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"
33 #include "ELFWriter.h"
34 #include "ELFCodeEmitter.h"
35 #include "llvm/Constants.h"
36 #include "llvm/Module.h"
37 #include "llvm/PassManager.h"
38 #include "llvm/DerivedTypes.h"
39 #include "llvm/CodeGen/BinaryObject.h"
40 #include "llvm/CodeGen/FileWriters.h"
41 #include "llvm/CodeGen/MachineCodeEmitter.h"
42 #include "llvm/CodeGen/ObjectCodeEmitter.h"
43 #include "llvm/CodeGen/MachineCodeEmitter.h"
44 #include "llvm/CodeGen/MachineConstantPool.h"
45 #include "llvm/Target/TargetAsmInfo.h"
46 #include "llvm/Target/TargetData.h"
47 #include "llvm/Target/TargetELFWriterInfo.h"
48 #include "llvm/Target/TargetMachine.h"
49 #include "llvm/Support/Mangler.h"
50 #include "llvm/Support/Streams.h"
51 #include "llvm/Support/raw_ostream.h"
52 #include "llvm/Support/Debug.h"
53 #include "llvm/Support/ErrorHandling.h"
57 char ELFWriter::ID = 0;
59 /// AddELFWriter - Add the ELF writer to the function pass manager
60 ObjectCodeEmitter *llvm::AddELFWriter(PassManagerBase &PM,
63 ELFWriter *EW = new ELFWriter(O, TM);
65 return EW->getObjectCodeEmitter();
68 //===----------------------------------------------------------------------===//
69 // ELFWriter Implementation
70 //===----------------------------------------------------------------------===//
72 ELFWriter::ELFWriter(raw_ostream &o, TargetMachine &tm)
73 : MachineFunctionPass(&ID), O(o), TM(tm),
74 is64Bit(TM.getTargetData()->getPointerSizeInBits() == 64),
75 isLittleEndian(TM.getTargetData()->isLittleEndian()),
76 ElfHdr(isLittleEndian, is64Bit) {
78 TAI = TM.getTargetAsmInfo();
79 TEW = TM.getELFWriterInfo();
81 // Create the object code emitter object for this target.
82 ElfCE = new ELFCodeEmitter(*this);
84 // Inital number of sections
88 ELFWriter::~ELFWriter() {
92 // doInitialization - Emit the file header and all of the global variables for
93 // the module to the ELF file.
94 bool ELFWriter::doInitialization(Module &M) {
95 Mang = new Mangler(M);
99 // Fields e_shnum e_shstrndx are only known after all section have
100 // been emitted. They locations in the ouput buffer are recorded so
101 // to be patched up later.
105 // emitWord method behaves differently for ELF32 and ELF64, writing
106 // 4 bytes in the former and 8 in the last for *_off and *_addr elf types
108 ElfHdr.emitByte(0x7f); // e_ident[EI_MAG0]
109 ElfHdr.emitByte('E'); // e_ident[EI_MAG1]
110 ElfHdr.emitByte('L'); // e_ident[EI_MAG2]
111 ElfHdr.emitByte('F'); // e_ident[EI_MAG3]
113 ElfHdr.emitByte(TEW->getEIClass()); // e_ident[EI_CLASS]
114 ElfHdr.emitByte(TEW->getEIData()); // e_ident[EI_DATA]
115 ElfHdr.emitByte(EV_CURRENT); // e_ident[EI_VERSION]
116 ElfHdr.emitAlignment(16); // e_ident[EI_NIDENT-EI_PAD]
118 ElfHdr.emitWord16(ET_REL); // e_type
119 ElfHdr.emitWord16(TEW->getEMachine()); // e_machine = target
120 ElfHdr.emitWord32(EV_CURRENT); // e_version
121 ElfHdr.emitWord(0); // e_entry, no entry point in .o file
122 ElfHdr.emitWord(0); // e_phoff, no program header for .o
123 ELFHdr_e_shoff_Offset = ElfHdr.size();
124 ElfHdr.emitWord(0); // e_shoff = sec hdr table off in bytes
125 ElfHdr.emitWord32(TEW->getEFlags()); // e_flags = whatever the target wants
126 ElfHdr.emitWord16(TEW->getHdrSize()); // e_ehsize = ELF header size
127 ElfHdr.emitWord16(0); // e_phentsize = prog header entry size
128 ElfHdr.emitWord16(0); // e_phnum = # prog header entries = 0
130 // e_shentsize = Section header entry size
131 ElfHdr.emitWord16(TEW->getSHdrSize());
133 // e_shnum = # of section header ents
134 ELFHdr_e_shnum_Offset = ElfHdr.size();
135 ElfHdr.emitWord16(0); // Placeholder
137 // e_shstrndx = Section # of '.shstrtab'
138 ELFHdr_e_shstrndx_Offset = ElfHdr.size();
139 ElfHdr.emitWord16(0); // Placeholder
141 // Add the null section, which is required to be first in the file.
