| //===------ BPFAbstractMemberAccess.cpp - Abstracting Member Accesses -----===// |
| // |
| // 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 pass abstracted struct/union member accesses in order to support |
| // compile-once run-everywhere (CO-RE). The CO-RE intends to compile the program |
| // which can run on different kernels. In particular, if bpf program tries to |
| // access a particular kernel data structure member, the details of the |
| // intermediate member access will be remembered so bpf loader can do |
| // necessary adjustment right before program loading. |
| // |
| // For example, |
| // |
| // struct s { |
| // int a; |
| // int b; |
| // }; |
| // struct t { |
| // struct s c; |
| // int d; |
| // }; |
| // struct t e; |
| // |
| // For the member access e.c.b, the compiler will generate code |
| // &e + 4 |
| // |
| // The compile-once run-everywhere instead generates the following code |
| // r = 4 |
| // &e + r |
| // The "4" in "r = 4" can be changed based on a particular kernel version. |
| // For example, on a particular kernel version, if struct s is changed to |
| // |
| // struct s { |
| // int new_field; |
| // int a; |
| // int b; |
| // } |
| // |
| // By repeating the member access on the host, the bpf loader can |
| // adjust "r = 4" as "r = 8". |
| // |
| // This feature relies on the following three intrinsic calls: |
| // addr = preserve_array_access_index(base, dimension, index) |
| // addr = preserve_union_access_index(base, di_index) |
| // !llvm.preserve.access.index <union_ditype> |
| // addr = preserve_struct_access_index(base, gep_index, di_index) |
| // !llvm.preserve.access.index <struct_ditype> |
| // |
| // Bitfield member access needs special attention. User cannot take the |
| // address of a bitfield acceess. To facilitate kernel verifier |
| // for easy bitfield code optimization, a new clang intrinsic is introduced: |
| // uint32_t __builtin_preserve_field_info(member_access, info_kind) |
| // In IR, a chain with two (or more) intrinsic calls will be generated: |
| // ... |
| // addr = preserve_struct_access_index(base, 1, 1) !struct s |
| // uint32_t result = bpf_preserve_field_info(addr, info_kind) |
| // |
| // Suppose the info_kind is FIELD_SIGNEDNESS, |
| // The above two IR intrinsics will be replaced with |
| // a relocatable insn: |
| // signness = /* signness of member_access */ |
| // and signness can be changed by bpf loader based on the |
| // types on the host. |
| // |
| // User can also test whether a field exists or not with |
| // uint32_t result = bpf_preserve_field_info(member_access, FIELD_EXISTENCE) |
| // The field will be always available (result = 1) during initial |
| // compilation, but bpf loader can patch with the correct value |
| // on the target host where the member_access may or may not be available |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "BPF.h" |
| #include "BPFCORE.h" |
| #include "BPFTargetMachine.h" |
| #include "llvm/IR/DebugInfoMetadata.h" |
| #include "llvm/IR/GlobalVariable.h" |
| #include "llvm/IR/Instruction.h" |
| #include "llvm/IR/Instructions.h" |
| #include "llvm/IR/Module.h" |
| #include "llvm/IR/Type.h" |
| #include "llvm/IR/User.h" |
| #include "llvm/IR/Value.h" |
| #include "llvm/Pass.h" |
| #include "llvm/Transforms/Utils/BasicBlockUtils.h" |
| #include <stack> |
| |
| #define DEBUG_TYPE "bpf-abstract-member-access" |
| |
| namespace llvm { |
| const std::string BPFCoreSharedInfo::AmaAttr = "btf_ama"; |
| } // namespace llvm |
| |
| using namespace llvm; |
| |
| namespace { |
| |
| class BPFAbstractMemberAccess final : public ModulePass { |
| StringRef getPassName() const override { |
| return "BPF Abstract Member Access"; |
| } |
| |
| bool runOnModule(Module &M) override; |
| |
| public: |
| static char ID; |
| TargetMachine *TM; |
| // Add optional BPFTargetMachine parameter so that BPF backend can add the phase |
| // with target machine to find out the endianness. The default constructor (without |
| // parameters) is used by the pass manager for managing purposes. |
