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diff --git a/contrib/llvm/lib/CodeGen/ShadowStackGCLowering.cpp b/contrib/llvm/lib/CodeGen/ShadowStackGCLowering.cpp
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-//===- ShadowStackGCLowering.cpp - Custom lowering for shadow-stack gc ----===//
-//
-// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-// See https://llvm.org/LICENSE.txt for license information.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-//
-//===----------------------------------------------------------------------===//
-//
-// This file contains the custom lowering code required by the shadow-stack GC
-// strategy.
-//
-// This pass implements the code transformation described in this paper:
-// "Accurate Garbage Collection in an Uncooperative Environment"
-// Fergus Henderson, ISMM, 2002
-//
-//===----------------------------------------------------------------------===//
-
-#include "llvm/ADT/SmallVector.h"
-#include "llvm/ADT/StringExtras.h"
-#include "llvm/CodeGen/Passes.h"
-#include "llvm/IR/BasicBlock.h"
-#include "llvm/IR/Constant.h"
-#include "llvm/IR/Constants.h"
-#include "llvm/IR/DerivedTypes.h"
-#include "llvm/IR/Function.h"
-#include "llvm/IR/GlobalValue.h"
-#include "llvm/IR/GlobalVariable.h"
-#include "llvm/IR/IRBuilder.h"
-#include "llvm/IR/Instructions.h"
-#include "llvm/IR/IntrinsicInst.h"
-#include "llvm/IR/Intrinsics.h"
-#include "llvm/IR/Module.h"
-#include "llvm/IR/Type.h"
-#include "llvm/IR/Value.h"
-#include "llvm/Pass.h"
-#include "llvm/Support/Casting.h"
-#include "llvm/Transforms/Utils/EscapeEnumerator.h"
-#include <cassert>
-#include <cstddef>
-#include <string>
-#include <utility>
-#include <vector>
-
-using namespace llvm;
-
-#define DEBUG_TYPE "shadow-stack-gc-lowering"
-
-namespace {
-
-class ShadowStackGCLowering : public FunctionPass {
- /// RootChain - This is the global linked-list that contains the chain of GC
- /// roots.
- GlobalVariable *Head = nullptr;
-
- /// StackEntryTy - Abstract type of a link in the shadow stack.
- StructType *StackEntryTy = nullptr;
- StructType *FrameMapTy = nullptr;
-
- /// Roots - GC roots in the current function. Each is a pair of the
- /// intrinsic call and its corresponding alloca.
- std::vector<std::pair<CallInst *, AllocaInst *>> Roots;
-
-public:
- static char ID;
-
- ShadowStackGCLowering();
-
- bool doInitialization(Module &M) override;
- bool runOnFunction(Function &F) override;
-
-private:
- bool IsNullValue(Value *V);
- Constant *GetFrameMap(Function &F);
- Type *GetConcreteStackEntryType(Function &F);
- void CollectRoots(Function &F);
-
- static GetElementPtrInst *CreateGEP(LLVMContext &Context, IRBuilder<> &B,
- Type *Ty, Value *BasePtr, int Idx1,
- const char *Name);
- static GetElementPtrInst *CreateGEP(LLVMContext &Context, IRBuilder<> &B,
- Type *Ty, Value *BasePtr, int Idx1, int Idx2,
- const char *Name);
-};
-
-} // end anonymous namespace
-
-char ShadowStackGCLowering::ID = 0;
-
-INITIALIZE_PASS_BEGIN(ShadowStackGCLowering, DEBUG_TYPE,
- "Shadow Stack GC Lowering", false, false)
-INITIALIZE_PASS_DEPENDENCY(GCModuleInfo)
-INITIALIZE_PASS_END(ShadowStackGCLowering, DEBUG_TYPE,
- "Shadow Stack GC Lowering", false, false)
-
-FunctionPass *llvm::createShadowStackGCLoweringPass() { return new ShadowStackGCLowering(); }
-
-ShadowStackGCLowering::ShadowStackGCLowering() : FunctionPass(ID) {
- initializeShadowStackGCLoweringPass(*PassRegistry::getPassRegistry());
-}
-
-Constant *ShadowStackGCLowering::GetFrameMap(Function &F) {
- // doInitialization creates the abstract type of this value.
