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 // Get jump table section on the section name returned by TAI
149 ELFSection &ELFWriter::getJumpTableSection() {
150 unsigned Align = TM.getTargetData()->getPointerABIAlignment();
151 return getSection(TAI->getJumpTableDataSection(),
152 ELFSection::SHT_PROGBITS,
153 ELFSection::SHF_ALLOC, Align);
156 // Get a constant pool section based on the section name returned by TAI
157 ELFSection &ELFWriter::getConstantPoolSection(MachineConstantPoolEntry &CPE) {
158 std::string CstPoolName =
159 TAI->SelectSectionForMachineConst(CPE.getType())->getName();
160 return getSection(CstPoolName,
161 ELFSection::SHT_PROGBITS,
162 ELFSection::SHF_MERGE | ELFSection::SHF_ALLOC,
166 // Return the relocation section of section 'S'. 'RelA' is true
167 // if the relocation section contains entries with addends.
168 ELFSection &ELFWriter::getRelocSection(ELFSection &S) {
169 unsigned SectionHeaderTy = TEW->hasRelocationAddend() ?
170 ELFSection::SHT_RELA : ELFSection::SHT_REL;
171 std::string RelSName(".rel");
172 if (TEW->hasRelocationAddend())
173 RelSName.append("a");
174 RelSName.append(S.getName());
176 return getSection(RelSName, SectionHeaderTy, 0, TEW->getPrefELFAlignment());
179 // getGlobalELFVisibility - Returns the ELF specific visibility type
180 unsigned ELFWriter::getGlobalELFVisibility(const GlobalValue *GV) {
181 switch (GV->getVisibility()) {
183 llvm_unreachable("unknown visibility type");
184 case GlobalValue::DefaultVisibility:
185 return ELFSym::STV_DEFAULT;
186 case GlobalValue::HiddenVisibility:
187 return ELFSym::STV_HIDDEN;
188 case GlobalValue::ProtectedVisibility:
189 return ELFSym::STV_PROTECTED;
194 // getGlobalELFBinding - Returns the ELF specific binding type
195 unsigned ELFWriter::getGlobalELFBinding(const GlobalValue *GV) {
196 if (GV->hasInternalLinkage())
197 return ELFSym::STB_LOCAL;
199 if (GV->hasWeakLinkage())
200 return ELFSym::STB_WEAK;
202 return ELFSym::STB_GLOBAL;
205 // getGlobalELFType - Returns the ELF specific type for a global
206 unsigned ELFWriter::getGlobalELFType(const GlobalValue *GV) {
207 if (GV->isDeclaration())
208 return ELFSym::STT_NOTYPE;
210 if (isa<Function>(GV))
211 return ELFSym::STT_FUNC;
213 return ELFSym::STT_OBJECT;
216 // getElfSectionFlags - Get the ELF Section Header flags based
217 // on the flags defined in ELFTargetAsmInfo.
218 unsigned ELFWriter::getElfSectionFlags(unsigned Flags) {
219 unsigned ElfSectionFlags = ELFSection::SHF_ALLOC;
221 if (Flags & SectionFlags::Code)
222 ElfSectionFlags |= ELFSection::SHF_EXECINSTR;
223 if (Flags & SectionFlags::Writeable)
224 ElfSectionFlags |= ELFSection::SHF_WRITE;
225 if (Flags & SectionFlags::Mergeable)
226 ElfSectionFlags |= ELFSection::SHF_MERGE;
227 if (Flags & SectionFlags::TLS)
228 ElfSectionFlags |= ELFSection::SHF_TLS;
229 if (Flags & SectionFlags::Strings)
230 ElfSectionFlags |= ELFSection::SHF_STRINGS;
232 return ElfSectionFlags;
235 // isELFUndefSym - the symbol has no section and must be placed in
236 // the symbol table with a reference to the null section.