| BPFAbstractMemberAccess(BPFTargetMachine *TM = nullptr) : ModulePass(ID), TM(TM) {} |
| |
| struct CallInfo { |
| uint32_t Kind; |
| uint32_t AccessIndex; |
| uint32_t RecordAlignment; |
| MDNode *Metadata; |
| Value *Base; |
| }; |
| typedef std::stack<std::pair<CallInst *, CallInfo>> CallInfoStack; |
| |
| private: |
| enum : uint32_t { |
| BPFPreserveArrayAI = 1, |
| BPFPreserveUnionAI = 2, |
| BPFPreserveStructAI = 3, |
| BPFPreserveFieldInfoAI = 4, |
| }; |
| |
| const DataLayout *DL = nullptr; |
| |
| std::map<std::string, GlobalVariable *> GEPGlobals; |
| // A map to link preserve_*_access_index instrinsic calls. |
| std::map<CallInst *, std::pair<CallInst *, CallInfo>> AIChain; |
| // A map to hold all the base preserve_*_access_index instrinsic calls. |
| // The base call is not an input of any other preserve_* |
| // intrinsics. |
| std::map<CallInst *, CallInfo> BaseAICalls; |
| |
| bool doTransformation(Module &M); |
| |
| void traceAICall(CallInst *Call, CallInfo &ParentInfo); |
| void traceBitCast(BitCastInst *BitCast, CallInst *Parent, |
| CallInfo &ParentInfo); |
| void traceGEP(GetElementPtrInst *GEP, CallInst *Parent, |
| CallInfo &ParentInfo); |
| void collectAICallChains(Module &M, Function &F); |
| |
| bool IsPreserveDIAccessIndexCall(const CallInst *Call, CallInfo &Cinfo); |
| bool IsValidAIChain(const MDNode *ParentMeta, uint32_t ParentAI, |
| const MDNode *ChildMeta); |
| bool removePreserveAccessIndexIntrinsic(Module &M); |
| void replaceWithGEP(std::vector<CallInst *> &CallList, |
| uint32_t NumOfZerosIndex, uint32_t DIIndex); |
| bool HasPreserveFieldInfoCall(CallInfoStack &CallStack); |
| void GetStorageBitRange(DIDerivedType *MemberTy, uint32_t RecordAlignment, |
| uint32_t &StartBitOffset, uint32_t &EndBitOffset); |
| uint32_t GetFieldInfo(uint32_t InfoKind, DICompositeType *CTy, |
| uint32_t AccessIndex, uint32_t PatchImm, |
| uint32_t RecordAlignment); |
| |
| Value *computeBaseAndAccessKey(CallInst *Call, CallInfo &CInfo, |
| std::string &AccessKey, MDNode *&BaseMeta); |
| uint64_t getConstant(const Value *IndexValue); |
| bool transformGEPChain(Module &M, CallInst *Call, CallInfo &CInfo); |
| }; |
| } // End anonymous namespace |
| |
| char BPFAbstractMemberAccess::ID = 0; |
| INITIALIZE_PASS(BPFAbstractMemberAccess, DEBUG_TYPE, |
| "abstracting struct/union member accessees", false, false) |
| |
| ModulePass *llvm::createBPFAbstractMemberAccess(BPFTargetMachine *TM) { |
| return new BPFAbstractMemberAccess(TM); |
| } |
| |
| bool BPFAbstractMemberAccess::runOnModule(Module &M) { |
| LLVM_DEBUG(dbgs() << "********** Abstract Member Accesses **********\n"); |
| |
| // Bail out if no debug info. |
| if (M.debug_compile_units().empty()) |
| return false; |
| |
| DL = &M.getDataLayout(); |
| return doTransformation(M); |
| } |
| |
| static bool SkipDIDerivedTag(unsigned Tag) { |
| if (Tag != dwarf::DW_TAG_typedef && Tag != dwarf::DW_TAG_const_type && |
| Tag != dwarf::DW_TAG_volatile_type && |
| Tag != dwarf::DW_TAG_restrict_type && |
| Tag != dwarf::DW_TAG_member) |
| return false; |
| return true; |
| } |
| |
| static DIType * stripQualifiers(DIType *Ty) { |
| while (auto *DTy = dyn_cast<DIDerivedType>(Ty)) { |
| if (!SkipDIDerivedTag(DTy->getTag())) |
| break; |
| Ty = DTy->getBaseType(); |
| } |
| return Ty; |
| } |
| |
| static const DIType * stripQualifiers(const DIType *Ty) { |
| while (auto *DTy = dyn_cast<DIDerivedType>(Ty)) { |
| if (!SkipDIDerivedTag(DTy->getTag())) |
| break; |
| Ty = DTy->getBaseType(); |
| } |
| return Ty; |
| } |
| |
| static uint32_t calcArraySize(const DICompositeType *CTy, uint32_t StartDim) { |
| DINodeArray Elements = CTy->getElements(); |
| uint32_t DimSize = 1; |
| for (uint32_t I = StartDim; I < Elements.size(); ++I) { |
| if (auto *Element = dyn_cast_or_null<DINode>(Elements[I])) |
| if (Element->getTag() == dwarf::DW_TAG_subrange_type) { |
| const DISubrange *SR = cast<DISubrange>(Element); |
| auto *CI = SR->getCount().dyn_cast<ConstantInt *>(); |
| DimSize *= CI->getSExtValue(); |
| } |
| } |
| |
| return DimSize; |
| } |
| |
| /// Check whether a call is a preserve_*_access_index intrinsic call or not. |
