1 //===- SyntheticSections.cpp ----------------------------------------------===//
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file contains linker-synthesized sections. Currently,
11 // synthetic sections are created either output sections or input sections,
12 // but we are rewriting code so that all synthetic sections are created as
15 //===----------------------------------------------------------------------===//
17 #include "SyntheticSections.h"
20 #include "InputFiles.h"
21 #include "LinkerScript.h"
22 #include "OutputSections.h"
23 #include "SymbolTable.h"
27 #include "lld/Common/ErrorHandler.h"
28 #include "lld/Common/Memory.h"
29 #include "lld/Common/Strings.h"
30 #include "lld/Common/Threads.h"
31 #include "lld/Common/Version.h"
32 #include "llvm/ADT/SetOperations.h"
33 #include "llvm/BinaryFormat/Dwarf.h"
34 #include "llvm/DebugInfo/DWARF/DWARFDebugPubTable.h"
35 #include "llvm/Object/Decompressor.h"
36 #include "llvm/Object/ELFObjectFile.h"
37 #include "llvm/Support/Endian.h"
38 #include "llvm/Support/LEB128.h"
39 #include "llvm/Support/MD5.h"
40 #include "llvm/Support/RandomNumberGenerator.h"
41 #include "llvm/Support/SHA1.h"
42 #include "llvm/Support/xxhash.h"
47 using namespace llvm::dwarf;
48 using namespace llvm::ELF;
49 using namespace llvm::object;
50 using namespace llvm::support;
53 using namespace lld::elf;
55 using llvm::support::endian::read32le;
56 using llvm::support::endian::write32le;
57 using llvm::support::endian::write64le;
59 constexpr size_t MergeNoTailSection::NumShards;
61 // Returns an LLD version string.
62 static ArrayRef<uint8_t> getVersion() {
63 // Check LLD_VERSION first for ease of testing.
64 // You can get consistent output by using the environment variable.
65 // This is only for testing.
66 StringRef S = getenv("LLD_VERSION");
68 S = Saver.save(Twine("Linker: ") + getLLDVersion());
70 // +1 to include the terminating '\0'.
71 return {(const uint8_t *)S.data(), S.size() + 1};
74 // Creates a .comment section containing LLD version info.
75 // With this feature, you can identify LLD-generated binaries easily
76 // by "readelf --string-dump .comment <file>".
77 // The returned object is a mergeable string section.
78 MergeInputSection *elf::createCommentSection() {
79 return make<MergeInputSection>(SHF_MERGE | SHF_STRINGS, SHT_PROGBITS, 1,
80 getVersion(), ".comment");
83 // .MIPS.abiflags section.
85 MipsAbiFlagsSection<ELFT>::MipsAbiFlagsSection(Elf_Mips_ABIFlags Flags)
86 : SyntheticSection(SHF_ALLOC, SHT_MIPS_ABIFLAGS, 8, ".MIPS.abiflags"),
88 this->Entsize = sizeof(Elf_Mips_ABIFlags);
91 template <class ELFT> void MipsAbiFlagsSection<ELFT>::writeTo(uint8_t *Buf) {
92 memcpy(Buf, &Flags, sizeof(Flags));
96 MipsAbiFlagsSection<ELFT> *MipsAbiFlagsSection<ELFT>::create() {
97 Elf_Mips_ABIFlags Flags = {};
100 for (InputSectionBase *Sec : InputSections) {
101 if (Sec->Type != SHT_MIPS_ABIFLAGS)
106 std::string Filename = toString(Sec->File);
107 const size_t Size = Sec->Data.size();
108 // Older version of BFD (such as the default FreeBSD linker) concatenate
109 // .MIPS.abiflags instead of merging. To allow for this case (or potential
110 // zero padding) we ignore everything after the first Elf_Mips_ABIFlags
111 if (Size < sizeof(Elf_Mips_ABIFlags)) {
112 error(Filename + ": invalid size of .MIPS.abiflags section: got " +
113 Twine(Size) + " instead of " + Twine(sizeof(Elf_Mips_ABIFlags)));
116 auto *S = reinterpret_cast<const Elf_Mips_ABIFlags *>(Sec->Data.data());
117 if (S->version != 0) {
118 error(Filename + ": unexpected .MIPS.abiflags version " +
123 // LLD checks ISA compatibility in calcMipsEFlags(). Here we just
124 // select the highest number of ISA/Rev/Ext.
125 Flags.isa_level = std::max(Flags.isa_level, S->isa_level);
126 Flags.isa_rev = std::max(Flags.isa_rev, S->isa_rev);
127 Flags.isa_ext = std::max(Flags.isa_ext, S->isa_ext);
128 Flags.gpr_size = std::max(Flags.gpr_size, S->gpr_size);
129 Flags.cpr1_size = std::max(Flags.cpr1_size, S->cpr1_size);
130 Flags.cpr2_size = std::max(Flags.cpr2_size, S->cpr2_size);
131 Flags.ases |= S->ases;
132 Flags.flags1 |= S->flags1;
133 Flags.flags2 |= S->flags2;
134 Flags.fp_abi = elf::getMipsFpAbiFlag(Flags.fp_abi, S->fp_abi, Filename);
138 return make<MipsAbiFlagsSection<ELFT>>(Flags);
142 // .MIPS.options section.
143 template <class ELFT>
144 MipsOptionsSection<ELFT>::MipsOptionsSection(Elf_Mips_RegInfo Reginfo)
145 : SyntheticSection(SHF_ALLOC, SHT_MIPS_OPTIONS, 8, ".MIPS.options"),
147 this->Entsize = sizeof(Elf_Mips_Options) + sizeof(Elf_Mips_RegInfo);
150 template <class ELFT> void MipsOptionsSection<ELFT>::writeTo(uint8_t *Buf) {
151 auto *Options = reinterpret_cast<Elf_Mips_Options *>(Buf);
152 Options->kind = ODK_REGINFO;
153 Options->size = getSize();
155 if (!Config->Relocatable)
156 Reginfo.ri_gp_value = InX::MipsGot->getGp();
157 memcpy(Buf + sizeof(Elf_Mips_Options), &Reginfo, sizeof(Reginfo));
160 template <class ELFT>
161 MipsOptionsSection<ELFT> *MipsOptionsSection<ELFT>::create() {
166 std::vector<InputSectionBase *> Sections;
167 for (InputSectionBase *Sec : InputSections)
168 if (Sec->Type == SHT_MIPS_OPTIONS)
169 Sections.push_back(Sec);
171 if (Sections.empty())
174 Elf_Mips_RegInfo Reginfo = {};
175 for (InputSectionBase *Sec : Sections) {
178 std::string Filename = toString(Sec->File);
179 ArrayRef<uint8_t> D = Sec->Data;
182 if (D.size() < sizeof(Elf_Mips_Options)) {
183 error(Filename + ": invalid size of .MIPS.options section");
187 auto *Opt = reinterpret_cast<const Elf_Mips_Options *>(D.data());
188 if (Opt->kind == ODK_REGINFO) {
189 Reginfo.ri_gprmask |= Opt->getRegInfo().ri_gprmask;
190 Sec->getFile<ELFT>()->MipsGp0 = Opt->getRegInfo().ri_gp_value;
195 fatal(Filename + ": zero option descriptor size");
196 D = D.slice(Opt->size);
200 return make<MipsOptionsSection<ELFT>>(Reginfo);
203 // MIPS .reginfo section.
204 template <class ELFT>
205 MipsReginfoSection<ELFT>::MipsReginfoSection(Elf_Mips_RegInfo Reginfo)
206 : SyntheticSection(SHF_ALLOC, SHT_MIPS_REGINFO, 4, ".reginfo"),
208 this->Entsize = sizeof(Elf_Mips_RegInfo);
211 template <class ELFT> void MipsReginfoSection<ELFT>::writeTo(uint8_t *Buf) {
212 if (!Config->Relocatable)
213 Reginfo.ri_gp_value = InX::MipsGot->getGp();
214 memcpy(Buf, &Reginfo, sizeof(Reginfo));
217 template <class ELFT>
218 MipsReginfoSection<ELFT> *MipsReginfoSection<ELFT>::create() {
219 // Section should be alive for O32 and N32 ABIs only.
223 std::vector<InputSectionBase *> Sections;
224 for (InputSectionBase *Sec : InputSections)
225 if (Sec->Type == SHT_MIPS_REGINFO)
226 Sections.push_back(Sec);
228 if (Sections.empty())
231 Elf_Mips_RegInfo Reginfo = {};
232 for (InputSectionBase *Sec : Sections) {
235 if (Sec->Data.size() != sizeof(Elf_Mips_RegInfo)) {
236 error(toString(Sec->File) + ": invalid size of .reginfo section");
240 auto *R = reinterpret_cast<const Elf_Mips_RegInfo *>(Sec->Data.data());
241 Reginfo.ri_gprmask |= R->ri_gprmask;
242 Sec->getFile<ELFT>()->MipsGp0 = R->ri_gp_value;
245 return make<MipsReginfoSection<ELFT>>(Reginfo);
248 InputSection *elf::createInterpSection() {
249 // StringSaver guarantees that the returned string ends with '\0'.
250 StringRef S = Saver.save(Config->DynamicLinker);
251 ArrayRef<uint8_t> Contents = {(const uint8_t *)S.data(), S.size() + 1};
253 auto *Sec = make<InputSection>(nullptr, SHF_ALLOC, SHT_PROGBITS, 1, Contents,
259 Defined *elf::addSyntheticLocal(StringRef Name, uint8_t Type, uint64_t Value,
260 uint64_t Size, InputSectionBase &Section) {
261 auto *S = make<Defined>(Section.File, Name, STB_LOCAL, STV_DEFAULT, Type,
262 Value, Size, &Section);
264 InX::SymTab->addSymbol(S);
268 static size_t getHashSize() {
269 switch (Config->BuildId) {
270 case BuildIdKind::Fast:
272 case BuildIdKind::Md5:
273 case BuildIdKind::Uuid:
275 case BuildIdKind::Sha1:
277 case BuildIdKind::Hexstring:
278 return Config->BuildIdVector.size();
280 llvm_unreachable("unknown BuildIdKind");
284 BuildIdSection::BuildIdSection()
285 : SyntheticSection(SHF_ALLOC, SHT_NOTE, 4, ".note.gnu.build-id"),
286 HashSize(getHashSize()) {}
288 void BuildIdSection::writeTo(uint8_t *Buf) {
289 write32(Buf, 4); // Name size
290 write32(Buf + 4, HashSize); // Content size
291 write32(Buf + 8, NT_GNU_BUILD_ID); // Type
292 memcpy(Buf + 12, "GNU", 4); // Name string
296 // Split one uint8 array into small pieces of uint8 arrays.
297 static std::vector<ArrayRef<uint8_t>> split(ArrayRef<uint8_t> Arr,
299 std::vector<ArrayRef<uint8_t>> Ret;
300 while (Arr.size() > ChunkSize) {
301 Ret.push_back(Arr.take_front(ChunkSize));
302 Arr = Arr.drop_front(ChunkSize);
309 // Computes a hash value of Data using a given hash function.
310 // In order to utilize multiple cores, we first split data into 1MB
311 // chunks, compute a hash for each chunk, and then compute a hash value
312 // of the hash values.
313 void BuildIdSection::computeHash(
314 llvm::ArrayRef<uint8_t> Data,
315 std::function<void(uint8_t *Dest, ArrayRef<uint8_t> Arr)> HashFn) {
316 std::vector<ArrayRef<uint8_t>> Chunks = split(Data, 1024 * 1024);
317 std::vector<uint8_t> Hashes(Chunks.size() * HashSize);
319 // Compute hash values.
320 parallelForEachN(0, Chunks.size(), [&](size_t I) {
321 HashFn(Hashes.data() + I * HashSize, Chunks[I]);
324 // Write to the final output buffer.
325 HashFn(HashBuf, Hashes);
328 BssSection::BssSection(StringRef Name, uint64_t Size, uint32_t Alignment)
329 : SyntheticSection(SHF_ALLOC | SHF_WRITE, SHT_NOBITS, Alignment, Name) {
334 void BuildIdSection::writeBuildId(ArrayRef<uint8_t> Buf) {
335 switch (Config->BuildId) {
336 case BuildIdKind::Fast:
337 computeHash(Buf, [](uint8_t *Dest, ArrayRef<uint8_t> Arr) {
338 write64le(Dest, xxHash64(toStringRef(Arr)));
341 case BuildIdKind::Md5:
342 computeHash(Buf, [](uint8_t *Dest, ArrayRef<uint8_t> Arr) {
343 memcpy(Dest, MD5::hash(Arr).data(), 16);
346 case BuildIdKind::Sha1:
347 computeHash(Buf, [](uint8_t *Dest, ArrayRef<uint8_t> Arr) {
348 memcpy(Dest, SHA1::hash(Arr).data(), 20);
351 case BuildIdKind::Uuid:
352 if (auto EC = getRandomBytes(HashBuf, HashSize))
353 error("entropy source failure: " + EC.message());
355 case BuildIdKind::Hexstring:
356 memcpy(HashBuf, Config->BuildIdVector.data(), Config->BuildIdVector.size());
359 llvm_unreachable("unknown BuildIdKind");
363 EhFrameSection::EhFrameSection()
364 : SyntheticSection(SHF_ALLOC, SHT_PROGBITS, 1, ".eh_frame") {}
366 // Search for an existing CIE record or create a new one.
367 // CIE records from input object files are uniquified by their contents
368 // and where their relocations point to.
369 template <class ELFT, class RelTy>
370 CieRecord *EhFrameSection::addCie(EhSectionPiece &Cie, ArrayRef<RelTy> Rels) {
371 Symbol *Personality = nullptr;
372 unsigned FirstRelI = Cie.FirstRelocation;
373 if (FirstRelI != (unsigned)-1)
375 &Cie.Sec->template getFile<ELFT>()->getRelocTargetSym(Rels[FirstRelI]);
377 // Search for an existing CIE by CIE contents/relocation target pair.
378 CieRecord *&Rec = CieMap[{Cie.data(), Personality}];
380 // If not found, create a new one.
382 Rec = make<CieRecord>();
384 CieRecords.push_back(Rec);
389 // There is one FDE per function. Returns true if a given FDE
390 // points to a live function.
391 template <class ELFT, class RelTy>
392 bool EhFrameSection::isFdeLive(EhSectionPiece &Fde, ArrayRef<RelTy> Rels) {
393 auto *Sec = cast<EhInputSection>(Fde.Sec);
394 unsigned FirstRelI = Fde.FirstRelocation;
396 // An FDE should point to some function because FDEs are to describe
397 // functions. That's however not always the case due to an issue of
398 // ld.gold with -r. ld.gold may discard only functions and leave their
399 // corresponding FDEs, which results in creating bad .eh_frame sections.
400 // To deal with that, we ignore such FDEs.
401 if (FirstRelI == (unsigned)-1)
404 const RelTy &Rel = Rels[FirstRelI];
405 Symbol &B = Sec->template getFile<ELFT>()->getRelocTargetSym(Rel);
407 // FDEs for garbage-collected or merged-by-ICF sections are dead.
408 if (auto *D = dyn_cast<Defined>(&B))
409 if (SectionBase *Sec = D->Section)
414 // .eh_frame is a sequence of CIE or FDE records. In general, there
415 // is one CIE record per input object file which is followed by
416 // a list of FDEs. This function searches an existing CIE or create a new
417 // one and associates FDEs to the CIE.
418 template <class ELFT, class RelTy>
419 void EhFrameSection::addSectionAux(EhInputSection *Sec, ArrayRef<RelTy> Rels) {
421 for (EhSectionPiece &Piece : Sec->Pieces) {
422 // The empty record is the end marker.
