1 //===-- ELFWriter.cpp - Target-independent ELF Writer code ----------------===//
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 //===----------------------------------------------------------------------===//
10 // This file implements the target-independent ELF writer. This file writes out
11 // the ELF file in the following order:
14 // #2. '.text' section
15 // #3. '.data' section
16 // #4. '.bss' section (conceptual position in file)
18 // #X. '.shstrtab' section
21 // The entries in the section table are laid out as:
22 // #0. Null entry [required]
23 // #1. ".text" entry - the program code
24 // #2. ".data" entry - global variables with initializers. [ if needed ]
25 // #3. ".bss" entry - global variables without initializers. [ if needed ]
27 // #N. ".shstrtab" entry - String table for the section names.
29 //===----------------------------------------------------------------------===//
31 #define DEBUG_TYPE "elfwriter"
34 #include "ELFWriter.h"
35 #include "ELFCodeEmitter.h"
36 #include "llvm/Constants.h"
37 #include "llvm/Module.h"
38 #include "llvm/PassManager.h"
39 #include "llvm/DerivedTypes.h"
40 #include "llvm/CodeGen/BinaryObject.h"
41 #include "llvm/CodeGen/FileWriters.h"
42 #include "llvm/CodeGen/MachineCodeEmitter.h"
43 #include "llvm/CodeGen/ObjectCodeEmitter.h"
44 #include "llvm/CodeGen/MachineCodeEmitter.h"
45 #include "llvm/CodeGen/MachineConstantPool.h"
46 #include "llvm/Target/TargetAsmInfo.h"
47 #include "llvm/Target/TargetData.h"
48 #include "llvm/Target/TargetELFWriterInfo.h"
49 #include "llvm/Target/TargetMachine.h"
50 #include "llvm/Support/Mangler.h"
51 #include "llvm/Support/Streams.h"
52 #include "llvm/Support/raw_ostream.h"
53 #include "llvm/Support/Debug.h"
54 #include "llvm/Support/ErrorHandling.h"
58 char ELFWriter::ID = 0;
60 /// AddELFWriter - Add the ELF writer to the function pass manager
61 ObjectCodeEmitter *llvm::AddELFWriter(PassManagerBase &PM,
64 ELFWriter *EW = new ELFWriter(O, TM);
66 return EW->getObjectCodeEmitter();
69 //===----------------------------------------------------------------------===//
70 // ELFWriter Implementation
71 //===----------------------------------------------------------------------===//
73 ELFWriter::ELFWriter(raw_ostream &o, TargetMachine &tm)
74 : MachineFunctionPass(&ID), O(o), TM(tm),
75 is64Bit(TM.getTargetData()->getPointerSizeInBits() == 64),
76 isLittleEndian(TM.getTargetData()->isLittleEndian()),
77 ElfHdr(isLittleEndian, is64Bit) {
79 TAI = TM.getTargetAsmInfo();
80 TEW = TM.getELFWriterInfo();
82 // Create the object code emitter object for this target.
83 ElfCE = new ELFCodeEmitter(*this);
85 // Inital number of sections
89 ELFWriter::~ELFWriter() {
93 // doInitialization - Emit the file header and all of the global variables for
94 // the module to the ELF file.
95 bool ELFWriter::doInitialization(Module &M) {
96 Mang = new Mangler(M);
100 // Fields e_shnum e_shstrndx are only known after all section have
101 // been emitted. They locations in the ouput buffer are recorded so
102 // to be patched up later.
