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/TargetLowering.h"
49 #include "llvm/Target/TargetLoweringObjectFile.h"
50 #include "llvm/Target/TargetMachine.h"
51 #include "llvm/Support/Mangler.h"
52 #include "llvm/Support/Streams.h"
53 #include "llvm/Support/raw_ostream.h"
54 #include "llvm/Support/Debug.h"
55 #include "llvm/Support/ErrorHandling.h"
59 char ELFWriter::ID = 0;
61 /// AddELFWriter - Add the ELF writer to the function pass manager
62 ObjectCodeEmitter *llvm::AddELFWriter(PassManagerBase &PM,
65 ELFWriter *EW = new ELFWriter(O, TM);
67 return EW->getObjectCodeEmitter();
70 //===----------------------------------------------------------------------===//
71 // ELFWriter Implementation
72 //===----------------------------------------------------------------------===//
74 ELFWriter::ELFWriter(raw_ostream &o, TargetMachine &tm)
75 : MachineFunctionPass(&ID), O(o), TM(tm),
76 is64Bit(TM.getTargetData()->getPointerSizeInBits() == 64),
77 isLittleEndian(TM.getTargetData()->isLittleEndian()),
78 ElfHdr(isLittleEndian, is64Bit) {
80 TAI = TM.getTargetAsmInfo();
81 TEW = TM.getELFWriterInfo();
83 // Create the object code emitter object for this target.
84 ElfCE = new ELFCodeEmitter(*this);
86 // Inital number of sections
90 ELFWriter::~ELFWriter() {
94 // doInitialization - Emit the file header and all of the global variables for
95 // the module to the ELF file.
96 bool ELFWriter::doInitialization(Module &M) {
97 Mang = new Mangler(M);
101 // Fields e_shnum e_shstrndx are only known after all section have
102 // been emitted. They locations in the ouput buffer are recorded so
103 // to be patched up later.
107 // emitWord method behaves differently for ELF32 and ELF64, writing
108 // 4 bytes in the former and 8 in the last for *_off and *_addr elf types
110 ElfHdr.emitByte(0x7f); // e_ident[EI_MAG0]
111 ElfHdr.emitByte('E'); // e_ident[EI_MAG1]
112 ElfHdr.emitByte('L'); // e_ident[EI_MAG2]
113 ElfHdr.emitByte('F'); // e_ident[EI_MAG3]
115 ElfHdr.emitByte(TEW->getEIClass()); // e_ident[EI_CLASS]
116 ElfHdr.emitByte(TEW->getEIData()); // e_ident[EI_DATA]
117 ElfHdr.emitByte(EV_CURRENT); // e_ident[EI_VERSION]
118 ElfHdr.emitAlignment(16); // e_ident[EI_NIDENT-EI_PAD]
120 ElfHdr.emitWord16(ET_REL); // e_type
121 ElfHdr.emitWord16(TEW->getEMachine()); // e_machine = target
122 ElfHdr.emitWord32(EV_CURRENT); // e_version
123 ElfHdr.emitWord(0); // e_entry, no entry point in .o file
124 ElfHdr.emitWord(0); // e_phoff, no program header for .o
125 ELFHdr_e_shoff_Offset = ElfHdr.size();
126 ElfHdr.emitWord(0); // e_shoff = sec hdr table off in bytes
127 ElfHdr.emitWord32(TEW->getEFlags()); // e_flags = whatever the target wants
128 ElfHdr.emitWord16(TEW->getHdrSize()); // e_ehsize = ELF header size
129 ElfHdr.emitWord16(0); // e_phentsize = prog header entry size
130 ElfHdr.emitWord16(0); // e_phnum = # prog header entries = 0
132 // e_shentsize = Section header entry size
133 ElfHdr.emitWord16(TEW->getSHdrSize());
135 // e_shnum = # of section header ents
136 ELFHdr_e_shnum_Offset = ElfHdr.size();
137 ElfHdr.emitWord16(0); // Placeholder
139 // e_shstrndx = Section # of '.shstrtab'
140 ELFHdr_e_shstrndx_Offset = ElfHdr.size();
141 ElfHdr.emitWord16(0); // Placeholder
143 // Add the null section, which is required to be first in the file.
