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 selrefsVA, uint64_t selectorIndex,
75                                     uint64_t gotAddr,
76                                     uint64_t msgSendIndex) const = 0;
77 
78   // Symbols may be referenced via either the GOT or the stubs section,
79   // depending on the relocation type. prepareSymbolRelocation() will set up the
80   // GOT/stubs entries, and resolveSymbolVA() will return the addresses of those
81   // entries. resolveSymbolVA() may also relax the target instructions to save
82   // on a level of address indirection.
83   virtual void relaxGotLoad(uint8_t *loc, uint8_t type) const = 0;
84 
85   virtual uint64_t getPageSize() const = 0;
86 
87   virtual void populateThunk(InputSection *thunk, Symbol *funcSym) {
88     llvm_unreachable("target does not use thunks");
89   }
90 
91   const RelocAttrs &getRelocAttrs(uint8_t type) const {
92     assert(type < relocAttrs.size() && "invalid relocation type");
93     if (type >= relocAttrs.size())
94       return invalidRelocAttrs;
95     return relocAttrs[type];
96   }
97 
98   bool hasAttr(uint8_t type, RelocAttrBits bit) const {
99     return getRelocAttrs(type).hasAttr(bit);
100   }
101 
102   bool usesThunks() const { return thunkSize > 0; }
103 
104   // For now, handleDtraceReloc only implements -no_dtrace_dof, and ensures
105   // that the linking would not fail even when there are user-provided dtrace
106   // symbols. However, unlike ld64, lld currently does not emit __dof sections.
107   virtual void handleDtraceReloc(const Symbol *sym, const Reloc &r,
108                                  uint8_t *loc) const {
109     llvm_unreachable("Unsupported architecture for dtrace symbols");
110   }
111 
112   virtual void applyOptimizationHints(uint8_t *, const ObjFile &) const {};
113 
114   uint32_t magic;
115   llvm::MachO::CPUType cpuType;
116   uint32_t cpuSubtype;
117 
118   uint64_t pageZeroSize;
119   size_t headerSize;
120   size_t stubSize;
121   size_t stubHelperHeaderSize;
122   size_t stubHelperEntrySize;
123   size_t objcStubsFastSize;
124   size_t objcStubsAlignment;
125   uint8_t p2WordSize;
126   size_t wordSize;
127 
128   size_t thunkSize = 0;
129   uint64_t forwardBranchRange = 0;
130   uint64_t backwardBranchRange = 0;
131 
132   uint32_t modeDwarfEncoding;
133   uint8_t subtractorRelocType;
134   uint8_t unsignedRelocType;
135 
136   llvm::ArrayRef<RelocAttrs> relocAttrs;
137 
138   // We contrive this value as sufficiently far from any valid address that it
139   // will always be out-of-range for any architecture. UINT64_MAX is not a
140   // good choice because it is (a) only 1 away from wrapping to 0, and (b) the
141   // tombstone value for DenseMap<> and caused weird assertions for me.
142   static constexpr uint64_t outOfRangeVA = 0xfull << 60;
143 };
144 
145 TargetInfo *createX86_64TargetInfo();
146 TargetInfo *createARM64TargetInfo();
147 TargetInfo *createARM64_32TargetInfo();
148 
149 struct LP64 {
150   using mach_header = llvm::MachO::mach_header_64;
151   using nlist = structs::nlist_64;
152   using segment_command = llvm::MachO::segment_command_64;
153   using section = llvm::MachO::section_64;
154   using encryption_info_command = llvm::MachO::encryption_info_command_64;
155 
156   static constexpr uint32_t magic = llvm::MachO::MH_MAGIC_64;
157   static constexpr uint32_t segmentLCType = llvm::MachO::LC_SEGMENT_64;
158   static constexpr uint32_t encryptionInfoLCType =
159       llvm::MachO::LC_ENCRYPTION_INFO_64;
160 
161   static constexpr uint64_t pageZeroSize = 1ull << 32;
162   static constexpr size_t wordSize = 8;
163 };
164 
165 struct ILP32 {
166   using mach_header = llvm::MachO::mach_header;
167   using nlist = structs::nlist;
168   using segment_command = llvm::MachO::segment_command;
169   using section = llvm::MachO::section;
170   using encryption_info_command = llvm::MachO::encryption_info_command;
171 
172   static constexpr uint32_t magic = llvm::MachO::MH_MAGIC;
173   static constexpr uint32_t segmentLCType = llvm::MachO::LC_SEGMENT;
174   static constexpr uint32_t encryptionInfoLCType =
175       llvm::MachO::LC_ENCRYPTION_INFO;
176 
177   static constexpr uint64_t pageZeroSize = 1ull << 12;
178   static constexpr size_t wordSize = 4;
179 };
180 
181 extern TargetInfo *target;
182 
183 } // namespace lld::macho
184 
185 #endif
186