap(Function &F) { // doInitialization creates the abstract type of this value. - Type *VoidPtr = PointerType::getUnqual(Type::Int8Ty); - + // Truncate the ShadowStackDescriptor if some metadata is null. unsigned NumMeta = 0; SmallVector Metadata; @@ -201,65 +199,64 @@ Constant *ShadowStackCollector::GetFrameMap(Function &F) { NumMeta = I + 1; Metadata.push_back(ConstantExpr::getBitCast(C, VoidPtr)); } - + Constant *BaseElts[] = { ConstantInt::get(Type::Int32Ty, Roots.size(), false), ConstantInt::get(Type::Int32Ty, NumMeta, false), }; - + Constant *DescriptorElts[] = { ConstantStruct::get(BaseElts, 2), ConstantArray::get(ArrayType::get(VoidPtr, NumMeta), Metadata.begin(), NumMeta) }; - + Constant *FrameMap = ConstantStruct::get(DescriptorElts, 2); - + std::string TypeName("gc_map."); TypeName += utostr(NumMeta); F.getParent()->addTypeName(TypeName, FrameMap->getType()); - + // FIXME: Is this actually dangerous as WritingAnLLVMPass.html claims? Seems // that, short of multithreaded LLVM, it should be safe; all that is // necessary is that a simple Module::iterator loop not be invalidated. // Appending to the GlobalVariable list is safe in that sense. - // + // // All of the output passes emit globals last. The ExecutionEngine // explicitly supports adding globals to the module after // initialization. - // + // // Still, if it isn't deemed acceptable, then this transformation needs // to be a ModulePass (which means it cannot be in the 'llc' pipeline // (which uses a FunctionPassManager (which segfaults (not asserts) if // provided a ModulePass))). - Constant *GV = new GlobalVariable(FrameMap->getType(), true, + Constant *GV = new GlobalVariable(*F.getParent(), FrameMap->getType(), true, GlobalVariable::InternalLinkage, - FrameMap, "__gc_" + F.getName(), - F.getParent()); - + FrameMap, "__gc_" + F.getName()); + Constant *GEPIndices[2] = { ConstantInt::get(Type::Int32Ty, 0), ConstantInt::get(Type::Int32Ty, 0) }; return ConstantExpr::getGetElementPtr(GV, GEPIndices, 2); } -const Type* ShadowStackCollector::GetConcreteStackEntryType(Function &F) { +const Type* ShadowStackGC::GetConcreteStackEntryType(Function &F) { // doInitialization creates the generic version of this type. std::vector EltTys; EltTys.push_back(StackEntryTy); for (size_t I = 0; I != Roots.size(); I++) EltTys.push_back(Roots[I].second->getAllocatedType()); Type *Ty = StructType::get(EltTys); - + std::string TypeName("gc_stackentry."); TypeName += F.getName(); F.getParent()->addTypeName(TypeName, Ty); - + return Ty; } /// doInitialization - If this module uses the GC intrinsics, find them now. If /// not, exit fast. -bool ShadowStackCollector::initializeCustomLowering(Module &M) { +bool ShadowStackGC::initializeCustomLowering(Module &M) { // struct FrameMap { // int32_t NumRoots; // Number of roots in stack frame. // int32_t NumMeta; // Number of metadata descriptors. May be < NumRoots. @@ -271,57 +268,57 @@ bool ShadowStackCollector::initializeCustomLowering(Module &M) { StructType *FrameMapTy = StructType::get(EltTys); M.addTypeName("gc_map", FrameMapTy); PointerType *FrameMapPtrTy = PointerType::getUnqual(FrameMapTy); - + // struct StackEntry { // ShadowStackEntry *Next; // Caller's stack entry. // FrameMap *Map; // Pointer to constant FrameMap. // void *Roots[]; // Stack roots (in-place array, so we pretend). // }; OpaqueType *RecursiveTy = OpaqueType::get(); - + EltTys.clear(); EltTys.push_back(PointerType::getUnqual(RecursiveTy)); EltTys.push_back(FrameMapPtrTy); PATypeHolder