1 //===- SyntheticSections.cpp ----------------------------------------------===//
2 //
3 //                             The LLVM Linker
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
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
13 // input sections.
14 //
15 //===----------------------------------------------------------------------===//
16 
17 #include "SyntheticSections.h"
18 #include "Config.h"
19 #include "Error.h"
20 #include "InputFiles.h"
21 #include "LinkerScript.h"
22 #include "Memory.h"
23 #include "OutputSections.h"
24 #include "Strings.h"
25 #include "SymbolTable.h"
26 #include "Target.h"
27 #include "Threads.h"
28 #include "Writer.h"
29 #include "lld/Config/Version.h"
30 #include "llvm/Support/Dwarf.h"
31 #include "llvm/Support/Endian.h"
32 #include "llvm/Support/MD5.h"
33 #include "llvm/Support/RandomNumberGenerator.h"
34 #include "llvm/Support/SHA1.h"
35 #include "llvm/Support/xxhash.h"
36 #include <cstdlib>
37 
38 using namespace llvm;
39 using namespace llvm::dwarf;
40 using namespace llvm::ELF;
41 using namespace llvm::object;
42 using namespace llvm::support;
43 using namespace llvm::support::endian;
44 
45 using namespace lld;
46 using namespace lld::elf;
47 
48 template <class ELFT> static std::vector<DefinedCommon *> getCommonSymbols() {
49   std::vector<DefinedCommon *> V;
50   for (Symbol *S : Symtab<ELFT>::X->getSymbols())
51     if (auto *B = dyn_cast<DefinedCommon>(S->body()))
52       V.push_back(B);
53   return V;
54 }
55 
56 // Find all common symbols and allocate space for them.
57 template <class ELFT> InputSection<ELFT> *elf::createCommonSection() {
58   auto *Ret = make<InputSection<ELFT>>(SHF_ALLOC | SHF_WRITE, SHT_NOBITS, 1,
59                                        ArrayRef<uint8_t>(), "COMMON");
60   Ret->Live = true;
61 
62   // Sort the common symbols by alignment as an heuristic to pack them better.
63   std::vector<DefinedCommon *> Syms = getCommonSymbols<ELFT>();
64   std::stable_sort(Syms.begin(), Syms.end(),
65                    [](const DefinedCommon *A, const DefinedCommon *B) {
66                      return A->Alignment > B->Alignment;
67                    });
68 
69   // Assign offsets to symbols.
70   size_t Size = 0;
71   size_t Alignment = 1;
72   for (DefinedCommon *Sym : Syms) {
73     Alignment = std::max<size_t>(Alignment, Sym->Alignment);
74     Size = alignTo(Size, Sym->Alignment);
75 
76     // Compute symbol offset relative to beginning of input section.
77     Sym->Offset = Size;
78     Size += Sym->Size;
79   }
80   Ret->Alignment = Alignment;
81   Ret->Data = makeArrayRef<uint8_t>(nullptr, Size);
82   return Ret;
83 }
84 
85 // Returns an LLD version string.
86 static ArrayRef<uint8_t> getVersion() {
87   // Check LLD_VERSION first for ease of testing.
88   // You can get consitent output by using the environment variable.
89   // This is only for testing.
90   StringRef S = getenv("LLD_VERSION");
91   if (S.empty())
92     S = Saver.save(Twine("Linker: ") + getLLDVersion());
93 
94   // +1 to include the terminating '\0'.
95   return {(const uint8_t *)S.data(), S.size() + 1};
96 }
97 
98 // Creates a .comment section containing LLD version info.
99 // With this feature, you can identify LLD-generated binaries easily
100 // by "objdump -s -j .comment <file>".
101 // The returned object is a mergeable string section.
102 template <class ELFT> MergeInputSection<ELFT> *elf::createCommentSection() {
103   typename ELFT::Shdr Hdr = {};
104   Hdr.sh_flags = SHF_MERGE | SHF_STRINGS;
105   Hdr.sh_type = SHT_PROGBITS;
106   Hdr.sh_entsize = 1;
107   Hdr.sh_addralign = 1;
108 
109   auto *Ret = make<MergeInputSection<ELFT>>(/*file=*/nullptr, &Hdr, ".comment");
110   Ret->Data = getVersion();
111   Ret->splitIntoPieces();
112   return Ret;
113 }
114 
115 // .MIPS.abiflags section.
116 template <class ELFT>
117 MipsAbiFlagsSection<ELFT>::MipsAbiFlagsSection(Elf_Mips_ABIFlags Flags)
118     : SyntheticSection<ELFT>(SHF_ALLOC, SHT_MIPS_ABIFLAGS, 8, ".MIPS.abiflags"),
119       Flags(Flags) {}
120 
121 template <class ELFT> void MipsAbiFlagsSection<ELFT>::writeTo(uint8_t *Buf) {
122   memcpy(Buf, &Flags, sizeof(Flags));
123 }
124 
125 template <class ELFT>
126 MipsAbiFlagsSection<ELFT> *MipsAbiFlagsSection<ELFT>::create() {
127   Elf_Mips_ABIFlags Flags = {};
128   bool Create = false;
129 
130   for (InputSectionBase<ELFT> *Sec : Symtab<ELFT>::X->Sections) {
131     if (!Sec->Live || Sec->Type != SHT_MIPS_ABIFLAGS)
132       continue;
133     Sec->Live = false;
134     Create = true;
135 
136     std::string Filename = toString(Sec->getFile());
137     const size_t Size = Sec->Data.size();
138     // Older version of BFD (such as the default FreeBSD linker) concatenate
139     // .MIPS.abiflags instead of merging. To allow for this case (or potential
140     // zero padding) we ignore everything after the first Elf_Mips_ABIFlags
141     if (Size < sizeof(Elf_Mips_ABIFlags)) {
142       error(Filename + ": invalid size of .MIPS.abiflags section: got " +
143             Twine(Size) + " instead of " + Twine(sizeof(Elf_Mips_ABIFlags)));
144       return nullptr;
145     }
146     auto *S = reinterpret_cast<const Elf_Mips_ABIFlags *>(Sec->Data.data());
147     if (S->version != 0) {
148       error(Filename + ": unexpected .MIPS.abiflags version " +
149             Twine(S->version));
150       return nullptr;
151     }
152 
153     // LLD checks ISA compatibility in getMipsEFlags(). Here we just
154     // select the highest number of ISA/Rev/Ext.
155     Flags.isa_level = std::max(Flags.isa_level, S->isa_level);
156     Flags.isa_rev = std::max(Flags.isa_rev, S->isa_rev);
157     Flags.isa_ext = std::max(Flags.isa_ext, S->isa_ext);
158     Flags.gpr_size = std::max(Flags.gpr_size, S->gpr_size);
159     Flags.cpr1_size = std::max(Flags.cpr1_size, S->cpr1_size);
160     Flags.cpr2_size = std::max(Flags.cpr2_size, S->cpr2_size);
161     Flags.ases |= S->ases;
162     Flags.flags1 |= S->flags1;
163     Flags.flags2 |= S->flags2;
164     Flags.fp_abi = elf::getMipsFpAbiFlag(Flags.fp_abi, S->fp_abi, Filename);
165   };
166 
167   if (Create)
168     return make<MipsAbiFlagsSection<ELFT>>(Flags);
169   return nullptr;
170 }
171 
172 // .MIPS.options section.
173 template <class ELFT>
174 MipsOptionsSection<ELFT>::MipsOptionsSection(Elf_Mips_RegInfo Reginfo)
175     : SyntheticSection<ELFT>(SHF_ALLOC, SHT_MIPS_OPTIONS, 8, ".MIPS.options"),
176       Reginfo(Reginfo) {}
177 
178 template <class ELFT> void MipsOptionsSection<ELFT>::writeTo(uint8_t *Buf) {
179   auto *Options = reinterpret_cast<Elf_Mips_Options *>(Buf);
180   Options->kind = ODK_REGINFO;
181   Options->size = getSize();
182 
183   if (!Config->Relocatable)
184     Reginfo.ri_gp_value = In<ELFT>::MipsGot->getGp();
185   memcpy(Buf + sizeof(Elf_Mips_Options), &Reginfo, sizeof(Reginfo));
186 }
187 
188 template <class ELFT>
189 MipsOptionsSection<ELFT> *MipsOptionsSection<ELFT>::create() {
190   // N64 ABI only.
191   if (!ELFT::Is64Bits)
192     return nullptr;
193 
194   Elf_Mips_RegInfo Reginfo = {};
195   bool Create = false;
196 
197   for (InputSectionBase<ELFT> *Sec : Symtab<ELFT>::X->Sections) {
198     if (!Sec->Live || Sec->Type != SHT_MIPS_OPTIONS)
199       continue;
200     Sec->Live = false;
201     Create = true;
202 
203     std::string Filename = toString(Sec->getFile());
204     ArrayRef<uint8_t> D = Sec->Data;
205 
206     while (!D.empty()) {
207       if (D.size() < sizeof(Elf_Mips_Options)) {
208         error(Filename + ": invalid size of .MIPS.options section");
209         break;
210       }
211 
212       auto *Opt = reinterpret_cast<const Elf_Mips_Options *>(D.data());
213       if (Opt->kind == ODK_REGINFO) {
214         if (Config->Relocatable && Opt->getRegInfo().ri_gp_value)
215           error(Filename + ": unsupported non-zero ri_gp_value");
216         Reginfo.ri_gprmask |= Opt->getRegInfo().ri_gprmask;
217         Sec->getFile()->MipsGp0 = Opt->getRegInfo().ri_gp_value;
218         break;
219       }
220 
221       if (!Opt->size)
222         fatal(Filename + ": zero option descriptor size");
223       D = D.slice(Opt->size);
224     }
225   };
226 
227   if (Create)
228     return make<MipsOptionsSection<ELFT>>(Reginfo);
229   return nullptr;
230 }
231 
232 // MIPS .reginfo section.
233 template <class ELFT>
234 MipsReginfoSection<ELFT>::MipsReginfoSection(Elf_Mips_RegInfo Reginfo)
235     : SyntheticSection<ELFT>(SHF_ALLOC, SHT_MIPS_REGINFO, 4, ".reginfo"),
236       Reginfo(Reginfo) {}
237 
238 template <class ELFT> void MipsReginfoSection<ELFT>::writeTo(uint8_t *Buf) {
239   if (!Config->Relocatable)
240     Reginfo.ri_gp_value = In<ELFT>::MipsGot->getGp();
241   memcpy(Buf, &Reginfo, sizeof(Reginfo));
242 }
243 
244 template <class ELFT>
245 MipsReginfoSection<ELFT> *MipsReginfoSection<ELFT>::create() {
246   // Section should be alive for O32 and N32 ABIs only.
247   if (ELFT::Is64Bits)
248     return nullptr;
249 
250   Elf_Mips_RegInfo Reginfo = {};
251   bool Create = false;
252 
253   for (InputSectionBase<ELFT> *Sec : Symtab<ELFT>::X->Sections) {
254     if (!Sec->Live || Sec->Type != SHT_MIPS_REGINFO)
255       continue;
256     Sec->Live = false;
257     Create = true;
258 
259     if (Sec->Data.size() != sizeof(Elf_Mips_RegInfo)) {
260       error(toString(Sec->getFile()) + ": invalid size of .reginfo section");
261       return nullptr;
262     }
263     auto *R = reinterpret_cast<const Elf_Mips_RegInfo *>(Sec->Data.data());
264     if (Config->Relocatable && R->ri_gp_value)
265       error(toString(Sec->getFile()) + ": unsupported non-zero ri_gp_value");
266 
267     Reginfo.ri_gprmask |= R->ri_gprmask;
268     Sec->getFile()->MipsGp0 = R->ri_gp_value;
269   };
270 
271   if (Create)
272     return make<MipsReginfoSection<ELFT>>(Reginfo);
273   return nullptr;
274 }
275 
276 template <class ELFT> InputSection<ELFT> *elf::createInterpSection() {
277   auto *Ret = make<InputSection<ELFT>>(SHF_ALLOC, SHT_PROGBITS, 1,
278                                        ArrayRef<uint8_t>(), ".interp");
279   Ret->Live = true;
280 
281   // StringSaver guarantees that the returned string ends with '\0'.
