Bug Summary

File:build/source/lld/COFF/Writer.cpp
Warning:line 1073, column 44
Forming reference to null pointer

Annotated Source Code

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clang -cc1 -cc1 -triple x86_64-pc-linux-gnu -analyze -disable-free -clear-ast-before-backend -disable-llvm-verifier -discard-value-names -main-file-name Writer.cpp -analyzer-checker=core -analyzer-checker=apiModeling -analyzer-checker=unix -analyzer-checker=deadcode -analyzer-checker=cplusplus -analyzer-checker=security.insecureAPI.UncheckedReturn -analyzer-checker=security.insecureAPI.getpw -analyzer-checker=security.insecureAPI.gets -analyzer-checker=security.insecureAPI.mktemp -analyzer-checker=security.insecureAPI.mkstemp -analyzer-checker=security.insecureAPI.vfork -analyzer-checker=nullability.NullPassedToNonnull -analyzer-checker=nullability.NullReturnedFromNonnull -analyzer-output plist -w -setup-static-analyzer -analyzer-config-compatibility-mode=true -mrelocation-model pic -pic-level 2 -mframe-pointer=none -fmath-errno -ffp-contract=on -fno-rounding-math -mconstructor-aliases -funwind-tables=2 -target-cpu x86-64 -tune-cpu generic -debugger-tuning=gdb -ffunction-sections -fdata-sections -fcoverage-compilation-dir=/build/source/build-llvm -resource-dir /usr/lib/llvm-16/lib/clang/16 -isystem /usr/include/libxml2 -I tools/lld/COFF -I /build/source/lld/COFF -I /build/source/lld/include -I tools/lld/include -I include -I /build/source/llvm/include -D LLD_VENDOR="Debian" -D _DEBUG -D _GNU_SOURCE -D __STDC_CONSTANT_MACROS -D __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS -D _FORTIFY_SOURCE=2 -D NDEBUG -U NDEBUG -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/10/../../../../include/x86_64-linux-gnu/c++/10 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/backward -internal-isystem /usr/lib/llvm-16/lib/clang/16/include -internal-isystem /usr/local/include -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/10/../../../../x86_64-linux-gnu/include -internal-externc-isystem /usr/include/x86_64-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -fmacro-prefix-map=/build/source/build-llvm=build-llvm -fmacro-prefix-map=/build/source/= -fcoverage-prefix-map=/build/source/build-llvm=build-llvm -fcoverage-prefix-map=/build/source/= -source-date-epoch 1673003482 -O3 -Wno-unused-command-line-argument -Wno-unused-parameter -Wwrite-strings -Wno-missing-field-initializers -Wno-long-long -Wno-maybe-uninitialized -Wno-class-memaccess -Wno-redundant-move -Wno-pessimizing-move -Wno-noexcept-type -Wno-comment -Wno-misleading-indentation -std=c++17 -fdeprecated-macro -fdebug-compilation-dir=/build/source/build-llvm -fdebug-prefix-map=/build/source/build-llvm=build-llvm -fdebug-prefix-map=/build/source/= -fdebug-prefix-map=/build/source/build-llvm=build-llvm -fdebug-prefix-map=/build/source/= -ferror-limit 19 -fvisibility-inlines-hidden -stack-protector 2 -fgnuc-version=4.2.1 -fcolor-diagnostics -vectorize-loops -vectorize-slp -analyzer-output=html -analyzer-config stable-report-filename=true -faddrsig -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o /tmp/scan-build-2023-01-06-130334-16210-1 -x c++ /build/source/lld/COFF/Writer.cpp
1//===- Writer.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 "Writer.h"
10#include "COFFLinkerContext.h"
11#include "CallGraphSort.h"
12#include "Config.h"
13#include "DLL.h"
14#include "InputFiles.h"
15#include "LLDMapFile.h"
16#include "MapFile.h"
17#include "PDB.h"
18#include "SymbolTable.h"
19#include "Symbols.h"
20#include "lld/Common/ErrorHandler.h"
21#include "lld/Common/Memory.h"
22#include "lld/Common/Timer.h"
23#include "llvm/ADT/DenseMap.h"
24#include "llvm/ADT/STLExtras.h"
25#include "llvm/ADT/StringSet.h"
26#include "llvm/BinaryFormat/COFF.h"
27#include "llvm/Support/BinaryStreamReader.h"
28#include "llvm/Support/Debug.h"
29#include "llvm/Support/Endian.h"
30#include "llvm/Support/FileOutputBuffer.h"
31#include "llvm/Support/Parallel.h"
32#include "llvm/Support/Path.h"
33#include "llvm/Support/RandomNumberGenerator.h"
34#include "llvm/Support/xxhash.h"
35#include <algorithm>
36#include <cstdio>
37#include <map>
38#include <memory>
39#include <utility>
40
41using namespace llvm;
42using namespace llvm::COFF;
43using namespace llvm::object;
44using namespace llvm::support;
45using namespace llvm::support::endian;
46using namespace lld;
47using namespace lld::coff;
48
49/* To re-generate DOSProgram:
50$ cat > /tmp/DOSProgram.asm
51org 0
52 ; Copy cs to ds.
53 push cs
54 pop ds
55 ; Point ds:dx at the $-terminated string.
56 mov dx, str
57 ; Int 21/AH=09h: Write string to standard output.
58 mov ah, 0x9
59 int 0x21
60 ; Int 21/AH=4Ch: Exit with return code (in AL).
61 mov ax, 0x4C01
62 int 0x21
63str:
64 db 'This program cannot be run in DOS mode.$'
65align 8, db 0
66$ nasm -fbin /tmp/DOSProgram.asm -o /tmp/DOSProgram.bin
67$ xxd -i /tmp/DOSProgram.bin
68*/
69static unsigned char dosProgram[] = {
70 0x0e, 0x1f, 0xba, 0x0e, 0x00, 0xb4, 0x09, 0xcd, 0x21, 0xb8, 0x01, 0x4c,
71 0xcd, 0x21, 0x54, 0x68, 0x69, 0x73, 0x20, 0x70, 0x72, 0x6f, 0x67, 0x72,
72 0x61, 0x6d, 0x20, 0x63, 0x61, 0x6e, 0x6e, 0x6f, 0x74, 0x20, 0x62, 0x65,
73 0x20, 0x72, 0x75, 0x6e, 0x20, 0x69, 0x6e, 0x20, 0x44, 0x4f, 0x53, 0x20,
74 0x6d, 0x6f, 0x64, 0x65, 0x2e, 0x24, 0x00, 0x00
75};
76static_assert(sizeof(dosProgram) % 8 == 0,
77 "DOSProgram size must be multiple of 8");
78
79static const int dosStubSize = sizeof(dos_header) + sizeof(dosProgram);
80static_assert(dosStubSize % 8 == 0, "DOSStub size must be multiple of 8");
81
82static const int numberOfDataDirectory = 16;
83
84namespace {
85
86class DebugDirectoryChunk : public NonSectionChunk {
87public:
88 DebugDirectoryChunk(COFFLinkerContext &c,
89 const std::vector<std::pair<COFF::DebugType, Chunk *>> &r,
90 bool writeRepro)
91 : records(r), writeRepro(writeRepro), ctx(c) {}
92
93 size_t getSize() const override {
94 return (records.size() + int(writeRepro)) * sizeof(debug_directory);
95 }
96
97 void writeTo(uint8_t *b) const override {
98 auto *d = reinterpret_cast<debug_directory *>(b);
99
100 for (const std::pair<COFF::DebugType, Chunk *>& record : records) {
101 Chunk *c = record.second;
102 OutputSection *os = ctx.getOutputSection(c);
103 uint64_t offs = os->getFileOff() + (c->getRVA() - os->getRVA());
104 fillEntry(d, record.first, c->getSize(), c->getRVA(), offs);
105 ++d;
106 }
107
108 if (writeRepro) {
109 // FIXME: The COFF spec allows either a 0-sized entry to just say
110 // "the timestamp field is really a hash", or a 4-byte size field
111 // followed by that many bytes containing a longer hash (with the
112 // lowest 4 bytes usually being the timestamp in little-endian order).
113 // Consider storing the full 8 bytes computed by xxHash64 here.
114 fillEntry(d, COFF::IMAGE_DEBUG_TYPE_REPRO, 0, 0, 0);
115 }
116 }
117
118 void setTimeDateStamp(uint32_t timeDateStamp) {
119 for (support::ulittle32_t *tds : timeDateStamps)
120 *tds = timeDateStamp;
121 }
122
123private:
124 void fillEntry(debug_directory *d, COFF::DebugType debugType, size_t size,
125 uint64_t rva, uint64_t offs) const {
126 d->Characteristics = 0;
127 d->TimeDateStamp = 0;
128 d->MajorVersion = 0;
129 d->MinorVersion = 0;
130 d->Type = debugType;
131 d->SizeOfData = size;
132 d->AddressOfRawData = rva;
133 d->PointerToRawData = offs;
134
135 timeDateStamps.push_back(&d->TimeDateStamp);
136 }
137
138 mutable std::vector<support::ulittle32_t *> timeDateStamps;
139 const std::vector<std::pair<COFF::DebugType, Chunk *>> &records;
140 bool writeRepro;
141
142 COFFLinkerContext &ctx;
143};
144
145class CVDebugRecordChunk : public NonSectionChunk {
146public:
147 size_t getSize() const override {
148 return sizeof(codeview::DebugInfo) + config->pdbAltPath.size() + 1;
149 }
150
151 void writeTo(uint8_t *b) const override {
152 // Save off the DebugInfo entry to backfill the file signature (build id)
153 // in Writer::writeBuildId
154 buildId = reinterpret_cast<codeview::DebugInfo *>(b);
155
156 // variable sized field (PDB Path)
157 char *p = reinterpret_cast<char *>(b + sizeof(*buildId));
158 if (!config->pdbAltPath.empty())
159 memcpy(p, config->pdbAltPath.data(), config->pdbAltPath.size());
160 p[config->pdbAltPath.size()] = '\0';
161 }
162
163 mutable codeview::DebugInfo *buildId = nullptr;
164};
165
166class ExtendedDllCharacteristicsChunk : public NonSectionChunk {
167public:
168 ExtendedDllCharacteristicsChunk(uint32_t c) : characteristics(c) {}
169
170 size_t getSize() const override { return 4; }
171
172 void writeTo(uint8_t *buf) const override { write32le(buf, characteristics); }
173
174 uint32_t characteristics = 0;
175};
176
177// PartialSection represents a group of chunks that contribute to an
178// OutputSection. Collating a collection of PartialSections of same name and
179// characteristics constitutes the OutputSection.
180class PartialSectionKey {
181public:
182 StringRef name;
183 unsigned characteristics;
184
185 bool operator<(const PartialSectionKey &other) const {
186 int c = name.compare(other.name);
187 if (c == 1)
188 return false;
189 if (c == 0)
190 return characteristics < other.characteristics;
191 return true;
192 }
193};
194
195// The writer writes a SymbolTable result to a file.
196class Writer {
197public:
198 Writer(COFFLinkerContext &c) : buffer(errorHandler().outputBuffer), ctx(c) {}
199 void run();
200
201private:
202 void createSections();
203 void createMiscChunks();
204 void createImportTables();
205 void appendImportThunks();
206 void locateImportTables();
207 void createExportTable();
208 void mergeSections();
209 void removeUnusedSections();
210 void assignAddresses();
211 void finalizeAddresses();
212 void removeEmptySections();
213 void assignOutputSectionIndices();
214 void createSymbolAndStringTable();
215 void openFile(StringRef outputPath);
216 template <typename PEHeaderTy> void writeHeader();
217 void createSEHTable();
218 void createRuntimePseudoRelocs();
219 void insertCtorDtorSymbols();
220 void createGuardCFTables();
221 void markSymbolsForRVATable(ObjFile *file,
222 ArrayRef<SectionChunk *> symIdxChunks,
223 SymbolRVASet &tableSymbols);
224 void getSymbolsFromSections(ObjFile *file,
225 ArrayRef<SectionChunk *> symIdxChunks,
226 std::vector<Symbol *> &symbols);
227 void maybeAddRVATable(SymbolRVASet tableSymbols, StringRef tableSym,
228 StringRef countSym, bool hasFlag=false);
229 void setSectionPermissions();
230 void writeSections();
231 void writeBuildId();
232 void writePEChecksum();
233 void sortSections();
234 void sortExceptionTable();
235 void sortCRTSectionChunks(std::vector<Chunk *> &chunks);
236 void addSyntheticIdata();
237 void fixPartialSectionChars(StringRef name, uint32_t chars);
238 bool fixGnuImportChunks();
239 void fixTlsAlignment();
240 PartialSection *createPartialSection(StringRef name, uint32_t outChars);
241 PartialSection *findPartialSection(StringRef name, uint32_t outChars);
242
243 std::optional<coff_symbol16> createSymbol(Defined *d);
244 size_t addEntryToStringTable(StringRef str);
245
246 OutputSection *findSection(StringRef name);
247 void addBaserels();
248 void addBaserelBlocks(std::vector<Baserel> &v);
249
250 uint32_t getSizeOfInitializedData();
251
252 void checkLoadConfig();
253 template <typename T> void checkLoadConfigGuardData(const T *loadConfig);
254
255 std::unique_ptr<FileOutputBuffer> &buffer;
256 std::map<PartialSectionKey, PartialSection *> partialSections;
257 std::vector<char> strtab;
258 std::vector<llvm::object::coff_symbol16> outputSymtab;
259 IdataContents idata;
260 Chunk *importTableStart = nullptr;
261 uint64_t importTableSize = 0;
262 Chunk *edataStart = nullptr;
263 Chunk *edataEnd = nullptr;
264 Chunk *iatStart = nullptr;
265 uint64_t iatSize = 0;
266 DelayLoadContents delayIdata;
267 EdataContents edata;
268 bool setNoSEHCharacteristic = false;
269 uint32_t tlsAlignment = 0;
270
271 DebugDirectoryChunk *debugDirectory = nullptr;
272 std::vector<std::pair<COFF::DebugType, Chunk *>> debugRecords;
273 CVDebugRecordChunk *buildId = nullptr;
274 ArrayRef<uint8_t> sectionTable;
275
276 uint64_t fileSize;
277 uint32_t pointerToSymbolTable = 0;
278 uint64_t sizeOfImage;
279 uint64_t sizeOfHeaders;
280
281 OutputSection *textSec;
282 OutputSection *rdataSec;
283 OutputSection *buildidSec;
284 OutputSection *dataSec;
285 OutputSection *pdataSec;
286 OutputSection *idataSec;
287 OutputSection *edataSec;
288 OutputSection *didatSec;
289 OutputSection *rsrcSec;
290 OutputSection *relocSec;
291 OutputSection *ctorsSec;
292 OutputSection *dtorsSec;
293
294 // The first and last .pdata sections in the output file.
