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 GlobalVariable *GV) {
244 const Constant *CV = GV->getInitializer();
245 return ((CV->isNullValue() || isa<UndefValue>(CV)) && !GV->isWeakForLinker());
248 // isELFCommonSym - for an undef or null value, the symbol must go to a
249 // common section if it's weak for linker, otherwise bss.
250 static bool isELFCommonSym(const GlobalVariable *GV) {
251 const Constant *CV = GV->getInitializer();
252 return ((CV->isNullValue() || isa<UndefValue>(CV)) && GV->isWeakForLinker());
255 // isELFDataSym - if the symbol is an initialized but no null constant
256 // it must go to some kind of data section gathered from TAI
257 static bool isELFDataSym(const Constant *CV) {
258 return (!(CV->isNullValue() || isa<UndefValue>(CV)));
261 // EmitGlobal - Choose the right section for global and emit it
262 void ELFWriter::EmitGlobal(const GlobalValue *GV) {
264 // Check if the referenced symbol is already emitted
265 if (GblSymLookup.find(GV) != GblSymLookup.end())
268 // Handle ELF Bind, Visibility and Type for the current symbol
269 unsigned SymBind = getGlobalELFBinding(GV);
270 ELFSym *GblSym = new ELFSym(GV);
271 GblSym->setBind(SymBind);
272 GblSym->setVisibility(getGlobalELFVisibility(GV));
273 GblSym->setType(getGlobalELFType(GV));
275 if (isELFUndefSym(GV)) {
276 GblSym->SectionIdx = ELFSection::SHN_UNDEF;
278 assert(isa<GlobalVariable>(GV) && "GV not a global variable!");
279 const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV);
281 // Get ELF section from TAI
282 const Section *S = TAI->SectionForGlobal(GV);
283 unsigned SectionFlags = getElfSectionFlags(S->getFlags());
285 // The symbol align should update the section alignment if needed
286 const TargetData *TD = TM.getTargetData();
287 unsigned Align = TD->getPreferredAlignment(GVar);
288 unsigned Size = TD->getTypeAllocSize(GVar->getInitializer()->getType());
291 if (isELFCommonSym(GVar)) {
292 GblSym->SectionIdx = ELFSection::SHN_COMMON;
293 getSection(S->getName(), ELFSection::SHT_NOBITS, SectionFlags, 1);
295 // A new linkonce section is created for each global in the
296 // common section, the default alignment is 1 and the symbol
297 // value contains its alignment.
298 GblSym->Value = Align;
300 } else if (isELFBssSym(GVar)) {
302 getSection(S->getName(), ELFSection::SHT_NOBITS, SectionFlags);
303 GblSym->SectionIdx = ES.SectionIdx;
305 // Update the size with alignment and the next object can
306 // start in the right offset in the section
307 if (Align) ES.Size = (ES.Size + Align-1) & ~(Align-1);
308 ES.Align = std::max(ES.Align, Align);
310 // GblSym->Value should contain the virtual offset inside the section.
311 // Virtual because the BSS space is not allocated on ELF objects
312 GblSym->Value = ES.Size;
315 } else if (isELFDataSym(GV)) {
317 getSection(S->getName(), ELFSection::SHT_PROGBITS, SectionFlags);
318 GblSym->SectionIdx = ES.SectionIdx;
320 // GblSym->Value should contain the symbol offset inside the section,
321 // and all symbols should start on their required alignment boundary
322 ES.Align = std::max(ES.Align, Align);
323 GblSym->Value = (ES.size() + (Align-1)) & (-Align);
324 ES.emitAlignment(ES.Align);
326 // Emit the global to the data section 'ES'
327 EmitGlobalConstant(GVar->getInitializer(), ES);
331 // Private symbols must never go to the symbol table.
333 if (GV->hasPrivateLinkage()) {
334 PrivateSyms.push_back(GblSym);
335 SymIdx = PrivateSyms.size()-1;
337 SymbolList.push_back(GblSym);
340 setGlobalSymLookup(GV, SymIdx);
343 void ELFWriter::EmitGlobalConstantStruct(const ConstantStruct *CVS,
346 // Print the fields in successive locations. Pad to align if needed!