282   StringRef S = Saver.save(Config->DynamicLinker);
283   Ret->Data = {(const uint8_t *)S.data(), S.size() + 1};
284   return Ret;
285 }
286 
287 static size_t getHashSize() {
288   switch (Config->BuildId) {
289   case BuildIdKind::Fast:
290     return 8;
291   case BuildIdKind::Md5:
292   case BuildIdKind::Uuid:
293     return 16;
294   case BuildIdKind::Sha1:
295     return 20;
296   case BuildIdKind::Hexstring:
297     return Config->BuildIdVector.size();
298   default:
299     llvm_unreachable("unknown BuildIdKind");
300   }
301 }
302 
303 template <class ELFT>
304 BuildIdSection<ELFT>::BuildIdSection()
305     : SyntheticSection<ELFT>(SHF_ALLOC, SHT_NOTE, 1, ".note.gnu.build-id"),
306       HashSize(getHashSize()) {}
307 
308 template <class ELFT> void BuildIdSection<ELFT>::writeTo(uint8_t *Buf) {
309   const endianness E = ELFT::TargetEndianness;
310   write32<E>(Buf, 4);                   // Name size
311   write32<E>(Buf + 4, HashSize);        // Content size
312   write32<E>(Buf + 8, NT_GNU_BUILD_ID); // Type
313   memcpy(Buf + 12, "GNU", 4);           // Name string
314   HashBuf = Buf + 16;
315 }
316 
317 // Split one uint8 array into small pieces of uint8 arrays.
318 static std::vector<ArrayRef<uint8_t>> split(ArrayRef<uint8_t> Arr,
319                                             size_t ChunkSize) {
320   std::vector<ArrayRef<uint8_t>> Ret;
321   while (Arr.size() > ChunkSize) {
322     Ret.push_back(Arr.take_front(ChunkSize));
323     Arr = Arr.drop_front(ChunkSize);
324   }
325   if (!Arr.empty())
326     Ret.push_back(Arr);
327   return Ret;
328 }
329 
330 // Computes a hash value of Data using a given hash function.
331 // In order to utilize multiple cores, we first split data into 1MB
332 // chunks, compute a hash for each chunk, and then compute a hash value
333 // of the hash values.
334 template <class ELFT>
335 void BuildIdSection<ELFT>::computeHash(
336     llvm::ArrayRef<uint8_t> Data,
337     std::function<void(uint8_t *Dest, ArrayRef<uint8_t> Arr)> HashFn) {
338   std::vector<ArrayRef<uint8_t>> Chunks = split(Data, 1024 * 1024);
339   std::vector<uint8_t> Hashes(Chunks.size() * HashSize);
340 
341   // Compute hash values.
342   forLoop(0, Chunks.size(),
343           [&](size_t I) { HashFn(Hashes.data() + I * HashSize, Chunks[I]); });
344 
345   // Write to the final output buffer.
346   HashFn(HashBuf, Hashes);
347 }
348 
349 template <class ELFT>
350 void BuildIdSection<ELFT>::writeBuildId(ArrayRef<uint8_t> Buf) {
351   switch (Config->BuildId) {
352   case BuildIdKind::Fast:
353     computeHash(Buf, [](uint8_t *Dest, ArrayRef<uint8_t> Arr) {
354       write64le(Dest, xxHash64(toStringRef(Arr)));
355     });
356     break;
357   case BuildIdKind::Md5:
358     computeHash(Buf, [](uint8_t *Dest, ArrayRef<uint8_t> Arr) {
359       memcpy(Dest, MD5::hash(Arr).data(), 16);
360     });
361     break;
362   case BuildIdKind::Sha1:
363     computeHash(Buf, [](uint8_t *Dest, ArrayRef<uint8_t> Arr) {
364       memcpy(Dest, SHA1::hash(Arr).data(), 20);
365     });
366     break;
367   case BuildIdKind::Uuid:
368     if (getRandomBytes(HashBuf, HashSize))
369       error("entropy source failure");
370     break;
371   case BuildIdKind::Hexstring:
372     memcpy(HashBuf, Config->BuildIdVector.data(), Config->BuildIdVector.size());
373     break;
374   default:
375     llvm_unreachable("unknown BuildIdKind");
376   }
377 }
378 
379 template <class ELFT>
380 GotSection<ELFT>::GotSection()
381     : SyntheticSection<ELFT>(SHF_ALLOC | SHF_WRITE, SHT_PROGBITS,
382                              Target->GotEntrySize, ".got") {}
383 
384 template <class ELFT> void GotSection<ELFT>::addEntry(SymbolBody &Sym) {
385   Sym.GotIndex = NumEntries;
386   ++NumEntries;
387 }
388 
389 template <class ELFT> bool GotSection<ELFT>::addDynTlsEntry(SymbolBody &Sym) {
390   if (Sym.GlobalDynIndex != -1U)
391     return false;
392   Sym.GlobalDynIndex = NumEntries;
393   // Global Dynamic TLS entries take two GOT slots.
394   NumEntries += 2;
395   return true;
396 }
397 
398 // Reserves TLS entries for a TLS module ID and a TLS block offset.
399 // In total it takes two GOT slots.
400 template <class ELFT> bool GotSection<ELFT>::addTlsIndex() {
401   if (TlsIndexOff != uint32_t(-1))
402     return false;
403   TlsIndexOff = NumEntries * sizeof(uintX_t);
404   NumEntries += 2;
405   return true;
406 }
407 
408 template <class ELFT>
409 typename GotSection<ELFT>::uintX_t
410 GotSection<ELFT>::getGlobalDynAddr(const SymbolBody &B) const {
411   return this->getVA() + B.GlobalDynIndex * sizeof(uintX_t);
412 }
413 
414 template <class ELFT>
415 typename GotSection<ELFT>::uintX_t
416 GotSection<ELFT>::getGlobalDynOffset(const SymbolBody &B) const {
417   return B.GlobalDynIndex * sizeof(uintX_t);
418 }
419 
420 template <class ELFT> void GotSection<ELFT>::finalize() {
421   Size = NumEntries * sizeof(uintX_t);
422 }
423 
424 template <class ELFT> bool GotSection<ELFT>::empty() const {
425   // If we have a relocation that is relative to GOT (such as GOTOFFREL),
426   // we need to emit a GOT even if it's empty.
427   return NumEntries == 0 && !HasGotOffRel;
428 }
429 
430 template <class ELFT> void GotSection<ELFT>::writeTo(uint8_t *Buf) {
431   this->relocate(Buf, Buf + Size);
432 }
433 
434 template <class ELFT>
435 MipsGotSection<ELFT>::MipsGotSection()
436     : SyntheticSection<ELFT>(SHF_ALLOC | SHF_WRITE | SHF_MIPS_GPREL,
437                              SHT_PROGBITS, Target->GotEntrySize, ".got") {}
438 
439 template <class ELFT>
440 void MipsGotSection<ELFT>::addEntry(SymbolBody &Sym, uintX_t Addend,
441                                     RelExpr Expr) {
442   // For "true" local symbols which can be referenced from the same module
443   // only compiler creates two instructions for address loading:
444   //
445   // lw   $8, 0($gp) # R_MIPS_GOT16
446   // addi $8, $8, 0  # R_MIPS_LO16
447   //
448   // The first instruction loads high 16 bits of the symbol address while
449   // the second adds an offset. That allows to reduce number of required
450   // GOT entries because only one global offset table entry is necessary
451   // for every 64 KBytes of local data. So for local symbols we need to
452   // allocate number of GOT entries to hold all required "page" addresses.
453   //
454   // All global symbols (hidden and regular) considered by compiler uniformly.
455   // It always generates a single `lw` instruction and R_MIPS_GOT16 relocation
456   // to load address of the symbol. So for each such symbol we need to
457   // allocate dedicated GOT entry to store its address.
458   //
459   // If a symbol is preemptible we need help of dynamic linker to get its
460   // final address. The corresponding GOT entries are allocated in the
461   // "global" part of GOT. Entries for non preemptible global symbol allocated
462   // in the "local" part of GOT.
463   //
464   // See "Global Offset Table" in Chapter 5:
465   // ftp://www.linux-mips.org/pub/linux/mips/doc/ABI/mipsabi.pdf
466   if (Expr == R_MIPS_GOT_LOCAL_PAGE) {
467     // At this point we do not know final symbol value so to reduce number
468     // of allocated GOT entries do the following trick. Save all output
469     // sections referenced by GOT relocations. Then later in the `finalize`
470     // method calculate number of "pages" required to cover all saved output
471     // section and allocate appropriate number of GOT entries.
472     PageIndexMap.insert({cast<DefinedRegular<ELFT>>(&Sym)->Section->OutSec, 0});
473     return;
474   }
475   if (Sym.isTls()) {
476     // GOT entries created for MIPS TLS relocations behave like
477     // almost GOT entries from other ABIs. They go to the end
478     // of the global offset table.
479     Sym.GotIndex = TlsEntries.size();
480     TlsEntries.push_back(&Sym);
481     return;
482   }
483   auto AddEntry = [&](SymbolBody &S, uintX_t A, GotEntries &Items) {
484     if (S.isInGot() && !A)
485       return;
486     size_t NewIndex = Items.size();
487     if (!EntryIndexMap.insert({{&S, A}, NewIndex}).second)
488       return;
489     Items.emplace_back(&S, A);
490     if (!A)
491       S.GotIndex = NewIndex;
492   };
493   if (Sym.isPreemptible()) {
494     // Ignore addends for preemptible symbols. They got single GOT entry anyway.
495     AddEntry(Sym, 0, GlobalEntries);
496     Sym.IsInGlobalMipsGot = true;
497   } else if (Expr == R_MIPS_GOT_OFF32) {
498     AddEntry(Sym, Addend, LocalEntries32);
499     Sym.Is32BitMipsGot = true;
500   } else {
501     // Hold local GOT entries accessed via a 16-bit index separately.
502     // That allows to write them in the beginning of the GOT and keep
503     // their indexes as less as possible to escape relocation's overflow.
504     AddEntry(Sym, Addend, LocalEntries);
505   }
506 }
507 
508 template <class ELFT>
509 bool MipsGotSection<ELFT>::addDynTlsEntry(SymbolBody &Sym) {
510   if (Sym.GlobalDynIndex != -1U)
511     return false;
512   Sym.GlobalDynIndex = TlsEntries.size();
513   // Global Dynamic TLS entries take two GOT slots.
514   TlsEntries.push_back(nullptr);
515   TlsEntries.push_back(&Sym);
516   return true;
517 }
518 
519 // Reserves TLS entries for a TLS module ID and a TLS block offset.
520 // In total it takes two GOT slots.
521 template <class ELFT> bool MipsGotSection<ELFT>::addTlsIndex() {
522   if (TlsIndexOff != uint32_t(-1))
523     return false;
524   TlsIndexOff = TlsEntries.size() * sizeof(uintX_t);
525   TlsEntries.push_back(nullptr);
526   TlsEntries.push_back(nullptr);
527   return true;
528 }
529 
530 static uint64_t getMipsPageAddr(uint64_t Addr) {
531   return (Addr + 0x8000) & ~0xffff;
532 }
533 
534 static uint64_t getMipsPageCount(uint64_t Size) {
535   return (Size + 0xfffe) / 0xffff + 1;
536 }
537 
538 template <class ELFT>
539 typename MipsGotSection<ELFT>::uintX_t
540 MipsGotSection<ELFT>::getPageEntryOffset(const SymbolBody &B,
541                                          uintX_t Addend) const {
542   const OutputSectionBase *OutSec =
543       cast<DefinedRegular<ELFT>>(&B)->Section->OutSec;
544   uintX_t SecAddr = getMipsPageAddr(OutSec->Addr);
545   uintX_t SymAddr = getMipsPageAddr(B.getVA<ELFT>(Addend));
546   uintX_t Index = PageIndexMap.lookup(OutSec) + (SymAddr - SecAddr) / 0xffff;
547   assert(Index < PageEntriesNum);
548   return (HeaderEntriesNum + Index) * sizeof(uintX_t);
549 }
550 
551 template <class ELFT>
552 typename MipsGotSection<ELFT>::uintX_t
553 MipsGotSection<ELFT>::getBodyEntryOffset(const SymbolBody &B,
554                                          uintX_t Addend) const {
555   // Calculate offset of the GOT entries block: TLS, global, local.