426 size_t Offset = Piece.InputOff;
427 uint32_t ID = read32(Piece.data().data() + 4);
429 OffsetToCie[Offset] = addCie<ELFT>(Piece, Rels);
433 uint32_t CieOffset = Offset + 4 - ID;
434 CieRecord *Rec = OffsetToCie[CieOffset];
436 fatal(toString(Sec) + ": invalid CIE reference");
438 if (!isFdeLive<ELFT>(Piece, Rels))
440 Rec->Fdes.push_back(&Piece);
445 template <class ELFT> void EhFrameSection::addSection(InputSectionBase *C) {
446 auto *Sec = cast<EhInputSection>(C);
449 Alignment = std::max(Alignment, Sec->Alignment);
450 Sections.push_back(Sec);
452 for (auto *DS : Sec->DependentSections)
453 DependentSections.push_back(DS);
455 if (Sec->Pieces.empty())
458 if (Sec->AreRelocsRela)
459 addSectionAux<ELFT>(Sec, Sec->template relas<ELFT>());
461 addSectionAux<ELFT>(Sec, Sec->template rels<ELFT>());
464 static void writeCieFde(uint8_t *Buf, ArrayRef<uint8_t> D) {
465 memcpy(Buf, D.data(), D.size());
467 size_t Aligned = alignTo(D.size(), Config->Wordsize);
469 // Zero-clear trailing padding if it exists.
470 memset(Buf + D.size(), 0, Aligned - D.size());
472 // Fix the size field. -4 since size does not include the size field itself.
473 write32(Buf, Aligned - 4);
476 void EhFrameSection::finalizeContents() {
477 assert(!this->Size); // Not finalized.
479 for (CieRecord *Rec : CieRecords) {
480 Rec->Cie->OutputOff = Off;
481 Off += alignTo(Rec->Cie->Size, Config->Wordsize);
483 for (EhSectionPiece *Fde : Rec->Fdes) {
484 Fde->OutputOff = Off;
485 Off += alignTo(Fde->Size, Config->Wordsize);
489 // The LSB standard does not allow a .eh_frame section with zero
490 // Call Frame Information records. glibc unwind-dw2-fde.c
491 // classify_object_over_fdes expects there is a CIE record length 0 as a
492 // terminator. Thus we add one unconditionally.
498 // Returns data for .eh_frame_hdr. .eh_frame_hdr is a binary search table
499 // to get an FDE from an address to which FDE is applied. This function
500 // returns a list of such pairs.
501 std::vector<EhFrameSection::FdeData> EhFrameSection::getFdeData() const {
502 uint8_t *Buf = getParent()->Loc + OutSecOff;
503 std::vector<FdeData> Ret;
505 uint64_t VA = InX::EhFrameHdr->getVA();
506 for (CieRecord *Rec : CieRecords) {
507 uint8_t Enc = getFdeEncoding(Rec->Cie);
508 for (EhSectionPiece *Fde : Rec->Fdes) {
509 uint64_t Pc = getFdePc(Buf, Fde->OutputOff, Enc);
510 uint64_t FdeVA = getParent()->Addr + Fde->OutputOff;
511 if (!isInt<32>(Pc - VA))
512 fatal(toString(Fde->Sec) + ": PC offset is too large: 0x" +
513 Twine::utohexstr(Pc - VA));
514 Ret.push_back({uint32_t(Pc - VA), uint32_t(FdeVA - VA)});
518 // Sort the FDE list by their PC and uniqueify. Usually there is only
519 // one FDE for a PC (i.e. function), but if ICF merges two functions
520 // into one, there can be more than one FDEs pointing to the address.
521 auto Less = [](const FdeData &A, const FdeData &B) {
522 return A.PcRel < B.PcRel;
524 std::stable_sort(Ret.begin(), Ret.end(), Less);
525 auto Eq = [](const FdeData &A, const FdeData &B) {
526 return A.PcRel == B.PcRel;
528 Ret.erase(std::unique(Ret.begin(), Ret.end(), Eq), Ret.end());
533 static uint64_t readFdeAddr(uint8_t *Buf, int Size) {
535 case DW_EH_PE_udata2:
537 case DW_EH_PE_sdata2:
538 return (int16_t)read16(Buf);
539 case DW_EH_PE_udata4:
541 case DW_EH_PE_sdata4:
542 return (int32_t)read32(Buf);
543 case DW_EH_PE_udata8:
544 case DW_EH_PE_sdata8:
546 case DW_EH_PE_absptr:
547 return readUint(Buf);
549 fatal("unknown FDE size encoding");
552 // Returns the VA to which a given FDE (on a mmap'ed buffer) is applied to.
553 // We need it to create .eh_frame_hdr section.
554 uint64_t EhFrameSection::getFdePc(uint8_t *Buf, size_t FdeOff,
556 // The starting address to which this FDE applies is
557 // stored at FDE + 8 byte.
558 size_t Off = FdeOff + 8;
559 uint64_t Addr = readFdeAddr(Buf + Off, Enc & 0xf);
560 if ((Enc & 0x70) == DW_EH_PE_absptr)
562 if ((Enc & 0x70) == DW_EH_PE_pcrel)
563 return Addr + getParent()->Addr + Off;
564 fatal("unknown FDE size relative encoding");
567 void EhFrameSection::writeTo(uint8_t *Buf) {
568 // Write CIE and FDE records.
569 for (CieRecord *Rec : CieRecords) {
570 size_t CieOffset = Rec->Cie->OutputOff;
571 writeCieFde(Buf + CieOffset, Rec->Cie->data());
573 for (EhSectionPiece *Fde : Rec->Fdes) {
574 size_t Off = Fde->OutputOff;
575 writeCieFde(Buf + Off, Fde->data());
577 // FDE's second word should have the offset to an associated CIE.
579 write32(Buf + Off + 4, Off + 4 - CieOffset);
583 // Apply relocations. .eh_frame section contents are not contiguous
584 // in the output buffer, but relocateAlloc() still works because
585 // getOffset() takes care of discontiguous section pieces.
586 for (EhInputSection *S : Sections)
587 S->relocateAlloc(Buf, nullptr);
590 GotSection::GotSection()
591 : SyntheticSection(SHF_ALLOC | SHF_WRITE, SHT_PROGBITS,
592 Target->GotEntrySize, ".got") {
593 // PPC64 saves the ElfSym::GlobalOffsetTable .TOC. as the first entry in the
594 // .got. If there are no references to .TOC. in the symbol table,
595 // ElfSym::GlobalOffsetTable will not be defined and we won't need to save
596 // .TOC. in the .got. When it is defined, we increase NumEntries by the number
597 // of entries used to emit ElfSym::GlobalOffsetTable.
598 if (ElfSym::GlobalOffsetTable && !Target->GotBaseSymInGotPlt)
599 NumEntries += Target->GotHeaderEntriesNum;
602 void GotSection::addEntry(Symbol &Sym) {
603 Sym.GotIndex = NumEntries;
607 bool GotSection::addDynTlsEntry(Symbol &Sym) {
608 if (Sym.GlobalDynIndex != -1U)
610 Sym.GlobalDynIndex = NumEntries;
611 // Global Dynamic TLS entries take two GOT slots.
616 // Reserves TLS entries for a TLS module ID and a TLS block offset.
617 // In total it takes two GOT slots.
618 bool GotSection::addTlsIndex() {
619 if (TlsIndexOff != uint32_t(-1))
621 TlsIndexOff = NumEntries * Config->Wordsize;
626 uint64_t GotSection::getGlobalDynAddr(const Symbol &B) const {
627 return this->getVA() + B.GlobalDynIndex * Config->Wordsize;
630 uint64_t GotSection::getGlobalDynOffset(const Symbol &B) const {
631 return B.GlobalDynIndex * Config->Wordsize;
634 void GotSection::finalizeContents() {
635 Size = NumEntries * Config->Wordsize;
638 bool GotSection::empty() const {
639 // We need to emit a GOT even if it's empty if there's a relocation that is
640 // relative to GOT(such as GOTOFFREL) or there's a symbol that points to a GOT
641 // (i.e. _GLOBAL_OFFSET_TABLE_) that the target defines relative to the .got.
642 return NumEntries == 0 && !HasGotOffRel &&
643 !(ElfSym::GlobalOffsetTable && !Target->GotBaseSymInGotPlt);
646 void GotSection::writeTo(uint8_t *Buf) {
647 // Buf points to the start of this section's buffer,
648 // whereas InputSectionBase::relocateAlloc() expects its argument
649 // to point to the start of the output section.
650 Target->writeGotHeader(Buf);
651 relocateAlloc(Buf - OutSecOff, Buf - OutSecOff + Size);
654 static uint64_t getMipsPageAddr(uint64_t Addr) {
655 return (Addr + 0x8000) & ~0xffff;
658 static uint64_t getMipsPageCount(uint64_t Size) {
659 return (Size + 0xfffe) / 0xffff + 1;
662 MipsGotSection::MipsGotSection()
663 : SyntheticSection(SHF_ALLOC | SHF_WRITE | SHF_MIPS_GPREL, SHT_PROGBITS, 16,
666 void MipsGotSection::addEntry(InputFile &File, Symbol &Sym, int64_t Addend,
668 FileGot &G = getGot(File);
669 if (Expr == R_MIPS_GOT_LOCAL_PAGE) {
670 if (const OutputSection *OS = Sym.getOutputSection())
671 G.PagesMap.insert({OS, {}});
673 G.Local16.insert({{nullptr, getMipsPageAddr(Sym.getVA(Addend))}, 0});
674 } else if (Sym.isTls())
675 G.Tls.insert({&Sym, 0});
676 else if (Sym.IsPreemptible && Expr == R_ABS)
677 G.Relocs.insert({&Sym, 0});
678 else if (Sym.IsPreemptible)
679 G.Global.insert({&Sym, 0});
680 else if (Expr == R_MIPS_GOT_OFF32)
681 G.Local32.insert({{&Sym, Addend}, 0});
683 G.Local16.insert({{&Sym, Addend}, 0});
686 void MipsGotSection::addDynTlsEntry(InputFile &File, Symbol &Sym) {
687 getGot(File).DynTlsSymbols.insert({&Sym, 0});
690 void MipsGotSection::addTlsIndex(InputFile &File) {
691 getGot(File).DynTlsSymbols.insert({nullptr, 0});
694 size_t MipsGotSection::FileGot::getEntriesNum() const {
695 return getPageEntriesNum() + Local16.size() + Global.size() + Relocs.size() +
696 Tls.size() + DynTlsSymbols.size() * 2;
699 size_t MipsGotSection::FileGot::getPageEntriesNum() const {
701 for (const std::pair<const OutputSection *, FileGot::PageBlock> &P : PagesMap)
702 Num += P.second.Count;
706 size_t MipsGotSection::FileGot::getIndexedEntriesNum() const {
707 size_t Count = getPageEntriesNum() + Local16.size() + Global.size();
708 // If there are relocation-only entries in the GOT, TLS entries
709 // are allocated after them. TLS entries should be addressable
710 // by 16-bit index so count both reloc-only and TLS entries.
711 if (!Tls.empty() || !DynTlsSymbols.empty())
712 Count += Relocs.size() + Tls.size() + DynTlsSymbols.size() * 2;
716 MipsGotSection::FileGot &MipsGotSection::getGot(InputFile &F) {
717 if (!F.MipsGotIndex.hasValue()) {
719 Gots.back().File = &F;
720 F.MipsGotIndex = Gots.size() - 1;
722 return Gots[*F.MipsGotIndex];
725 uint64_t MipsGotSection::getPageEntryOffset(const InputFile *F,
727 int64_t Addend) const {
728 const FileGot &G = Gots[*F->MipsGotIndex];
730 if (const OutputSection *OutSec = Sym.getOutputSection()) {
731 uint64_t SecAddr = getMipsPageAddr(OutSec->Addr);
732 uint64_t SymAddr = getMipsPageAddr(Sym.getVA(Addend));
733 Index = G.PagesMap.lookup(OutSec).FirstIndex + (SymAddr - SecAddr) / 0xffff;
735 Index = G.Local16.lookup({nullptr, getMipsPageAddr(Sym.getVA(Addend))});
737 return Index * Config->Wordsize;
740 uint64_t MipsGotSection::getSymEntryOffset(const InputFile *F, const Symbol &S,
741 int64_t Addend) const {
742 const FileGot &G = Gots[*F->MipsGotIndex];
743 Symbol *Sym = const_cast<Symbol *>(&S);
745 return G.Tls.lookup(Sym) * Config->Wordsize;
746 if (Sym->IsPreemptible)
747 return G.Global.lookup(Sym) * Config->Wordsize;
748 return G.Local16.lookup({Sym, Addend}) * Config->Wordsize;
751 uint64_t MipsGotSection::getTlsIndexOffset(const InputFile *F) const {
752 const FileGot &G = Gots[*F->MipsGotIndex];
753 return G.DynTlsSymbols.lookup(nullptr) * Config->Wordsize;
756 uint64_t MipsGotSection::getGlobalDynOffset(const InputFile *F,
757 const Symbol &S) const {
758 const FileGot &G = Gots[*F->MipsGotIndex];
759 Symbol *Sym = const_cast<Symbol *>(&S);
760 return G.DynTlsSymbols.lookup(Sym) * Config->Wordsize;
763 const Symbol *MipsGotSection::getFirstGlobalEntry() const {
766 const FileGot &PrimGot = Gots.front();
767 if (!PrimGot.Global.empty())
768 return PrimGot.Global.front().first;
769 if (!PrimGot.Relocs.empty())
770 return PrimGot.Relocs.front().first;
774 unsigned MipsGotSection::getLocalEntriesNum() const {
776 return HeaderEntriesNum;
777 return HeaderEntriesNum + Gots.front().getPageEntriesNum() +
778 Gots.front().Local16.size();
781 bool MipsGotSection::tryMergeGots(FileGot &Dst, FileGot &Src, bool IsPrimary) {
783 set_union(Tmp.PagesMap, Src.PagesMap);
784 set_union(Tmp.Local16, Src.Local16);
785 set_union(Tmp.Global, Src.Global);
786 set_union(Tmp.Relocs, Src.Relocs);
787 set_union(Tmp.Tls, Src.Tls);
788 set_union(Tmp.DynTlsSymbols, Src.DynTlsSymbols);
790 size_t Count = IsPrimary ? HeaderEntriesNum : 0;
791 Count += Tmp.getIndexedEntriesNum();
793 if (Count * Config->Wordsize > Config->MipsGotSize)
800 void MipsGotSection::finalizeContents() { updateAllocSize(); }
802 bool MipsGotSection::updateAllocSize() {
803 Size = HeaderEntriesNum * Config->Wordsize;
804 for (const FileGot &G : Gots)
805 Size += G.getEntriesNum() * Config->Wordsize;
809 template <class ELFT> void MipsGotSection::build() {
813 std::vector<FileGot> MergedGots(1);
815 // For each GOT move non-preemptible symbols from the `Global`
816 // to `Local16` list. Preemptible symbol might become non-preemptible
817 // one if, for example, it gets a related copy relocation.
818 for (FileGot &Got : Gots) {
819 for (auto &P: Got.Global)
820 if (!P.first->IsPreemptible)
821 Got.Local16.insert({{P.first, 0}, 0});
822 Got.Global.remove_if([&](const std::pair<Symbol *, size_t> &P) {
823 return !P.first->IsPreemptible;
827 // For each GOT remove "reloc-only" entry if there is "global"
828 // entry for the same symbol. And add local entries which indexed
829 // using 32-bit value at the end of 16-bit entries.
830 for (FileGot &Got : Gots) {
831 Got.Relocs.remove_if([&](const std::pair<Symbol *, size_t> &P) {
832 return Got.Global.count(P.first);
834 set_union(Got.Local16, Got.Local32);
838 // Evaluate number of "reloc-only" entries in the resulting GOT.
839 // To do that put all unique "reloc-only" and "global" entries
840 // from all GOTs to the future primary GOT.
841 FileGot *PrimGot = &MergedGots.front();
842 for (FileGot &Got : Gots) {
843 set_union(PrimGot->Relocs, Got.Global);
844 set_union(PrimGot->Relocs, Got.Relocs);
848 // Evaluate number of "page" entries in each GOT.
