1 //===- MachOReader.cpp ------------------------------------------*- 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 #include "MachOReader.h"
10 #include "Object.h"
11 #include "llvm/BinaryFormat/MachO.h"
12 #include "llvm/Object/MachO.h"
13 #include "llvm/Support/Errc.h"
14 #include <memory>
15
16 using namespace llvm;
17 using namespace llvm::objcopy;
18 using namespace llvm::objcopy::macho;
19
readHeader(Object & O) const20 void MachOReader::readHeader(Object &O) const {
21 O.Header.Magic = MachOObj.getHeader().magic;
22 O.Header.CPUType = MachOObj.getHeader().cputype;
23 O.Header.CPUSubType = MachOObj.getHeader().cpusubtype;
24 O.Header.FileType = MachOObj.getHeader().filetype;
25 O.Header.NCmds = MachOObj.getHeader().ncmds;
26 O.Header.SizeOfCmds = MachOObj.getHeader().sizeofcmds;
27 O.Header.Flags = MachOObj.getHeader().flags;
28 }
29
30 template <typename SectionType>
constructSectionCommon(const SectionType & Sec,uint32_t Index)31 static Section constructSectionCommon(const SectionType &Sec, uint32_t Index) {
32 StringRef SegName(Sec.segname, strnlen(Sec.segname, sizeof(Sec.segname)));
33 StringRef SectName(Sec.sectname, strnlen(Sec.sectname, sizeof(Sec.sectname)));
34 Section S(SegName, SectName);
35 S.Index = Index;
36 S.Addr = Sec.addr;
37 S.Size = Sec.size;
38 S.OriginalOffset = Sec.offset;
39 S.Align = Sec.align;
40 S.RelOff = Sec.reloff;
41 S.NReloc = Sec.nreloc;
42 S.Flags = Sec.flags;
43 S.Reserved1 = Sec.reserved1;
44 S.Reserved2 = Sec.reserved2;
45 S.Reserved3 = 0;
46 return S;
47 }
48
constructSection(const MachO::section & Sec,uint32_t Index)49 Section constructSection(const MachO::section &Sec, uint32_t Index) {
50 return constructSectionCommon(Sec, Index);
51 }
52
constructSection(const MachO::section_64 & Sec,uint32_t Index)53 Section constructSection(const MachO::section_64 &Sec, uint32_t Index) {
54 Section S = constructSectionCommon(Sec, Index);
55 S.Reserved3 = Sec.reserved3;
56 return S;
57 }
58
59 template <typename SectionType, typename SegmentType>
extractSections(const object::MachOObjectFile::LoadCommandInfo & LoadCmd,const object::MachOObjectFile & MachOObj,uint32_t & NextSectionIndex)60 Expected<std::vector<std::unique_ptr<Section>>> static extractSections(
61 const object::MachOObjectFile::LoadCommandInfo &LoadCmd,
62 const object::MachOObjectFile &MachOObj, uint32_t &NextSectionIndex) {
63 std::vector<std::unique_ptr<Section>> Sections;
64 for (auto Curr = reinterpret_cast<const SectionType *>(LoadCmd.Ptr +
65 sizeof(SegmentType)),
66 End = reinterpret_cast<const SectionType *>(LoadCmd.Ptr +
67 LoadCmd.C.cmdsize);
68 Curr < End; ++Curr) {
69 SectionType Sec;
70 memcpy((void *)&Sec, Curr, sizeof(SectionType));
71
72 if (MachOObj.isLittleEndian() != sys::IsLittleEndianHost)
73 MachO::swapStruct(Sec);
74
75 Sections.push_back(
76 std::make_unique<Section>(constructSection(Sec, NextSectionIndex)));
77
78 Section &S = *Sections.back();
79
80 Expected<object::SectionRef> SecRef =
81 MachOObj.getSection(NextSectionIndex++);
82 if (!SecRef)
83 return SecRef.takeError();
84
85 Expected<ArrayRef<uint8_t>> Data =
86 MachOObj.getSectionContents(SecRef->getRawDataRefImpl());
87 if (!Data)
88 return Data.takeError();
89
90 S.Content =
91 StringRef(reinterpret_cast<const char *>(Data->data()), Data->size());
92
93 const uint32_t CPUType = MachOObj.getHeader().cputype;
94 S.Relocations.reserve(S.NReloc);
95 for (auto RI = MachOObj.section_rel_begin(SecRef->getRawDataRefImpl()),
96 RE = MachOObj.section_rel_end(SecRef->getRawDataRefImpl());
97 RI != RE; ++RI) {
98 RelocationInfo R;
99 R.Symbol = nullptr; // We'll fill this field later.
100 R.Info = MachOObj.getRelocation(RI->getRawDataRefImpl());
101 R.Scattered = MachOObj.isRelocationScattered(R.Info);
102 unsigned Type = MachOObj.getAnyRelocationType(R.Info);
103 // TODO Support CPU_TYPE_ARM.