347 const TargetData *TD = TM.getTargetData();
348 unsigned Size = TD->getTypeAllocSize(CVS->getType());
349 const StructLayout *cvsLayout = TD->getStructLayout(CVS->getType());
350 uint64_t sizeSoFar = 0;
351 for (unsigned i = 0, e = CVS->getNumOperands(); i != e; ++i) {
352 const Constant* field = CVS->getOperand(i);
354 // Check if padding is needed and insert one or more 0s.
355 uint64_t fieldSize = TD->getTypeAllocSize(field->getType());
356 uint64_t padSize = ((i == e-1 ? Size : cvsLayout->getElementOffset(i+1))
357 - cvsLayout->getElementOffset(i)) - fieldSize;
358 sizeSoFar += fieldSize + padSize;
360 // Now print the actual field value.
361 EmitGlobalConstant(field, GblS);
363 // Insert padding - this may include padding to increase the size of the
364 // current field up to the ABI size (if the struct is not packed) as well
365 // as padding to ensure that the next field starts at the right offset.
366 for (unsigned p=0; p < padSize; p++)
369 assert(sizeSoFar == cvsLayout->getSizeInBytes() &&
370 "Layout of constant struct may be incorrect!");
373 void ELFWriter::EmitGlobalConstant(const Constant *CV, ELFSection &GblS) {
374 const TargetData *TD = TM.getTargetData();
375 unsigned Size = TD->getTypeAllocSize(CV->getType());
377 if (const ConstantArray *CVA = dyn_cast<ConstantArray>(CV)) {
378 if (CVA->isString()) {
379 std::string GblStr = CVA->getAsString();
380 GblStr.resize(GblStr.size()-1);
381 GblS.emitString(GblStr);
382 } else { // Not a string. Print the values in successive locations
383 for (unsigned i = 0, e = CVA->getNumOperands(); i != e; ++i)
384 EmitGlobalConstant(CVA->getOperand(i), GblS);
387 } else if (const ConstantStruct *CVS = dyn_cast<ConstantStruct>(CV)) {
388 EmitGlobalConstantStruct(CVS, GblS);
390 } else if (const ConstantFP *CFP = dyn_cast<ConstantFP>(CV)) {
391 uint64_t Val = CFP->getValueAPF().bitcastToAPInt().getZExtValue();
392 if (CFP->getType() == Type::DoubleTy)
393 GblS.emitWord64(Val);
394 else if (CFP->getType() == Type::FloatTy)
395 GblS.emitWord32(Val);
396 else if (CFP->getType() == Type::X86_FP80Ty) {
397 llvm_unreachable("X86_FP80Ty global emission not implemented");
398 } else if (CFP->getType() == Type::PPC_FP128Ty)
399 llvm_unreachable("PPC_FP128Ty global emission not implemented");
401 } else if (const ConstantInt *CI = dyn_cast<ConstantInt>(CV)) {
403 GblS.emitWord32(CI->getZExtValue());
405 GblS.emitWord64(CI->getZExtValue());
407 llvm_unreachable("LargeInt global emission not implemented");
409 } else if (const ConstantVector *CP = dyn_cast<ConstantVector>(CV)) {
410 const VectorType *PTy = CP->getType();
411 for (unsigned I = 0, E = PTy->getNumElements(); I < E; ++I)
412 EmitGlobalConstant(CP->getOperand(I), GblS);
414 } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(CV)) {
415 // This is a constant address for a global variable or function and
416 // therefore must be referenced using a relocation entry.
