1 //===- yaml2elf - Convert YAML to a ELF object file -----------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
11 /// \brief The ELF component of yaml2obj.
13 //===----------------------------------------------------------------------===//
16 #include "llvm/ADT/ArrayRef.h"
17 #include "llvm/MC/StringTableBuilder.h"
18 #include "llvm/Object/ELFObjectFile.h"
19 #include "llvm/Object/ELFYAML.h"
20 #include "llvm/Support/ELF.h"
21 #include "llvm/Support/MemoryBuffer.h"
22 #include "llvm/Support/YAMLTraits.h"
23 #include "llvm/Support/raw_ostream.h"
27 // This class is used to build up a contiguous binary blob while keeping
28 // track of an offset in the output (which notionally begins at
31 class ContiguousBlobAccumulator {
32 const uint64_t InitialOffset;
33 SmallVector<char, 128> Buf;
34 raw_svector_ostream OS;
36 /// \returns The new offset.
37 uint64_t padToAlignment(unsigned Align) {
38 uint64_t CurrentOffset = InitialOffset + OS.tell();
39 uint64_t AlignedOffset = RoundUpToAlignment(CurrentOffset, Align);
40 for (; CurrentOffset != AlignedOffset; ++CurrentOffset)
42 return AlignedOffset; // == CurrentOffset;
46 ContiguousBlobAccumulator(uint64_t InitialOffset_)
47 : InitialOffset(InitialOffset_), Buf(), OS(Buf) {}
48 template <class Integer>
49 raw_ostream &getOSAndAlignedOffset(Integer &Offset, unsigned Align = 16) {
50 Offset = padToAlignment(Align);
53 void writeBlobToStream(raw_ostream &Out) { Out << OS.str(); }
55 } // end anonymous namespace
57 // Used to keep track of section and symbol names, so that in the YAML file
58 // sections and symbols can be referenced by name instead of by index.
63 /// \returns true if name is already present in the map.
64 bool addName(StringRef Name, unsigned i) {
65 return !Map.insert(std::make_pair(Name, (int)i)).second;
67 /// \returns true if name is not present in the map
68 bool lookup(StringRef Name, unsigned &Idx) const {
69 StringMap<int>::const_iterator I = Map.find(Name);
76 } // end anonymous namespace
79 static size_t arrayDataSize(ArrayRef<T> A) {
80 return A.size() * sizeof(T);
84 static void writeArrayData(raw_ostream &OS, ArrayRef<T> A) {
85 OS.write((const char *)A.data(), arrayDataSize(A));
89 static void zero(T &Obj) {
90 memset(&Obj, 0, sizeof(Obj));
94 /// \brief "Single point of truth" for the ELF file construction.
95 /// TODO: This class still has a ways to go before it is truly a "single
99 typedef typename object::ELFFile<ELFT>::Elf_Ehdr Elf_Ehdr;
100 typedef typename object::ELFFile<ELFT>::Elf_Shdr Elf_Shdr;
101 typedef typename object::ELFFile<ELFT>::Elf_Sym Elf_Sym;
102 typedef typename object::ELFFile<ELFT>::Elf_Rel Elf_Rel;
103 typedef typename object::ELFFile<ELFT>::Elf_Rela Elf_Rela;
105 /// \brief The future ".strtab" section.
106 StringTableBuilder DotStrtab;
108 /// \brief The future ".shstrtab" section.