| bool BPFAbstractMemberAccess::IsPreserveDIAccessIndexCall(const CallInst *Call, |
| CallInfo &CInfo) { |
| if (!Call) |
| return false; |
| |
| const auto *GV = dyn_cast<GlobalValue>(Call->getCalledValue()); |
| if (!GV) |
| return false; |
| if (GV->getName().startswith("llvm.preserve.array.access.index")) { |
| CInfo.Kind = BPFPreserveArrayAI; |
| CInfo.Metadata = Call->getMetadata(LLVMContext::MD_preserve_access_index); |
| if (!CInfo.Metadata) |
| report_fatal_error("Missing metadata for llvm.preserve.array.access.index intrinsic"); |
| CInfo.AccessIndex = getConstant(Call->getArgOperand(2)); |
| CInfo.Base = Call->getArgOperand(0); |
| CInfo.RecordAlignment = |
| DL->getABITypeAlignment(CInfo.Base->getType()->getPointerElementType()); |
| return true; |
| } |
| if (GV->getName().startswith("llvm.preserve.union.access.index")) { |
| CInfo.Kind = BPFPreserveUnionAI; |
| CInfo.Metadata = Call->getMetadata(LLVMContext::MD_preserve_access_index); |
| if (!CInfo.Metadata) |
| report_fatal_error("Missing metadata for llvm.preserve.union.access.index intrinsic"); |
| CInfo.AccessIndex = getConstant(Call->getArgOperand(1)); |
| CInfo.Base = Call->getArgOperand(0); |
| CInfo.RecordAlignment = |
| DL->getABITypeAlignment(CInfo.Base->getType()->getPointerElementType()); |
| return true; |
| } |
| if (GV->getName().startswith("llvm.preserve.struct.access.index")) { |
| CInfo.Kind = BPFPreserveStructAI; |
| CInfo.Metadata = Call->getMetadata(LLVMContext::MD_preserve_access_index); |
| if (!CInfo.Metadata) |
| report_fatal_error("Missing metadata for llvm.preserve.struct.access.index intrinsic"); |
| CInfo.AccessIndex = getConstant(Call->getArgOperand(2)); |
| CInfo.Base = Call->getArgOperand(0); |
| CInfo.RecordAlignment = |
| DL->getABITypeAlignment(CInfo.Base->getType()->getPointerElementType()); |
| return true; |
| } |
| if (GV->getName().startswith("llvm.bpf.preserve.field.info")) { |
| CInfo.Kind = BPFPreserveFieldInfoAI; |
| CInfo.Metadata = nullptr; |
| // Check validity of info_kind as clang did not check this. |
| uint64_t InfoKind = getConstant(Call->getArgOperand(1)); |
| if (InfoKind >= BPFCoreSharedInfo::MAX_FIELD_RELOC_KIND) |
| report_fatal_error("Incorrect info_kind for llvm.bpf.preserve.field.info intrinsic"); |
| CInfo.AccessIndex = InfoKind; |
| return true; |
| } |
| |
| return false; |
| } |
| |
| void BPFAbstractMemberAccess::replaceWithGEP(std::vector<CallInst *> &CallList, |
| uint32_t DimensionIndex, |
| uint32_t GEPIndex) { |
| for (auto Call : CallList) { |
| uint32_t Dimension = 1; |
| if (DimensionIndex > 0) |
| Dimension = getConstant(Call->getArgOperand(DimensionIndex)); |
| |
| Constant *Zero = |
| ConstantInt::get(Type::getInt32Ty(Call->getParent()->getContext()), 0); |
| SmallVector<Value *, 4> IdxList; |
| for (unsigned I = 0; I < Dimension; ++I) |
| IdxList.push_back(Zero); |
| IdxList.push_back(Call->getArgOperand(GEPIndex)); |
| |
| auto *GEP = GetElementPtrInst::CreateInBounds(Call->getArgOperand(0), |
| IdxList, "", Call); |
| Call->replaceAllUsesWith(GEP); |
| Call->eraseFromParent(); |
| } |
| } |
| |
| bool BPFAbstractMemberAccess::removePreserveAccessIndexIntrinsic(Module &M) { |
| std::vector<CallInst *> PreserveArrayIndexCalls; |
| std::vector<CallInst *> PreserveUnionIndexCalls; |
| std::vector<CallInst *> PreserveStructIndexCalls; |
| bool Found = false; |
| |
| for (Function &F : M) |
| for (auto &BB : F) |
| for (auto &I : BB) { |
| auto *Call = dyn_cast<CallInst>(&I); |
| CallInfo CInfo; |
| if (!IsPreserveDIAccessIndexCall(Call, CInfo)) |
| continue; |
| |
| Found = true; |
| if (CInfo.Kind == BPFPreserveArrayAI) |
| PreserveArrayIndexCalls.push_back(Call); |
| else if (CInfo.Kind == BPFPreserveUnionAI) |
| PreserveUnionIndexCalls.push_back(Call); |
| else |
| PreserveStructIndexCalls.push_back(Call); |
| } |
| |
| // do the following transformation: |
| // . addr = preserve_array_access_index(base, dimension, index) |
| // is transformed to |
| // addr = GEP(base, dimenion's zero's, index) |
| // . addr = preserve_union_access_index(base, di_index) |
| // is transformed to |
