1 //===- Target.h -------------------------------------------------*- C++ -*-===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 9 #ifndef LLD_MACHO_TARGET_H 10 #define LLD_MACHO_TARGET_H 11 12 #include "MachOStructs.h" 13 #include "Relocations.h" 14 15 #include "llvm/ADT/BitmaskEnum.h" 16 #include "llvm/BinaryFormat/MachO.h" 17 #include "llvm/Support/MathExtras.h" 18 #include "llvm/Support/MemoryBuffer.h" 19 20 #include <cstddef> 21 #include <cstdint> 22 23 #include "mach-o/compact_unwind_encoding.h" 24 25 namespace lld::macho { 26 LLVM_ENABLE_BITMASK_ENUMS_IN_NAMESPACE(); 27 28 class Symbol; 29 class Defined; 30 class DylibSymbol; 31 class InputSection; 32 class ObjFile; 33 34 static_assert(static_cast<uint32_t>(UNWIND_X86_64_MODE_MASK) == 35 static_cast<uint32_t>(UNWIND_X86_MODE_MASK) && 36 static_cast<uint32_t>(UNWIND_ARM64_MODE_MASK) == 37 static_cast<uint32_t>(UNWIND_X86_64_MODE_MASK)); 38 39 // Since the mode masks have the same value on all targets, define 40 // a common one for convenience. 41 constexpr uint32_t UNWIND_MODE_MASK = UNWIND_X86_64_MODE_MASK; 42 43 class TargetInfo { 44 public: 45 template <class LP> TargetInfo(LP) { 46 // Having these values available in TargetInfo allows us to access them 47 // without having to resort to templates. 48 magic = LP::magic; 49 pageZeroSize = LP::pageZeroSize; 50 headerSize = sizeof(typename LP::mach_header); 51 wordSize = LP::wordSize; 52 p2WordSize = llvm::CTLog2<LP::wordSize>(); 53 } 54 55 virtual ~TargetInfo() = default; 56 57 // Validate the relocation structure and get its addend. 58 virtual int64_t 59 getEmbeddedAddend(llvm::MemoryBufferRef, uint64_t offset, 60 const llvm::MachO::relocation_info) const = 0; 61 virtual void relocateOne(uint8_t *loc, const Reloc &, uint64_t va, 62 uint64_t relocVA) const = 0; 63 64 // Write code for lazy binding. See the comments on StubsSection for more 65 // details. 66 virtual void writeStub(uint8_t *buf, const Symbol &, 67 uint64_t pointerVA) const = 0; 68 virtual void writeStubHelperHeader(uint8_t *buf) const = 0; 69 virtual void writeStubHelperEntry(uint8_t *buf, const Symbol &, 70 uint64_t entryAddr) const = 0; 71 72 virtual void writeObjCMsgSendStub(uint8_t *buf, Symbol *sym, 73 uint64_t stubsAddr, uint64_t &stubOffset, 74 uint64_t selrefVA, 75 Symbol *objcMsgSend) const = 0; 76 77 // Init 'thunk' so that it be a direct jump to 'branchTarget'. 78 virtual void initICFSafeThunkBody(InputSection *thunk, 79 InputSection *branchTarget) const { 80 llvm_unreachable("target does not support ICF safe thunks"); 81 } 82 83 // Given a thunk for which `initICFSafeThunkBody` was called, return the 84 // branchTarget it was initialized with. 85 virtual InputSection *getThunkBranchTarget(InputSection *thunk) const { 86 llvm_unreachable("target does not support ICF safe thunks"); 87 } 88 89 virtual uint32_t getICFSafeThunkSize() const { 90 llvm_unreachable("target does not support ICF safe thunks"); 91 } 92 93 // Symbols may be referenced via either the GOT or the stubs section, 94 // depending on the relocation type. prepareSymbolRelocation() will set up the 95 // GOT/stubs entries, and resolveSymbolVA() will return the addresses of those 96 // entries. resolveSymbolVA() may also relax the target instructions to save 97 // on a level of address indirection. 