849 for (FileGot &Got : Gots) {
850 for (std::pair<const OutputSection *, FileGot::PageBlock> &P :
852 const OutputSection *OS = P.first;
853 uint64_t SecSize = 0;
854 for (BaseCommand *Cmd : OS->SectionCommands) {
855 if (auto *ISD = dyn_cast<InputSectionDescription>(Cmd))
856 for (InputSection *IS : ISD->Sections) {
857 uint64_t Off = alignTo(SecSize, IS->Alignment);
858 SecSize = Off + IS->getSize();
861 P.second.Count = getMipsPageCount(SecSize);
865 // Merge GOTs. Try to join as much as possible GOTs but do not exceed
866 // maximum GOT size. At first, try to fill the primary GOT because
867 // the primary GOT can be accessed in the most effective way. If it
868 // is not possible, try to fill the last GOT in the list, and finally
869 // create a new GOT if both attempts failed.
870 for (FileGot &SrcGot : Gots) {
871 InputFile *File = SrcGot.File;
872 if (tryMergeGots(MergedGots.front(), SrcGot, true)) {
873 File->MipsGotIndex = 0;
875 // If this is the first time we failed to merge with the primary GOT,
876 // MergedGots.back() will also be the primary GOT. We must make sure not
877 // to try to merge again with IsPrimary=false, as otherwise, if the
878 // inputs are just right, we could allow the primary GOT to become 1 or 2
879 // words too big due to ignoring the header size.
880 if (MergedGots.size() == 1 ||
881 !tryMergeGots(MergedGots.back(), SrcGot, false)) {
882 MergedGots.emplace_back();
883 std::swap(MergedGots.back(), SrcGot);
885 File->MipsGotIndex = MergedGots.size() - 1;
888 std::swap(Gots, MergedGots);
890 // Reduce number of "reloc-only" entries in the primary GOT
891 // by substracting "global" entries exist in the primary GOT.
892 PrimGot = &Gots.front();
893 PrimGot->Relocs.remove_if([&](const std::pair<Symbol *, size_t> &P) {
894 return PrimGot->Global.count(P.first);
897 // Calculate indexes for each GOT entry.
898 size_t Index = HeaderEntriesNum;
899 for (FileGot &Got : Gots) {
900 Got.StartIndex = &Got == PrimGot ? 0 : Index;
901 for (std::pair<const OutputSection *, FileGot::PageBlock> &P :
903 // For each output section referenced by GOT page relocations calculate
904 // and save into PagesMap an upper bound of MIPS GOT entries required
905 // to store page addresses of local symbols. We assume the worst case -
906 // each 64kb page of the output section has at least one GOT relocation
907 // against it. And take in account the case when the section intersects
909 P.second.FirstIndex = Index;
910 Index += P.second.Count;
912 for (auto &P: Got.Local16)
914 for (auto &P: Got.Global)
916 for (auto &P: Got.Relocs)
918 for (auto &P: Got.Tls)
920 for (auto &P: Got.DynTlsSymbols) {
926 // Update Symbol::GotIndex field to use this
927 // value later in the `sortMipsSymbols` function.
928 for (auto &P : PrimGot->Global)
929 P.first->GotIndex = P.second;
930 for (auto &P : PrimGot->Relocs)
931 P.first->GotIndex = P.second;
933 // Create dynamic relocations.
934 for (FileGot &Got : Gots) {
935 // Create dynamic relocations for TLS entries.
936 for (std::pair<Symbol *, size_t> &P : Got.Tls) {
938 uint64_t Offset = P.second * Config->Wordsize;
939 if (S->IsPreemptible)
940 InX::RelaDyn->addReloc(Target->TlsGotRel, this, Offset, S);
942 for (std::pair<Symbol *, size_t> &P : Got.DynTlsSymbols) {
944 uint64_t Offset = P.second * Config->Wordsize;
948 InX::RelaDyn->addReloc(Target->TlsModuleIndexRel, this, Offset, S);
950 // When building a shared library we still need a dynamic relocation
951 // for the module index. Therefore only checking for
952 // S->IsPreemptible is not sufficient (this happens e.g. for
953 // thread-locals that have been marked as local through a linker script)
954 if (!S->IsPreemptible && !Config->Pic)
956 InX::RelaDyn->addReloc(Target->TlsModuleIndexRel, this, Offset, S);
957 // However, we can skip writing the TLS offset reloc for non-preemptible
958 // symbols since it is known even in shared libraries
959 if (!S->IsPreemptible)
961 Offset += Config->Wordsize;
962 InX::RelaDyn->addReloc(Target->TlsOffsetRel, this, Offset, S);
966 // Do not create dynamic relocations for non-TLS
967 // entries in the primary GOT.
971 // Dynamic relocations for "global" entries.
972 for (const std::pair<Symbol *, size_t> &P : Got.Global) {
973 uint64_t Offset = P.second * Config->Wordsize;
974 InX::RelaDyn->addReloc(Target->RelativeRel, this, Offset, P.first);
978 // Dynamic relocations for "local" entries in case of PIC.
979 for (const std::pair<const OutputSection *, FileGot::PageBlock> &L :
981 size_t PageCount = L.second.Count;
982 for (size_t PI = 0; PI < PageCount; ++PI) {
983 uint64_t Offset = (L.second.FirstIndex + PI) * Config->Wordsize;
984 InX::RelaDyn->addReloc({Target->RelativeRel, this, Offset, L.first,
985 int64_t(PI * 0x10000)});
988 for (const std::pair<GotEntry, size_t> &P : Got.Local16) {
989 uint64_t Offset = P.second * Config->Wordsize;
990 InX::RelaDyn->addReloc({Target->RelativeRel, this, Offset, true,
991 P.first.first, P.first.second});
996 bool MipsGotSection::empty() const {
997 // We add the .got section to the result for dynamic MIPS target because
998 // its address and properties are mentioned in the .dynamic section.
999 return Config->Relocatable;
1002 uint64_t MipsGotSection::getGp(const InputFile *F) const {
1003 // For files without related GOT or files refer a primary GOT
1004 // returns "common" _gp value. For secondary GOTs calculate
1005 // individual _gp values.
1006 if (!F || !F->MipsGotIndex.hasValue() || *F->MipsGotIndex == 0)
1007 return ElfSym::MipsGp->getVA(0);
1008 return getVA() + Gots[*F->MipsGotIndex].StartIndex * Config->Wordsize +
1012 void MipsGotSection::writeTo(uint8_t *Buf) {
1013 // Set the MSB of the second GOT slot. This is not required by any
1014 // MIPS ABI documentation, though.
1016 // There is a comment in glibc saying that "The MSB of got[1] of a
1017 // gnu object is set to identify gnu objects," and in GNU gold it
1018 // says "the second entry will be used by some runtime loaders".
1019 // But how this field is being used is unclear.
1021 // We are not really willing to mimic other linkers behaviors
1022 // without understanding why they do that, but because all files
1023 // generated by GNU tools have this special GOT value, and because
1024 // we've been doing this for years, it is probably a safe bet to
1025 // keep doing this for now. We really need to revisit this to see
1026 // if we had to do this.
1027 writeUint(Buf + Config->Wordsize, (uint64_t)1 << (Config->Wordsize * 8 - 1));
1028 for (const FileGot &G : Gots) {
1029 auto Write = [&](size_t I, const Symbol *S, int64_t A) {
1033 if (S->StOther & STO_MIPS_MICROMIPS)
1036 writeUint(Buf + I * Config->Wordsize, VA);
1038 // Write 'page address' entries to the local part of the GOT.
1039 for (const std::pair<const OutputSection *, FileGot::PageBlock> &L :
1041 size_t PageCount = L.second.Count;
1042 uint64_t FirstPageAddr = getMipsPageAddr(L.first->Addr);
1043 for (size_t PI = 0; PI < PageCount; ++PI)
1044 Write(L.second.FirstIndex + PI, nullptr, FirstPageAddr + PI * 0x10000);
1046 // Local, global, TLS, reloc-only entries.
1047 // If TLS entry has a corresponding dynamic relocations, leave it
1048 // initialized by zero. Write down adjusted TLS symbol's values otherwise.
1049 // To calculate the adjustments use offsets for thread-local storage.
1050 // https://www.linux-mips.org/wiki/NPTL
1051 for (const std::pair<GotEntry, size_t> &P : G.Local16)
1052 Write(P.second, P.first.first, P.first.second);
1053 // Write VA to the primary GOT only. For secondary GOTs that
1054 // will be done by REL32 dynamic relocations.
1055 if (&G == &Gots.front())
1056 for (const std::pair<const Symbol *, size_t> &P : G.Global)
1057 Write(P.second, P.first, 0);
1058 for (const std::pair<Symbol *, size_t> &P : G.Relocs)
1059 Write(P.second, P.first, 0);
1060 for (const std::pair<Symbol *, size_t> &P : G.Tls)
1061 Write(P.second, P.first, P.first->IsPreemptible ? 0 : -0x7000);
1062 for (const std::pair<Symbol *, size_t> &P : G.DynTlsSymbols) {
1063 if (P.first == nullptr && !Config->Pic)
1064 Write(P.second, nullptr, 1);
1065 else if (P.first && !P.first->IsPreemptible) {
1066 // If we are emitting PIC code with relocations we mustn't write
1067 // anything to the GOT here. When using Elf_Rel relocations the value
1068 // one will be treated as an addend and will cause crashes at runtime
1070 Write(P.second, nullptr, 1);
1071 Write(P.second + 1, P.first, -0x8000);
1077 // On PowerPC the .plt section is used to hold the table of function addresses
1078 // instead of the .got.plt, and the type is SHT_NOBITS similar to a .bss
1079 // section. I don't know why we have a BSS style type for the section but it is
1080 // consitent across both 64-bit PowerPC ABIs as well as the 32-bit PowerPC ABI.
1081 GotPltSection::GotPltSection()
1082 : SyntheticSection(SHF_ALLOC | SHF_WRITE,
1083 Config->EMachine == EM_PPC64 ? SHT_NOBITS : SHT_PROGBITS,
1084 Target->GotPltEntrySize,
1085 Config->EMachine == EM_PPC64 ? ".plt" : ".got.plt") {}
1087 void GotPltSection::addEntry(Symbol &Sym) {
1088 assert(Sym.PltIndex == Entries.size());
1089 Entries.push_back(&Sym);
1092 size_t GotPltSection::getSize() const {
1093 return (Target->GotPltHeaderEntriesNum + Entries.size()) *
1094 Target->GotPltEntrySize;
1097 void GotPltSection::writeTo(uint8_t *Buf) {
1098 Target->writeGotPltHeader(Buf);
1099 Buf += Target->GotPltHeaderEntriesNum * Target->GotPltEntrySize;
1100 for (const Symbol *B : Entries) {
1101 Target->writeGotPlt(Buf, *B);
1102 Buf += Config->Wordsize;
1106 bool GotPltSection::empty() const {
1107 // We need to emit a GOT.PLT even if it's empty if there's a symbol that
1108 // references the _GLOBAL_OFFSET_TABLE_ and the Target defines the symbol
1109 // relative to the .got.plt section.
1110 return Entries.empty() &&
1111 !(ElfSym::GlobalOffsetTable && Target->GotBaseSymInGotPlt);
1114 static StringRef getIgotPltName() {
1115 // On ARM the IgotPltSection is part of the GotSection.
1116 if (Config->EMachine == EM_ARM)
1119 // On PowerPC64 the GotPltSection is renamed to '.plt' so the IgotPltSection
1120 // needs to be named the same.
1121 if (Config->EMachine == EM_PPC64)
1127 // On PowerPC64 the GotPltSection type is SHT_NOBITS so we have to follow suit
1128 // with the IgotPltSection.
1129 IgotPltSection::IgotPltSection()
1130 : SyntheticSection(SHF_ALLOC | SHF_WRITE,
1131 Config->EMachine == EM_PPC64 ? SHT_NOBITS : SHT_PROGBITS,
1132 Target->GotPltEntrySize, getIgotPltName()) {}
1134 void IgotPltSection::addEntry(Symbol &Sym) {
1135 Sym.IsInIgot = true;
1136 assert(Sym.PltIndex == Entries.size());
1137 Entries.push_back(&Sym);
1140 size_t IgotPltSection::getSize() const {
1141 return Entries.size() * Target->GotPltEntrySize;
1144 void IgotPltSection::writeTo(uint8_t *Buf) {
1145 for (const Symbol *B : Entries) {
1146 Target->writeIgotPlt(Buf, *B);
1147 Buf += Config->Wordsize;
1151 StringTableSection::StringTableSection(StringRef Name, bool Dynamic)
1152 : SyntheticSection(Dynamic ? (uint64_t)SHF_ALLOC : 0, SHT_STRTAB, 1, Name),
1154 // ELF string tables start with a NUL byte.
1158 // Adds a string to the string table. If HashIt is true we hash and check for
1159 // duplicates. It is optional because the name of global symbols are already
1160 // uniqued and hashing them again has a big cost for a small value: uniquing
1161 // them with some other string that happens to be the same.
1162 unsigned StringTableSection::addString(StringRef S, bool HashIt) {
1164 auto R = StringMap.insert(std::make_pair(S, this->Size));
1166 return R.first->second;
1168 unsigned Ret = this->Size;
1169 this->Size = this->Size + S.size() + 1;
1170 Strings.push_back(S);
1174 void StringTableSection::writeTo(uint8_t *Buf) {
1175 for (StringRef S : Strings) {
1176 memcpy(Buf, S.data(), S.size());
1177 Buf[S.size()] = '\0';
1178 Buf += S.size() + 1;
1182 // Returns the number of version definition entries. Because the first entry
1183 // is for the version definition itself, it is the number of versioned symbols
1184 // plus one. Note that we don't support multiple versions yet.
1185 static unsigned getVerDefNum() { return Config->VersionDefinitions.size() + 1; }
1187 template <class ELFT>
1188 DynamicSection<ELFT>::DynamicSection()
1189 : SyntheticSection(SHF_ALLOC | SHF_WRITE, SHT_DYNAMIC, Config->Wordsize,
1191 this->Entsize = ELFT::Is64Bits ? 16 : 8;
1193 // .dynamic section is not writable on MIPS and on Fuchsia OS
1194 // which passes -z rodynamic.
1195 // See "Special Section" in Chapter 4 in the following document:
1196 // ftp://www.linux-mips.org/pub/linux/mips/doc/ABI/mipsabi.pdf
1197 if (Config->EMachine == EM_MIPS || Config->ZRodynamic)
1198 this->Flags = SHF_ALLOC;
1200 // Add strings to .dynstr early so that .dynstr's size will be
1202 for (StringRef S : Config->FilterList)
1203 addInt(DT_FILTER, InX::DynStrTab->addString(S));
1204 for (StringRef S : Config->AuxiliaryList)
1205 addInt(DT_AUXILIARY, InX::DynStrTab->addString(S));
1207 if (!Config->Rpath.empty())
1208 addInt(Config->EnableNewDtags ? DT_RUNPATH : DT_RPATH,
1209 InX::DynStrTab->addString(Config->Rpath));
1211 for (InputFile *File : SharedFiles) {
1212 SharedFile<ELFT> *F = cast<SharedFile<ELFT>>(File);
1214 addInt(DT_NEEDED, InX::DynStrTab->addString(F->SoName));
1216 if (!Config->SoName.empty())
1217 addInt(DT_SONAME, InX::DynStrTab->addString(Config->SoName));
1220 template <class ELFT>
1221 void DynamicSection<ELFT>::add(int32_t Tag, std::function<uint64_t()> Fn) {
1222 Entries.push_back({Tag, Fn});
1225 template <class ELFT>
1226 void DynamicSection<ELFT>::addInt(int32_t Tag, uint64_t Val) {
1227 Entries.push_back({Tag, [=] { return Val; }});
1230 template <class ELFT>
1231 void DynamicSection<ELFT>::addInSec(int32_t Tag, InputSection *Sec) {
1232 Entries.push_back({Tag, [=] { return Sec->getVA(0); }});
1235 template <class ELFT>
1236 void DynamicSection<ELFT>::addInSecRelative(int32_t Tag, InputSection *Sec) {
1237 size_t TagOffset = Entries.size() * Entsize;
1239 {Tag, [=] { return Sec->getVA(0) - (getVA() + TagOffset); }});
1242 template <class ELFT>
1243 void DynamicSection<ELFT>::addOutSec(int32_t Tag, OutputSection *Sec) {
1244 Entries.push_back({Tag, [=] { return Sec->Addr; }});
1247 template <class ELFT>
1248 void DynamicSection<ELFT>::addSize(int32_t Tag, OutputSection *Sec) {
1249 Entries.push_back({Tag, [=] { return Sec->Size; }});
1252 template <class ELFT>
1253 void DynamicSection<ELFT>::addSym(int32_t Tag, Symbol *Sym) {
1254 Entries.push_back({Tag, [=] { return Sym->getVA(); }});
1257 // Add remaining entries to complete .dynamic contents.