149 // addGlobalSymbol - Add a global to be processed and to the
150 // global symbol lookup, use a zero index for non private symbols
151 // because the table index will be determined later.
152 void ELFWriter::addGlobalSymbol(const GlobalValue *GV) {
153 PendingGlobals.insert(GV);
156 // addExternalSymbol - Add the external to be processed and to the
157 // external symbol lookup, use a zero index because the symbol
158 // table index will be determined later
159 void ELFWriter::addExternalSymbol(const char *External) {
160 PendingExternals.insert(External);
161 ExtSymLookup[External] = 0;
164 // Get jump table section on the section name returned by TAI
165 ELFSection &ELFWriter::getJumpTableSection() {
166 unsigned Align = TM.getTargetData()->getPointerABIAlignment();
167 return getSection(TAI->getJumpTableDataSection(),
168 ELFSection::SHT_PROGBITS,
169 ELFSection::SHF_ALLOC, Align);
172 // Get a constant pool section based on the section name returned by TAI
173 ELFSection &ELFWriter::getConstantPoolSection(MachineConstantPoolEntry &CPE) {
175 switch (CPE.getRelocationInfo()) {
176 default: llvm_unreachable("Unknown section kind");
177 case 2: Kind = SectionKind::get(SectionKind::ReadOnlyWithRel,false); break;
179 Kind = SectionKind::get(SectionKind::ReadOnlyWithRelLocal,false);
182 switch (TM.getTargetData()->getTypeAllocSize(CPE.getType())) {
183 case 4: Kind = SectionKind::get(SectionKind::MergeableConst4,false); break;
184 case 8: Kind = SectionKind::get(SectionKind::MergeableConst8,false); break;
185 case 16: Kind = SectionKind::get(SectionKind::MergeableConst16,false);break;
186 default: Kind = SectionKind::get(SectionKind::MergeableConst,false); break;
190 const TargetLoweringObjectFile &TLOF =
191 TM.getTargetLowering()->getObjFileLowering();
193 return getSection(TLOF.getSectionForMergeableConstant(Kind)->getName(),
194 ELFSection::SHT_PROGBITS,
195 ELFSection::SHF_MERGE | ELFSection::SHF_ALLOC,
199 // Return the relocation section of section 'S'. 'RelA' is true
200 // if the relocation section contains entries with addends.
201 ELFSection &ELFWriter::getRelocSection(ELFSection &S) {
202 unsigned SectionHeaderTy = TEW->hasRelocationAddend() ?
203 ELFSection::SHT_RELA : ELFSection::SHT_REL;
204 std::string RelSName(".rel");
205 if (TEW->hasRelocationAddend())
206 RelSName.append("a");
207 RelSName.append(S.getName());
209 return getSection(RelSName, SectionHeaderTy, 0, TEW->getPrefELFAlignment());
212 // getGlobalELFVisibility - Returns the ELF specific visibility type
213 unsigned ELFWriter::getGlobalELFVisibility(const GlobalValue *GV) {
214 switch (GV->getVisibility()) {
216 llvm_unreachable("unknown visibility type");
217 case GlobalValue::DefaultVisibility:
218 return ELFSym::STV_DEFAULT;
219 case GlobalValue::HiddenVisibility:
220 return ELFSym::STV_HIDDEN;
221 case GlobalValue::ProtectedVisibility:
222 return ELFSym::STV_PROTECTED;
227 // getGlobalELFBinding - Returns the ELF specific binding type
228 unsigned ELFWriter::getGlobalELFBinding(const GlobalValue *GV) {
229 if (GV->hasInternalLinkage())
230 return ELFSym::STB_LOCAL;
232 if (GV->hasWeakLinkage())
233 return ELFSym::STB_WEAK;
235 return ELFSym::STB_GLOBAL;
238 // getGlobalELFType - Returns the ELF specific type for a global
239 unsigned ELFWriter::getGlobalELFType(const GlobalValue *GV) {
240 if (GV->isDeclaration())
241 return ELFSym::STT_NOTYPE;
243 if (isa<Function>(GV))
244 return ELFSym::STT_FUNC;
246 return ELFSym::STT_OBJECT;
249 // getElfSectionFlags - Get the ELF Section Header flags based
250 // on the flags defined in ELFTargetAsmInfo.