295 //
296 // We need to keep track of the location of .pdata in whichever section it
297 // gets merged into so that we can sort its contents and emit a correct data
298 // directory entry for the exception table. This is also the case for some
299 // other sections (such as .edata) but because the contents of those sections
300 // are entirely linker-generated we can keep track of their locations using
301 // the chunks that the linker creates. All .pdata chunks come from input
302 // files, so we need to keep track of them separately.
303 Chunk *firstPdata = nullptr;
304 Chunk *lastPdata;
305
306 COFFLinkerContext &ctx;
307};
308} // anonymous namespace
309
310void lld::coff::writeResult(COFFLinkerContext &ctx) { Writer(ctx).run(); }
1
Calling 'Writer::run'
311
312void OutputSection::addChunk(Chunk *c) {
313 chunks.push_back(c);
314}
315
316void OutputSection::insertChunkAtStart(Chunk *c) {
317 chunks.insert(chunks.begin(), c);
318}
319
320void OutputSection::setPermissions(uint32_t c) {
321 header.Characteristics &= ~permMask;
322 header.Characteristics |= c;
323}
324
325void OutputSection::merge(OutputSection *other) {
326 chunks.insert(chunks.end(), other->chunks.begin(), other->chunks.end());
327 other->chunks.clear();
328 contribSections.insert(contribSections.end(), other->contribSections.begin(),
329 other->contribSections.end());
330 other->contribSections.clear();
331}
332
333// Write the section header to a given buffer.
334void OutputSection::writeHeaderTo(uint8_t *buf) {
335 auto *hdr = reinterpret_cast<coff_section *>(buf);
336 *hdr = header;
337 if (stringTableOff) {
338 // If name is too long, write offset into the string table as a name.
339 encodeSectionName(hdr->Name, stringTableOff);
340 } else {
341 assert(!config->debug || name.size() <= COFF::NameSize ||(static_cast <bool> (!config->debug || name.size() <=
COFF::NameSize || (hdr->Characteristics & IMAGE_SCN_MEM_DISCARDABLE
) == 0) ? void (0) : __assert_fail ("!config->debug || name.size() <= COFF::NameSize || (hdr->Characteristics & IMAGE_SCN_MEM_DISCARDABLE) == 0"
, "lld/COFF/Writer.cpp", 342, __extension__ __PRETTY_FUNCTION__
))
342 (hdr->Characteristics & IMAGE_SCN_MEM_DISCARDABLE) == 0)(static_cast <bool> (!config->debug || name.size() <=
COFF::NameSize || (hdr->Characteristics & IMAGE_SCN_MEM_DISCARDABLE
) == 0) ? void (0) : __assert_fail ("!config->debug || name.size() <= COFF::NameSize || (hdr->Characteristics & IMAGE_SCN_MEM_DISCARDABLE) == 0"
, "lld/COFF/Writer.cpp", 342, __extension__ __PRETTY_FUNCTION__
))
;
343 strncpy(hdr->Name, name.data(),
344 std::min(name.size(), (size_t)COFF::NameSize));
345 }
346}
347
348void OutputSection::addContributingPartialSection(PartialSection *sec) {
349 contribSections.push_back(sec);
350}
351
352// Check whether the target address S is in range from a relocation
353// of type relType at address P.
354static bool isInRange(uint16_t relType, uint64_t s, uint64_t p, int margin) {
355 if (config->machine == ARMNT) {
356 int64_t diff = AbsoluteDifference(s, p + 4) + margin;
357 switch (relType) {
358 case IMAGE_REL_ARM_BRANCH20T:
359 return isInt<21>(diff);
360 case IMAGE_REL_ARM_BRANCH24T:
361 case IMAGE_REL_ARM_BLX23T:
362 return isInt<25>(diff);
363 default:
364 return true;
365 }
366 } else if (config->machine == ARM64) {
367 int64_t diff = AbsoluteDifference(s, p) + margin;
368 switch (relType) {
369 case IMAGE_REL_ARM64_BRANCH26:
370 return isInt<28>(diff);
371 case IMAGE_REL_ARM64_BRANCH19:
372 return isInt<21>(diff);
373 case IMAGE_REL_ARM64_BRANCH14:
374 return isInt<16>(diff);
375 default:
376 return true;
377 }
378 } else {
379 llvm_unreachable("Unexpected architecture")::llvm::llvm_unreachable_internal("Unexpected architecture", "lld/COFF/Writer.cpp"
, 379)
;
380 }
381}
382
383// Return the last thunk for the given target if it is in range,
384// or create a new one.
385static std::pair<Defined *, bool>
386getThunk(DenseMap<uint64_t, Defined *> &lastThunks, Defined *target, uint64_t p,
387 uint16_t type, int margin) {
388 Defined *&lastThunk = lastThunks[target->getRVA()];
389 if (lastThunk && isInRange(type, lastThunk->getRVA(), p, margin))
390 return {lastThunk, false};
391 Chunk *c;
392 switch (config->machine) {
393 case ARMNT:
394 c = make<RangeExtensionThunkARM>(target);
395 break;
396 case ARM64:
397 c = make<RangeExtensionThunkARM64>(target);
398 break;
399 default:
400 llvm_unreachable("Unexpected architecture")::llvm::llvm_unreachable_internal("Unexpected architecture", "lld/COFF/Writer.cpp"
, 400)
;
401 }
402 Defined *d = make<DefinedSynthetic>("range_extension_thunk", c);
403 lastThunk = d;
404 return {d, true};
405}
406
407// This checks all relocations, and for any relocation which isn't in range
408// it adds a thunk after the section chunk that contains the relocation.
409// If the latest thunk for the specific target is in range, that is used
410// instead of creating a new thunk. All range checks are done with the
411// specified margin, to make sure that relocations that originally are in
412// range, but only barely, also get thunks - in case other added thunks makes
413// the target go out of range.
414//
415// After adding thunks, we verify that all relocations are in range (with
416// no extra margin requirements). If this failed, we restart (throwing away
417// the previously created thunks) and retry with a wider margin.
418static bool createThunks(OutputSection *os, int margin) {
419 bool addressesChanged = false;
420 DenseMap<uint64_t, Defined *> lastThunks;
421 DenseMap<std::pair<ObjFile *, Defined *>, uint32_t> thunkSymtabIndices;
422 size_t thunksSize = 0;
423 // Recheck Chunks.size() each iteration, since we can insert more
424 // elements into it.
425 for (size_t i = 0; i != os->chunks.size(); ++i) {
426 SectionChunk *sc = dyn_cast_or_null<SectionChunk>(os->chunks[i]);
427 if (!sc)
428 continue;
429 size_t thunkInsertionSpot = i + 1;
430
431 // Try to get a good enough estimate of where new thunks will be placed.
432 // Offset this by the size of the new thunks added so far, to make the
433 // estimate slightly better.
434 size_t thunkInsertionRVA = sc->getRVA() + sc->getSize() + thunksSize;
435 ObjFile *file = sc->file;
436 std::vector<std::pair<uint32_t, uint32_t>> relocReplacements;
437 ArrayRef<coff_relocation> originalRelocs =
438 file->getCOFFObj()->getRelocations(sc->header);
439 for (size_t j = 0, e = originalRelocs.size(); j < e; ++j) {
440 const coff_relocation &rel = originalRelocs[j];
441 Symbol *relocTarget = file->getSymbol(rel.SymbolTableIndex);
442
443 // The estimate of the source address P should be pretty accurate,
444 // but we don't know whether the target Symbol address should be
445 // offset by thunksSize or not (or by some of thunksSize but not all of
446 // it), giving us some uncertainty once we have added one thunk.
447 uint64_t p = sc->getRVA() + rel.VirtualAddress + thunksSize;
448
449 Defined *sym = dyn_cast_or_null<Defined>(relocTarget);
450 if (!sym)
451 continue;
452
453 uint64_t s = sym->getRVA();
454
455 if (isInRange(rel.Type, s, p, margin))
456 continue;
457
458 // If the target isn't in range, hook it up to an existing or new thunk.
459 auto [thunk, wasNew] = getThunk(lastThunks, sym, p, rel.Type, margin);
460 if (wasNew) {
461 Chunk *thunkChunk = thunk->getChunk();
462 thunkChunk->setRVA(
463 thunkInsertionRVA); // Estimate of where it will be located.
464 os->chunks.insert(os->chunks.begin() + thunkInsertionSpot, thunkChunk);
465 thunkInsertionSpot++;
466 thunksSize += thunkChunk->getSize();
467 thunkInsertionRVA += thunkChunk->getSize();
468 addressesChanged = true;
469 }
470
471 // To redirect the relocation, add a symbol to the parent object file's
472 // symbol table, and replace the relocation symbol table index with the
473 // new index.
474 auto insertion = thunkSymtabIndices.insert({{file, thunk}, ~0U});
475 uint32_t &thunkSymbolIndex = insertion.first->second;
476 if (insertion.second)
477 thunkSymbolIndex = file->addRangeThunkSymbol(thunk);
478 relocReplacements.push_back({j, thunkSymbolIndex});
479 }
480
481 // Get a writable copy of this section's relocations so they can be
482 // modified. If the relocations point into the object file, allocate new
483 // memory. Otherwise, this must be previously allocated memory that can be
484 // modified in place.
485 ArrayRef<coff_relocation> curRelocs = sc->getRelocs();
486 MutableArrayRef<coff_relocation> newRelocs;
487 if (originalRelocs.data() == curRelocs.data()) {
488 newRelocs = makeMutableArrayRef(
489 bAlloc().Allocate<coff_relocation>(originalRelocs.size()),
490 originalRelocs.size());
491 } else {
492 newRelocs = makeMutableArrayRef(
493 const_cast<coff_relocation *>(curRelocs.data()), curRelocs.size());
494 }
495
496 // Copy each relocation, but replace the symbol table indices which need
497 // thunks.
498 auto nextReplacement = relocReplacements.begin();
499 auto endReplacement = relocReplacements.end();
500 for (size_t i = 0, e = originalRelocs.size(); i != e; ++i) {
501 newRelocs[i] = originalRelocs[i];
502 if (nextReplacement != endReplacement && nextReplacement->first == i) {
503 newRelocs[i].SymbolTableIndex = nextReplacement->second;
504 ++nextReplacement;
505 }
506 }
507
508 sc->setRelocs(newRelocs);
509 }
510 return addressesChanged;
511}
512
513// Verify that all relocations are in range, with no extra margin requirements.
514static bool verifyRanges(const std::vector<Chunk *> chunks) {
515 for (Chunk *c : chunks) {
516 SectionChunk *sc = dyn_cast_or_null<SectionChunk>(c);
517 if (!sc)
518 continue;
519
520 ArrayRef<coff_relocation> relocs = sc->getRelocs();
521 for (size_t j = 0, e = relocs.size(); j < e; ++j) {
522 const coff_relocation &rel = relocs[j];
523 Symbol *relocTarget = sc->file->getSymbol(rel.SymbolTableIndex);
524
525 Defined *sym = dyn_cast_or_null<Defined>(relocTarget);
526 if (!sym)
527 continue;
528
529 uint64_t p = sc->getRVA() + rel.VirtualAddress;
530 uint64_t s = sym->getRVA();
531
532 if (!isInRange(rel.Type, s, p, 0))
533 return false;
534 }
535 }
536 return true;
537}
538
539// Assign addresses and add thunks if necessary.
540void Writer::finalizeAddresses() {
541 assignAddresses();
542 if (config->machine != ARMNT && config->machine != ARM64)
543 return;
544
545 size_t origNumChunks = 0;
546 for (OutputSection *sec : ctx.outputSections) {
547 sec->origChunks = sec->chunks;
548 origNumChunks += sec->chunks.size();
549 }
550
551 int pass = 0;
552 int margin = 1024 * 100;
553 while (true) {
554 // First check whether we need thunks at all, or if the previous pass of
555 // adding them turned out ok.
