1//===- InputFiles.cpp -----------------------------------------------------===//
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 "InputFiles.h"
10#include "COFFLinkerContext.h"
11#include "Chunks.h"
12#include "Config.h"
13#include "DebugTypes.h"
14#include "Driver.h"
15#include "SymbolTable.h"
16#include "Symbols.h"
17#include "lld/Common/DWARF.h"
18#include "llvm-c/lto.h"
19#include "llvm/ADT/SmallVector.h"
20#include "llvm/ADT/Twine.h"
21#include "llvm/BinaryFormat/COFF.h"
22#include "llvm/DebugInfo/CodeView/DebugSubsectionRecord.h"
23#include "llvm/DebugInfo/CodeView/SymbolDeserializer.h"
24#include "llvm/DebugInfo/CodeView/SymbolRecord.h"
25#include "llvm/DebugInfo/CodeView/TypeDeserializer.h"
26#include "llvm/DebugInfo/PDB/Native/NativeSession.h"
27#include "llvm/DebugInfo/PDB/Native/PDBFile.h"
28#include "llvm/LTO/LTO.h"
29#include "llvm/Object/Binary.h"
30#include "llvm/Object/COFF.h"
31#include "llvm/Support/Casting.h"
32#include "llvm/Support/Endian.h"
33#include "llvm/Support/Error.h"
34#include "llvm/Support/ErrorOr.h"
35#include "llvm/Support/FileSystem.h"
36#include "llvm/Support/Path.h"
37#include "llvm/Target/TargetOptions.h"
38#include "llvm/TargetParser/Triple.h"
39#include <cstring>
40#include <optional>
41#include <system_error>
42#include <utility>
43
44using namespace llvm;
45using namespace llvm::COFF;
46using namespace llvm::codeview;
47using namespace llvm::object;
48using namespace llvm::support::endian;
49using namespace lld;
50using namespace lld::coff;
51
52using llvm::Triple;
53using llvm::support::ulittle32_t;
54
55// Returns the last element of a path, which is supposed to be a filename.
56static StringRef getBasename(StringRef path) {
57 return sys::path::filename(path, style: sys::path::Style::windows);
58}
59
60// Returns a string in the format of "foo.obj" or "foo.obj(bar.lib)".
61std::string lld::toString(const coff::InputFile *file) {
62 if (!file)
63 return "<internal>";
64 if (file->parentName.empty() || file->kind() == coff::InputFile::ImportKind)
65 return std::string(file->getName());
66
67 return (getBasename(path: file->parentName) + "(" + getBasename(path: file->getName()) +
68 ")")
69 .str();
70}
71
72/// Checks that Source is compatible with being a weak alias to Target.
73/// If Source is Undefined and has no weak alias set, makes it a weak
74/// alias to Target.
75static void checkAndSetWeakAlias(COFFLinkerContext &ctx, InputFile *f,
76 Symbol *source, Symbol *target) {
77 if (auto *u = dyn_cast<Undefined>(Val: source)) {
78 if (u->weakAlias && u->weakAlias != target) {
79 // Weak aliases as produced by GCC are named in the form
80 // .weak.<weaksymbol>.<othersymbol>, where <othersymbol> is the name
81 // of another symbol emitted near the weak symbol.
82 // Just use the definition from the first object file that defined
83 // this weak symbol.
84 if (ctx.config.allowDuplicateWeak)
85 return;
86 ctx.symtab.reportDuplicate(existing: source, newFile: f);
87 }
88 u->weakAlias = target;
89 }
90}
91
92static bool ignoredSymbolName(StringRef name) {
93 return name == "@feat.00" || name == "@comp.id";
94}
95
96ArchiveFile::ArchiveFile(COFFLinkerContext &ctx, MemoryBufferRef m)
97 : InputFile(ctx, ArchiveKind, m) {}
98
99void ArchiveFile::parse() {
100 // Parse a MemoryBufferRef as an archive file.
101 file = CHECK(Archive::create(mb), this);
102
103 // Read the symbol table to construct Lazy objects.
104 for (const Archive::Symbol &sym : file->symbols())
105 ctx.symtab.addLazyArchive(f: this, sym);
106}
107
108// Returns a buffer pointing to a member file containing a given symbol.
109void ArchiveFile::addMember(const Archive::Symbol &sym) {
110 const Archive::Child &c =
111 CHECK(sym.getMember(),
112 "could not get the member for symbol " + toCOFFString(ctx, sym));
113
114 // Return an empty buffer if we have already returned the same buffer.
115 if (!seen.insert(V: c.getChildOffset()).second)
116 return;
117
118 ctx.driver.enqueueArchiveMember(c, sym, parentName: getName());
119}
120
121std::vector<MemoryBufferRef> lld::coff::getArchiveMembers(Archive *file) {
122 std::vector<MemoryBufferRef> v;
123 Error err = Error::success();
124 for (const Archive::Child &c : file->children(Err&: err)) {
125 MemoryBufferRef mbref =
126 CHECK(c.getMemoryBufferRef(),
127 file->getFileName() +
128 ": could not get the buffer for a child of the archive");
129 v.push_back(x: mbref);
130 }
131 if (err)
132 fatal(msg: file->getFileName() +
133 ": Archive::children failed: " + toString(E: std::move(err)));
134 return v;
135}
136
137void ObjFile::parseLazy() {
138 // Native object file.
139 std::unique_ptr<Binary> coffObjPtr = CHECK(createBinary(mb), this);
140 COFFObjectFile *coffObj = cast<COFFObjectFile>(Val: coffObjPtr.get());
141 uint32_t numSymbols = coffObj->getNumberOfSymbols();
142 for (uint32_t i = 0; i < numSymbols; ++i) {
143 COFFSymbolRef coffSym = check(e: coffObj->getSymbol(index: i));
144 if (coffSym.isUndefined() || !coffSym.isExternal() ||
145 coffSym.isWeakExternal())
146 continue;
147 StringRef name = check(e: coffObj->getSymbolName(Symbol: coffSym));
148 if (coffSym.isAbsolute() && ignoredSymbolName(name))
149 continue;
150 ctx.symtab.addLazyObject(f: this, n: name);
151 i += coffSym.getNumberOfAuxSymbols();
152 }
153}
154
155void ObjFile::parse() {
156 // Parse a memory buffer as a COFF file.
157 std::unique_ptr<Binary> bin = CHECK(createBinary(mb), this);
158
159 if (auto *obj = dyn_cast<COFFObjectFile>(Val: bin.get())) {
160 bin.release();
161 coffObj.reset(p: obj);
162 } else {
163 fatal(msg: toString(file: this) + " is not a COFF file");
164 }
165
166 // Read section and symbol tables.
