tools/yaml2obj/yaml2elf.cpp

   1 //===- yaml2elf - Convert YAML to a ELF object file -----------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 ///
   9 /// \file
  10 /// The ELF component of yaml2obj.
  11 ///
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "yaml2obj.h"
  15 #include "llvm/ADT/ArrayRef.h"
  16 #include "llvm/BinaryFormat/ELF.h"
  17 #include "llvm/MC/StringTableBuilder.h"
  18 #include "llvm/Object/ELFObjectFile.h"
  19 #include "llvm/ObjectYAML/ELFYAML.h"
  20 #include "llvm/Support/EndianStream.h"
  21 #include "llvm/Support/MemoryBuffer.h"
  22 #include "llvm/Support/WithColor.h"
  23 #include "llvm/Support/YAMLTraits.h"
  24 #include "llvm/Support/raw_ostream.h"
  25
  26 using namespace llvm;
  27
  28 // This class is used to build up a contiguous binary blob while keeping
  29 // track of an offset in the output (which notionally begins at
  30 // `InitialOffset`).
  31 namespace {
  32 class ContiguousBlobAccumulator {
  33   const uint64_t InitialOffset;
  34   SmallVector<char, 128> Buf;
  35   raw_svector_ostream OS;
  36
  37   /// \returns The new offset.
  38   uint64_t padToAlignment(unsigned Align) {
  39     if (Align == 0)
  40       Align = 1;
  41     uint64_t CurrentOffset = InitialOffset + OS.tell();
  42     uint64_t AlignedOffset = alignTo(CurrentOffset, Align);
  43     OS.write_zeros(AlignedOffset - CurrentOffset);
  44     return AlignedOffset; // == CurrentOffset;
  45   }
  46
  47 public:
  48   ContiguousBlobAccumulator(uint64_t InitialOffset_)
  49       : InitialOffset(InitialOffset_), Buf(), OS(Buf) {}
  50   template <class Integer>
  51   raw_ostream &getOSAndAlignedOffset(Integer &Offset, unsigned Align) {
  52     Offset = padToAlignment(Align);
  53     return OS;
  54   }
  55   void writeBlobToStream(raw_ostream &Out) { Out << OS.str(); }
  56 };
  57 } // end anonymous namespace
  58
  59 // Used to keep track of section and symbol names, so that in the YAML file
  60 // sections and symbols can be referenced by name instead of by index.
  61 namespace {
  62 class NameToIdxMap {
  63   StringMap<int> Map;
  64 public:
  65   /// \returns true if name is already present in the map.
  66   bool addName(StringRef Name, unsigned i) {
  67     return !Map.insert(std::make_pair(Name, (int)i)).second;
  68   }
  69   /// \returns true if name is not present in the map
  70   bool lookup(StringRef Name, unsigned &Idx) const {
  71     StringMap<int>::const_iterator I = Map.find(Name);
  72     if (I == Map.end())
  73       return true;
  74     Idx = I->getValue();
  75     return false;
  76   }
  77   /// asserts if name is not present in the map
  78   unsigned get(StringRef Name) const {
  79     unsigned Idx = 0;
  80     auto missing = lookup(Name, Idx);
  81     (void)missing;
  82     assert(!missing && "Expected section not found in index");
  83     return Idx;
  84   }
  85   unsigned size() const { return Map.size(); }
  86 };
  87 } // end anonymous namespace
  88
  89 template <class T>
  90 static size_t arrayDataSize(ArrayRef<T> A) {
  91   return A.size() * sizeof(T);
  92 }
  93
  94 template <class T>
  95 static void writeArrayData(raw_ostream &OS, ArrayRef<T> A) {
  96   OS.write((const char *)A.data(), arrayDataSize(A));
  97 }
  98
  99 template <class T>
 100 static void zero(T &Obj) {
 101   memset(&Obj, 0, sizeof(Obj));
 102 }
 103
 104 namespace {
 105 /// "Single point of truth" for the ELF file construction.
 106 /// TODO: This class still has a ways to go before it is truly a "single
 107 /// point of truth".
 108 template <class ELFT>
 109 class ELFState {
 110   typedef typename ELFT::Ehdr Elf_Ehdr;
 111   typedef typename ELFT::Phdr Elf_Phdr;
 112   typedef typename ELFT::Shdr Elf_Shdr;
 113   typedef typename ELFT::Sym Elf_Sym;
 114   typedef typename ELFT::Rel Elf_Rel;
 115   typedef typename ELFT::Rela Elf_Rela;
 116   typedef typename ELFT::Relr Elf_Relr;
 117   typedef typename ELFT::Dyn Elf_Dyn;
 118
 119   enum class SymtabType { Static, Dynamic };
 120
 121   /// The future ".strtab" section.
 122   StringTableBuilder DotStrtab{StringTableBuilder::ELF};
 123
 124   /// The future ".shstrtab" section.
 125   StringTableBuilder DotShStrtab{StringTableBuilder::ELF};
 126
 127   /// The future ".dynstr" section.