251 unsigned ELFWriter::getElfSectionFlags(SectionKind Kind) {
252 unsigned ElfSectionFlags = ELFSection::SHF_ALLOC;
255 ElfSectionFlags |= ELFSection::SHF_EXECINSTR;
256 if (Kind.isWriteable())
257 ElfSectionFlags |= ELFSection::SHF_WRITE;
258 if (Kind.isMergeableConst())
259 ElfSectionFlags |= ELFSection::SHF_MERGE;
260 if (Kind.isThreadLocal())
261 ElfSectionFlags |= ELFSection::SHF_TLS;
262 if (Kind.isMergeableCString())
263 ElfSectionFlags |= ELFSection::SHF_STRINGS;
265 return ElfSectionFlags;
268 // isELFUndefSym - the symbol has no section and must be placed in
269 // the symbol table with a reference to the null section.
270 static bool isELFUndefSym(const GlobalValue *GV) {
271 return GV->isDeclaration();
274 // isELFBssSym - for an undef or null value, the symbol must go to a bss
275 // section if it's not weak for linker, otherwise it's a common sym.
276 static bool isELFBssSym(const GlobalVariable *GV) {
277 const Constant *CV = GV->getInitializer();
278 return ((CV->isNullValue() || isa<UndefValue>(CV)) && !GV->isWeakForLinker());
281 // isELFCommonSym - for an undef or null value, the symbol must go to a
282 // common section if it's weak for linker, otherwise bss.
283 static bool isELFCommonSym(const GlobalVariable *GV) {
284 const Constant *CV = GV->getInitializer();
285 return ((CV->isNullValue() || isa<UndefValue>(CV)) && GV->isWeakForLinker());
288 // isELFDataSym - if the symbol is an initialized but no null constant
289 // it must go to some kind of data section gathered from TAI
290 static bool isELFDataSym(const Constant *CV) {
291 return (!(CV->isNullValue() || isa<UndefValue>(CV)));
294 // EmitGlobal - Choose the right section for global and emit it
295 void ELFWriter::EmitGlobal(const GlobalValue *GV) {
297 // Check if the referenced symbol is already emitted
298 if (GblSymLookup.find(GV) != GblSymLookup.end())
301 // If the global is a function already emited in the text section
302 // just add it to the global symbol lookup with a zero index to be
304 if (isa<Function>(GV) && !GV->isDeclaration()) {
305 GblSymLookup[GV] = 0;
309 // Handle ELF Bind, Visibility and Type for the current symbol
310 unsigned SymBind = getGlobalELFBinding(GV);
311 ELFSym *GblSym = ELFSym::getGV(GV, SymBind, getGlobalELFType(GV),
312 getGlobalELFVisibility(GV));
314 if (isELFUndefSym(GV)) {
315 GblSym->SectionIdx = ELFSection::SHN_UNDEF;
317 assert(isa<GlobalVariable>(GV) && "GV not a global variable!");
318 const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV);
320 const TargetLoweringObjectFile &TLOF =
321 TM.getTargetLowering()->getObjFileLowering();
323 // Get ELF section from TAI
324 const Section *S = TLOF.SectionForGlobal(GV, TM);
325 unsigned SectionFlags = getElfSectionFlags(S->getKind());
327 // The symbol align should update the section alignment if needed
328 const TargetData *TD = TM.getTargetData();
329 unsigned Align = TD->getPreferredAlignment(GVar);
330 unsigned Size = TD->getTypeAllocSize(GVar->getInitializer()->getType());
333 if (isELFCommonSym(GVar)) {
334 GblSym->SectionIdx = ELFSection::SHN_COMMON;
335 getSection(S->getName(), ELFSection::SHT_NOBITS, SectionFlags, 1);
337 // A new linkonce section is created for each global in the
338 // common section, the default alignment is 1 and the symbol
339 // value contains its alignment.
