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 "MachOObject.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 static constexpr char TextSegmentName[] = "__TEXT";
120 for (auto LoadCmd : MachOObj.load_commands()) {
121 LoadCommand LC;
122 switch (LoadCmd.C.cmd) {
123 case MachO::LC_CODE_SIGNATURE:
124 O.CodeSignatureCommandIndex = O.LoadCommands.size();
125 break;
126 case MachO::LC_SEGMENT:
127 // LoadCmd.Ptr might not be aligned temporarily as
128 // MachO::segment_command requires, but the segname char pointer do not
129 // have alignment restrictions.
130 if (StringRef(reinterpret_cast<const char *>(
131 LoadCmd.Ptr + offsetof(MachO::segment_command, segname))) ==
132 TextSegmentName)
133 O.TextSegmentCommandIndex = O.LoadCommands.size();
134
135 if (Expected<std::vector<std::unique_ptr<Section>>> Sections =
136 extractSections<MachO::section, MachO::segment_command>(
137 LoadCmd, MachOObj, NextSectionIndex))
138 LC.Sections = std::move(*Sections);
139 else
140 return Sections.takeError();
141 break;
142 case MachO::LC_SEGMENT_64:
143 // LoadCmd.Ptr might not be aligned temporarily as
144 // MachO::segment_command_64 requires, but the segname char pointer do
145 // not have alignment restrictions.
146 if (StringRef(reinterpret_cast<const char *>(
147 LoadCmd.Ptr + offsetof(MachO::segment_command_64, segname))) ==
148 TextSegmentName)
149 O.TextSegmentCommandIndex = O.LoadCommands.size();
150
151 if (Expected<std::vector<std::unique_ptr<Section>>> Sections =
152 extractSections<MachO::section_64, MachO::segment_command_64>(
153 LoadCmd, MachOObj, NextSectionIndex))
154 LC.Sections = std::move(*Sections);
155 else
156 return Sections.takeError();
157 break;
158 case MachO::LC_SYMTAB:
159 O.SymTabCommandIndex = O.LoadCommands.size();
160 break;
161 case MachO::LC_DYSYMTAB:
162 O.DySymTabCommandIndex = O.LoadCommands.size();
163 break;
164 case MachO::LC_DYLD_INFO:
165 case MachO::LC_DYLD_INFO_ONLY:
166 O.DyLdInfoCommandIndex = O.LoadCommands.size();
167 break;
168 case MachO::LC_DATA_IN_CODE:
169 O.DataInCodeCommandIndex = O.LoadCommands.size();
170 break;
171 case MachO::LC_LINKER_OPTIMIZATION_HINT:
172 O.LinkerOptimizationHintCommandIndex = O.LoadCommands.size();
173 break;
174 case MachO::LC_FUNCTION_STARTS:
175 O.FunctionStartsCommandIndex = O.LoadCommands.size();
176 break;
177 case MachO::LC_DYLIB_CODE_SIGN_DRS:
178 O.DylibCodeSignDRsIndex = O.LoadCommands.size();
179 break;
180 case MachO::LC_DYLD_EXPORTS_TRIE:
181 O.ExportsTrieCommandIndex = O.LoadCommands.size();
182 break;
183 case MachO::LC_DYLD_CHAINED_FIXUPS:
184 O.ChainedFixupsCommandIndex = O.LoadCommands.size();
185 break;
186 }
187 #define HANDLE_LOAD_COMMAND(LCName, LCValue, LCStruct) \
188 case MachO::LCName: \
189 memcpy((void *)&(LC.MachOLoadCommand.LCStruct##_data), LoadCmd.Ptr, \
190 sizeof(MachO::LCStruct)); \
191 if (MachOObj.isLittleEndian() != sys::IsLittleEndianHost) \
192 MachO::swapStruct(LC.MachOLoadCommand.LCStruct##_data); \
193 if (LoadCmd.C.cmdsize > sizeof(MachO::LCStruct)) \
194 LC.Payload = ArrayRef<uint8_t>( \
195 reinterpret_cast<uint8_t *>(const_cast<char *>(LoadCmd.Ptr)) + \
196 sizeof(MachO::LCStruct), \
197 LoadCmd.C.cmdsize - sizeof(MachO::LCStruct)); \
198 break;
199
200 switch (LoadCmd.C.cmd) {
201 default:
202 memcpy((void *)&(LC.MachOLoadCommand.load_command_data), LoadCmd.Ptr,
203 sizeof(MachO::load_command));
204 if (MachOObj.isLittleEndian() != sys::IsLittleEndianHost)
205 MachO::swapStruct(LC.MachOLoadCommand.load_command_data);