556 bool rangesOk = true;
557 size_t numChunks = 0;
558 for (OutputSection *sec : ctx.outputSections) {
559 if (!verifyRanges(sec->chunks)) {
560 rangesOk = false;
561 break;
562 }
563 numChunks += sec->chunks.size();
564 }
565 if (rangesOk) {
566 if (pass > 0)
567 log("Added " + Twine(numChunks - origNumChunks) + " thunks with " +
568 "margin " + Twine(margin) + " in " + Twine(pass) + " passes");
569 return;
570 }
571
572 if (pass >= 10)
573 fatal("adding thunks hasn't converged after " + Twine(pass) + " passes");
574
575 if (pass > 0) {
576 // If the previous pass didn't work out, reset everything back to the
577 // original conditions before retrying with a wider margin. This should
578 // ideally never happen under real circumstances.
579 for (OutputSection *sec : ctx.outputSections)
580 sec->chunks = sec->origChunks;
581 margin *= 2;
582 }
583
584 // Try adding thunks everywhere where it is needed, with a margin
585 // to avoid things going out of range due to the added thunks.
586 bool addressesChanged = false;
587 for (OutputSection *sec : ctx.outputSections)
588 addressesChanged |= createThunks(sec, margin);
589 // If the verification above thought we needed thunks, we should have
590 // added some.
591 assert(addressesChanged)(static_cast <bool> (addressesChanged) ? void (0) : __assert_fail
("addressesChanged", "lld/COFF/Writer.cpp", 591, __extension__
__PRETTY_FUNCTION__))
;
592 (void)addressesChanged;
593
594 // Recalculate the layout for the whole image (and verify the ranges at
595 // the start of the next round).
596 assignAddresses();
597
598 pass++;
599 }
600}
601
602void Writer::writePEChecksum() {
603 if (!config->writeCheckSum) {
604 return;
605 }
606
607 // https://docs.microsoft.com/en-us/windows/win32/debug/pe-format#checksum
608 uint32_t *buf = (uint32_t *)buffer->getBufferStart();
609 uint32_t size = (uint32_t)(buffer->getBufferSize());
610
611 coff_file_header *coffHeader =
612 (coff_file_header *)((uint8_t *)buf + dosStubSize + sizeof(PEMagic));
613 pe32_header *peHeader =
614 (pe32_header *)((uint8_t *)coffHeader + sizeof(coff_file_header));
615
616 uint64_t sum = 0;
617 uint32_t count = size;
618 ulittle16_t *addr = (ulittle16_t *)buf;
619
620 // The PE checksum algorithm, implemented as suggested in RFC1071
621 while (count > 1) {
622 sum += *addr++;
623 count -= 2;
624 }
625
626 // Add left-over byte, if any
627 if (count > 0)
628 sum += *(unsigned char *)addr;
629
630 // Fold 32-bit sum to 16 bits
631 while (sum >> 16) {
632 sum = (sum & 0xffff) + (sum >> 16);
633 }
634
635 sum += size;
636 peHeader->CheckSum = sum;
637}
638
639// The main function of the writer.
640void Writer::run() {
641 ScopedTimer t1(ctx.codeLayoutTimer);
642
643 createImportTables();
2
Calling 'Writer::createImportTables'
644 createSections();
645 appendImportThunks();
646 // Import thunks must be added before the Control Flow Guard tables are added.
647 createMiscChunks();
648 createExportTable();
649 mergeSections();
650 removeUnusedSections();
651 finalizeAddresses();
652 removeEmptySections();
653 assignOutputSectionIndices();
654 setSectionPermissions();
655 createSymbolAndStringTable();
656
657 if (fileSize > UINT32_MAX(4294967295U))
658 fatal("image size (" + Twine(fileSize) + ") " +
659 "exceeds maximum allowable size (" + Twine(UINT32_MAX(4294967295U)) + ")");
660
661 openFile(config->outputFile);
662 if (config->is64()) {
663 writeHeader<pe32plus_header>();
664 } else {
665 writeHeader<pe32_header>();
666 }
667 writeSections();
668 checkLoadConfig();
669 sortExceptionTable();
670
671 // Fix up the alignment in the TLS Directory's characteristic field,
672 // if a specific alignment value is needed
673 if (tlsAlignment)
674 fixTlsAlignment();
675
676 t1.stop();
677
678 if (!config->pdbPath.empty() && config->debug) {
679 assert(buildId)(static_cast <bool> (buildId) ? void (0) : __assert_fail
("buildId", "lld/COFF/Writer.cpp", 679, __extension__ __PRETTY_FUNCTION__
))
;
680 createPDB(ctx, sectionTable, buildId->buildId);
681 }
682 writeBuildId();
683
684 writeLLDMapFile(ctx);
685 writeMapFile(ctx);
686
687 writePEChecksum();
688
689 if (errorCount())
690 return;
691
692 ScopedTimer t2(ctx.outputCommitTimer);
693 if (auto e = buffer->commit())
694 fatal("failed to write output '" + buffer->getPath() +
695 "': " + toString(std::move(e)));
696}
697
698static StringRef getOutputSectionName(StringRef name) {
699 StringRef s = name.split('$').first;
700
701 // Treat a later period as a separator for MinGW, for sections like
702 // ".ctors.01234".
703 return s.substr(0, s.find('.', 1));
704}
705
706// For /order.
707static void sortBySectionOrder(std::vector<Chunk *> &chunks) {
708 auto getPriority = [](const Chunk *c) {
709 if (auto *sec = dyn_cast<SectionChunk>(c))
710 if (sec->sym)
711 return config->order.lookup(sec->sym->getName());
712 return 0;
713 };
714
715 llvm::stable_sort(chunks, [=](const Chunk *a, const Chunk *b) {
716 return getPriority(a) < getPriority(b);
717 });
718}
719
720// Change the characteristics of existing PartialSections that belong to the
721// section Name to Chars.
722void Writer::fixPartialSectionChars(StringRef name, uint32_t chars) {
723 for (auto it : partialSections) {
724 PartialSection *pSec = it.second;
725 StringRef curName = pSec->name;
726 if (!curName.consume_front(name) ||
727 (!curName.empty() && !curName.startswith("$")))
728 continue;
729 if (pSec->characteristics == chars)
730 continue;
731 PartialSection *destSec = createPartialSection(pSec->name, chars);
732 destSec->chunks.insert(destSec->chunks.end(), pSec->chunks.begin(),
733 pSec->chunks.end());
734 pSec->chunks.clear();
735 }
736}
737
738// Sort concrete section chunks from GNU import libraries.
739//
740// GNU binutils doesn't use short import files, but instead produces import
741// libraries that consist of object files, with section chunks for the .idata$*
742// sections. These are linked just as regular static libraries. Each import
743// library consists of one header object, one object file for every imported
744// symbol, and one trailer object. In order for the .idata tables/lists to
745// be formed correctly, the section chunks within each .idata$* section need
746// to be grouped by library, and sorted alphabetically within each library
747// (which makes sure the header comes first and the trailer last).
748bool Writer::fixGnuImportChunks() {
749 uint32_t rdata = IMAGE_SCN_CNT_INITIALIZED_DATA | IMAGE_SCN_MEM_READ;
750
751 // Make sure all .idata$* section chunks are mapped as RDATA in order to
752 // be sorted into the same sections as our own synthesized .idata chunks.
753 fixPartialSectionChars(".idata", rdata);
754
755 bool hasIdata = false;
756 // Sort all .idata$* chunks, grouping chunks from the same library,
757 // with alphabetical ordering of the object files within a library.
758 for (auto it : partialSections) {
759 PartialSection *pSec = it.second;
760 if (!pSec->name.startswith(".idata"))
761 continue;
762
763 if (!pSec->chunks.empty())
764 hasIdata = true;
765 llvm::stable_sort(pSec->chunks, [&](Chunk *s, Chunk *t) {
766 SectionChunk *sc1 = dyn_cast_or_null<SectionChunk>(s);
767 SectionChunk *sc2 = dyn_cast_or_null<SectionChunk>(t);
768 if (!sc1 || !sc2) {
769 // if SC1, order them ascending. If SC2 or both null,
770 // S is not less than T.
771 return sc1 != nullptr;
772 }
773 // Make a string with "libraryname/objectfile" for sorting, achieving
774 // both grouping by library and sorting of objects within a library,
775 // at once.
776 std::string key1 =
777 (sc1->file->parentName + "/" + sc1->file->getName()).str();
778 std::string key2 =
779 (sc2->file->parentName + "/" + sc2->file->getName()).str();
780 return key1 < key2;
781 });
782 }
783 return hasIdata;
784}
785
786// Add generated idata chunks, for imported symbols and DLLs, and a
787// terminator in .idata$2.
788void Writer::addSyntheticIdata() {
789 uint32_t rdata = IMAGE_SCN_CNT_INITIALIZED_DATA | IMAGE_SCN_MEM_READ;
790 idata.create();
791
792 // Add the .idata content in the right section groups, to allow
793 // chunks from other linked in object files to be grouped together.
794 // See Microsoft PE/COFF spec 5.4 for details.
795 auto add = [&](StringRef n, std::vector<Chunk *> &v) {
796 PartialSection *pSec = createPartialSection(n, rdata);
797 pSec->chunks.insert(pSec->chunks.end(), v.begin(), v.end());
798 };
799
800 // The loader assumes a specific order of data.
801 // Add each type in the correct order.
802 add(".idata$2", idata.dirs);
803 add(".idata$4", idata.lookups);
804 add(".idata$5", idata.addresses);
805 if (!idata.hints.empty())
806 add(".idata$6", idata.hints);
807 add(".idata$7", idata.dllNames);
808}
809
810// Locate the first Chunk and size of the import directory list and the
811// IAT.
812void Writer::locateImportTables() {
813 uint32_t rdata = IMAGE_SCN_CNT_INITIALIZED_DATA | IMAGE_SCN_MEM_READ;
814
815 if (PartialSection *importDirs = findPartialSection(".idata$2", rdata)) {
816 if (!importDirs->chunks.empty())
817 importTableStart = importDirs->chunks.front();
818 for (Chunk *c : importDirs->chunks)
819 importTableSize += c->getSize();
820 }
821
822 if (PartialSection *importAddresses = findPartialSection(".idata$5", rdata)) {
823 if (!importAddresses->chunks.empty())
824 iatStart = importAddresses->chunks.front();
825 for (Chunk *c : importAddresses->chunks)
826 iatSize += c->getSize();
827 }
828}
829
830// Return whether a SectionChunk's suffix (the dollar and any trailing
831// suffix) should be removed and sorted into the main suffixless
832// PartialSection.
833static bool shouldStripSectionSuffix(SectionChunk *sc, StringRef name) {
834 // On MinGW, comdat groups are formed by putting the comdat group name
835 // after the '$' in the section name. For .eh_frame$<symbol>, that must
836 // still be sorted before the .eh_frame trailer from crtend.o, thus just
837 // strip the section name trailer. For other sections, such as
838 // .tls$$<symbol> (where non-comdat .tls symbols are otherwise stored in
839 // ".tls$"), they must be strictly sorted after .tls. And for the
840 // hypothetical case of comdat .CRT$XCU, we definitely need to keep the
841 // suffix for sorting. Thus, to play it safe, only strip the suffix for
842 // the standard sections.
843 if (!config->mingw)
844 return false;
845 if (!sc || !sc->isCOMDAT())
846 return false;
847 return name.startswith(".text$") || name.startswith(".data$") ||
848 name.startswith(".rdata$") || name.startswith(".pdata$") ||
849 name.startswith(".xdata$") || name.startswith(".eh_frame$");
850}
851
852void Writer::sortSections() {
853 if (!config->callGraphProfile.empty()) {
854 DenseMap<const SectionChunk *, int> order =
855 computeCallGraphProfileOrder(ctx);
856 for (auto it : order) {
857 if (DefinedRegular *sym = it.first->sym)
858 config->order[sym->getName()] = it.second;
859 }
860 }
861 if (!config->order.empty())
862 for (auto it : partialSections)
863 sortBySectionOrder(it.second->chunks);
864}
865
866// Create output section objects and add them to OutputSections.
867void Writer::createSections() {
868 // First, create the builtin sections.
869 const uint32_t data = IMAGE_SCN_CNT_INITIALIZED_DATA;
870 const uint32_t bss = IMAGE_SCN_CNT_UNINITIALIZED_DATA;
871 const uint32_t code = IMAGE_SCN_CNT_CODE;
872 const uint32_t discardable = IMAGE_SCN_MEM_DISCARDABLE;
873 const uint32_t r = IMAGE_SCN_MEM_READ;
874 const uint32_t w = IMAGE_SCN_MEM_WRITE;
875 const uint32_t x = IMAGE_SCN_MEM_EXECUTE;
876
877 SmallDenseMap<std::pair<StringRef, uint32_t>, OutputSection *> sections;
878 auto createSection = [&](StringRef name, uint32_t outChars) {
879 OutputSection *&sec = sections[{name, outChars}];
880 if (!sec) {
881 sec = make<OutputSection>(name, outChars);
882 ctx.outputSections.push_back(sec);
883 }
884 return sec;
885 };
886
887 // Try to match the section order used by link.exe.