98 virtual void relaxGotLoad(uint8_t *loc, uint8_t type) const = 0; 99 100 virtual uint64_t getPageSize() const = 0; 101 102 virtual void populateThunk(InputSection *thunk, Symbol *funcSym) { 103 llvm_unreachable("target does not use thunks"); 104 } 105 106 const RelocAttrs &getRelocAttrs(uint8_t type) const { 107 assert(type < relocAttrs.size() && "invalid relocation type"); 108 if (type >= relocAttrs.size()) 109 return invalidRelocAttrs; 110 return relocAttrs[type]; 111 } 112 113 bool hasAttr(uint8_t type, RelocAttrBits bit) const { 114 return getRelocAttrs(type).hasAttr(bit); 115 } 116 117 bool usesThunks() const { return thunkSize > 0; } 118 119 // For now, handleDtraceReloc only implements -no_dtrace_dof, and ensures 120 // that the linking would not fail even when there are user-provided dtrace 121 // symbols. However, unlike ld64, lld currently does not emit __dof sections. 122 virtual void handleDtraceReloc(const Symbol *sym, const Reloc &r, 123 uint8_t *loc) const { 124 llvm_unreachable("Unsupported architecture for dtrace symbols"); 125 } 126 127 virtual void applyOptimizationHints(uint8_t *, const ObjFile &) const {}; 128 129 uint32_t magic; 130 llvm::MachO::CPUType cpuType; 131 uint32_t cpuSubtype; 132 133 uint64_t pageZeroSize; 134 size_t headerSize; 135 size_t stubSize; 136 size_t stubHelperHeaderSize; 137 size_t stubHelperEntrySize; 138 size_t objcStubsFastSize; 139 size_t objcStubsSmallSize; 140 size_t objcStubsFastAlignment; 141 size_t objcStubsSmallAlignment; 142 uint8_t p2WordSize; 143 size_t wordSize; 144 145 size_t thunkSize = 0; 146 uint64_t forwardBranchRange = 0; 147 uint64_t backwardBranchRange = 0; 148 149 uint32_t modeDwarfEncoding; 150 uint8_t subtractorRelocType; 151 uint8_t unsignedRelocType; 152 153 llvm::ArrayRef<RelocAttrs> relocAttrs; 154 155 // We contrive this value as sufficiently far from any valid address that it 156 // will always be out-of-range for any architecture. UINT64_MAX is not a 157 // good choice because it is (a) only 1 away from wrapping to 0, and (b) the 158 // tombstone value for DenseMap<> and caused weird assertions for me. 159 static constexpr uint64_t outOfRangeVA = 0xfull << 60; 160 }; 161 162 TargetInfo *createX86_64TargetInfo(); 163 TargetInfo *createARM64TargetInfo(); 164 TargetInfo *createARM64_32TargetInfo(); 165 166 struct LP64 { 167 using mach_header = llvm::MachO::mach_header_64; 168 using nlist = structs::nlist_64; 169 using segment_command = llvm::MachO::segment_command_64; 170 using section = llvm::MachO::section_64; 171 using encryption_info_command = llvm::MachO::encryption_info_command_64; 172 173 static constexpr uint32_t magic = llvm::MachO::MH_MAGIC_64; 174 static constexpr uint32_t segmentLCType = llvm::MachO::LC_SEGMENT_64; 175 static constexpr uint32_t encryptionInfoLCType = 176 llvm::MachO::LC_ENCRYPTION_INFO_64; 177 178 static constexpr uint64_t pageZeroSize = 1ull << 32; 179 static constexpr size_t wordSize = 8; 180 }; 181 182 struct ILP32 { 183 using mach_header = llvm::MachO::mach_header; 184 using nlist = structs::nlist; 185 using segment_command = llvm::MachO::segment_command; 186 using section = llvm::MachO::section; 187 using encryption_info_command = llvm::MachO::encryption_info_command; 188 189 static constexpr uint32_t magic = llvm::MachO::MH_MAGIC; 190 static constexpr uint32_t segmentLCType = llvm::MachO::LC_SEGMENT; 191 static constexpr uint32_t encryptionInfoLCType = 192 llvm::MachO::LC_ENCRYPTION_INFO; 193 194 static constexpr uint64_t pageZeroSize = 1ull << 12; 195 static constexpr size_t wordSize = 4; 196 }; 197 198 extern TargetInfo *target; 199 200 } // namespace lld::macho 201 202 #endif 203