 128   StringTableBuilder DotDynstr{StringTableBuilder::ELF};
 129
 130   NameToIdxMap SN2I;
 131   NameToIdxMap SymN2I;
 132   const ELFYAML::Object &Doc;
 133
 134   bool buildSectionIndex();
 135   bool buildSymbolIndex(ArrayRef<ELFYAML::Symbol> Symbols);
 136   void initELFHeader(Elf_Ehdr &Header);
 137   void initProgramHeaders(std::vector<Elf_Phdr> &PHeaders);
 138   bool initSectionHeaders(std::vector<Elf_Shdr> &SHeaders,
 139                           ContiguousBlobAccumulator &CBA);
 140   void initSymtabSectionHeader(Elf_Shdr &SHeader, SymtabType STType,
 141                                ContiguousBlobAccumulator &CBA);
 142   void initStrtabSectionHeader(Elf_Shdr &SHeader, StringRef Name,
 143                                StringTableBuilder &STB,
 144                                ContiguousBlobAccumulator &CBA);
 145   void setProgramHeaderLayout(std::vector<Elf_Phdr> &PHeaders,
 146                               std::vector<Elf_Shdr> &SHeaders);
 147   void addSymbols(ArrayRef<ELFYAML::Symbol> Symbols, std::vector<Elf_Sym> &Syms,
 148                   const StringTableBuilder &Strtab);
 149   bool writeSectionContent(Elf_Shdr &SHeader,
 150                            const ELFYAML::RawContentSection &Section,
 151                            ContiguousBlobAccumulator &CBA);
 152   bool writeSectionContent(Elf_Shdr &SHeader,
 153                            const ELFYAML::RelocationSection &Section,
 154                            ContiguousBlobAccumulator &CBA);
 155   bool writeSectionContent(Elf_Shdr &SHeader, const ELFYAML::Group &Group,
 156                            ContiguousBlobAccumulator &CBA);
 157   bool writeSectionContent(Elf_Shdr &SHeader,
 158                            const ELFYAML::SymverSection &Section,
 159                            ContiguousBlobAccumulator &CBA);
 160   bool writeSectionContent(Elf_Shdr &SHeader,
 161                            const ELFYAML::VerneedSection &Section,
 162                            ContiguousBlobAccumulator &CBA);
 163   bool writeSectionContent(Elf_Shdr &SHeader,
 164                            const ELFYAML::VerdefSection &Section,
 165                            ContiguousBlobAccumulator &CBA);
 166   bool writeSectionContent(Elf_Shdr &SHeader,
 167                            const ELFYAML::MipsABIFlags &Section,
 168                            ContiguousBlobAccumulator &CBA);
 169   bool writeSectionContent(Elf_Shdr &SHeader,
 170                            const ELFYAML::DynamicSection &Section,
 171                            ContiguousBlobAccumulator &CBA);
 172   std::vector<StringRef> implicitSectionNames() const;
 173
 174   // - SHT_NULL entry (placed first, i.e. 0'th entry)
 175   // - symbol table (.symtab) (defaults to after last yaml section)
 176   // - string table (.strtab) (defaults to after .symtab)
 177   // - section header string table (.shstrtab) (defaults to after .strtab)
 178   // - dynamic symbol table (.dynsym) (defaults to after .shstrtab)
 179   // - dynamic string table (.dynstr) (defaults to after .dynsym)
 180   unsigned getDotSymTabSecNo() const { return SN2I.get(".symtab"); }
 181   unsigned getDotStrTabSecNo() const { return SN2I.get(".strtab"); }
 182   unsigned getDotShStrTabSecNo() const { return SN2I.get(".shstrtab"); }
 183   unsigned getDotDynSymSecNo() const { return SN2I.get(".dynsym"); }
 184   unsigned getDotDynStrSecNo() const { return SN2I.get(".dynstr"); }
 185   unsigned getSectionCount() const { return SN2I.size() + 1; }
 186
 187   ELFState(const ELFYAML::Object &D) : Doc(D) {}
 188
 189 public:
 190   static int writeELF(raw_ostream &OS, const ELFYAML::Object &Doc);
 191
 192 private:
 193   void finalizeStrings();
 194 };
 195 } // end anonymous namespace
 196
 197 template <class ELFT>
 198 void ELFState<ELFT>::initELFHeader(Elf_Ehdr &Header) {
 199   using namespace llvm::ELF;
 200   zero(Header);
 201   Header.e_ident[EI_MAG0] = 0x7f;
 202   Header.e_ident[EI_MAG1] = 'E';
 203   Header.e_ident[EI_MAG2] = 'L';
 204   Header.e_ident[EI_MAG3] = 'F';
 205   Header.e_ident[EI_CLASS] = ELFT::Is64Bits ? ELFCLASS64 : ELFCLASS32;
 206   Header.e_ident[EI_DATA] = Doc.Header.Data;
 207   Header.e_ident[EI_VERSION] = EV_CURRENT;
 208   Header.e_ident[EI_OSABI] = Doc.Header.OSABI;
 209   Header.e_ident[EI_ABIVERSION] = Doc.Header.ABIVersion;
 210   Header.e_type = Doc.Header.Type;
 211   Header.e_machine = Doc.Header.Machine;
 212   Header.e_version = EV_CURRENT;
 213   Header.e_entry = Doc.Header.Entry;
 214   Header.e_phoff = sizeof(Header);
 215   Header.e_flags = Doc.Header.Flags;
 216   Header.e_ehsize = sizeof(Elf_Ehdr);
 217   Header.e_phentsize = sizeof(Elf_Phdr);
 218   Header.e_phnum = Doc.ProgramHeaders.size();
 219   Header.e_shentsize = sizeof(Elf_Shdr);
 220   // Immediately following the ELF header and program headers.
 221   Header.e_shoff =
 222       sizeof(Header) + sizeof(Elf_Phdr) * Doc.ProgramHeaders.size();
 223   Header.e_shnum = getSectionCount();
 224   Header.e_shstrndx = getDotShStrTabSecNo();
 225 }
 226
 227 template <class ELFT>
 228 void ELFState<ELFT>::initProgramHeaders(std::vector<Elf_Phdr> &PHeaders) {
 229   for (const auto &YamlPhdr : Doc.ProgramHeaders) {
 230     Elf_Phdr Phdr;
 231     Phdr.p_type = YamlPhdr.Type;
 232     Phdr.p_flags = YamlPhdr.Flags;
 233     Phdr.p_vaddr = YamlPhdr.VAddr;
 234     Phdr.p_paddr = YamlPhdr.PAddr;
 235     PHeaders.push_back(Phdr);
 236   }
 237 }
 238
 239 static bool convertSectionIndex(NameToIdxMap &SN2I, StringRef SecName,
 240                                 StringRef IndexSrc, unsigned &IndexDest) {
 241   if (SN2I.lookup(IndexSrc, IndexDest) && !to_integer(IndexSrc, IndexDest)) {
 242     WithColor::error() << "Unknown section referenced: '" << IndexSrc
 243                        << "' at YAML section '" << SecName << "'.\n";
 244     return false;
 245   }
 246   return true;
 247 }
 248
 249 template <class ELFT>
 250 bool ELFState<ELFT>::initSectionHeaders(std::vector<Elf_Shdr> &SHeaders,
 251                                         ContiguousBlobAccumulator &CBA) {
 252   // Ensure SHN_UNDEF entry is present. An all-zero section header is a
 253   // valid SHN_UNDEF entry since SHT_NULL == 0.