167 initializeChunks();
168 initializeSymbols();
169 initializeFlags();
170 initializeDependencies();
171}
172
173const coff_section *ObjFile::getSection(uint32_t i) {
174 auto sec = coffObj->getSection(index: i);
175 if (!sec)
176 fatal(msg: "getSection failed: #" + Twine(i) + ": " + toString(E: sec.takeError()));
177 return *sec;
178}
179
180// We set SectionChunk pointers in the SparseChunks vector to this value
181// temporarily to mark comdat sections as having an unknown resolution. As we
182// walk the object file's symbol table, once we visit either a leader symbol or
183// an associative section definition together with the parent comdat's leader,
184// we set the pointer to either nullptr (to mark the section as discarded) or a
185// valid SectionChunk for that section.
186static SectionChunk *const pendingComdat = reinterpret_cast<SectionChunk *>(1);
187
188void ObjFile::initializeChunks() {
189 uint32_t numSections = coffObj->getNumberOfSections();
190 sparseChunks.resize(new_size: numSections + 1);
191 for (uint32_t i = 1; i < numSections + 1; ++i) {
192 const coff_section *sec = getSection(i);
193 if (sec->Characteristics & IMAGE_SCN_LNK_COMDAT)
194 sparseChunks[i] = pendingComdat;
195 else
196 sparseChunks[i] = readSection(sectionNumber: i, def: nullptr, leaderName: "");
197 }
198}
199
200SectionChunk *ObjFile::readSection(uint32_t sectionNumber,
201 const coff_aux_section_definition *def,
202 StringRef leaderName) {
203 const coff_section *sec = getSection(i: sectionNumber);
204
205 StringRef name;
206 if (Expected<StringRef> e = coffObj->getSectionName(Sec: sec))
207 name = *e;
208 else
209 fatal(msg: "getSectionName failed: #" + Twine(sectionNumber) + ": " +
210 toString(E: e.takeError()));
211
212 if (name == ".drectve") {
213 ArrayRef<uint8_t> data;
214 cantFail(Err: coffObj->getSectionContents(Sec: sec, Res&: data));
215 directives = StringRef((const char *)data.data(), data.size());
216 return nullptr;
217 }
218
219 if (name == ".llvm_addrsig") {
220 addrsigSec = sec;
221 return nullptr;
222 }
223
224 if (name == ".llvm.call-graph-profile") {
225 callgraphSec = sec;
226 return nullptr;
227 }
228
229 // Object files may have DWARF debug info or MS CodeView debug info
230 // (or both).
231 //
232 // DWARF sections don't need any special handling from the perspective
233 // of the linker; they are just a data section containing relocations.
234 // We can just link them to complete debug info.
235 //
236 // CodeView needs linker support. We need to interpret debug info,
237 // and then write it to a separate .pdb file.
238
239 // Ignore DWARF debug info unless requested to be included.
240 if (!ctx.config.includeDwarfChunks && name.starts_with(Prefix: ".debug_"))
241 return nullptr;
242
243 if (sec->Characteristics & llvm::COFF::IMAGE_SCN_LNK_REMOVE)
244 return nullptr;
245 auto *c = make<SectionChunk>(args: this, args&: sec);
246 if (def)
247 c->checksum = def->CheckSum;
248
249 // CodeView sections are stored to a different vector because they are not
250 // linked in the regular manner.
251 if (c->isCodeView())
252 debugChunks.push_back(x: c);
253 else if (name == ".gfids$y")
254 guardFidChunks.push_back(x: c);
255 else if (name == ".giats$y")
256 guardIATChunks.push_back(x: c);
257 else if (name == ".gljmp$y")
258 guardLJmpChunks.push_back(x: c);
259 else if (name == ".gehcont$y")
260 guardEHContChunks.push_back(x: c);
261 else if (name == ".sxdata")
262 sxDataChunks.push_back(x: c);
263 else if (ctx.config.tailMerge && sec->NumberOfRelocations == 0 &&
264 name == ".rdata" && leaderName.starts_with(Prefix: "??_C@"))
265 // COFF sections that look like string literal sections (i.e. no
266 // relocations, in .rdata, leader symbol name matches the MSVC name mangling
267 // for string literals) are subject to string tail merging.
268 MergeChunk::addSection(ctx, c);
269 else if (name == ".rsrc" || name.starts_with(Prefix: ".rsrc$"))
270 resourceChunks.push_back(x: c);
271 else
272 chunks.push_back(x: c);
273
274 return c;
275}
276
277void ObjFile::includeResourceChunks() {
278 chunks.insert(position: chunks.end(), first: resourceChunks.begin(), last: resourceChunks.end());
279}
280
281void ObjFile::readAssociativeDefinition(
282 COFFSymbolRef sym, const coff_aux_section_definition *def) {
283 readAssociativeDefinition(coffSym: sym, def, parentSection: def->getNumber(IsBigObj: sym.isBigObj()));
284}
285
286void ObjFile::readAssociativeDefinition(COFFSymbolRef sym,
287 const coff_aux_section_definition *def,
288 uint32_t parentIndex) {
289 SectionChunk *parent = sparseChunks[parentIndex];
290 int32_t sectionNumber = sym.getSectionNumber();
291
292 auto diag = [&]() {
293 StringRef name = check(e: coffObj->getSymbolName(Symbol: sym));
294
295 StringRef parentName;
296 const coff_section *parentSec = getSection(i: parentIndex);
297 if (Expected<StringRef> e = coffObj->getSectionName(Sec: parentSec))
298 parentName = *e;
299 error(msg: toString(file: this) + ": associative comdat " + name + " (sec " +
300 Twine(sectionNumber) + ") has invalid reference to section " +
301 parentName + " (sec " + Twine(parentIndex) + ")");
302 };
303
304 if (parent == pendingComdat) {
305 // This can happen if an associative comdat refers to another associative
306 // comdat that appears after it (invalid per COFF spec) or to a section
307 // without any symbols.
308 diag();
309 return;
310 }
311
312 // Check whether the parent is prevailing. If it is, so are we, and we read
313 // the section; otherwise mark it as discarded.
314 if (parent) {
315 SectionChunk *c = readSection(sectionNumber, def, leaderName: "");
316 sparseChunks[sectionNumber] = c;
317 if (c) {
318 c->selection = IMAGE_COMDAT_SELECT_ASSOCIATIVE;
319 parent->addAssociative(child: c);
320 }
321 } else {
322 sparseChunks[sectionNumber] = nullptr;
323 }
324}
325
326void ObjFile::recordPrevailingSymbolForMingw(
327 COFFSymbolRef sym, DenseMap<StringRef, uint32_t> &prevailingSectionMap) {
328 // For comdat symbols in executable sections, where this is the copy
329 // of the section chunk we actually include instead of discarding it,
330 // add the symbol to a map to allow using it for implicitly
331 // associating .[px]data$<func> sections to it.
332 // Use the suffix from the .text$<func> instead of the leader symbol
333 // name, for cases where the names differ (i386 mangling/decorations,
334 // cases where the leader is a weak symbol named .weak.func.default*).