340 GblSym->Value = Align;
342 } else if (isELFBssSym(GVar)) {
344 getSection(S->getName(), ELFSection::SHT_NOBITS, SectionFlags);
345 GblSym->SectionIdx = ES.SectionIdx;
347 // Update the size with alignment and the next object can
348 // start in the right offset in the section
349 if (Align) ES.Size = (ES.Size + Align-1) & ~(Align-1);
350 ES.Align = std::max(ES.Align, Align);
352 // GblSym->Value should contain the virtual offset inside the section.
353 // Virtual because the BSS space is not allocated on ELF objects
354 GblSym->Value = ES.Size;
357 } else if (isELFDataSym(GV)) {
359 getSection(S->getName(), ELFSection::SHT_PROGBITS, SectionFlags);
360 GblSym->SectionIdx = ES.SectionIdx;
362 // GblSym->Value should contain the symbol offset inside the section,
363 // and all symbols should start on their required alignment boundary
364 ES.Align = std::max(ES.Align, Align);
365 GblSym->Value = (ES.size() + (Align-1)) & (-Align);
366 ES.emitAlignment(ES.Align);
368 // Emit the global to the data section 'ES'
369 EmitGlobalConstant(GVar->getInitializer(), ES);
373 if (GV->hasPrivateLinkage()) {
374 // For a private symbols, keep track of the index inside the
375 // private list since it will never go to the symbol table and
376 // won't be patched up later.
377 PrivateSyms.push_back(GblSym);
378 GblSymLookup[GV] = PrivateSyms.size()-1;
380 // Non private symbol are left with zero indices until they are patched
381 // up during the symbol table emition (where the indicies are created).
382 SymbolList.push_back(GblSym);
383 GblSymLookup[GV] = 0;
387 void ELFWriter::EmitGlobalConstantStruct(const ConstantStruct *CVS,
390 // Print the fields in successive locations. Pad to align if needed!
391 const TargetData *TD = TM.getTargetData();
392 unsigned Size = TD->getTypeAllocSize(CVS->getType());
393 const StructLayout *cvsLayout = TD->getStructLayout(CVS->getType());
394 uint64_t sizeSoFar = 0;
395 for (unsigned i = 0, e = CVS->getNumOperands(); i != e; ++i) {
396 const Constant* field = CVS->getOperand(i);
398 // Check if padding is needed and insert one or more 0s.
399 uint64_t fieldSize = TD->getTypeAllocSize(field->getType());
400 uint64_t padSize = ((i == e-1 ? Size : cvsLayout->getElementOffset(i+1))
401 - cvsLayout->getElementOffset(i)) - fieldSize;
402 sizeSoFar += fieldSize + padSize;
404 // Now print the actual field value.
405 EmitGlobalConstant(field, GblS);
407 // Insert padding - this may include padding to increase the size of the
408 // current field up to the ABI size (if the struct is not packed) as well
409 // as padding to ensure that the next field starts at the right offset.