888 textSec = createSection(".text", code | r | x);
889 createSection(".bss", bss | r | w);
890 rdataSec = createSection(".rdata", data | r);
891 buildidSec = createSection(".buildid", data | r);
892 dataSec = createSection(".data", data | r | w);
893 pdataSec = createSection(".pdata", data | r);
894 idataSec = createSection(".idata", data | r);
895 edataSec = createSection(".edata", data | r);
896 didatSec = createSection(".didat", data | r);
897 rsrcSec = createSection(".rsrc", data | r);
898 relocSec = createSection(".reloc", data | discardable | r);
899 ctorsSec = createSection(".ctors", data | r | w);
900 dtorsSec = createSection(".dtors", data | r | w);
901
902 // Then bin chunks by name and output characteristics.
903 for (Chunk *c : ctx.symtab.getChunks()) {
904 auto *sc = dyn_cast<SectionChunk>(c);
905 if (sc && !sc->live) {
906 if (config->verbose)
907 sc->printDiscardedMessage();
908 continue;
909 }
910 StringRef name = c->getSectionName();
911 if (shouldStripSectionSuffix(sc, name))
912 name = name.split('$').first;
913
914 if (name.startswith(".tls"))
915 tlsAlignment = std::max(tlsAlignment, c->getAlignment());
916
917 PartialSection *pSec = createPartialSection(name,
918 c->getOutputCharacteristics());
919 pSec->chunks.push_back(c);
920 }
921
922 fixPartialSectionChars(".rsrc", data | r);
923 fixPartialSectionChars(".edata", data | r);
924 // Even in non MinGW cases, we might need to link against GNU import
925 // libraries.
926 bool hasIdata = fixGnuImportChunks();
927 if (!idata.empty())
928 hasIdata = true;
929
930 if (hasIdata)
931 addSyntheticIdata();
932
933 sortSections();
934
935 if (hasIdata)
936 locateImportTables();
937
938 // Then create an OutputSection for each section.
939 // '$' and all following characters in input section names are
940 // discarded when determining output section. So, .text$foo
941 // contributes to .text, for example. See PE/COFF spec 3.2.
942 for (auto it : partialSections) {
943 PartialSection *pSec = it.second;
944 StringRef name = getOutputSectionName(pSec->name);
945 uint32_t outChars = pSec->characteristics;
946
947 if (name == ".CRT") {
948 // In link.exe, there is a special case for the I386 target where .CRT
949 // sections are treated as if they have output characteristics DATA | R if
950 // their characteristics are DATA | R | W. This implements the same
951 // special case for all architectures.
952 outChars = data | r;
953
954 log("Processing section " + pSec->name + " -> " + name);
955
956 sortCRTSectionChunks(pSec->chunks);
957 }
958
959 OutputSection *sec = createSection(name, outChars);
960 for (Chunk *c : pSec->chunks)
961 sec->addChunk(c);
962
963 sec->addContributingPartialSection(pSec);
964 }
965
966 // Finally, move some output sections to the end.
967 auto sectionOrder = [&](const OutputSection *s) {
968 // Move DISCARDABLE (or non-memory-mapped) sections to the end of file
969 // because the loader cannot handle holes. Stripping can remove other
970 // discardable ones than .reloc, which is first of them (created early).
971 if (s->header.Characteristics & IMAGE_SCN_MEM_DISCARDABLE) {
972 // Move discardable sections named .debug_ to the end, after other
973 // discardable sections. Stripping only removes the sections named
974 // .debug_* - thus try to avoid leaving holes after stripping.
975 if (s->name.startswith(".debug_"))
976 return 3;
977 return 2;
978 }
979 // .rsrc should come at the end of the non-discardable sections because its
980 // size may change by the Win32 UpdateResources() function, causing
981 // subsequent sections to move (see https://crbug.com/827082).
982 if (s == rsrcSec)
983 return 1;
984 return 0;
985 };
986 llvm::stable_sort(ctx.outputSections,
987 [&](const OutputSection *s, const OutputSection *t) {
988 return sectionOrder(s) < sectionOrder(t);
989 });
990}
991
992void Writer::createMiscChunks() {
993 for (MergeChunk *p : ctx.mergeChunkInstances) {
994 if (p) {
995 p->finalizeContents();
996 rdataSec->addChunk(p);
997 }
998 }
999
1000 // Create thunks for locally-dllimported symbols.
1001 if (!ctx.symtab.localImportChunks.empty()) {
1002 for (Chunk *c : ctx.symtab.localImportChunks)
1003 rdataSec->addChunk(c);
1004 }
1005
1006 // Create Debug Information Chunks
1007 OutputSection *debugInfoSec = config->mingw ? buildidSec : rdataSec;
1008 if (config->debug || config->repro || config->cetCompat) {
1009 debugDirectory =
1010 make<DebugDirectoryChunk>(ctx, debugRecords, config->repro);
1011 debugDirectory->setAlignment(4);
1012 debugInfoSec->addChunk(debugDirectory);
1013 }
1014
1015 if (config->debug) {
1016 // Make a CVDebugRecordChunk even when /DEBUG:CV is not specified. We
1017 // output a PDB no matter what, and this chunk provides the only means of
1018 // allowing a debugger to match a PDB and an executable. So we need it even
1019 // if we're ultimately not going to write CodeView data to the PDB.
1020 buildId = make<CVDebugRecordChunk>();
1021 debugRecords.push_back({COFF::IMAGE_DEBUG_TYPE_CODEVIEW, buildId});
1022 }
1023
1024 if (config->cetCompat) {
1025 debugRecords.push_back({COFF::IMAGE_DEBUG_TYPE_EX_DLLCHARACTERISTICS,
1026 make<ExtendedDllCharacteristicsChunk>(
1027 IMAGE_DLL_CHARACTERISTICS_EX_CET_COMPAT)});
1028 }
1029
1030 // Align and add each chunk referenced by the debug data directory.
1031 for (std::pair<COFF::DebugType, Chunk *> r : debugRecords) {
1032 r.second->setAlignment(4);
1033 debugInfoSec->addChunk(r.second);
1034 }
1035
1036 // Create SEH table. x86-only.
1037 if (config->safeSEH)
1038 createSEHTable();
1039
1040 // Create /guard:cf tables if requested.
1041 if (config->guardCF != GuardCFLevel::Off)
1042 createGuardCFTables();
1043
1044 if (config->autoImport)
1045 createRuntimePseudoRelocs();
1046
1047 if (config->mingw)
1048 insertCtorDtorSymbols();
1049}
1050
1051// Create .idata section for the DLL-imported symbol table.
1052// The format of this section is inherently Windows-specific.
1053// IdataContents class abstracted away the details for us,
1054// so we just let it create chunks and add them to the section.
1055void Writer::createImportTables() {
1056 // Initialize DLLOrder so that import entries are ordered in
1057 // the same order as in the command line. (That affects DLL
1058 // initialization order, and this ordering is MSVC-compatible.)
1059 for (ImportFile *file : ctx.importFileInstances) {
1060 if (!file->live)
3
Assuming field 'live' is true
4
Taking false branch
1061 continue;
1062
1063 std::string dll = StringRef(file->dllName).lower();
1064 if (config->dllOrder.count(dll) == 0)
5
Assuming the condition is false
1065 config->dllOrder[dll] = config->dllOrder.size();
1066
1067 if (file->impSym && !isa<DefinedImportData>(file->impSym))
6
Assuming field 'impSym' is null
1068 fatal(toString(*file->impSym) + " was replaced");
1069 DefinedImportData *impSym = cast_or_null<DefinedImportData>(file->impSym);
7
Assuming null pointer is passed into cast
8
'impSym' initialized to a null pointer value
1070 if (config->delayLoads.count(StringRef(file->dllName).lower())) {
9
Assuming the condition is true
10
Taking true branch
1071 if (!file->thunkSym)
11
Assuming field 'thunkSym' is null
12
Taking true branch
1072 fatal("cannot delay-load " + toString(file) +
1073 " due to import of data: " + toString(*impSym));
13
Forming reference to null pointer
1074 delayIdata.add(impSym);
1075 } else {
1076 idata.add(impSym);
1077 }
1078 }
1079}
1080
1081void Writer::appendImportThunks() {
1082 if (ctx.importFileInstances.empty())
1083 return;
1084
1085 for (ImportFile *file : ctx.importFileInstances) {
1086 if (!file->live)
1087 continue;
1088
1089 if (!file->thunkSym)
1090 continue;
1091
1092 if (!isa<DefinedImportThunk>(file->thunkSym))
1093 fatal(toString(*file->thunkSym) + " was replaced");
1094 DefinedImportThunk *thunk = cast<DefinedImportThunk>(file->thunkSym);
1095 if (file->thunkLive)
1096 textSec->addChunk(thunk->getChunk());
1097 }
1098
1099 if (!delayIdata.empty()) {
1100 Defined *helper = cast<Defined>(config->delayLoadHelper);
1101 delayIdata.create(ctx, helper);
1102 for (Chunk *c : delayIdata.getChunks())
1103 didatSec->addChunk(c);
1104 for (Chunk *c : delayIdata.getDataChunks())
1105 dataSec->addChunk(c);
1106 for (Chunk *c : delayIdata.getCodeChunks())
1107 textSec->addChunk(c);
1108 }
1109}
1110
1111void Writer::createExportTable() {
1112 if (!edataSec->chunks.empty()) {
1113 // Allow using a custom built export table from input object files, instead
1114 // of having the linker synthesize the tables.
1115 if (config->hadExplicitExports)
1116 warn("literal .edata sections override exports");
1117 } else if (!config->exports.empty()) {
1118 for (Chunk *c : edata.chunks)
1119 edataSec->addChunk(c);
1120 }
1121 if (!edataSec->chunks.empty()) {
1122 edataStart = edataSec->chunks.front();
1123 edataEnd = edataSec->chunks.back();
1124 }
1125 // Warn on exported deleting destructor.
1126 for (auto e : config->exports)
1127 if (e.sym && e.sym->getName().startswith("??_G"))
1128 warn("export of deleting dtor: " + toString(*e.sym));
1129}
1130
1131void Writer::removeUnusedSections() {
1132 // Remove sections that we can be sure won't get content, to avoid
1133 // allocating space for their section headers.
1134 auto isUnused = [this](OutputSection *s) {
1135 if (s == relocSec)
1136 return false; // This section is populated later.
1137 // MergeChunks have zero size at this point, as their size is finalized
1138 // later. Only remove sections that have no Chunks at all.
1139 return s->chunks.empty();
1140 };
1141 llvm::erase_if(ctx.outputSections, isUnused);
1142}
1143
1144// The Windows loader doesn't seem to like empty sections,
1145// so we remove them if any.
1146void Writer::removeEmptySections() {
1147 auto isEmpty = [](OutputSection *s) { return s->getVirtualSize() == 0; };
1148 llvm::erase_if(ctx.outputSections, isEmpty);
1149}
1150
1151void Writer::assignOutputSectionIndices() {
1152 // Assign final output section indices, and assign each chunk to its output
1153 // section.
1154 uint32_t idx = 1;
1155 for (OutputSection *os : ctx.outputSections) {
1156 os->sectionIndex = idx;
1157 for (Chunk *c : os->chunks)
1158 c->setOutputSectionIdx(idx);
1159 ++idx;
1160 }
1161
1162 // Merge chunks are containers of chunks, so assign those an output section
1163 // too.
1164 for (MergeChunk *mc : ctx.mergeChunkInstances)
1165 if (mc)
1166 for (SectionChunk *sc : mc->sections)
1167 if (sc && sc->live)
1168 sc->setOutputSectionIdx(mc->getOutputSectionIdx());
1169}
1170
1171size_t Writer::addEntryToStringTable(StringRef str) {
1172 assert(str.size() > COFF::NameSize)(static_cast <bool> (str.size() > COFF::NameSize) ? void
(0) : __assert_fail ("str.size() > COFF::NameSize", "lld/COFF/Writer.cpp"
, 1172, __extension__ __PRETTY_FUNCTION__))
;
1173 size_t offsetOfEntry = strtab.size() + 4; // +4 for the size field
1174 strtab.insert(strtab.end(), str.begin(), str.end());
1175 strtab.push_back('\0');
1176 return offsetOfEntry;
1177}
1178
1179std::optional<coff_symbol16> Writer::createSymbol(Defined *def) {
1180 coff_symbol16 sym;
1181 switch (def->kind()) {
1182 case Symbol::DefinedAbsoluteKind: {
1183 auto *da = dyn_cast<DefinedAbsolute>(def);
1184 // Note: COFF symbol can only store 32-bit values, so 64-bit absolute
1185 // values will be truncated.
1186 sym.Value = da->getVA();
1187 sym.SectionNumber = IMAGE_SYM_ABSOLUTE;
1188 break;
1189 }
1190 default: {
1191 // Don't write symbols that won't be written to the output to the symbol
1192 // table.
1193 // We also try to write DefinedSynthetic as a normal symbol. Some of these
1194 // symbols do point to an actual chunk, like __safe_se_handler_table. Others
1195 // like __ImageBase are outside of sections and thus cannot be represented.
1196 Chunk *c = def->getChunk();
1197 if (!c)
1198 return std::nullopt;
1199 OutputSection *os = ctx.getOutputSection(c);
1200 if (!os)
1201 return std::nullopt;
1202
1203 sym.Value = def->getRVA() - os->getRVA();
1204 sym.SectionNumber = os->sectionIndex;
1205 break;
1206 }
1207 }
1208
1209 // Symbols that are runtime pseudo relocations don't point to the actual
1210 // symbol data itself (as they are imported), but points to the IAT entry
1211 // instead. Avoid emitting them to the symbol table, as they can confuse
1212 // debuggers.