237 static bool isELFUndefSym(const GlobalValue *GV) {
238 return GV->isDeclaration();
241 // isELFBssSym - for an undef or null value, the symbol must go to a bss
242 // section if it's not weak for linker, otherwise it's a common sym.
243 static bool isELFBssSym(const GlobalValue *GV) {
244 return (!GV->isDeclaration() &&
245 (GV->isNullValue() || isa<UndefValue>(GV)) &&
246 !GV->isWeakForLinker());
249 // isELFCommonSym - for an undef or null value, the symbol must go to a
250 // common section if it's weak for linker, otherwise bss.
251 static bool isELFCommonSym(const GlobalValue *GV) {
252 return (!GV->isDeclaration() &&
253 (GV->isNullValue() || isa<UndefValue>(GV))
254 && GV->isWeakForLinker());
257 // isELFDataSym - if the symbol is an initialized but no null constant
258 // it must go to some kind of data section gathered from TAI
259 static bool isELFDataSym(const GlobalValue *GV) {
260 return (!GV->isDeclaration() &&
261 !(GV->isNullValue() || isa<UndefValue>(GV)));
264 // EmitGlobal - Choose the right section for global and emit it
265 void ELFWriter::EmitGlobal(const GlobalValue *GV) {
267 // Handle ELF Bind, Visibility and Type for the current symbol
268 unsigned SymBind = getGlobalELFBinding(GV);
269 ELFSym *GblSym = new ELFSym(GV);
270 GblSym->setBind(SymBind);
271 GblSym->setVisibility(getGlobalELFVisibility(GV));
272 GblSym->setType(getGlobalELFType(GV));
274 if (isELFUndefSym(GV)) {
275 GblSym->SectionIdx = ELFSection::SHN_UNDEF;
277 assert(isa<GlobalVariable>(GV) && "GV not a global variable!");
278 const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV);
280 // Get ELF section from TAI
281 const Section *S = TAI->SectionForGlobal(GV);
282 unsigned SectionFlags = getElfSectionFlags(S->getFlags());
284 // The symbol align should update the section alignment if needed
285 const TargetData *TD = TM.getTargetData();
286 unsigned Align = TD->getPreferredAlignment(GVar);
287 unsigned Size = TD->getTypeAllocSize(GVar->getInitializer()->getType());
290 if (isELFCommonSym(GV)) {
291 GblSym->SectionIdx = ELFSection::SHN_COMMON;
292 getSection(S->getName(), ELFSection::SHT_NOBITS, SectionFlags, 1);
294 // A new linkonce section is created for each global in the
295 // common section, the default alignment is 1 and the symbol
296 // value contains its alignment.
297 GblSym->Value = Align;
299 } else if (isELFBssSym(GV)) {
301 getSection(S->getName(), ELFSection::SHT_NOBITS, SectionFlags);
302 GblSym->SectionIdx = ES.SectionIdx;
304 // Update the size with alignment and the next object can
305 // start in the right offset in the section
306 if (Align) ES.Size = (ES.Size + Align-1) & ~(Align-1);
307 ES.Align = std::max(ES.Align, Align);
309 // GblSym->Value should contain the virtual offset inside the section.
310 // Virtual because the BSS space is not allocated on ELF objects
311 GblSym->Value = ES.Size;
314 } else if (isELFDataSym(GV)) {
316 getSection(S->getName(), ELFSection::SHT_PROGBITS, SectionFlags);
317 GblSym->SectionIdx = ES.SectionIdx;
319 // GblSym->Value should contain the symbol offset inside the section,
320 // and all symbols should start on their required alignment boundary
321 ES.Align = std::max(ES.Align, Align);
322 GblSym->Value = (ES.size() + (Align-1)) & (-Align);
323 ES.emitAlignment(ES.Align);
325 // Emit the global to the data section 'ES'
326 EmitGlobalConstant(GVar->getInitializer(), ES);
330 // Private symbols must never go to the symbol table.