104 R.IsAddend = !R.Scattered && (CPUType == MachO::CPU_TYPE_ARM64 &&
105 Type == MachO::ARM64_RELOC_ADDEND);
106 R.Extern = !R.Scattered && MachOObj.getPlainRelocationExternal(R.Info);
107 S.Relocations.push_back(R);
108 }
109
110 assert(S.NReloc == S.Relocations.size() &&
111 "Incorrect number of relocations");
112 }
113 return std::move(Sections);
114 }
115
readLoadCommands(Object & O) const116 Error MachOReader::readLoadCommands(Object &O) const {
117 // For MachO sections indices start from 1.
118 uint32_t NextSectionIndex = 1;
119 for (auto LoadCmd : MachOObj.load_commands()) {
120 LoadCommand LC;
121 switch (LoadCmd.C.cmd) {
122 case MachO::LC_CODE_SIGNATURE:
123 O.CodeSignatureCommandIndex = O.LoadCommands.size();
124 break;
125 case MachO::LC_SEGMENT:
126 if (Expected<std::vector<std::unique_ptr<Section>>> Sections =
127 extractSections<MachO::section, MachO::segment_command>(
128 LoadCmd, MachOObj, NextSectionIndex))
129 LC.Sections = std::move(*Sections);
130 else
131 return Sections.takeError();
132 break;
133 case MachO::LC_SEGMENT_64:
134 if (Expected<std::vector<std::unique_ptr<Section>>> Sections =
135 extractSections<MachO::section_64, MachO::segment_command_64>(
136 LoadCmd, MachOObj, NextSectionIndex))
137 LC.Sections = std::move(*Sections);
138 else
139 return Sections.takeError();
140 break;
141 case MachO::LC_SYMTAB:
142 O.SymTabCommandIndex = O.LoadCommands.size();
143 break;
144 case MachO::LC_DYSYMTAB:
145 O.DySymTabCommandIndex = O.LoadCommands.size();
146 break;
147 case MachO::LC_DYLD_INFO:
148 case MachO::LC_DYLD_INFO_ONLY:
149 O.DyLdInfoCommandIndex = O.LoadCommands.size();
150 break;
151 case MachO::LC_DATA_IN_CODE:
152 O.DataInCodeCommandIndex = O.LoadCommands.size();
153 break;
154 case MachO::LC_LINKER_OPTIMIZATION_HINT:
155 O.LinkerOptimizationHintCommandIndex = O.LoadCommands.size();
156 break;
157 case MachO::LC_FUNCTION_STARTS:
158 O.FunctionStartsCommandIndex = O.LoadCommands.size();
159 break;
160 }
161 #define HANDLE_LOAD_COMMAND(LCName, LCValue, LCStruct) \
162 case MachO::LCName: \
163 memcpy((void *)&(LC.MachOLoadCommand.LCStruct##_data), LoadCmd.Ptr, \
164 sizeof(MachO::LCStruct)); \
165 if (MachOObj.isLittleEndian() != sys::IsLittleEndianHost) \
166 MachO::swapStruct(LC.MachOLoadCommand.LCStruct##_data); \
167 if (LoadCmd.C.cmdsize > sizeof(MachO::LCStruct)) \
168 LC.Payload = ArrayRef<uint8_t>( \
169 reinterpret_cast<uint8_t *>(const_cast<char *>(LoadCmd.Ptr)) + \
170 sizeof(MachO::LCStruct), \
171 LoadCmd.C.cmdsize - sizeof(MachO::LCStruct)); \