109 StringTableBuilder DotShStrtab;
113 const ELFYAML::Object &Doc;
115 bool buildSectionIndex();
116 bool buildSymbolIndex(std::size_t &StartIndex,
117 const std::vector<ELFYAML::Symbol> &Symbols);
118 void initELFHeader(Elf_Ehdr &Header);
119 bool initSectionHeaders(std::vector<Elf_Shdr> &SHeaders,
120 ContiguousBlobAccumulator &CBA);
121 void initSymtabSectionHeader(Elf_Shdr &SHeader,
122 ContiguousBlobAccumulator &CBA);
123 void initStrtabSectionHeader(Elf_Shdr &SHeader, StringRef Name,
124 StringTableBuilder &STB,
125 ContiguousBlobAccumulator &CBA);
126 void addSymbols(const std::vector<ELFYAML::Symbol> &Symbols,
127 std::vector<Elf_Sym> &Syms, unsigned SymbolBinding);
128 void writeSectionContent(Elf_Shdr &SHeader,
129 const ELFYAML::RawContentSection &Section,
130 ContiguousBlobAccumulator &CBA);
131 bool writeSectionContent(Elf_Shdr &SHeader,
132 const ELFYAML::RelocationSection &Section,
133 ContiguousBlobAccumulator &CBA);
134 bool writeSectionContent(Elf_Shdr &SHeader, const ELFYAML::Group &Group,
135 ContiguousBlobAccumulator &CBA);
137 // - SHT_NULL entry (placed first, i.e. 0'th entry)
138 // - symbol table (.symtab) (placed third to last)
139 // - string table (.strtab) (placed second to last)
140 // - section header string table (.shstrtab) (placed last)
141 unsigned getDotSymTabSecNo() const { return Doc.Sections.size() + 1; }
142 unsigned getDotStrTabSecNo() const { return Doc.Sections.size() + 2; }
143 unsigned getDotShStrTabSecNo() const { return Doc.Sections.size() + 3; }
144 unsigned getSectionCount() const { return Doc.Sections.size() + 4; }
146 ELFState(const ELFYAML::Object &D) : Doc(D) {}
149 static int writeELF(raw_ostream &OS, const ELFYAML::Object &Doc);
151 } // end anonymous namespace
153 template <class ELFT>
154 void ELFState<ELFT>::initELFHeader(Elf_Ehdr &Header) {
155 using namespace llvm::ELF;
157 Header.e_ident[EI_MAG0] = 0x7f;
158 Header.e_ident[EI_MAG1] = 'E';
159 Header.e_ident[EI_MAG2] = 'L';
160 Header.e_ident[EI_MAG3] = 'F';
161 Header.e_ident[EI_CLASS] = ELFT::Is64Bits ? ELFCLASS64 : ELFCLASS32;
162 bool IsLittleEndian = ELFT::TargetEndianness == support::little;
163 Header.e_ident[EI_DATA] = IsLittleEndian ? ELFDATA2LSB : ELFDATA2MSB;
164 Header.e_ident[EI_VERSION] = EV_CURRENT;
165 Header.e_ident[EI_OSABI] = Doc.Header.OSABI;
166 Header.e_ident[EI_ABIVERSION] = 0;
167 Header.e_type = Doc.Header.Type;
168 Header.e_machine = Doc.Header.Machine;
169 Header.e_version = EV_CURRENT;
170 Header.e_entry = Doc.Header.Entry;
171 Header.e_flags = Doc.Header.Flags;
172 Header.e_ehsize = sizeof(Elf_Ehdr);
173 Header.e_shentsize = sizeof(Elf_Shdr);
174 // Immediately following the ELF header.
175 Header.e_shoff = sizeof(Header);
176 Header.e_shnum = getSectionCount();
177 Header.e_shstrndx = getDotShStrTabSecNo();
180 template <class ELFT>
181 bool ELFState<ELFT>::initSectionHeaders(std::vector<Elf_Shdr> &SHeaders,
182 ContiguousBlobAccumulator &CBA) {
183 // Ensure SHN_UNDEF entry is present. An all-zero section header is a
184 // valid SHN_UNDEF entry since SHT_NULL == 0.
187 SHeaders.push_back(SHeader);
189 for (const auto &Sec : Doc.Sections)
190 DotShStrtab.add(Sec->Name);
191 DotShStrtab.finalize(StringTableBuilder::ELF);
193 for (const auto &Sec : Doc.Sections) {
195 SHeader.sh_name = DotShStrtab.getOffset(Sec->Name);
196 SHeader.sh_type = Sec->Type;
197 SHeader.sh_flags = Sec->Flags;
198 SHeader.sh_addr = Sec->Address;
199 SHeader.sh_addralign = Sec->AddressAlign;
201 if (!Sec->Link.empty()) {
203 if (SN2I.lookup(Sec->Link, Index)) {
204 errs() << "error: Unknown section referenced: '" << Sec->Link
205 << "' at YAML section '" << Sec->Name << "'.\n";
208 SHeader.sh_link = Index;
211 if (auto S = dyn_cast<ELFYAML::RawContentSection>(Sec.get()))
212 writeSectionContent(SHeader, *S, CBA);
213 else if (auto S = dyn_cast<ELFYAML::RelocationSection>(Sec.get())) {
215 // For relocation section set link to .symtab by default.