556   uintX_t Index = HeaderEntriesNum + PageEntriesNum;
557   if (B.isTls())
558     Index += LocalEntries.size() + LocalEntries32.size() + GlobalEntries.size();
559   else if (B.IsInGlobalMipsGot)
560     Index += LocalEntries.size() + LocalEntries32.size();
561   else if (B.Is32BitMipsGot)
562     Index += LocalEntries.size();
563   // Calculate offset of the GOT entry in the block.
564   if (B.isInGot())
565     Index += B.GotIndex;
566   else {
567     auto It = EntryIndexMap.find({&B, Addend});
568     assert(It != EntryIndexMap.end());
569     Index += It->second;
570   }
571   return Index * sizeof(uintX_t);
572 }
573 
574 template <class ELFT>
575 typename MipsGotSection<ELFT>::uintX_t
576 MipsGotSection<ELFT>::getTlsOffset() const {
577   return (getLocalEntriesNum() + GlobalEntries.size()) * sizeof(uintX_t);
578 }
579 
580 template <class ELFT>
581 typename MipsGotSection<ELFT>::uintX_t
582 MipsGotSection<ELFT>::getGlobalDynOffset(const SymbolBody &B) const {
583   return B.GlobalDynIndex * sizeof(uintX_t);
584 }
585 
586 template <class ELFT>
587 const SymbolBody *MipsGotSection<ELFT>::getFirstGlobalEntry() const {
588   return GlobalEntries.empty() ? nullptr : GlobalEntries.front().first;
589 }
590 
591 template <class ELFT>
592 unsigned MipsGotSection<ELFT>::getLocalEntriesNum() const {
593   return HeaderEntriesNum + PageEntriesNum + LocalEntries.size() +
594          LocalEntries32.size();
595 }
596 
597 template <class ELFT> void MipsGotSection<ELFT>::finalize() {
598   PageEntriesNum = 0;
599   for (std::pair<const OutputSectionBase *, size_t> &P : PageIndexMap) {
600     // For each output section referenced by GOT page relocations calculate
601     // and save into PageIndexMap an upper bound of MIPS GOT entries required
602     // to store page addresses of local symbols. We assume the worst case -
603     // each 64kb page of the output section has at least one GOT relocation
604     // against it. And take in account the case when the section intersects
605     // page boundaries.
606     P.second = PageEntriesNum;
607     PageEntriesNum += getMipsPageCount(P.first->Size);
608   }
609   Size = (getLocalEntriesNum() + GlobalEntries.size() + TlsEntries.size()) *
610          sizeof(uintX_t);
611 }
612 
613 template <class ELFT> bool MipsGotSection<ELFT>::empty() const {
614   // We add the .got section to the result for dynamic MIPS target because
615   // its address and properties are mentioned in the .dynamic section.
616   return Config->Relocatable;
617 }
618 
619 template <class ELFT>
620 typename MipsGotSection<ELFT>::uintX_t MipsGotSection<ELFT>::getGp() const {
621   return ElfSym<ELFT>::MipsGp->template getVA<ELFT>(0);
622 }
623 
624 template <class ELFT>
625 static void writeUint(uint8_t *Buf, typename ELFT::uint Val) {
626   typedef typename ELFT::uint uintX_t;
627   write<uintX_t, ELFT::TargetEndianness, sizeof(uintX_t)>(Buf, Val);
628 }
629 
630 template <class ELFT> void MipsGotSection<ELFT>::writeTo(uint8_t *Buf) {
631   // Set the MSB of the second GOT slot. This is not required by any
632   // MIPS ABI documentation, though.
633   //
634   // There is a comment in glibc saying that "The MSB of got[1] of a
635   // gnu object is set to identify gnu objects," and in GNU gold it
636   // says "the second entry will be used by some runtime loaders".
637   // But how this field is being used is unclear.
638   //
639   // We are not really willing to mimic other linkers behaviors
640   // without understanding why they do that, but because all files
641   // generated by GNU tools have this special GOT value, and because
642   // we've been doing this for years, it is probably a safe bet to
643   // keep doing this for now. We really need to revisit this to see
644   // if we had to do this.
645   auto *P = reinterpret_cast<typename ELFT::Off *>(Buf);
646   P[1] = uintX_t(1) << (ELFT::Is64Bits ? 63 : 31);
647   Buf += HeaderEntriesNum * sizeof(uintX_t);
648   // Write 'page address' entries to the local part of the GOT.
649   for (std::pair<const OutputSectionBase *, size_t> &L : PageIndexMap) {
650     size_t PageCount = getMipsPageCount(L.first->Size);
651     uintX_t FirstPageAddr = getMipsPageAddr(L.first->Addr);
652     for (size_t PI = 0; PI < PageCount; ++PI) {
653       uint8_t *Entry = Buf + (L.second + PI) * sizeof(uintX_t);
654       writeUint<ELFT>(Entry, FirstPageAddr + PI * 0x10000);
655     }
656   }
657   Buf += PageEntriesNum * sizeof(uintX_t);
658   auto AddEntry = [&](const GotEntry &SA) {
659     uint8_t *Entry = Buf;
660     Buf += sizeof(uintX_t);
661     const SymbolBody *Body = SA.first;
662     uintX_t VA = Body->template getVA<ELFT>(SA.second);
663     writeUint<ELFT>(Entry, VA);
664   };
665   std::for_each(std::begin(LocalEntries), std::end(LocalEntries), AddEntry);
666   std::for_each(std::begin(LocalEntries32), std::end(LocalEntries32), AddEntry);
667   std::for_each(std::begin(GlobalEntries), std::end(GlobalEntries), AddEntry);
668   // Initialize TLS-related GOT entries. If the entry has a corresponding
669   // dynamic relocations, leave it initialized by zero. Write down adjusted
670   // TLS symbol's values otherwise. To calculate the adjustments use offsets
671   // for thread-local storage.
672   // https://www.linux-mips.org/wiki/NPTL
673   if (TlsIndexOff != -1U && !Config->Pic)
674     writeUint<ELFT>(Buf + TlsIndexOff, 1);
675   for (const SymbolBody *B : TlsEntries) {
676     if (!B || B->isPreemptible())
677       continue;
678     uintX_t VA = B->getVA<ELFT>();
679     if (B->GotIndex != -1U) {
680       uint8_t *Entry = Buf + B->GotIndex * sizeof(uintX_t);
681       writeUint<ELFT>(Entry, VA - 0x7000);
682     }
683     if (B->GlobalDynIndex != -1U) {
684       uint8_t *Entry = Buf + B->GlobalDynIndex * sizeof(uintX_t);
685       writeUint<ELFT>(Entry, 1);
686       Entry += sizeof(uintX_t);
687       writeUint<ELFT>(Entry, VA - 0x8000);
688     }
689   }
690 }
691 
692 template <class ELFT>
693 GotPltSection<ELFT>::GotPltSection()
694     : SyntheticSection<ELFT>(SHF_ALLOC | SHF_WRITE, SHT_PROGBITS,
695                              Target->GotPltEntrySize, ".got.plt") {}
696 
697 template <class ELFT> void GotPltSection<ELFT>::addEntry(SymbolBody &Sym) {
698   Sym.GotPltIndex = Target->GotPltHeaderEntriesNum + Entries.size();
699   Entries.push_back(&Sym);
700 }
701 
702 template <class ELFT> size_t GotPltSection<ELFT>::getSize() const {
703   return (Target->GotPltHeaderEntriesNum + Entries.size()) *
704          Target->GotPltEntrySize;
705 }
706 
707 template <class ELFT> void GotPltSection<ELFT>::writeTo(uint8_t *Buf) {
708   Target->writeGotPltHeader(Buf);
709   Buf += Target->GotPltHeaderEntriesNum * Target->GotPltEntrySize;
710   for (const SymbolBody *B : Entries) {
711     Target->writeGotPlt(Buf, *B);
712     Buf += sizeof(uintX_t);
713   }
714 }
715 
716 // On ARM the IgotPltSection is part of the GotSection, on other Targets it is
717 // part of the .got.plt
718 template <class ELFT>
719 IgotPltSection<ELFT>::IgotPltSection()
720     : SyntheticSection<ELFT>(SHF_ALLOC | SHF_WRITE, SHT_PROGBITS,
721                              Target->GotPltEntrySize,
722                              Config->EMachine == EM_ARM ? ".got" : ".got.plt") {
723 }
724 
725 template <class ELFT> void IgotPltSection<ELFT>::addEntry(SymbolBody &Sym) {
726   Sym.IsInIgot = true;
727   Sym.GotPltIndex = Entries.size();
728   Entries.push_back(&Sym);
729 }
730 
731 template <class ELFT> size_t IgotPltSection<ELFT>::getSize() const {
732   return Entries.size() * Target->GotPltEntrySize;
733 }
734 
735 template <class ELFT> void IgotPltSection<ELFT>::writeTo(uint8_t *Buf) {
736   for (const SymbolBody *B : Entries) {
737     Target->writeIgotPlt(Buf, *B);
738     Buf += sizeof(uintX_t);
739   }
740 }
741 
742 template <class ELFT>
743 StringTableSection<ELFT>::StringTableSection(StringRef Name, bool Dynamic)
744     : SyntheticSection<ELFT>(Dynamic ? (uintX_t)SHF_ALLOC : 0, SHT_STRTAB, 1,
745                              Name),
746       Dynamic(Dynamic) {}
747 
748 // Adds a string to the string table. If HashIt is true we hash and check for
749 // duplicates. It is optional because the name of global symbols are already
750 // uniqued and hashing them again has a big cost for a small value: uniquing
751 // them with some other string that happens to be the same.
752 template <class ELFT>
753 unsigned StringTableSection<ELFT>::addString(StringRef S, bool HashIt) {
754   if (HashIt) {
755     auto R = StringMap.insert(std::make_pair(S, this->Size));
756     if (!R.second)
757       return R.first->second;
758   }
759   unsigned Ret = this->Size;
760   this->Size = this->Size + S.size() + 1;
761   Strings.push_back(S);
762   return Ret;
763 }
764 
765 template <class ELFT> void StringTableSection<ELFT>::writeTo(uint8_t *Buf) {
766   // ELF string tables start with NUL byte, so advance the pointer by one.
767   ++Buf;
768   for (StringRef S : Strings) {
769     memcpy(Buf, S.data(), S.size());
770     Buf += S.size() + 1;
771   }
772 }
773 
774 // Returns the number of version definition entries. Because the first entry
775 // is for the version definition itself, it is the number of versioned symbols
776 // plus one. Note that we don't support multiple versions yet.
777 static unsigned getVerDefNum() { return Config->VersionDefinitions.size() + 1; }
778 
779 template <class ELFT>
780 DynamicSection<ELFT>::DynamicSection()
781     : SyntheticSection<ELFT>(SHF_ALLOC | SHF_WRITE, SHT_DYNAMIC,
782                              sizeof(uintX_t), ".dynamic") {
783   this->Entsize = ELFT::Is64Bits ? 16 : 8;
784   // .dynamic section is not writable on MIPS.
785   // See "Special Section" in Chapter 4 in the following document:
786   // ftp://www.linux-mips.org/pub/linux/mips/doc/ABI/mipsabi.pdf
787   if (Config->EMachine == EM_MIPS)
788     this->Flags = SHF_ALLOC;
789 
790   addEntries();
791 }
792 
793 // There are some dynamic entries that don't depend on other sections.
794 // Such entries can be set early.