| // addr = base, i.e., all usages of "addr" are replaced by "base". |
| // . addr = preserve_struct_access_index(base, gep_index, di_index) |
| // is transformed to |
| // addr = GEP(base, 0, gep_index) |
| replaceWithGEP(PreserveArrayIndexCalls, 1, 2); |
| replaceWithGEP(PreserveStructIndexCalls, 0, 1); |
| for (auto Call : PreserveUnionIndexCalls) { |
| Call->replaceAllUsesWith(Call->getArgOperand(0)); |
| Call->eraseFromParent(); |
| } |
| |
| return Found; |
| } |
| |
| /// Check whether the access index chain is valid. We check |
| /// here because there may be type casts between two |
| /// access indexes. We want to ensure memory access still valid. |
| bool BPFAbstractMemberAccess::IsValidAIChain(const MDNode *ParentType, |
| uint32_t ParentAI, |
| const MDNode *ChildType) { |
| if (!ChildType) |
| return true; // preserve_field_info, no type comparison needed. |
| |
| const DIType *PType = stripQualifiers(cast<DIType>(ParentType)); |
| const DIType *CType = stripQualifiers(cast<DIType>(ChildType)); |
| |
| // Child is a derived/pointer type, which is due to type casting. |
| // Pointer type cannot be in the middle of chain. |
| if (isa<DIDerivedType>(CType)) |
| return false; |
| |
| // Parent is a pointer type. |
| if (const auto *PtrTy = dyn_cast<DIDerivedType>(PType)) { |
| if (PtrTy->getTag() != dwarf::DW_TAG_pointer_type) |
| return false; |
| return stripQualifiers(PtrTy->getBaseType()) == CType; |
| } |
| |
| // Otherwise, struct/union/array types |
| const auto *PTy = dyn_cast<DICompositeType>(PType); |
| const auto *CTy = dyn_cast<DICompositeType>(CType); |
| assert(PTy && CTy && "ParentType or ChildType is null or not composite"); |
| |
| uint32_t PTyTag = PTy->getTag(); |
| assert(PTyTag == dwarf::DW_TAG_array_type || |
| PTyTag == dwarf::DW_TAG_structure_type || |
| PTyTag == dwarf::DW_TAG_union_type); |
| |
| uint32_t CTyTag = CTy->getTag(); |
| assert(CTyTag == dwarf::DW_TAG_array_type || |
| CTyTag == dwarf::DW_TAG_structure_type || |
| CTyTag == dwarf::DW_TAG_union_type); |
| |
| // Multi dimensional arrays, base element should be the same |
| if (PTyTag == dwarf::DW_TAG_array_type && PTyTag == CTyTag) |
| return PTy->getBaseType() == CTy->getBaseType(); |
| |
| DIType *Ty; |
| if (PTyTag == dwarf::DW_TAG_array_type) |
| Ty = PTy->getBaseType(); |
| else |
| Ty = dyn_cast<DIType>(PTy->getElements()[ParentAI]); |
| |
| return dyn_cast<DICompositeType>(stripQualifiers(Ty)) == CTy; |
| } |
| |
| void BPFAbstractMemberAccess::traceAICall(CallInst *Call, |
| CallInfo &ParentInfo) { |
| for (User *U : Call->users()) { |
| Instruction *Inst = dyn_cast<Instruction>(U); |
| if (!Inst) |
| continue; |
| |
| if (auto *BI = dyn_cast<BitCastInst>(Inst)) { |
| traceBitCast(BI, Call, ParentInfo); |
| } else if (auto *CI = dyn_cast<CallInst>(Inst)) { |
| CallInfo ChildInfo; |
| |
| if (IsPreserveDIAccessIndexCall(CI, ChildInfo) && |
| IsValidAIChain(ParentInfo.Metadata, ParentInfo.AccessIndex, |
| ChildInfo.Metadata)) { |
| AIChain[CI] = std::make_pair(Call, ParentInfo); |
| traceAICall(CI, ChildInfo); |
| } else { |
| BaseAICalls[Call] = ParentInfo; |
| } |
| } else if (auto *GI = dyn_cast<GetElementPtrInst>(Inst)) { |
| if (GI->hasAllZeroIndices()) |
| traceGEP(GI, Call, ParentInfo); |
| else |
| BaseAICalls[Call] = ParentInfo; |
| } else { |
| BaseAICalls[Call] = ParentInfo; |
| } |
| } |
| } |
| |
| void BPFAbstractMemberAccess::traceBitCast(BitCastInst *BitCast, |
| CallInst *Parent, |
| CallInfo &ParentInfo) { |
| for (User *U : BitCast->users()) { |
| Instruction *Inst = dyn_cast<Instruction>(U); |
| if (!Inst) |
| continue; |
| |
| if (auto *BI = dyn_cast<BitCastInst>(Inst)) { |
| traceBitCast(BI, Parent, ParentInfo); |
| } else if (auto *CI = dyn_cast<CallInst>(Inst)) { |
| CallInfo ChildInfo; |
| if (IsPreserveDIAccessIndexCall(CI, ChildInfo) && |
| IsValidAIChain(ParentInfo.Metadata, ParentInfo.AccessIndex, |
| ChildInfo.Metadata)) { |
| AIChain[CI] = std::make_pair(Parent, ParentInfo); |
| traceAICall(CI, ChildInfo); |
| } else { |
| BaseAICalls[Parent] = ParentInfo; |
| } |
| } else if (auto *GI = dyn_cast<GetElementPtrInst>(Inst)) { |