418 // Check if the referenced symbol is already emitted
419 if (GblSymLookup.find(GV) == GblSymLookup.end())
422 // Create the relocation entry for the global value
423 MachineRelocation MR =
424 MachineRelocation::getGV(GblS.getCurrentPCOffset(),
425 TEW->getAbsoluteLabelMachineRelTy(),
426 const_cast<GlobalValue*>(GV));
428 // Fill the data entry with zeros
429 for (unsigned i=0; i < Size; ++i)
432 // Add the relocation entry for the current data section
433 GblS.addRelocation(MR);
435 } else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(CV)) {
436 if (CE->getOpcode() == Instruction::BitCast) {
437 EmitGlobalConstant(CE->getOperand(0), GblS);
440 // See AsmPrinter::EmitConstantValueOnly for other ConstantExpr types
441 llvm_unreachable("Unsupported ConstantExpr type");
444 llvm_unreachable("Unknown global constant type");
448 bool ELFWriter::runOnMachineFunction(MachineFunction &MF) {
449 // Nothing to do here, this is all done through the ElfCE object above.
453 /// doFinalization - Now that the module has been completely processed, emit
454 /// the ELF file to 'O'.
455 bool ELFWriter::doFinalization(Module &M) {
456 // Emit .data section placeholder
459 // Emit .bss section placeholder
462 // Build and emit data, bss and "common" sections.
463 for (Module::global_iterator I = M.global_begin(), E = M.global_end();
467 // Emit all pending globals
468 for (SetVector<GlobalValue*>::const_iterator I = PendingGlobals.begin(),
469 E = PendingGlobals.end(); I != E; ++I)
472 // Emit non-executable stack note
473 if (TAI->getNonexecutableStackDirective())
474 getNonExecStackSection();
476 // Emit a symbol for each section created until now, skip null section
477 for (unsigned i = 1, e = SectionList.size(); i < e; ++i) {
478 ELFSection &ES = *SectionList[i];
479 ELFSym *SectionSym = new ELFSym(0);
480 SectionSym->SectionIdx = ES.SectionIdx;
481 SectionSym->Size = 0;
482 SectionSym->setBind(ELFSym::STB_LOCAL);
483 SectionSym->setType(ELFSym::STT_SECTION);
484 SectionSym->setVisibility(ELFSym::STV_DEFAULT);
485 SymbolList.push_back(SectionSym);
486 ES.Sym = SymbolList.back();
492 // Emit the symbol table now, if non-empty.
495 // Emit the relocation sections.
498 // Emit the sections string table.
499 EmitSectionTableStringTable();
501 // Dump the sections and section table to the .o file.
502 OutputSectionsAndSectionTable();
504 // We are done with the abstract symbols.
509 // Release the name mangler object.
510 delete Mang; Mang = 0;
514 // RelocateField - Patch relocatable field with 'Offset' in 'BO'
515 // using a 'Value' of known 'Size'
516 void ELFWriter::RelocateField(BinaryObject &BO, uint32_t Offset,
517 int64_t Value, unsigned Size) {
519 BO.fixWord32(Value, Offset);
521 BO.fixWord64(Value, Offset);
523 llvm_unreachable("don't know howto patch relocatable field");
526 /// EmitRelocations - Emit relocations
527 void ELFWriter::EmitRelocations() {
529 // True if the target uses the relocation entry to hold the addend,
530 // otherwise the addend is written directly to the relocatable field.
531 bool HasRelA = TEW->hasRelocationAddend();
533 // Create Relocation sections for each section which needs it.
534 for (unsigned i=0, e=SectionList.size(); i != e; ++i) {
535 ELFSection &S = *SectionList[i];
537 // This section does not have relocations
538 if (!S.hasRelocations()) continue;
539 ELFSection &RelSec = getRelocSection(S);
541 // 'Link' - Section hdr idx of the associated symbol table
542 // 'Info' - Section hdr idx of the section to which the relocation applies
543 ELFSection &SymTab = getSymbolTableSection();
544 RelSec.Link = SymTab.SectionIdx;
545 RelSec.Info = S.SectionIdx;
546 RelSec.EntSize = TEW->getRelocationEntrySize();
548 // Get the relocations from Section
549 std::vector<MachineRelocation> Relos = S.getRelocations();
550 for (std::vector<MachineRelocation>::iterator MRI = Relos.begin(),
551 MRE = Relos.end(); MRI != MRE; ++MRI) {
552 MachineRelocation &MR = *MRI;
554 // Relocatable field offset from the section start
555 unsigned RelOffset = MR.getMachineCodeOffset();
557 // Symbol index in the symbol table
560 // Target specific relocation field type and size
561 unsigned RelType = TEW->getRelocationType(MR.getRelocationType());
562 unsigned RelTySize = TEW->getRelocationTySize(RelType);
565 // There are several machine relocations types, and each one of
566 // them needs a different approach to retrieve the symbol table index.