795 template <class ELFT> void DynamicSection<ELFT>::addEntries() {
796   // Add strings to .dynstr early so that .dynstr's size will be
797   // fixed early.
798   for (StringRef S : Config->AuxiliaryList)
799     add({DT_AUXILIARY, In<ELFT>::DynStrTab->addString(S)});
800   if (!Config->RPath.empty())
801     add({Config->EnableNewDtags ? DT_RUNPATH : DT_RPATH,
802          In<ELFT>::DynStrTab->addString(Config->RPath)});
803   for (SharedFile<ELFT> *F : Symtab<ELFT>::X->getSharedFiles())
804     if (F->isNeeded())
805       add({DT_NEEDED, In<ELFT>::DynStrTab->addString(F->getSoName())});
806   if (!Config->SoName.empty())
807     add({DT_SONAME, In<ELFT>::DynStrTab->addString(Config->SoName)});
808 
809   // Set DT_FLAGS and DT_FLAGS_1.
810   uint32_t DtFlags = 0;
811   uint32_t DtFlags1 = 0;
812   if (Config->Bsymbolic)
813     DtFlags |= DF_SYMBOLIC;
814   if (Config->ZNodelete)
815     DtFlags1 |= DF_1_NODELETE;
816   if (Config->ZNow) {
817     DtFlags |= DF_BIND_NOW;
818     DtFlags1 |= DF_1_NOW;
819   }
820   if (Config->ZOrigin) {
821     DtFlags |= DF_ORIGIN;
822     DtFlags1 |= DF_1_ORIGIN;
823   }
824 
825   if (DtFlags)
826     add({DT_FLAGS, DtFlags});
827   if (DtFlags1)
828     add({DT_FLAGS_1, DtFlags1});
829 
830   if (!Config->Shared && !Config->Relocatable)
831     add({DT_DEBUG, (uint64_t)0});
832 }
833 
834 // Add remaining entries to complete .dynamic contents.
835 template <class ELFT> void DynamicSection<ELFT>::finalize() {
836   if (this->Size)
837     return; // Already finalized.
838 
839   this->Link = In<ELFT>::DynStrTab->OutSec->SectionIndex;
840   if (In<ELFT>::RelaDyn->OutSec->Size > 0) {
841     bool IsRela = Config->Rela;
842     add({IsRela ? DT_RELA : DT_REL, In<ELFT>::RelaDyn});
843     add({IsRela ? DT_RELASZ : DT_RELSZ, In<ELFT>::RelaDyn->OutSec->Size});
844     add({IsRela ? DT_RELAENT : DT_RELENT,
845          uintX_t(IsRela ? sizeof(Elf_Rela) : sizeof(Elf_Rel))});
846 
847     // MIPS dynamic loader does not support RELCOUNT tag.
848     // The problem is in the tight relation between dynamic
849     // relocations and GOT. So do not emit this tag on MIPS.
850     if (Config->EMachine != EM_MIPS) {
851       size_t NumRelativeRels = In<ELFT>::RelaDyn->getRelativeRelocCount();
852       if (Config->ZCombreloc && NumRelativeRels)
853         add({IsRela ? DT_RELACOUNT : DT_RELCOUNT, NumRelativeRels});
854     }
855   }
856   if (In<ELFT>::RelaPlt->OutSec->Size > 0) {
857     add({DT_JMPREL, In<ELFT>::RelaPlt});
858     add({DT_PLTRELSZ, In<ELFT>::RelaPlt->OutSec->Size});
859     add({Config->EMachine == EM_MIPS ? DT_MIPS_PLTGOT : DT_PLTGOT,
860          In<ELFT>::GotPlt});
861     add({DT_PLTREL, uint64_t(Config->Rela ? DT_RELA : DT_REL)});
862   }
863 
864   add({DT_SYMTAB, In<ELFT>::DynSymTab});
865   add({DT_SYMENT, sizeof(Elf_Sym)});
866   add({DT_STRTAB, In<ELFT>::DynStrTab});
867   add({DT_STRSZ, In<ELFT>::DynStrTab->getSize()});
868   if (In<ELFT>::GnuHashTab)
869     add({DT_GNU_HASH, In<ELFT>::GnuHashTab});
870   if (In<ELFT>::HashTab)
871     add({DT_HASH, In<ELFT>::HashTab});
872 
873   if (Out<ELFT>::PreinitArray) {
874     add({DT_PREINIT_ARRAY, Out<ELFT>::PreinitArray});
875     add({DT_PREINIT_ARRAYSZ, Out<ELFT>::PreinitArray, Entry::SecSize});
876   }
877   if (Out<ELFT>::InitArray) {
878     add({DT_INIT_ARRAY, Out<ELFT>::InitArray});
879     add({DT_INIT_ARRAYSZ, Out<ELFT>::InitArray, Entry::SecSize});
880   }
881   if (Out<ELFT>::FiniArray) {
882     add({DT_FINI_ARRAY, Out<ELFT>::FiniArray});
883     add({DT_FINI_ARRAYSZ, Out<ELFT>::FiniArray, Entry::SecSize});
884   }
885 
886   if (SymbolBody *B = Symtab<ELFT>::X->find(Config->Init))
887     add({DT_INIT, B});
888   if (SymbolBody *B = Symtab<ELFT>::X->find(Config->Fini))
889     add({DT_FINI, B});
890 
891   bool HasVerNeed = In<ELFT>::VerNeed->getNeedNum() != 0;
892   if (HasVerNeed || In<ELFT>::VerDef)
893     add({DT_VERSYM, In<ELFT>::VerSym});
894   if (In<ELFT>::VerDef) {
895     add({DT_VERDEF, In<ELFT>::VerDef});
896     add({DT_VERDEFNUM, getVerDefNum()});
897   }
898   if (HasVerNeed) {
899     add({DT_VERNEED, In<ELFT>::VerNeed});
900     add({DT_VERNEEDNUM, In<ELFT>::VerNeed->getNeedNum()});
901   }
902 
903   if (Config->EMachine == EM_MIPS) {
904     add({DT_MIPS_RLD_VERSION, 1});
905     add({DT_MIPS_FLAGS, RHF_NOTPOT});
906     add({DT_MIPS_BASE_ADDRESS, Config->ImageBase});
907     add({DT_MIPS_SYMTABNO, In<ELFT>::DynSymTab->getNumSymbols()});
908     add({DT_MIPS_LOCAL_GOTNO, In<ELFT>::MipsGot->getLocalEntriesNum()});
909     if (const SymbolBody *B = In<ELFT>::MipsGot->getFirstGlobalEntry())
910       add({DT_MIPS_GOTSYM, B->DynsymIndex});
911     else
912       add({DT_MIPS_GOTSYM, In<ELFT>::DynSymTab->getNumSymbols()});
913     add({DT_PLTGOT, In<ELFT>::MipsGot});
914     if (In<ELFT>::MipsRldMap)
915       add({DT_MIPS_RLD_MAP, In<ELFT>::MipsRldMap});
916   }
917 
918   this->OutSec->Entsize = this->Entsize;
919   this->OutSec->Link = this->Link;
920 
921   // +1 for DT_NULL
922   this->Size = (Entries.size() + 1) * this->Entsize;
923 }
924 
925 template <class ELFT> void DynamicSection<ELFT>::writeTo(uint8_t *Buf) {
926   auto *P = reinterpret_cast<Elf_Dyn *>(Buf);
927 
928   for (const Entry &E : Entries) {
929     P->d_tag = E.Tag;
930     switch (E.Kind) {
931     case Entry::SecAddr:
932       P->d_un.d_ptr = E.OutSec->Addr;
933       break;
934     case Entry::InSecAddr:
935       P->d_un.d_ptr = E.InSec->OutSec->Addr + E.InSec->OutSecOff;
936       break;
937     case Entry::SecSize:
938       P->d_un.d_val = E.OutSec->Size;
939       break;
940     case Entry::SymAddr:
941       P->d_un.d_ptr = E.Sym->template getVA<ELFT>();
942       break;
943     case Entry::PlainInt:
944       P->d_un.d_val = E.Val;
945       break;
946     }
947     ++P;
948   }
949 }
950 
951 template <class ELFT>
952 typename ELFT::uint DynamicReloc<ELFT>::getOffset() const {
953   if (OutputSec)
954     return OutputSec->Addr + OffsetInSec;
955   return InputSec->OutSec->Addr + InputSec->getOffset(OffsetInSec);
956 }
957 
958 template <class ELFT>
959 typename ELFT::uint DynamicReloc<ELFT>::getAddend() const {
960   if (UseSymVA)
961     return Sym->getVA<ELFT>(Addend);
962   return Addend;
963 }
964 
965 template <class ELFT> uint32_t DynamicReloc<ELFT>::getSymIndex() const {
966   if (Sym && !UseSymVA)
967     return Sym->DynsymIndex;
968   return 0;
969 }
970 
971 template <class ELFT>
972 RelocationSection<ELFT>::RelocationSection(StringRef Name, bool Sort)
973     : SyntheticSection<ELFT>(SHF_ALLOC, Config->Rela ? SHT_RELA : SHT_REL,
974                              sizeof(uintX_t), Name),
975       Sort(Sort) {
976   this->Entsize = Config->Rela ? sizeof(Elf_Rela) : sizeof(Elf_Rel);
977 }
978 
979 template <class ELFT>
980 void RelocationSection<ELFT>::addReloc(const DynamicReloc<ELFT> &Reloc) {
981   if (Reloc.Type == Target->RelativeRel)
982     ++NumRelativeRelocs;
983   Relocs.push_back(Reloc);
984 }
985 
986 template <class ELFT, class RelTy>
987 static bool compRelocations(const RelTy &A, const RelTy &B) {
988   bool AIsRel = A.getType(Config->Mips64EL) == Target->RelativeRel;
989   bool BIsRel = B.getType(Config->Mips64EL) == Target->RelativeRel;
990   if (AIsRel != BIsRel)
991     return AIsRel;
992 
993   return A.getSymbol(Config->Mips64EL) < B.getSymbol(Config->Mips64EL);
994 }
995 
996 template <class ELFT> void RelocationSection<ELFT>::writeTo(uint8_t *Buf) {
997   uint8_t *BufBegin = Buf;
998   for (const DynamicReloc<ELFT> &Rel : Relocs) {
999     auto *P = reinterpret_cast<Elf_Rela *>(Buf);
1000     Buf += Config->Rela ? sizeof(Elf_Rela) : sizeof(Elf_Rel);
1001 
1002     if (Config->Rela)
1003       P->r_addend = Rel.getAddend();
1004     P->r_offset = Rel.getOffset();
1005     if (Config->EMachine == EM_MIPS && Rel.getInputSec() == In<ELFT>::MipsGot)
1006       // Dynamic relocation against MIPS GOT section make deal TLS entries
1007       // allocated in the end of the GOT. We need to adjust the offset to take
1008       // in account 'local' and 'global' GOT entries.
1009       P->r_offset += In<ELFT>::MipsGot->getTlsOffset();
1010     P->setSymbolAndType(Rel.getSymIndex(), Rel.Type, Config->Mips64EL);
1011   }
1012 
1013   if (Sort) {
1014     if (Config->Rela)
1015       std::stable_sort((Elf_Rela *)BufBegin,
1016                        (Elf_Rela *)BufBegin + Relocs.size(),
1017                        compRelocations<ELFT, Elf_Rela>);
1018     else
1019       std::stable_sort((Elf_Rel *)BufBegin, (Elf_Rel *)BufBegin + Relocs.size(),
1020                        compRelocations<ELFT, Elf_Rel>);
1021   }
1022 }
1023 
1024 template <class ELFT> unsigned RelocationSection<ELFT>::getRelocOffset() {
1025   return this->Entsize * Relocs.size();
1026 }
1027 
1028 template <class ELFT> void RelocationSection<ELFT>::finalize() {
1029   this->Link = In<ELFT>::DynSymTab ? In<ELFT>::DynSymTab->OutSec->SectionIndex
1030                                    : In<ELFT>::SymTab->OutSec->SectionIndex;
1031 
1032   // Set required output section properties.