206 if (LoadCmd.C.cmdsize > sizeof(MachO::load_command))
207 LC.Payload = ArrayRef<uint8_t>(
208 reinterpret_cast<uint8_t *>(const_cast<char *>(LoadCmd.Ptr)) +
209 sizeof(MachO::load_command),
210 LoadCmd.C.cmdsize - sizeof(MachO::load_command));
211 break;
212 #include "llvm/BinaryFormat/MachO.def"
213 }
214 O.LoadCommands.push_back(std::move(LC));
215 }
216 return Error::success();
217 }
218
219 template <typename nlist_t>
constructSymbolEntry(StringRef StrTable,const nlist_t & nlist)220 SymbolEntry constructSymbolEntry(StringRef StrTable, const nlist_t &nlist) {
221 assert(nlist.n_strx < StrTable.size() &&
222 "n_strx exceeds the size of the string table");
223 SymbolEntry SE;
224 SE.Name = StringRef(StrTable.data() + nlist.n_strx).str();
225 SE.n_type = nlist.n_type;
226 SE.n_sect = nlist.n_sect;
227 SE.n_desc = nlist.n_desc;
228 SE.n_value = nlist.n_value;
229 return SE;
230 }
231
readSymbolTable(Object & O) const232 void MachOReader::readSymbolTable(Object &O) const {
233 StringRef StrTable = MachOObj.getStringTableData();
234 for (auto Symbol : MachOObj.symbols()) {
235 SymbolEntry SE =
236 (MachOObj.is64Bit()
237 ? constructSymbolEntry(StrTable, MachOObj.getSymbol64TableEntry(
238 Symbol.getRawDataRefImpl()))
239 : constructSymbolEntry(StrTable, MachOObj.getSymbolTableEntry(
240 Symbol.getRawDataRefImpl())));
241
242 O.SymTable.Symbols.push_back(std::make_unique<SymbolEntry>(SE));
243 }
244 }
245
setSymbolInRelocationInfo(Object & O) const246 void MachOReader::setSymbolInRelocationInfo(Object &O) const {
247 std::vector<const Section *> Sections;
248 for (auto &LC : O.LoadCommands)
249 for (std::unique_ptr<Section> &Sec : LC.Sections)
250 Sections.push_back(Sec.get());
251
252 for (LoadCommand &LC : O.LoadCommands)
253 for (std::unique_ptr<Section> &Sec : LC.Sections)
254 for (auto &Reloc : Sec->Relocations)
255 if (!Reloc.Scattered && !Reloc.IsAddend) {
256 const uint32_t SymbolNum =
257 Reloc.getPlainRelocationSymbolNum(MachOObj.isLittleEndian());
258 if (Reloc.Extern) {
259 Reloc.Symbol = O.SymTable.getSymbolByIndex(SymbolNum);
260 } else {
261 // FIXME: Refactor error handling in MachOReader and report an error
262 // if we encounter an invalid relocation.
263 assert(SymbolNum >= 1 && SymbolNum <= Sections.size() &&
264 "Invalid section index.");
265 Reloc.Sec = Sections[SymbolNum - 1];
266 }
267 }
268 }
269
readRebaseInfo(Object & O) const270 void MachOReader::readRebaseInfo(Object &O) const {
271 O.Rebases.Opcodes = MachOObj.getDyldInfoRebaseOpcodes();
272 }
273
readBindInfo(Object & O) const274 void MachOReader::readBindInfo(Object &O) const {
275 O.Binds.Opcodes = MachOObj.getDyldInfoBindOpcodes();
276 }
277
readWeakBindInfo(Object & O) const278 void MachOReader::readWeakBindInfo(Object &O) const {
279 O.WeakBinds.Opcodes = MachOObj.getDyldInfoWeakBindOpcodes();
280 }
281
readLazyBindInfo(Object & O) const282 void MachOReader::readLazyBindInfo(Object &O) const {
283 O.LazyBinds.Opcodes = MachOObj.getDyldInfoLazyBindOpcodes();
284 }
285
readExportInfo(Object & O) const286 void MachOReader::readExportInfo(Object &O) const {
287 // This information can be in LC_DYLD_INFO or in LC_DYLD_EXPORTS_TRIE
288 ArrayRef<uint8_t> Trie = MachOObj.getDyldInfoExportsTrie();
289 if (Trie.empty())
290 Trie = MachOObj.getDyldExportsTrie();
291 O.Exports.Trie = Trie;
292 }
293
readLinkData(Object & O,std::optional<size_t> LCIndex,LinkData & LD) const294 void MachOReader::readLinkData(Object &O, std::optional<size_t> LCIndex,
295 LinkData &LD) const {