335 int32_t sectionNumber = sym.getSectionNumber();
336 SectionChunk *sc = sparseChunks[sectionNumber];
337 if (sc && sc->getOutputCharacteristics() & IMAGE_SCN_MEM_EXECUTE) {
338 StringRef name = sc->getSectionName().split(Separator: '$').second;
339 prevailingSectionMap[name] = sectionNumber;
340 }
341}
342
343void ObjFile::maybeAssociateSEHForMingw(
344 COFFSymbolRef sym, const coff_aux_section_definition *def,
345 const DenseMap<StringRef, uint32_t> &prevailingSectionMap) {
346 StringRef name = check(e: coffObj->getSymbolName(Symbol: sym));
347 if (name.consume_front(Prefix: ".pdata$") || name.consume_front(Prefix: ".xdata$") ||
348 name.consume_front(Prefix: ".eh_frame$")) {
349 // For MinGW, treat .[px]data$<func> and .eh_frame$<func> as implicitly
350 // associative to the symbol <func>.
351 auto parentSym = prevailingSectionMap.find(Val: name);
352 if (parentSym != prevailingSectionMap.end())
353 readAssociativeDefinition(sym, def, parentIndex: parentSym->second);
354 }
355}
356
357Symbol *ObjFile::createRegular(COFFSymbolRef sym) {
358 SectionChunk *sc = sparseChunks[sym.getSectionNumber()];
359 if (sym.isExternal()) {
360 StringRef name = check(e: coffObj->getSymbolName(Symbol: sym));
361 if (sc)
362 return ctx.symtab.addRegular(f: this, n: name, s: sym.getGeneric(), c: sc,
363 sectionOffset: sym.getValue());
364 // For MinGW symbols named .weak.* that point to a discarded section,
365 // don't create an Undefined symbol. If nothing ever refers to the symbol,
366 // everything should be fine. If something actually refers to the symbol
367 // (e.g. the undefined weak alias), linking will fail due to undefined
368 // references at the end.
369 if (ctx.config.mingw && name.starts_with(Prefix: ".weak."))
370 return nullptr;
371 return ctx.symtab.addUndefined(name, f: this, isWeakAlias: false);
372 }
373 if (sc)
374 return make<DefinedRegular>(args: this, /*Name*/ args: "", /*IsCOMDAT*/ args: false,
375 /*IsExternal*/ args: false, args: sym.getGeneric(), args&: sc);
376 return nullptr;
377}
378
379void ObjFile::initializeSymbols() {
380 uint32_t numSymbols = coffObj->getNumberOfSymbols();
381 symbols.resize(new_size: numSymbols);
382
383 SmallVector<std::pair<Symbol *, uint32_t>, 8> weakAliases;
384 std::vector<uint32_t> pendingIndexes;
385 pendingIndexes.reserve(n: numSymbols);
386
387 DenseMap<StringRef, uint32_t> prevailingSectionMap;
388 std::vector<const coff_aux_section_definition *> comdatDefs(
389 coffObj->getNumberOfSections() + 1);
390
391 for (uint32_t i = 0; i < numSymbols; ++i) {
392 COFFSymbolRef coffSym = check(e: coffObj->getSymbol(index: i));
393 bool prevailingComdat;
394 if (coffSym.isUndefined()) {
395 symbols[i] = createUndefined(sym: coffSym);
396 } else if (coffSym.isWeakExternal()) {
397 symbols[i] = createUndefined(sym: coffSym);
398 uint32_t tagIndex = coffSym.getAux<coff_aux_weak_external>()->TagIndex;
399 weakAliases.emplace_back(Args&: symbols[i], Args&: tagIndex);
400 } else if (std::optional<Symbol *> optSym =
401 createDefined(sym: coffSym, comdatDefs, prevailingComdat)) {
402 symbols[i] = *optSym;
403 if (ctx.config.mingw && prevailingComdat)
404 recordPrevailingSymbolForMingw(sym: coffSym, prevailingSectionMap);
405 } else {
406 // createDefined() returns std::nullopt if a symbol belongs to a section
407 // that was pending at the point when the symbol was read. This can happen
408 // in two cases:
409 // 1) section definition symbol for a comdat leader;
410 // 2) symbol belongs to a comdat section associated with another section.
411 // In both of these cases, we can expect the section to be resolved by
412 // the time we finish visiting the remaining symbols in the symbol
413 // table. So we postpone the handling of this symbol until that time.
414 pendingIndexes.push_back(x: i);
415 }
416 i += coffSym.getNumberOfAuxSymbols();
417 }
418
419 for (uint32_t i : pendingIndexes) {
420 COFFSymbolRef sym = check(e: coffObj->getSymbol(index: i));
421 if (const coff_aux_section_definition *def = sym.getSectionDefinition()) {
422 if (def->Selection == IMAGE_COMDAT_SELECT_ASSOCIATIVE)
423 readAssociativeDefinition(sym, def);
424 else if (ctx.config.mingw)
425 maybeAssociateSEHForMingw(sym, def, prevailingSectionMap);
426 }
427 if (sparseChunks[sym.getSectionNumber()] == pendingComdat) {
428 StringRef name = check(e: coffObj->getSymbolName(Symbol: sym));
429 log(msg: "comdat section " + name +
430 " without leader and unassociated, discarding");
431 continue;
432 }
433 symbols[i] = createRegular(sym);
434 }
435
436 for (auto &kv : weakAliases) {
437 Symbol *sym = kv.first;
438 uint32_t idx = kv.second;
439 checkAndSetWeakAlias(ctx, f: this, source: sym, target: symbols[idx]);
440 }
441
442 // Free the memory used by sparseChunks now that symbol loading is finished.
443 decltype(sparseChunks)().swap(x&: sparseChunks);
444}
445
446Symbol *ObjFile::createUndefined(COFFSymbolRef sym) {
447 StringRef name = check(e: coffObj->getSymbolName(Symbol: sym));
448 return ctx.symtab.addUndefined(name, f: this, isWeakAlias: sym.isWeakExternal());
449}
450
451static const coff_aux_section_definition *findSectionDef(COFFObjectFile *obj,
452 int32_t section) {
453 uint32_t numSymbols = obj->getNumberOfSymbols();
454 for (uint32_t i = 0; i < numSymbols; ++i) {
455 COFFSymbolRef sym = check(e: obj->getSymbol(index: i));
456 if (sym.getSectionNumber() != section)
457 continue;
458 if (const coff_aux_section_definition *def = sym.getSectionDefinition())
459 return def;
460 }
461 return nullptr;
462}
463
464void ObjFile::handleComdatSelection(
465 COFFSymbolRef sym, COMDATType &selection, bool &prevailing,
466 DefinedRegular *leader,
467 const llvm::object::coff_aux_section_definition *def) {
468 if (prevailing)
469 return;
470 // There's already an existing comdat for this symbol: `Leader`.