147 // Get jump table section on the section name returned by TAI
148 ELFSection &ELFWriter::getJumpTableSection() {
149 unsigned Align = TM.getTargetData()->getPointerABIAlignment();
150 return getSection(TAI->getJumpTableDataSection(),
151 ELFSection::SHT_PROGBITS,
152 ELFSection::SHF_ALLOC, Align);
155 // Get a constant pool section based on the section name returned by TAI
156 ELFSection &ELFWriter::getConstantPoolSection(MachineConstantPoolEntry &CPE) {
158 switch (CPE.getRelocationInfo()) {
159 default: llvm_unreachable("Unknown section kind");
160 case 2: Kind = SectionKind::get(SectionKind::ReadOnlyWithRel,false); break;
162 Kind = SectionKind::get(SectionKind::ReadOnlyWithRelLocal,false);
165 switch (TM.getTargetData()->getTypeAllocSize(CPE.getType())) {
166 case 4: Kind = SectionKind::get(SectionKind::MergeableConst4,false); break;
167 case 8: Kind = SectionKind::get(SectionKind::MergeableConst8,false); break;
168 case 16: Kind = SectionKind::get(SectionKind::MergeableConst16,false);break;
169 default: Kind = SectionKind::get(SectionKind::MergeableConst,false); break;
173 return getSection(TAI->getSectionForMergeableConstant(Kind)->getName(),
174 ELFSection::SHT_PROGBITS,
175 ELFSection::SHF_MERGE | ELFSection::SHF_ALLOC,
179 // Return the relocation section of section 'S'. 'RelA' is true
180 // if the relocation section contains entries with addends.
181 ELFSection &ELFWriter::getRelocSection(ELFSection &S) {
182 unsigned SectionHeaderTy = TEW->hasRelocationAddend() ?
183 ELFSection::SHT_RELA : ELFSection::SHT_REL;
184 std::string RelSName(".rel");
185 if (TEW->hasRelocationAddend())
186 RelSName.append("a");
187 RelSName.append(S.getName());
189 return getSection(RelSName, SectionHeaderTy, 0, TEW->getPrefELFAlignment());
192 // getGlobalELFVisibility - Returns the ELF specific visibility type
193 unsigned ELFWriter::getGlobalELFVisibility(const GlobalValue *GV) {
194 switch (GV->getVisibility()) {
196 llvm_unreachable("unknown visibility type");
197 case GlobalValue::DefaultVisibility:
198 return ELFSym::STV_DEFAULT;
199 case GlobalValue::HiddenVisibility:
200 return ELFSym::STV_HIDDEN;
201 case GlobalValue::ProtectedVisibility:
202 return ELFSym::STV_PROTECTED;
207 // getGlobalELFBinding - Returns the ELF specific binding type
208 unsigned ELFWriter::getGlobalELFBinding(const GlobalValue *GV) {
209 if (GV->hasInternalLinkage())
210 return ELFSym::STB_LOCAL;
212 if (GV->hasWeakLinkage())
213 return ELFSym::STB_WEAK;
215 return ELFSym::STB_GLOBAL;
218 // getGlobalELFType - Returns the ELF specific type for a global
219 unsigned ELFWriter::getGlobalELFType(const GlobalValue *GV) {
220 if (GV->isDeclaration())
221 return ELFSym::STT_NOTYPE;
223 if (isa<Function>(GV))
224 return ELFSym::STT_FUNC;
226 return ELFSym::STT_OBJECT;
229 // getElfSectionFlags - Get the ELF Section Header flags based
230 // on the flags defined in ELFTargetAsmInfo.