 254   Elf_Shdr SHeader;
 255   zero(SHeader);
 256   SHeaders.push_back(SHeader);
 257
 258   for (const auto &Sec : Doc.Sections) {
 259     zero(SHeader);
 260     SHeader.sh_name = DotShStrtab.getOffset(Sec->Name);
 261     SHeader.sh_type = Sec->Type;
 262     SHeader.sh_flags = Sec->Flags;
 263     SHeader.sh_addr = Sec->Address;
 264     SHeader.sh_addralign = Sec->AddressAlign;
 265
 266     if (!Sec->Link.empty()) {
 267       unsigned Index;
 268       if (!convertSectionIndex(SN2I, Sec->Name, Sec->Link, Index))
 269         return false;
 270       SHeader.sh_link = Index;
 271     }
 272
 273     if (auto S = dyn_cast<ELFYAML::RawContentSection>(Sec.get())) {
 274       if (!writeSectionContent(SHeader, *S, CBA))
 275         return false;
 276     } else if (auto S = dyn_cast<ELFYAML::RelocationSection>(Sec.get())) {
 277       if (!writeSectionContent(SHeader, *S, CBA))
 278         return false;
 279     } else if (auto S = dyn_cast<ELFYAML::Group>(Sec.get())) {
 280       if (!writeSectionContent(SHeader, *S, CBA))
 281         return false;
 282     } else if (auto S = dyn_cast<ELFYAML::MipsABIFlags>(Sec.get())) {
 283       if (!writeSectionContent(SHeader, *S, CBA))
 284         return false;
 285     } else if (auto S = dyn_cast<ELFYAML::NoBitsSection>(Sec.get())) {
 286       SHeader.sh_entsize = 0;
 287       SHeader.sh_size = S->Size;
 288       // SHT_NOBITS section does not have content
 289       // so just to setup the section offset.
 290       CBA.getOSAndAlignedOffset(SHeader.sh_offset, SHeader.sh_addralign);
 291     } else if (auto S = dyn_cast<ELFYAML::DynamicSection>(Sec.get())) {
 292       if (!writeSectionContent(SHeader, *S, CBA))
 293         return false;
 294     } else if (auto S = dyn_cast<ELFYAML::SymverSection>(Sec.get())) {
 295       if (!writeSectionContent(SHeader, *S, CBA))
 296         return false;
 297     } else if (auto S = dyn_cast<ELFYAML::VerneedSection>(Sec.get())) {
 298       if (!writeSectionContent(SHeader, *S, CBA))
 299         return false;
 300     } else if (auto S = dyn_cast<ELFYAML::VerdefSection>(Sec.get())) {
 301       if (!writeSectionContent(SHeader, *S, CBA))
 302         return false;
 303     } else
 304       llvm_unreachable("Unknown section type");
 305
 306     SHeaders.push_back(SHeader);
 307   }
 308   return true;
 309 }
 310
 311 static size_t findFirstNonGlobal(ArrayRef<ELFYAML::Symbol> Symbols) {
 312   for (size_t I = 0; I < Symbols.size(); ++I)
 313     if (Symbols[I].Binding.value != ELF::STB_LOCAL)
 314       return I;
 315   return Symbols.size();
 316 }
 317
 318 template <class ELFT>
 319 void ELFState<ELFT>::initSymtabSectionHeader(Elf_Shdr &SHeader,
 320                                              SymtabType STType,
 321                                              ContiguousBlobAccumulator &CBA) {
 322   zero(SHeader);
 323   bool IsStatic = STType == SymtabType::Static;
 324   SHeader.sh_name = DotShStrtab.getOffset(IsStatic ? ".symtab" : ".dynsym");
 325   SHeader.sh_type = IsStatic ? ELF::SHT_SYMTAB : ELF::SHT_DYNSYM;
 326   SHeader.sh_link = IsStatic ? getDotStrTabSecNo() : getDotDynStrSecNo();
 327   if (!IsStatic)
 328     SHeader.sh_flags |= ELF::SHF_ALLOC;
 329
 330   // One greater than symbol table index of the last local symbol.
 331   const auto &Symbols = IsStatic ? Doc.Symbols : Doc.DynamicSymbols;
 332   SHeader.sh_info = findFirstNonGlobal(Symbols) + 1;
 333   SHeader.sh_entsize = sizeof(Elf_Sym);
 334   SHeader.sh_addralign = 8;
 335
 336   // Get the section index ignoring the SHT_NULL section.
 337   unsigned SecNdx =
 338       IsStatic ? getDotSymTabSecNo() - 1 : getDotDynSymSecNo() - 1;
 339   // If the symbol table section is explicitly described in the YAML
 340   // then we should set the fields requested.