471 // Use the comdats's selection field to determine if the new
472 // symbol in `Sym` should be discarded, produce a duplicate symbol
473 // error, etc.
474
475 SectionChunk *leaderChunk = leader->getChunk();
476 COMDATType leaderSelection = leaderChunk->selection;
477
478 assert(leader->data && "Comdat leader without SectionChunk?");
479 if (isa<BitcodeFile>(Val: leader->file)) {
480 // If the leader is only a LTO symbol, we don't know e.g. its final size
481 // yet, so we can't do the full strict comdat selection checking yet.
482 selection = leaderSelection = IMAGE_COMDAT_SELECT_ANY;
483 }
484
485 if ((selection == IMAGE_COMDAT_SELECT_ANY &&
486 leaderSelection == IMAGE_COMDAT_SELECT_LARGEST) ||
487 (selection == IMAGE_COMDAT_SELECT_LARGEST &&
488 leaderSelection == IMAGE_COMDAT_SELECT_ANY)) {
489 // cl.exe picks "any" for vftables when building with /GR- and
490 // "largest" when building with /GR. To be able to link object files
491 // compiled with each flag, "any" and "largest" are merged as "largest".
492 leaderSelection = selection = IMAGE_COMDAT_SELECT_LARGEST;
493 }
494
495 // GCCs __declspec(selectany) doesn't actually pick "any" but "same size as".
496 // Clang on the other hand picks "any". To be able to link two object files
497 // with a __declspec(selectany) declaration, one compiled with gcc and the
498 // other with clang, we merge them as proper "same size as"
499 if (ctx.config.mingw && ((selection == IMAGE_COMDAT_SELECT_ANY &&
500 leaderSelection == IMAGE_COMDAT_SELECT_SAME_SIZE) ||
501 (selection == IMAGE_COMDAT_SELECT_SAME_SIZE &&
502 leaderSelection == IMAGE_COMDAT_SELECT_ANY))) {
503 leaderSelection = selection = IMAGE_COMDAT_SELECT_SAME_SIZE;
504 }
505
506 // Other than that, comdat selections must match. This is a bit more
507 // strict than link.exe which allows merging "any" and "largest" if "any"
508 // is the first symbol the linker sees, and it allows merging "largest"
509 // with everything (!) if "largest" is the first symbol the linker sees.
510 // Making this symmetric independent of which selection is seen first
511 // seems better though.
512 // (This behavior matches ModuleLinker::getComdatResult().)
513 if (selection != leaderSelection) {
514 log(msg: ("conflicting comdat type for " + toString(ctx, b&: *leader) + ": " +
515 Twine((int)leaderSelection) + " in " + toString(file: leader->getFile()) +
516 " and " + Twine((int)selection) + " in " + toString(file: this))
517 .str());
518 ctx.symtab.reportDuplicate(existing: leader, newFile: this);
519 return;
520 }
521
522 switch (selection) {
523 case IMAGE_COMDAT_SELECT_NODUPLICATES:
524 ctx.symtab.reportDuplicate(existing: leader, newFile: this);
525 break;
526
527 case IMAGE_COMDAT_SELECT_ANY:
528 // Nothing to do.
529 break;
530
531 case IMAGE_COMDAT_SELECT_SAME_SIZE:
532 if (leaderChunk->getSize() != getSection(sym)->SizeOfRawData) {
533 if (!ctx.config.mingw) {
534 ctx.symtab.reportDuplicate(existing: leader, newFile: this);
535 } else {
536 const coff_aux_section_definition *leaderDef = nullptr;
537 if (leaderChunk->file)
538 leaderDef = findSectionDef(obj: leaderChunk->file->getCOFFObj(),
539 section: leaderChunk->getSectionNumber());
540 if (!leaderDef || leaderDef->Length != def->Length)
541 ctx.symtab.reportDuplicate(existing: leader, newFile: this);
542 }
543 }
544 break;
545
546 case IMAGE_COMDAT_SELECT_EXACT_MATCH: {
547 SectionChunk newChunk(this, getSection(sym));
548 // link.exe only compares section contents here and doesn't complain
549 // if the two comdat sections have e.g. different alignment.
550 // Match that.
551 if (leaderChunk->getContents() != newChunk.getContents())
552 ctx.symtab.reportDuplicate(existing: leader, newFile: this, newSc: &newChunk, newSectionOffset: sym.getValue());
553 break;
554 }
555
556 case IMAGE_COMDAT_SELECT_ASSOCIATIVE:
557 // createDefined() is never called for IMAGE_COMDAT_SELECT_ASSOCIATIVE.
558 // (This means lld-link doesn't produce duplicate symbol errors for
559 // associative comdats while link.exe does, but associate comdats
560 // are never extern in practice.)
561 llvm_unreachable("createDefined not called for associative comdats");
562
563 case IMAGE_COMDAT_SELECT_LARGEST:
564 if (leaderChunk->getSize() < getSection(sym)->SizeOfRawData) {
565 // Replace the existing comdat symbol with the new one.
566 StringRef name = check(e: coffObj->getSymbolName(Symbol: sym));
567 // FIXME: This is incorrect: With /opt:noref, the previous sections
568 // make it into the final executable as well. Correct handling would
569 // be to undo reading of the whole old section that's being replaced,
570 // or doing one pass that determines what the final largest comdat
571 // is for all IMAGE_COMDAT_SELECT_LARGEST comdats and then reading
572 // only the largest one.
573 replaceSymbol<DefinedRegular>(s: leader, arg: this, arg&: name, /*IsCOMDAT*/ arg: true,
574 /*IsExternal*/ arg: true, arg: sym.getGeneric(),
575 arg: nullptr);
576 prevailing = true;
577 }
578 break;
579
580 case IMAGE_COMDAT_SELECT_NEWEST:
581 llvm_unreachable("should have been rejected earlier");
582 }
583}
584
585std::optional<Symbol *> ObjFile::createDefined(
586 COFFSymbolRef sym,
587 std::vector<const coff_aux_section_definition *> &comdatDefs,
588 bool &prevailing) {
589 prevailing = false;
590 auto getName = [&]() { return check(e: coffObj->getSymbolName(Symbol: sym)); };
591
592 if (sym.isCommon()) {
593 auto *c = make<CommonChunk>(args&: sym);
594 chunks.push_back(x: c);
595 return ctx.symtab.addCommon(f: this, n: getName(), size: sym.getValue(),
596 s: sym.getGeneric(), c);
597 }
598
599 if (sym.isAbsolute()) {
600 StringRef name = getName();
601
602 if (name == "@feat.00")
603 feat00Flags = sym.getValue();
604 // Skip special symbols.