| if (GI->hasAllZeroIndices()) |
| traceGEP(GI, Parent, ParentInfo); |
| else |
| BaseAICalls[Parent] = ParentInfo; |
| } else { |
| BaseAICalls[Parent] = ParentInfo; |
| } |
| } |
| } |
| |
| void BPFAbstractMemberAccess::traceGEP(GetElementPtrInst *GEP, CallInst *Parent, |
| CallInfo &ParentInfo) { |
| for (User *U : GEP->users()) { |
| Instruction *Inst = dyn_cast<Instruction>(U); |
| if (!Inst) |
| continue; |
| |
| if (auto *BI = dyn_cast<BitCastInst>(Inst)) { |
| traceBitCast(BI, Parent, ParentInfo); |
| } else if (auto *CI = dyn_cast<CallInst>(Inst)) { |
| CallInfo ChildInfo; |
| if (IsPreserveDIAccessIndexCall(CI, ChildInfo) && |
| IsValidAIChain(ParentInfo.Metadata, ParentInfo.AccessIndex, |
| ChildInfo.Metadata)) { |
| AIChain[CI] = std::make_pair(Parent, ParentInfo); |
| traceAICall(CI, ChildInfo); |
| } else { |
| BaseAICalls[Parent] = ParentInfo; |
| } |
| } else if (auto *GI = dyn_cast<GetElementPtrInst>(Inst)) { |
| if (GI->hasAllZeroIndices()) |
| traceGEP(GI, Parent, ParentInfo); |
| else |
| BaseAICalls[Parent] = ParentInfo; |
| } else { |
| BaseAICalls[Parent] = ParentInfo; |
| } |
| } |
| } |
| |
| void BPFAbstractMemberAccess::collectAICallChains(Module &M, Function &F) { |
| AIChain.clear(); |
| BaseAICalls.clear(); |
| |
| for (auto &BB : F) |
| for (auto &I : BB) { |
| CallInfo CInfo; |
| auto *Call = dyn_cast<CallInst>(&I); |
| if (!IsPreserveDIAccessIndexCall(Call, CInfo) || |
| AIChain.find(Call) != AIChain.end()) |
| continue; |
| |
| traceAICall(Call, CInfo); |
| } |
| } |
| |
| uint64_t BPFAbstractMemberAccess::getConstant(const Value *IndexValue) { |
| const ConstantInt *CV = dyn_cast<ConstantInt>(IndexValue); |
| assert(CV); |
| return CV->getValue().getZExtValue(); |
| } |
| |
| /// Get the start and the end of storage offset for \p MemberTy. |
| void BPFAbstractMemberAccess::GetStorageBitRange(DIDerivedType *MemberTy, |
| uint32_t RecordAlignment, |
| uint32_t &StartBitOffset, |
| uint32_t &EndBitOffset) { |
| uint32_t MemberBitSize = MemberTy->getSizeInBits(); |
| uint32_t MemberBitOffset = MemberTy->getOffsetInBits(); |
| uint32_t AlignBits = RecordAlignment * 8; |
| if (RecordAlignment > 8 || MemberBitSize > AlignBits) |
| report_fatal_error("Unsupported field expression for llvm.bpf.preserve.field.info, " |
| "requiring too big alignment"); |
| |
| StartBitOffset = MemberBitOffset & ~(AlignBits - 1); |
| if ((StartBitOffset + AlignBits) < (MemberBitOffset + MemberBitSize)) |
| report_fatal_error("Unsupported field expression for llvm.bpf.preserve.field.info, " |
| "cross alignment boundary"); |
| EndBitOffset = StartBitOffset + AlignBits; |
| } |
| |
| uint32_t BPFAbstractMemberAccess::GetFieldInfo(uint32_t InfoKind, |
| DICompositeType *CTy, |
| uint32_t AccessIndex, |
| uint32_t PatchImm, |
| uint32_t RecordAlignment) { |
| if (InfoKind == BPFCoreSharedInfo::FIELD_EXISTENCE) |
| return 1; |
| |
| uint32_t Tag = CTy->getTag(); |
| if (InfoKind == BPFCoreSharedInfo::FIELD_BYTE_OFFSET) { |
| if (Tag == dwarf::DW_TAG_array_type) { |
| auto *EltTy = stripQualifiers(CTy->getBaseType()); |
| PatchImm += AccessIndex * calcArraySize(CTy, 1) * |
| (EltTy->getSizeInBits() >> 3); |
| } else if (Tag == dwarf::DW_TAG_structure_type) { |
| auto *MemberTy = cast<DIDerivedType>(CTy->getElements()[AccessIndex]); |
| if (!MemberTy->isBitField()) { |
| PatchImm += MemberTy->getOffsetInBits() >> 3; |
| } else { |
| unsigned SBitOffset, NextSBitOffset; |
| GetStorageBitRange(MemberTy, RecordAlignment, SBitOffset, |
| NextSBitOffset); |
| PatchImm += SBitOffset >> 3; |
| } |
| } |
| return PatchImm; |
| } |
| |
| if (InfoKind == BPFCoreSharedInfo::FIELD_BYTE_SIZE) { |
| if (Tag == dwarf::DW_TAG_array_type) { |
| auto *EltTy = stripQualifiers(CTy->getBaseType()); |
| return calcArraySize(CTy, 1) * (EltTy->getSizeInBits() >> 3); |
| } else { |
| auto *MemberTy = cast<DIDerivedType>(CTy->getElements()[AccessIndex]); |
| uint32_t SizeInBits = MemberTy->getSizeInBits(); |
| if (!MemberTy->isBitField()) |
| return SizeInBits >> 3; |
| |
| unsigned SBitOffset, NextSBitOffset; |
| GetStorageBitRange(MemberTy, RecordAlignment, SBitOffset, NextSBitOffset); |