567 if (MR.isGlobalValue()) {
568 const GlobalValue *G = MR.getGlobalValue();
569 SymIdx = GblSymLookup[G];
570 if (G->hasPrivateLinkage()) {
571 // If the target uses a section offset in the relocation:
572 // SymIdx + Addend = section sym for global + section offset
573 unsigned SectionIdx = PrivateSyms[SymIdx]->SectionIdx;
574 Addend = PrivateSyms[SymIdx]->Value;
575 SymIdx = SectionList[SectionIdx]->getSymbolTableIndex();
577 Addend = TEW->getDefaultAddendForRelTy(RelType);
580 // Get the symbol index for the section symbol
581 unsigned SectionIdx = MR.getConstantVal();
582 SymIdx = SectionList[SectionIdx]->getSymbolTableIndex();
583 Addend = (uint64_t)MR.getResultPointer();
585 // For pc relative relocations where symbols are defined in the same
586 // section they are referenced, ignore the relocation entry and patch
587 // the relocatable field with the symbol offset directly.
588 if (S.SectionIdx == SectionIdx && TEW->isPCRelativeRel(RelType)) {
589 int64_t Value = TEW->computeRelocation(Addend, RelOffset, RelType);
590 RelocateField(S, RelOffset, Value, RelTySize);
594 // Handle Jump Table Index relocation
595 if ((SectionIdx == getJumpTableSection().SectionIdx) &&
596 TEW->hasCustomJumpTableIndexRelTy()) {
597 RelType = TEW->getJumpTableIndexRelTy();
598 RelTySize = TEW->getRelocationTySize(RelType);
602 // The target without addend on the relocation symbol must be
603 // patched in the relocation place itself to contain the addend
605 RelocateField(S, RelOffset, Addend, RelTySize);
607 // Get the relocation entry and emit to the relocation section
608 ELFRelocation Rel(RelOffset, SymIdx, RelType, HasRelA, Addend);
609 EmitRelocation(RelSec, Rel, HasRelA);
614 /// EmitRelocation - Write relocation 'Rel' to the relocation section 'Rel'
615 void ELFWriter::EmitRelocation(BinaryObject &RelSec, ELFRelocation &Rel,
617 RelSec.emitWord(Rel.getOffset());
618 RelSec.emitWord(Rel.getInfo(is64Bit));
620 RelSec.emitWord(Rel.getAddend());
623 /// EmitSymbol - Write symbol 'Sym' to the symbol table 'SymbolTable'
624 void ELFWriter::EmitSymbol(BinaryObject &SymbolTable, ELFSym &Sym) {
626 SymbolTable.emitWord32(Sym.NameIdx);
627 SymbolTable.emitByte(Sym.Info);
628 SymbolTable.emitByte(Sym.Other);
629 SymbolTable.emitWord16(Sym.SectionIdx);
630 SymbolTable.emitWord64(Sym.Value);
631 SymbolTable.emitWord64(Sym.Size);
633 SymbolTable.emitWord32(Sym.NameIdx);
634 SymbolTable.emitWord32(Sym.Value);
635 SymbolTable.emitWord32(Sym.Size);
636 SymbolTable.emitByte(Sym.Info);
637 SymbolTable.emitByte(Sym.Other);
638 SymbolTable.emitWord16(Sym.SectionIdx);
642 /// EmitSectionHeader - Write section 'Section' header in 'SHdrTab'
643 /// Section Header Table
644 void ELFWriter::EmitSectionHeader(BinaryObject &SHdrTab,
645 const ELFSection &SHdr) {
646 SHdrTab.emitWord32(SHdr.NameIdx);
647 SHdrTab.emitWord32(SHdr.Type);