1213 if (def->isRuntimePseudoReloc)
1214 return std::nullopt;
1215
1216 StringRef name = def->getName();
1217 if (name.size() > COFF::NameSize) {
1218 sym.Name.Offset.Zeroes = 0;
1219 sym.Name.Offset.Offset = addEntryToStringTable(name);
1220 } else {
1221 memset(sym.Name.ShortName, 0, COFF::NameSize);
1222 memcpy(sym.Name.ShortName, name.data(), name.size());
1223 }
1224
1225 if (auto *d = dyn_cast<DefinedCOFF>(def)) {
1226 COFFSymbolRef ref = d->getCOFFSymbol();
1227 sym.Type = ref.getType();
1228 sym.StorageClass = ref.getStorageClass();
1229 } else if (def->kind() == Symbol::DefinedImportThunkKind) {
1230 sym.Type = (IMAGE_SYM_DTYPE_FUNCTION << SCT_COMPLEX_TYPE_SHIFT) |
1231 IMAGE_SYM_TYPE_NULL;
1232 sym.StorageClass = IMAGE_SYM_CLASS_EXTERNAL;
1233 } else {
1234 sym.Type = IMAGE_SYM_TYPE_NULL;
1235 sym.StorageClass = IMAGE_SYM_CLASS_EXTERNAL;
1236 }
1237 sym.NumberOfAuxSymbols = 0;
1238 return sym;
1239}
1240
1241void Writer::createSymbolAndStringTable() {
1242 // PE/COFF images are limited to 8 byte section names. Longer names can be
1243 // supported by writing a non-standard string table, but this string table is
1244 // not mapped at runtime and the long names will therefore be inaccessible.
1245 // link.exe always truncates section names to 8 bytes, whereas binutils always
1246 // preserves long section names via the string table. LLD adopts a hybrid
1247 // solution where discardable sections have long names preserved and
1248 // non-discardable sections have their names truncated, to ensure that any
1249 // section which is mapped at runtime also has its name mapped at runtime.
1250 for (OutputSection *sec : ctx.outputSections) {
1251 if (sec->name.size() <= COFF::NameSize)
1252 continue;
1253 if ((sec->header.Characteristics & IMAGE_SCN_MEM_DISCARDABLE) == 0)
1254 continue;
1255 if (config->warnLongSectionNames) {
1256 warn("section name " + sec->name +
1257 " is longer than 8 characters and will use a non-standard string "
1258 "table");
1259 }
1260 sec->setStringTableOff(addEntryToStringTable(sec->name));
1261 }
1262
1263 if (config->debugDwarf || config->debugSymtab) {
1264 for (ObjFile *file : ctx.objFileInstances) {
1265 for (Symbol *b : file->getSymbols()) {
1266 auto *d = dyn_cast_or_null<Defined>(b);
1267 if (!d || d->writtenToSymtab)
1268 continue;
1269 d->writtenToSymtab = true;
1270 if (auto *dc = dyn_cast_or_null<DefinedCOFF>(d)) {
1271 COFFSymbolRef symRef = dc->getCOFFSymbol();
1272 if (symRef.isSectionDefinition() ||
1273 symRef.getStorageClass() == COFF::IMAGE_SYM_CLASS_LABEL)
1274 continue;
1275 }
1276
1277 if (std::optional<coff_symbol16> sym = createSymbol(d))
1278 outputSymtab.push_back(*sym);
1279
1280 if (auto *dthunk = dyn_cast<DefinedImportThunk>(d)) {
1281 if (!dthunk->wrappedSym->writtenToSymtab) {
1282 dthunk->wrappedSym->writtenToSymtab = true;
1283 if (std::optional<coff_symbol16> sym =
1284 createSymbol(dthunk->wrappedSym))
1285 outputSymtab.push_back(*sym);
1286 }
1287 }
1288 }
1289 }
1290 }
1291
1292 if (outputSymtab.empty() && strtab.empty())
1293 return;
1294
1295 // We position the symbol table to be adjacent to the end of the last section.
1296 uint64_t fileOff = fileSize;
1297 pointerToSymbolTable = fileOff;
1298 fileOff += outputSymtab.size() * sizeof(coff_symbol16);
1299 fileOff += 4 + strtab.size();
1300 fileSize = alignTo(fileOff, config->fileAlign);
1301}
1302
1303void Writer::mergeSections() {
1304 if (!pdataSec->chunks.empty()) {
1305 firstPdata = pdataSec->chunks.front();
1306 lastPdata = pdataSec->chunks.back();
1307 }
1308
1309 for (auto &p : config->merge) {
1310 StringRef toName = p.second;
1311 if (p.first == toName)
1312 continue;
1313 StringSet<> names;
1314 while (true) {
1315 if (!names.insert(toName).second)
1316 fatal("/merge: cycle found for section '" + p.first + "'");
1317 auto i = config->merge.find(toName);
1318 if (i == config->merge.end())
1319 break;
1320 toName = i->second;
1321 }
1322 OutputSection *from = findSection(p.first);
1323 OutputSection *to = findSection(toName);
1324 if (!from)
1325 continue;
1326 if (!to) {
1327 from->name = toName;
1328 continue;
1329 }
1330 to->merge(from);
1331 }
1332}
1333
1334// Visits all sections to assign incremental, non-overlapping RVAs and
1335// file offsets.
1336void Writer::assignAddresses() {
1337 sizeOfHeaders = dosStubSize + sizeof(PEMagic) + sizeof(coff_file_header) +
1338 sizeof(data_directory) * numberOfDataDirectory +
1339 sizeof(coff_section) * ctx.outputSections.size();
1340 sizeOfHeaders +=
1341 config->is64() ? sizeof(pe32plus_header) : sizeof(pe32_header);
1342 sizeOfHeaders = alignTo(sizeOfHeaders, config->fileAlign);
1343 fileSize = sizeOfHeaders;
1344
1345 // The first page is kept unmapped.
1346 uint64_t rva = alignTo(sizeOfHeaders, config->align);
1347
1348 for (OutputSection *sec : ctx.outputSections) {
1349 if (sec == relocSec)
1350 addBaserels();
1351 uint64_t rawSize = 0, virtualSize = 0;
1352 sec->header.VirtualAddress = rva;
1353
1354 // If /FUNCTIONPADMIN is used, functions are padded in order to create a
1355 // hotpatchable image.
1356 const bool isCodeSection =
1357 (sec->header.Characteristics & IMAGE_SCN_CNT_CODE) &&
1358 (sec->header.Characteristics & IMAGE_SCN_MEM_READ) &&
1359 (sec->header.Characteristics & IMAGE_SCN_MEM_EXECUTE);
1360 uint32_t padding = isCodeSection ? config->functionPadMin : 0;
1361
1362 for (Chunk *c : sec->chunks) {
1363 if (padding && c->isHotPatchable())
1364 virtualSize += padding;
1365 virtualSize = alignTo(virtualSize, c->getAlignment());
1366 c->setRVA(rva + virtualSize);
1367 virtualSize += c->getSize();
1368 if (c->hasData)
1369 rawSize = alignTo(virtualSize, config->fileAlign);
1370 }
1371 if (virtualSize > UINT32_MAX(4294967295U))
1372 error("section larger than 4 GiB: " + sec->name);
1373 sec->header.VirtualSize = virtualSize;
1374 sec->header.SizeOfRawData = rawSize;
1375 if (rawSize != 0)
1376 sec->header.PointerToRawData = fileSize;
1377 rva += alignTo(virtualSize, config->align);
1378 fileSize += alignTo(rawSize, config->fileAlign);
1379 }
1380 sizeOfImage = alignTo(rva, config->align);
1381
1382 // Assign addresses to sections in MergeChunks.
1383 for (MergeChunk *mc : ctx.mergeChunkInstances)
1384 if (mc)
1385 mc->assignSubsectionRVAs();
1386}
1387
1388template <typename PEHeaderTy> void Writer::writeHeader() {
1389 // Write DOS header. For backwards compatibility, the first part of a PE/COFF
1390 // executable consists of an MS-DOS MZ executable. If the executable is run
1391 // under DOS, that program gets run (usually to just print an error message).
1392 // When run under Windows, the loader looks at AddressOfNewExeHeader and uses
1393 // the PE header instead.
1394 uint8_t *buf = buffer->getBufferStart();
1395 auto *dos = reinterpret_cast<dos_header *>(buf);
1396 buf += sizeof(dos_header);
1397 dos->Magic[0] = 'M';
1398 dos->Magic[1] = 'Z';
1399 dos->UsedBytesInTheLastPage = dosStubSize % 512;
1400 dos->FileSizeInPages = divideCeil(dosStubSize, 512);
1401 dos->HeaderSizeInParagraphs = sizeof(dos_header) / 16;
1402
1403 dos->AddressOfRelocationTable = sizeof(dos_header);
1404 dos->AddressOfNewExeHeader = dosStubSize;
1405
1406 // Write DOS program.
1407 memcpy(buf, dosProgram, sizeof(dosProgram));
1408 buf += sizeof(dosProgram);
1409
1410 // Write PE magic
1411 memcpy(buf, PEMagic, sizeof(PEMagic));
1412 buf += sizeof(PEMagic);
1413
1414 // Write COFF header
1415 auto *coff = reinterpret_cast<coff_file_header *>(buf);
1416 buf += sizeof(*coff);
1417 coff->Machine = config->machine;
1418 coff->NumberOfSections = ctx.outputSections.size();
1419 coff->Characteristics = IMAGE_FILE_EXECUTABLE_IMAGE;
1420 if (config->largeAddressAware)
1421 coff->Characteristics |= IMAGE_FILE_LARGE_ADDRESS_AWARE;
1422 if (!config->is64())
1423 coff->Characteristics |= IMAGE_FILE_32BIT_MACHINE;
1424 if (config->dll)
1425 coff->Characteristics |= IMAGE_FILE_DLL;
1426 if (config->driverUponly)
1427 coff->Characteristics |= IMAGE_FILE_UP_SYSTEM_ONLY;
1428 if (!config->relocatable)
1429 coff->Characteristics |= IMAGE_FILE_RELOCS_STRIPPED;
1430 if (config->swaprunCD)
1431 coff->Characteristics |= IMAGE_FILE_REMOVABLE_RUN_FROM_SWAP;
1432 if (config->swaprunNet)
1433 coff->Characteristics |= IMAGE_FILE_NET_RUN_FROM_SWAP;
1434 coff->SizeOfOptionalHeader =
1435 sizeof(PEHeaderTy) + sizeof(data_directory) * numberOfDataDirectory;
1436
1437 // Write PE header
1438 auto *pe = reinterpret_cast<PEHeaderTy *>(buf);
1439 buf += sizeof(*pe);
1440 pe->Magic = config->is64() ? PE32Header::PE32_PLUS : PE32Header::PE32;
1441
1442 // If {Major,Minor}LinkerVersion is left at 0.0, then for some
1443 // reason signing the resulting PE file with Authenticode produces a
1444 // signature that fails to validate on Windows 7 (but is OK on 10).
1445 // Set it to 14.0, which is what VS2015 outputs, and which avoids
1446 // that problem.
1447 pe->MajorLinkerVersion = 14;
1448 pe->MinorLinkerVersion = 0;
1449
1450 pe->ImageBase = config->imageBase;
1451 pe->SectionAlignment = config->align;
1452 pe->FileAlignment = config->fileAlign;
1453 pe->MajorImageVersion = config->majorImageVersion;
1454 pe->MinorImageVersion = config->minorImageVersion;
1455 pe->MajorOperatingSystemVersion = config->majorOSVersion;
1456 pe->MinorOperatingSystemVersion = config->minorOSVersion;
1457 pe->MajorSubsystemVersion = config->majorSubsystemVersion;
1458 pe->MinorSubsystemVersion = config->minorSubsystemVersion;
1459 pe->Subsystem = config->subsystem;
1460 pe->SizeOfImage = sizeOfImage;
1461 pe->SizeOfHeaders = sizeOfHeaders;
1462 if (!config->noEntry) {
1463 Defined *entry = cast<Defined>(config->entry);
1464 pe->AddressOfEntryPoint = entry->getRVA();
1465 // Pointer to thumb code must have the LSB set, so adjust it.