 341   if (SecNdx < Doc.Sections.size()) {
 342     ELFYAML::Section *Sec = Doc.Sections[SecNdx].get();
 343     SHeader.sh_addr = Sec->Address;
 344     if (auto S = dyn_cast<ELFYAML::RawContentSection>(Sec))
 345       SHeader.sh_info = S->Info;
 346   }
 347
 348   std::vector<Elf_Sym> Syms;
 349   {
 350     // Ensure STN_UNDEF is present
 351     Elf_Sym Sym;
 352     zero(Sym);
 353     Syms.push_back(Sym);
 354   }
 355
 356   addSymbols(Symbols, Syms, IsStatic ? DotStrtab : DotDynstr);
 357
 358   writeArrayData(
 359       CBA.getOSAndAlignedOffset(SHeader.sh_offset, SHeader.sh_addralign),
 360       makeArrayRef(Syms));
 361   SHeader.sh_size = arrayDataSize(makeArrayRef(Syms));
 362 }
 363
 364 template <class ELFT>
 365 void ELFState<ELFT>::initStrtabSectionHeader(Elf_Shdr &SHeader, StringRef Name,
 366                                              StringTableBuilder &STB,
 367                                              ContiguousBlobAccumulator &CBA) {
 368   zero(SHeader);
 369   SHeader.sh_name = DotShStrtab.getOffset(Name);
 370   SHeader.sh_type = ELF::SHT_STRTAB;
 371   STB.write(CBA.getOSAndAlignedOffset(SHeader.sh_offset, SHeader.sh_addralign));
 372   SHeader.sh_size = STB.getSize();
 373   SHeader.sh_addralign = 1;
 374
 375   // If .dynstr section is explicitly described in the YAML
 376   // then we want to use its section address.
 377   if (Name == ".dynstr") {
 378     // Take section index and ignore the SHT_NULL section.
 379     unsigned SecNdx = getDotDynStrSecNo() - 1;
 380     if (SecNdx < Doc.Sections.size())
 381       SHeader.sh_addr = Doc.Sections[SecNdx]->Address;
 382
 383     // We assume that .dynstr is always allocatable.
 384     SHeader.sh_flags |= ELF::SHF_ALLOC;
 385   }
 386 }
 387
 388 template <class ELFT>
 389 void ELFState<ELFT>::setProgramHeaderLayout(std::vector<Elf_Phdr> &PHeaders,
 390                                             std::vector<Elf_Shdr> &SHeaders) {
 391   uint32_t PhdrIdx = 0;
 392   for (auto &YamlPhdr : Doc.ProgramHeaders) {
 393     Elf_Phdr &PHeader = PHeaders[PhdrIdx++];
 394
 395     std::vector<Elf_Shdr *> Sections;
 396     for (const ELFYAML::SectionName &SecName : YamlPhdr.Sections) {
 397       unsigned Index;
 398       if (SN2I.lookup(SecName.Section, Index)) {
 399         WithColor::error() << "Unknown section referenced: '" << SecName.Section
 400                            << "' by program header.\n";
 401         exit(1);
 402       }
 403       Sections.push_back(&SHeaders[Index]);
 404     }
 405
 406     if (YamlPhdr.Offset) {
 407       PHeader.p_offset = *YamlPhdr.Offset;
 408     } else {
 409       if (YamlPhdr.Sections.size())
 410         PHeader.p_offset = UINT32_MAX;
 411       else
 412         PHeader.p_offset = 0;
 413
 414       // Find the minimum offset for the program header.
 415       for (Elf_Shdr *SHeader : Sections)
 416         PHeader.p_offset = std::min(PHeader.p_offset, SHeader->sh_offset);
 417     }
 418
 419     // Find the maximum offset of the end of a section in order to set p_filesz,
 420     // if not set explicitly.
 421     if (YamlPhdr.FileSize) {
 422       PHeader.p_filesz = *YamlPhdr.FileSize;
 423     } else {
 424       PHeader.p_filesz = 0;
 425       for (Elf_Shdr *SHeader : Sections) {
 426         uint64_t EndOfSection;
 427         if (SHeader->sh_type == llvm::ELF::SHT_NOBITS)
 428           EndOfSection = SHeader->sh_offset;
 429         else
 430           EndOfSection = SHeader->sh_offset + SHeader->sh_size;
 431         uint64_t EndOfSegment = PHeader.p_offset + PHeader.p_filesz;
 432         EndOfSegment = std::max(EndOfSegment, EndOfSection);
 433         PHeader.p_filesz = EndOfSegment - PHeader.p_offset;
 434       }
 435     }
 436
 437     // If not set explicitly, find the memory size by adding the size of
 438     // sections at the end of the segment. These should be empty (size of zero)
 439     // and NOBITS sections.
 440     if (YamlPhdr.MemSize) {
 441       PHeader.p_memsz = *YamlPhdr.MemSize;
 442     } else {
 443       PHeader.p_memsz = PHeader.p_filesz;
 444       for (Elf_Shdr *SHeader : Sections)
 445         if (SHeader->sh_offset == PHeader.p_offset + PHeader.p_filesz)
 446           PHeader.p_memsz += SHeader->sh_size;
 447     }
 448
 449     // Set the alignment of the segment to be the same as the maximum alignment
 450     // of the sections with the same offset so that by default the segment
 451     // has a valid and sensible alignment.