1258 template <class ELFT> void DynamicSection<ELFT>::finalizeContents() {
1260 return; // Already finalized.
1262 // Set DT_FLAGS and DT_FLAGS_1.
1263 uint32_t DtFlags = 0;
1264 uint32_t DtFlags1 = 0;
1265 if (Config->Bsymbolic)
1266 DtFlags |= DF_SYMBOLIC;
1267 if (Config->ZInitfirst)
1268 DtFlags1 |= DF_1_INITFIRST;
1269 if (Config->ZNodelete)
1270 DtFlags1 |= DF_1_NODELETE;
1271 if (Config->ZNodlopen)
1272 DtFlags1 |= DF_1_NOOPEN;
1274 DtFlags |= DF_BIND_NOW;
1275 DtFlags1 |= DF_1_NOW;
1277 if (Config->ZOrigin) {
1278 DtFlags |= DF_ORIGIN;
1279 DtFlags1 |= DF_1_ORIGIN;
1282 DtFlags |= DF_TEXTREL;
1285 addInt(DT_FLAGS, DtFlags);
1287 addInt(DT_FLAGS_1, DtFlags1);
1289 // DT_DEBUG is a pointer to debug informaion used by debuggers at runtime. We
1290 // need it for each process, so we don't write it for DSOs. The loader writes
1291 // the pointer into this entry.
1293 // DT_DEBUG is the only .dynamic entry that needs to be written to. Some
1294 // systems (currently only Fuchsia OS) provide other means to give the
1295 // debugger this information. Such systems may choose make .dynamic read-only.
1296 // If the target is such a system (used -z rodynamic) don't write DT_DEBUG.
1297 if (!Config->Shared && !Config->Relocatable && !Config->ZRodynamic)
1298 addInt(DT_DEBUG, 0);
1300 this->Link = InX::DynStrTab->getParent()->SectionIndex;
1301 if (!InX::RelaDyn->empty()) {
1302 addInSec(InX::RelaDyn->DynamicTag, InX::RelaDyn);
1303 addSize(InX::RelaDyn->SizeDynamicTag, InX::RelaDyn->getParent());
1305 bool IsRela = Config->IsRela;
1306 addInt(IsRela ? DT_RELAENT : DT_RELENT,
1307 IsRela ? sizeof(Elf_Rela) : sizeof(Elf_Rel));
1309 // MIPS dynamic loader does not support RELCOUNT tag.
1310 // The problem is in the tight relation between dynamic
1311 // relocations and GOT. So do not emit this tag on MIPS.
1312 if (Config->EMachine != EM_MIPS) {
1313 size_t NumRelativeRels = InX::RelaDyn->getRelativeRelocCount();
1314 if (Config->ZCombreloc && NumRelativeRels)
1315 addInt(IsRela ? DT_RELACOUNT : DT_RELCOUNT, NumRelativeRels);
1318 if (InX::RelrDyn && !InX::RelrDyn->Relocs.empty()) {
1319 addInSec(Config->UseAndroidRelrTags ? DT_ANDROID_RELR : DT_RELR,
1321 addSize(Config->UseAndroidRelrTags ? DT_ANDROID_RELRSZ : DT_RELRSZ,
1322 InX::RelrDyn->getParent());
1323 addInt(Config->UseAndroidRelrTags ? DT_ANDROID_RELRENT : DT_RELRENT,
1326 // .rel[a].plt section usually consists of two parts, containing plt and
1327 // iplt relocations. It is possible to have only iplt relocations in the
1328 // output. In that case RelaPlt is empty and have zero offset, the same offset
1329 // as RelaIplt have. And we still want to emit proper dynamic tags for that
1330 // case, so here we always use RelaPlt as marker for the begining of
1331 // .rel[a].plt section.
1332 if (InX::RelaPlt->getParent()->Live) {
1333 addInSec(DT_JMPREL, InX::RelaPlt);
1334 addSize(DT_PLTRELSZ, InX::RelaPlt->getParent());
1335 switch (Config->EMachine) {
1337 addInSec(DT_MIPS_PLTGOT, InX::GotPlt);
1340 addInSec(DT_PLTGOT, InX::Plt);
1343 addInSec(DT_PLTGOT, InX::GotPlt);
1346 addInt(DT_PLTREL, Config->IsRela ? DT_RELA : DT_REL);
1349 addInSec(DT_SYMTAB, InX::DynSymTab);
1350 addInt(DT_SYMENT, sizeof(Elf_Sym));
1351 addInSec(DT_STRTAB, InX::DynStrTab);
1352 addInt(DT_STRSZ, InX::DynStrTab->getSize());
1354 addInt(DT_TEXTREL, 0);
1355 if (InX::GnuHashTab)
1356 addInSec(DT_GNU_HASH, InX::GnuHashTab);
1358 addInSec(DT_HASH, InX::HashTab);
1360 if (Out::PreinitArray) {
1361 addOutSec(DT_PREINIT_ARRAY, Out::PreinitArray);
1362 addSize(DT_PREINIT_ARRAYSZ, Out::PreinitArray);
1364 if (Out::InitArray) {
1365 addOutSec(DT_INIT_ARRAY, Out::InitArray);
1366 addSize(DT_INIT_ARRAYSZ, Out::InitArray);
1368 if (Out::FiniArray) {
1369 addOutSec(DT_FINI_ARRAY, Out::FiniArray);
1370 addSize(DT_FINI_ARRAYSZ, Out::FiniArray);
1373 if (Symbol *B = Symtab->find(Config->Init))
1376 if (Symbol *B = Symtab->find(Config->Fini))
1380 bool HasVerNeed = In<ELFT>::VerNeed->getNeedNum() != 0;
1381 if (HasVerNeed || In<ELFT>::VerDef)
1382 addInSec(DT_VERSYM, In<ELFT>::VerSym);
1383 if (In<ELFT>::VerDef) {
1384 addInSec(DT_VERDEF, In<ELFT>::VerDef);
1385 addInt(DT_VERDEFNUM, getVerDefNum());
1388 addInSec(DT_VERNEED, In<ELFT>::VerNeed);
1389 addInt(DT_VERNEEDNUM, In<ELFT>::VerNeed->getNeedNum());
1392 if (Config->EMachine == EM_MIPS) {
1393 addInt(DT_MIPS_RLD_VERSION, 1);
1394 addInt(DT_MIPS_FLAGS, RHF_NOTPOT);
1395 addInt(DT_MIPS_BASE_ADDRESS, Target->getImageBase());
1396 addInt(DT_MIPS_SYMTABNO, InX::DynSymTab->getNumSymbols());
1398 add(DT_MIPS_LOCAL_GOTNO, [] { return InX::MipsGot->getLocalEntriesNum(); });
1400 if (const Symbol *B = InX::MipsGot->getFirstGlobalEntry())
1401 addInt(DT_MIPS_GOTSYM, B->DynsymIndex);
1403 addInt(DT_MIPS_GOTSYM, InX::DynSymTab->getNumSymbols());
1404 addInSec(DT_PLTGOT, InX::MipsGot);
1405 if (InX::MipsRldMap) {
1407 addInSec(DT_MIPS_RLD_MAP, InX::MipsRldMap);
1408 // Store the offset to the .rld_map section
1409 // relative to the address of the tag.
1410 addInSecRelative(DT_MIPS_RLD_MAP_REL, InX::MipsRldMap);
1414 // Glink dynamic tag is required by the V2 abi if the plt section isn't empty.
1415 if (Config->EMachine == EM_PPC64 && !InX::Plt->empty()) {
1416 // The Glink tag points to 32 bytes before the first lazy symbol resolution
1417 // stub, which starts directly after the header.
1418 Entries.push_back({DT_PPC64_GLINK, [=] {
1419 unsigned Offset = Target->PltHeaderSize - 32;
1420 return InX::Plt->getVA(0) + Offset;
1426 getParent()->Link = this->Link;
1427 this->Size = Entries.size() * this->Entsize;
1430 template <class ELFT> void DynamicSection<ELFT>::writeTo(uint8_t *Buf) {
1431 auto *P = reinterpret_cast<Elf_Dyn *>(Buf);
1433 for (std::pair<int32_t, std::function<uint64_t()>> &KV : Entries) {
1434 P->d_tag = KV.first;
1435 P->d_un.d_val = KV.second();
1440 uint64_t DynamicReloc::getOffset() const {
1441 return InputSec->getVA(OffsetInSec);
1444 int64_t DynamicReloc::computeAddend() const {
1446 return Sym->getVA(Addend);
1449 // See the comment in the DynamicReloc ctor.
1450 return getMipsPageAddr(OutputSec->Addr) + Addend;
1453 uint32_t DynamicReloc::getSymIndex() const {
1454 if (Sym && !UseSymVA)
1455 return Sym->DynsymIndex;
1459 RelocationBaseSection::RelocationBaseSection(StringRef Name, uint32_t Type,
1461 int32_t SizeDynamicTag)
1462 : SyntheticSection(SHF_ALLOC, Type, Config->Wordsize, Name),
1463 DynamicTag(DynamicTag), SizeDynamicTag(SizeDynamicTag) {}
1465 void RelocationBaseSection::addReloc(RelType DynType, InputSectionBase *IS,
1466 uint64_t OffsetInSec, Symbol *Sym) {
1467 addReloc({DynType, IS, OffsetInSec, false, Sym, 0});
1470 void RelocationBaseSection::addReloc(RelType DynType,
1471 InputSectionBase *InputSec,
1472 uint64_t OffsetInSec, Symbol *Sym,
1473 int64_t Addend, RelExpr Expr,
1475 // Write the addends to the relocated address if required. We skip
1476 // it if the written value would be zero.
1477 if (Config->WriteAddends && (Expr != R_ADDEND || Addend != 0))
1478 InputSec->Relocations.push_back({Expr, Type, OffsetInSec, Addend, Sym});
1479 addReloc({DynType, InputSec, OffsetInSec, Expr != R_ADDEND, Sym, Addend});
1482 void RelocationBaseSection::addReloc(const DynamicReloc &Reloc) {
1483 if (Reloc.Type == Target->RelativeRel)
1484 ++NumRelativeRelocs;
1485 Relocs.push_back(Reloc);
1488 void RelocationBaseSection::finalizeContents() {
1489 // If all relocations are R_*_RELATIVE they don't refer to any
1490 // dynamic symbol and we don't need a dynamic symbol table. If that
1491 // is the case, just use 0 as the link.
1492 Link = InX::DynSymTab ? InX::DynSymTab->getParent()->SectionIndex : 0;
1494 // Set required output section properties.
1495 getParent()->Link = Link;
1498 RelrBaseSection::RelrBaseSection()
1499 : SyntheticSection(SHF_ALLOC,
1500 Config->UseAndroidRelrTags ? SHT_ANDROID_RELR : SHT_RELR,
1501 Config->Wordsize, ".relr.dyn") {}
1503 template <class ELFT>
1504 static void encodeDynamicReloc(typename ELFT::Rela *P,
1505 const DynamicReloc &Rel) {
1507 P->r_addend = Rel.computeAddend();
1508 P->r_offset = Rel.getOffset();
1509 P->setSymbolAndType(Rel.getSymIndex(), Rel.Type, Config->IsMips64EL);
1512 template <class ELFT>
1513 RelocationSection<ELFT>::RelocationSection(StringRef Name, bool Sort)
1514 : RelocationBaseSection(Name, Config->IsRela ? SHT_RELA : SHT_REL,
1515 Config->IsRela ? DT_RELA : DT_REL,
1516 Config->IsRela ? DT_RELASZ : DT_RELSZ),
1518 this->Entsize = Config->IsRela ? sizeof(Elf_Rela) : sizeof(Elf_Rel);
1521 static bool compRelocations(const DynamicReloc &A, const DynamicReloc &B) {
1522 bool AIsRel = A.Type == Target->RelativeRel;
1523 bool BIsRel = B.Type == Target->RelativeRel;
1524 if (AIsRel != BIsRel)
1526 return A.getSymIndex() < B.getSymIndex();
1529 template <class ELFT> void RelocationSection<ELFT>::writeTo(uint8_t *Buf) {
1531 std::stable_sort(Relocs.begin(), Relocs.end(), compRelocations);
1533 for (const DynamicReloc &Rel : Relocs) {
1534 encodeDynamicReloc<ELFT>(reinterpret_cast<Elf_Rela *>(Buf), Rel);
1535 Buf += Config->IsRela ? sizeof(Elf_Rela) : sizeof(Elf_Rel);
1539 template <class ELFT> unsigned RelocationSection<ELFT>::getRelocOffset() {
1540 return this->Entsize * Relocs.size();
1543 template <class ELFT>
1544 AndroidPackedRelocationSection<ELFT>::AndroidPackedRelocationSection(
1546 : RelocationBaseSection(
1547 Name, Config->IsRela ? SHT_ANDROID_RELA : SHT_ANDROID_REL,
1548 Config->IsRela ? DT_ANDROID_RELA : DT_ANDROID_REL,
1549 Config->IsRela ? DT_ANDROID_RELASZ : DT_ANDROID_RELSZ) {
1553 template <class ELFT>
1554 bool AndroidPackedRelocationSection<ELFT>::updateAllocSize() {
1555 // This function computes the contents of an Android-format packed relocation
1558 // This format compresses relocations by using relocation groups to factor out
1559 // fields that are common between relocations and storing deltas from previous
1560 // relocations in SLEB128 format (which has a short representation for small
1561 // numbers). A good example of a relocation type with common fields is
1562 // R_*_RELATIVE, which is normally used to represent function pointers in
1563 // vtables. In the REL format, each relative relocation has the same r_info
1564 // field, and is only different from other relative relocations in terms of
1565 // the r_offset field. By sorting relocations by offset, grouping them by
1566 // r_info and representing each relocation with only the delta from the
1567 // previous offset, each 8-byte relocation can be compressed to as little as 1
1568 // byte (or less with run-length encoding). This relocation packer was able to
1569 // reduce the size of the relocation section in an Android Chromium DSO from
1570 // 2,911,184 bytes to 174,693 bytes, or 6% of the original size.
1572 // A relocation section consists of a header containing the literal bytes
1573 // 'APS2' followed by a sequence of SLEB128-encoded integers. The first two
1574 // elements are the total number of relocations in the section and an initial
1575 // r_offset value. The remaining elements define a sequence of relocation
1576 // groups. Each relocation group starts with a header consisting of the
1577 // following elements:
1579 // - the number of relocations in the relocation group
1580 // - flags for the relocation group
1581 // - (if RELOCATION_GROUPED_BY_OFFSET_DELTA_FLAG is set) the r_offset delta
1582 // for each relocation in the group.
1583 // - (if RELOCATION_GROUPED_BY_INFO_FLAG is set) the value of the r_info
1584 // field for each relocation in the group.
1585 // - (if RELOCATION_GROUP_HAS_ADDEND_FLAG and
1586 // RELOCATION_GROUPED_BY_ADDEND_FLAG are set) the r_addend delta for
1587 // each relocation in the group.
1589 // Following the relocation group header are descriptions of each of the
1590 // relocations in the group. They consist of the following elements:
1592 // - (if RELOCATION_GROUPED_BY_OFFSET_DELTA_FLAG is not set) the r_offset
1593 // delta for this relocation.
1594 // - (if RELOCATION_GROUPED_BY_INFO_FLAG is not set) the value of the r_info
1595 // field for this relocation.