172 break;
173
174 switch (LoadCmd.C.cmd) {
175 default:
176 memcpy((void *)&(LC.MachOLoadCommand.load_command_data), LoadCmd.Ptr,
177 sizeof(MachO::load_command));
178 if (MachOObj.isLittleEndian() != sys::IsLittleEndianHost)
179 MachO::swapStruct(LC.MachOLoadCommand.load_command_data);
180 if (LoadCmd.C.cmdsize > sizeof(MachO::load_command))
181 LC.Payload = ArrayRef<uint8_t>(
182 reinterpret_cast<uint8_t *>(const_cast<char *>(LoadCmd.Ptr)) +
183 sizeof(MachO::load_command),
184 LoadCmd.C.cmdsize - sizeof(MachO::load_command));
185 break;
186 #include "llvm/BinaryFormat/MachO.def"
187 }
188 O.LoadCommands.push_back(std::move(LC));
189 }
190 return Error::success();
191 }
192
193 template <typename nlist_t>
constructSymbolEntry(StringRef StrTable,const nlist_t & nlist)194 SymbolEntry constructSymbolEntry(StringRef StrTable, const nlist_t &nlist) {
195 assert(nlist.n_strx < StrTable.size() &&
196 "n_strx exceeds the size of the string table");
197 SymbolEntry SE;
198 SE.Name = StringRef(StrTable.data() + nlist.n_strx).str();
199 SE.n_type = nlist.n_type;
200 SE.n_sect = nlist.n_sect;
201 SE.n_desc = nlist.n_desc;
202 SE.n_value = nlist.n_value;
203 return SE;
204 }
205
readSymbolTable(Object & O) const206 void MachOReader::readSymbolTable(Object &O) const {
207 StringRef StrTable = MachOObj.getStringTableData();
208 for (auto Symbol : MachOObj.symbols()) {
209 SymbolEntry SE =
210 (MachOObj.is64Bit()
211 ? constructSymbolEntry(StrTable, MachOObj.getSymbol64TableEntry(
212 Symbol.getRawDataRefImpl()))
213 : constructSymbolEntry(StrTable, MachOObj.getSymbolTableEntry(
214 Symbol.getRawDataRefImpl())));
215
216 O.SymTable.Symbols.push_back(std::make_unique<SymbolEntry>(SE));
217 }
218 }
219
setSymbolInRelocationInfo(Object & O) const220 void MachOReader::setSymbolInRelocationInfo(Object &O) const {
221 std::vector<const Section *> Sections;
222 for (auto &LC : O.LoadCommands)
223 for (std::unique_ptr<Section> &Sec : LC.Sections)
224 Sections.push_back(Sec.get());
225
226 for (LoadCommand &LC : O.LoadCommands)
227 for (std::unique_ptr<Section> &Sec : LC.Sections)
228 for (auto &Reloc : Sec->Relocations)
229 if (!Reloc.Scattered && !Reloc.IsAddend) {
230 const uint32_t SymbolNum =
231 Reloc.getPlainRelocationSymbolNum(MachOObj.isLittleEndian());
232 if (Reloc.Extern) {
233 Reloc.Symbol = O.SymTable.getSymbolByIndex(SymbolNum);
234 } else {
235 // FIXME: Refactor error handling in MachOReader and report an error
236 // if we encounter an invalid relocation.