410 for (unsigned p=0; p < padSize; p++)
413 assert(sizeSoFar == cvsLayout->getSizeInBytes() &&
414 "Layout of constant struct may be incorrect!");
417 void ELFWriter::EmitGlobalConstant(const Constant *CV, ELFSection &GblS) {
418 const TargetData *TD = TM.getTargetData();
419 unsigned Size = TD->getTypeAllocSize(CV->getType());
421 if (const ConstantArray *CVA = dyn_cast<ConstantArray>(CV)) {
422 if (CVA->isString()) {
423 std::string GblStr = CVA->getAsString();
424 GblStr.resize(GblStr.size()-1);
425 GblS.emitString(GblStr);
426 } else { // Not a string. Print the values in successive locations
427 for (unsigned i = 0, e = CVA->getNumOperands(); i != e; ++i)
428 EmitGlobalConstant(CVA->getOperand(i), GblS);
431 } else if (const ConstantStruct *CVS = dyn_cast<ConstantStruct>(CV)) {
432 EmitGlobalConstantStruct(CVS, GblS);
434 } else if (const ConstantFP *CFP = dyn_cast<ConstantFP>(CV)) {
435 uint64_t Val = CFP->getValueAPF().bitcastToAPInt().getZExtValue();
436 if (CFP->getType() == Type::DoubleTy)
437 GblS.emitWord64(Val);
438 else if (CFP->getType() == Type::FloatTy)
439 GblS.emitWord32(Val);
440 else if (CFP->getType() == Type::X86_FP80Ty) {
441 llvm_unreachable("X86_FP80Ty global emission not implemented");
442 } else if (CFP->getType() == Type::PPC_FP128Ty)
443 llvm_unreachable("PPC_FP128Ty global emission not implemented");
445 } else if (const ConstantInt *CI = dyn_cast<ConstantInt>(CV)) {
447 GblS.emitWord32(CI->getZExtValue());
449 GblS.emitWord64(CI->getZExtValue());
451 llvm_unreachable("LargeInt global emission not implemented");
453 } else if (const ConstantVector *CP = dyn_cast<ConstantVector>(CV)) {
454 const VectorType *PTy = CP->getType();
455 for (unsigned I = 0, E = PTy->getNumElements(); I < E; ++I)
456 EmitGlobalConstant(CP->getOperand(I), GblS);
458 } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(CV)) {
459 // This is a constant address for a global variable or function and
460 // therefore must be referenced using a relocation entry.
462 // Check if the referenced symbol is already emitted
463 if (GblSymLookup.find(GV) == GblSymLookup.end())
466 // Create the relocation entry for the global value
467 MachineRelocation MR =
468 MachineRelocation::getGV(GblS.getCurrentPCOffset(),
469 TEW->getAbsoluteLabelMachineRelTy(),
470 const_cast<GlobalValue*>(GV));
472 // Fill the data entry with zeros
473 for (unsigned i=0; i < Size; ++i)
476 // Add the relocation entry for the current data section
477 GblS.addRelocation(MR);
479 } else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(CV)) {
480 if (CE->getOpcode() == Instruction::BitCast) {
481 EmitGlobalConstant(CE->getOperand(0), GblS);
484 // See AsmPrinter::EmitConstantValueOnly for other ConstantExpr types
485 llvm_unreachable("Unsupported ConstantExpr type");
488 llvm_unreachable("Unknown global constant type");
492 bool ELFWriter::runOnMachineFunction(MachineFunction &MF) {
493 // Nothing to do here, this is all done through the ElfCE object above.
497 /// doFinalization - Now that the module has been completely processed, emit
498 /// the ELF file to 'O'.
499 bool ELFWriter::doFinalization(Module &M) {
500 // Emit .data section placeholder
503 // Emit .bss section placeholder
506 // Build and emit data, bss and "common" sections.
507 for (Module::global_iterator I = M.global_begin(), E = M.global_end();
511 // Emit all pending globals
512 for (PendingGblsIter I = PendingGlobals.begin(), E = PendingGlobals.end();
516 // Emit all pending externals
517 for (PendingExtsIter I = PendingExternals.begin(), E = PendingExternals.end();
519 SymbolList.push_back(ELFSym::getExtSym(*I));
521 // Emit non-executable stack note
522 if (TAI->getNonexecutableStackDirective())
523 getNonExecStackSection();
526 SymbolList.push_back(ELFSym::getFileSym());
528 // Emit a symbol for each section created until now, skip null section
529 for (unsigned i = 1, e = SectionList.size(); i < e; ++i) {
530 ELFSection &ES = *SectionList[i];
531 ELFSym *SectionSym = ELFSym::getSectionSym();
532 SectionSym->SectionIdx = ES.SectionIdx;
533 SymbolList.push_back(SectionSym);
534 ES.Sym = SymbolList.back();
538 EmitStringTable(M.getModuleIdentifier());
540 // Emit the symbol table now, if non-empty.
543 // Emit the relocation sections.
546 // Emit the sections string table.
547 EmitSectionTableStringTable();
549 // Dump the sections and section table to the .o file.
550 OutputSectionsAndSectionTable();
552 // We are done with the abstract symbols.
557 // Release the name mangler object.