1033   this->OutSec->Link = this->Link;
1034   this->OutSec->Entsize = this->Entsize;
1035 }
1036 
1037 template <class ELFT>
1038 SymbolTableSection<ELFT>::SymbolTableSection(
1039     StringTableSection<ELFT> &StrTabSec)
1040     : SyntheticSection<ELFT>(StrTabSec.isDynamic() ? (uintX_t)SHF_ALLOC : 0,
1041                              StrTabSec.isDynamic() ? SHT_DYNSYM : SHT_SYMTAB,
1042                              sizeof(uintX_t),
1043                              StrTabSec.isDynamic() ? ".dynsym" : ".symtab"),
1044       StrTabSec(StrTabSec) {
1045   this->Entsize = sizeof(Elf_Sym);
1046 }
1047 
1048 // Orders symbols according to their positions in the GOT,
1049 // in compliance with MIPS ABI rules.
1050 // See "Global Offset Table" in Chapter 5 in the following document
1051 // for detailed description:
1052 // ftp://www.linux-mips.org/pub/linux/mips/doc/ABI/mipsabi.pdf
1053 static bool sortMipsSymbols(const SymbolBody *L, const SymbolBody *R) {
1054   // Sort entries related to non-local preemptible symbols by GOT indexes.
1055   // All other entries go to the first part of GOT in arbitrary order.
1056   bool LIsInLocalGot = !L->IsInGlobalMipsGot;
1057   bool RIsInLocalGot = !R->IsInGlobalMipsGot;
1058   if (LIsInLocalGot || RIsInLocalGot)
1059     return !RIsInLocalGot;
1060   return L->GotIndex < R->GotIndex;
1061 }
1062 
1063 template <class ELFT> void SymbolTableSection<ELFT>::finalize() {
1064   this->OutSec->Link = this->Link = StrTabSec.OutSec->SectionIndex;
1065   this->OutSec->Info = this->Info = NumLocals + 1;
1066   this->OutSec->Entsize = this->Entsize;
1067 
1068   if (Config->Relocatable) {
1069     size_t I = NumLocals;
1070     for (const SymbolTableEntry &S : Symbols)
1071       S.Symbol->DynsymIndex = ++I;
1072     return;
1073   }
1074 
1075   if (!StrTabSec.isDynamic()) {
1076     std::stable_sort(
1077         Symbols.begin(), Symbols.end(),
1078         [](const SymbolTableEntry &L, const SymbolTableEntry &R) {
1079           return L.Symbol->symbol()->computeBinding() == STB_LOCAL &&
1080                  R.Symbol->symbol()->computeBinding() != STB_LOCAL;
1081         });
1082     return;
1083   }
1084   if (In<ELFT>::GnuHashTab)
1085     // NB: It also sorts Symbols to meet the GNU hash table requirements.
1086     In<ELFT>::GnuHashTab->addSymbols(Symbols);
1087   else if (Config->EMachine == EM_MIPS)
1088     std::stable_sort(Symbols.begin(), Symbols.end(),
1089                      [](const SymbolTableEntry &L, const SymbolTableEntry &R) {
1090                        return sortMipsSymbols(L.Symbol, R.Symbol);
1091                      });
1092   size_t I = 0;
1093   for (const SymbolTableEntry &S : Symbols)
1094     S.Symbol->DynsymIndex = ++I;
1095 }
1096 
1097 template <class ELFT> void SymbolTableSection<ELFT>::addSymbol(SymbolBody *B) {
1098   Symbols.push_back({B, StrTabSec.addString(B->getName(), false)});
1099 }
1100 
1101 template <class ELFT> void SymbolTableSection<ELFT>::writeTo(uint8_t *Buf) {
1102   Buf += sizeof(Elf_Sym);
1103 
1104   // All symbols with STB_LOCAL binding precede the weak and global symbols.
1105   // .dynsym only contains global symbols.
1106   if (Config->Discard != DiscardPolicy::All && !StrTabSec.isDynamic())
1107     writeLocalSymbols(Buf);
1108 
1109   writeGlobalSymbols(Buf);
1110 }
1111 
1112 template <class ELFT>
1113 void SymbolTableSection<ELFT>::writeLocalSymbols(uint8_t *&Buf) {
1114   // Iterate over all input object files to copy their local symbols
1115   // to the output symbol table pointed by Buf.
1116   for (ObjectFile<ELFT> *File : Symtab<ELFT>::X->getObjectFiles()) {
1117     for (const std::pair<const DefinedRegular<ELFT> *, size_t> &P :
1118          File->KeptLocalSyms) {
1119       const DefinedRegular<ELFT> &Body = *P.first;
1120       InputSectionBase<ELFT> *Section = Body.Section;
1121       auto *ESym = reinterpret_cast<Elf_Sym *>(Buf);
1122 
1123       if (!Section) {
1124         ESym->st_shndx = SHN_ABS;
1125         ESym->st_value = Body.Value;
1126       } else {
1127         const OutputSectionBase *OutSec = Section->OutSec;
1128         ESym->st_shndx = OutSec->SectionIndex;
1129         ESym->st_value = OutSec->Addr + Section->getOffset(Body);
1130       }
1131       ESym->st_name = P.second;
1132       ESym->st_size = Body.template getSize<ELFT>();
1133       ESym->setBindingAndType(STB_LOCAL, Body.Type);
1134       Buf += sizeof(*ESym);
1135     }
1136   }
1137 }
1138 
1139 template <class ELFT>
1140 void SymbolTableSection<ELFT>::writeGlobalSymbols(uint8_t *Buf) {
1141   // Write the internal symbol table contents to the output symbol table
1142   // pointed by Buf.
1143   auto *ESym = reinterpret_cast<Elf_Sym *>(Buf);
1144   for (const SymbolTableEntry &S : Symbols) {
1145     SymbolBody *Body = S.Symbol;
1146     size_t StrOff = S.StrTabOffset;
1147 
1148     uint8_t Type = Body->Type;
1149     uintX_t Size = Body->getSize<ELFT>();
1150 
1151     ESym->setBindingAndType(Body->symbol()->computeBinding(), Type);
1152     ESym->st_size = Size;
1153     ESym->st_name = StrOff;
1154     ESym->setVisibility(Body->symbol()->Visibility);
1155     ESym->st_value = Body->getVA<ELFT>();
1156 
1157     if (const OutputSectionBase *OutSec = getOutputSection(Body))
1158       ESym->st_shndx = OutSec->SectionIndex;
1159     else if (isa<DefinedRegular<ELFT>>(Body))
1160       ESym->st_shndx = SHN_ABS;
1161 
1162     if (Config->EMachine == EM_MIPS) {
1163       // On MIPS we need to mark symbol which has a PLT entry and requires
1164       // pointer equality by STO_MIPS_PLT flag. That is necessary to help
1165       // dynamic linker distinguish such symbols and MIPS lazy-binding stubs.
1166       // https://sourceware.org/ml/binutils/2008-07/txt00000.txt
1167       if (Body->isInPlt() && Body->NeedsCopyOrPltAddr)
1168         ESym->st_other |= STO_MIPS_PLT;
1169       if (Config->Relocatable) {
1170         auto *D = dyn_cast<DefinedRegular<ELFT>>(Body);
1171         if (D && D->isMipsPIC())
1172           ESym->st_other |= STO_MIPS_PIC;
1173       }
1174     }
1175     ++ESym;
1176   }
1177 }
1178 
1179 template <class ELFT>
1180 const OutputSectionBase *
1181 SymbolTableSection<ELFT>::getOutputSection(SymbolBody *Sym) {
1182   switch (Sym->kind()) {
1183   case SymbolBody::DefinedSyntheticKind:
1184     return cast<DefinedSynthetic>(Sym)->Section;
1185   case SymbolBody::DefinedRegularKind: {
1186     auto &D = cast<DefinedRegular<ELFT>>(*Sym);
1187     if (D.Section)
1188       return D.Section->OutSec;
1189     break;
1190   }
1191   case SymbolBody::DefinedCommonKind:
1192     return In<ELFT>::Common->OutSec;
1193   case SymbolBody::SharedKind: {
1194     auto &SS = cast<SharedSymbol<ELFT>>(*Sym);
1195     if (SS.needsCopy())
1196       return SS.getBssSectionForCopy();
1197     break;
1198   }
1199   case SymbolBody::UndefinedKind:
1200   case SymbolBody::LazyArchiveKind:
1201   case SymbolBody::LazyObjectKind:
1202     break;
1203   }
1204   return nullptr;
1205 }
1206 
1207 template <class ELFT>
1208 GnuHashTableSection<ELFT>::GnuHashTableSection()
1209     : SyntheticSection<ELFT>(SHF_ALLOC, SHT_GNU_HASH, sizeof(uintX_t),
1210                              ".gnu.hash") {
1211   this->Entsize = ELFT::Is64Bits ? 0 : 4;
1212 }
1213 
1214 template <class ELFT>
1215 unsigned GnuHashTableSection<ELFT>::calcNBuckets(unsigned NumHashed) {
1216   if (!NumHashed)
1217     return 0;
1218 
1219   // These values are prime numbers which are not greater than 2^(N-1) + 1.
1220   // In result, for any particular NumHashed we return a prime number
1221   // which is not greater than NumHashed.
1222   static const unsigned Primes[] = {
1223       1,   1,    3,    3,    7,    13,    31,    61,    127,   251,
1224       509, 1021, 2039, 4093, 8191, 16381, 32749, 65521, 131071};
1225 
1226   return Primes[std::min<unsigned>(Log2_32_Ceil(NumHashed),
1227                                    array_lengthof(Primes) - 1)];
1228 }
1229 
1230 // Bloom filter estimation: at least 8 bits for each hashed symbol.
1231 // GNU Hash table requirement: it should be a power of 2,
1232 //   the minimum value is 1, even for an empty table.
1233 // Expected results for a 32-bit target:
1234 //   calcMaskWords(0..4)   = 1
1235 //   calcMaskWords(5..8)   = 2
1236 //   calcMaskWords(9..16)  = 4
1237 // For a 64-bit target:
1238 //   calcMaskWords(0..8)   = 1
1239 //   calcMaskWords(9..16)  = 2
1240 //   calcMaskWords(17..32) = 4
1241 template <class ELFT>
1242 unsigned GnuHashTableSection<ELFT>::calcMaskWords(unsigned NumHashed) {
1243   if (!NumHashed)
1244     return 1;
1245   return NextPowerOf2((NumHashed - 1) / sizeof(Elf_Off));
1246 }
1247 
1248 template <class ELFT> void GnuHashTableSection<ELFT>::finalize() {
1249   unsigned NumHashed = Symbols.size();
1250   NBuckets = calcNBuckets(NumHashed);
1251   MaskWords = calcMaskWords(NumHashed);
1252   // Second hash shift estimation: just predefined values.