1596 // - (if RELOCATION_GROUP_HAS_ADDEND_FLAG is set and
1597 // RELOCATION_GROUPED_BY_ADDEND_FLAG is not set) the r_addend delta for
1600 size_t OldSize = RelocData.size();
1602 RelocData = {'A', 'P', 'S', '2'};
1603 raw_svector_ostream OS(RelocData);
1604 auto Add = [&](int64_t V) { encodeSLEB128(V, OS); };
1606 // The format header includes the number of relocations and the initial
1607 // offset (we set this to zero because the first relocation group will
1608 // perform the initial adjustment).
1612 std::vector<Elf_Rela> Relatives, NonRelatives;
1614 for (const DynamicReloc &Rel : Relocs) {
1616 encodeDynamicReloc<ELFT>(&R, Rel);
1618 if (R.getType(Config->IsMips64EL) == Target->RelativeRel)
1619 Relatives.push_back(R);
1621 NonRelatives.push_back(R);
1624 llvm::sort(Relatives.begin(), Relatives.end(),
1625 [](const Elf_Rel &A, const Elf_Rel &B) {
1626 return A.r_offset < B.r_offset;
1629 // Try to find groups of relative relocations which are spaced one word
1630 // apart from one another. These generally correspond to vtable entries. The
1631 // format allows these groups to be encoded using a sort of run-length
1632 // encoding, but each group will cost 7 bytes in addition to the offset from
1633 // the previous group, so it is only profitable to do this for groups of
1634 // size 8 or larger.
1635 std::vector<Elf_Rela> UngroupedRelatives;
1636 std::vector<std::vector<Elf_Rela>> RelativeGroups;
1637 for (auto I = Relatives.begin(), E = Relatives.end(); I != E;) {
1638 std::vector<Elf_Rela> Group;
1640 Group.push_back(*I++);
1641 } while (I != E && (I - 1)->r_offset + Config->Wordsize == I->r_offset);
1643 if (Group.size() < 8)
1644 UngroupedRelatives.insert(UngroupedRelatives.end(), Group.begin(),
1647 RelativeGroups.emplace_back(std::move(Group));
1650 unsigned HasAddendIfRela =
1651 Config->IsRela ? RELOCATION_GROUP_HAS_ADDEND_FLAG : 0;
1653 uint64_t Offset = 0;
1654 uint64_t Addend = 0;
1656 // Emit the run-length encoding for the groups of adjacent relative
1657 // relocations. Each group is represented using two groups in the packed
1658 // format. The first is used to set the current offset to the start of the
1659 // group (and also encodes the first relocation), and the second encodes the
1660 // remaining relocations.
1661 for (std::vector<Elf_Rela> &G : RelativeGroups) {
1662 // The first relocation in the group.
1664 Add(RELOCATION_GROUPED_BY_OFFSET_DELTA_FLAG |
1665 RELOCATION_GROUPED_BY_INFO_FLAG | HasAddendIfRela);
1666 Add(G[0].r_offset - Offset);
1667 Add(Target->RelativeRel);
1668 if (Config->IsRela) {
1669 Add(G[0].r_addend - Addend);
1670 Addend = G[0].r_addend;
1673 // The remaining relocations.
1675 Add(RELOCATION_GROUPED_BY_OFFSET_DELTA_FLAG |
1676 RELOCATION_GROUPED_BY_INFO_FLAG | HasAddendIfRela);
1677 Add(Config->Wordsize);
1678 Add(Target->RelativeRel);
1679 if (Config->IsRela) {
1680 for (auto I = G.begin() + 1, E = G.end(); I != E; ++I) {
1681 Add(I->r_addend - Addend);
1682 Addend = I->r_addend;
1686 Offset = G.back().r_offset;
1689 // Now the ungrouped relatives.
1690 if (!UngroupedRelatives.empty()) {
1691 Add(UngroupedRelatives.size());
1692 Add(RELOCATION_GROUPED_BY_INFO_FLAG | HasAddendIfRela);
1693 Add(Target->RelativeRel);
1694 for (Elf_Rela &R : UngroupedRelatives) {
1695 Add(R.r_offset - Offset);
1696 Offset = R.r_offset;
1697 if (Config->IsRela) {
1698 Add(R.r_addend - Addend);
1699 Addend = R.r_addend;
1704 // Finally the non-relative relocations.
1705 llvm::sort(NonRelatives.begin(), NonRelatives.end(),
1706 [](const Elf_Rela &A, const Elf_Rela &B) {
1707 return A.r_offset < B.r_offset;
1709 if (!NonRelatives.empty()) {
1710 Add(NonRelatives.size());
1711 Add(HasAddendIfRela);
1712 for (Elf_Rela &R : NonRelatives) {
1713 Add(R.r_offset - Offset);
1714 Offset = R.r_offset;
1716 if (Config->IsRela) {
1717 Add(R.r_addend - Addend);
1718 Addend = R.r_addend;
1723 // Returns whether the section size changed. We need to keep recomputing both
1724 // section layout and the contents of this section until the size converges
1725 // because changing this section's size can affect section layout, which in
1726 // turn can affect the sizes of the LEB-encoded integers stored in this
1728 return RelocData.size() != OldSize;
1731 template <class ELFT> RelrSection<ELFT>::RelrSection() {
1732 this->Entsize = Config->Wordsize;
1735 template <class ELFT> bool RelrSection<ELFT>::updateAllocSize() {
1736 // This function computes the contents of an SHT_RELR packed relocation
1739 // Proposal for adding SHT_RELR sections to generic-abi is here:
1740 // https://groups.google.com/forum/#!topic/generic-abi/bX460iggiKg
1742 // The encoded sequence of Elf64_Relr entries in a SHT_RELR section looks
1743 // like [ AAAAAAAA BBBBBBB1 BBBBBBB1 ... AAAAAAAA BBBBBB1 ... ]
1745 // i.e. start with an address, followed by any number of bitmaps. The address
1746 // entry encodes 1 relocation. The subsequent bitmap entries encode up to 63
1747 // relocations each, at subsequent offsets following the last address entry.
1749 // The bitmap entries must have 1 in the least significant bit. The assumption
1750 // here is that an address cannot have 1 in lsb. Odd addresses are not
1753 // Excluding the least significant bit in the bitmap, each non-zero bit in
1754 // the bitmap represents a relocation to be applied to a corresponding machine
1755 // word that follows the base address word. The second least significant bit
1756 // represents the machine word immediately following the initial address, and
1757 // each bit that follows represents the next word, in linear order. As such,
1758 // a single bitmap can encode up to 31 relocations in a 32-bit object, and
1759 // 63 relocations in a 64-bit object.
1761 // This encoding has a couple of interesting properties:
1762 // 1. Looking at any entry, it is clear whether it's an address or a bitmap:
1763 // even means address, odd means bitmap.
1764 // 2. Just a simple list of addresses is a valid encoding.
1766 size_t OldSize = RelrRelocs.size();
1769 // Same as Config->Wordsize but faster because this is a compile-time
1771 const size_t Wordsize = sizeof(typename ELFT::uint);
1773 // Number of bits to use for the relocation offsets bitmap.
1774 // Must be either 63 or 31.
1775 const size_t NBits = Wordsize * 8 - 1;
1777 // Get offsets for all relative relocations and sort them.
1778 std::vector<uint64_t> Offsets;
1779 for (const RelativeReloc &Rel : Relocs)
1780 Offsets.push_back(Rel.getOffset());
1781 llvm::sort(Offsets.begin(), Offsets.end());
1783 // For each leading relocation, find following ones that can be folded
1784 // as a bitmap and fold them.
1785 for (size_t I = 0, E = Offsets.size(); I < E;) {
1786 // Add a leading relocation.
1787 RelrRelocs.push_back(Elf_Relr(Offsets[I]));
1788 uint64_t Base = Offsets[I] + Wordsize;
1791 // Find foldable relocations to construct bitmaps.
1793 uint64_t Bitmap = 0;
1796 uint64_t Delta = Offsets[I] - Base;
1798 // If it is too far, it cannot be folded.
1799 if (Delta >= NBits * Wordsize)
1802 // If it is not a multiple of wordsize away, it cannot be folded.
1803 if (Delta % Wordsize)
1807 Bitmap |= 1ULL << (Delta / Wordsize);
1814 RelrRelocs.push_back(Elf_Relr((Bitmap << 1) | 1));
1815 Base += NBits * Wordsize;
1819 return RelrRelocs.size() != OldSize;
1822 SymbolTableBaseSection::SymbolTableBaseSection(StringTableSection &StrTabSec)
1823 : SyntheticSection(StrTabSec.isDynamic() ? (uint64_t)SHF_ALLOC : 0,
1824 StrTabSec.isDynamic() ? SHT_DYNSYM : SHT_SYMTAB,
1826 StrTabSec.isDynamic() ? ".dynsym" : ".symtab"),
1827 StrTabSec(StrTabSec) {}
1829 // Orders symbols according to their positions in the GOT,
1830 // in compliance with MIPS ABI rules.
1831 // See "Global Offset Table" in Chapter 5 in the following document
1832 // for detailed description:
1833 // ftp://www.linux-mips.org/pub/linux/mips/doc/ABI/mipsabi.pdf
1834 static bool sortMipsSymbols(const SymbolTableEntry &L,
1835 const SymbolTableEntry &R) {
1836 // Sort entries related to non-local preemptible symbols by GOT indexes.
1837 // All other entries go to the beginning of a dynsym in arbitrary order.
1838 if (L.Sym->isInGot() && R.Sym->isInGot())
1839 return L.Sym->GotIndex < R.Sym->GotIndex;
1840 if (!L.Sym->isInGot() && !R.Sym->isInGot())
1842 return !L.Sym->isInGot();
1845 void SymbolTableBaseSection::finalizeContents() {
1846 getParent()->Link = StrTabSec.getParent()->SectionIndex;
1848 if (this->Type != SHT_DYNSYM)
1851 // If it is a .dynsym, there should be no local symbols, but we need
1852 // to do a few things for the dynamic linker.
1854 // Section's Info field has the index of the first non-local symbol.
1855 // Because the first symbol entry is a null entry, 1 is the first.
1856 getParent()->Info = 1;
1858 if (InX::GnuHashTab) {
1859 // NB: It also sorts Symbols to meet the GNU hash table requirements.
1860 InX::GnuHashTab->addSymbols(Symbols);
1861 } else if (Config->EMachine == EM_MIPS) {
1862 std::stable_sort(Symbols.begin(), Symbols.end(), sortMipsSymbols);
1866 for (const SymbolTableEntry &S : Symbols)
1867 S.Sym->DynsymIndex = ++I;
1870 // The ELF spec requires that all local symbols precede global symbols, so we
1871 // sort symbol entries in this function. (For .dynsym, we don't do that because
1872 // symbols for dynamic linking are inherently all globals.)
1874 // Aside from above, we put local symbols in groups starting with the STT_FILE
1875 // symbol. That is convenient for purpose of identifying where are local symbols
1877 void SymbolTableBaseSection::postThunkContents() {
1878 assert(this->Type == SHT_SYMTAB);
1880 // Move all local symbols before global symbols.
1881 auto E = std::stable_partition(
1882 Symbols.begin(), Symbols.end(), [](const SymbolTableEntry &S) {
1883 return S.Sym->isLocal() || S.Sym->computeBinding() == STB_LOCAL;
1885 size_t NumLocals = E - Symbols.begin();
1886 getParent()->Info = NumLocals + 1;
1888 // We want to group the local symbols by file. For that we rebuild the local
1889 // part of the symbols vector. We do not need to care about the STT_FILE
1890 // symbols, they are already naturally placed first in each group. That
1891 // happens because STT_FILE is always the first symbol in the object and hence
1892 // precede all other local symbols we add for a file.
1893 MapVector<InputFile *, std::vector<SymbolTableEntry>> Arr;
1894 for (const SymbolTableEntry &S : llvm::make_range(Symbols.begin(), E))
1895 Arr[S.Sym->File].push_back(S);
1897 auto I = Symbols.begin();
1898 for (std::pair<InputFile *, std::vector<SymbolTableEntry>> &P : Arr)
1899 for (SymbolTableEntry &Entry : P.second)
1903 void SymbolTableBaseSection::addSymbol(Symbol *B) {
1904 // Adding a local symbol to a .dynsym is a bug.
1905 assert(this->Type != SHT_DYNSYM || !B->isLocal());
1907 bool HashIt = B->isLocal();
1908 Symbols.push_back({B, StrTabSec.addString(B->getName(), HashIt)});
1911 size_t SymbolTableBaseSection::getSymbolIndex(Symbol *Sym) {
1912 // Initializes symbol lookup tables lazily. This is used only
1913 // for -r or -emit-relocs.
1914 llvm::call_once(OnceFlag, [&] {
1915 SymbolIndexMap.reserve(Symbols.size());
1917 for (const SymbolTableEntry &E : Symbols) {
1918 if (E.Sym->Type == STT_SECTION)
1919 SectionIndexMap[E.Sym->getOutputSection()] = ++I;
1921 SymbolIndexMap[E.Sym] = ++I;
1925 // Section symbols are mapped based on their output sections
1926 // to maintain their semantics.
1927 if (Sym->Type == STT_SECTION)
1928 return SectionIndexMap.lookup(Sym->getOutputSection());
1929 return SymbolIndexMap.lookup(Sym);
1932 template <class ELFT>
1933 SymbolTableSection<ELFT>::SymbolTableSection(StringTableSection &StrTabSec)
1934 : SymbolTableBaseSection(StrTabSec) {
1935 this->Entsize = sizeof(Elf_Sym);
1938 // Write the internal symbol table contents to the output symbol table.
1939 template <class ELFT> void SymbolTableSection<ELFT>::writeTo(uint8_t *Buf) {
1940 // The first entry is a null entry as per the ELF spec.
1941 memset(Buf, 0, sizeof(Elf_Sym));
1942 Buf += sizeof(Elf_Sym);
1944 auto *ESym = reinterpret_cast<Elf_Sym *>(Buf);
1946 for (SymbolTableEntry &Ent : Symbols) {
1947 Symbol *Sym = Ent.Sym;
1949 // Set st_info and st_other.
1951 if (Sym->isLocal()) {
1952 ESym->setBindingAndType(STB_LOCAL, Sym->Type);
1954 ESym->setBindingAndType(Sym->computeBinding(), Sym->Type);
1955 ESym->setVisibility(Sym->Visibility);
1958 ESym->st_name = Ent.StrTabOffset;
1960 // Set a section index.
1961 BssSection *CommonSec = nullptr;
1962 if (!Config->DefineCommon)
1963 if (auto *D = dyn_cast<Defined>(Sym))
1964 CommonSec = dyn_cast_or_null<BssSection>(D->Section);
1966 ESym->st_shndx = SHN_COMMON;
1967 else if (Sym->NeedsPltAddr)
1968 ESym->st_shndx = SHN_UNDEF;
1969 else if (const OutputSection *OutSec = Sym->getOutputSection())
1970 ESym->st_shndx = OutSec->SectionIndex;
1971 else if (isa<Defined>(Sym))
1972 ESym->st_shndx = SHN_ABS;
1974 ESym->st_shndx = SHN_UNDEF;
1976 // Copy symbol size if it is a defined symbol. st_size is not significant
1977 // for undefined symbols, so whether copying it or not is up to us if that's
1978 // the case. We'll leave it as zero because by not setting a value, we can
1979 // get the exact same outputs for two sets of input files that differ only
1980 // in undefined symbol size in DSOs.
1981 if (ESym->st_shndx == SHN_UNDEF)
1984 ESym->st_size = Sym->getSize();
1986 // st_value is usually an address of a symbol, but that has a
1987 // special meaining for uninstantiated common symbols (this can
1988 // occur if -r is given).
1990 ESym->st_value = CommonSec->Alignment;
1992 ESym->st_value = Sym->getVA();
1997 // On MIPS we need to mark symbol which has a PLT entry and requires
1998 // pointer equality by STO_MIPS_PLT flag. That is necessary to help
1999 // dynamic linker distinguish such symbols and MIPS lazy-binding stubs.