 452     if (YamlPhdr.Align) {
 453       PHeader.p_align = *YamlPhdr.Align;
 454     } else {
 455       PHeader.p_align = 1;
 456       for (Elf_Shdr *SHeader : Sections)
 457         if (SHeader->sh_offset == PHeader.p_offset)
 458           PHeader.p_align = std::max(PHeader.p_align, SHeader->sh_addralign);
 459     }
 460   }
 461 }
 462
 463 template <class ELFT>
 464 void ELFState<ELFT>::addSymbols(ArrayRef<ELFYAML::Symbol> Symbols,
 465                                 std::vector<Elf_Sym> &Syms,
 466                                 const StringTableBuilder &Strtab) {
 467   for (const auto &Sym : Symbols) {
 468     Elf_Sym Symbol;
 469     zero(Symbol);
 470     if (!Sym.Name.empty())
 471       Symbol.st_name = Strtab.getOffset(Sym.Name);
 472     Symbol.setBindingAndType(Sym.Binding, Sym.Type);
 473     if (!Sym.Section.empty()) {
 474       unsigned Index;
 475       if (SN2I.lookup(Sym.Section, Index)) {
 476         WithColor::error() << "Unknown section referenced: '" << Sym.Section
 477                            << "' by YAML symbol " << Sym.Name << ".\n";
 478         exit(1);
 479       }
 480       Symbol.st_shndx = Index;
 481     } else if (Sym.Index) {
 482       Symbol.st_shndx = *Sym.Index;
 483     }
 484     // else Symbol.st_shndex == SHN_UNDEF (== 0), since it was zero'd earlier.
 485     Symbol.st_value = Sym.Value;
 486     Symbol.st_other = Sym.Other;
 487     Symbol.st_size = Sym.Size;
 488     Syms.push_back(Symbol);
 489   }
 490 }
 491
 492 template <class ELFT>
 493 bool ELFState<ELFT>::writeSectionContent(
 494     Elf_Shdr &SHeader, const ELFYAML::RawContentSection &Section,
 495     ContiguousBlobAccumulator &CBA) {
 496   assert(Section.Size >= Section.Content.binary_size() &&
 497          "Section size and section content are inconsistent");
 498   raw_ostream &OS =
 499       CBA.getOSAndAlignedOffset(SHeader.sh_offset, SHeader.sh_addralign);
 500   Section.Content.writeAsBinary(OS);
 501   OS.write_zeros(Section.Size - Section.Content.binary_size());
 502
 503   if (Section.EntSize)
 504     SHeader.sh_entsize = *Section.EntSize;
 505   else if (Section.Type == llvm::ELF::SHT_RELR)
 506     SHeader.sh_entsize = sizeof(Elf_Relr);
 507   else
 508     SHeader.sh_entsize = 0;
 509   SHeader.sh_size = Section.Size;
 510   SHeader.sh_info = Section.Info;
 511   return true;
 512 }
 513
 514 static bool isMips64EL(const ELFYAML::Object &Doc) {
 515   return Doc.Header.Machine == ELFYAML::ELF_EM(llvm::ELF::EM_MIPS) &&
 516          Doc.Header.Class == ELFYAML::ELF_ELFCLASS(ELF::ELFCLASS64) &&
 517          Doc.Header.Data == ELFYAML::ELF_ELFDATA(ELF::ELFDATA2LSB);
 518 }
 519
 520 template <class ELFT>
 521 bool
 522 ELFState<ELFT>::writeSectionContent(Elf_Shdr &SHeader,
 523                                     const ELFYAML::RelocationSection &Section,
 524                                     ContiguousBlobAccumulator &CBA) {
 525   assert((Section.Type == llvm::ELF::SHT_REL ||
 526           Section.Type == llvm::ELF::SHT_RELA) &&
 527          "Section type is not SHT_REL nor SHT_RELA");
 528
 529   bool IsRela = Section.Type == llvm::ELF::SHT_RELA;
 530   SHeader.sh_entsize = IsRela ? sizeof(Elf_Rela) : sizeof(Elf_Rel);
 531   SHeader.sh_size = SHeader.sh_entsize * Section.Relocations.size();
 532
 533   // For relocation section set link to .symtab by default.
 534   if (Section.Link.empty())
 535     SHeader.sh_link = getDotSymTabSecNo();
 536
 537   unsigned Index = 0;
 538   if (!Section.RelocatableSec.empty() &&
 539       !convertSectionIndex(SN2I, Section.Name, Section.RelocatableSec, Index))
 540     return false;
 541   SHeader.sh_info = Index;
 542
 543   auto &OS = CBA.getOSAndAlignedOffset(SHeader.sh_offset, SHeader.sh_addralign);
 544
 545   for (const auto &Rel : Section.Relocations) {
 546     unsigned SymIdx = 0;
 547     // If a relocation references a symbol, try to look one up in the symbol
 548     // table. If it is not there, treat the value as a symbol index.