106 // emitWord method behaves differently for ELF32 and ELF64, writing
107 // 4 bytes in the former and 8 in the last for *_off and *_addr elf types
109 ElfHdr.emitByte(0x7f); // e_ident[EI_MAG0]
110 ElfHdr.emitByte('E'); // e_ident[EI_MAG1]
111 ElfHdr.emitByte('L'); // e_ident[EI_MAG2]
112 ElfHdr.emitByte('F'); // e_ident[EI_MAG3]
114 ElfHdr.emitByte(TEW->getEIClass()); // e_ident[EI_CLASS]
115 ElfHdr.emitByte(TEW->getEIData()); // e_ident[EI_DATA]
116 ElfHdr.emitByte(EV_CURRENT); // e_ident[EI_VERSION]
117 ElfHdr.emitAlignment(16); // e_ident[EI_NIDENT-EI_PAD]
119 ElfHdr.emitWord16(ET_REL); // e_type
120 ElfHdr.emitWord16(TEW->getEMachine()); // e_machine = target
121 ElfHdr.emitWord32(EV_CURRENT); // e_version
122 ElfHdr.emitWord(0); // e_entry, no entry point in .o file
123 ElfHdr.emitWord(0); // e_phoff, no program header for .o
124 ELFHdr_e_shoff_Offset = ElfHdr.size();
125 ElfHdr.emitWord(0); // e_shoff = sec hdr table off in bytes
126 ElfHdr.emitWord32(TEW->getEFlags()); // e_flags = whatever the target wants
127 ElfHdr.emitWord16(TEW->getHdrSize()); // e_ehsize = ELF header size
128 ElfHdr.emitWord16(0); // e_phentsize = prog header entry size
129 ElfHdr.emitWord16(0); // e_phnum = # prog header entries = 0
131 // e_shentsize = Section header entry size
132 ElfHdr.emitWord16(TEW->getSHdrSize());
134 // e_shnum = # of section header ents
135 ELFHdr_e_shnum_Offset = ElfHdr.size();
136 ElfHdr.emitWord16(0); // Placeholder
138 // e_shstrndx = Section # of '.shstrtab'
139 ELFHdr_e_shstrndx_Offset = ElfHdr.size();
140 ElfHdr.emitWord16(0); // Placeholder
142 // Add the null section, which is required to be first in the file.
148 // getGlobalELFVisibility - Returns the ELF specific visibility type
149 unsigned ELFWriter::getGlobalELFVisibility(const GlobalValue *GV) {
150 switch (GV->getVisibility()) {
152 llvm_unreachable("unknown visibility type");
153 case GlobalValue::DefaultVisibility:
154 return ELFSym::STV_DEFAULT;
155 case GlobalValue::HiddenVisibility:
156 return ELFSym::STV_HIDDEN;
157 case GlobalValue::ProtectedVisibility:
158 return ELFSym::STV_PROTECTED;
163 // getGlobalELFBinding - Returns the ELF specific binding type
164 unsigned ELFWriter::getGlobalELFBinding(const GlobalValue *GV) {
165 if (GV->hasInternalLinkage())
166 return ELFSym::STB_LOCAL;
168 if (GV->hasWeakLinkage())
169 return ELFSym::STB_WEAK;
171 return ELFSym::STB_GLOBAL;
174 // getGlobalELFType - Returns the ELF specific type for a global
175 unsigned ELFWriter::getGlobalELFType(const GlobalValue *GV) {
176 if (GV->isDeclaration())
177 return ELFSym::STT_NOTYPE;
179 if (isa<Function>(GV))
180 return ELFSym::STT_FUNC;
182 return ELFSym::STT_OBJECT;
185 // getElfSectionFlags - Get the ELF Section Header flags based
186 // on the flags defined in ELFTargetAsmInfo.
187 unsigned ELFWriter::getElfSectionFlags(unsigned Flags) {
188 unsigned ElfSectionFlags = ELFSection::SHF_ALLOC;
190 if (Flags & SectionFlags::Code)
191 ElfSectionFlags |= ELFSection::SHF_EXECINSTR;
192 if (Flags & SectionFlags::Writeable)
193 ElfSectionFlags |= ELFSection::SHF_WRITE;
194 if (Flags & SectionFlags::Mergeable)
195 ElfSectionFlags |= ELFSection::SHF_MERGE;
196 if (Flags & SectionFlags::TLS)
197 ElfSectionFlags |= ELFSection::SHF_TLS;
198 if (Flags & SectionFlags::Strings)
199 ElfSectionFlags |= ELFSection::SHF_STRINGS;
201 return ElfSectionFlags;
204 // isELFUndefSym - the symbol has no section and must be placed in
205 // the symbol table with a reference to the null section.
206 static bool isELFUndefSym(const GlobalValue *GV) {
207 return GV->isDeclaration();
210 // isELFBssSym - for an undef or null value, the symbol must go to a bss
211 // section if it's not weak for linker, otherwise it's a common sym.
212 static bool isELFBssSym(const GlobalValue *GV) {
213 return (!GV->isDeclaration() &&
214 (GV->isNullValue() || isa<UndefValue>(GV)) &&
215 !GV->isWeakForLinker());
218 // isELFCommonSym - for an undef or null value, the symbol must go to a
219 // common section if it's weak for linker, otherwise bss.