649 SHdrTab.emitWord64(SHdr.Flags);
650 SHdrTab.emitWord(SHdr.Addr);
651 SHdrTab.emitWord(SHdr.Offset);
652 SHdrTab.emitWord64(SHdr.Size);
653 SHdrTab.emitWord32(SHdr.Link);
654 SHdrTab.emitWord32(SHdr.Info);
655 SHdrTab.emitWord64(SHdr.Align);
656 SHdrTab.emitWord64(SHdr.EntSize);
658 SHdrTab.emitWord32(SHdr.Flags);
659 SHdrTab.emitWord(SHdr.Addr);
660 SHdrTab.emitWord(SHdr.Offset);
661 SHdrTab.emitWord32(SHdr.Size);
662 SHdrTab.emitWord32(SHdr.Link);
663 SHdrTab.emitWord32(SHdr.Info);
664 SHdrTab.emitWord32(SHdr.Align);
665 SHdrTab.emitWord32(SHdr.EntSize);
669 /// EmitStringTable - If the current symbol table is non-empty, emit the string
671 void ELFWriter::EmitStringTable() {
672 if (!SymbolList.size()) return; // Empty symbol table.
673 ELFSection &StrTab = getStringTableSection();
675 // Set the zero'th symbol to a null byte, as required.
678 // Walk on the symbol list and write symbol names into the string table.
680 for (ELFSymIter I=SymbolList.begin(), E=SymbolList.end(); I != E; ++I) {
683 // Use the name mangler to uniquify the LLVM symbol.
685 if (Sym.GV) Name.append(Mang->getMangledName(Sym.GV));
691 StrTab.emitString(Name);
693 // Keep track of the number of bytes emitted to this section.
694 Index += Name.size()+1;
697 assert(Index == StrTab.size());
701 // SortSymbols - On the symbol table local symbols must come before
702 // all other symbols with non-local bindings. The return value is
703 // the position of the first non local symbol.
704 unsigned ELFWriter::SortSymbols() {
705 unsigned FirstNonLocalSymbol;
706 std::vector<ELFSym*> LocalSyms, OtherSyms;
708 for (ELFSymIter I=SymbolList.begin(), E=SymbolList.end(); I != E; ++I) {
709 if ((*I)->isLocalBind())
710 LocalSyms.push_back(*I);
712 OtherSyms.push_back(*I);
715 FirstNonLocalSymbol = LocalSyms.size();
717 for (unsigned i = 0; i < FirstNonLocalSymbol; ++i)
718 SymbolList.push_back(LocalSyms[i]);
720 for (ELFSymIter I=OtherSyms.begin(), E=OtherSyms.end(); I != E; ++I)
721 SymbolList.push_back(*I);
726 return FirstNonLocalSymbol;
729 /// EmitSymbolTable - Emit the symbol table itself.
730 void ELFWriter::EmitSymbolTable() {
731 if (!SymbolList.size()) return; // Empty symbol table.
733 // Now that we have emitted the string table and know the offset into the
734 // string table of each symbol, emit the symbol table itself.
735 ELFSection &SymTab = getSymbolTableSection();
736 SymTab.Align = TEW->getPrefELFAlignment();
738 // Section Index of .strtab.
739 SymTab.Link = getStringTableSection().SectionIdx;
741 // Size of each symtab entry.
742 SymTab.EntSize = TEW->getSymTabEntrySize();
744 // The first entry in the symtab is the null symbol
745 SymbolList.insert(SymbolList.begin(), new ELFSym(0));
747 // Reorder the symbol table with local symbols first!
748 unsigned FirstNonLocalSymbol = SortSymbols();
750 // Emit all the symbols to the symbol table.