2000 // https://sourceware.org/ml/binutils/2008-07/txt00000.txt
2001 if (Config->EMachine == EM_MIPS) {
2002 auto *ESym = reinterpret_cast<Elf_Sym *>(Buf);
2004 for (SymbolTableEntry &Ent : Symbols) {
2005 Symbol *Sym = Ent.Sym;
2006 if (Sym->isInPlt() && Sym->NeedsPltAddr)
2007 ESym->st_other |= STO_MIPS_PLT;
2008 if (isMicroMips()) {
2009 // Set STO_MIPS_MICROMIPS flag and less-significant bit for
2010 // a defined microMIPS symbol and symbol should point to its
2011 // PLT entry (in case of microMIPS, PLT entries always contain
2013 if (Sym->isDefined() &&
2014 ((Sym->StOther & STO_MIPS_MICROMIPS) || Sym->NeedsPltAddr)) {
2015 if (StrTabSec.isDynamic())
2016 ESym->st_value |= 1;
2017 ESym->st_other |= STO_MIPS_MICROMIPS;
2020 if (Config->Relocatable)
2021 if (auto *D = dyn_cast<Defined>(Sym))
2022 if (isMipsPIC<ELFT>(D))
2023 ESym->st_other |= STO_MIPS_PIC;
2029 // .hash and .gnu.hash sections contain on-disk hash tables that map
2030 // symbol names to their dynamic symbol table indices. Their purpose
2031 // is to help the dynamic linker resolve symbols quickly. If ELF files
2032 // don't have them, the dynamic linker has to do linear search on all
2033 // dynamic symbols, which makes programs slower. Therefore, a .hash
2034 // section is added to a DSO by default. A .gnu.hash is added if you
2035 // give the -hash-style=gnu or -hash-style=both option.
2037 // The Unix semantics of resolving dynamic symbols is somewhat expensive.
2038 // Each ELF file has a list of DSOs that the ELF file depends on and a
2039 // list of dynamic symbols that need to be resolved from any of the
2040 // DSOs. That means resolving all dynamic symbols takes O(m)*O(n)
2041 // where m is the number of DSOs and n is the number of dynamic
2042 // symbols. For modern large programs, both m and n are large. So
2043 // making each step faster by using hash tables substiantially
2044 // improves time to load programs.
2046 // (Note that this is not the only way to design the shared library.
2047 // For instance, the Windows DLL takes a different approach. On
2048 // Windows, each dynamic symbol has a name of DLL from which the symbol
2049 // has to be resolved. That makes the cost of symbol resolution O(n).
2050 // This disables some hacky techniques you can use on Unix such as
2051 // LD_PRELOAD, but this is arguably better semantics than the Unix ones.)
2053 // Due to historical reasons, we have two different hash tables, .hash
2054 // and .gnu.hash. They are for the same purpose, and .gnu.hash is a new
2055 // and better version of .hash. .hash is just an on-disk hash table, but
2056 // .gnu.hash has a bloom filter in addition to a hash table to skip
2057 // DSOs very quickly. If you are sure that your dynamic linker knows
2058 // about .gnu.hash, you want to specify -hash-style=gnu. Otherwise, a
2059 // safe bet is to specify -hash-style=both for backward compatibilty.
2060 GnuHashTableSection::GnuHashTableSection()
2061 : SyntheticSection(SHF_ALLOC, SHT_GNU_HASH, Config->Wordsize, ".gnu.hash") {
2064 void GnuHashTableSection::finalizeContents() {
2065 getParent()->Link = InX::DynSymTab->getParent()->SectionIndex;
2067 // Computes bloom filter size in word size. We want to allocate 12
2068 // bits for each symbol. It must be a power of two.
2069 if (Symbols.empty()) {
2072 uint64_t NumBits = Symbols.size() * 12;
2073 MaskWords = NextPowerOf2(NumBits / (Config->Wordsize * 8));
2076 Size = 16; // Header
2077 Size += Config->Wordsize * MaskWords; // Bloom filter
2078 Size += NBuckets * 4; // Hash buckets
2079 Size += Symbols.size() * 4; // Hash values
2082 void GnuHashTableSection::writeTo(uint8_t *Buf) {
2083 // The output buffer is not guaranteed to be zero-cleared because we pre-
2084 // fill executable sections with trap instructions. This is a precaution
2085 // for that case, which happens only when -no-rosegment is given.
2086 memset(Buf, 0, Size);
2089 write32(Buf, NBuckets);
2090 write32(Buf + 4, InX::DynSymTab->getNumSymbols() - Symbols.size());
2091 write32(Buf + 8, MaskWords);
2092 write32(Buf + 12, Shift2);
2095 // Write a bloom filter and a hash table.
2096 writeBloomFilter(Buf);
2097 Buf += Config->Wordsize * MaskWords;
2098 writeHashTable(Buf);
2101 // This function writes a 2-bit bloom filter. This bloom filter alone
2102 // usually filters out 80% or more of all symbol lookups [1].
2103 // The dynamic linker uses the hash table only when a symbol is not
2104 // filtered out by a bloom filter.
2106 // [1] Ulrich Drepper (2011), "How To Write Shared Libraries" (Ver. 4.1.2),
2107 // p.9, https://www.akkadia.org/drepper/dsohowto.pdf
2108 void GnuHashTableSection::writeBloomFilter(uint8_t *Buf) {
2109 unsigned C = Config->Is64 ? 64 : 32;
2110 for (const Entry &Sym : Symbols) {
2111 size_t I = (Sym.Hash / C) & (MaskWords - 1);
2112 uint64_t Val = readUint(Buf + I * Config->Wordsize);
2113 Val |= uint64_t(1) << (Sym.Hash % C);
2114 Val |= uint64_t(1) << ((Sym.Hash >> Shift2) % C);
2115 writeUint(Buf + I * Config->Wordsize, Val);
2119 void GnuHashTableSection::writeHashTable(uint8_t *Buf) {
2120 uint32_t *Buckets = reinterpret_cast<uint32_t *>(Buf);
2121 uint32_t OldBucket = -1;
2122 uint32_t *Values = Buckets + NBuckets;
2123 for (auto I = Symbols.begin(), E = Symbols.end(); I != E; ++I) {
2124 // Write a hash value. It represents a sequence of chains that share the
2125 // same hash modulo value. The last element of each chain is terminated by
2127 uint32_t Hash = I->Hash;
2128 bool IsLastInChain = (I + 1) == E || I->BucketIdx != (I + 1)->BucketIdx;
2129 Hash = IsLastInChain ? Hash | 1 : Hash & ~1;
2130 write32(Values++, Hash);
2132 if (I->BucketIdx == OldBucket)
2134 // Write a hash bucket. Hash buckets contain indices in the following hash
2136 write32(Buckets + I->BucketIdx, I->Sym->DynsymIndex);
2137 OldBucket = I->BucketIdx;
2141 static uint32_t hashGnu(StringRef Name) {
2143 for (uint8_t C : Name)
2144 H = (H << 5) + H + C;
2148 // Add symbols to this symbol hash table. Note that this function
2149 // destructively sort a given vector -- which is needed because
2150 // GNU-style hash table places some sorting requirements.
2151 void GnuHashTableSection::addSymbols(std::vector<SymbolTableEntry> &V) {
2152 // We cannot use 'auto' for Mid because GCC 6.1 cannot deduce
2153 // its type correctly.
2154 std::vector<SymbolTableEntry>::iterator Mid =
2155 std::stable_partition(V.begin(), V.end(), [](const SymbolTableEntry &S) {
2156 return !S.Sym->isDefined();
2159 // We chose load factor 4 for the on-disk hash table. For each hash
2160 // collision, the dynamic linker will compare a uint32_t hash value.
2161 // Since the integer comparison is quite fast, we believe we can
2162 // make the load factor even larger. 4 is just a conservative choice.
2164 // Note that we don't want to create a zero-sized hash table because
2165 // Android loader as of 2018 doesn't like a .gnu.hash containing such
2166 // table. If that's the case, we create a hash table with one unused
2168 NBuckets = std::max<size_t>((V.end() - Mid) / 4, 1);
2173 for (SymbolTableEntry &Ent : llvm::make_range(Mid, V.end())) {
2174 Symbol *B = Ent.Sym;
2175 uint32_t Hash = hashGnu(B->getName());
2176 uint32_t BucketIdx = Hash % NBuckets;
2177 Symbols.push_back({B, Ent.StrTabOffset, Hash, BucketIdx});
2181 Symbols.begin(), Symbols.end(),
2182 [](const Entry &L, const Entry &R) { return L.BucketIdx < R.BucketIdx; });
2184 V.erase(Mid, V.end());
2185 for (const Entry &Ent : Symbols)
2186 V.push_back({Ent.Sym, Ent.StrTabOffset});
2189 HashTableSection::HashTableSection()
2190 : SyntheticSection(SHF_ALLOC, SHT_HASH, 4, ".hash") {
2194 void HashTableSection::finalizeContents() {
2195 getParent()->Link = InX::DynSymTab->getParent()->SectionIndex;
2197 unsigned NumEntries = 2; // nbucket and nchain.
2198 NumEntries += InX::DynSymTab->getNumSymbols(); // The chain entries.
2200 // Create as many buckets as there are symbols.
2201 NumEntries += InX::DynSymTab->getNumSymbols();
2202 this->Size = NumEntries * 4;
2205 void HashTableSection::writeTo(uint8_t *Buf) {
2206 // See comment in GnuHashTableSection::writeTo.
2207 memset(Buf, 0, Size);
2209 unsigned NumSymbols = InX::DynSymTab->getNumSymbols();
2211 uint32_t *P = reinterpret_cast<uint32_t *>(Buf);
2212 write32(P++, NumSymbols); // nbucket
2213 write32(P++, NumSymbols); // nchain
2215 uint32_t *Buckets = P;
2216 uint32_t *Chains = P + NumSymbols;
2218 for (const SymbolTableEntry &S : InX::DynSymTab->getSymbols()) {
2219 Symbol *Sym = S.Sym;
2220 StringRef Name = Sym->getName();
2221 unsigned I = Sym->DynsymIndex;
2222 uint32_t Hash = hashSysV(Name) % NumSymbols;
2223 Chains[I] = Buckets[Hash];
2224 write32(Buckets + Hash, I);
2228 // On PowerPC64 the lazy symbol resolvers go into the `global linkage table`
2229 // in the .glink section, rather then the typical .plt section.
2230 PltSection::PltSection(bool IsIplt)
2231 : SyntheticSection(SHF_ALLOC | SHF_EXECINSTR, SHT_PROGBITS, 16,
2232 Config->EMachine == EM_PPC64 ? ".glink" : ".plt"),
2233 HeaderSize(IsIplt ? 0 : Target->PltHeaderSize), IsIplt(IsIplt) {
2234 // The PLT needs to be writable on SPARC as the dynamic linker will
2235 // modify the instructions in the PLT entries.
2236 if (Config->EMachine == EM_SPARCV9)
2237 this->Flags |= SHF_WRITE;
2240 void PltSection::writeTo(uint8_t *Buf) {
2241 // At beginning of PLT but not the IPLT, we have code to call the dynamic
2242 // linker to resolve dynsyms at runtime. Write such code.
2244 Target->writePltHeader(Buf);
2245 size_t Off = HeaderSize;
2246 // The IPlt is immediately after the Plt, account for this in RelOff
2247 unsigned PltOff = getPltRelocOff();
2249 for (auto &I : Entries) {
2250 const Symbol *B = I.first;
2251 unsigned RelOff = I.second + PltOff;
2252 uint64_t Got = B->getGotPltVA();
2253 uint64_t Plt = this->getVA() + Off;
2254 Target->writePlt(Buf + Off, Got, Plt, B->PltIndex, RelOff);
2255 Off += Target->PltEntrySize;
2259 template <class ELFT> void PltSection::addEntry(Symbol &Sym) {
2260 Sym.PltIndex = Entries.size();
2261 RelocationBaseSection *PltRelocSection = InX::RelaPlt;
2263 PltRelocSection = InX::RelaIplt;
2264 Sym.IsInIplt = true;
2267 static_cast<RelocationSection<ELFT> *>(PltRelocSection)->getRelocOffset();
2268 Entries.push_back(std::make_pair(&Sym, RelOff));
2271 size_t PltSection::getSize() const {
2272 return HeaderSize + Entries.size() * Target->PltEntrySize;
2275 // Some architectures such as additional symbols in the PLT section. For
2276 // example ARM uses mapping symbols to aid disassembly
2277 void PltSection::addSymbols() {
2278 // The PLT may have symbols defined for the Header, the IPLT has no header
2280 Target->addPltHeaderSymbols(*this);
2281 size_t Off = HeaderSize;
2282 for (size_t I = 0; I < Entries.size(); ++I) {
2283 Target->addPltSymbols(*this, Off);
2284 Off += Target->PltEntrySize;
2288 unsigned PltSection::getPltRelocOff() const {
2289 return IsIplt ? InX::Plt->getSize() : 0;
2292 // The string hash function for .gdb_index.
2293 static uint32_t computeGdbHash(StringRef S) {
2296 H = H * 67 + tolower(C) - 113;
2300 GdbIndexSection::GdbIndexSection()
2301 : SyntheticSection(0, SHT_PROGBITS, 1, ".gdb_index") {}
2303 // Returns the desired size of an on-disk hash table for a .gdb_index section.
2304 // There's a tradeoff between size and collision rate. We aim 75% utilization.
2305 size_t GdbIndexSection::computeSymtabSize() const {
2306 return std::max<size_t>(NextPowerOf2(Symbols.size() * 4 / 3), 1024);
2309 // Compute the output section size.
2310 void GdbIndexSection::initOutputSize() {
2311 Size = sizeof(GdbIndexHeader) + computeSymtabSize() * 8;
2313 for (GdbChunk &Chunk : Chunks)
2314 Size += Chunk.CompilationUnits.size() * 16 + Chunk.AddressAreas.size() * 20;
2316 // Add the constant pool size if exists.
2317 if (!Symbols.empty()) {
2318 GdbSymbol &Sym = Symbols.back();
2319 Size += Sym.NameOff + Sym.Name.size() + 1;
2323 static std::vector<InputSection *> getDebugInfoSections() {
2324 std::vector<InputSection *> Ret;
2325 for (InputSectionBase *S : InputSections)
2326 if (InputSection *IS = dyn_cast<InputSection>(S))
2327 if (IS->Name == ".debug_info")
2332 static std::vector<GdbIndexSection::CuEntry> readCuList(DWARFContext &Dwarf) {
2333 std::vector<GdbIndexSection::CuEntry> Ret;
2334 for (std::unique_ptr<DWARFCompileUnit> &Cu : Dwarf.compile_units())
2335 Ret.push_back({Cu->getOffset(), Cu->getLength() + 4});
2339 static std::vector<GdbIndexSection::AddressEntry>
2340 readAddressAreas(DWARFContext &Dwarf, InputSection *Sec) {
2341 std::vector<GdbIndexSection::AddressEntry> Ret;
2344 for (std::unique_ptr<DWARFCompileUnit> &Cu : Dwarf.compile_units()) {
2345 DWARFAddressRangesVector Ranges;
2346 Cu->collectAddressRanges(Ranges);
2348 ArrayRef<InputSectionBase *> Sections = Sec->File->getSections();
2349 for (DWARFAddressRange &R : Ranges) {
2350 InputSectionBase *S = Sections[R.SectionIndex];
2351 if (!S || S == &InputSection::Discarded || !S->Live)
2353 // Range list with zero size has no effect.