220 static bool isELFCommonSym(const GlobalValue *GV) {
221 return (!GV->isDeclaration() &&
222 (GV->isNullValue() || isa<UndefValue>(GV))
223 && GV->isWeakForLinker());
226 // isELFDataSym - if the symbol is an initialized but no null constant
227 // it must go to some kind of data section gathered from TAI
228 static bool isELFDataSym(const GlobalValue *GV) {
229 return (!GV->isDeclaration() &&
230 !(GV->isNullValue() || isa<UndefValue>(GV)));
233 // EmitGlobal - Choose the right section for global and emit it
234 void ELFWriter::EmitGlobal(const GlobalValue *GV) {
236 // Handle ELF Bind, Visibility and Type for the current symbol
237 unsigned SymBind = getGlobalELFBinding(GV);
238 ELFSym *GblSym = new ELFSym(GV);
239 GblSym->setBind(SymBind);
240 GblSym->setVisibility(getGlobalELFVisibility(GV));
241 GblSym->setType(getGlobalELFType(GV));
243 if (isELFUndefSym(GV)) {
244 GblSym->SectionIdx = ELFSection::SHN_UNDEF;
246 assert(isa<GlobalVariable>(GV) && "GV not a global variable!");
247 const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV);
249 // Get ELF section from TAI
250 const Section *S = TAI->SectionForGlobal(GV);
251 unsigned SectionFlags = getElfSectionFlags(S->getFlags());
253 // The symbol align should update the section alignment if needed
254 const TargetData *TD = TM.getTargetData();
255 unsigned Align = TD->getPreferredAlignment(GVar);
256 unsigned Size = TD->getTypeAllocSize(GVar->getInitializer()->getType());
259 if (isELFCommonSym(GV)) {
260 GblSym->SectionIdx = ELFSection::SHN_COMMON;
261 getSection(S->getName(), ELFSection::SHT_NOBITS, SectionFlags, 1);
263 // A new linkonce section is created for each global in the
264 // common section, the default alignment is 1 and the symbol
265 // value contains its alignment.
266 GblSym->Value = Align;
268 } else if (isELFBssSym(GV)) {
270 getSection(S->getName(), ELFSection::SHT_NOBITS, SectionFlags);
271 GblSym->SectionIdx = ES.SectionIdx;
273 // Update the size with alignment and the next object can
274 // start in the right offset in the section
275 if (Align) ES.Size = (ES.Size + Align-1) & ~(Align-1);
276 ES.Align = std::max(ES.Align, Align);
278 // GblSym->Value should contain the virtual offset inside the section.
279 // Virtual because the BSS space is not allocated on ELF objects
280 GblSym->Value = ES.Size;
283 } else if (isELFDataSym(GV)) {
285 getSection(S->getName(), ELFSection::SHT_PROGBITS, SectionFlags);
286 GblSym->SectionIdx = ES.SectionIdx;
288 // GblSym->Value should contain the symbol offset inside the section,
289 // and all symbols should start on their required alignment boundary
290 ES.Align = std::max(ES.Align, Align);
291 GblSym->Value = (ES.size() + (Align-1)) & (-Align);
292 ES.emitAlignment(ES.Align);
294 // Emit the global to the data section 'ES'
295 EmitGlobalConstant(GVar->getInitializer(), ES);
299 // Private symbols must never go to the symbol table.
301 if (GV->hasPrivateLinkage()) {
302 PrivateSyms.push_back(GblSym);
303 SymIdx = PrivateSyms.size()-1;
305 SymbolList.push_back(GblSym);
308 GblSymLookup[GV] = SymIdx;
311 void ELFWriter::EmitGlobalConstantStruct(const ConstantStruct *CVS,
314 // Print the fields in successive locations. Pad to align if needed!
315 const TargetData *TD = TM.getTargetData();
316 unsigned Size = TD->getTypeAllocSize(CVS->getType());
317 const StructLayout *cvsLayout = TD->getStructLayout(CVS->getType());
318 uint64_t sizeSoFar = 0;
319 for (unsigned i = 0, e = CVS->getNumOperands(); i != e; ++i) {
320 const Constant* field = CVS->getOperand(i);
322 // Check if padding is needed and insert one or more 0s.
323 uint64_t fieldSize = TD->getTypeAllocSize(field->getType());
324 uint64_t padSize = ((i == e-1 ? Size : cvsLayout->getElementOffset(i+1))
325 - cvsLayout->getElementOffset(i)) - fieldSize;
326 sizeSoFar += fieldSize + padSize;
328 // Now print the actual field value.