605 if (ignoredSymbolName(name))
606 return nullptr;
607
608 if (sym.isExternal())
609 return ctx.symtab.addAbsolute(n: name, s: sym);
610 return make<DefinedAbsolute>(args&: ctx, args&: name, args&: sym);
611 }
612
613 int32_t sectionNumber = sym.getSectionNumber();
614 if (sectionNumber == llvm::COFF::IMAGE_SYM_DEBUG)
615 return nullptr;
616
617 if (llvm::COFF::isReservedSectionNumber(SectionNumber: sectionNumber))
618 fatal(msg: toString(file: this) + ": " + getName() +
619 " should not refer to special section " + Twine(sectionNumber));
620
621 if ((uint32_t)sectionNumber >= sparseChunks.size())
622 fatal(msg: toString(file: this) + ": " + getName() +
623 " should not refer to non-existent section " + Twine(sectionNumber));
624
625 // Comdat handling.
626 // A comdat symbol consists of two symbol table entries.
627 // The first symbol entry has the name of the section (e.g. .text), fixed
628 // values for the other fields, and one auxiliary record.
629 // The second symbol entry has the name of the comdat symbol, called the
630 // "comdat leader".
631 // When this function is called for the first symbol entry of a comdat,
632 // it sets comdatDefs and returns std::nullopt, and when it's called for the
633 // second symbol entry it reads comdatDefs and then sets it back to nullptr.
634
635 // Handle comdat leader.
636 if (const coff_aux_section_definition *def = comdatDefs[sectionNumber]) {
637 comdatDefs[sectionNumber] = nullptr;
638 DefinedRegular *leader;
639
640 if (sym.isExternal()) {
641 std::tie(args&: leader, args&: prevailing) =
642 ctx.symtab.addComdat(f: this, n: getName(), s: sym.getGeneric());
643 } else {
644 leader = make<DefinedRegular>(args: this, /*Name*/ args: "", /*IsCOMDAT*/ args: false,
645 /*IsExternal*/ args: false, args: sym.getGeneric());
646 prevailing = true;
647 }
648
649 if (def->Selection < (int)IMAGE_COMDAT_SELECT_NODUPLICATES ||
650 // Intentionally ends at IMAGE_COMDAT_SELECT_LARGEST: link.exe
651 // doesn't understand IMAGE_COMDAT_SELECT_NEWEST either.
652 def->Selection > (int)IMAGE_COMDAT_SELECT_LARGEST) {
653 fatal(msg: "unknown comdat type " + std::to_string(val: (int)def->Selection) +
654 " for " + getName() + " in " + toString(file: this));
655 }
656 COMDATType selection = (COMDATType)def->Selection;
657
658 if (leader->isCOMDAT)
659 handleComdatSelection(sym, selection, prevailing, leader, def);
660
661 if (prevailing) {
662 SectionChunk *c = readSection(sectionNumber, def, leaderName: getName());
663 sparseChunks[sectionNumber] = c;
664 if (!c)
665 return nullptr;
666 c->sym = cast<DefinedRegular>(Val: leader);
667 c->selection = selection;
668 cast<DefinedRegular>(Val: leader)->data = &c->repl;
669 } else {
670 sparseChunks[sectionNumber] = nullptr;
671 }
672 return leader;
673 }
674
675 // Prepare to handle the comdat leader symbol by setting the section's
676 // ComdatDefs pointer if we encounter a non-associative comdat.
677 if (sparseChunks[sectionNumber] == pendingComdat) {
678 if (const coff_aux_section_definition *def = sym.getSectionDefinition()) {
679 if (def->Selection != IMAGE_COMDAT_SELECT_ASSOCIATIVE)
680 comdatDefs[sectionNumber] = def;
681 }
682 return std::nullopt;
683 }
684
685 return createRegular(sym);
686}
687
688MachineTypes ObjFile::getMachineType() {
689 if (coffObj)
690 return static_cast<MachineTypes>(coffObj->getMachine());
691 return IMAGE_FILE_MACHINE_UNKNOWN;
692}
693
694ArrayRef<uint8_t> ObjFile::getDebugSection(StringRef secName) {
695 if (SectionChunk *sec = SectionChunk::findByName(sections: debugChunks, name: secName))
696 return sec->consumeDebugMagic();
697 return {};
698}
699
700// OBJ files systematically store critical information in a .debug$S stream,
701// even if the TU was compiled with no debug info. At least two records are
702// always there. S_OBJNAME stores a 32-bit signature, which is loaded into the
703// PCHSignature member. S_COMPILE3 stores compile-time cmd-line flags. This is
704// currently used to initialize the hotPatchable member.
705void ObjFile::initializeFlags() {
706 ArrayRef<uint8_t> data = getDebugSection(secName: ".debug$S");
707 if (data.empty())
708 return;
709
710 DebugSubsectionArray subsections;
711
712 BinaryStreamReader reader(data, llvm::endianness::little);
713 ExitOnError exitOnErr;
714 exitOnErr(reader.readArray(Array&: subsections, Size: data.size()));
715
716 for (const DebugSubsectionRecord &ss : subsections) {
717 if (ss.kind() != DebugSubsectionKind::Symbols)
718 continue;
719
720 unsigned offset = 0;
721
722 // Only parse the first two records. We are only looking for S_OBJNAME
723 // and S_COMPILE3, and they usually appear at the beginning of the
724 // stream.
725 for (unsigned i = 0; i < 2; ++i) {
726 Expected<CVSymbol> sym = readSymbolFromStream(Stream: ss.getRecordData(), Offset: offset);
727 if (!sym) {
728 consumeError(Err: sym.takeError());
729 return;
730 }
731 if (sym->kind() == SymbolKind::S_COMPILE3) {
732 auto cs =
733 cantFail(ValOrErr: SymbolDeserializer::deserializeAs<Compile3Sym>(Symbol: sym.get()));
734 hotPatchable =
735 (cs.Flags & CompileSym3Flags::HotPatch) != CompileSym3Flags::None;
736 }
737 if (sym->kind() == SymbolKind::S_OBJNAME) {
738 auto objName = cantFail(ValOrErr: SymbolDeserializer::deserializeAs<ObjNameSym>(
739 Symbol: sym.get()));
740 if (objName.Signature)
741 pchSignature = objName.Signature;
742 }
743 offset += sym->length();
744 }
745 }
746}
747
748// Depending on the compilation flags, OBJs can refer to external files,
749// necessary to merge this OBJ into the final PDB. We currently support two
750// types of external files: Precomp/PCH OBJs, when compiling with /Yc and /Yu.
751// And PDB type servers, when compiling with /Zi. This function extracts these
752// dependencies and makes them available as a TpiSource interface (see
753// DebugTypes.h). Both cases only happen with cl.exe: clang-cl produces regular
754// output even with /Yc and /Yu and with /Zi.