2354 if (R.LowPC == R.HighPC)
2356 auto *IS = cast<InputSection>(S);
2357 uint64_t Offset = IS->getOffsetInFile();
2358 Ret.push_back({IS, R.LowPC - Offset, R.HighPC - Offset, CuIdx});
2365 static std::vector<GdbIndexSection::NameTypeEntry>
2366 readPubNamesAndTypes(DWARFContext &Dwarf, uint32_t Idx) {
2367 StringRef Sec1 = Dwarf.getDWARFObj().getGnuPubNamesSection();
2368 StringRef Sec2 = Dwarf.getDWARFObj().getGnuPubTypesSection();
2370 std::vector<GdbIndexSection::NameTypeEntry> Ret;
2371 for (StringRef Sec : {Sec1, Sec2}) {
2372 DWARFDebugPubTable Table(Sec, Config->IsLE, true);
2373 for (const DWARFDebugPubTable::Set &Set : Table.getData())
2374 for (const DWARFDebugPubTable::Entry &Ent : Set.Entries)
2375 Ret.push_back({{Ent.Name, computeGdbHash(Ent.Name)},
2376 (Ent.Descriptor.toBits() << 24) | Idx});
2381 // Create a list of symbols from a given list of symbol names and types
2382 // by uniquifying them by name.
2383 static std::vector<GdbIndexSection::GdbSymbol>
2384 createSymbols(ArrayRef<std::vector<GdbIndexSection::NameTypeEntry>> NameTypes) {
2385 typedef GdbIndexSection::GdbSymbol GdbSymbol;
2386 typedef GdbIndexSection::NameTypeEntry NameTypeEntry;
2388 // The number of symbols we will handle in this function is of the order
2389 // of millions for very large executables, so we use multi-threading to
2391 size_t NumShards = 32;
2392 size_t Concurrency = 1;
2395 std::min<size_t>(PowerOf2Floor(hardware_concurrency()), NumShards);
2397 // A sharded map to uniquify symbols by name.
2398 std::vector<DenseMap<CachedHashStringRef, size_t>> Map(NumShards);
2399 size_t Shift = 32 - countTrailingZeros(NumShards);
2401 // Instantiate GdbSymbols while uniqufying them by name.
2402 std::vector<std::vector<GdbSymbol>> Symbols(NumShards);
2403 parallelForEachN(0, Concurrency, [&](size_t ThreadId) {
2404 for (ArrayRef<NameTypeEntry> Entries : NameTypes) {
2405 for (const NameTypeEntry &Ent : Entries) {
2406 size_t ShardId = Ent.Name.hash() >> Shift;
2407 if ((ShardId & (Concurrency - 1)) != ThreadId)
2410 size_t &Idx = Map[ShardId][Ent.Name];
2412 Symbols[ShardId][Idx - 1].CuVector.push_back(Ent.Type);
2416 Idx = Symbols[ShardId].size() + 1;
2417 Symbols[ShardId].push_back({Ent.Name, {Ent.Type}, 0, 0});
2422 size_t NumSymbols = 0;
2423 for (ArrayRef<GdbSymbol> V : Symbols)
2424 NumSymbols += V.size();
2426 // The return type is a flattened vector, so we'll copy each vector
2428 std::vector<GdbSymbol> Ret;
2429 Ret.reserve(NumSymbols);
2430 for (std::vector<GdbSymbol> &Vec : Symbols)
2431 for (GdbSymbol &Sym : Vec)
2432 Ret.push_back(std::move(Sym));
2434 // CU vectors and symbol names are adjacent in the output file.
2435 // We can compute their offsets in the output file now.
2437 for (GdbSymbol &Sym : Ret) {
2438 Sym.CuVectorOff = Off;
2439 Off += (Sym.CuVector.size() + 1) * 4;
2441 for (GdbSymbol &Sym : Ret) {
2443 Off += Sym.Name.size() + 1;
2449 // Returns a newly-created .gdb_index section.
2450 template <class ELFT> GdbIndexSection *GdbIndexSection::create() {
2451 std::vector<InputSection *> Sections = getDebugInfoSections();
2453 // .debug_gnu_pub{names,types} are useless in executables.
2454 // They are present in input object files solely for creating
2455 // a .gdb_index. So we can remove them from the output.
2456 for (InputSectionBase *S : InputSections)
2457 if (S->Name == ".debug_gnu_pubnames" || S->Name == ".debug_gnu_pubtypes")
2460 std::vector<GdbChunk> Chunks(Sections.size());
2461 std::vector<std::vector<NameTypeEntry>> NameTypes(Sections.size());
2463 parallelForEachN(0, Sections.size(), [&](size_t I) {
2464 ObjFile<ELFT> *File = Sections[I]->getFile<ELFT>();
2465 DWARFContext Dwarf(make_unique<LLDDwarfObj<ELFT>>(File));
2467 Chunks[I].Sec = Sections[I];
2468 Chunks[I].CompilationUnits = readCuList(Dwarf);
2469 Chunks[I].AddressAreas = readAddressAreas(Dwarf, Sections[I]);
2470 NameTypes[I] = readPubNamesAndTypes(Dwarf, I);
2473 auto *Ret = make<GdbIndexSection>();
2474 Ret->Chunks = std::move(Chunks);
2475 Ret->Symbols = createSymbols(NameTypes);
2476 Ret->initOutputSize();
2480 void GdbIndexSection::writeTo(uint8_t *Buf) {
2481 // Write the header.
2482 auto *Hdr = reinterpret_cast<GdbIndexHeader *>(Buf);
2483 uint8_t *Start = Buf;
2485 Buf += sizeof(*Hdr);
2487 // Write the CU list.
2488 Hdr->CuListOff = Buf - Start;
2489 for (GdbChunk &Chunk : Chunks) {
2490 for (CuEntry &Cu : Chunk.CompilationUnits) {
2491 write64le(Buf, Chunk.Sec->OutSecOff + Cu.CuOffset);
2492 write64le(Buf + 8, Cu.CuLength);
2497 // Write the address area.
2498 Hdr->CuTypesOff = Buf - Start;
2499 Hdr->AddressAreaOff = Buf - Start;
2501 for (GdbChunk &Chunk : Chunks) {
2502 for (AddressEntry &E : Chunk.AddressAreas) {
2503 uint64_t BaseAddr = E.Section->getVA(0);
2504 write64le(Buf, BaseAddr + E.LowAddress);
2505 write64le(Buf + 8, BaseAddr + E.HighAddress);
2506 write32le(Buf + 16, E.CuIndex + CuOff);
2509 CuOff += Chunk.CompilationUnits.size();
2512 // Write the on-disk open-addressing hash table containing symbols.
2513 Hdr->SymtabOff = Buf - Start;
2514 size_t SymtabSize = computeSymtabSize();
2515 uint32_t Mask = SymtabSize - 1;
2517 for (GdbSymbol &Sym : Symbols) {
2518 uint32_t H = Sym.Name.hash();
2519 uint32_t I = H & Mask;
2520 uint32_t Step = ((H * 17) & Mask) | 1;
2522 while (read32le(Buf + I * 8))
2523 I = (I + Step) & Mask;
2525 write32le(Buf + I * 8, Sym.NameOff);
2526 write32le(Buf + I * 8 + 4, Sym.CuVectorOff);
2529 Buf += SymtabSize * 8;
2531 // Write the string pool.
2532 Hdr->ConstantPoolOff = Buf - Start;
2533 for (GdbSymbol &Sym : Symbols)
2534 memcpy(Buf + Sym.NameOff, Sym.Name.data(), Sym.Name.size());
2536 // Write the CU vectors.
2537 for (GdbSymbol &Sym : Symbols) {
2538 write32le(Buf, Sym.CuVector.size());
2540 for (uint32_t Val : Sym.CuVector) {
2541 write32le(Buf, Val);
2547 bool GdbIndexSection::empty() const { return !Out::DebugInfo; }
2549 EhFrameHeader::EhFrameHeader()
2550 : SyntheticSection(SHF_ALLOC, SHT_PROGBITS, 4, ".eh_frame_hdr") {}
2552 // .eh_frame_hdr contains a binary search table of pointers to FDEs.
2553 // Each entry of the search table consists of two values,
2554 // the starting PC from where FDEs covers, and the FDE's address.
2555 // It is sorted by PC.
2556 void EhFrameHeader::writeTo(uint8_t *Buf) {
2557 typedef EhFrameSection::FdeData FdeData;
2559 std::vector<FdeData> Fdes = InX::EhFrame->getFdeData();
2562 Buf[1] = DW_EH_PE_pcrel | DW_EH_PE_sdata4;
2563 Buf[2] = DW_EH_PE_udata4;
2564 Buf[3] = DW_EH_PE_datarel | DW_EH_PE_sdata4;
2565 write32(Buf + 4, InX::EhFrame->getParent()->Addr - this->getVA() - 4);
2566 write32(Buf + 8, Fdes.size());
2569 for (FdeData &Fde : Fdes) {
2570 write32(Buf, Fde.PcRel);
2571 write32(Buf + 4, Fde.FdeVARel);
2576 size_t EhFrameHeader::getSize() const {
2577 // .eh_frame_hdr has a 12 bytes header followed by an array of FDEs.
2578 return 12 + InX::EhFrame->NumFdes * 8;
2581 bool EhFrameHeader::empty() const { return InX::EhFrame->empty(); }
2583 template <class ELFT>
2584 VersionDefinitionSection<ELFT>::VersionDefinitionSection()
2585 : SyntheticSection(SHF_ALLOC, SHT_GNU_verdef, sizeof(uint32_t),
2586 ".gnu.version_d") {}
2588 static StringRef getFileDefName() {
2589 if (!Config->SoName.empty())
2590 return Config->SoName;
2591 return Config->OutputFile;
2594 template <class ELFT> void VersionDefinitionSection<ELFT>::finalizeContents() {
2595 FileDefNameOff = InX::DynStrTab->addString(getFileDefName());
2596 for (VersionDefinition &V : Config->VersionDefinitions)
2597 V.NameOff = InX::DynStrTab->addString(V.Name);
2599 getParent()->Link = InX::DynStrTab->getParent()->SectionIndex;
2601 // sh_info should be set to the number of definitions. This fact is missed in
2602 // documentation, but confirmed by binutils community:
2603 // https://sourceware.org/ml/binutils/2014-11/msg00355.html
2604 getParent()->Info = getVerDefNum();
2607 template <class ELFT>
2608 void VersionDefinitionSection<ELFT>::writeOne(uint8_t *Buf, uint32_t Index,
2609 StringRef Name, size_t NameOff) {
2610 auto *Verdef = reinterpret_cast<Elf_Verdef *>(Buf);
2611 Verdef->vd_version = 1;
2613 Verdef->vd_aux = sizeof(Elf_Verdef);
2614 Verdef->vd_next = sizeof(Elf_Verdef) + sizeof(Elf_Verdaux);
2615 Verdef->vd_flags = (Index == 1 ? VER_FLG_BASE : 0);
2616 Verdef->vd_ndx = Index;
2617 Verdef->vd_hash = hashSysV(Name);
2619 auto *Verdaux = reinterpret_cast<Elf_Verdaux *>(Buf + sizeof(Elf_Verdef));
2620 Verdaux->vda_name = NameOff;
2621 Verdaux->vda_next = 0;
2624 template <class ELFT>
2625 void VersionDefinitionSection<ELFT>::writeTo(uint8_t *Buf) {
2626 writeOne(Buf, 1, getFileDefName(), FileDefNameOff);
2628 for (VersionDefinition &V : Config->VersionDefinitions) {
2629 Buf += sizeof(Elf_Verdef) + sizeof(Elf_Verdaux);
2630 writeOne(Buf, V.Id, V.Name, V.NameOff);
2633 // Need to terminate the last version definition.
2634 Elf_Verdef *Verdef = reinterpret_cast<Elf_Verdef *>(Buf);
2635 Verdef->vd_next = 0;
2638 template <class ELFT> size_t VersionDefinitionSection<ELFT>::getSize() const {
2639 return (sizeof(Elf_Verdef) + sizeof(Elf_Verdaux)) * getVerDefNum();
2642 template <class ELFT>
2643 VersionTableSection<ELFT>::VersionTableSection()
2644 : SyntheticSection(SHF_ALLOC, SHT_GNU_versym, sizeof(uint16_t),
2646 this->Entsize = sizeof(Elf_Versym);
2649 template <class ELFT> void VersionTableSection<ELFT>::finalizeContents() {
2650 // At the moment of june 2016 GNU docs does not mention that sh_link field
2651 // should be set, but Sun docs do. Also readelf relies on this field.
2652 getParent()->Link = InX::DynSymTab->getParent()->SectionIndex;
2655 template <class ELFT> size_t VersionTableSection<ELFT>::getSize() const {
2656 return sizeof(Elf_Versym) * (InX::DynSymTab->getSymbols().size() + 1);
2659 template <class ELFT> void VersionTableSection<ELFT>::writeTo(uint8_t *Buf) {
2660 auto *OutVersym = reinterpret_cast<Elf_Versym *>(Buf) + 1;
2661 for (const SymbolTableEntry &S : InX::DynSymTab->getSymbols()) {
2662 OutVersym->vs_index = S.Sym->VersionId;
2667 template <class ELFT> bool VersionTableSection<ELFT>::empty() const {
2668 return !In<ELFT>::VerDef && In<ELFT>::VerNeed->empty();
2671 template <class ELFT>
2672 VersionNeedSection<ELFT>::VersionNeedSection()
2673 : SyntheticSection(SHF_ALLOC, SHT_GNU_verneed, sizeof(uint32_t),
2675 // Identifiers in verneed section start at 2 because 0 and 1 are reserved
2676 // for VER_NDX_LOCAL and VER_NDX_GLOBAL.
2677 // First identifiers are reserved by verdef section if it exist.
2678 NextIndex = getVerDefNum() + 1;
2681 template <class ELFT> void VersionNeedSection<ELFT>::addSymbol(Symbol *SS) {
2682 auto &File = cast<SharedFile<ELFT>>(*SS->File);
2683 if (SS->VerdefIndex == VER_NDX_GLOBAL) {
2684 SS->VersionId = VER_NDX_GLOBAL;
2688 // If we don't already know that we need an Elf_Verneed for this DSO, prepare
2689 // to create one by adding it to our needed list and creating a dynstr entry
2691 if (File.VerdefMap.empty())
2692 Needed.push_back({&File, InX::DynStrTab->addString(File.SoName)});
2693 const typename ELFT::Verdef *Ver = File.Verdefs[SS->VerdefIndex];
2694 typename SharedFile<ELFT>::NeededVer &NV = File.VerdefMap[Ver];
2696 // If we don't already know that we need an Elf_Vernaux for this Elf_Verdef,
2697 // prepare to create one by allocating a version identifier and creating a
2698 // dynstr entry for the version name.
2699 if (NV.Index == 0) {
2700 NV.StrTab = InX::DynStrTab->addString(File.getStringTable().data() +
2701 Ver->getAux()->vda_name);
2702 NV.Index = NextIndex++;
2704 SS->VersionId = NV.Index;
2707 template <class ELFT> void VersionNeedSection<ELFT>::writeTo(uint8_t *Buf) {
2708 // The Elf_Verneeds need to appear first, followed by the Elf_Vernauxs.
2709 auto *Verneed = reinterpret_cast<Elf_Verneed *>(Buf);
2710 auto *Vernaux = reinterpret_cast<Elf_Vernaux *>(Verneed + Needed.size());
2712 for (std::pair<SharedFile<ELFT> *, size_t> &P : Needed) {
2713 // Create an Elf_Verneed for this DSO.
2714 Verneed->vn_version = 1;
2715 Verneed->vn_cnt = P.first->VerdefMap.size();
2716 Verneed->vn_file = P.second;
2718 reinterpret_cast<char *>(Vernaux) - reinterpret_cast<char *>(Verneed);
2719 Verneed->vn_next = sizeof(Elf_Verneed);
2722 // Create the Elf_Vernauxs for this Elf_Verneed. The loop iterates over
2723 // VerdefMap, which will only contain references to needed version
2724 // definitions. Each Elf_Vernaux is based on the information contained in
2725 // the Elf_Verdef in the source DSO. This loop iterates over a std::map of
2726 // pointers, but is deterministic because the pointers refer to Elf_Verdef
2727 // data structures within a single input file.