216 SHeader.sh_link = getDotSymTabSecNo();
219 if (SN2I.lookup(S->Info, Index)) {
220 errs() << "error: Unknown section referenced: '" << S->Info
221 << "' at YAML section '" << S->Name << "'.\n";
224 SHeader.sh_info = Index;
226 if (!writeSectionContent(SHeader, *S, CBA))
228 } else if (auto S = dyn_cast<ELFYAML::Group>(Sec.get())) {
230 if (SymN2I.lookup(S->Info, SymIdx)) {
231 errs() << "error: Unknown symbol referenced: '" << S->Info
232 << "' at YAML section '" << S->Name << "'.\n";
235 SHeader.sh_info = SymIdx;
236 if (!writeSectionContent(SHeader, *S, CBA))
239 llvm_unreachable("Unknown section type");
241 SHeaders.push_back(SHeader);
246 template <class ELFT>
247 void ELFState<ELFT>::initSymtabSectionHeader(Elf_Shdr &SHeader,
248 ContiguousBlobAccumulator &CBA) {
250 SHeader.sh_name = DotShStrtab.getOffset(".symtab");
251 SHeader.sh_type = ELF::SHT_SYMTAB;
252 SHeader.sh_link = getDotStrTabSecNo();
253 // One greater than symbol table index of the last local symbol.
254 SHeader.sh_info = Doc.Symbols.Local.size() + 1;
255 SHeader.sh_entsize = sizeof(Elf_Sym);
257 std::vector<Elf_Sym> Syms;
259 // Ensure STN_UNDEF is present
265 // Add symbol names to .strtab.
266 for (const auto &Sym : Doc.Symbols.Local)
267 DotStrtab.add(Sym.Name);
268 for (const auto &Sym : Doc.Symbols.Global)
269 DotStrtab.add(Sym.Name);
270 for (const auto &Sym : Doc.Symbols.Weak)
271 DotStrtab.add(Sym.Name);
272 DotStrtab.finalize(StringTableBuilder::ELF);
274 addSymbols(Doc.Symbols.Local, Syms, ELF::STB_LOCAL);
275 addSymbols(Doc.Symbols.Global, Syms, ELF::STB_GLOBAL);
276 addSymbols(Doc.Symbols.Weak, Syms, ELF::STB_WEAK);
278 writeArrayData(CBA.getOSAndAlignedOffset(SHeader.sh_offset),
280 SHeader.sh_size = arrayDataSize(makeArrayRef(Syms));
283 template <class ELFT>
284 void ELFState<ELFT>::initStrtabSectionHeader(Elf_Shdr &SHeader, StringRef Name,
285 StringTableBuilder &STB,
286 ContiguousBlobAccumulator &CBA) {
288 SHeader.sh_name = DotShStrtab.getOffset(Name);
289 SHeader.sh_type = ELF::SHT_STRTAB;
290 CBA.getOSAndAlignedOffset(SHeader.sh_offset) << STB.data();
291 SHeader.sh_size = STB.data().size();
292 SHeader.sh_addralign = 1;
295 template <class ELFT>
296 void ELFState<ELFT>::addSymbols(const std::vector<ELFYAML::Symbol> &Symbols,
297 std::vector<Elf_Sym> &Syms,
298 unsigned SymbolBinding) {
299 for (const auto &Sym : Symbols) {
302 if (!Sym.Name.empty())
303 Symbol.st_name = DotStrtab.getOffset(Sym.Name);
304 Symbol.setBindingAndType(SymbolBinding, Sym.Type);
305 if (!Sym.Section.empty()) {
307 if (SN2I.lookup(Sym.Section, Index)) {
308 errs() << "error: Unknown section referenced: '" << Sym.Section
309 << "' by YAML symbol " << Sym.Name << ".\n";
312 Symbol.st_shndx = Index;
313 } // else Symbol.st_shndex == SHN_UNDEF (== 0), since it was zero'd earlier.