237 assert(SymbolNum >= 1 && SymbolNum <= Sections.size() &&
238 "Invalid section index.");
239 Reloc.Sec = Sections[SymbolNum - 1];
240 }
241 }
242 }
243
readRebaseInfo(Object & O) const244 void MachOReader::readRebaseInfo(Object &O) const {
245 O.Rebases.Opcodes = MachOObj.getDyldInfoRebaseOpcodes();
246 }
247
readBindInfo(Object & O) const248 void MachOReader::readBindInfo(Object &O) const {
249 O.Binds.Opcodes = MachOObj.getDyldInfoBindOpcodes();
250 }
251
readWeakBindInfo(Object & O) const252 void MachOReader::readWeakBindInfo(Object &O) const {
253 O.WeakBinds.Opcodes = MachOObj.getDyldInfoWeakBindOpcodes();
254 }
255
readLazyBindInfo(Object & O) const256 void MachOReader::readLazyBindInfo(Object &O) const {
257 O.LazyBinds.Opcodes = MachOObj.getDyldInfoLazyBindOpcodes();
258 }
259
readExportInfo(Object & O) const260 void MachOReader::readExportInfo(Object &O) const {
261 O.Exports.Trie = MachOObj.getDyldInfoExportsTrie();
262 }
263
readLinkData(Object & O,Optional<size_t> LCIndex,LinkData & LD) const264 void MachOReader::readLinkData(Object &O, Optional<size_t> LCIndex,
265 LinkData &LD) const {
266 if (!LCIndex)
267 return;
268 const MachO::linkedit_data_command &LC =
269 O.LoadCommands[*LCIndex].MachOLoadCommand.linkedit_data_command_data;
270 LD.Data =
271 arrayRefFromStringRef(MachOObj.getData().substr(LC.dataoff, LC.datasize));
272 }
273
readCodeSignature(Object & O) const274 void MachOReader::readCodeSignature(Object &O) const {
275 return readLinkData(O, O.CodeSignatureCommandIndex, O.CodeSignature);
276 }
277
readDataInCodeData(Object & O) const278 void MachOReader::readDataInCodeData(Object &O) const {
279 return readLinkData(O, O.DataInCodeCommandIndex, O.DataInCode);
280 }
281
readLinkerOptimizationHint(Object & O) const282 void MachOReader::readLinkerOptimizationHint(Object &O) const {
283 return readLinkData(O, O.LinkerOptimizationHintCommandIndex,
284 O.LinkerOptimizationHint);
285 }
286
readFunctionStartsData(Object & O) const287 void MachOReader::readFunctionStartsData(Object &O) const {
288 return readLinkData(O, O.FunctionStartsCommandIndex, O.FunctionStarts);
289 }
290
readIndirectSymbolTable(Object & O) const291 void MachOReader::readIndirectSymbolTable(Object &O) const {
292 MachO::dysymtab_command DySymTab = MachOObj.getDysymtabLoadCommand();
293 constexpr uint32_t AbsOrLocalMask =
294 MachO::INDIRECT_SYMBOL_LOCAL | MachO::INDIRECT_SYMBOL_ABS;
295 for (uint32_t i = 0; i < DySymTab.nindirectsyms; ++i) {
296 uint32_t Index = MachOObj.getIndirectSymbolTableEntry(DySymTab, i);
297 if ((Index & AbsOrLocalMask) != 0)
298 O.IndirectSymTable.Symbols.emplace_back(Index, None);
299 else
300 O.IndirectSymTable.Symbols.emplace_back(
301 Index, O.SymTable.getSymbolByIndex(Index));
302 }
303 }
304
readSwiftVersion(Object & O) const305 void MachOReader::readSwiftVersion(Object &O) const {
306 struct ObjCImageInfo {
307 uint32_t Version;
308 uint32_t Flags;
309 } ImageInfo;
310
311 for (const LoadCommand &LC : O.LoadCommands)
312 for (const std::unique_ptr<Section> &Sec : LC.Sections)
313 if (Sec->Sectname == "__objc_imageinfo" &&
314 (Sec->Segname == "__DATA" || Sec->Segname == "__DATA_CONST" ||
315 Sec->Segname == "__DATA_DIRTY") &&
316 Sec->Content.size() >= sizeof(ObjCImageInfo)) {
317 memcpy(&ImageInfo, Sec->Content.data(), sizeof(ObjCImageInfo));
318 if (MachOObj.isLittleEndian() != sys::IsLittleEndianHost) {
319 sys::swapByteOrder(ImageInfo.Version);
320 sys::swapByteOrder(ImageInfo.Flags);
321 }
322 O.SwiftVersion = (ImageInfo.Flags >> 8) & 0xff;
323 return;
324 }
325 }
326
create() const327 Expected<std::unique_ptr<Object>> MachOReader::create() const {
328 auto Obj = std::make_unique<Object>();
329 readHeader(*Obj);
330 if (Error E = readLoadCommands(*Obj))
331 return std::move(E);
332 readSymbolTable(*Obj);
333 setSymbolInRelocationInfo(*Obj);
334 readRebaseInfo(*Obj);
335 readBindInfo(*Obj);
336 readWeakBindInfo(*Obj);
337 readLazyBindInfo(*Obj);
338 readExportInfo(*Obj);
339 readCodeSignature(*Obj);
340 readDataInCodeData(*Obj);
341 readLinkerOptimizationHint(*Obj);
342 readFunctionStartsData(*Obj);
343 readIndirectSymbolTable(*Obj);
344 readSwiftVersion(*Obj);
345 return std::move(Obj);
346 }
347