296 if (!LCIndex)
297 return;
298 const MachO::linkedit_data_command &LC =
299 O.LoadCommands[*LCIndex].MachOLoadCommand.linkedit_data_command_data;
300 LD.Data =
301 arrayRefFromStringRef(MachOObj.getData().substr(LC.dataoff, LC.datasize));
302 }
303
readDataInCodeData(Object & O) const304 void MachOReader::readDataInCodeData(Object &O) const {
305 return readLinkData(O, O.DataInCodeCommandIndex, O.DataInCode);
306 }
307
readLinkerOptimizationHint(Object & O) const308 void MachOReader::readLinkerOptimizationHint(Object &O) const {
309 return readLinkData(O, O.LinkerOptimizationHintCommandIndex,
310 O.LinkerOptimizationHint);
311 }
312
readFunctionStartsData(Object & O) const313 void MachOReader::readFunctionStartsData(Object &O) const {
314 return readLinkData(O, O.FunctionStartsCommandIndex, O.FunctionStarts);
315 }
316
readDylibCodeSignDRs(Object & O) const317 void MachOReader::readDylibCodeSignDRs(Object &O) const {
318 return readLinkData(O, O.DylibCodeSignDRsIndex, O.DylibCodeSignDRs);
319 }
320
readExportsTrie(Object & O) const321 void MachOReader::readExportsTrie(Object &O) const {
322 return readLinkData(O, O.ExportsTrieCommandIndex, O.ExportsTrie);
323 }
324
readChainedFixups(Object & O) const325 void MachOReader::readChainedFixups(Object &O) const {
326 return readLinkData(O, O.ChainedFixupsCommandIndex, O.ChainedFixups);
327 }
328
readIndirectSymbolTable(Object & O) const329 void MachOReader::readIndirectSymbolTable(Object &O) const {
330 MachO::dysymtab_command DySymTab = MachOObj.getDysymtabLoadCommand();
331 constexpr uint32_t AbsOrLocalMask =
332 MachO::INDIRECT_SYMBOL_LOCAL | MachO::INDIRECT_SYMBOL_ABS;
333 for (uint32_t i = 0; i < DySymTab.nindirectsyms; ++i) {
334 uint32_t Index = MachOObj.getIndirectSymbolTableEntry(DySymTab, i);
335 if ((Index & AbsOrLocalMask) != 0)
336 O.IndirectSymTable.Symbols.emplace_back(Index, std::nullopt);
337 else
338 O.IndirectSymTable.Symbols.emplace_back(
339 Index, O.SymTable.getSymbolByIndex(Index));
340 }
341 }
342
readSwiftVersion(Object & O) const343 void MachOReader::readSwiftVersion(Object &O) const {
344 struct ObjCImageInfo {
345 uint32_t Version;
346 uint32_t Flags;
347 } ImageInfo;
348
349 for (const LoadCommand &LC : O.LoadCommands)
350 for (const std::unique_ptr<Section> &Sec : LC.Sections)
351 if (Sec->Sectname == "__objc_imageinfo" &&
352 (Sec->Segname == "__DATA" || Sec->Segname == "__DATA_CONST" ||
353 Sec->Segname == "__DATA_DIRTY") &&
354 Sec->Content.size() >= sizeof(ObjCImageInfo)) {
355 memcpy(&ImageInfo, Sec->Content.data(), sizeof(ObjCImageInfo));
356 if (MachOObj.isLittleEndian() != sys::IsLittleEndianHost) {
357 sys::swapByteOrder(ImageInfo.Version);
358 sys::swapByteOrder(ImageInfo.Flags);
359 }
360 O.SwiftVersion = (ImageInfo.Flags >> 8) & 0xff;
361 return;
362 }
363 }
364
create() const365 Expected<std::unique_ptr<Object>> MachOReader::create() const {
366 auto Obj = std::make_unique<Object>();
367 readHeader(*Obj);
368 if (Error E = readLoadCommands(*Obj))
369 return std::move(E);
370 readSymbolTable(*Obj);
371 setSymbolInRelocationInfo(*Obj);
372 readRebaseInfo(*Obj);
373 readBindInfo(*Obj);
374 readWeakBindInfo(*Obj);
375 readLazyBindInfo(*Obj);
376 readExportInfo(*Obj);
377 readDataInCodeData(*Obj);
378 readLinkerOptimizationHint(*Obj);
379 readFunctionStartsData(*Obj);
380 readDylibCodeSignDRs(*Obj);
381 readExportsTrie(*Obj);
382 readChainedFixups(*Obj);
383 readIndirectSymbolTable(*Obj);
384 readSwiftVersion(*Obj);
385 return std::move(Obj);
386 }
387