332 if (GV->hasPrivateLinkage()) {
333 PrivateSyms.push_back(GblSym);
334 SymIdx = PrivateSyms.size()-1;
336 SymbolList.push_back(GblSym);
339 GblSymLookup[GV] = SymIdx;
342 void ELFWriter::EmitGlobalConstantStruct(const ConstantStruct *CVS,
345 // Print the fields in successive locations. Pad to align if needed!
346 const TargetData *TD = TM.getTargetData();
347 unsigned Size = TD->getTypeAllocSize(CVS->getType());
348 const StructLayout *cvsLayout = TD->getStructLayout(CVS->getType());
349 uint64_t sizeSoFar = 0;
350 for (unsigned i = 0, e = CVS->getNumOperands(); i != e; ++i) {
351 const Constant* field = CVS->getOperand(i);
353 // Check if padding is needed and insert one or more 0s.
354 uint64_t fieldSize = TD->getTypeAllocSize(field->getType());
355 uint64_t padSize = ((i == e-1 ? Size : cvsLayout->getElementOffset(i+1))
356 - cvsLayout->getElementOffset(i)) - fieldSize;
357 sizeSoFar += fieldSize + padSize;
359 // Now print the actual field value.
360 EmitGlobalConstant(field, GblS);
362 // Insert padding - this may include padding to increase the size of the
363 // current field up to the ABI size (if the struct is not packed) as well
364 // as padding to ensure that the next field starts at the right offset.
365 for (unsigned p=0; p < padSize; p++)
368 assert(sizeSoFar == cvsLayout->getSizeInBytes() &&
369 "Layout of constant struct may be incorrect!");
372 void ELFWriter::EmitGlobalConstant(const Constant *CV, ELFSection &GblS) {
373 const TargetData *TD = TM.getTargetData();
374 unsigned Size = TD->getTypeAllocSize(CV->getType());
376 if (const ConstantArray *CVA = dyn_cast<ConstantArray>(CV)) {
377 if (CVA->isString()) {
378 std::string GblStr = CVA->getAsString();
379 GblStr.resize(GblStr.size()-1);
380 GblS.emitString(GblStr);
381 } else { // Not a string. Print the values in successive locations
382 for (unsigned i = 0, e = CVA->getNumOperands(); i != e; ++i)
383 EmitGlobalConstant(CVA->getOperand(i), GblS);
386 } else if (const ConstantStruct *CVS = dyn_cast<ConstantStruct>(CV)) {
387 EmitGlobalConstantStruct(CVS, GblS);
389 } else if (const ConstantFP *CFP = dyn_cast<ConstantFP>(CV)) {
390 uint64_t Val = CFP->getValueAPF().bitcastToAPInt().getZExtValue();
391 if (CFP->getType() == Type::DoubleTy)
392 GblS.emitWord64(Val);
393 else if (CFP->getType() == Type::FloatTy)
394 GblS.emitWord32(Val);
395 else if (CFP->getType() == Type::X86_FP80Ty) {
396 llvm_unreachable("X86_FP80Ty global emission not implemented");
397 } else if (CFP->getType() == Type::PPC_FP128Ty)
398 llvm_unreachable("PPC_FP128Ty global emission not implemented");
400 } else if (const ConstantInt *CI = dyn_cast<ConstantInt>(CV)) {
402 GblS.emitWord32(CI->getZExtValue());
404 GblS.emitWord64(CI->getZExtValue());
406 llvm_unreachable("LargeInt global emission not implemented");
408 } else if (const ConstantVector *CP = dyn_cast<ConstantVector>(CV)) {
409 const VectorType *PTy = CP->getType();
410 for (unsigned I = 0, E = PTy->getNumElements(); I < E; ++I)
411 EmitGlobalConstant(CP->getOperand(I), GblS);
414 llvm_unreachable("unknown global constant");
418 bool ELFWriter::runOnMachineFunction(MachineFunction &MF) {
419 // Nothing to do here, this is all done through the ElfCE object above.