231 unsigned ELFWriter::getElfSectionFlags(SectionKind Kind) {
232 unsigned ElfSectionFlags = ELFSection::SHF_ALLOC;
235 ElfSectionFlags |= ELFSection::SHF_EXECINSTR;
236 if (Kind.isWriteable())
237 ElfSectionFlags |= ELFSection::SHF_WRITE;
238 if (Kind.isMergeableConst())
239 ElfSectionFlags |= ELFSection::SHF_MERGE;
240 if (Kind.isThreadLocal())
241 ElfSectionFlags |= ELFSection::SHF_TLS;
242 if (Kind.isMergeableCString())
243 ElfSectionFlags |= ELFSection::SHF_STRINGS;
245 return ElfSectionFlags;
248 // isELFUndefSym - the symbol has no section and must be placed in
249 // the symbol table with a reference to the null section.
250 static bool isELFUndefSym(const GlobalValue *GV) {
251 return GV->isDeclaration();
254 // isELFBssSym - for an undef or null value, the symbol must go to a bss
255 // section if it's not weak for linker, otherwise it's a common sym.
256 static bool isELFBssSym(const GlobalVariable *GV) {
257 const Constant *CV = GV->getInitializer();
258 return ((CV->isNullValue() || isa<UndefValue>(CV)) && !GV->isWeakForLinker());
261 // isELFCommonSym - for an undef or null value, the symbol must go to a
262 // common section if it's weak for linker, otherwise bss.
263 static bool isELFCommonSym(const GlobalVariable *GV) {
264 const Constant *CV = GV->getInitializer();
265 return ((CV->isNullValue() || isa<UndefValue>(CV)) && GV->isWeakForLinker());
268 // isELFDataSym - if the symbol is an initialized but no null constant
269 // it must go to some kind of data section gathered from TAI
270 static bool isELFDataSym(const Constant *CV) {
271 return (!(CV->isNullValue() || isa<UndefValue>(CV)));
274 // EmitGlobal - Choose the right section for global and emit it
275 void ELFWriter::EmitGlobal(const GlobalValue *GV) {
277 // Check if the referenced symbol is already emitted
278 if (GblSymLookup.find(GV) != GblSymLookup.end())
281 // Handle ELF Bind, Visibility and Type for the current symbol
282 unsigned SymBind = getGlobalELFBinding(GV);
283 ELFSym *GblSym = new ELFSym(GV);
284 GblSym->setBind(SymBind);
285 GblSym->setVisibility(getGlobalELFVisibility(GV));
286 GblSym->setType(getGlobalELFType(GV));
288 if (isELFUndefSym(GV)) {
289 GblSym->SectionIdx = ELFSection::SHN_UNDEF;
291 assert(isa<GlobalVariable>(GV) && "GV not a global variable!");
292 const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV);
294 // Get ELF section from TAI
295 const Section *S = TAI->SectionForGlobal(GV);
296 unsigned SectionFlags = getElfSectionFlags(S->getKind());
298 // The symbol align should update the section alignment if needed
299 const TargetData *TD = TM.getTargetData();
300 unsigned Align = TD->getPreferredAlignment(GVar);
301 unsigned Size = TD->getTypeAllocSize(GVar->getInitializer()->getType());
304 if (isELFCommonSym(GVar)) {
305 GblSym->SectionIdx = ELFSection::SHN_COMMON;
306 getSection(S->getName(), ELFSection::SHT_NOBITS, SectionFlags, 1);
308 // A new linkonce section is created for each global in the
309 // common section, the default alignment is 1 and the symbol
310 // value contains its alignment.
311 GblSym->Value = Align;
313 } else if (isELFBssSym(GVar)) {
315 getSection(S->getName(), ELFSection::SHT_NOBITS, SectionFlags);
316 GblSym->SectionIdx = ES.SectionIdx;
318 // Update the size with alignment and the next object can
319 // start in the right offset in the section
320 if (Align) ES.Size = (ES.Size + Align-1) & ~(Align-1);
321 ES.Align = std::max(ES.Align, Align);
323 // GblSym->Value should contain the virtual offset inside the section.