329 EmitGlobalConstant(field, GblS);
331 // Insert padding - this may include padding to increase the size of the
332 // current field up to the ABI size (if the struct is not packed) as well
333 // as padding to ensure that the next field starts at the right offset.
334 for (unsigned p=0; p < padSize; p++)
337 assert(sizeSoFar == cvsLayout->getSizeInBytes() &&
338 "Layout of constant struct may be incorrect!");
341 void ELFWriter::EmitGlobalConstant(const Constant *CV, ELFSection &GblS) {
342 const TargetData *TD = TM.getTargetData();
343 unsigned Size = TD->getTypeAllocSize(CV->getType());
345 if (const ConstantArray *CVA = dyn_cast<ConstantArray>(CV)) {
346 if (CVA->isString()) {
347 std::string GblStr = CVA->getAsString();
348 GblStr.resize(GblStr.size()-1);
349 GblS.emitString(GblStr);
350 } else { // Not a string. Print the values in successive locations
351 for (unsigned i = 0, e = CVA->getNumOperands(); i != e; ++i)
352 EmitGlobalConstant(CVA->getOperand(i), GblS);
355 } else if (const ConstantStruct *CVS = dyn_cast<ConstantStruct>(CV)) {
356 EmitGlobalConstantStruct(CVS, GblS);
358 } else if (const ConstantFP *CFP = dyn_cast<ConstantFP>(CV)) {
359 uint64_t Val = CFP->getValueAPF().bitcastToAPInt().getZExtValue();
360 if (CFP->getType() == Type::DoubleTy)
361 GblS.emitWord64(Val);
362 else if (CFP->getType() == Type::FloatTy)
363 GblS.emitWord32(Val);
364 else if (CFP->getType() == Type::X86_FP80Ty) {
365 llvm_unreachable("X86_FP80Ty global emission not implemented");
366 } else if (CFP->getType() == Type::PPC_FP128Ty)
367 llvm_unreachable("PPC_FP128Ty global emission not implemented");
369 } else if (const ConstantInt *CI = dyn_cast<ConstantInt>(CV)) {
371 GblS.emitWord32(CI->getZExtValue());
373 GblS.emitWord64(CI->getZExtValue());
375 llvm_unreachable("LargeInt global emission not implemented");
377 } else if (const ConstantVector *CP = dyn_cast<ConstantVector>(CV)) {
378 const VectorType *PTy = CP->getType();
379 for (unsigned I = 0, E = PTy->getNumElements(); I < E; ++I)
380 EmitGlobalConstant(CP->getOperand(I), GblS);
383 llvm_unreachable("unknown global constant");
387 bool ELFWriter::runOnMachineFunction(MachineFunction &MF) {
388 // Nothing to do here, this is all done through the ElfCE object above.
392 /// doFinalization - Now that the module has been completely processed, emit
393 /// the ELF file to 'O'.
394 bool ELFWriter::doFinalization(Module &M) {
395 // Emit .data section placeholder
398 // Emit .bss section placeholder
401 // Build and emit data, bss and "common" sections.
402 for (Module::global_iterator I = M.global_begin(), E = M.global_end();
407 // Emit all pending globals
408 // TODO: this should be done only for referenced symbols
409 for (SetVector<GlobalValue*>::const_iterator I = PendingGlobals.begin(),
410 E = PendingGlobals.end(); I != E; ++I) {
411 // No need to emit the symbol again
412 if (GblSymLookup.find(*I) != GblSymLookup.end())
417 // Emit non-executable stack note
418 if (TAI->getNonexecutableStackDirective())
419 getNonExecStackSection();
421 // Emit a symbol for each section created until now, skip null section
422 for (unsigned i = 1, e = SectionList.size(); i < e; ++i) {
423 ELFSection &ES = *SectionList[i];
424 ELFSym *SectionSym = new ELFSym(0);
425 SectionSym->SectionIdx = ES.SectionIdx;
426 SectionSym->Size = 0;
427 SectionSym->setBind(ELFSym::STB_LOCAL);
428 SectionSym->setType(ELFSym::STT_SECTION);
429 SectionSym->setVisibility(ELFSym::STV_DEFAULT);
430 SymbolList.push_back(SectionSym);
431 ES.Sym = SymbolList.back();
437 // Emit the symbol table now, if non-empty.
440 // Emit the relocation sections.