LinkTyH = StructType::get(EltTys); - + RecursiveTy->refineAbstractTypeTo(LinkTyH.get()); StackEntryTy = cast(LinkTyH.get()); const PointerType *StackEntryPtrTy = PointerType::getUnqual(StackEntryTy); M.addTypeName("gc_stackentry", LinkTyH.get()); // FIXME: Is this safe from // a FunctionPass? - + // Get the root chain if it already exists. Head = M.getGlobalVariable("llvm_gc_root_chain"); if (!Head) { // If the root chain does not exist, insert a new one with linkonce // linkage! - Head = new GlobalVariable(StackEntryPtrTy, false, - GlobalValue::LinkOnceLinkage, - Constant::getNullValue(StackEntryPtrTy), - "llvm_gc_root_chain", &M); + Head = new GlobalVariable(M, StackEntryPtrTy, false, + GlobalValue::LinkOnceAnyLinkage, + M.getContext().getNullValue(StackEntryPtrTy), + "llvm_gc_root_chain"); } else if (Head->hasExternalLinkage() && Head->isDeclaration()) { - Head->setInitializer(Constant::getNullValue(StackEntryPtrTy)); - Head->setLinkage(GlobalValue::LinkOnceLinkage); + Head->setInitializer(M.getContext().getNullValue(StackEntryPtrTy)); + Head->setLinkage(GlobalValue::LinkOnceAnyLinkage); } - + return true; } -bool ShadowStackCollector::IsNullValue(Value *V) { +bool ShadowStackGC::IsNullValue(Value *V) { if (Constant *C = dyn_cast(V)) return C->isNullValue(); return false; } -void ShadowStackCollector::CollectRoots(Function &F) { +void ShadowStackGC::CollectRoots(Function &F) { // FIXME: Account for original alignment. Could fragment the root array. // Approach 1: Null initialize empty slots at runtime. Yuck. // Approach 2: Emit a map of the array instead of just a count. - + assert(Roots.empty() && "Not cleaned up?"); - + SmallVector,16> MetaRoots; - + for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E;) if (IntrinsicInst *CI = dyn_cast(II++)) @@ -334,100 +331,106 @@ void ShadowStackCollector::CollectRoots(Function &F) { else MetaRoots.push_back(Pair); } - + // Number roots with metadata (usually empty) at the beginning, so that the // FrameMap::Meta array can be elided. Roots.insert(Roots.begin(), MetaRoots.begin(), MetaRoots.end()); } GetElementPtrInst * -ShadowStackCollector::CreateGEP(IRBuilder<> &B, Value *BasePtr, - int Idx, int Idx2, const char *Name) { +ShadowStackGC::CreateGEP(LLVMContext &Context, IRBuilder<> &B, Value *BasePtr, + int Idx, int Idx2, const char *Name) { Value *Indices[] = { ConstantInt::get(Type::Int32Ty, 0), ConstantInt::get(Type::Int32Ty, Idx), ConstantInt::get(Type::Int32Ty, Idx2) }; Value* Val = B.CreateGEP(BasePtr, Indices, Indices + 3, Name); - + assert(isa(Val) && "Unexpected folded constant"); - + return dyn_cast(Val); } GetElementPtrInst * -ShadowStackCollector::CreateGEP(IRBuilder<> &B, Value *BasePtr, - int Idx, const char *Name) { +ShadowStackGC::CreateGEP(LLVMContext &Context, IRBuilder<> &B, Value *BasePtr, + int Idx, const char *Name) { Value *Indices[] = { ConstantInt::get(Type::Int32Ty, 0), ConstantInt::get(Type::Int32Ty, Idx) }; Value *Val = B.CreateGEP(BasePtr, Indices, Indices + 2, Name); - + assert(isa(Val) && "Unexpected folded constant"); return dyn_cast(Val); } /// runOnFunction - Insert code to maintain the shadow stack. -bool ShadowStackCollector::performCustomLowering(Function &F) { +bool ShadowStackGC::performCustomLowering(Function &F) { + LLVMContext &Context = F.getContext(); + // Find calls to llvm.gcroot. CollectRoots(F); - + // If there are no roots in this function, then