324 // Virtual because the BSS space is not allocated on ELF objects
325 GblSym->Value = ES.Size;
328 } else if (isELFDataSym(GV)) {
330 getSection(S->getName(), ELFSection::SHT_PROGBITS, SectionFlags);
331 GblSym->SectionIdx = ES.SectionIdx;
333 // GblSym->Value should contain the symbol offset inside the section,
334 // and all symbols should start on their required alignment boundary
335 ES.Align = std::max(ES.Align, Align);
336 GblSym->Value = (ES.size() + (Align-1)) & (-Align);
337 ES.emitAlignment(ES.Align);
339 // Emit the global to the data section 'ES'
340 EmitGlobalConstant(GVar->getInitializer(), ES);
344 // Private symbols must never go to the symbol table.
346 if (GV->hasPrivateLinkage()) {
347 PrivateSyms.push_back(GblSym);
348 SymIdx = PrivateSyms.size()-1;
350 SymbolList.push_back(GblSym);
353 setGlobalSymLookup(GV, SymIdx);
356 void ELFWriter::EmitGlobalConstantStruct(const ConstantStruct *CVS,
359 // Print the fields in successive locations. Pad to align if needed!
360 const TargetData *TD = TM.getTargetData();
361 unsigned Size = TD->getTypeAllocSize(CVS->getType());
362 const StructLayout *cvsLayout = TD->getStructLayout(CVS->getType());
363 uint64_t sizeSoFar = 0;
364 for (unsigned i = 0, e = CVS->getNumOperands(); i != e; ++i) {
365 const Constant* field = CVS->getOperand(i);
367 // Check if padding is needed and insert one or more 0s.
368 uint64_t fieldSize = TD->getTypeAllocSize(field->getType());
369 uint64_t padSize = ((i == e-1 ? Size : cvsLayout->getElementOffset(i+1))
370 - cvsLayout->getElementOffset(i)) - fieldSize;
371 sizeSoFar += fieldSize + padSize;
373 // Now print the actual field value.
374 EmitGlobalConstant(field, GblS);
376 // Insert padding - this may include padding to increase the size of the
377 // current field up to the ABI size (if the struct is not packed) as well
378 // as padding to ensure that the next field starts at the right offset.
379 for (unsigned p=0; p < padSize; p++)
382 assert(sizeSoFar == cvsLayout->getSizeInBytes() &&
383 "Layout of constant struct may be incorrect!");
386 void ELFWriter::EmitGlobalConstant(const Constant *CV, ELFSection &GblS) {
387 const TargetData *TD = TM.getTargetData();
388 unsigned Size = TD->getTypeAllocSize(CV->getType());
390 if (const ConstantArray *CVA = dyn_cast<ConstantArray>(CV)) {
391 if (CVA->isString()) {
392 std::string GblStr = CVA->getAsString();
393 GblStr.resize(GblStr.size()-1);
394 GblS.emitString(GblStr);
395 } else { // Not a string. Print the values in successive locations
396 for (unsigned i = 0, e = CVA->getNumOperands(); i != e; ++i)
397 EmitGlobalConstant(CVA->getOperand(i), GblS);
400 } else if (const ConstantStruct *CVS = dyn_cast<ConstantStruct>(CV)) {
401 EmitGlobalConstantStruct(CVS, GblS);
403 } else if (const ConstantFP *CFP = dyn_cast<ConstantFP>(CV)) {
404 uint64_t Val = CFP->getValueAPF().bitcastToAPInt().getZExtValue();
405 if (CFP->getType() == Type::DoubleTy)
406 GblS.emitWord64(Val);
407 else if (CFP->getType() == Type::FloatTy)
408 GblS.emitWord32(Val);
409 else if (CFP->getType() == Type::X86_FP80Ty) {
410 llvm_unreachable("X86_FP80Ty global emission not implemented");
411 } else if (CFP->getType() == Type::PPC_FP128Ty)
412 llvm_unreachable("PPC_FP128Ty global emission not implemented");
414 } else if (const ConstantInt *CI = dyn_cast<ConstantInt>(CV)) {
416 GblS.emitWord32(CI->getZExtValue());
418 GblS.emitWord64(CI->getZExtValue());
420 llvm_unreachable("LargeInt global emission not implemented");
422 } else if (const ConstantVector *CP = dyn_cast<ConstantVector>(CV)) {
423 const VectorType *PTy = CP->getType();
424 for (unsigned I = 0, E = PTy->getNumElements(); I < E; ++I)
425 EmitGlobalConstant(CP->getOperand(I), GblS);
427 } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(CV)) {
428 // This is a constant address for a global variable or function and
429 // therefore must be referenced using a relocation entry.