443 // Emit the sections string table.
444 EmitSectionTableStringTable();
446 // Dump the sections and section table to the .o file.
447 OutputSectionsAndSectionTable();
449 // We are done with the abstract symbols.
454 // Release the name mangler object.
455 delete Mang; Mang = 0;
459 /// EmitRelocations - Emit relocations
460 void ELFWriter::EmitRelocations() {
462 // Create Relocation sections for each section which needs it.
463 for (unsigned i=0, e=SectionList.size(); i != e; ++i) {
464 ELFSection &S = *SectionList[i];
466 // This section does not have relocations
467 if (!S.hasRelocations()) continue;
469 // Get the relocation section for section 'S'
470 bool HasRelA = TEW->hasRelocationAddend();
471 ELFSection &RelSec = getRelocSection(S.getName(), HasRelA,
472 TEW->getPrefELFAlignment());
474 // 'Link' - Section hdr idx of the associated symbol table
475 // 'Info' - Section hdr idx of the section to which the relocation applies
476 ELFSection &SymTab = getSymbolTableSection();
477 RelSec.Link = SymTab.SectionIdx;
478 RelSec.Info = S.SectionIdx;
479 RelSec.EntSize = TEW->getRelocationEntrySize();
481 // Get the relocations from Section
482 std::vector<MachineRelocation> Relos = S.getRelocations();
483 for (std::vector<MachineRelocation>::iterator MRI = Relos.begin(),
484 MRE = Relos.end(); MRI != MRE; ++MRI) {
485 MachineRelocation &MR = *MRI;
487 // Holds the relocatable field address as an offset from the
488 // beginning of the section where it lives
489 unsigned Offset = MR.getMachineCodeOffset();
491 // Symbol index in the symbol table
494 // Target specific ELF relocation type
495 unsigned RelType = TEW->getRelocationType(MR.getRelocationType());
497 // Constant addend used to compute the value to be stored
498 // into the relocatable field
501 // There are several machine relocations types, and each one of
502 // them needs a different approach to retrieve the symbol table index.
503 if (MR.isGlobalValue()) {
504 const GlobalValue *G = MR.getGlobalValue();
505 SymIdx = GblSymLookup[G];
506 if (G->hasPrivateLinkage()) {
507 // If the target uses a section offset in the relocation:
508 // SymIdx + Addend = section sym for global + section offset
509 unsigned SectionIdx = PrivateSyms[SymIdx]->SectionIdx;
510 Addend = PrivateSyms[SymIdx]->Value;
511 SymIdx = SectionList[SectionIdx]->getSymbolTableIndex();
513 Addend = TEW->getDefaultAddendForRelTy(RelType);
516 // Get the symbol index for the section symbol referenced
518 unsigned SectionIdx = MR.getConstantVal();
519 SymIdx = SectionList[SectionIdx]->getSymbolTableIndex();
520 Addend = (uint64_t)MR.getResultPointer();
523 // The target without addend on the relocation symbol must be
524 // patched in the relocation place itself to contain the addend
526 if (TEW->getRelocationTySize(RelType) == 32)
527 S.fixWord32(Addend, Offset);
528 else if (TEW->getRelocationTySize(RelType) == 64)
529 S.fixWord64(Addend, Offset);
531 llvm_unreachable("don't know howto patch relocatable field");
534 // Get the relocation entry and emit to the relocation section
535 ELFRelocation Rel(Offset, SymIdx, RelType, HasRelA, Addend);
536 EmitRelocation(RelSec, Rel, HasRelA);
541 /// EmitRelocation - Write relocation 'Rel' to the relocation section 'Rel'
542 void ELFWriter::EmitRelocation(BinaryObject &RelSec, ELFRelocation &Rel,
544 RelSec.emitWord(Rel.getOffset());
545 RelSec.emitWord(Rel.getInfo(is64Bit));
547 RelSec.emitWord(Rel.getAddend());
550 /// EmitSymbol - Write symbol 'Sym' to the symbol table 'SymbolTable'
551 void ELFWriter::EmitSymbol(BinaryObject &SymbolTable, ELFSym &Sym) {