- Type *VoidPtr = Type::getInt8PtrTy(F.getContext());
-
- // Truncate the ShadowStackDescriptor if some metadata is null.
- unsigned NumMeta = 0;
- SmallVector<Constant *, 16> Metadata;
- for (unsigned I = 0; I != Roots.size(); ++I) {
- Constant *C = cast<Constant>(Roots[I].first->getArgOperand(1));
- if (!C->isNullValue())
- NumMeta = I + 1;
- Metadata.push_back(ConstantExpr::getBitCast(C, VoidPtr));
- }
- Metadata.resize(NumMeta);
-
- Type *Int32Ty = Type::getInt32Ty(F.getContext());
-
- Constant *BaseElts[] = {
- ConstantInt::get(Int32Ty, Roots.size(), false),
- ConstantInt::get(Int32Ty, NumMeta, false),
- };
-
- Constant *DescriptorElts[] = {
- ConstantStruct::get(FrameMapTy, BaseElts),
- ConstantArray::get(ArrayType::get(VoidPtr, NumMeta), Metadata)};
-
- Type *EltTys[] = {DescriptorElts[0]->getType(), DescriptorElts[1]->getType()};
- StructType *STy = StructType::create(EltTys, "gc_map." + utostr(NumMeta));
-
- Constant *FrameMap = ConstantStruct::get(STy, DescriptorElts);
-
- // 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(*F.getParent(), FrameMap->getType(), true,
- GlobalVariable::InternalLinkage, FrameMap,
- "__gc_" + F.getName());
-
- Constant *GEPIndices[2] = {
- ConstantInt::get(Type::getInt32Ty(F.getContext()), 0),
- ConstantInt::get(Type::getInt32Ty(F.getContext()), 0)};
- return ConstantExpr::getGetElementPtr(FrameMap->getType(), GV, GEPIndices);
-}
-
-Type *ShadowStackGCLowering::GetConcreteStackEntryType(Function &F) {
- // doInitialization creates the generic version of this type.
- std::vector<Type *> EltTys;
- EltTys.push_back(StackEntryTy);
- for (size_t I = 0; I != Roots.size(); I++)
- EltTys.push_back(Roots[I].second->getAllocatedType());
-
- return StructType::create(EltTys, ("gc_stackentry." + F.getName()).str());
-}
-
-/// doInitialization - If this module uses the GC intrinsics, find them now. If
-/// not, exit fast.
-bool ShadowStackGCLowering::doInitialization(Module &M) {
- bool Active = false;
- for (Function &F : M) {
- if (F.hasGC() && F.getGC() == std::string("shadow-stack")) {
- Active = true;
- break;
- }
- }
- if (!Active)
- return false;
-
- // struct FrameMap {
- // int32_t NumRoots; // Number of roots in stack frame.
- // int32_t NumMeta; // Number of metadata descriptors. May be < NumRoots.
- // void *Meta[]; // May be absent for roots without metadata.
- // };
- std::vector<Type *> EltTys;
- // 32 bits is ok up to a 32GB stack frame. :)
- EltTys.push_back(Type::getInt32Ty(M.getContext()));
- // Specifies length of variable length array.
- EltTys.push_back(Type::getInt32Ty(M.getContext()));
- FrameMapTy = StructType::create(EltTys, "gc_map");
- 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).