755void ObjFile::initializeDependencies() {
756 if (!ctx.config.debug)
757 return;
758
759 bool isPCH = false;
760
761 ArrayRef<uint8_t> data = getDebugSection(secName: ".debug$P");
762 if (!data.empty())
763 isPCH = true;
764 else
765 data = getDebugSection(secName: ".debug$T");
766
767 // symbols but no types, make a plain, empty TpiSource anyway, because it
768 // simplifies adding the symbols later.
769 if (data.empty()) {
770 if (!debugChunks.empty())
771 debugTypesObj = makeTpiSource(ctx, f: this);
772 return;
773 }
774
775 // Get the first type record. It will indicate if this object uses a type
776 // server (/Zi) or a PCH file (/Yu).
777 CVTypeArray types;
778 BinaryStreamReader reader(data, llvm::endianness::little);
779 cantFail(Err: reader.readArray(Array&: types, Size: reader.getLength()));
780 CVTypeArray::Iterator firstType = types.begin();
781 if (firstType == types.end())
782 return;
783
784 // Remember the .debug$T or .debug$P section.
785 debugTypes = data;
786
787 // This object file is a PCH file that others will depend on.
788 if (isPCH) {
789 debugTypesObj = makePrecompSource(ctx, file: this);
790 return;
791 }
792
793 // This object file was compiled with /Zi. Enqueue the PDB dependency.
794 if (firstType->kind() == LF_TYPESERVER2) {
795 TypeServer2Record ts = cantFail(
796 ValOrErr: TypeDeserializer::deserializeAs<TypeServer2Record>(Data: firstType->data()));
797 debugTypesObj = makeUseTypeServerSource(ctx, file: this, ts);
798 enqueuePdbFile(path: ts.getName(), fromFile: this);
799 return;
800 }
801
802 // This object was compiled with /Yu. It uses types from another object file
803 // with a matching signature.
804 if (firstType->kind() == LF_PRECOMP) {
805 PrecompRecord precomp = cantFail(
806 ValOrErr: TypeDeserializer::deserializeAs<PrecompRecord>(Data: firstType->data()));
807 // We're better off trusting the LF_PRECOMP signature. In some cases the
808 // S_OBJNAME record doesn't contain a valid PCH signature.
809 if (precomp.Signature)
810 pchSignature = precomp.Signature;
811 debugTypesObj = makeUsePrecompSource(ctx, file: this, ts: precomp);
812 // Drop the LF_PRECOMP record from the input stream.
813 debugTypes = debugTypes.drop_front(N: firstType->RecordData.size());
814 return;
815 }
816
817 // This is a plain old object file.
818 debugTypesObj = makeTpiSource(ctx, f: this);
819}
820
821// Make a PDB path assuming the PDB is in the same folder as the OBJ
822static std::string getPdbBaseName(ObjFile *file, StringRef tSPath) {
823 StringRef localPath =
824 !file->parentName.empty() ? file->parentName : file->getName();
825 SmallString<128> path = sys::path::parent_path(path: localPath);
826
827 // Currently, type server PDBs are only created by MSVC cl, which only runs
828 // on Windows, so we can assume type server paths are Windows style.
829 sys::path::append(path,
830 a: sys::path::filename(path: tSPath, style: sys::path::Style::windows));
831 return std::string(path);
832}
833
834// The casing of the PDB path stamped in the OBJ can differ from the actual path
835// on disk. With this, we ensure to always use lowercase as a key for the
836// pdbInputFileInstances map, at least on Windows.
837static std::string normalizePdbPath(StringRef path) {
838#if defined(_WIN32)
839 return path.lower();
840#else // LINUX
841 return std::string(path);
842#endif
843}
844
845// If existing, return the actual PDB path on disk.
846static std::optional<std::string> findPdbPath(StringRef pdbPath,
847 ObjFile *dependentFile) {
848 // Ensure the file exists before anything else. In some cases, if the path
849 // points to a removable device, Driver::enqueuePath() would fail with an
850 // error (EAGAIN, "resource unavailable try again") which we want to skip
851 // silently.
852 if (llvm::sys::fs::exists(Path: pdbPath))
853 return normalizePdbPath(path: pdbPath);
854 std::string ret = getPdbBaseName(file: dependentFile, tSPath: pdbPath);
855 if (llvm::sys::fs::exists(Path: ret))
856 return normalizePdbPath(path: ret);
857 return std::nullopt;
858}
859
860PDBInputFile::PDBInputFile(COFFLinkerContext &ctx, MemoryBufferRef m)
861 : InputFile(ctx, PDBKind, m) {}
862
863PDBInputFile::~PDBInputFile() = default;
864
865PDBInputFile *PDBInputFile::findFromRecordPath(const COFFLinkerContext &ctx,
866 StringRef path,
867 ObjFile *fromFile) {
868 auto p = findPdbPath(pdbPath: path.str(), dependentFile: fromFile);
869 if (!p)
870 return nullptr;
871 auto it = ctx.pdbInputFileInstances.find(x: *p);
872 if (it != ctx.pdbInputFileInstances.end())
873 return it->second;
874 return nullptr;
875}
876
877void PDBInputFile::parse() {
878 ctx.pdbInputFileInstances[mb.getBufferIdentifier().str()] = this;
879
880 std::unique_ptr<pdb::IPDBSession> thisSession;
881 Error E = pdb::NativeSession::createFromPdb(
882 MB: MemoryBuffer::getMemBuffer(Ref: mb, RequiresNullTerminator: false), Session&: thisSession);
883 if (E) {
884 loadErrorStr.emplace(args: toString(E: std::move(E)));
885 return; // fail silently at this point - the error will be handled later,
886 // when merging the debug type stream
887 }
888
889 session.reset(p: static_cast<pdb::NativeSession *>(thisSession.release()));
890
891 pdb::PDBFile &pdbFile = session->getPDBFile();
892 auto expectedInfo = pdbFile.getPDBInfoStream();
893 // All PDB Files should have an Info stream.
894 if (!expectedInfo) {
895 loadErrorStr.emplace(args: toString(E: expectedInfo.takeError()));
896 return;
897 }
898 debugTypesObj = makeTypeServerSource(ctx, pdbInputFile: this);
899}
900
901// Used only for DWARF debug info, which is not common (except in MinGW
902// environments). This returns an optional pair of file name and line
903// number for where the variable was defined.
904std::optional<std::pair<StringRef, uint32_t>>
905ObjFile::getVariableLocation(StringRef var) {
906 if (!dwarf) {
907 dwarf = make<DWARFCache>(args: DWARFContext::create(Obj: *getCOFFObj()));
908 if (!dwarf)
909 return std::nullopt;
910 }
911 if (ctx.config.machine == I386)
912 var.consume_front(Prefix: "_");
913 std::optional<std::pair<std::string, unsigned>> ret =
914 dwarf->getVariableLoc(name: var);
915 if (!ret)
916 return std::nullopt;
917 return std::make_pair(x: saver().save(S: ret->first), y&: ret->second);
918}
919
920// Used only for DWARF debug info, which is not common (except in MinGW
921// environments).