1253   Shift2 = ELFT::Is64Bits ? 6 : 5;
1254 
1255   this->OutSec->Entsize = this->Entsize;
1256   this->OutSec->Link = this->Link = In<ELFT>::DynSymTab->OutSec->SectionIndex;
1257   this->Size = sizeof(Elf_Word) * 4            // Header
1258                + sizeof(Elf_Off) * MaskWords   // Bloom Filter
1259                + sizeof(Elf_Word) * NBuckets   // Hash Buckets
1260                + sizeof(Elf_Word) * NumHashed; // Hash Values
1261 }
1262 
1263 template <class ELFT> void GnuHashTableSection<ELFT>::writeTo(uint8_t *Buf) {
1264   writeHeader(Buf);
1265   if (Symbols.empty())
1266     return;
1267   writeBloomFilter(Buf);
1268   writeHashTable(Buf);
1269 }
1270 
1271 template <class ELFT>
1272 void GnuHashTableSection<ELFT>::writeHeader(uint8_t *&Buf) {
1273   auto *P = reinterpret_cast<Elf_Word *>(Buf);
1274   *P++ = NBuckets;
1275   *P++ = In<ELFT>::DynSymTab->getNumSymbols() - Symbols.size();
1276   *P++ = MaskWords;
1277   *P++ = Shift2;
1278   Buf = reinterpret_cast<uint8_t *>(P);
1279 }
1280 
1281 template <class ELFT>
1282 void GnuHashTableSection<ELFT>::writeBloomFilter(uint8_t *&Buf) {
1283   unsigned C = sizeof(Elf_Off) * 8;
1284 
1285   auto *Masks = reinterpret_cast<Elf_Off *>(Buf);
1286   for (const SymbolData &Sym : Symbols) {
1287     size_t Pos = (Sym.Hash / C) & (MaskWords - 1);
1288     uintX_t V = (uintX_t(1) << (Sym.Hash % C)) |
1289                 (uintX_t(1) << ((Sym.Hash >> Shift2) % C));
1290     Masks[Pos] |= V;
1291   }
1292   Buf += sizeof(Elf_Off) * MaskWords;
1293 }
1294 
1295 template <class ELFT>
1296 void GnuHashTableSection<ELFT>::writeHashTable(uint8_t *Buf) {
1297   Elf_Word *Buckets = reinterpret_cast<Elf_Word *>(Buf);
1298   Elf_Word *Values = Buckets + NBuckets;
1299 
1300   int PrevBucket = -1;
1301   int I = 0;
1302   for (const SymbolData &Sym : Symbols) {
1303     int Bucket = Sym.Hash % NBuckets;
1304     assert(PrevBucket <= Bucket);
1305     if (Bucket != PrevBucket) {
1306       Buckets[Bucket] = Sym.Body->DynsymIndex;
1307       PrevBucket = Bucket;
1308       if (I > 0)
1309         Values[I - 1] |= 1;
1310     }
1311     Values[I] = Sym.Hash & ~1;
1312     ++I;
1313   }
1314   if (I > 0)
1315     Values[I - 1] |= 1;
1316 }
1317 
1318 static uint32_t hashGnu(StringRef Name) {
1319   uint32_t H = 5381;
1320   for (uint8_t C : Name)
1321     H = (H << 5) + H + C;
1322   return H;
1323 }
1324 
1325 // Add symbols to this symbol hash table. Note that this function
1326 // destructively sort a given vector -- which is needed because
1327 // GNU-style hash table places some sorting requirements.
1328 template <class ELFT>
1329 void GnuHashTableSection<ELFT>::addSymbols(std::vector<SymbolTableEntry> &V) {
1330   // Ideally this will just be 'auto' but GCC 6.1 is not able
1331   // to deduce it correctly.
1332   std::vector<SymbolTableEntry>::iterator Mid =
1333       std::stable_partition(V.begin(), V.end(), [](const SymbolTableEntry &S) {
1334         return S.Symbol->isUndefined();
1335       });
1336   if (Mid == V.end())
1337     return;
1338   for (auto I = Mid, E = V.end(); I != E; ++I) {
1339     SymbolBody *B = I->Symbol;
1340     size_t StrOff = I->StrTabOffset;
1341     Symbols.push_back({B, StrOff, hashGnu(B->getName())});
1342   }
1343 
1344   unsigned NBuckets = calcNBuckets(Symbols.size());
1345   std::stable_sort(Symbols.begin(), Symbols.end(),
1346                    [&](const SymbolData &L, const SymbolData &R) {
1347                      return L.Hash % NBuckets < R.Hash % NBuckets;
1348                    });
1349 
1350   V.erase(Mid, V.end());
1351   for (const SymbolData &Sym : Symbols)
1352     V.push_back({Sym.Body, Sym.STName});
1353 }
1354 
1355 template <class ELFT>
1356 HashTableSection<ELFT>::HashTableSection()
1357     : SyntheticSection<ELFT>(SHF_ALLOC, SHT_HASH, sizeof(Elf_Word), ".hash") {
1358   this->Entsize = sizeof(Elf_Word);
1359 }
1360 
1361 template <class ELFT> void HashTableSection<ELFT>::finalize() {
1362   this->OutSec->Link = this->Link = In<ELFT>::DynSymTab->OutSec->SectionIndex;
1363   this->OutSec->Entsize = this->Entsize;
1364 
1365   unsigned NumEntries = 2;                            // nbucket and nchain.
1366   NumEntries += In<ELFT>::DynSymTab->getNumSymbols(); // The chain entries.
1367 
1368   // Create as many buckets as there are symbols.
1369   // FIXME: This is simplistic. We can try to optimize it, but implementing
1370   // support for SHT_GNU_HASH is probably even more profitable.
1371   NumEntries += In<ELFT>::DynSymTab->getNumSymbols();
1372   this->Size = NumEntries * sizeof(Elf_Word);
1373 }
1374 
1375 template <class ELFT> void HashTableSection<ELFT>::writeTo(uint8_t *Buf) {
1376   unsigned NumSymbols = In<ELFT>::DynSymTab->getNumSymbols();
1377   auto *P = reinterpret_cast<Elf_Word *>(Buf);
1378   *P++ = NumSymbols; // nbucket
1379   *P++ = NumSymbols; // nchain
1380 
1381   Elf_Word *Buckets = P;
1382   Elf_Word *Chains = P + NumSymbols;
1383 
1384   for (const SymbolTableEntry &S : In<ELFT>::DynSymTab->getSymbols()) {
1385     SymbolBody *Body = S.Symbol;
1386     StringRef Name = Body->getName();
1387     unsigned I = Body->DynsymIndex;
1388     uint32_t Hash = hashSysV(Name) % NumSymbols;
1389     Chains[I] = Buckets[Hash];
1390     Buckets[Hash] = I;
1391   }
1392 }
1393 
1394 template <class ELFT>
1395 PltSection<ELFT>::PltSection()
1396     : SyntheticSection<ELFT>(SHF_ALLOC | SHF_EXECINSTR, SHT_PROGBITS, 16,
1397                              ".plt") {}
1398 
1399 template <class ELFT> void PltSection<ELFT>::writeTo(uint8_t *Buf) {
1400   // At beginning of PLT, we have code to call the dynamic linker
1401   // to resolve dynsyms at runtime. Write such code.
1402   Target->writePltHeader(Buf);
1403   size_t Off = Target->PltHeaderSize;
1404 
1405   for (auto &I : Entries) {
1406     const SymbolBody *B = I.first;
1407     unsigned RelOff = I.second;
1408     uint64_t Got = B->getGotPltVA<ELFT>();
1409     uint64_t Plt = this->getVA() + Off;
1410     Target->writePlt(Buf + Off, Got, Plt, B->PltIndex, RelOff);
1411     Off += Target->PltEntrySize;
1412   }
1413 }
1414 
1415 template <class ELFT> void PltSection<ELFT>::addEntry(SymbolBody &Sym) {
1416   Sym.PltIndex = Entries.size();
1417   unsigned RelOff = In<ELFT>::RelaPlt->getRelocOffset();
1418   Entries.push_back(std::make_pair(&Sym, RelOff));
1419 }
1420 
1421 template <class ELFT> size_t PltSection<ELFT>::getSize() const {
1422   return Target->PltHeaderSize + Entries.size() * Target->PltEntrySize;
1423 }
1424 
1425 template <class ELFT>
1426 IpltSection<ELFT>::IpltSection()
1427     : SyntheticSection<ELFT>(SHF_ALLOC | SHF_EXECINSTR, SHT_PROGBITS, 16,
1428                              ".plt") {}
1429 
1430 template <class ELFT> void IpltSection<ELFT>::writeTo(uint8_t *Buf) {
1431   // The IRelative relocations do not support lazy binding so no header is
1432   // needed
1433   size_t Off = 0;
1434   for (auto &I : Entries) {
1435     const SymbolBody *B = I.first;
1436     unsigned RelOff = I.second + In<ELFT>::Plt->getSize();
1437     uint64_t Got = B->getGotPltVA<ELFT>();
1438     uint64_t Plt = this->getVA() + Off;
1439     Target->writePlt(Buf + Off, Got, Plt, B->PltIndex, RelOff);
1440     Off += Target->PltEntrySize;
1441   }
1442 }
1443 
1444 template <class ELFT> void IpltSection<ELFT>::addEntry(SymbolBody &Sym) {
1445   Sym.PltIndex = Entries.size();
1446   Sym.IsInIplt = true;
1447   unsigned RelOff = In<ELFT>::RelaIplt->getRelocOffset();
1448   Entries.push_back(std::make_pair(&Sym, RelOff));
1449 }
1450 
1451 template <class ELFT> size_t IpltSection<ELFT>::getSize() const {
1452   return Entries.size() * Target->PltEntrySize;
1453 }
1454 
1455 template <class ELFT>
1456 GdbIndexSection<ELFT>::GdbIndexSection()
1457     : SyntheticSection<ELFT>(0, SHT_PROGBITS, 1, ".gdb_index"),
1458       StringPool(llvm::StringTableBuilder::ELF) {}
1459 
1460 template <class ELFT> void GdbIndexSection<ELFT>::parseDebugSections() {
1461   for (InputSectionBase<ELFT> *S : Symtab<ELFT>::X->Sections)
1462     if (InputSection<ELFT> *IS = dyn_cast<InputSection<ELFT>>(S))
1463       if (IS->OutSec && IS->Name == ".debug_info")
1464         readDwarf(IS);
1465 }
1466 
1467 // Iterative hash function for symbol's name is described in .gdb_index format
1468 // specification. Note that we use one for version 5 to 7 here, it is different
1469 // for version 4.
1470 static uint32_t hash(StringRef Str) {
1471   uint32_t R = 0;
1472   for (uint8_t C : Str)
1473     R = R * 67 + tolower(C) - 113;
1474   return R;
1475 }
1476 
1477 template <class ELFT>
1478 void GdbIndexSection<ELFT>::readDwarf(InputSection<ELFT> *I) {
1479   GdbIndexBuilder<ELFT> Builder(I);
1480   if (ErrorCount)
1481     return;
1482 
1483   size_t CuId = CompilationUnits.size();
1484   std::vector<std::pair<uintX_t, uintX_t>> CuList = Builder.readCUList();
1485   CompilationUnits.insert(CompilationUnits.end(), CuList.begin(), CuList.end());
1486 
1487   std::vector<AddressEntry<ELFT>> AddrArea = Builder.readAddressArea(CuId);
1488   AddressArea.insert(AddressArea.end(), AddrArea.begin(), AddrArea.end());
1489 
1490   std::vector<std::pair<StringRef, uint8_t>> NamesAndTypes =
1491       Builder.readPubNamesAndTypes();
1492 
1493   for (std::pair<StringRef, uint8_t> &Pair : NamesAndTypes) {
1494     uint32_t Hash = hash(Pair.first);
1495     size_t Offset = StringPool.add(Pair.first);
1496 
1497     bool IsNew;
1498     GdbSymbol *Sym;
1499     std::tie(IsNew, Sym) = SymbolTable.add(Hash, Offset);
1500     if (IsNew) {
1501       Sym->CuVectorIndex = CuVectors.size();
1502       CuVectors.push_back({{CuId, Pair.second}});
1503       continue;
1504     }
1505 
1506     std::vector<std::pair<uint32_t, uint8_t>> &CuVec =
1507         CuVectors[Sym->CuVectorIndex];
1508     CuVec.push_back({CuId, Pair.second});
1509   }
1510 }
1511 
1512 template <class ELFT> void GdbIndexSection<ELFT>::finalize() {
1513   if (Finalized)
1514     return;
1515   Finalized = true;
1516 
1517   parseDebugSections();
1518 
1519   // GdbIndex header consist from version fields
1520   // and 5 more fields with different kinds of offsets.