there is no need to add a // stack map entry for it. if (Roots.empty()) return false; - + // Build the constant map and figure the type of the shadow stack entry. Value *FrameMap = GetFrameMap(F); const Type *ConcreteStackEntryTy = GetConcreteStackEntryType(F); - + // Build the shadow stack entry at the very start of the function. BasicBlock::iterator IP = F.getEntryBlock().begin(); IRBuilder<> AtEntry(IP->getParent(), IP); - + Instruction *StackEntry = AtEntry.CreateAlloca(ConcreteStackEntryTy, 0, "gc_frame"); - + while (isa(IP)) ++IP; AtEntry.SetInsertPoint(IP->getParent(), IP); - + // Initialize the map pointer and load the current head of the shadow stack. Instruction *CurrentHead = AtEntry.CreateLoad(Head, "gc_currhead"); - Instruction *EntryMapPtr = CreateGEP(AtEntry, StackEntry,0,1,"gc_frame.map"); + Instruction *EntryMapPtr = CreateGEP(Context, AtEntry, StackEntry, + 0,1,"gc_frame.map"); AtEntry.CreateStore(FrameMap, EntryMapPtr); - + // After all the allocas... for (unsigned I = 0, E = Roots.size(); I != E; ++I) { // For each root, find the corresponding slot in the aggregate... - Value *SlotPtr = CreateGEP(AtEntry, StackEntry, 1 + I, "gc_root"); - + Value *SlotPtr = CreateGEP(Context, AtEntry, StackEntry, 1 + I, "gc_root"); + // And use it in lieu of the alloca. AllocaInst *OriginalAlloca = Roots[I].second; SlotPtr->takeName(OriginalAlloca); OriginalAlloca->replaceAllUsesWith(SlotPtr); } - - // Move past the original stores inserted by Collector::InitRoots. This isn't - // really necessary (the collector would never see the intermediate state), - // but it's nicer not to push the half-initialized entry onto the stack. + + // Move past the original stores inserted by GCStrategy::InitRoots. This isn't + // really necessary (the collector would never see the intermediate state at + // runtime), but it's nicer not to push the half-initialized entry onto the + // shadow stack. while (isa(IP)) ++IP; AtEntry.SetInsertPoint(IP->getParent(), IP); - + // Push the entry onto the shadow stack. - Instruction *EntryNextPtr = CreateGEP(AtEntry,StackEntry,0,0,"gc_frame.next"); - Instruction *NewHeadVal = CreateGEP(AtEntry,StackEntry, 0, "gc_newhead"); - AtEntry.CreateStore(CurrentHead, EntryNextPtr); - AtEntry.CreateStore(NewHeadVal, Head); - + Instruction *EntryNextPtr = CreateGEP(Context, AtEntry, + StackEntry,0,0,"gc_frame.next"); + Instruction *NewHeadVal = CreateGEP(Context, AtEntry, + StackEntry, 0, "gc_newhead"); + AtEntry.CreateStore(CurrentHead, EntryNextPtr); + AtEntry.CreateStore(NewHeadVal, Head); + // For each instruction that escapes... EscapeEnumerator EE(F, "gc_cleanup"); while (IRBuilder<> *AtExit = EE.Next()) { // Pop the entry from the shadow stack. Don't reuse CurrentHead from // AtEntry, since that would make the value live for the entire function. - Instruction *EntryNextPtr2 = CreateGEP(*AtExit, StackEntry, 0, 0, + Instruction *EntryNextPtr2 = CreateGEP(Context, *AtExit, StackEntry, 0, 0, "gc_frame.next"); Value *SavedHead = AtExit->CreateLoad(EntryNextPtr2, "gc_savedhead"); AtExit->CreateStore(SavedHead, Head); } - + // Delete the original allocas (which are no longer used) and the intrinsic // calls (which are no longer valid). Doing this last avoids invalidating // iterators. @@ -435,7 +438,7 @@ bool ShadowStackCollector::performCustomLowering(Function &F) { Roots[I].first->eraseFromParent(); Roots[I].second->eraseFromParent(); } - + Roots.clear(); return true; }