1466 if (config->machine == ARMNT)
1467 pe->AddressOfEntryPoint |= 1;
1468 }
1469 pe->SizeOfStackReserve = config->stackReserve;
1470 pe->SizeOfStackCommit = config->stackCommit;
1471 pe->SizeOfHeapReserve = config->heapReserve;
1472 pe->SizeOfHeapCommit = config->heapCommit;
1473 if (config->appContainer)
1474 pe->DLLCharacteristics |= IMAGE_DLL_CHARACTERISTICS_APPCONTAINER;
1475 if (config->driverWdm)
1476 pe->DLLCharacteristics |= IMAGE_DLL_CHARACTERISTICS_WDM_DRIVER;
1477 if (config->dynamicBase)
1478 pe->DLLCharacteristics |= IMAGE_DLL_CHARACTERISTICS_DYNAMIC_BASE;
1479 if (config->highEntropyVA)
1480 pe->DLLCharacteristics |= IMAGE_DLL_CHARACTERISTICS_HIGH_ENTROPY_VA;
1481 if (!config->allowBind)
1482 pe->DLLCharacteristics |= IMAGE_DLL_CHARACTERISTICS_NO_BIND;
1483 if (config->nxCompat)
1484 pe->DLLCharacteristics |= IMAGE_DLL_CHARACTERISTICS_NX_COMPAT;
1485 if (!config->allowIsolation)
1486 pe->DLLCharacteristics |= IMAGE_DLL_CHARACTERISTICS_NO_ISOLATION;
1487 if (config->guardCF != GuardCFLevel::Off)
1488 pe->DLLCharacteristics |= IMAGE_DLL_CHARACTERISTICS_GUARD_CF;
1489 if (config->integrityCheck)
1490 pe->DLLCharacteristics |= IMAGE_DLL_CHARACTERISTICS_FORCE_INTEGRITY;
1491 if (setNoSEHCharacteristic || config->noSEH)
1492 pe->DLLCharacteristics |= IMAGE_DLL_CHARACTERISTICS_NO_SEH;
1493 if (config->terminalServerAware)
1494 pe->DLLCharacteristics |= IMAGE_DLL_CHARACTERISTICS_TERMINAL_SERVER_AWARE;
1495 pe->NumberOfRvaAndSize = numberOfDataDirectory;
1496 if (textSec->getVirtualSize()) {
1497 pe->BaseOfCode = textSec->getRVA();
1498 pe->SizeOfCode = textSec->getRawSize();
1499 }
1500 pe->SizeOfInitializedData = getSizeOfInitializedData();
1501
1502 // Write data directory
1503 auto *dir = reinterpret_cast<data_directory *>(buf);
1504 buf += sizeof(*dir) * numberOfDataDirectory;
1505 if (edataStart) {
1506 dir[EXPORT_TABLE].RelativeVirtualAddress = edataStart->getRVA();
1507 dir[EXPORT_TABLE].Size =
1508 edataEnd->getRVA() + edataEnd->getSize() - edataStart->getRVA();
1509 }
1510 if (importTableStart) {
1511 dir[IMPORT_TABLE].RelativeVirtualAddress = importTableStart->getRVA();
1512 dir[IMPORT_TABLE].Size = importTableSize;
1513 }
1514 if (iatStart) {
1515 dir[IAT].RelativeVirtualAddress = iatStart->getRVA();
1516 dir[IAT].Size = iatSize;
1517 }
1518 if (rsrcSec->getVirtualSize()) {
1519 dir[RESOURCE_TABLE].RelativeVirtualAddress = rsrcSec->getRVA();
1520 dir[RESOURCE_TABLE].Size = rsrcSec->getVirtualSize();
1521 }
1522 if (firstPdata) {
1523 dir[EXCEPTION_TABLE].RelativeVirtualAddress = firstPdata->getRVA();
1524 dir[EXCEPTION_TABLE].Size =
1525 lastPdata->getRVA() + lastPdata->getSize() - firstPdata->getRVA();
1526 }
1527 if (relocSec->getVirtualSize()) {
1528 dir[BASE_RELOCATION_TABLE].RelativeVirtualAddress = relocSec->getRVA();
1529 dir[BASE_RELOCATION_TABLE].Size = relocSec->getVirtualSize();
1530 }
1531 if (Symbol *sym = ctx.symtab.findUnderscore("_tls_used")) {
1532 if (Defined *b = dyn_cast<Defined>(sym)) {
1533 dir[TLS_TABLE].RelativeVirtualAddress = b->getRVA();
1534 dir[TLS_TABLE].Size = config->is64()
1535 ? sizeof(object::coff_tls_directory64)
1536 : sizeof(object::coff_tls_directory32);
1537 }
1538 }
1539 if (debugDirectory) {
1540 dir[DEBUG_DIRECTORY].RelativeVirtualAddress = debugDirectory->getRVA();
1541 dir[DEBUG_DIRECTORY].Size = debugDirectory->getSize();
1542 }
1543 if (Symbol *sym = ctx.symtab.findUnderscore("_load_config_used")) {
1544 if (auto *b = dyn_cast<DefinedRegular>(sym)) {
1545 SectionChunk *sc = b->getChunk();
1546 assert(b->getRVA() >= sc->getRVA())(static_cast <bool> (b->getRVA() >= sc->getRVA
()) ? void (0) : __assert_fail ("b->getRVA() >= sc->getRVA()"
, "lld/COFF/Writer.cpp", 1546, __extension__ __PRETTY_FUNCTION__
))
;
1547 uint64_t offsetInChunk = b->getRVA() - sc->getRVA();
1548 if (!sc->hasData || offsetInChunk + 4 > sc->getSize())
1549 fatal("_load_config_used is malformed");
1550
1551 ArrayRef<uint8_t> secContents = sc->getContents();
1552 uint32_t loadConfigSize =
1553 *reinterpret_cast<const ulittle32_t *>(&secContents[offsetInChunk]);
1554 if (offsetInChunk + loadConfigSize > sc->getSize())
1555 fatal("_load_config_used is too large");
1556 dir[LOAD_CONFIG_TABLE].RelativeVirtualAddress = b->getRVA();
1557 dir[LOAD_CONFIG_TABLE].Size = loadConfigSize;
1558 }
1559 }
1560 if (!delayIdata.empty()) {
1561 dir[DELAY_IMPORT_DESCRIPTOR].RelativeVirtualAddress =
1562 delayIdata.getDirRVA();
1563 dir[DELAY_IMPORT_DESCRIPTOR].Size = delayIdata.getDirSize();
1564 }
1565
1566 // Write section table
1567 for (OutputSection *sec : ctx.outputSections) {
1568 sec->writeHeaderTo(buf);
1569 buf += sizeof(coff_section);
1570 }
1571 sectionTable = ArrayRef<uint8_t>(
1572 buf - ctx.outputSections.size() * sizeof(coff_section), buf);
1573
1574 if (outputSymtab.empty() && strtab.empty())
1575 return;
1576
1577 coff->PointerToSymbolTable = pointerToSymbolTable;
1578 uint32_t numberOfSymbols = outputSymtab.size();
1579 coff->NumberOfSymbols = numberOfSymbols;
1580 auto *symbolTable = reinterpret_cast<coff_symbol16 *>(
1581 buffer->getBufferStart() + coff->PointerToSymbolTable);
1582 for (size_t i = 0; i != numberOfSymbols; ++i)
1583 symbolTable[i] = outputSymtab[i];
1584 // Create the string table, it follows immediately after the symbol table.
1585 // The first 4 bytes is length including itself.
1586 buf = reinterpret_cast<uint8_t *>(&symbolTable[numberOfSymbols]);
1587 write32le(buf, strtab.size() + 4);
1588 if (!strtab.empty())
1589 memcpy(buf + 4, strtab.data(), strtab.size());
1590}
1591
1592void Writer::openFile(StringRef path) {
1593 buffer = CHECK(check2((FileOutputBuffer::create(path, fileSize, FileOutputBuffer
::F_executable)), [&] { return toString("failed to open "
+ path); })
1594 FileOutputBuffer::create(path, fileSize, FileOutputBuffer::F_executable),check2((FileOutputBuffer::create(path, fileSize, FileOutputBuffer
::F_executable)), [&] { return toString("failed to open "
+ path); })
1595 "failed to open " + path)check2((FileOutputBuffer::create(path, fileSize, FileOutputBuffer
::F_executable)), [&] { return toString("failed to open "
+ path); })
;
1596}
1597
1598void Writer::createSEHTable() {
1599 SymbolRVASet handlers;
1600 for (ObjFile *file : ctx.objFileInstances) {
1601 if (!file->hasSafeSEH())
1602 error("/safeseh: " + file->getName() + " is not compatible with SEH");
1603 markSymbolsForRVATable(file, file->getSXDataChunks(), handlers);
1604 }
1605
1606 // Set the "no SEH" characteristic if there really were no handlers, or if
1607 // there is no load config object to point to the table of handlers.
1608 setNoSEHCharacteristic =
1609 handlers.empty() || !ctx.symtab.findUnderscore("_load_config_used");
1610
1611 maybeAddRVATable(std::move(handlers), "__safe_se_handler_table",
1612 "__safe_se_handler_count");
1613}
1614
1615// Add a symbol to an RVA set. Two symbols may have the same RVA, but an RVA set
1616// cannot contain duplicates. Therefore, the set is uniqued by Chunk and the
1617// symbol's offset into that Chunk.
1618static void addSymbolToRVASet(SymbolRVASet &rvaSet, Defined *s) {
1619 Chunk *c = s->getChunk();
1620 if (auto *sc = dyn_cast<SectionChunk>(c))
1621 c = sc->repl; // Look through ICF replacement.
1622 uint32_t off = s->getRVA() - (c ? c->getRVA() : 0);
1623 rvaSet.insert({c, off});
1624}
1625
1626// Given a symbol, add it to the GFIDs table if it is a live, defined, function
1627// symbol in an executable section.
1628static void maybeAddAddressTakenFunction(SymbolRVASet &addressTakenSyms,
1629 Symbol *s) {
1630 if (!s)
1631 return;
1632
1633 switch (s->kind()) {
1634 case Symbol::DefinedLocalImportKind:
1635 case Symbol::DefinedImportDataKind:
1636 // Defines an __imp_ pointer, so it is data, so it is ignored.
1637 break;
1638 case Symbol::DefinedCommonKind:
1639 // Common is always data, so it is ignored.
1640 break;
1641 case Symbol::DefinedAbsoluteKind:
1642 case Symbol::DefinedSyntheticKind:
1643 // Absolute is never code, synthetic generally isn't and usually isn't
1644 // determinable.
1645 break;
1646 case Symbol::LazyArchiveKind:
1647 case Symbol::LazyObjectKind:
1648 case Symbol::LazyDLLSymbolKind:
1649 case Symbol::UndefinedKind:
1650 // Undefined symbols resolve to zero, so they don't have an RVA. Lazy
1651 // symbols shouldn't have relocations.
1652 break;
1653
1654 case Symbol::DefinedImportThunkKind:
1655 // Thunks are always code, include them.
1656 addSymbolToRVASet(addressTakenSyms, cast<Defined>(s));
1657 break;
1658
1659 case Symbol::DefinedRegularKind: {
1660 // This is a regular, defined, symbol from a COFF file. Mark the symbol as
1661 // address taken if the symbol type is function and it's in an executable
1662 // section.
1663 auto *d = cast<DefinedRegular>(s);
1664 if (d->getCOFFSymbol().getComplexType() == COFF::IMAGE_SYM_DTYPE_FUNCTION) {
1665 SectionChunk *sc = dyn_cast<SectionChunk>(d->getChunk());
1666 if (sc && sc->live &&
1667 sc->getOutputCharacteristics() & IMAGE_SCN_MEM_EXECUTE)
1668 addSymbolToRVASet(addressTakenSyms, d);
1669 }
1670 break;
1671 }
1672 }
1673}
1674
1675// Visit all relocations from all section contributions of this object file and
1676// mark the relocation target as address-taken.
1677static void markSymbolsWithRelocations(ObjFile *file,
1678 SymbolRVASet &usedSymbols) {
1679 for (Chunk *c : file->getChunks()) {
1680 // We only care about live section chunks. Common chunks and other chunks
1681 // don't generally contain relocations.
1682 SectionChunk *sc = dyn_cast<SectionChunk>(c);
1683 if (!sc || !sc->live)
1684 continue;
1685
1686 for (const coff_relocation &reloc : sc->getRelocs()) {
1687 if (config->machine == I386 && reloc.Type == COFF::IMAGE_REL_I386_REL32)
1688 // Ignore relative relocations on x86. On x86_64 they can't be ignored
1689 // since they're also used to compute absolute addresses.
1690 continue;
1691
1692 Symbol *ref = sc->file->getSymbol(reloc.SymbolTableIndex);
1693 maybeAddAddressTakenFunction(usedSymbols, ref);
1694 }
1695 }
1696}
1697
1698// Create the guard function id table. This is a table of RVAs of all
1699// address-taken functions. It is sorted and uniqued, just like the safe SEH
1700// table.
1701void Writer::createGuardCFTables() {
1702 SymbolRVASet addressTakenSyms;
1703 SymbolRVASet giatsRVASet;
1704 std::vector<Symbol *> giatsSymbols;
1705 SymbolRVASet longJmpTargets;
1706 SymbolRVASet ehContTargets;
1707 for (ObjFile *file : ctx.objFileInstances) {
1708 // If the object was compiled with /guard:cf, the address taken symbols
1709 // are in .gfids$y sections, the longjmp targets are in .gljmp$y sections,
1710 // and ehcont targets are in .gehcont$y sections. If the object was not
1711 // compiled with /guard:cf, we assume there were no setjmp and ehcont
1712 // targets, and that all code symbols with relocations are possibly
1713 // address-taken.
1714 if (file->hasGuardCF()) {
1715 markSymbolsForRVATable(file, file->getGuardFidChunks(), addressTakenSyms);
1716 markSymbolsForRVATable(file, file->getGuardIATChunks(), giatsRVASet);
1717 getSymbolsFromSections(file, file->getGuardIATChunks(), giatsSymbols);
1718 markSymbolsForRVATable(file, file->getGuardLJmpChunks(), longJmpTargets);
1719 markSymbolsForRVATable(file, file->getGuardEHContChunks(), ehContTargets);
1720 } else {
1721 markSymbolsWithRelocations(file, addressTakenSyms);
1722 }
1723 }
1724
1725 // Mark the image entry as address-taken.