553 SymbolTable.emitWord32(Sym.NameIdx);
554 SymbolTable.emitByte(Sym.Info);
555 SymbolTable.emitByte(Sym.Other);
556 SymbolTable.emitWord16(Sym.SectionIdx);
557 SymbolTable.emitWord64(Sym.Value);
558 SymbolTable.emitWord64(Sym.Size);
560 SymbolTable.emitWord32(Sym.NameIdx);
561 SymbolTable.emitWord32(Sym.Value);
562 SymbolTable.emitWord32(Sym.Size);
563 SymbolTable.emitByte(Sym.Info);
564 SymbolTable.emitByte(Sym.Other);
565 SymbolTable.emitWord16(Sym.SectionIdx);
569 /// EmitSectionHeader - Write section 'Section' header in 'SHdrTab'
570 /// Section Header Table
571 void ELFWriter::EmitSectionHeader(BinaryObject &SHdrTab,
572 const ELFSection &SHdr) {
573 SHdrTab.emitWord32(SHdr.NameIdx);
574 SHdrTab.emitWord32(SHdr.Type);
576 SHdrTab.emitWord64(SHdr.Flags);
577 SHdrTab.emitWord(SHdr.Addr);
578 SHdrTab.emitWord(SHdr.Offset);
579 SHdrTab.emitWord64(SHdr.Size);
580 SHdrTab.emitWord32(SHdr.Link);
581 SHdrTab.emitWord32(SHdr.Info);
582 SHdrTab.emitWord64(SHdr.Align);
583 SHdrTab.emitWord64(SHdr.EntSize);
585 SHdrTab.emitWord32(SHdr.Flags);
586 SHdrTab.emitWord(SHdr.Addr);
587 SHdrTab.emitWord(SHdr.Offset);
588 SHdrTab.emitWord32(SHdr.Size);
589 SHdrTab.emitWord32(SHdr.Link);
590 SHdrTab.emitWord32(SHdr.Info);
591 SHdrTab.emitWord32(SHdr.Align);
592 SHdrTab.emitWord32(SHdr.EntSize);
596 /// EmitStringTable - If the current symbol table is non-empty, emit the string
598 void ELFWriter::EmitStringTable() {
599 if (!SymbolList.size()) return; // Empty symbol table.
600 ELFSection &StrTab = getStringTableSection();
602 // Set the zero'th symbol to a null byte, as required.
605 // Walk on the symbol list and write symbol names into the string table.
607 for (ELFSymIter I=SymbolList.begin(), E=SymbolList.end(); I != E; ++I) {
610 // Use the name mangler to uniquify the LLVM symbol.
612 if (Sym.GV) Name.append(Mang->getMangledName(Sym.GV));
618 StrTab.emitString(Name);
620 // Keep track of the number of bytes emitted to this section.
621 Index += Name.size()+1;
624 assert(Index == StrTab.size());
628 // SortSymbols - On the symbol table local symbols must come before
629 // all other symbols with non-local bindings. The return value is
630 // the position of the first non local symbol.
631 unsigned ELFWriter::SortSymbols() {
632 unsigned FirstNonLocalSymbol;
633 std::vector<ELFSym*> LocalSyms, OtherSyms;
635 for (ELFSymIter I=SymbolList.begin(), E=SymbolList.end(); I != E; ++I) {
636 if ((*I)->isLocalBind())
637 LocalSyms.push_back(*I);
639 OtherSyms.push_back(*I);
642 FirstNonLocalSymbol = LocalSyms.size();
644 for (unsigned i = 0; i < FirstNonLocalSymbol; ++i)
645 SymbolList.push_back(LocalSyms[i]);
647 for (ELFSymIter I=OtherSyms.begin(), E=OtherSyms.end(); I != E; ++I)
648 SymbolList.push_back(*I);
653 return FirstNonLocalSymbol;
656 /// EmitSymbolTable - Emit the symbol table itself.
657 void ELFWriter::EmitSymbolTable() {
658 if (!SymbolList.size()) return; // Empty symbol table.
660 // Now that we have emitted the string table and know the offset into the
661 // string table of each symbol, emit the symbol table itself.
662 ELFSection &SymTab = getSymbolTableSection();
663 SymTab.Align = TEW->getPrefELFAlignment();
665 // Section Index of .strtab.
666 SymTab.Link = getStringTableSection().SectionIdx;
668 // Size of each symtab entry.
669 SymTab.EntSize = TEW->getSymTabEntrySize();
671 // The first entry in the symtab is the null symbol
672 SymbolList.insert(SymbolList.begin(), new ELFSym(0));
674 // Reorder the symbol table with local symbols first!
675 unsigned FirstNonLocalSymbol = SortSymbols();
677 // Emit all the symbols to the symbol table.