1521   CuTypesOffset = CuListOffset + CompilationUnits.size() * CompilationUnitSize;
1522   SymTabOffset = CuTypesOffset + AddressArea.size() * AddressEntrySize;
1523 
1524   ConstantPoolOffset =
1525       SymTabOffset + SymbolTable.getCapacity() * SymTabEntrySize;
1526 
1527   for (std::vector<std::pair<uint32_t, uint8_t>> &CuVec : CuVectors) {
1528     CuVectorsOffset.push_back(CuVectorsSize);
1529     CuVectorsSize += OffsetTypeSize * (CuVec.size() + 1);
1530   }
1531   StringPoolOffset = ConstantPoolOffset + CuVectorsSize;
1532 
1533   StringPool.finalizeInOrder();
1534 }
1535 
1536 template <class ELFT> size_t GdbIndexSection<ELFT>::getSize() const {
1537   const_cast<GdbIndexSection<ELFT> *>(this)->finalize();
1538   return StringPoolOffset + StringPool.getSize();
1539 }
1540 
1541 template <class ELFT> void GdbIndexSection<ELFT>::writeTo(uint8_t *Buf) {
1542   write32le(Buf, 7);                       // Write version.
1543   write32le(Buf + 4, CuListOffset);        // CU list offset.
1544   write32le(Buf + 8, CuTypesOffset);       // Types CU list offset.
1545   write32le(Buf + 12, CuTypesOffset);      // Address area offset.
1546   write32le(Buf + 16, SymTabOffset);       // Symbol table offset.
1547   write32le(Buf + 20, ConstantPoolOffset); // Constant pool offset.
1548   Buf += 24;
1549 
1550   // Write the CU list.
1551   for (std::pair<uintX_t, uintX_t> CU : CompilationUnits) {
1552     write64le(Buf, CU.first);
1553     write64le(Buf + 8, CU.second);
1554     Buf += 16;
1555   }
1556 
1557   // Write the address area.
1558   for (AddressEntry<ELFT> &E : AddressArea) {
1559     uintX_t BaseAddr = E.Section->OutSec->Addr + E.Section->getOffset(0);
1560     write64le(Buf, BaseAddr + E.LowAddress);
1561     write64le(Buf + 8, BaseAddr + E.HighAddress);
1562     write32le(Buf + 16, E.CuIndex);
1563     Buf += 20;
1564   }
1565 
1566   // Write the symbol table.
1567   for (size_t I = 0; I < SymbolTable.getCapacity(); ++I) {
1568     GdbSymbol *Sym = SymbolTable.getSymbol(I);
1569     if (Sym) {
1570       size_t NameOffset =
1571           Sym->NameOffset + StringPoolOffset - ConstantPoolOffset;
1572       size_t CuVectorOffset = CuVectorsOffset[Sym->CuVectorIndex];
1573       write32le(Buf, NameOffset);
1574       write32le(Buf + 4, CuVectorOffset);
1575     }
1576     Buf += 8;
1577   }
1578 
1579   // Write the CU vectors into the constant pool.
1580   for (std::vector<std::pair<uint32_t, uint8_t>> &CuVec : CuVectors) {
1581     write32le(Buf, CuVec.size());
1582     Buf += 4;
1583     for (std::pair<uint32_t, uint8_t> &P : CuVec) {
1584       uint32_t Index = P.first;
1585       uint8_t Flags = P.second;
1586       Index |= Flags << 24;
1587       write32le(Buf, Index);
1588       Buf += 4;
1589     }
1590   }
1591 
1592   StringPool.write(Buf);
1593 }
1594 
1595 template <class ELFT> bool GdbIndexSection<ELFT>::empty() const {
1596   return !Out<ELFT>::DebugInfo;
1597 }
1598 
1599 template <class ELFT>
1600 EhFrameHeader<ELFT>::EhFrameHeader()
1601     : SyntheticSection<ELFT>(SHF_ALLOC, SHT_PROGBITS, 1, ".eh_frame_hdr") {}
1602 
1603 // .eh_frame_hdr contains a binary search table of pointers to FDEs.
1604 // Each entry of the search table consists of two values,
1605 // the starting PC from where FDEs covers, and the FDE's address.
1606 // It is sorted by PC.
1607 template <class ELFT> void EhFrameHeader<ELFT>::writeTo(uint8_t *Buf) {
1608   const endianness E = ELFT::TargetEndianness;
1609 
1610   // Sort the FDE list by their PC and uniqueify. Usually there is only
1611   // one FDE for a PC (i.e. function), but if ICF merges two functions
1612   // into one, there can be more than one FDEs pointing to the address.
1613   auto Less = [](const FdeData &A, const FdeData &B) { return A.Pc < B.Pc; };
1614   std::stable_sort(Fdes.begin(), Fdes.end(), Less);
1615   auto Eq = [](const FdeData &A, const FdeData &B) { return A.Pc == B.Pc; };
1616   Fdes.erase(std::unique(Fdes.begin(), Fdes.end(), Eq), Fdes.end());
1617 
1618   Buf[0] = 1;
1619   Buf[1] = DW_EH_PE_pcrel | DW_EH_PE_sdata4;
1620   Buf[2] = DW_EH_PE_udata4;
1621   Buf[3] = DW_EH_PE_datarel | DW_EH_PE_sdata4;
1622   write32<E>(Buf + 4, Out<ELFT>::EhFrame->Addr - this->getVA() - 4);
1623   write32<E>(Buf + 8, Fdes.size());
1624   Buf += 12;
1625 
1626   uintX_t VA = this->getVA();
1627   for (FdeData &Fde : Fdes) {
1628     write32<E>(Buf, Fde.Pc - VA);
1629     write32<E>(Buf + 4, Fde.FdeVA - VA);
1630     Buf += 8;
1631   }
1632 }
1633 
1634 template <class ELFT> size_t EhFrameHeader<ELFT>::getSize() const {
1635   // .eh_frame_hdr has a 12 bytes header followed by an array of FDEs.
1636   return 12 + Out<ELFT>::EhFrame->NumFdes * 8;
1637 }
1638 
1639 template <class ELFT>
1640 void EhFrameHeader<ELFT>::addFde(uint32_t Pc, uint32_t FdeVA) {
1641   Fdes.push_back({Pc, FdeVA});
1642 }
1643 
1644 template <class ELFT> bool EhFrameHeader<ELFT>::empty() const {
1645   return Out<ELFT>::EhFrame->empty();
1646 }
1647 
1648 template <class ELFT>
1649 VersionDefinitionSection<ELFT>::VersionDefinitionSection()
1650     : SyntheticSection<ELFT>(SHF_ALLOC, SHT_GNU_verdef, sizeof(uint32_t),
1651                              ".gnu.version_d") {}
1652 
1653 static StringRef getFileDefName() {
1654   if (!Config->SoName.empty())
1655     return Config->SoName;
1656   return Config->OutputFile;
1657 }
1658 
1659 template <class ELFT> void VersionDefinitionSection<ELFT>::finalize() {
1660   FileDefNameOff = In<ELFT>::DynStrTab->addString(getFileDefName());
1661   for (VersionDefinition &V : Config->VersionDefinitions)
1662     V.NameOff = In<ELFT>::DynStrTab->addString(V.Name);
1663 
1664   this->OutSec->Link = this->Link = In<ELFT>::DynStrTab->OutSec->SectionIndex;
1665 
1666   // sh_info should be set to the number of definitions. This fact is missed in
1667   // documentation, but confirmed by binutils community:
1668   // https://sourceware.org/ml/binutils/2014-11/msg00355.html
1669   this->OutSec->Info = this->Info = getVerDefNum();
1670 }
1671 
1672 template <class ELFT>
1673 void VersionDefinitionSection<ELFT>::writeOne(uint8_t *Buf, uint32_t Index,
1674                                               StringRef Name, size_t NameOff) {
1675   auto *Verdef = reinterpret_cast<Elf_Verdef *>(Buf);
1676   Verdef->vd_version = 1;
1677   Verdef->vd_cnt = 1;
1678   Verdef->vd_aux = sizeof(Elf_Verdef);
1679   Verdef->vd_next = sizeof(Elf_Verdef) + sizeof(Elf_Verdaux);
1680   Verdef->vd_flags = (Index == 1 ? VER_FLG_BASE : 0);
1681   Verdef->vd_ndx = Index;
1682   Verdef->vd_hash = hashSysV(Name);
1683 
1684   auto *Verdaux = reinterpret_cast<Elf_Verdaux *>(Buf + sizeof(Elf_Verdef));
1685   Verdaux->vda_name = NameOff;
1686   Verdaux->vda_next = 0;
1687 }
1688 
1689 template <class ELFT>
1690 void VersionDefinitionSection<ELFT>::writeTo(uint8_t *Buf) {
1691   writeOne(Buf, 1, getFileDefName(), FileDefNameOff);
1692 
1693   for (VersionDefinition &V : Config->VersionDefinitions) {
1694     Buf += sizeof(Elf_Verdef) + sizeof(Elf_Verdaux);
1695     writeOne(Buf, V.Id, V.Name, V.NameOff);
1696   }
1697 
1698   // Need to terminate the last version definition.
1699   Elf_Verdef *Verdef = reinterpret_cast<Elf_Verdef *>(Buf);
1700   Verdef->vd_next = 0;
1701 }
1702 
1703 template <class ELFT> size_t VersionDefinitionSection<ELFT>::getSize() const {
1704   return (sizeof(Elf_Verdef) + sizeof(Elf_Verdaux)) * getVerDefNum();
1705 }
1706 
1707 template <class ELFT>
1708 VersionTableSection<ELFT>::VersionTableSection()
1709     : SyntheticSection<ELFT>(SHF_ALLOC, SHT_GNU_versym, sizeof(uint16_t),
1710                              ".gnu.version") {}
1711 
1712 template <class ELFT> void VersionTableSection<ELFT>::finalize() {
1713   this->OutSec->Entsize = this->Entsize = sizeof(Elf_Versym);
1714   // At the moment of june 2016 GNU docs does not mention that sh_link field
1715   // should be set, but Sun docs do. Also readelf relies on this field.
1716   this->OutSec->Link = this->Link = In<ELFT>::DynSymTab->OutSec->SectionIndex;
1717 }
1718 
1719 template <class ELFT> size_t VersionTableSection<ELFT>::getSize() const {
1720   return sizeof(Elf_Versym) * (In<ELFT>::DynSymTab->getSymbols().size() + 1);
1721 }
1722 
1723 template <class ELFT> void VersionTableSection<ELFT>::writeTo(uint8_t *Buf) {
1724   auto *OutVersym = reinterpret_cast<Elf_Versym *>(Buf) + 1;
1725   for (const SymbolTableEntry &S : In<ELFT>::DynSymTab->getSymbols()) {
1726     OutVersym->vs_index = S.Symbol->symbol()->VersionId;
1727     ++OutVersym;
1728   }
1729 }
1730 
1731 template <class ELFT> bool VersionTableSection<ELFT>::empty() const {
1732   return !In<ELFT>::VerDef && In<ELFT>::VerNeed->empty();
1733 }
1734 
1735 template <class ELFT>
1736 VersionNeedSection<ELFT>::VersionNeedSection()
1737     : SyntheticSection<ELFT>(SHF_ALLOC, SHT_GNU_verneed, sizeof(uint32_t),
1738                              ".gnu.version_r") {
1739   // Identifiers in verneed section start at 2 because 0 and 1 are reserved
1740   // for VER_NDX_LOCAL and VER_NDX_GLOBAL.
1741   // First identifiers are reserved by verdef section if it exist.
1742   NextIndex = getVerDefNum() + 1;
1743 }
1744 
1745 template <class ELFT>
1746 void VersionNeedSection<ELFT>::addSymbol(SharedSymbol<ELFT> *SS) {
1747   if (!SS->Verdef) {
1748     SS->symbol()->VersionId = VER_NDX_GLOBAL;
1749     return;
1750   }
1751   SharedFile<ELFT> *F = SS->file();
1752   // If we don't already know that we need an Elf_Verneed for this DSO, prepare
1753   // to create one by adding it to our needed list and creating a dynstr entry
1754   // for the soname.
1755   if (F->VerdefMap.empty())
1756     Needed.push_back({F, In<ELFT>::DynStrTab->addString(F->getSoName())});
1757   typename SharedFile<ELFT>::NeededVer &NV = F->VerdefMap[SS->Verdef];
1758   // If we don't already know that we need an Elf_Vernaux for this Elf_Verdef,
1759   // prepare to create one by allocating a version identifier and creating a
1760   // dynstr entry for the version name.