 549     if (Rel.Symbol && SymN2I.lookup(*Rel.Symbol, SymIdx) &&
 550         !to_integer(*Rel.Symbol, SymIdx)) {
 551       WithColor::error() << "Unknown symbol referenced: '" << *Rel.Symbol
 552                          << "' at YAML section '" << Section.Name << "'.\n";
 553       return false;
 554     }
 555
 556     if (IsRela) {
 557       Elf_Rela REntry;
 558       zero(REntry);
 559       REntry.r_offset = Rel.Offset;
 560       REntry.r_addend = Rel.Addend;
 561       REntry.setSymbolAndType(SymIdx, Rel.Type, isMips64EL(Doc));
 562       OS.write((const char *)&REntry, sizeof(REntry));
 563     } else {
 564       Elf_Rel REntry;
 565       zero(REntry);
 566       REntry.r_offset = Rel.Offset;
 567       REntry.setSymbolAndType(SymIdx, Rel.Type, isMips64EL(Doc));
 568       OS.write((const char *)&REntry, sizeof(REntry));
 569     }
 570   }
 571   return true;
 572 }
 573
 574 template <class ELFT>
 575 bool ELFState<ELFT>::writeSectionContent(Elf_Shdr &SHeader,
 576                                          const ELFYAML::Group &Section,
 577                                          ContiguousBlobAccumulator &CBA) {
 578   assert(Section.Type == llvm::ELF::SHT_GROUP &&
 579          "Section type is not SHT_GROUP");
 580
 581   SHeader.sh_entsize = 4;
 582   SHeader.sh_size = SHeader.sh_entsize * Section.Members.size();
 583
 584   unsigned SymIdx;
 585   if (SymN2I.lookup(Section.Signature, SymIdx) &&
 586       !to_integer(Section.Signature, SymIdx)) {
 587     WithColor::error() << "Unknown symbol referenced: '" << Section.Signature
 588                        << "' at YAML section '" << Section.Name << "'.\n";
 589     return false;
 590   }
 591   SHeader.sh_info = SymIdx;
 592
 593   raw_ostream &OS =
 594       CBA.getOSAndAlignedOffset(SHeader.sh_offset, SHeader.sh_addralign);
 595
 596   for (const ELFYAML::SectionOrType &Member : Section.Members) {
 597     unsigned int SectionIndex = 0;
 598     if (Member.sectionNameOrType == "GRP_COMDAT")
 599       SectionIndex = llvm::ELF::GRP_COMDAT;
 600     else if (!convertSectionIndex(SN2I, Section.Name, Member.sectionNameOrType,
 601                                   SectionIndex))
 602       return false;
 603     support::endian::write<uint32_t>(OS, SectionIndex, ELFT::TargetEndianness);
 604   }
 605   return true;
 606 }
 607
 608 template <class ELFT>
 609 bool ELFState<ELFT>::writeSectionContent(Elf_Shdr &SHeader,
 610                                          const ELFYAML::SymverSection &Section,
 611                                          ContiguousBlobAccumulator &CBA) {
 612   raw_ostream &OS =
 613       CBA.getOSAndAlignedOffset(SHeader.sh_offset, SHeader.sh_addralign);
 614   for (uint16_t Version : Section.Entries)
 615     support::endian::write<uint16_t>(OS, Version, ELFT::TargetEndianness);
 616
 617   SHeader.sh_entsize = 2;
 618   SHeader.sh_size = Section.Entries.size() * SHeader.sh_entsize;
 619   return true;
 620 }
 621
 622 template <class ELFT>
 623 bool ELFState<ELFT>::writeSectionContent(Elf_Shdr &SHeader,
 624                                          const ELFYAML::VerdefSection &Section,
 625                                          ContiguousBlobAccumulator &CBA) {
 626   typedef typename ELFT::Verdef Elf_Verdef;
 627   typedef typename ELFT::Verdaux Elf_Verdaux;
 628   raw_ostream &OS =
 629       CBA.getOSAndAlignedOffset(SHeader.sh_offset, SHeader.sh_addralign);
 630
 631   uint64_t AuxCnt = 0;
 632   for (size_t I = 0; I < Section.Entries.size(); ++I) {
 633     const ELFYAML::VerdefEntry &E = Section.Entries[I];
 634
 635     Elf_Verdef VerDef;
 636     VerDef.vd_version = E.Version;
 637     VerDef.vd_flags = E.Flags;
 638     VerDef.vd_ndx = E.VersionNdx;
 639     VerDef.vd_hash = E.Hash;
 640     VerDef.vd_aux = sizeof(Elf_Verdef);
 641     VerDef.vd_cnt = E.VerNames.size();
 642     if (I == Section.Entries.size() - 1)
 643       VerDef.vd_next = 0;
 644     else
 645       VerDef.vd_next =
 646           sizeof(Elf_Verdef) + E.VerNames.size() * sizeof(Elf_Verdaux);
 647     OS.write((const char *)&VerDef, sizeof(Elf_Verdef));
 648
 649     for (size_t J = 0; J < E.VerNames.size(); ++J, ++AuxCnt) {
 650       Elf_Verdaux VernAux;
 651       VernAux.vda_name = DotDynstr.getOffset(E.VerNames[J]);
 652       if (J == E.VerNames.size() - 1)
 653         VernAux.vda_next = 0;
 654       else
 655         VernAux.vda_next = sizeof(Elf_Verdaux);
 656       OS.write((const char *)&VernAux, sizeof(Elf_Verdaux));
 657     }
 658   }
 659
 660   SHeader.sh_size = Section.Entries.size() * sizeof(Elf_Verdef) +
 661                     AuxCnt * sizeof(Elf_Verdaux);
 662   SHeader.sh_info = Section.Info;
 663
 664   return true;
 665 }
 666
 667 template <class ELFT>
 668 bool ELFState<ELFT>::writeSectionContent(Elf_Shdr &SHeader,
 669                                          const ELFYAML::VerneedSection &Section,
 670                                          ContiguousBlobAccumulator &CBA) {
 671   typedef typename ELFT::Verneed Elf_Verneed;
 672   typedef typename ELFT::Vernaux Elf_Vernaux;
 673
 674   auto &OS = CBA.getOSAndAlignedOffset(SHeader.sh_offset, SHeader.sh_addralign);
 675
 676   uint64_t AuxCnt = 0;
 677   for (size_t I = 0; I < Section.VerneedV.size(); ++I) {
 678     const ELFYAML::VerneedEntry &VE = Section.VerneedV[I];
 679
 680     Elf_Verneed VerNeed;
 681     VerNeed.vn_version = VE.Version;
 682     VerNeed.vn_file = DotDynstr.getOffset(VE.File);
 683     if (I == Section.VerneedV.size() - 1)
 684       VerNeed.vn_next = 0;