423 /// doFinalization - Now that the module has been completely processed, emit
424 /// the ELF file to 'O'.
425 bool ELFWriter::doFinalization(Module &M) {
426 // Emit .data section placeholder
429 // Emit .bss section placeholder
432 // Build and emit data, bss and "common" sections.
433 for (Module::global_iterator I = M.global_begin(), E = M.global_end();
438 // Emit all pending globals
439 // TODO: this should be done only for referenced symbols
440 for (SetVector<GlobalValue*>::const_iterator I = PendingGlobals.begin(),
441 E = PendingGlobals.end(); I != E; ++I) {
442 // No need to emit the symbol again
443 if (GblSymLookup.find(*I) != GblSymLookup.end())
448 // Emit non-executable stack note
449 if (TAI->getNonexecutableStackDirective())
450 getNonExecStackSection();
452 // Emit a symbol for each section created until now, skip null section
453 for (unsigned i = 1, e = SectionList.size(); i < e; ++i) {
454 ELFSection &ES = *SectionList[i];
455 ELFSym *SectionSym = new ELFSym(0);
456 SectionSym->SectionIdx = ES.SectionIdx;
457 SectionSym->Size = 0;
458 SectionSym->setBind(ELFSym::STB_LOCAL);
459 SectionSym->setType(ELFSym::STT_SECTION);
460 SectionSym->setVisibility(ELFSym::STV_DEFAULT);
461 SymbolList.push_back(SectionSym);
462 ES.Sym = SymbolList.back();
468 // Emit the symbol table now, if non-empty.
471 // Emit the relocation sections.
474 // Emit the sections string table.
475 EmitSectionTableStringTable();
477 // Dump the sections and section table to the .o file.
478 OutputSectionsAndSectionTable();
480 // We are done with the abstract symbols.
485 // Release the name mangler object.
486 delete Mang; Mang = 0;
490 // RelocateField - Patch relocatable field with 'Offset' in 'BO'
491 // using a 'Value' of known 'Size'
492 void ELFWriter::RelocateField(BinaryObject &BO, uint32_t Offset,
493 int64_t Value, unsigned Size) {
495 BO.fixWord32(Value, Offset);
497 BO.fixWord64(Value, Offset);
499 llvm_unreachable("don't know howto patch relocatable field");
502 /// EmitRelocations - Emit relocations
503 void ELFWriter::EmitRelocations() {
505 // True if the target uses the relocation entry to hold the addend,
506 // otherwise the addend is written directly to the relocatable field.
507 bool HasRelA = TEW->hasRelocationAddend();
509 // Create Relocation sections for each section which needs it.
510 for (unsigned i=0, e=SectionList.size(); i != e; ++i) {
511 ELFSection &S = *SectionList[i];
513 // This section does not have relocations
514 if (!S.hasRelocations()) continue;
515 ELFSection &RelSec = getRelocSection(S);
517 // 'Link' - Section hdr idx of the associated symbol table
518 // 'Info' - Section hdr idx of the section to which the relocation applies
519 ELFSection &SymTab = getSymbolTableSection();
520 RelSec.Link = SymTab.SectionIdx;
521 RelSec.Info = S.SectionIdx;
522 RelSec.EntSize = TEW->getRelocationEntrySize();
524 // Get the relocations from Section
525 std::vector<MachineRelocation> Relos = S.getRelocations();
526 for (std::vector<MachineRelocation>::iterator MRI = Relos.begin(),
527 MRE = Relos.end(); MRI != MRE; ++MRI) {
528 MachineRelocation &MR = *MRI;
530 // Relocatable field offset from the section start
531 unsigned RelOffset = MR.getMachineCodeOffset();
533 // Symbol index in the symbol table
536 // Target specific relocation field type and size
537 unsigned RelType = TEW->getRelocationType(MR.getRelocationType());
538 unsigned RelTySize = TEW->getRelocationTySize(RelType);
541 // There are several machine relocations types, and each one of
542 // them needs a different approach to retrieve the symbol table index.