431 // Check if the referenced symbol is already emitted
432 if (GblSymLookup.find(GV) == GblSymLookup.end())
435 // Create the relocation entry for the global value
436 MachineRelocation MR =
437 MachineRelocation::getGV(GblS.getCurrentPCOffset(),
438 TEW->getAbsoluteLabelMachineRelTy(),
439 const_cast<GlobalValue*>(GV));
441 // Fill the data entry with zeros
442 for (unsigned i=0; i < Size; ++i)
445 // Add the relocation entry for the current data section
446 GblS.addRelocation(MR);
448 } else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(CV)) {
449 if (CE->getOpcode() == Instruction::BitCast) {
450 EmitGlobalConstant(CE->getOperand(0), GblS);
453 // See AsmPrinter::EmitConstantValueOnly for other ConstantExpr types
454 llvm_unreachable("Unsupported ConstantExpr type");
457 llvm_unreachable("Unknown global constant type");
461 bool ELFWriter::runOnMachineFunction(MachineFunction &MF) {
462 // Nothing to do here, this is all done through the ElfCE object above.
466 /// doFinalization - Now that the module has been completely processed, emit
467 /// the ELF file to 'O'.
468 bool ELFWriter::doFinalization(Module &M) {
469 // Emit .data section placeholder
472 // Emit .bss section placeholder
475 // Build and emit data, bss and "common" sections.
476 for (Module::global_iterator I = M.global_begin(), E = M.global_end();
480 // Emit all pending globals
481 for (SetVector<GlobalValue*>::const_iterator I = PendingGlobals.begin(),
482 E = PendingGlobals.end(); I != E; ++I)
485 // Emit non-executable stack note
486 if (TAI->getNonexecutableStackDirective())
487 getNonExecStackSection();
489 // Emit a symbol for each section created until now, skip null section
490 for (unsigned i = 1, e = SectionList.size(); i < e; ++i) {
491 ELFSection &ES = *SectionList[i];
492 ELFSym *SectionSym = new ELFSym(0);
493 SectionSym->SectionIdx = ES.SectionIdx;
494 SectionSym->Size = 0;
495 SectionSym->setBind(ELFSym::STB_LOCAL);
496 SectionSym->setType(ELFSym::STT_SECTION);
497 SectionSym->setVisibility(ELFSym::STV_DEFAULT);
498 SymbolList.push_back(SectionSym);
499 ES.Sym = SymbolList.back();
505 // Emit the symbol table now, if non-empty.
508 // Emit the relocation sections.
511 // Emit the sections string table.
512 EmitSectionTableStringTable();
514 // Dump the sections and section table to the .o file.
515 OutputSectionsAndSectionTable();
517 // We are done with the abstract symbols.
522 // Release the name mangler object.
523 delete Mang; Mang = 0;
527 // RelocateField - Patch relocatable field with 'Offset' in 'BO'
528 // using a 'Value' of known 'Size'
529 void ELFWriter::RelocateField(BinaryObject &BO, uint32_t Offset,
530 int64_t Value, unsigned Size) {
532 BO.fixWord32(Value, Offset);
534 BO.fixWord64(Value, Offset);
536 llvm_unreachable("don't know howto patch relocatable field");
539 /// EmitRelocations - Emit relocations
540 void ELFWriter::EmitRelocations() {
542 // True if the target uses the relocation entry to hold the addend,
543 // otherwise the addend is written directly to the relocatable field.
544 bool HasRelA = TEW->hasRelocationAddend();
546 // Create Relocation sections for each section which needs it.