751 for (unsigned i = 0, e = SymbolList.size(); i < e; ++i) {
752 ELFSym &Sym = *SymbolList[i];
754 // Emit symbol to the symbol table
755 EmitSymbol(SymTab, Sym);
757 // Record the symbol table index for each global value
758 if (Sym.GV) setGlobalSymLookup(Sym.GV, i);
760 // Keep track on the symbol index into the symbol table
764 // One greater than the symbol table index of the last local symbol
765 SymTab.Info = FirstNonLocalSymbol;
766 SymTab.Size = SymTab.size();
769 /// EmitSectionTableStringTable - This method adds and emits a section for the
770 /// ELF Section Table string table: the string table that holds all of the
772 void ELFWriter::EmitSectionTableStringTable() {
773 // First step: add the section for the string table to the list of sections:
774 ELFSection &SHStrTab = getSectionHeaderStringTableSection();
776 // Now that we know which section number is the .shstrtab section, update the
777 // e_shstrndx entry in the ELF header.
778 ElfHdr.fixWord16(SHStrTab.SectionIdx, ELFHdr_e_shstrndx_Offset);
780 // Set the NameIdx of each section in the string table and emit the bytes for
784 for (ELFSectionIter I=SectionList.begin(), E=SectionList.end(); I != E; ++I) {
785 ELFSection &S = *(*I);
786 // Set the index into the table. Note if we have lots of entries with
787 // common suffixes, we could memoize them here if we cared.
789 SHStrTab.emitString(S.getName());
791 // Keep track of the number of bytes emitted to this section.
792 Index += S.getName().size()+1;
795 // Set the size of .shstrtab now that we know what it is.
796 assert(Index == SHStrTab.size());
797 SHStrTab.Size = Index;
800 /// OutputSectionsAndSectionTable - Now that we have constructed the file header
801 /// and all of the sections, emit these to the ostream destination and emit the
803 void ELFWriter::OutputSectionsAndSectionTable() {
804 // Pass #1: Compute the file offset for each section.
805 size_t FileOff = ElfHdr.size(); // File header first.
807 // Adjust alignment of all section if needed, skip the null section.
808 for (unsigned i=1, e=SectionList.size(); i < e; ++i) {
809 ELFSection &ES = *SectionList[i];
815 // Update Section size
819 // Align FileOff to whatever the alignment restrictions of the section are.
821 FileOff = (FileOff+ES.Align-1) & ~(ES.Align-1);
827 // Align Section Header.
828 unsigned TableAlign = TEW->getPrefELFAlignment();
829 FileOff = (FileOff+TableAlign-1) & ~(TableAlign-1);
831 // Now that we know where all of the sections will be emitted, set the e_shnum
832 // entry in the ELF header.
833 ElfHdr.fixWord16(NumSections, ELFHdr_e_shnum_Offset);
835 // Now that we know the offset in the file of the section table, update the
836 // e_shoff address in the ELF header.
837 ElfHdr.fixWord(FileOff, ELFHdr_e_shoff_Offset);
839 // Now that we know all of the data in the file header, emit it and all of the
841 O.write((char *)&ElfHdr.getData()[0], ElfHdr.size());
842 FileOff = ElfHdr.size();
844 // Section Header Table blob
845 BinaryObject SHdrTable(isLittleEndian, is64Bit);
847 // Emit all of sections to the file and build the section header table.
848 for (ELFSectionIter I=SectionList.begin(), E=SectionList.end(); I != E; ++I) {
849 ELFSection &S = *(*I);
850 DOUT << "SectionIdx: " << S.SectionIdx << ", Name: " << S.getName()
851 << ", Size: " << S.Size << ", Offset: " << S.Offset
852 << ", SectionData Size: " << S.size() << "\n";
854 // Align FileOff to whatever the alignment restrictions of the section are.
857 for (size_t NewFileOff = (FileOff+S.Align-1) & ~(S.Align-1);
858 FileOff != NewFileOff; ++FileOff)
861 O.write((char *)&S.getData()[0], S.Size);
865 EmitSectionHeader(SHdrTable, S);
868 // Align output for the section table.
869 for (size_t NewFileOff = (FileOff+TableAlign-1) & ~(TableAlign-1);
870 FileOff != NewFileOff; ++FileOff)
873 // Emit the section table itself.
874 O.write((char *)&SHdrTable.getData()[0], SHdrTable.size());