- // };
-
- StackEntryTy = StructType::create(M.getContext(), "gc_stackentry");
-
- EltTys.clear();
- EltTys.push_back(PointerType::getUnqual(StackEntryTy));
- EltTys.push_back(FrameMapPtrTy);
- StackEntryTy->setBody(EltTys);
- PointerType *StackEntryPtrTy = PointerType::getUnqual(StackEntryTy);
-
- // 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(
- M, StackEntryPtrTy, false, GlobalValue::LinkOnceAnyLinkage,
- Constant::getNullValue(StackEntryPtrTy), "llvm_gc_root_chain");
- } else if (Head->hasExternalLinkage() && Head->isDeclaration()) {
- Head->setInitializer(Constant::getNullValue(StackEntryPtrTy));
- Head->setLinkage(GlobalValue::LinkOnceAnyLinkage);
- }
-
- return true;
-}
-
-bool ShadowStackGCLowering::IsNullValue(Value *V) {
- if (Constant *C = dyn_cast<Constant>(V))
- return C->isNullValue();
- return false;
-}
-
-void ShadowStackGCLowering::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<std::pair<CallInst *, AllocaInst *>, 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<IntrinsicInst>(II++))
- if (Function *F = CI->getCalledFunction())
- if (F->getIntrinsicID() == Intrinsic::gcroot) {
- std::pair<CallInst *, AllocaInst *> Pair = std::make_pair(
- CI,
- cast<AllocaInst>(CI->getArgOperand(0)->stripPointerCasts()));
- if (IsNullValue(CI->getArgOperand(1)))
- Roots.push_back(Pair);
- 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 *ShadowStackGCLowering::CreateGEP(LLVMContext &Context,
- IRBuilder<> &B, Type *Ty,
- Value *BasePtr, int Idx,
- int Idx2,
- const char *Name) {
- Value *Indices[] = {ConstantInt::get(Type::getInt32Ty(Context), 0),
- ConstantInt::get(Type::getInt32Ty(Context), Idx),
- ConstantInt::get(Type::getInt32Ty(Context), Idx2)};
- Value *Val = B.CreateGEP(Ty, BasePtr, Indices, Name);
-
- assert(isa<GetElementPtrInst>(Val) && "Unexpected folded constant");
-
- return dyn_cast<GetElementPtrInst>(Val);
-}
-
-GetElementPtrInst *ShadowStackGCLowering::CreateGEP(LLVMContext &Context,
- IRBuilder<> &B, Type *Ty, Value *BasePtr,
- int Idx, const char *Name) {
- Value *Indices[] = {ConstantInt::get(Type::getInt32Ty(Context), 0),
- ConstantInt::get(Type::getInt32Ty(Context), Idx)};
- Value *Val = B.CreateGEP(Ty, BasePtr, Indices, Name);
-
- assert(isa<GetElementPtrInst>(Val) && "Unexpected folded constant");
-
- return dyn_cast<GetElementPtrInst>(Val);
-}
-
-/// runOnFunction - Insert code to maintain the shadow stack.
-bool ShadowStackGCLowering::runOnFunction(Function &F) {
- // Quick exit for functions that do not use the shadow stack GC.
- if (!F.hasGC() ||
- F.getGC() != std::string("shadow-stack"))
- return false;
-
- 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);
- 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, nullptr, "gc_frame");
-
- while (isa<AllocaInst>(IP))
- ++IP;
- AtEntry.SetInsertPoint(IP->getParent(), IP);
-
- // Initialize the map pointer and load the current head of the shadow stack.
- Instruction *CurrentHead =
- AtEntry.CreateLoad(StackEntryTy->getPointerTo(), Head, "gc_currhead");
- Instruction *EntryMapPtr = CreateGEP(Context, AtEntry, ConcreteStackEntryTy,
- 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(Context, AtEntry, ConcreteStackEntryTy,
- 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 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<StoreInst>(IP))
- ++IP;
- AtEntry.SetInsertPoint(IP->getParent(), IP);
-
- // Push the entry onto the shadow stack.
- Instruction *EntryNextPtr = CreateGEP(Context, AtEntry, ConcreteStackEntryTy,
- StackEntry, 0, 0, "gc_frame.next");
- Instruction *NewHeadVal = CreateGEP(Context, AtEntry, ConcreteStackEntryTy,
- 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(Context, *AtExit, ConcreteStackEntryTy, StackEntry, 0, 0,
- "gc_frame.next");
- Value *SavedHead = AtExit->CreateLoad(StackEntryTy->getPointerTo(),
- 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.
- for (unsigned I = 0, E = Roots.size(); I != E; ++I) {
- Roots[I].first->eraseFromParent();
- Roots[I].second->eraseFromParent();
- }
-
- Roots.clear();
- return true;
-}
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