547 for (unsigned i=0, e=SectionList.size(); i != e; ++i) {
548 ELFSection &S = *SectionList[i];
550 // This section does not have relocations
551 if (!S.hasRelocations()) continue;
552 ELFSection &RelSec = getRelocSection(S);
554 // 'Link' - Section hdr idx of the associated symbol table
555 // 'Info' - Section hdr idx of the section to which the relocation applies
556 ELFSection &SymTab = getSymbolTableSection();
557 RelSec.Link = SymTab.SectionIdx;
558 RelSec.Info = S.SectionIdx;
559 RelSec.EntSize = TEW->getRelocationEntrySize();
561 // Get the relocations from Section
562 std::vector<MachineRelocation> Relos = S.getRelocations();
563 for (std::vector<MachineRelocation>::iterator MRI = Relos.begin(),
564 MRE = Relos.end(); MRI != MRE; ++MRI) {
565 MachineRelocation &MR = *MRI;
567 // Relocatable field offset from the section start
568 unsigned RelOffset = MR.getMachineCodeOffset();
570 // Symbol index in the symbol table
573 // Target specific relocation field type and size
574 unsigned RelType = TEW->getRelocationType(MR.getRelocationType());
575 unsigned RelTySize = TEW->getRelocationTySize(RelType);
578 // There are several machine relocations types, and each one of
579 // them needs a different approach to retrieve the symbol table index.
580 if (MR.isGlobalValue()) {
581 const GlobalValue *G = MR.getGlobalValue();
582 SymIdx = GblSymLookup[G];
583 if (G->hasPrivateLinkage()) {
584 // If the target uses a section offset in the relocation:
585 // SymIdx + Addend = section sym for global + section offset
586 unsigned SectionIdx = PrivateSyms[SymIdx]->SectionIdx;
587 Addend = PrivateSyms[SymIdx]->Value;
588 SymIdx = SectionList[SectionIdx]->getSymbolTableIndex();
590 Addend = TEW->getDefaultAddendForRelTy(RelType);
593 // Get the symbol index for the section symbol
594 unsigned SectionIdx = MR.getConstantVal();
595 SymIdx = SectionList[SectionIdx]->getSymbolTableIndex();
596 Addend = (uint64_t)MR.getResultPointer();
598 // For pc relative relocations where symbols are defined in the same
599 // section they are referenced, ignore the relocation entry and patch
600 // the relocatable field with the symbol offset directly.
601 if (S.SectionIdx == SectionIdx && TEW->isPCRelativeRel(RelType)) {
602 int64_t Value = TEW->computeRelocation(Addend, RelOffset, RelType);
603 RelocateField(S, RelOffset, Value, RelTySize);
607 // Handle Jump Table Index relocation
608 if ((SectionIdx == getJumpTableSection().SectionIdx) &&
609 TEW->hasCustomJumpTableIndexRelTy()) {
610 RelType = TEW->getJumpTableIndexRelTy();
611 RelTySize = TEW->getRelocationTySize(RelType);
615 // The target without addend on the relocation symbol must be
616 // patched in the relocation place itself to contain the addend
618 RelocateField(S, RelOffset, Addend, RelTySize);
620 // Get the relocation entry and emit to the relocation section
621 ELFRelocation Rel(RelOffset, SymIdx, RelType, HasRelA, Addend);
622 EmitRelocation(RelSec, Rel, HasRelA);
627 /// EmitRelocation - Write relocation 'Rel' to the relocation section 'Rel'
628 void ELFWriter::EmitRelocation(BinaryObject &RelSec, ELFRelocation &Rel,
630 RelSec.emitWord(Rel.getOffset());
631 RelSec.emitWord(Rel.getInfo(is64Bit));
633 RelSec.emitWord(Rel.getAddend());
636 /// EmitSymbol - Write symbol 'Sym' to the symbol table 'SymbolTable'
637 void ELFWriter::EmitSymbol(BinaryObject &SymbolTable, ELFSym &Sym) {
639 SymbolTable.emitWord32(Sym.NameIdx);
640 SymbolTable.emitByte(Sym.Info);
641 SymbolTable.emitByte(Sym.Other);