678 for (unsigned i = 0, e = SymbolList.size(); i < e; ++i) {
679 ELFSym &Sym = *SymbolList[i];
681 // Emit symbol to the symbol table
682 EmitSymbol(SymTab, Sym);
684 // Record the symbol table index for each global value
685 if (Sym.GV) GblSymLookup[Sym.GV] = i;
687 // Keep track on the symbol index into the symbol table
691 // One greater than the symbol table index of the last local symbol
692 SymTab.Info = FirstNonLocalSymbol;
693 SymTab.Size = SymTab.size();
696 /// EmitSectionTableStringTable - This method adds and emits a section for the
697 /// ELF Section Table string table: the string table that holds all of the
699 void ELFWriter::EmitSectionTableStringTable() {
700 // First step: add the section for the string table to the list of sections:
701 ELFSection &SHStrTab = getSectionHeaderStringTableSection();
703 // Now that we know which section number is the .shstrtab section, update the
704 // e_shstrndx entry in the ELF header.
705 ElfHdr.fixWord16(SHStrTab.SectionIdx, ELFHdr_e_shstrndx_Offset);
707 // Set the NameIdx of each section in the string table and emit the bytes for
711 for (ELFSectionIter I=SectionList.begin(), E=SectionList.end(); I != E; ++I) {
712 ELFSection &S = *(*I);
713 // Set the index into the table. Note if we have lots of entries with
714 // common suffixes, we could memoize them here if we cared.
716 SHStrTab.emitString(S.getName());
718 // Keep track of the number of bytes emitted to this section.
719 Index += S.getName().size()+1;
722 // Set the size of .shstrtab now that we know what it is.
723 assert(Index == SHStrTab.size());
724 SHStrTab.Size = Index;
727 /// OutputSectionsAndSectionTable - Now that we have constructed the file header
728 /// and all of the sections, emit these to the ostream destination and emit the
730 void ELFWriter::OutputSectionsAndSectionTable() {
731 // Pass #1: Compute the file offset for each section.
732 size_t FileOff = ElfHdr.size(); // File header first.
734 // Adjust alignment of all section if needed, skip the null section.
735 for (unsigned i=1, e=SectionList.size(); i < e; ++i) {
736 ELFSection &ES = *SectionList[i];
742 // Update Section size
746 // Align FileOff to whatever the alignment restrictions of the section are.
748 FileOff = (FileOff+ES.Align-1) & ~(ES.Align-1);
754 // Align Section Header.
755 unsigned TableAlign = TEW->getPrefELFAlignment();
756 FileOff = (FileOff+TableAlign-1) & ~(TableAlign-1);
758 // Now that we know where all of the sections will be emitted, set the e_shnum
759 // entry in the ELF header.
760 ElfHdr.fixWord16(NumSections, ELFHdr_e_shnum_Offset);
762 // Now that we know the offset in the file of the section table, update the
763 // e_shoff address in the ELF header.
764 ElfHdr.fixWord(FileOff, ELFHdr_e_shoff_Offset);
766 // Now that we know all of the data in the file header, emit it and all of the
768 O.write((char *)&ElfHdr.getData()[0], ElfHdr.size());
769 FileOff = ElfHdr.size();
771 // Section Header Table blob
772 BinaryObject SHdrTable(isLittleEndian, is64Bit);
774 // Emit all of sections to the file and build the section header table.
775 for (ELFSectionIter I=SectionList.begin(), E=SectionList.end(); I != E; ++I) {
776 ELFSection &S = *(*I);
777 DOUT << "SectionIdx: " << S.SectionIdx << ", Name: " << S.getName()
778 << ", Size: " << S.Size << ", Offset: " << S.Offset
779 << ", SectionData Size: " << S.size() << "\n";
781 // Align FileOff to whatever the alignment restrictions of the section are.
784 for (size_t NewFileOff = (FileOff+S.Align-1) & ~(S.Align-1);
785 FileOff != NewFileOff; ++FileOff)
788 O.write((char *)&S.getData()[0], S.Size);
792 EmitSectionHeader(SHdrTable, S);
795 // Align output for the section table.
796 for (size_t NewFileOff = (FileOff+TableAlign-1) & ~(TableAlign-1);
797 FileOff != NewFileOff; ++FileOff)
800 // Emit the section table itself.
801 O.write((char *)&SHdrTable.getData()[0], SHdrTable.size());