314 Symbol.st_value = Sym.Value;
315 Symbol.st_other = Sym.Other;
316 Symbol.st_size = Sym.Size;
317 Syms.push_back(Symbol);
321 template <class ELFT>
323 ELFState<ELFT>::writeSectionContent(Elf_Shdr &SHeader,
324 const ELFYAML::RawContentSection &Section,
325 ContiguousBlobAccumulator &CBA) {
326 assert(Section.Size >= Section.Content.binary_size() &&
327 "Section size and section content are inconsistent");
328 raw_ostream &OS = CBA.getOSAndAlignedOffset(SHeader.sh_offset);
329 Section.Content.writeAsBinary(OS);
330 for (auto i = Section.Content.binary_size(); i < Section.Size; ++i)
332 SHeader.sh_entsize = 0;
333 SHeader.sh_size = Section.Size;
336 static bool isMips64EL(const ELFYAML::Object &Doc) {
337 return Doc.Header.Machine == ELFYAML::ELF_EM(llvm::ELF::EM_MIPS) &&
338 Doc.Header.Class == ELFYAML::ELF_ELFCLASS(ELF::ELFCLASS64) &&
339 Doc.Header.Data == ELFYAML::ELF_ELFDATA(ELF::ELFDATA2LSB);
342 template <class ELFT>
344 ELFState<ELFT>::writeSectionContent(Elf_Shdr &SHeader,
345 const ELFYAML::RelocationSection &Section,
346 ContiguousBlobAccumulator &CBA) {
347 if (Section.Type != llvm::ELF::SHT_REL &&
348 Section.Type != llvm::ELF::SHT_RELA) {
349 errs() << "error: Invalid relocation section type.\n";
353 bool IsRela = Section.Type == llvm::ELF::SHT_RELA;
354 SHeader.sh_entsize = IsRela ? sizeof(Elf_Rela) : sizeof(Elf_Rel);
355 SHeader.sh_size = SHeader.sh_entsize * Section.Relocations.size();
357 auto &OS = CBA.getOSAndAlignedOffset(SHeader.sh_offset);
359 for (const auto &Rel : Section.Relocations) {
361 if (SymN2I.lookup(Rel.Symbol, SymIdx)) {
362 errs() << "error: Unknown symbol referenced: '" << Rel.Symbol
363 << "' at YAML relocation.\n";
370 REntry.r_offset = Rel.Offset;
371 REntry.r_addend = Rel.Addend;
372 REntry.setSymbolAndType(SymIdx, Rel.Type, isMips64EL(Doc));
373 OS.write((const char *)&REntry, sizeof(REntry));
377 REntry.r_offset = Rel.Offset;
378 REntry.setSymbolAndType(SymIdx, Rel.Type, isMips64EL(Doc));
379 OS.write((const char *)&REntry, sizeof(REntry));
385 template <class ELFT>
386 bool ELFState<ELFT>::writeSectionContent(Elf_Shdr &SHeader,
387 const ELFYAML::Group &Section,
388 ContiguousBlobAccumulator &CBA) {
389 typedef typename object::ELFFile<ELFT>::Elf_Word Elf_Word;
390 if (Section.Type != llvm::ELF::SHT_GROUP) {
391 errs() << "error: Invalid section type.\n";
395 SHeader.sh_entsize = sizeof(Elf_Word);
396 SHeader.sh_size = SHeader.sh_entsize * Section.Members.size();
398 auto &OS = CBA.getOSAndAlignedOffset(SHeader.sh_offset);
400 for (auto member : Section.Members) {
402 unsigned int sectionIndex = 0;
403 if (member.sectionNameOrType == "GRP_COMDAT")
404 sectionIndex = llvm::ELF::GRP_COMDAT;
405 else if (SN2I.lookup(member.sectionNameOrType, sectionIndex)) {
406 errs() << "error: Unknown section referenced: '"
407 << member.sectionNameOrType << "' at YAML section' "
408 << Section.Name << "\n";
412 OS.write((const char *)&SIdx, sizeof(SIdx));
417 template <class ELFT> bool ELFState<ELFT>::buildSectionIndex() {
418 SN2I.addName(".symtab", getDotSymTabSecNo());
419 SN2I.addName(".strtab", getDotStrTabSecNo());
420 SN2I.addName(".shstrtab", getDotShStrTabSecNo());
422 for (unsigned i = 0, e = Doc.Sections.size(); i != e; ++i) {
423 StringRef Name = Doc.Sections[i]->Name;
426 // "+ 1" to take into account the SHT_NULL entry.