642 SymbolTable.emitWord16(Sym.SectionIdx);
643 SymbolTable.emitWord64(Sym.Value);
644 SymbolTable.emitWord64(Sym.Size);
646 SymbolTable.emitWord32(Sym.NameIdx);
647 SymbolTable.emitWord32(Sym.Value);
648 SymbolTable.emitWord32(Sym.Size);
649 SymbolTable.emitByte(Sym.Info);
650 SymbolTable.emitByte(Sym.Other);
651 SymbolTable.emitWord16(Sym.SectionIdx);
655 /// EmitSectionHeader - Write section 'Section' header in 'SHdrTab'
656 /// Section Header Table
657 void ELFWriter::EmitSectionHeader(BinaryObject &SHdrTab,
658 const ELFSection &SHdr) {
659 SHdrTab.emitWord32(SHdr.NameIdx);
660 SHdrTab.emitWord32(SHdr.Type);
662 SHdrTab.emitWord64(SHdr.Flags);
663 SHdrTab.emitWord(SHdr.Addr);
664 SHdrTab.emitWord(SHdr.Offset);
665 SHdrTab.emitWord64(SHdr.Size);
666 SHdrTab.emitWord32(SHdr.Link);
667 SHdrTab.emitWord32(SHdr.Info);
668 SHdrTab.emitWord64(SHdr.Align);
669 SHdrTab.emitWord64(SHdr.EntSize);
671 SHdrTab.emitWord32(SHdr.Flags);
672 SHdrTab.emitWord(SHdr.Addr);
673 SHdrTab.emitWord(SHdr.Offset);
674 SHdrTab.emitWord32(SHdr.Size);
675 SHdrTab.emitWord32(SHdr.Link);
676 SHdrTab.emitWord32(SHdr.Info);
677 SHdrTab.emitWord32(SHdr.Align);
678 SHdrTab.emitWord32(SHdr.EntSize);
682 /// EmitStringTable - If the current symbol table is non-empty, emit the string
684 void ELFWriter::EmitStringTable() {
685 if (!SymbolList.size()) return; // Empty symbol table.
686 ELFSection &StrTab = getStringTableSection();
688 // Set the zero'th symbol to a null byte, as required.
691 // Walk on the symbol list and write symbol names into the string table.
693 for (ELFSymIter I=SymbolList.begin(), E=SymbolList.end(); I != E; ++I) {
696 // Use the name mangler to uniquify the LLVM symbol.
698 if (Sym.GV) Name.append(Mang->getMangledName(Sym.GV));
704 StrTab.emitString(Name);
706 // Keep track of the number of bytes emitted to this section.
707 Index += Name.size()+1;
710 assert(Index == StrTab.size());
714 // SortSymbols - On the symbol table local symbols must come before
715 // all other symbols with non-local bindings. The return value is
716 // the position of the first non local symbol.
717 unsigned ELFWriter::SortSymbols() {
718 unsigned FirstNonLocalSymbol;
719 std::vector<ELFSym*> LocalSyms, OtherSyms;
721 for (ELFSymIter I=SymbolList.begin(), E=SymbolList.end(); I != E; ++I) {
722 if ((*I)->isLocalBind())
723 LocalSyms.push_back(*I);
725 OtherSyms.push_back(*I);
728 FirstNonLocalSymbol = LocalSyms.size();
730 for (unsigned i = 0; i < FirstNonLocalSymbol; ++i)
731 SymbolList.push_back(LocalSyms[i]);
733 for (ELFSymIter I=OtherSyms.begin(), E=OtherSyms.end(); I != E; ++I)
734 SymbolList.push_back(*I);
739 return FirstNonLocalSymbol;
742 /// EmitSymbolTable - Emit the symbol table itself.
743 void ELFWriter::EmitSymbolTable() {
744 if (!SymbolList.size()) return; // Empty symbol table.
746 // Now that we have emitted the string table and know the offset into the
747 // string table of each symbol, emit the symbol table itself.
748 ELFSection &SymTab = getSymbolTableSection();
749 SymTab.Align = TEW->getPrefELFAlignment();
751 // Section Index of .strtab.
752 SymTab.Link = getStringTableSection().SectionIdx;
754 // Size of each symtab entry.
755 SymTab.EntSize = TEW->getSymTabEntrySize();
757 // The first entry in the symtab is the null symbol
758 SymbolList.insert(SymbolList.begin(), new ELFSym(0));
760 // Reorder the symbol table with local symbols first!
761 unsigned FirstNonLocalSymbol = SortSymbols();
763 // Emit all the symbols to the symbol table.