543 if (MR.isGlobalValue()) {
544 const GlobalValue *G = MR.getGlobalValue();
545 SymIdx = GblSymLookup[G];
546 if (G->hasPrivateLinkage()) {
547 // If the target uses a section offset in the relocation:
548 // SymIdx + Addend = section sym for global + section offset
549 unsigned SectionIdx = PrivateSyms[SymIdx]->SectionIdx;
550 Addend = PrivateSyms[SymIdx]->Value;
551 SymIdx = SectionList[SectionIdx]->getSymbolTableIndex();
553 Addend = TEW->getDefaultAddendForRelTy(RelType);
556 // Get the symbol index for the section symbol
557 unsigned SectionIdx = MR.getConstantVal();
558 SymIdx = SectionList[SectionIdx]->getSymbolTableIndex();
559 Addend = (uint64_t)MR.getResultPointer();
561 // For pc relative relocations where symbols are defined in the same
562 // section they are referenced, ignore the relocation entry and patch
563 // the relocatable field with the symbol offset directly.
564 if (S.SectionIdx == SectionIdx && TEW->isPCRelativeRel(RelType)) {
565 int64_t Value = TEW->computeRelocation(Addend, RelOffset, RelType);
566 RelocateField(S, RelOffset, Value, RelTySize);
570 // Handle Jump Table Index relocation
571 if ((SectionIdx == getJumpTableSection().SectionIdx) &&
572 TEW->hasCustomJumpTableIndexRelTy()) {
573 RelType = TEW->getJumpTableIndexRelTy();
574 RelTySize = TEW->getRelocationTySize(RelType);
578 // The target without addend on the relocation symbol must be
579 // patched in the relocation place itself to contain the addend
581 RelocateField(S, RelOffset, Addend, RelTySize);
583 // Get the relocation entry and emit to the relocation section
584 ELFRelocation Rel(RelOffset, SymIdx, RelType, HasRelA, Addend);
585 EmitRelocation(RelSec, Rel, HasRelA);
590 /// EmitRelocation - Write relocation 'Rel' to the relocation section 'Rel'
591 void ELFWriter::EmitRelocation(BinaryObject &RelSec, ELFRelocation &Rel,
593 RelSec.emitWord(Rel.getOffset());
594 RelSec.emitWord(Rel.getInfo(is64Bit));
596 RelSec.emitWord(Rel.getAddend());
599 /// EmitSymbol - Write symbol 'Sym' to the symbol table 'SymbolTable'
600 void ELFWriter::EmitSymbol(BinaryObject &SymbolTable, ELFSym &Sym) {
602 SymbolTable.emitWord32(Sym.NameIdx);
603 SymbolTable.emitByte(Sym.Info);
604 SymbolTable.emitByte(Sym.Other);
605 SymbolTable.emitWord16(Sym.SectionIdx);
606 SymbolTable.emitWord64(Sym.Value);
607 SymbolTable.emitWord64(Sym.Size);
609 SymbolTable.emitWord32(Sym.NameIdx);
610 SymbolTable.emitWord32(Sym.Value);
611 SymbolTable.emitWord32(Sym.Size);
612 SymbolTable.emitByte(Sym.Info);
613 SymbolTable.emitByte(Sym.Other);
614 SymbolTable.emitWord16(Sym.SectionIdx);
618 /// EmitSectionHeader - Write section 'Section' header in 'SHdrTab'
619 /// Section Header Table
620 void ELFWriter::EmitSectionHeader(BinaryObject &SHdrTab,
621 const ELFSection &SHdr) {
622 SHdrTab.emitWord32(SHdr.NameIdx);
623 SHdrTab.emitWord32(SHdr.Type);
625 SHdrTab.emitWord64(SHdr.Flags);
626 SHdrTab.emitWord(SHdr.Addr);
627 SHdrTab.emitWord(SHdr.Offset);
628 SHdrTab.emitWord64(SHdr.Size);
629 SHdrTab.emitWord32(SHdr.Link);
630 SHdrTab.emitWord32(SHdr.Info);
631 SHdrTab.emitWord64(SHdr.Align);
632 SHdrTab.emitWord64(SHdr.EntSize);
634 SHdrTab.emitWord32(SHdr.Flags);
635 SHdrTab.emitWord(SHdr.Addr);
636 SHdrTab.emitWord(SHdr.Offset);
637 SHdrTab.emitWord32(SHdr.Size);
638 SHdrTab.emitWord32(SHdr.Link);
639 SHdrTab.emitWord32(SHdr.Info);
640 SHdrTab.emitWord32(SHdr.Align);
641 SHdrTab.emitWord32(SHdr.EntSize);
645 /// EmitStringTable - If the current symbol table is non-empty, emit the string
647 void ELFWriter::EmitStringTable() {
648 if (!SymbolList.size()) return; // Empty symbol table.