1726 if (config->entry)
1727 maybeAddAddressTakenFunction(addressTakenSyms, config->entry);
1728
1729 // Mark exported symbols in executable sections as address-taken.
1730 for (Export &e : config->exports)
1731 maybeAddAddressTakenFunction(addressTakenSyms, e.sym);
1732
1733 // For each entry in the .giats table, check if it has a corresponding load
1734 // thunk (e.g. because the DLL that defines it will be delay-loaded) and, if
1735 // so, add the load thunk to the address taken (.gfids) table.
1736 for (Symbol *s : giatsSymbols) {
1737 if (auto *di = dyn_cast<DefinedImportData>(s)) {
1738 if (di->loadThunkSym)
1739 addSymbolToRVASet(addressTakenSyms, di->loadThunkSym);
1740 }
1741 }
1742
1743 // Ensure sections referenced in the gfid table are 16-byte aligned.
1744 for (const ChunkAndOffset &c : addressTakenSyms)
1745 if (c.inputChunk->getAlignment() < 16)
1746 c.inputChunk->setAlignment(16);
1747
1748 maybeAddRVATable(std::move(addressTakenSyms), "__guard_fids_table",
1749 "__guard_fids_count");
1750
1751 // Add the Guard Address Taken IAT Entry Table (.giats).
1752 maybeAddRVATable(std::move(giatsRVASet), "__guard_iat_table",
1753 "__guard_iat_count");
1754
1755 // Add the longjmp target table unless the user told us not to.
1756 if (config->guardCF & GuardCFLevel::LongJmp)
1757 maybeAddRVATable(std::move(longJmpTargets), "__guard_longjmp_table",
1758 "__guard_longjmp_count");
1759
1760 // Add the ehcont target table unless the user told us not to.
1761 if (config->guardCF & GuardCFLevel::EHCont)
1762 maybeAddRVATable(std::move(ehContTargets), "__guard_eh_cont_table",
1763 "__guard_eh_cont_count", true);
1764
1765 // Set __guard_flags, which will be used in the load config to indicate that
1766 // /guard:cf was enabled.
1767 uint32_t guardFlags = uint32_t(GuardFlags::CF_INSTRUMENTED) |
1768 uint32_t(GuardFlags::CF_FUNCTION_TABLE_PRESENT);
1769 if (config->guardCF & GuardCFLevel::LongJmp)
1770 guardFlags |= uint32_t(GuardFlags::CF_LONGJUMP_TABLE_PRESENT);
1771 if (config->guardCF & GuardCFLevel::EHCont)
1772 guardFlags |= uint32_t(GuardFlags::EH_CONTINUATION_TABLE_PRESENT);
1773 Symbol *flagSym = ctx.symtab.findUnderscore("__guard_flags");
1774 cast<DefinedAbsolute>(flagSym)->setVA(guardFlags);
1775}
1776
1777// Take a list of input sections containing symbol table indices and add those
1778// symbols to a vector. The challenge is that symbol RVAs are not known and
1779// depend on the table size, so we can't directly build a set of integers.
1780void Writer::getSymbolsFromSections(ObjFile *file,
1781 ArrayRef<SectionChunk *> symIdxChunks,
1782 std::vector<Symbol *> &symbols) {
1783 for (SectionChunk *c : symIdxChunks) {
1784 // Skip sections discarded by linker GC. This comes up when a .gfids section
1785 // is associated with something like a vtable and the vtable is discarded.
1786 // In this case, the associated gfids section is discarded, and we don't
1787 // mark the virtual member functions as address-taken by the vtable.
1788 if (!c->live)
1789 continue;
1790
1791 // Validate that the contents look like symbol table indices.
1792 ArrayRef<uint8_t> data = c->getContents();
1793 if (data.size() % 4 != 0) {
1794 warn("ignoring " + c->getSectionName() +
1795 " symbol table index section in object " + toString(file));
1796 continue;
1797 }
1798
1799 // Read each symbol table index and check if that symbol was included in the
1800 // final link. If so, add it to the vector of symbols.
1801 ArrayRef<ulittle32_t> symIndices(
1802 reinterpret_cast<const ulittle32_t *>(data.data()), data.size() / 4);
1803 ArrayRef<Symbol *> objSymbols = file->getSymbols();
1804 for (uint32_t symIndex : symIndices) {
1805 if (symIndex >= objSymbols.size()) {
1806 warn("ignoring invalid symbol table index in section " +
1807 c->getSectionName() + " in object " + toString(file));
1808 continue;
1809 }
1810 if (Symbol *s = objSymbols[symIndex]) {
1811 if (s->isLive())
1812 symbols.push_back(cast<Symbol>(s));
1813 }
1814 }
1815 }
1816}
1817
1818// Take a list of input sections containing symbol table indices and add those
1819// symbols to an RVA table.
1820void Writer::markSymbolsForRVATable(ObjFile *file,
1821 ArrayRef<SectionChunk *> symIdxChunks,
1822 SymbolRVASet &tableSymbols) {
1823 std::vector<Symbol *> syms;
1824 getSymbolsFromSections(file, symIdxChunks, syms);
1825
1826 for (Symbol *s : syms)
1827 addSymbolToRVASet(tableSymbols, cast<Defined>(s));
1828}
1829
1830// Replace the absolute table symbol with a synthetic symbol pointing to
1831// tableChunk so that we can emit base relocations for it and resolve section
1832// relative relocations.
1833void Writer::maybeAddRVATable(SymbolRVASet tableSymbols, StringRef tableSym,
1834 StringRef countSym, bool hasFlag) {
1835 if (tableSymbols.empty())
1836 return;
1837
1838 NonSectionChunk *tableChunk;
1839 if (hasFlag)
1840 tableChunk = make<RVAFlagTableChunk>(std::move(tableSymbols));
1841 else
1842 tableChunk = make<RVATableChunk>(std::move(tableSymbols));
1843 rdataSec->addChunk(tableChunk);
1844
1845 Symbol *t = ctx.symtab.findUnderscore(tableSym);
1846 Symbol *c = ctx.symtab.findUnderscore(countSym);
1847 replaceSymbol<DefinedSynthetic>(t, t->getName(), tableChunk);
1848 cast<DefinedAbsolute>(c)->setVA(tableChunk->getSize() / (hasFlag ? 5 : 4));
1849}
1850
1851// MinGW specific. Gather all relocations that are imported from a DLL even
1852// though the code didn't expect it to, produce the table that the runtime
1853// uses for fixing them up, and provide the synthetic symbols that the
1854// runtime uses for finding the table.
1855void Writer::createRuntimePseudoRelocs() {
1856 std::vector<RuntimePseudoReloc> rels;
1857
1858 for (Chunk *c : ctx.symtab.getChunks()) {
1859 auto *sc = dyn_cast<SectionChunk>(c);
1860 if (!sc || !sc->live)
1861 continue;
1862 sc->getRuntimePseudoRelocs(rels);
1863 }
1864
1865 if (!config->pseudoRelocs) {
1866 // Not writing any pseudo relocs; if some were needed, error out and
1867 // indicate what required them.
1868 for (const RuntimePseudoReloc &rpr : rels)
1869 error("automatic dllimport of " + rpr.sym->getName() + " in " +
1870 toString(rpr.target->file) + " requires pseudo relocations");
1871 return;
1872 }
1873
1874 if (!rels.empty())
1875 log("Writing " + Twine(rels.size()) + " runtime pseudo relocations");
1876 PseudoRelocTableChunk *table = make<PseudoRelocTableChunk>(rels);
1877 rdataSec->addChunk(table);
1878 EmptyChunk *endOfList = make<EmptyChunk>();
1879 rdataSec->addChunk(endOfList);
1880
1881 Symbol *headSym = ctx.symtab.findUnderscore("__RUNTIME_PSEUDO_RELOC_LIST__");
1882 Symbol *endSym =
1883 ctx.symtab.findUnderscore("__RUNTIME_PSEUDO_RELOC_LIST_END__");
1884 replaceSymbol<DefinedSynthetic>(headSym, headSym->getName(), table);
1885 replaceSymbol<DefinedSynthetic>(endSym, endSym->getName(), endOfList);
1886}
1887
1888// MinGW specific.
1889// The MinGW .ctors and .dtors lists have sentinels at each end;
1890// a (uintptr_t)-1 at the start and a (uintptr_t)0 at the end.
1891// There's a symbol pointing to the start sentinel pointer, __CTOR_LIST__
1892// and __DTOR_LIST__ respectively.
1893void Writer::insertCtorDtorSymbols() {
1894 AbsolutePointerChunk *ctorListHead = make<AbsolutePointerChunk>(-1);
1895 AbsolutePointerChunk *ctorListEnd = make<AbsolutePointerChunk>(0);
1896 AbsolutePointerChunk *dtorListHead = make<AbsolutePointerChunk>(-1);
1897 AbsolutePointerChunk *dtorListEnd = make<AbsolutePointerChunk>(0);
1898 ctorsSec->insertChunkAtStart(ctorListHead);
1899 ctorsSec->addChunk(ctorListEnd);
1900 dtorsSec->insertChunkAtStart(dtorListHead);
1901 dtorsSec->addChunk(dtorListEnd);
1902
1903 Symbol *ctorListSym = ctx.symtab.findUnderscore("__CTOR_LIST__");
1904 Symbol *dtorListSym = ctx.symtab.findUnderscore("__DTOR_LIST__");
1905 replaceSymbol<DefinedSynthetic>(ctorListSym, ctorListSym->getName(),
1906 ctorListHead);
1907 replaceSymbol<DefinedSynthetic>(dtorListSym, dtorListSym->getName(),
1908 dtorListHead);
1909}
1910
1911// Handles /section options to allow users to overwrite
1912// section attributes.
1913void Writer::setSectionPermissions() {
1914 for (auto &p : config->section) {
1915 StringRef name = p.first;
1916 uint32_t perm = p.second;
1917 for (OutputSection *sec : ctx.outputSections)
1918 if (sec->name == name)
1919 sec->setPermissions(perm);
1920 }
1921}
1922
1923// Write section contents to a mmap'ed file.
1924void Writer::writeSections() {
1925 // Record the number of sections to apply section index relocations
1926 // against absolute symbols. See applySecIdx in Chunks.cpp..
1927 DefinedAbsolute::numOutputSections = ctx.outputSections.size();
1928
1929 uint8_t *buf = buffer->getBufferStart();
1930 for (OutputSection *sec : ctx.outputSections) {
1931 uint8_t *secBuf = buf + sec->getFileOff();
1932 // Fill gaps between functions in .text with INT3 instructions
1933 // instead of leaving as NUL bytes (which can be interpreted as
1934 // ADD instructions).
1935 if (sec->header.Characteristics & IMAGE_SCN_CNT_CODE)
1936 memset(secBuf, 0xCC, sec->getRawSize());
1937 parallelForEach(sec->chunks, [&](Chunk *c) {
1938 c->writeTo(secBuf + c->getRVA() - sec->getRVA());
1939 });
1940 }
1941}
1942
1943void Writer::writeBuildId() {
1944 // There are two important parts to the build ID.
1945 // 1) If building with debug info, the COFF debug directory contains a
1946 // timestamp as well as a Guid and Age of the PDB.
1947 // 2) In all cases, the PE COFF file header also contains a timestamp.
1948 // For reproducibility, instead of a timestamp we want to use a hash of the
1949 // PE contents.
1950 if (config->debug) {
1951 assert(buildId && "BuildId is not set!")(static_cast <bool> (buildId && "BuildId is not set!"
) ? void (0) : __assert_fail ("buildId && \"BuildId is not set!\""
, "lld/COFF/Writer.cpp", 1951, __extension__ __PRETTY_FUNCTION__
))
;
1952 // BuildId->BuildId was filled in when the PDB was written.
1953 }
1954
1955 // At this point the only fields in the COFF file which remain unset are the
1956 // "timestamp" in the COFF file header, and the ones in the coff debug
1957 // directory. Now we can hash the file and write that hash to the various
1958 // timestamp fields in the file.
1959 StringRef outputFileData(
1960 reinterpret_cast<const char *>(buffer->getBufferStart()),
1961 buffer->getBufferSize());
1962
1963 uint32_t timestamp = config->timestamp;
1964 uint64_t hash = 0;
1965 bool generateSyntheticBuildId =
1966 config->mingw && config->debug && config->pdbPath.empty();
1967
1968 if (config->repro || generateSyntheticBuildId)
1969 hash = xxHash64(outputFileData);
1970
1971 if (config->repro)
1972 timestamp = static_cast<uint32_t>(hash);
1973
1974 if (generateSyntheticBuildId) {
1975 // For MinGW builds without a PDB file, we still generate a build id
1976 // to allow associating a crash dump to the executable.
1977 buildId->buildId->PDB70.CVSignature = OMF::Signature::PDB70;
1978 buildId->buildId->PDB70.Age = 1;
1979 memcpy(buildId->buildId->PDB70.Signature, &hash, 8);
1980 // xxhash only gives us 8 bytes, so put some fixed data in the other half.