| SizeInBits = NextSBitOffset - SBitOffset; |
| if (SizeInBits & (SizeInBits - 1)) |
| report_fatal_error("Unsupported field expression for llvm.bpf.preserve.field.info"); |
| return SizeInBits >> 3; |
| } |
| } |
| |
| if (InfoKind == BPFCoreSharedInfo::FIELD_SIGNEDNESS) { |
| const DIType *BaseTy; |
| if (Tag == dwarf::DW_TAG_array_type) { |
| // Signedness only checked when final array elements are accessed. |
| if (CTy->getElements().size() != 1) |
| report_fatal_error("Invalid array expression for llvm.bpf.preserve.field.info"); |
| BaseTy = stripQualifiers(CTy->getBaseType()); |
| } else { |
| auto *MemberTy = cast<DIDerivedType>(CTy->getElements()[AccessIndex]); |
| BaseTy = stripQualifiers(MemberTy->getBaseType()); |
| } |
| |
| // Only basic types and enum types have signedness. |
| const auto *BTy = dyn_cast<DIBasicType>(BaseTy); |
| while (!BTy) { |
| const auto *CompTy = dyn_cast<DICompositeType>(BaseTy); |
| // Report an error if the field expression does not have signedness. |
| if (!CompTy || CompTy->getTag() != dwarf::DW_TAG_enumeration_type) |
| report_fatal_error("Invalid field expression for llvm.bpf.preserve.field.info"); |
| BaseTy = stripQualifiers(CompTy->getBaseType()); |
| BTy = dyn_cast<DIBasicType>(BaseTy); |
| } |
| uint32_t Encoding = BTy->getEncoding(); |
| return (Encoding == dwarf::DW_ATE_signed || Encoding == dwarf::DW_ATE_signed_char); |
| } |
| |
| if (InfoKind == BPFCoreSharedInfo::FIELD_LSHIFT_U64) { |
| // The value is loaded into a value with FIELD_BYTE_SIZE size, |
| // and then zero or sign extended to U64. |
| // FIELD_LSHIFT_U64 and FIELD_RSHIFT_U64 are operations |
| // to extract the original value. |
| const Triple &Triple = TM->getTargetTriple(); |
| DIDerivedType *MemberTy = nullptr; |
| bool IsBitField = false; |
| uint32_t SizeInBits; |
| |
| if (Tag == dwarf::DW_TAG_array_type) { |
| auto *EltTy = stripQualifiers(CTy->getBaseType()); |
| SizeInBits = calcArraySize(CTy, 1) * EltTy->getSizeInBits(); |
| } else { |
| MemberTy = cast<DIDerivedType>(CTy->getElements()[AccessIndex]); |
| SizeInBits = MemberTy->getSizeInBits(); |
| IsBitField = MemberTy->isBitField(); |
| } |
| |
| if (!IsBitField) { |
| if (SizeInBits > 64) |
| report_fatal_error("too big field size for llvm.bpf.preserve.field.info"); |
| return 64 - SizeInBits; |
| } |
| |
| unsigned SBitOffset, NextSBitOffset; |
| GetStorageBitRange(MemberTy, RecordAlignment, SBitOffset, NextSBitOffset); |
| if (NextSBitOffset - SBitOffset > 64) |
| report_fatal_error("too big field size for llvm.bpf.preserve.field.info"); |
| |
| unsigned OffsetInBits = MemberTy->getOffsetInBits(); |
| if (Triple.getArch() == Triple::bpfel) |
| return SBitOffset + 64 - OffsetInBits - SizeInBits; |
| else |
| return OffsetInBits + 64 - NextSBitOffset; |
| } |
| |
| if (InfoKind == BPFCoreSharedInfo::FIELD_RSHIFT_U64) { |
| DIDerivedType *MemberTy = nullptr; |
| bool IsBitField = false; |
| uint32_t SizeInBits; |
| if (Tag == dwarf::DW_TAG_array_type) { |
| auto *EltTy = stripQualifiers(CTy->getBaseType()); |
| SizeInBits = calcArraySize(CTy, 1) * EltTy->getSizeInBits(); |
| } else { |
| MemberTy = cast<DIDerivedType>(CTy->getElements()[AccessIndex]); |
| SizeInBits = MemberTy->getSizeInBits(); |
| IsBitField = MemberTy->isBitField(); |
| } |
| |
| if (!IsBitField) { |
| if (SizeInBits > 64) |
| report_fatal_error("too big field size for llvm.bpf.preserve.field.info"); |
| return 64 - SizeInBits; |
| } |
| |
| unsigned SBitOffset, NextSBitOffset; |
| GetStorageBitRange(MemberTy, RecordAlignment, SBitOffset, NextSBitOffset); |
| if (NextSBitOffset - SBitOffset > 64) |
| report_fatal_error("too big field size for llvm.bpf.preserve.field.info"); |
| |
| return 64 - SizeInBits; |
| } |
| |
| llvm_unreachable("Unknown llvm.bpf.preserve.field.info info kind"); |
| } |
| |
| bool BPFAbstractMemberAccess::HasPreserveFieldInfoCall(CallInfoStack &CallStack) { |
| // This is called in error return path, no need to maintain CallStack. |
| while (CallStack.size()) { |
| auto StackElem = CallStack.top(); |
| if (StackElem.second.Kind == BPFPreserveFieldInfoAI) |
| return true; |