649 ELFSection &StrTab = getStringTableSection();
651 // Set the zero'th symbol to a null byte, as required.
654 // Walk on the symbol list and write symbol names into the string table.
656 for (ELFSymIter I=SymbolList.begin(), E=SymbolList.end(); I != E; ++I) {
659 // Use the name mangler to uniquify the LLVM symbol.
661 if (Sym.GV) Name.append(Mang->getMangledName(Sym.GV));
667 StrTab.emitString(Name);
669 // Keep track of the number of bytes emitted to this section.
670 Index += Name.size()+1;
673 assert(Index == StrTab.size());
677 // SortSymbols - On the symbol table local symbols must come before
678 // all other symbols with non-local bindings. The return value is
679 // the position of the first non local symbol.
680 unsigned ELFWriter::SortSymbols() {
681 unsigned FirstNonLocalSymbol;
682 std::vector<ELFSym*> LocalSyms, OtherSyms;
684 for (ELFSymIter I=SymbolList.begin(), E=SymbolList.end(); I != E; ++I) {
685 if ((*I)->isLocalBind())
686 LocalSyms.push_back(*I);
688 OtherSyms.push_back(*I);
691 FirstNonLocalSymbol = LocalSyms.size();
693 for (unsigned i = 0; i < FirstNonLocalSymbol; ++i)
694 SymbolList.push_back(LocalSyms[i]);
696 for (ELFSymIter I=OtherSyms.begin(), E=OtherSyms.end(); I != E; ++I)
697 SymbolList.push_back(*I);
702 return FirstNonLocalSymbol;
705 /// EmitSymbolTable - Emit the symbol table itself.
706 void ELFWriter::EmitSymbolTable() {
707 if (!SymbolList.size()) return; // Empty symbol table.
709 // Now that we have emitted the string table and know the offset into the
710 // string table of each symbol, emit the symbol table itself.
711 ELFSection &SymTab = getSymbolTableSection();
712 SymTab.Align = TEW->getPrefELFAlignment();
714 // Section Index of .strtab.
715 SymTab.Link = getStringTableSection().SectionIdx;
717 // Size of each symtab entry.
718 SymTab.EntSize = TEW->getSymTabEntrySize();
720 // The first entry in the symtab is the null symbol
721 SymbolList.insert(SymbolList.begin(), new ELFSym(0));
723 // Reorder the symbol table with local symbols first!
724 unsigned FirstNonLocalSymbol = SortSymbols();
726 // Emit all the symbols to the symbol table.