1981 memcpy(&buildId->buildId->PDB70.Signature[8], "LLD PDB.", 8);
1982 }
1983
1984 if (debugDirectory)
1985 debugDirectory->setTimeDateStamp(timestamp);
1986
1987 uint8_t *buf = buffer->getBufferStart();
1988 buf += dosStubSize + sizeof(PEMagic);
1989 object::coff_file_header *coffHeader =
1990 reinterpret_cast<coff_file_header *>(buf);
1991 coffHeader->TimeDateStamp = timestamp;
1992}
1993
1994// Sort .pdata section contents according to PE/COFF spec 5.5.
1995void Writer::sortExceptionTable() {
1996 if (!firstPdata)
1997 return;
1998 // We assume .pdata contains function table entries only.
1999 auto bufAddr = [&](Chunk *c) {
2000 OutputSection *os = ctx.getOutputSection(c);
2001 return buffer->getBufferStart() + os->getFileOff() + c->getRVA() -
2002 os->getRVA();
2003 };
2004 uint8_t *begin = bufAddr(firstPdata);
2005 uint8_t *end = bufAddr(lastPdata) + lastPdata->getSize();
2006 if (config->machine == AMD64) {
2007 struct Entry { ulittle32_t begin, end, unwind; };
2008 if ((end - begin) % sizeof(Entry) != 0) {
2009 fatal("unexpected .pdata size: " + Twine(end - begin) +
2010 " is not a multiple of " + Twine(sizeof(Entry)));
2011 }
2012 parallelSort(
2013 MutableArrayRef<Entry>((Entry *)begin, (Entry *)end),
2014 [](const Entry &a, const Entry &b) { return a.begin < b.begin; });
2015 return;
2016 }
2017 if (config->machine == ARMNT || config->machine == ARM64) {
2018 struct Entry { ulittle32_t begin, unwind; };
2019 if ((end - begin) % sizeof(Entry) != 0) {
2020 fatal("unexpected .pdata size: " + Twine(end - begin) +
2021 " is not a multiple of " + Twine(sizeof(Entry)));
2022 }
2023 parallelSort(
2024 MutableArrayRef<Entry>((Entry *)begin, (Entry *)end),
2025 [](const Entry &a, const Entry &b) { return a.begin < b.begin; });
2026 return;
2027 }
2028 lld::errs() << "warning: don't know how to handle .pdata.\n";
2029}
2030
2031// The CRT section contains, among other things, the array of function
2032// pointers that initialize every global variable that is not trivially
2033// constructed. The CRT calls them one after the other prior to invoking
2034// main().
2035//
2036// As per C++ spec, 3.6.2/2.3,
2037// "Variables with ordered initialization defined within a single
2038// translation unit shall be initialized in the order of their definitions
2039// in the translation unit"
2040//
2041// It is therefore critical to sort the chunks containing the function
2042// pointers in the order that they are listed in the object file (top to
2043// bottom), otherwise global objects might not be initialized in the
2044// correct order.
2045void Writer::sortCRTSectionChunks(std::vector<Chunk *> &chunks) {
2046 auto sectionChunkOrder = [](const Chunk *a, const Chunk *b) {
2047 auto sa = dyn_cast<SectionChunk>(a);
2048 auto sb = dyn_cast<SectionChunk>(b);
2049 assert(sa && sb && "Non-section chunks in CRT section!")(static_cast <bool> (sa && sb && "Non-section chunks in CRT section!"
) ? void (0) : __assert_fail ("sa && sb && \"Non-section chunks in CRT section!\""
, "lld/COFF/Writer.cpp", 2049, __extension__ __PRETTY_FUNCTION__
))
;
2050
2051 StringRef sAObj = sa->file->mb.getBufferIdentifier();
2052 StringRef sBObj = sb->file->mb.getBufferIdentifier();
2053
2054 return sAObj == sBObj && sa->getSectionNumber() < sb->getSectionNumber();
2055 };
2056 llvm::stable_sort(chunks, sectionChunkOrder);
2057
2058 if (config->verbose) {
2059 for (auto &c : chunks) {
2060 auto sc = dyn_cast<SectionChunk>(c);
2061 log(" " + sc->file->mb.getBufferIdentifier().str() +
2062 ", SectionID: " + Twine(sc->getSectionNumber()));
2063 }
2064 }
2065}
2066
2067OutputSection *Writer::findSection(StringRef name) {
2068 for (OutputSection *sec : ctx.outputSections)
2069 if (sec->name == name)
2070 return sec;
2071 return nullptr;
2072}
2073
2074uint32_t Writer::getSizeOfInitializedData() {
2075 uint32_t res = 0;
2076 for (OutputSection *s : ctx.outputSections)
2077 if (s->header.Characteristics & IMAGE_SCN_CNT_INITIALIZED_DATA)
2078 res += s->getRawSize();
2079 return res;
2080}
2081
2082// Add base relocations to .reloc section.
2083void Writer::addBaserels() {
2084 if (!config->relocatable)
2085 return;
2086 relocSec->chunks.clear();
2087 std::vector<Baserel> v;
2088 for (OutputSection *sec : ctx.outputSections) {
2089 if (sec->header.Characteristics & IMAGE_SCN_MEM_DISCARDABLE)
2090 continue;
2091 // Collect all locations for base relocations.
2092 for (Chunk *c : sec->chunks)
2093 c->getBaserels(&v);
2094 // Add the addresses to .reloc section.
2095 if (!v.empty())
2096 addBaserelBlocks(v);
2097 v.clear();
2098 }
2099}
2100
2101// Add addresses to .reloc section. Note that addresses are grouped by page.
2102void Writer::addBaserelBlocks(std::vector<Baserel> &v) {
2103 const uint32_t mask = ~uint32_t(pageSize - 1);
2104 uint32_t page = v[0].rva & mask;
2105 size_t i = 0, j = 1;
2106 for (size_t e = v.size(); j < e; ++j) {
2107 uint32_t p = v[j].rva & mask;
2108 if (p == page)
2109 continue;
2110 relocSec->addChunk(make<BaserelChunk>(page, &v[i], &v[0] + j));
2111 i = j;
2112 page = p;
2113 }
2114 if (i == j)
2115 return;
2116 relocSec->addChunk(make<BaserelChunk>(page, &v[i], &v[0] + j));
2117}
2118
2119PartialSection *Writer::createPartialSection(StringRef name,
2120 uint32_t outChars) {
2121 PartialSection *&pSec = partialSections[{name, outChars}];
2122 if (pSec)
2123 return pSec;
2124 pSec = make<PartialSection>(name, outChars);
2125 return pSec;
2126}
2127
2128PartialSection *Writer::findPartialSection(StringRef name, uint32_t outChars) {
2129 auto it = partialSections.find({name, outChars});
2130 if (it != partialSections.end())
2131 return it->second;
2132 return nullptr;
2133}
2134
2135void Writer::fixTlsAlignment() {
2136 Defined *tlsSym =
2137 dyn_cast_or_null<Defined>(ctx.symtab.findUnderscore("_tls_used"));
2138 if (!tlsSym)
2139 return;
2140
2141 OutputSection *sec = ctx.getOutputSection(tlsSym->getChunk());
2142 assert(sec && tlsSym->getRVA() >= sec->getRVA() &&(static_cast <bool> (sec && tlsSym->getRVA()
>= sec->getRVA() && "no output section for _tls_used"
) ? void (0) : __assert_fail ("sec && tlsSym->getRVA() >= sec->getRVA() && \"no output section for _tls_used\""
, "lld/COFF/Writer.cpp", 2143, __extension__ __PRETTY_FUNCTION__
))
2143 "no output section for _tls_used")(static_cast <bool> (sec && tlsSym->getRVA()
>= sec->getRVA() && "no output section for _tls_used"
) ? void (0) : __assert_fail ("sec && tlsSym->getRVA() >= sec->getRVA() && \"no output section for _tls_used\""
, "lld/COFF/Writer.cpp", 2143, __extension__ __PRETTY_FUNCTION__
))
;
2144
2145 uint8_t *secBuf = buffer->getBufferStart() + sec->getFileOff();
2146 uint64_t tlsOffset = tlsSym->getRVA() - sec->getRVA();
2147 uint64_t directorySize = config->is64()
2148 ? sizeof(object::coff_tls_directory64)
2149 : sizeof(object::coff_tls_directory32);
2150
2151 if (tlsOffset + directorySize > sec->getRawSize())
2152 fatal("_tls_used sym is malformed");
2153
2154 if (config->is64()) {
2155 object::coff_tls_directory64 *tlsDir =
2156 reinterpret_cast<object::coff_tls_directory64 *>(&secBuf[tlsOffset]);
2157 tlsDir->setAlignment(tlsAlignment);
2158 } else {
2159 object::coff_tls_directory32 *tlsDir =
2160 reinterpret_cast<object::coff_tls_directory32 *>(&secBuf[tlsOffset]);
2161 tlsDir->setAlignment(tlsAlignment);
2162 }
2163}
2164
2165void Writer::checkLoadConfig() {
2166 Symbol *sym = ctx.symtab.findUnderscore("_load_config_used");
2167 auto *b = cast_if_present<DefinedRegular>(sym);
2168 if (!b) {
2169 if (config->guardCF != GuardCFLevel::Off)
2170 warn("Control Flow Guard is enabled but '_load_config_used' is missing");
2171 return;
2172 }
2173
2174 OutputSection *sec = ctx.getOutputSection(b->getChunk());
2175 uint8_t *buf = buffer->getBufferStart();
2176 uint8_t *secBuf = buf + sec->getFileOff();
2177 uint8_t *symBuf = secBuf + (b->getRVA() - sec->getRVA());
2178 uint32_t expectedAlign = config->is64() ? 8 : 4;
2179 if (b->getChunk()->getAlignment() < expectedAlign)
2180 warn("'_load_config_used' is misaligned (expected alignment to be " +
2181 Twine(expectedAlign) + " bytes, got " +
2182 Twine(b->getChunk()->getAlignment()) + " instead)");
2183 else if (!isAligned(Align(expectedAlign), b->getRVA()))
2184 warn("'_load_config_used' is misaligned (RVA is 0x" +
2185 Twine::utohexstr(b->getRVA()) + " not aligned to " +
2186 Twine(expectedAlign) + " bytes)");
2187
2188 if (config->is64())
2189 checkLoadConfigGuardData(
2190 reinterpret_cast<const coff_load_configuration64 *>(symBuf));
2191 else
2192 checkLoadConfigGuardData(
2193 reinterpret_cast<const coff_load_configuration32 *>(symBuf));
2194}
2195
2196template <typename T>
2197void Writer::checkLoadConfigGuardData(const T *loadConfig) {
2198 size_t loadConfigSize = loadConfig->Size;
2199
2200#define RETURN_IF_NOT_CONTAINS(field) \
2201 if (loadConfigSize < offsetof(T, field)__builtin_offsetof(T, field) + sizeof(T::field)) { \
2202 warn("'_load_config_used' structure too small to include " #field); \
2203 return; \
2204 }
2205
2206#define IF_CONTAINS(field) \
2207 if (loadConfigSize >= offsetof(T, field)__builtin_offsetof(T, field) + sizeof(T::field))
2208
2209#define CHECK_VA(field, sym) \
2210 if (auto *s = dyn_cast<DefinedSynthetic>(ctx.symtab.findUnderscore(sym))) \
2211 if (loadConfig->field != config->imageBase + s->getRVA()) \
2212 warn(#field " not set correctly in '_load_config_used'");
2213
2214#define CHECK_ABSOLUTE(field, sym) \
2215 if (auto *s = dyn_cast<DefinedAbsolute>(ctx.symtab.findUnderscore(sym))) \
2216 if (loadConfig->field != s->getVA()) \
2217 warn(#field " not set correctly in '_load_config_used'");
2218
2219 if (config->guardCF == GuardCFLevel::Off)
2220 return;
2221 RETURN_IF_NOT_CONTAINS(GuardFlags)
2222 CHECK_VA(GuardCFFunctionTable, "__guard_fids_table")
2223 CHECK_ABSOLUTE(GuardCFFunctionCount, "__guard_fids_count")
2224 CHECK_ABSOLUTE(GuardFlags, "__guard_flags")
2225 IF_CONTAINS(GuardAddressTakenIatEntryCount) {
2226 CHECK_VA(GuardAddressTakenIatEntryTable, "__guard_iat_table")
2227 CHECK_ABSOLUTE(GuardAddressTakenIatEntryCount, "__guard_iat_count")
2228 }
2229
2230 if (!(config->guardCF & GuardCFLevel::LongJmp))
2231 return;
2232 RETURN_IF_NOT_CONTAINS(GuardLongJumpTargetCount)
2233 CHECK_VA(GuardLongJumpTargetTable, "__guard_longjmp_table")
2234 CHECK_ABSOLUTE(GuardLongJumpTargetCount, "__guard_longjmp_count")
2235
2236 if (!(config->guardCF & GuardCFLevel::EHCont))
2237 return;
2238 RETURN_IF_NOT_CONTAINS(GuardEHContinuationCount)
2239 CHECK_VA(GuardEHContinuationTable, "__guard_eh_cont_table")
2240 CHECK_ABSOLUTE(GuardEHContinuationCount, "__guard_eh_cont_count")
2241
2242#undef RETURN_IF_NOT_CONTAINS
2243#undef IF_CONTAINS
2244#undef CHECK_VA
2245#undef CHECK_ABSOLUTE
2246}