 685     else
 686       VerNeed.vn_next =
 687           sizeof(Elf_Verneed) + VE.AuxV.size() * sizeof(Elf_Vernaux);
 688     VerNeed.vn_cnt = VE.AuxV.size();
 689     VerNeed.vn_aux = sizeof(Elf_Verneed);
 690     OS.write((const char *)&VerNeed, sizeof(Elf_Verneed));
 691
 692     for (size_t J = 0; J < VE.AuxV.size(); ++J, ++AuxCnt) {
 693       const ELFYAML::VernauxEntry &VAuxE = VE.AuxV[J];
 694
 695       Elf_Vernaux VernAux;
 696       VernAux.vna_hash = VAuxE.Hash;
 697       VernAux.vna_flags = VAuxE.Flags;
 698       VernAux.vna_other = VAuxE.Other;
 699       VernAux.vna_name = DotDynstr.getOffset(VAuxE.Name);
 700       if (J == VE.AuxV.size() - 1)
 701         VernAux.vna_next = 0;
 702       else
 703         VernAux.vna_next = sizeof(Elf_Vernaux);
 704       OS.write((const char *)&VernAux, sizeof(Elf_Vernaux));
 705     }
 706   }
 707
 708   SHeader.sh_size = Section.VerneedV.size() * sizeof(Elf_Verneed) +
 709                     AuxCnt * sizeof(Elf_Vernaux);
 710   SHeader.sh_info = Section.Info;
 711
 712   return true;
 713 }
 714
 715 template <class ELFT>
 716 bool ELFState<ELFT>::writeSectionContent(Elf_Shdr &SHeader,
 717                                          const ELFYAML::MipsABIFlags &Section,
 718                                          ContiguousBlobAccumulator &CBA) {
 719   assert(Section.Type == llvm::ELF::SHT_MIPS_ABIFLAGS &&
 720          "Section type is not SHT_MIPS_ABIFLAGS");
 721
 722   object::Elf_Mips_ABIFlags<ELFT> Flags;
 723   zero(Flags);
 724   SHeader.sh_entsize = sizeof(Flags);
 725   SHeader.sh_size = SHeader.sh_entsize;
 726
 727   auto &OS = CBA.getOSAndAlignedOffset(SHeader.sh_offset, SHeader.sh_addralign);
 728   Flags.version = Section.Version;
 729   Flags.isa_level = Section.ISALevel;
 730   Flags.isa_rev = Section.ISARevision;
 731   Flags.gpr_size = Section.GPRSize;
 732   Flags.cpr1_size = Section.CPR1Size;
 733   Flags.cpr2_size = Section.CPR2Size;
 734   Flags.fp_abi = Section.FpABI;
 735   Flags.isa_ext = Section.ISAExtension;
 736   Flags.ases = Section.ASEs;
 737   Flags.flags1 = Section.Flags1;
 738   Flags.flags2 = Section.Flags2;
 739   OS.write((const char *)&Flags, sizeof(Flags));
 740
 741   return true;
 742 }
 743
 744 template <class ELFT>
 745 bool ELFState<ELFT>::writeSectionContent(Elf_Shdr &SHeader,
 746                                          const ELFYAML::DynamicSection &Section,
 747                                          ContiguousBlobAccumulator &CBA) {
 748   typedef typename ELFT::uint uintX_t;
 749
 750   assert(Section.Type == llvm::ELF::SHT_DYNAMIC &&
 751          "Section type is not SHT_DYNAMIC");
 752
 753   if (!Section.Entries.empty() && Section.Content) {
 754     WithColor::error()
 755         << "Cannot specify both raw content and explicit entries "
 756            "for dynamic section '"
 757         << Section.Name << "'.\n";
 758     return false;
 759   }
 760
 761   if (Section.Content)
 762     SHeader.sh_size = Section.Content->binary_size();
 763   else
 764     SHeader.sh_size = 2 * sizeof(uintX_t) * Section.Entries.size();
 765   if (Section.EntSize)
 766     SHeader.sh_entsize = *Section.EntSize;
 767   else
 768     SHeader.sh_entsize = sizeof(Elf_Dyn);
 769
 770   raw_ostream &OS = CBA.getOSAndAlignedOffset(SHeader.sh_offset, SHeader.sh_addralign);
 771   for (const ELFYAML::DynamicEntry &DE : Section.Entries) {
 772     support::endian::write<uintX_t>(OS, DE.Tag, ELFT::TargetEndianness);
 773     support::endian::write<uintX_t>(OS, DE.Val, ELFT::TargetEndianness);
 774   }
 775   if (Section.Content)
 776     Section.Content->writeAsBinary(OS);
 777
 778   return true;
 779 }
 780
 781 template <class ELFT> bool ELFState<ELFT>::buildSectionIndex() {
 782   for (unsigned i = 0, e = Doc.Sections.size(); i != e; ++i) {
 783     StringRef Name = Doc.Sections[i]->Name;
 784     DotShStrtab.add(Name);
 785     // "+ 1" to take into account the SHT_NULL entry.
 786     if (SN2I.addName(Name, i + 1)) {
 787       WithColor::error() << "Repeated section name: '" << Name
 788                          << "' at YAML section number " << i << ".\n";
 789       return false;
 790     }
 791   }
 792
 793   auto SecNo = 1 + Doc.Sections.size();
 794   // Add special sections after input sections, if necessary.
 795   for (StringRef Name : implicitSectionNames())
 796     if (!SN2I.addName(Name, SecNo)) {
 797       // Account for this section, since it wasn't in the Doc
 798       ++SecNo;
 799       DotShStrtab.add(Name);
 800     }
 801
 802   DotShStrtab.finalize();
 803   return true;
 804 }
 805
 806 template <class ELFT>
 807 bool ELFState<ELFT>::buildSymbolIndex(ArrayRef<ELFYAML::Symbol> Symbols) {
 808   bool GlobalSymbolSeen = false;
 809   std::size_t I = 0;
 810   for (const auto &Sym : Symbols) {
 811     ++I;
 812
 813     StringRef Name = Sym.Name;
 814     if (Sym.Binding.value == ELF::STB_LOCAL && GlobalSymbolSeen) {
 815       WithColor::error() << "Local symbol '" + Name +
 816                                 "' after global in Symbols list.\n";
 817       return false;
 818     }
 819     if (Sym.Binding.value != ELF::STB_LOCAL)
 820       GlobalSymbolSeen = true;
 821
 822     if (!Name.empty() && SymN2I.addName(Name, I)) {
 823       WithColor::error() << "Repeated symbol name: '" << Name << "'.\n";
 824       return false;
 825     }
 826   }
 827   return true;
 828 }
 829
 830 template <class ELFT> void ELFState<ELFT>::finalizeStrings() {
 831   // Add the regular symbol names to .strtab section.