727 for (unsigned i = 0, e = SymbolList.size(); i < e; ++i) {
728 ELFSym &Sym = *SymbolList[i];
730 // Emit symbol to the symbol table
731 EmitSymbol(SymTab, Sym);
733 // Record the symbol table index for each global value
734 if (Sym.GV) GblSymLookup[Sym.GV] = i;
736 // Keep track on the symbol index into the symbol table
740 // One greater than the symbol table index of the last local symbol
741 SymTab.Info = FirstNonLocalSymbol;
742 SymTab.Size = SymTab.size();
745 /// EmitSectionTableStringTable - This method adds and emits a section for the
746 /// ELF Section Table string table: the string table that holds all of the
748 void ELFWriter::EmitSectionTableStringTable() {
749 // First step: add the section for the string table to the list of sections:
750 ELFSection &SHStrTab = getSectionHeaderStringTableSection();
752 // Now that we know which section number is the .shstrtab section, update the
753 // e_shstrndx entry in the ELF header.
754 ElfHdr.fixWord16(SHStrTab.SectionIdx, ELFHdr_e_shstrndx_Offset);
756 // Set the NameIdx of each section in the string table and emit the bytes for
760 for (ELFSectionIter I=SectionList.begin(), E=SectionList.end(); I != E; ++I) {
761 ELFSection &S = *(*I);
762 // Set the index into the table. Note if we have lots of entries with
763 // common suffixes, we could memoize them here if we cared.
765 SHStrTab.emitString(S.getName());
767 // Keep track of the number of bytes emitted to this section.
768 Index += S.getName().size()+1;
771 // Set the size of .shstrtab now that we know what it is.
772 assert(Index == SHStrTab.size());
773 SHStrTab.Size = Index;
776 /// OutputSectionsAndSectionTable - Now that we have constructed the file header
777 /// and all of the sections, emit these to the ostream destination and emit the
779 void ELFWriter::OutputSectionsAndSectionTable() {
780 // Pass #1: Compute the file offset for each section.
781 size_t FileOff = ElfHdr.size(); // File header first.
783 // Adjust alignment of all section if needed, skip the null section.
784 for (unsigned i=1, e=SectionList.size(); i < e; ++i) {
785 ELFSection &ES = *SectionList[i];
791 // Update Section size
795 // Align FileOff to whatever the alignment restrictions of the section are.
797 FileOff = (FileOff+ES.Align-1) & ~(ES.Align-1);
803 // Align Section Header.
804 unsigned TableAlign = TEW->getPrefELFAlignment();
805 FileOff = (FileOff+TableAlign-1) & ~(TableAlign-1);
807 // Now that we know where all of the sections will be emitted, set the e_shnum
808 // entry in the ELF header.
809 ElfHdr.fixWord16(NumSections, ELFHdr_e_shnum_Offset);
811 // Now that we know the offset in the file of the section table, update the
812 // e_shoff address in the ELF header.
813 ElfHdr.fixWord(FileOff, ELFHdr_e_shoff_Offset);
815 // Now that we know all of the data in the file header, emit it and all of the
817 O.write((char *)&ElfHdr.getData()[0], ElfHdr.size());
818 FileOff = ElfHdr.size();
820 // Section Header Table blob
821 BinaryObject SHdrTable(isLittleEndian, is64Bit);
823 // Emit all of sections to the file and build the section header table.
824 for (ELFSectionIter I=SectionList.begin(), E=SectionList.end(); I != E; ++I) {
825 ELFSection &S = *(*I);
826 DOUT << "SectionIdx: " << S.SectionIdx << ", Name: " << S.getName()
827 << ", Size: " << S.Size << ", Offset: " << S.Offset
828 << ", SectionData Size: " << S.size() << "\n";
830 // Align FileOff to whatever the alignment restrictions of the section are.
833 for (size_t NewFileOff = (FileOff+S.Align-1) & ~(S.Align-1);
834 FileOff != NewFileOff; ++FileOff)
837 O.write((char *)&S.getData()[0], S.Size);
841 EmitSectionHeader(SHdrTable, S);
844 // Align output for the section table.
845 for (size_t NewFileOff = (FileOff+TableAlign-1) & ~(TableAlign-1);
846 FileOff != NewFileOff; ++FileOff)
849 // Emit the section table itself.
850 O.write((char *)&SHdrTable.getData()[0], SHdrTable.size());