2728 for (auto &NV : P.first->VerdefMap) {
2729 Vernaux->vna_hash = NV.first->vd_hash;
2730 Vernaux->vna_flags = 0;
2731 Vernaux->vna_other = NV.second.Index;
2732 Vernaux->vna_name = NV.second.StrTab;
2733 Vernaux->vna_next = sizeof(Elf_Vernaux);
2737 Vernaux[-1].vna_next = 0;
2739 Verneed[-1].vn_next = 0;
2742 template <class ELFT> void VersionNeedSection<ELFT>::finalizeContents() {
2743 getParent()->Link = InX::DynStrTab->getParent()->SectionIndex;
2744 getParent()->Info = Needed.size();
2747 template <class ELFT> size_t VersionNeedSection<ELFT>::getSize() const {
2748 unsigned Size = Needed.size() * sizeof(Elf_Verneed);
2749 for (const std::pair<SharedFile<ELFT> *, size_t> &P : Needed)
2750 Size += P.first->VerdefMap.size() * sizeof(Elf_Vernaux);
2754 template <class ELFT> bool VersionNeedSection<ELFT>::empty() const {
2755 return getNeedNum() == 0;
2758 void MergeSyntheticSection::addSection(MergeInputSection *MS) {
2760 Sections.push_back(MS);
2763 MergeTailSection::MergeTailSection(StringRef Name, uint32_t Type,
2764 uint64_t Flags, uint32_t Alignment)
2765 : MergeSyntheticSection(Name, Type, Flags, Alignment),
2766 Builder(StringTableBuilder::RAW, Alignment) {}
2768 size_t MergeTailSection::getSize() const { return Builder.getSize(); }
2770 void MergeTailSection::writeTo(uint8_t *Buf) { Builder.write(Buf); }
2772 void MergeTailSection::finalizeContents() {
2773 // Add all string pieces to the string table builder to create section
2775 for (MergeInputSection *Sec : Sections)
2776 for (size_t I = 0, E = Sec->Pieces.size(); I != E; ++I)
2777 if (Sec->Pieces[I].Live)
2778 Builder.add(Sec->getData(I));
2780 // Fix the string table content. After this, the contents will never change.
2783 // finalize() fixed tail-optimized strings, so we can now get
2784 // offsets of strings. Get an offset for each string and save it
2785 // to a corresponding StringPiece for easy access.
2786 for (MergeInputSection *Sec : Sections)
2787 for (size_t I = 0, E = Sec->Pieces.size(); I != E; ++I)
2788 if (Sec->Pieces[I].Live)
2789 Sec->Pieces[I].OutputOff = Builder.getOffset(Sec->getData(I));
2792 void MergeNoTailSection::writeTo(uint8_t *Buf) {
2793 for (size_t I = 0; I < NumShards; ++I)
2794 Shards[I].write(Buf + ShardOffsets[I]);
2797 // This function is very hot (i.e. it can take several seconds to finish)
2798 // because sometimes the number of inputs is in an order of magnitude of
2799 // millions. So, we use multi-threading.
2801 // For any strings S and T, we know S is not mergeable with T if S's hash
2802 // value is different from T's. If that's the case, we can safely put S and
2803 // T into different string builders without worrying about merge misses.
2804 // We do it in parallel.
2805 void MergeNoTailSection::finalizeContents() {
2806 // Initializes string table builders.
2807 for (size_t I = 0; I < NumShards; ++I)
2808 Shards.emplace_back(StringTableBuilder::RAW, Alignment);
2810 // Concurrency level. Must be a power of 2 to avoid expensive modulo
2811 // operations in the following tight loop.
2812 size_t Concurrency = 1;
2815 std::min<size_t>(PowerOf2Floor(hardware_concurrency()), NumShards);
2817 // Add section pieces to the builders.
2818 parallelForEachN(0, Concurrency, [&](size_t ThreadId) {
2819 for (MergeInputSection *Sec : Sections) {
2820 for (size_t I = 0, E = Sec->Pieces.size(); I != E; ++I) {
2821 size_t ShardId = getShardId(Sec->Pieces[I].Hash);
2822 if ((ShardId & (Concurrency - 1)) == ThreadId && Sec->Pieces[I].Live)
2823 Sec->Pieces[I].OutputOff = Shards[ShardId].add(Sec->getData(I));
2828 // Compute an in-section offset for each shard.
2830 for (size_t I = 0; I < NumShards; ++I) {
2831 Shards[I].finalizeInOrder();
2832 if (Shards[I].getSize() > 0)
2833 Off = alignTo(Off, Alignment);
2834 ShardOffsets[I] = Off;
2835 Off += Shards[I].getSize();
2839 // So far, section pieces have offsets from beginning of shards, but
2840 // we want offsets from beginning of the whole section. Fix them.
2841 parallelForEach(Sections, [&](MergeInputSection *Sec) {
2842 for (size_t I = 0, E = Sec->Pieces.size(); I != E; ++I)
2843 if (Sec->Pieces[I].Live)
2844 Sec->Pieces[I].OutputOff +=
2845 ShardOffsets[getShardId(Sec->Pieces[I].Hash)];
2849 static MergeSyntheticSection *createMergeSynthetic(StringRef Name,
2852 uint32_t Alignment) {
2853 bool ShouldTailMerge = (Flags & SHF_STRINGS) && Config->Optimize >= 2;
2854 if (ShouldTailMerge)
2855 return make<MergeTailSection>(Name, Type, Flags, Alignment);
2856 return make<MergeNoTailSection>(Name, Type, Flags, Alignment);
2859 // Debug sections may be compressed by zlib. Decompress if exists.
2860 void elf::decompressSections() {
2861 parallelForEach(InputSections,
2862 [](InputSectionBase *Sec) { Sec->maybeDecompress(); });
2865 template <class ELFT> void elf::splitSections() {
2866 // splitIntoPieces needs to be called on each MergeInputSection
2867 // before calling finalizeContents().
2868 parallelForEach(InputSections, [](InputSectionBase *Sec) {
2869 if (auto *S = dyn_cast<MergeInputSection>(Sec))
2870 S->splitIntoPieces();
2871 else if (auto *Eh = dyn_cast<EhInputSection>(Sec))
2876 // This function scans over the inputsections to create mergeable
2877 // synthetic sections.
2879 // It removes MergeInputSections from the input section array and adds
2880 // new synthetic sections at the location of the first input section
2881 // that it replaces. It then finalizes each synthetic section in order
2882 // to compute an output offset for each piece of each input section.
2883 void elf::mergeSections() {
2884 std::vector<MergeSyntheticSection *> MergeSections;
2885 for (InputSectionBase *&S : InputSections) {
2886 MergeInputSection *MS = dyn_cast<MergeInputSection>(S);
2890 // We do not want to handle sections that are not alive, so just remove
2891 // them instead of trying to merge.
2895 StringRef OutsecName = getOutputSectionName(MS);
2896 uint32_t Alignment = std::max<uint32_t>(MS->Alignment, MS->Entsize);
2898 auto I = llvm::find_if(MergeSections, [=](MergeSyntheticSection *Sec) {
2899 // While we could create a single synthetic section for two different
2900 // values of Entsize, it is better to take Entsize into consideration.
2902 // With a single synthetic section no two pieces with different Entsize
2903 // could be equal, so we may as well have two sections.
2905 // Using Entsize in here also allows us to propagate it to the synthetic
2907 return Sec->Name == OutsecName && Sec->Flags == MS->Flags &&
2908 Sec->Entsize == MS->Entsize && Sec->Alignment == Alignment;
2910 if (I == MergeSections.end()) {
2911 MergeSyntheticSection *Syn =
2912 createMergeSynthetic(OutsecName, MS->Type, MS->Flags, Alignment);
2913 MergeSections.push_back(Syn);
2914 I = std::prev(MergeSections.end());
2916 Syn->Entsize = MS->Entsize;
2920 (*I)->addSection(MS);
2922 for (auto *MS : MergeSections)
2923 MS->finalizeContents();
2925 std::vector<InputSectionBase *> &V = InputSections;
2926 V.erase(std::remove(V.begin(), V.end(), nullptr), V.end());
2929 MipsRldMapSection::MipsRldMapSection()
2930 : SyntheticSection(SHF_ALLOC | SHF_WRITE, SHT_PROGBITS, Config->Wordsize,
2933 ARMExidxSentinelSection::ARMExidxSentinelSection()
2934 : SyntheticSection(SHF_ALLOC | SHF_LINK_ORDER, SHT_ARM_EXIDX,
2935 Config->Wordsize, ".ARM.exidx") {}
2937 // Write a terminating sentinel entry to the end of the .ARM.exidx table.
2938 // This section will have been sorted last in the .ARM.exidx table.
2939 // This table entry will have the form:
2940 // | PREL31 upper bound of code that has exception tables | EXIDX_CANTUNWIND |
2941 // The sentinel must have the PREL31 value of an address higher than any
2942 // address described by any other table entry.
2943 void ARMExidxSentinelSection::writeTo(uint8_t *Buf) {
2945 uint64_t S = Highest->getVA(Highest->getSize());
2946 uint64_t P = getVA();
2947 Target->relocateOne(Buf, R_ARM_PREL31, S - P);
2948 write32le(Buf + 4, 1);
2951 // The sentinel has to be removed if there are no other .ARM.exidx entries.
2952 bool ARMExidxSentinelSection::empty() const {
2953 for (InputSection *IS : getInputSections(getParent()))
2954 if (!isa<ARMExidxSentinelSection>(IS))
2959 bool ARMExidxSentinelSection::classof(const SectionBase *D) {
2960 return D->kind() == InputSectionBase::Synthetic && D->Type == SHT_ARM_EXIDX;
2963 ThunkSection::ThunkSection(OutputSection *OS, uint64_t Off)
2964 : SyntheticSection(SHF_ALLOC | SHF_EXECINSTR, SHT_PROGBITS,
2965 Config->Wordsize, ".text.thunk") {
2967 this->OutSecOff = Off;
2970 void ThunkSection::addThunk(Thunk *T) {
2971 Thunks.push_back(T);
2972 T->addSymbols(*this);
2975 void ThunkSection::writeTo(uint8_t *Buf) {
2976 for (Thunk *T : Thunks)
2977 T->writeTo(Buf + T->Offset);
2980 InputSection *ThunkSection::getTargetInputSection() const {
2983 const Thunk *T = Thunks.front();
2984 return T->getTargetInputSection();
2987 bool ThunkSection::assignOffsets() {
2989 for (Thunk *T : Thunks) {
2990 Off = alignTo(Off, T->Alignment);
2992 uint32_t Size = T->size();
2993 T->getThunkTargetSym()->Size = Size;
2996 bool Changed = Off != Size;
3001 InputSection *InX::ARMAttributes;
3002 BssSection *InX::Bss;
3003 BssSection *InX::BssRelRo;
3004 BuildIdSection *InX::BuildId;
3005 EhFrameHeader *InX::EhFrameHdr;
3006 EhFrameSection *InX::EhFrame;
3007 SyntheticSection *InX::Dynamic;
3008 StringTableSection *InX::DynStrTab;
3009 SymbolTableBaseSection *InX::DynSymTab;
3010 InputSection *InX::Interp;
3011 GdbIndexSection *InX::GdbIndex;
3012 GotSection *InX::Got;
3013 GotPltSection *InX::GotPlt;
3014 GnuHashTableSection *InX::GnuHashTab;
3015 HashTableSection *InX::HashTab;
3016 IgotPltSection *InX::IgotPlt;
3017 MipsGotSection *InX::MipsGot;
3018 MipsRldMapSection *InX::MipsRldMap;
3019 PltSection *InX::Plt;
3020 PltSection *InX::Iplt;
3021 RelocationBaseSection *InX::RelaDyn;
3022 RelrBaseSection *InX::RelrDyn;
3023 RelocationBaseSection *InX::RelaPlt;
3024 RelocationBaseSection *InX::RelaIplt;
3025 StringTableSection *InX::ShStrTab;
3026 StringTableSection *InX::StrTab;
3027 SymbolTableBaseSection *InX::SymTab;
3029 template GdbIndexSection *GdbIndexSection::create<ELF32LE>();
3030 template GdbIndexSection *GdbIndexSection::create<ELF32BE>();
3031 template GdbIndexSection *GdbIndexSection::create<ELF64LE>();
3032 template GdbIndexSection *GdbIndexSection::create<ELF64BE>();
3034 template void elf::splitSections<ELF32LE>();
3035 template void elf::splitSections<ELF32BE>();
3036 template void elf::splitSections<ELF64LE>();
3037 template void elf::splitSections<ELF64BE>();
3039 template void EhFrameSection::addSection<ELF32LE>(InputSectionBase *);
3040 template void EhFrameSection::addSection<ELF32BE>(InputSectionBase *);
3041 template void EhFrameSection::addSection<ELF64LE>(InputSectionBase *);
3042 template void EhFrameSection::addSection<ELF64BE>(InputSectionBase *);
3044 template void PltSection::addEntry<ELF32LE>(Symbol &Sym);
3045 template void PltSection::addEntry<ELF32BE>(Symbol &Sym);
3046 template void PltSection::addEntry<ELF64LE>(Symbol &Sym);
3047 template void PltSection::addEntry<ELF64BE>(Symbol &Sym);
3049 template void MipsGotSection::build<ELF32LE>();
3050 template void MipsGotSection::build<ELF32BE>();
3051 template void MipsGotSection::build<ELF64LE>();
3052 template void MipsGotSection::build<ELF64BE>();
3054 template class elf::MipsAbiFlagsSection<ELF32LE>;
3055 template class elf::MipsAbiFlagsSection<ELF32BE>;
3056 template class elf::MipsAbiFlagsSection<ELF64LE>;
3057 template class elf::MipsAbiFlagsSection<ELF64BE>;
3059 template class elf::MipsOptionsSection<ELF32LE>;
3060 template class elf::MipsOptionsSection<ELF32BE>;
3061 template class elf::MipsOptionsSection<ELF64LE>;
3062 template class elf::MipsOptionsSection<ELF64BE>;
3064 template class elf::MipsReginfoSection<ELF32LE>;
3065 template class elf::MipsReginfoSection<ELF32BE>;
3066 template class elf::MipsReginfoSection<ELF64LE>;
3067 template class elf::MipsReginfoSection<ELF64BE>;
3069 template class elf::DynamicSection<ELF32LE>;
3070 template class elf::DynamicSection<ELF32BE>;
3071 template class elf::DynamicSection<ELF64LE>;
3072 template class elf::DynamicSection<ELF64BE>;
3074 template class elf::RelocationSection<ELF32LE>;
3075 template class elf::RelocationSection<ELF32BE>;
3076 template class elf::RelocationSection<ELF64LE>;
3077 template class elf::RelocationSection<ELF64BE>;
3079 template class elf::AndroidPackedRelocationSection<ELF32LE>;
3080 template class elf::AndroidPackedRelocationSection<ELF32BE>;
3081 template class elf::AndroidPackedRelocationSection<ELF64LE>;
3082 template class elf::AndroidPackedRelocationSection<ELF64BE>;
3084 template class elf::RelrSection<ELF32LE>;
3085 template class elf::RelrSection<ELF32BE>;
3086 template class elf::RelrSection<ELF64LE>;
3087 template class elf::RelrSection<ELF64BE>;
3089 template class elf::SymbolTableSection<ELF32LE>;
3090 template class elf::SymbolTableSection<ELF32BE>;
3091 template class elf::SymbolTableSection<ELF64LE>;
3092 template class elf::SymbolTableSection<ELF64BE>;
3094 template class elf::VersionTableSection<ELF32LE>;
3095 template class elf::VersionTableSection<ELF32BE>;
3096 template class elf::VersionTableSection<ELF64LE>;
3097 template class elf::VersionTableSection<ELF64BE>;
3099 template class elf::VersionNeedSection<ELF32LE>;
3100 template class elf::VersionNeedSection<ELF32BE>;
3101 template class elf::VersionNeedSection<ELF64LE>;
3102 template class elf::VersionNeedSection<ELF64BE>;
3104 template class elf::VersionDefinitionSection<ELF32LE>;
3105 template class elf::VersionDefinitionSection<ELF32BE>;
3106 template class elf::VersionDefinitionSection<ELF64LE>;
3107 template class elf::VersionDefinitionSection<ELF64BE>;