922std::optional<DILineInfo> ObjFile::getDILineInfo(uint32_t offset,
923 uint32_t sectionIndex) {
924 if (!dwarf) {
925 dwarf = make<DWARFCache>(args: DWARFContext::create(Obj: *getCOFFObj()));
926 if (!dwarf)
927 return std::nullopt;
928 }
929
930 return dwarf->getDILineInfo(offset, sectionIndex);
931}
932
933void ObjFile::enqueuePdbFile(StringRef path, ObjFile *fromFile) {
934 auto p = findPdbPath(pdbPath: path.str(), dependentFile: fromFile);
935 if (!p)
936 return;
937 auto it = ctx.pdbInputFileInstances.emplace(args&: *p, args: nullptr);
938 if (!it.second)
939 return; // already scheduled for load
940 ctx.driver.enqueuePDB(Path: *p);
941}
942
943ImportFile::ImportFile(COFFLinkerContext &ctx, MemoryBufferRef m)
944 : InputFile(ctx, ImportKind, m), live(!ctx.config.doGC), thunkLive(live) {}
945
946void ImportFile::parse() {
947 const char *buf = mb.getBufferStart();
948 const auto *hdr = reinterpret_cast<const coff_import_header *>(buf);
949
950 // Check if the total size is valid.
951 if (mb.getBufferSize() != sizeof(*hdr) + hdr->SizeOfData)
952 fatal(msg: "broken import library");
953
954 // Read names and create an __imp_ symbol.
955 StringRef name = saver().save(S: StringRef(buf + sizeof(*hdr)));
956 StringRef impName = saver().save(S: "__imp_" + name);
957 const char *nameStart = buf + sizeof(coff_import_header) + name.size() + 1;
958 dllName = std::string(StringRef(nameStart));
959 StringRef extName;
960 switch (hdr->getNameType()) {
961 case IMPORT_ORDINAL:
962 extName = "";
963 break;
964 case IMPORT_NAME:
965 extName = name;
966 break;
967 case IMPORT_NAME_NOPREFIX:
968 extName = ltrim1(s: name, chars: "?@_");
969 break;
970 case IMPORT_NAME_UNDECORATE:
971 extName = ltrim1(s: name, chars: "?@_");
972 extName = extName.substr(Start: 0, N: extName.find(C: '@'));
973 break;
974 }
975
976 this->hdr = hdr;
977 externalName = extName;
978
979 impSym = ctx.symtab.addImportData(n: impName, f: this);
980 // If this was a duplicate, we logged an error but may continue;
981 // in this case, impSym is nullptr.
982 if (!impSym)
983 return;
984
985 if (hdr->getType() == llvm::COFF::IMPORT_CONST)
986 static_cast<void>(ctx.symtab.addImportData(n: name, f: this));
987
988 // If type is function, we need to create a thunk which jump to an
989 // address pointed by the __imp_ symbol. (This allows you to call
990 // DLL functions just like regular non-DLL functions.)
991 if (hdr->getType() == llvm::COFF::IMPORT_CODE)
992 thunkSym = ctx.symtab.addImportThunk(
993 name, s: cast_or_null<DefinedImportData>(Val: impSym), machine: hdr->Machine);
994}
995
996BitcodeFile::BitcodeFile(COFFLinkerContext &ctx, MemoryBufferRef mb,
997 StringRef archiveName, uint64_t offsetInArchive,
998 bool lazy)
999 : InputFile(ctx, BitcodeKind, mb, lazy) {
1000 std::string path = mb.getBufferIdentifier().str();
1001 if (ctx.config.thinLTOIndexOnly)
1002 path = replaceThinLTOSuffix(path: mb.getBufferIdentifier(),
1003 suffix: ctx.config.thinLTOObjectSuffixReplace.first,
1004 repl: ctx.config.thinLTOObjectSuffixReplace.second);
1005
1006 // ThinLTO assumes that all MemoryBufferRefs given to it have a unique
1007 // name. If two archives define two members with the same name, this
1008 // causes a collision which result in only one of the objects being taken
1009 // into consideration at LTO time (which very likely causes undefined
1010 // symbols later in the link stage). So we append file offset to make
1011 // filename unique.
1012 MemoryBufferRef mbref(mb.getBuffer(),
1013 saver().save(S: archiveName.empty()
1014 ? path
1015 : archiveName +
1016 sys::path::filename(path) +
1017 utostr(X: offsetInArchive)));
1018
1019 obj = check(e: lto::InputFile::create(Object: mbref));
1020}
1021
1022BitcodeFile::~BitcodeFile() = default;
1023
1024void BitcodeFile::parse() {
1025 llvm::StringSaver &saver = lld::saver();
1026
1027 std::vector<std::pair<Symbol *, bool>> comdat(obj->getComdatTable().size());
1028 for (size_t i = 0; i != obj->getComdatTable().size(); ++i)
1029 // FIXME: Check nodeduplicate
1030 comdat[i] =
1031 ctx.symtab.addComdat(f: this, n: saver.save(S: obj->getComdatTable()[i].first));
1032 for (const lto::InputFile::Symbol &objSym : obj->symbols()) {
1033 StringRef symName = saver.save(S: objSym.getName());
1034 int comdatIndex = objSym.getComdatIndex();
1035 Symbol *sym;
1036 SectionChunk *fakeSC = nullptr;
1037 if (objSym.isExecutable())
1038 fakeSC = &ctx.ltoTextSectionChunk.chunk;
1039 else
1040 fakeSC = &ctx.ltoDataSectionChunk.chunk;
1041 if (objSym.isUndefined()) {
1042 sym = ctx.symtab.addUndefined(name: symName, f: this, isWeakAlias: false);
1043 if (objSym.isWeak())
1044 sym->deferUndefined = true;
1045 // If one LTO object file references (i.e. has an undefined reference to)
1046 // a symbol with an __imp_ prefix, the LTO compilation itself sees it
1047 // as unprefixed but with a dllimport attribute instead, and doesn't
1048 // understand the relation to a concrete IR symbol with the __imp_ prefix.
1049 //
1050 // For such cases, mark the symbol as used in a regular object (i.e. the
1051 // symbol must be retained) so that the linker can associate the
1052 // references in the end. If the symbol is defined in an import library
1053 // or in a regular object file, this has no effect, but if it is defined
1054 // in another LTO object file, this makes sure it is kept, to fulfill
1055 // the reference when linking the output of the LTO compilation.
1056 if (symName.starts_with(Prefix: "__imp_"))
1057 sym->isUsedInRegularObj = true;
1058 } else if (objSym.isCommon()) {
1059 sym = ctx.symtab.addCommon(f: this, n: symName, size: objSym.getCommonSize());
1060 } else if (objSym.isWeak() && objSym.isIndirect()) {
1061 // Weak external.