| CallStack.pop(); |
| } |
| return false; |
| } |
| |
| /// Compute the base of the whole preserve_* intrinsics chains, i.e., the base |
| /// pointer of the first preserve_*_access_index call, and construct the access |
| /// string, which will be the name of a global variable. |
| Value *BPFAbstractMemberAccess::computeBaseAndAccessKey(CallInst *Call, |
| CallInfo &CInfo, |
| std::string &AccessKey, |
| MDNode *&TypeMeta) { |
| Value *Base = nullptr; |
| std::string TypeName; |
| CallInfoStack CallStack; |
| |
| // Put the access chain into a stack with the top as the head of the chain. |
| while (Call) { |
| CallStack.push(std::make_pair(Call, CInfo)); |
| CInfo = AIChain[Call].second; |
| Call = AIChain[Call].first; |
| } |
| |
| // The access offset from the base of the head of chain is also |
| // calculated here as all debuginfo types are available. |
| |
| // Get type name and calculate the first index. |
| // We only want to get type name from structure or union. |
| // If user wants a relocation like |
| // int *p; ... __builtin_preserve_access_index(&p[4]) ... |
| // or |
| // int a[10][20]; ... __builtin_preserve_access_index(&a[2][3]) ... |
| // we will skip them. |
| uint32_t FirstIndex = 0; |
| uint32_t PatchImm = 0; // AccessOffset or the requested field info |
| uint32_t InfoKind = BPFCoreSharedInfo::FIELD_BYTE_OFFSET; |
| while (CallStack.size()) { |
| auto StackElem = CallStack.top(); |
| Call = StackElem.first; |
| CInfo = StackElem.second; |
| |
| if (!Base) |
| Base = CInfo.Base; |
| |
| DIType *Ty = stripQualifiers(cast<DIType>(CInfo.Metadata)); |
| if (CInfo.Kind == BPFPreserveUnionAI || |
| CInfo.Kind == BPFPreserveStructAI) { |
| // struct or union type |
| TypeName = Ty->getName(); |
| TypeMeta = Ty; |
| PatchImm += FirstIndex * (Ty->getSizeInBits() >> 3); |
| break; |
| } |
| |
| assert(CInfo.Kind == BPFPreserveArrayAI); |
| |
| // Array entries will always be consumed for accumulative initial index. |
| CallStack.pop(); |
| |
| // BPFPreserveArrayAI |
| uint64_t AccessIndex = CInfo.AccessIndex; |
| |
| DIType *BaseTy = nullptr; |
| bool CheckElemType = false; |
| if (const auto *CTy = dyn_cast<DICompositeType>(Ty)) { |
| // array type |
| assert(CTy->getTag() == dwarf::DW_TAG_array_type); |
| |
| |
| FirstIndex += AccessIndex * calcArraySize(CTy, 1); |
| BaseTy = stripQualifiers(CTy->getBaseType()); |
| CheckElemType = CTy->getElements().size() == 1; |
| } else { |
| // pointer type |
| auto *DTy = cast<DIDerivedType>(Ty); |
| assert(DTy->getTag() == dwarf::DW_TAG_pointer_type); |
| |
| BaseTy = stripQualifiers(DTy->getBaseType()); |
| CTy = dyn_cast<DICompositeType>(BaseTy); |
| if (!CTy) { |
| CheckElemType = true; |
| } else if (CTy->getTag() != dwarf::DW_TAG_array_type) { |
| FirstIndex += AccessIndex; |
| CheckElemType = true; |
| } else { |
| FirstIndex += AccessIndex * calcArraySize(CTy, 0); |
| } |
| } |
| |
| if (CheckElemType) { |
| auto *CTy = dyn_cast<DICompositeType>(BaseTy); |
| if (!CTy) { |
| if (HasPreserveFieldInfoCall(CallStack)) |
| report_fatal_error("Invalid field access for llvm.preserve.field.info intrinsic"); |
| return nullptr; |
| } |
| |
| unsigned CTag = CTy->getTag(); |
| if (CTag == dwarf::DW_TAG_structure_type || CTag == dwarf::DW_TAG_union_type) { |
| TypeName = CTy->getName(); |
| } else { |
| if (HasPreserveFieldInfoCall(CallStack)) |
| report_fatal_error("Invalid field access for llvm.preserve.field.info intrinsic"); |
| return nullptr; |
| } |
| TypeMeta = CTy; |
| PatchImm += FirstIndex * (CTy->getSizeInBits() >> 3); |
| break; |
| } |
| } |
| assert(TypeName.size()); |
| AccessKey += std::to_string(FirstIndex); |
| |
| // Traverse the rest of access chain to complete offset calculation |
| // and access key construction. |
| while (CallStack.size()) { |
| auto StackElem = CallStack.top(); |
| CInfo = StackElem.second; |
| CallStack.pop(); |
| |
| if (CInfo.Kind == BPFPreserveFieldInfoAI) |
| break; |
| |
| // If the next Call (the top of the stack) is a BPFPreserveFieldInfoAI, |
| // the action will be extracting field info. |
| if (CallStack.size()) { |