 832   for (const ELFYAML::Symbol &Sym : Doc.Symbols)
 833     DotStrtab.add(Sym.Name);
 834   DotStrtab.finalize();
 835
 836   if (Doc.DynamicSymbols.empty())
 837     return;
 838
 839   // Add the dynamic symbol names to .dynstr section.
 840   for (const ELFYAML::Symbol &Sym : Doc.DynamicSymbols)
 841     DotDynstr.add(Sym.Name);
 842
 843   // SHT_GNU_verdef and SHT_GNU_verneed sections might also
 844   // add strings to .dynstr section.
 845   for (const std::unique_ptr<ELFYAML::Section> &Sec : Doc.Sections) {
 846     if (auto VerNeed = dyn_cast<ELFYAML::VerneedSection>(Sec.get())) {
 847       for (const ELFYAML::VerneedEntry &VE : VerNeed->VerneedV) {
 848         DotDynstr.add(VE.File);
 849         for (const ELFYAML::VernauxEntry &Aux : VE.AuxV)
 850           DotDynstr.add(Aux.Name);
 851       }
 852     } else if (auto VerDef = dyn_cast<ELFYAML::VerdefSection>(Sec.get())) {
 853       for (const ELFYAML::VerdefEntry &E : VerDef->Entries)
 854         for (StringRef Name : E.VerNames)
 855           DotDynstr.add(Name);
 856     }
 857   }
 858
 859   DotDynstr.finalize();
 860 }
 861
 862 template <class ELFT>
 863 int ELFState<ELFT>::writeELF(raw_ostream &OS, const ELFYAML::Object &Doc) {
 864   ELFState<ELFT> State(Doc);
 865
 866   // Finalize .strtab and .dynstr sections. We do that early because want to
 867   // finalize the string table builders before writing the content of the
 868   // sections that might want to use them.
 869   State.finalizeStrings();
 870
 871   if (!State.buildSectionIndex())
 872     return 1;
 873
 874   if (!State.buildSymbolIndex(Doc.Symbols))
 875     return 1;
 876
 877   Elf_Ehdr Header;
 878   State.initELFHeader(Header);
 879
 880   // TODO: Flesh out section header support.
 881
 882   std::vector<Elf_Phdr> PHeaders;
 883   State.initProgramHeaders(PHeaders);
 884
 885   // XXX: This offset is tightly coupled with the order that we write
 886   // things to `OS`.
 887   const size_t SectionContentBeginOffset = Header.e_ehsize +
 888                                            Header.e_phentsize * Header.e_phnum +
 889                                            Header.e_shentsize * Header.e_shnum;
 890   ContiguousBlobAccumulator CBA(SectionContentBeginOffset);
 891
 892   std::vector<Elf_Shdr> SHeaders;
 893   if (!State.initSectionHeaders(SHeaders, CBA))
 894     return 1;
 895
 896   // Populate SHeaders with implicit sections not present in the Doc
 897   for (StringRef Name : State.implicitSectionNames())
 898     if (State.SN2I.get(Name) >= SHeaders.size())
 899       SHeaders.push_back({});
 900
 901   // Initialize the implicit sections
 902   State.initSymtabSectionHeader(SHeaders[State.SN2I.get(".symtab")],
 903                                 SymtabType::Static, CBA);
 904   State.initStrtabSectionHeader(SHeaders[State.SN2I.get(".strtab")], ".strtab",
 905                                 State.DotStrtab, CBA);
 906   State.initStrtabSectionHeader(SHeaders[State.SN2I.get(".shstrtab")],
 907                                 ".shstrtab", State.DotShStrtab, CBA);
 908   if (!Doc.DynamicSymbols.empty()) {
 909     State.initSymtabSectionHeader(SHeaders[State.SN2I.get(".dynsym")],
 910                                   SymtabType::Dynamic, CBA);
 911     State.initStrtabSectionHeader(SHeaders[State.SN2I.get(".dynstr")],
 912                                   ".dynstr", State.DotDynstr, CBA);
 913   }
 914
 915   // Now we can decide segment offsets
 916   State.setProgramHeaderLayout(PHeaders, SHeaders);
 917
 918   OS.write((const char *)&Header, sizeof(Header));
 919   writeArrayData(OS, makeArrayRef(PHeaders));
 920   writeArrayData(OS, makeArrayRef(SHeaders));
 921   CBA.writeBlobToStream(OS);
 922   return 0;
 923 }
 924
 925 template <class ELFT>
 926 std::vector<StringRef> ELFState<ELFT>::implicitSectionNames() const {
 927   if (Doc.DynamicSymbols.empty())
 928     return {".symtab", ".strtab", ".shstrtab"};
 929   return {".symtab", ".strtab", ".shstrtab", ".dynsym", ".dynstr"};
 930 }
 931
 932 int yaml2elf(llvm::ELFYAML::Object &Doc, raw_ostream &Out) {
 933   bool IsLE = Doc.Header.Data == ELFYAML::ELF_ELFDATA(ELF::ELFDATA2LSB);
 934   bool Is64Bit = Doc.Header.Class == ELFYAML::ELF_ELFCLASS(ELF::ELFCLASS64);
 935   if (Is64Bit) {
 936     if (IsLE)
 937       return ELFState<object::ELF64LE>::writeELF(Out, Doc);
 938     return ELFState<object::ELF64BE>::writeELF(Out, Doc);
 939   }
 940   if (IsLE)
 941     return ELFState<object::ELF32LE>::writeELF(Out, Doc);
 942   return ELFState<object::ELF32BE>::writeELF(Out, Doc);
 943 }