427 if (SN2I.addName(Name, i + 1)) {
428 errs() << "error: Repeated section name: '" << Name
429 << "' at YAML section number " << i << ".\n";
436 template <class ELFT>
438 ELFState<ELFT>::buildSymbolIndex(std::size_t &StartIndex,
439 const std::vector<ELFYAML::Symbol> &Symbols) {
440 for (const auto &Sym : Symbols) {
442 if (Sym.Name.empty())
444 if (SymN2I.addName(Sym.Name, StartIndex)) {
445 errs() << "error: Repeated symbol name: '" << Sym.Name << "'.\n";
452 template <class ELFT>
453 int ELFState<ELFT>::writeELF(raw_ostream &OS, const ELFYAML::Object &Doc) {
454 ELFState<ELFT> State(Doc);
455 if (!State.buildSectionIndex())
458 std::size_t StartSymIndex = 0;
459 if (!State.buildSymbolIndex(StartSymIndex, Doc.Symbols.Local) ||
460 !State.buildSymbolIndex(StartSymIndex, Doc.Symbols.Global) ||
461 !State.buildSymbolIndex(StartSymIndex, Doc.Symbols.Weak))
465 State.initELFHeader(Header);
467 // TODO: Flesh out section header support.
468 // TODO: Program headers.
470 // XXX: This offset is tightly coupled with the order that we write
472 const size_t SectionContentBeginOffset =
473 Header.e_ehsize + Header.e_shentsize * Header.e_shnum;
474 ContiguousBlobAccumulator CBA(SectionContentBeginOffset);
476 // Doc might not contain .symtab, .strtab and .shstrtab sections,
477 // but we will emit them, so make sure to add them to ShStrTabSHeader.
478 State.DotShStrtab.add(".symtab");
479 State.DotShStrtab.add(".strtab");
480 State.DotShStrtab.add(".shstrtab");
482 std::vector<Elf_Shdr> SHeaders;
483 if(!State.initSectionHeaders(SHeaders, CBA))
487 Elf_Shdr SymtabSHeader;
488 State.initSymtabSectionHeader(SymtabSHeader, CBA);
489 SHeaders.push_back(SymtabSHeader);
491 // .strtab string table header.
492 Elf_Shdr DotStrTabSHeader;
493 State.initStrtabSectionHeader(DotStrTabSHeader, ".strtab", State.DotStrtab,
495 SHeaders.push_back(DotStrTabSHeader);
497 // .shstrtab string table header.
498 Elf_Shdr ShStrTabSHeader;
499 State.initStrtabSectionHeader(ShStrTabSHeader, ".shstrtab", State.DotShStrtab,
501 SHeaders.push_back(ShStrTabSHeader);
503 OS.write((const char *)&Header, sizeof(Header));
504 writeArrayData(OS, makeArrayRef(SHeaders));
505 CBA.writeBlobToStream(OS);
509 static bool is64Bit(const ELFYAML::Object &Doc) {
510 return Doc.Header.Class == ELFYAML::ELF_ELFCLASS(ELF::ELFCLASS64);
513 static bool isLittleEndian(const ELFYAML::Object &Doc) {
514 return Doc.Header.Data == ELFYAML::ELF_ELFDATA(ELF::ELFDATA2LSB);
517 int yaml2elf(yaml::Input &YIn, raw_ostream &Out) {
521 errs() << "yaml2obj: Failed to parse YAML file!\n";
524 using object::ELFType;
525 typedef ELFType<support::little, 8, true> LE64;
526 typedef ELFType<support::big, 8, true> BE64;
527 typedef ELFType<support::little, 4, false> LE32;
528 typedef ELFType<support::big, 4, false> BE32;
530 if (isLittleEndian(Doc))
531 return ELFState<LE64>::writeELF(Out, Doc);
533 return ELFState<BE64>::writeELF(Out, Doc);
535 if (isLittleEndian(Doc))
536 return ELFState<LE32>::writeELF(Out, Doc);
538 return ELFState<BE32>::writeELF(Out, Doc);