1062 sym = ctx.symtab.addUndefined(name: symName, f: this, isWeakAlias: true);
1063 std::string fallback = std::string(objSym.getCOFFWeakExternalFallback());
1064 Symbol *alias = ctx.symtab.addUndefined(name: saver.save(S: fallback));
1065 checkAndSetWeakAlias(ctx, f: this, source: sym, target: alias);
1066 } else if (comdatIndex != -1) {
1067 if (symName == obj->getComdatTable()[comdatIndex].first) {
1068 sym = comdat[comdatIndex].first;
1069 if (cast<DefinedRegular>(Val: sym)->data == nullptr)
1070 cast<DefinedRegular>(Val: sym)->data = &fakeSC->repl;
1071 } else if (comdat[comdatIndex].second) {
1072 sym = ctx.symtab.addRegular(f: this, n: symName, s: nullptr, c: fakeSC);
1073 } else {
1074 sym = ctx.symtab.addUndefined(name: symName, f: this, isWeakAlias: false);
1075 }
1076 } else {
1077 sym = ctx.symtab.addRegular(f: this, n: symName, s: nullptr, c: fakeSC, sectionOffset: 0,
1078 isWeak: objSym.isWeak());
1079 }
1080 symbols.push_back(x: sym);
1081 if (objSym.isUsed())
1082 ctx.config.gcroot.push_back(x: sym);
1083 }
1084 directives = saver.save(S: obj->getCOFFLinkerOpts());
1085}
1086
1087void BitcodeFile::parseLazy() {
1088 for (const lto::InputFile::Symbol &sym : obj->symbols())
1089 if (!sym.isUndefined())
1090 ctx.symtab.addLazyObject(f: this, n: sym.getName());
1091}
1092
1093MachineTypes BitcodeFile::getMachineType() {
1094 switch (Triple(obj->getTargetTriple()).getArch()) {
1095 case Triple::x86_64:
1096 return AMD64;
1097 case Triple::x86:
1098 return I386;
1099 case Triple::arm:
1100 case Triple::thumb:
1101 return ARMNT;
1102 case Triple::aarch64:
1103 return ARM64;
1104 default:
1105 return IMAGE_FILE_MACHINE_UNKNOWN;
1106 }
1107}
1108
1109std::string lld::coff::replaceThinLTOSuffix(StringRef path, StringRef suffix,
1110 StringRef repl) {
1111 if (path.consume_back(Suffix: suffix))
1112 return (path + repl).str();
1113 return std::string(path);
1114}
1115
1116static bool isRVACode(COFFObjectFile *coffObj, uint64_t rva, InputFile *file) {
1117 for (size_t i = 1, e = coffObj->getNumberOfSections(); i <= e; i++) {
1118 const coff_section *sec = CHECK(coffObj->getSection(i), file);
1119 if (rva >= sec->VirtualAddress &&
1120 rva <= sec->VirtualAddress + sec->VirtualSize) {
1121 return (sec->Characteristics & COFF::IMAGE_SCN_CNT_CODE) != 0;
1122 }
1123 }
1124 return false;
1125}
1126
1127void DLLFile::parse() {
1128 // Parse a memory buffer as a PE-COFF executable.
1129 std::unique_ptr<Binary> bin = CHECK(createBinary(mb), this);
1130
1131 if (auto *obj = dyn_cast<COFFObjectFile>(Val: bin.get())) {
1132 bin.release();
1133 coffObj.reset(p: obj);
1134 } else {
1135 error(msg: toString(file: this) + " is not a COFF file");
1136 return;
1137 }
1138
1139 if (!coffObj->getPE32Header() && !coffObj->getPE32PlusHeader()) {
1140 error(msg: toString(file: this) + " is not a PE-COFF executable");
1141 return;
1142 }
1143
1144 for (const auto &exp : coffObj->export_directories()) {
1145 StringRef dllName, symbolName;
1146 uint32_t exportRVA;
1147 checkError(e: exp.getDllName(Result&: dllName));
1148 checkError(e: exp.getSymbolName(Result&: symbolName));
1149 checkError(e: exp.getExportRVA(Result&: exportRVA));
1150
1151 if (symbolName.empty())
1152 continue;
1153
1154 bool code = isRVACode(coffObj: coffObj.get(), rva: exportRVA, file: this);
1155
1156 Symbol *s = make<Symbol>();
1157 s->dllName = dllName;
1158 s->symbolName = symbolName;
1159 s->importType = code ? ImportType::IMPORT_CODE : ImportType::IMPORT_DATA;
1160 s->nameType = ImportNameType::IMPORT_NAME;
1161
1162 if (coffObj->getMachine() == I386) {
1163 s->symbolName = symbolName = saver().save(S: "_" + symbolName);
1164 s->nameType = ImportNameType::IMPORT_NAME_NOPREFIX;
1165 }
1166
1167 StringRef impName = saver().save(S: "__imp_" + symbolName);
1168 ctx.symtab.addLazyDLLSymbol(f: this, sym: s, n: impName);
1169 if (code)
1170 ctx.symtab.addLazyDLLSymbol(f: this, sym: s, n: symbolName);
1171 }
1172}
1173
1174MachineTypes DLLFile::getMachineType() {
1175 if (coffObj)
1176 return static_cast<MachineTypes>(coffObj->getMachine());
1177 return IMAGE_FILE_MACHINE_UNKNOWN;
1178}
1179
1180void DLLFile::makeImport(DLLFile::Symbol *s) {
1181 if (!seen.insert(key: s->symbolName).second)
1182 return;
1183
1184 size_t impSize = s->dllName.size() + s->symbolName.size() + 2; // +2 for NULs
1185 size_t size = sizeof(coff_import_header) + impSize;
1186 char *buf = bAlloc().Allocate<char>(Num: size);
1187 memset(s: buf, c: 0, n: size);
1188 char *p = buf;
1189 auto *imp = reinterpret_cast<coff_import_header *>(p);
1190 p += sizeof(*imp);
1191 imp->Sig2 = 0xFFFF;
1192 imp->Machine = coffObj->getMachine();
1193 imp->SizeOfData = impSize;
1194 imp->OrdinalHint = 0; // Only linking by name
1195 imp->TypeInfo = (s->nameType << 2) | s->importType;
1196
1197 // Write symbol name and DLL name.
1198 memcpy(dest: p, src: s->symbolName.data(), n: s->symbolName.size());
1199 p += s->symbolName.size() + 1;
1200 memcpy(dest: p, src: s->dllName.data(), n: s->dllName.size());
1201 MemoryBufferRef mbref = MemoryBufferRef(StringRef(buf, size), s->dllName);
1202 ImportFile *impFile = make<ImportFile>(args&: ctx, args&: mbref);
1203 ctx.symtab.addFile(file: impFile);
1204}
1205

source code of lld/COFF/InputFiles.cpp