1761   if (NV.Index == 0) {
1762     NV.StrTab = In<ELFT>::DynStrTab->addString(
1763         SS->file()->getStringTable().data() + SS->Verdef->getAux()->vda_name);
1764     NV.Index = NextIndex++;
1765   }
1766   SS->symbol()->VersionId = NV.Index;
1767 }
1768 
1769 template <class ELFT> void VersionNeedSection<ELFT>::writeTo(uint8_t *Buf) {
1770   // The Elf_Verneeds need to appear first, followed by the Elf_Vernauxs.
1771   auto *Verneed = reinterpret_cast<Elf_Verneed *>(Buf);
1772   auto *Vernaux = reinterpret_cast<Elf_Vernaux *>(Verneed + Needed.size());
1773 
1774   for (std::pair<SharedFile<ELFT> *, size_t> &P : Needed) {
1775     // Create an Elf_Verneed for this DSO.
1776     Verneed->vn_version = 1;
1777     Verneed->vn_cnt = P.first->VerdefMap.size();
1778     Verneed->vn_file = P.second;
1779     Verneed->vn_aux =
1780         reinterpret_cast<char *>(Vernaux) - reinterpret_cast<char *>(Verneed);
1781     Verneed->vn_next = sizeof(Elf_Verneed);
1782     ++Verneed;
1783 
1784     // Create the Elf_Vernauxs for this Elf_Verneed. The loop iterates over
1785     // VerdefMap, which will only contain references to needed version
1786     // definitions. Each Elf_Vernaux is based on the information contained in
1787     // the Elf_Verdef in the source DSO. This loop iterates over a std::map of
1788     // pointers, but is deterministic because the pointers refer to Elf_Verdef
1789     // data structures within a single input file.
1790     for (auto &NV : P.first->VerdefMap) {
1791       Vernaux->vna_hash = NV.first->vd_hash;
1792       Vernaux->vna_flags = 0;
1793       Vernaux->vna_other = NV.second.Index;
1794       Vernaux->vna_name = NV.second.StrTab;
1795       Vernaux->vna_next = sizeof(Elf_Vernaux);
1796       ++Vernaux;
1797     }
1798 
1799     Vernaux[-1].vna_next = 0;
1800   }
1801   Verneed[-1].vn_next = 0;
1802 }
1803 
1804 template <class ELFT> void VersionNeedSection<ELFT>::finalize() {
1805   this->OutSec->Link = this->Link = In<ELFT>::DynStrTab->OutSec->SectionIndex;
1806   this->OutSec->Info = this->Info = Needed.size();
1807 }
1808 
1809 template <class ELFT> size_t VersionNeedSection<ELFT>::getSize() const {
1810   unsigned Size = Needed.size() * sizeof(Elf_Verneed);
1811   for (const std::pair<SharedFile<ELFT> *, size_t> &P : Needed)
1812     Size += P.first->VerdefMap.size() * sizeof(Elf_Vernaux);
1813   return Size;
1814 }
1815 
1816 template <class ELFT> bool VersionNeedSection<ELFT>::empty() const {
1817   return getNeedNum() == 0;
1818 }
1819 
1820 template <class ELFT>
1821 MipsRldMapSection<ELFT>::MipsRldMapSection()
1822     : SyntheticSection<ELFT>(SHF_ALLOC | SHF_WRITE, SHT_PROGBITS,
1823                              sizeof(typename ELFT::uint), ".rld_map") {}
1824 
1825 template <class ELFT> void MipsRldMapSection<ELFT>::writeTo(uint8_t *Buf) {
1826   // Apply filler from linker script.
1827   uint64_t Filler = Script<ELFT>::X->getFiller(this->Name);
1828   Filler = (Filler << 32) | Filler;
1829   memcpy(Buf, &Filler, getSize());
1830 }
1831 
1832 template <class ELFT>
1833 ARMExidxSentinelSection<ELFT>::ARMExidxSentinelSection()
1834     : SyntheticSection<ELFT>(SHF_ALLOC | SHF_LINK_ORDER, SHT_ARM_EXIDX,
1835                              sizeof(typename ELFT::uint), ".ARM.exidx") {}
1836 
1837 // Write a terminating sentinel entry to the end of the .ARM.exidx table.
1838 // This section will have been sorted last in the .ARM.exidx table.
1839 // This table entry will have the form:
1840 // | PREL31 upper bound of code that has exception tables | EXIDX_CANTUNWIND |
1841 template <class ELFT>
1842 void ARMExidxSentinelSection<ELFT>::writeTo(uint8_t *Buf) {
1843   // Get the InputSection before us, we are by definition last
1844   auto RI = cast<OutputSection<ELFT>>(this->OutSec)->Sections.rbegin();
1845   InputSection<ELFT> *LE = *(++RI);
1846   InputSection<ELFT> *LC = cast<InputSection<ELFT>>(LE->getLinkOrderDep());
1847   uint64_t S = LC->OutSec->Addr + LC->getOffset(LC->getSize());
1848   uint64_t P = this->getVA();
1849   Target->relocateOne(Buf, R_ARM_PREL31, S - P);
1850   write32le(Buf + 4, 0x1);
1851 }
1852 
1853 template InputSection<ELF32LE> *elf::createCommonSection();
1854 template InputSection<ELF32BE> *elf::createCommonSection();
1855 template InputSection<ELF64LE> *elf::createCommonSection();
1856 template InputSection<ELF64BE> *elf::createCommonSection();
1857 
1858 template InputSection<ELF32LE> *elf::createInterpSection();
1859 template InputSection<ELF32BE> *elf::createInterpSection();
1860 template InputSection<ELF64LE> *elf::createInterpSection();
1861 template InputSection<ELF64BE> *elf::createInterpSection();
1862 
1863 template MergeInputSection<ELF32LE> *elf::createCommentSection();
1864 template MergeInputSection<ELF32BE> *elf::createCommentSection();
1865 template MergeInputSection<ELF64LE> *elf::createCommentSection();
1866 template MergeInputSection<ELF64BE> *elf::createCommentSection();
1867 
1868 template class elf::MipsAbiFlagsSection<ELF32LE>;
1869 template class elf::MipsAbiFlagsSection<ELF32BE>;
1870 template class elf::MipsAbiFlagsSection<ELF64LE>;
1871 template class elf::MipsAbiFlagsSection<ELF64BE>;
1872 
1873 template class elf::MipsOptionsSection<ELF32LE>;
1874 template class elf::MipsOptionsSection<ELF32BE>;
1875 template class elf::MipsOptionsSection<ELF64LE>;
1876 template class elf::MipsOptionsSection<ELF64BE>;
1877 
1878 template class elf::MipsReginfoSection<ELF32LE>;
1879 template class elf::MipsReginfoSection<ELF32BE>;
1880 template class elf::MipsReginfoSection<ELF64LE>;
1881 template class elf::MipsReginfoSection<ELF64BE>;
1882 
1883 template class elf::BuildIdSection<ELF32LE>;
1884 template class elf::BuildIdSection<ELF32BE>;
1885 template class elf::BuildIdSection<ELF64LE>;
1886 template class elf::BuildIdSection<ELF64BE>;
1887 
1888 template class elf::GotSection<ELF32LE>;
1889 template class elf::GotSection<ELF32BE>;
1890 template class elf::GotSection<ELF64LE>;
1891 template class elf::GotSection<ELF64BE>;
1892 
1893 template class elf::MipsGotSection<ELF32LE>;
1894 template class elf::MipsGotSection<ELF32BE>;
1895 template class elf::MipsGotSection<ELF64LE>;
1896 template class elf::MipsGotSection<ELF64BE>;
1897 
1898 template class elf::GotPltSection<ELF32LE>;
1899 template class elf::GotPltSection<ELF32BE>;
1900 template class elf::GotPltSection<ELF64LE>;
1901 template class elf::GotPltSection<ELF64BE>;
1902 
1903 template class elf::IgotPltSection<ELF32LE>;
1904 template class elf::IgotPltSection<ELF32BE>;
1905 template class elf::IgotPltSection<ELF64LE>;
1906 template class elf::IgotPltSection<ELF64BE>;
1907 
1908 template class elf::StringTableSection<ELF32LE>;
1909 template class elf::StringTableSection<ELF32BE>;
1910 template class elf::StringTableSection<ELF64LE>;
1911 template class elf::StringTableSection<ELF64BE>;
1912 
1913 template class elf::DynamicSection<ELF32LE>;
1914 template class elf::DynamicSection<ELF32BE>;
1915 template class elf::DynamicSection<ELF64LE>;
1916 template class elf::DynamicSection<ELF64BE>;
1917 
1918 template class elf::RelocationSection<ELF32LE>;
1919 template class elf::RelocationSection<ELF32BE>;
1920 template class elf::RelocationSection<ELF64LE>;
1921 template class elf::RelocationSection<ELF64BE>;
1922 
1923 template class elf::SymbolTableSection<ELF32LE>;
1924 template class elf::SymbolTableSection<ELF32BE>;
1925 template class elf::SymbolTableSection<ELF64LE>;
1926 template class elf::SymbolTableSection<ELF64BE>;
1927 
1928 template class elf::GnuHashTableSection<ELF32LE>;
1929 template class elf::GnuHashTableSection<ELF32BE>;
1930 template class elf::GnuHashTableSection<ELF64LE>;
1931 template class elf::GnuHashTableSection<ELF64BE>;
1932 
1933 template class elf::HashTableSection<ELF32LE>;
1934 template class elf::HashTableSection<ELF32BE>;
1935 template class elf::HashTableSection<ELF64LE>;
1936 template class elf::HashTableSection<ELF64BE>;
1937 
1938 template class elf::PltSection<ELF32LE>;
1939 template class elf::PltSection<ELF32BE>;
1940 template class elf::PltSection<ELF64LE>;
1941 template class elf::PltSection<ELF64BE>;
1942 
1943 template class elf::IpltSection<ELF32LE>;
1944 template class elf::IpltSection<ELF32BE>;
1945 template class elf::IpltSection<ELF64LE>;
1946 template class elf::IpltSection<ELF64BE>;
1947 
1948 template class elf::GdbIndexSection<ELF32LE>;
1949 template class elf::GdbIndexSection<ELF32BE>;
1950 template class elf::GdbIndexSection<ELF64LE>;
1951 template class elf::GdbIndexSection<ELF64BE>;
1952 
1953 template class elf::EhFrameHeader<ELF32LE>;
1954 template class elf::EhFrameHeader<ELF32BE>;
1955 template class elf::EhFrameHeader<ELF64LE>;
1956 template class elf::EhFrameHeader<ELF64BE>;
1957 
1958 template class elf::VersionTableSection<ELF32LE>;
1959 template class elf::VersionTableSection<ELF32BE>;
1960 template class elf::VersionTableSection<ELF64LE>;
1961 template class elf::VersionTableSection<ELF64BE>;
1962 
1963 template class elf::VersionNeedSection<ELF32LE>;
1964 template class elf::VersionNeedSection<ELF32BE>;
1965 template class elf::VersionNeedSection<ELF64LE>;
1966 template class elf::VersionNeedSection<ELF64BE>;
1967 
1968 template class elf::VersionDefinitionSection<ELF32LE>;
1969 template class elf::VersionDefinitionSection<ELF32BE>;
1970 template class elf::VersionDefinitionSection<ELF64LE>;
1971 template class elf::VersionDefinitionSection<ELF64BE>;
1972 
1973 template class elf::MipsRldMapSection<ELF32LE>;
1974 template class elf::MipsRldMapSection<ELF32BE>;
1975 template class elf::MipsRldMapSection<ELF64LE>;
1976 template class elf::MipsRldMapSection<ELF64BE>;
1977 
1978 template class elf::ARMExidxSentinelSection<ELF32LE>;
1979 template class elf::ARMExidxSentinelSection<ELF32BE>;
1980 template class elf::ARMExidxSentinelSection<ELF64LE>;
1981 template class elf::ARMExidxSentinelSection<ELF64BE>;
1982