764 for (unsigned i = 0, e = SymbolList.size(); i < e; ++i) {
765 ELFSym &Sym = *SymbolList[i];
767 // Emit symbol to the symbol table
768 EmitSymbol(SymTab, Sym);
770 // Record the symbol table index for each global value
771 if (Sym.GV) setGlobalSymLookup(Sym.GV, i);
773 // Keep track on the symbol index into the symbol table
777 // One greater than the symbol table index of the last local symbol
778 SymTab.Info = FirstNonLocalSymbol;
779 SymTab.Size = SymTab.size();
782 /// EmitSectionTableStringTable - This method adds and emits a section for the
783 /// ELF Section Table string table: the string table that holds all of the
785 void ELFWriter::EmitSectionTableStringTable() {
786 // First step: add the section for the string table to the list of sections:
787 ELFSection &SHStrTab = getSectionHeaderStringTableSection();
789 // Now that we know which section number is the .shstrtab section, update the
790 // e_shstrndx entry in the ELF header.
791 ElfHdr.fixWord16(SHStrTab.SectionIdx, ELFHdr_e_shstrndx_Offset);
793 // Set the NameIdx of each section in the string table and emit the bytes for
797 for (ELFSectionIter I=SectionList.begin(), E=SectionList.end(); I != E; ++I) {
798 ELFSection &S = *(*I);
799 // Set the index into the table. Note if we have lots of entries with
800 // common suffixes, we could memoize them here if we cared.
802 SHStrTab.emitString(S.getName());
804 // Keep track of the number of bytes emitted to this section.
805 Index += S.getName().size()+1;
808 // Set the size of .shstrtab now that we know what it is.
809 assert(Index == SHStrTab.size());
810 SHStrTab.Size = Index;
813 /// OutputSectionsAndSectionTable - Now that we have constructed the file header
814 /// and all of the sections, emit these to the ostream destination and emit the
816 void ELFWriter::OutputSectionsAndSectionTable() {
817 // Pass #1: Compute the file offset for each section.
818 size_t FileOff = ElfHdr.size(); // File header first.
820 // Adjust alignment of all section if needed, skip the null section.
821 for (unsigned i=1, e=SectionList.size(); i < e; ++i) {
822 ELFSection &ES = *SectionList[i];
828 // Update Section size
832 // Align FileOff to whatever the alignment restrictions of the section are.
834 FileOff = (FileOff+ES.Align-1) & ~(ES.Align-1);
840 // Align Section Header.
841 unsigned TableAlign = TEW->getPrefELFAlignment();
842 FileOff = (FileOff+TableAlign-1) & ~(TableAlign-1);
844 // Now that we know where all of the sections will be emitted, set the e_shnum
845 // entry in the ELF header.
846 ElfHdr.fixWord16(NumSections, ELFHdr_e_shnum_Offset);
848 // Now that we know the offset in the file of the section table, update the
849 // e_shoff address in the ELF header.
850 ElfHdr.fixWord(FileOff, ELFHdr_e_shoff_Offset);
852 // Now that we know all of the data in the file header, emit it and all of the
854 O.write((char *)&ElfHdr.getData()[0], ElfHdr.size());
855 FileOff = ElfHdr.size();
857 // Section Header Table blob
858 BinaryObject SHdrTable(isLittleEndian, is64Bit);
860 // Emit all of sections to the file and build the section header table.
861 for (ELFSectionIter I=SectionList.begin(), E=SectionList.end(); I != E; ++I) {
862 ELFSection &S = *(*I);
863 DOUT << "SectionIdx: " << S.SectionIdx << ", Name: " << S.getName()
864 << ", Size: " << S.Size << ", Offset: " << S.Offset
865 << ", SectionData Size: " << S.size() << "\n";
867 // Align FileOff to whatever the alignment restrictions of the section are.
870 for (size_t NewFileOff = (FileOff+S.Align-1) & ~(S.Align-1);
871 FileOff != NewFileOff; ++FileOff)
874 O.write((char *)&S.getData()[0], S.Size);
878 EmitSectionHeader(SHdrTable, S);
881 // Align output for the section table.
882 for (size_t NewFileOff = (FileOff+TableAlign-1) & ~(TableAlign-1);
883 FileOff != NewFileOff; ++FileOff)
886 // Emit the section table itself.
887 O.write((char *)&SHdrTable.getData()[0], SHdrTable.size());