| auto StackElem2 = CallStack.top(); |
| CallInfo CInfo2 = StackElem2.second; |
| if (CInfo2.Kind == BPFPreserveFieldInfoAI) { |
| InfoKind = CInfo2.AccessIndex; |
| assert(CallStack.size() == 1); |
| } |
| } |
| |
| // Access Index |
| uint64_t AccessIndex = CInfo.AccessIndex; |
| AccessKey += ":" + std::to_string(AccessIndex); |
| |
| MDNode *MDN = CInfo.Metadata; |
| uint32_t RecordAlignment = CInfo.RecordAlignment; |
| // At this stage, it cannot be pointer type. |
| auto *CTy = cast<DICompositeType>(stripQualifiers(cast<DIType>(MDN))); |
| PatchImm = GetFieldInfo(InfoKind, CTy, AccessIndex, PatchImm, |
| RecordAlignment); |
| } |
| |
| // Access key is the |
| // "llvm." + type name + ":" + reloc type + ":" + patched imm + "$" + |
| // access string, |
| // uniquely identifying one relocation. |
| // The prefix "llvm." indicates this is a temporary global, which should |
| // not be emitted to ELF file. |
| AccessKey = "llvm." + TypeName + ":" + std::to_string(InfoKind) + ":" + |
| std::to_string(PatchImm) + "$" + AccessKey; |
| |
| return Base; |
| } |
| |
| /// Call/Kind is the base preserve_*_access_index() call. Attempts to do |
| /// transformation to a chain of relocable GEPs. |
| bool BPFAbstractMemberAccess::transformGEPChain(Module &M, CallInst *Call, |
| CallInfo &CInfo) { |
| std::string AccessKey; |
| MDNode *TypeMeta; |
| Value *Base = |
| computeBaseAndAccessKey(Call, CInfo, AccessKey, TypeMeta); |
| if (!Base) |
| return false; |
| |
| BasicBlock *BB = Call->getParent(); |
| GlobalVariable *GV; |
| |
| if (GEPGlobals.find(AccessKey) == GEPGlobals.end()) { |
| IntegerType *VarType; |
| if (CInfo.Kind == BPFPreserveFieldInfoAI) |
| VarType = Type::getInt32Ty(BB->getContext()); // 32bit return value |
| else |
| VarType = Type::getInt64Ty(BB->getContext()); // 64bit ptr arith |
| |
| GV = new GlobalVariable(M, VarType, false, GlobalVariable::ExternalLinkage, |
| NULL, AccessKey); |
| GV->addAttribute(BPFCoreSharedInfo::AmaAttr); |
| GV->setMetadata(LLVMContext::MD_preserve_access_index, TypeMeta); |
| GEPGlobals[AccessKey] = GV; |
| } else { |
| GV = GEPGlobals[AccessKey]; |
| } |
| |
| if (CInfo.Kind == BPFPreserveFieldInfoAI) { |
| // Load the global variable which represents the returned field info. |
| auto *LDInst = new LoadInst(Type::getInt32Ty(BB->getContext()), GV); |
| BB->getInstList().insert(Call->getIterator(), LDInst); |
| Call->replaceAllUsesWith(LDInst); |
| Call->eraseFromParent(); |
| return true; |
| } |
| |
| // For any original GEP Call and Base %2 like |
| // %4 = bitcast %struct.net_device** %dev1 to i64* |
| // it is transformed to: |
| // %6 = load sk_buff:50:$0:0:0:2:0 |
| // %7 = bitcast %struct.sk_buff* %2 to i8* |
| // %8 = getelementptr i8, i8* %7, %6 |
| // %9 = bitcast i8* %8 to i64* |
| // using %9 instead of %4 |
| // The original Call inst is removed. |
| |
| // Load the global variable. |
| auto *LDInst = new LoadInst(Type::getInt64Ty(BB->getContext()), GV); |
| BB->getInstList().insert(Call->getIterator(), LDInst); |
| |
| // Generate a BitCast |
| auto *BCInst = new BitCastInst(Base, Type::getInt8PtrTy(BB->getContext())); |
| BB->getInstList().insert(Call->getIterator(), BCInst); |
| |
| // Generate a GetElementPtr |
| auto *GEP = GetElementPtrInst::Create(Type::getInt8Ty(BB->getContext()), |
| BCInst, LDInst); |
| BB->getInstList().insert(Call->getIterator(), GEP); |
| |
| // Generate a BitCast |
| auto *BCInst2 = new BitCastInst(GEP, Call->getType()); |
| BB->getInstList().insert(Call->getIterator(), BCInst2); |
| |
| Call->replaceAllUsesWith(BCInst2); |
| Call->eraseFromParent(); |
| |
| return true; |
| } |
| |
| bool BPFAbstractMemberAccess::doTransformation(Module &M) { |
| bool Transformed = false; |
| |
| for (Function &F : M) { |
| // Collect PreserveDIAccessIndex Intrinsic call chains. |
| // The call chains will be used to generate the access |
| // patterns similar to GEP. |
| collectAICallChains(M, F); |
| |
| for (auto &C : BaseAICalls) |
| Transformed = transformGEPChain(M, C.first, C.second) || Transformed; |
| } |
| |
| return removePreserveAccessIndexIntrinsic(M) || Transformed; |
| } |