558 delete Mang; Mang = 0;
562 // RelocateField - Patch relocatable field with 'Offset' in 'BO'
563 // using a 'Value' of known 'Size'
564 void ELFWriter::RelocateField(BinaryObject &BO, uint32_t Offset,
565 int64_t Value, unsigned Size) {
567 BO.fixWord32(Value, Offset);
569 BO.fixWord64(Value, Offset);
571 llvm_unreachable("don't know howto patch relocatable field");
574 /// EmitRelocations - Emit relocations
575 void ELFWriter::EmitRelocations() {
577 // True if the target uses the relocation entry to hold the addend,
578 // otherwise the addend is written directly to the relocatable field.
579 bool HasRelA = TEW->hasRelocationAddend();
581 // Create Relocation sections for each section which needs it.
582 for (unsigned i=0, e=SectionList.size(); i != e; ++i) {
583 ELFSection &S = *SectionList[i];
585 // This section does not have relocations
586 if (!S.hasRelocations()) continue;
587 ELFSection &RelSec = getRelocSection(S);
589 // 'Link' - Section hdr idx of the associated symbol table
590 // 'Info' - Section hdr idx of the section to which the relocation applies
591 ELFSection &SymTab = getSymbolTableSection();
592 RelSec.Link = SymTab.SectionIdx;
593 RelSec.Info = S.SectionIdx;
594 RelSec.EntSize = TEW->getRelocationEntrySize();
596 // Get the relocations from Section
597 std::vector<MachineRelocation> Relos = S.getRelocations();
598 for (std::vector<MachineRelocation>::iterator MRI = Relos.begin(),
599 MRE = Relos.end(); MRI != MRE; ++MRI) {
600 MachineRelocation &MR = *MRI;
602 // Relocatable field offset from the section start
603 unsigned RelOffset = MR.getMachineCodeOffset();
605 // Symbol index in the symbol table
608 // Target specific relocation field type and size
609 unsigned RelType = TEW->getRelocationType(MR.getRelocationType());
610 unsigned RelTySize = TEW->getRelocationTySize(RelType);
613 // There are several machine relocations types, and each one of
614 // them needs a different approach to retrieve the symbol table index.
615 if (MR.isGlobalValue()) {
616 const GlobalValue *G = MR.getGlobalValue();
617 SymIdx = GblSymLookup[G];
618 if (G->hasPrivateLinkage()) {
619 // If the target uses a section offset in the relocation:
620 // SymIdx + Addend = section sym for global + section offset
621 unsigned SectionIdx = PrivateSyms[SymIdx]->SectionIdx;
622 Addend = PrivateSyms[SymIdx]->Value;
623 SymIdx = SectionList[SectionIdx]->getSymbolTableIndex();
625 Addend = TEW->getDefaultAddendForRelTy(RelType);
627 } else if (MR.isExternalSymbol()) {
628 const char *ExtSym = MR.getExternalSymbol();
629 SymIdx = ExtSymLookup[ExtSym];
630 Addend = TEW->getDefaultAddendForRelTy(RelType);
632 // Get the symbol index for the section symbol
633 unsigned SectionIdx = MR.getConstantVal();
634 SymIdx = SectionList[SectionIdx]->getSymbolTableIndex();
635 Addend = (uint64_t)MR.getResultPointer();
637 // For pc relative relocations where symbols are defined in the same
638 // section they are referenced, ignore the relocation entry and patch
639 // the relocatable field with the symbol offset directly.
640 if (S.SectionIdx == SectionIdx && TEW->isPCRelativeRel(RelType)) {
641 int64_t Value = TEW->computeRelocation(Addend, RelOffset, RelType);
642 RelocateField(S, RelOffset, Value, RelTySize);
646 // Handle Jump Table Index relocation
647 if ((SectionIdx == getJumpTableSection().SectionIdx) &&
648 TEW->hasCustomJumpTableIndexRelTy()) {
649 RelType = TEW->getJumpTableIndexRelTy();
650 RelTySize = TEW->getRelocationTySize(RelType);
654 // The target without addend on the relocation symbol must be
655 // patched in the relocation place itself to contain the addend
657 RelocateField(S, RelOffset, Addend, RelTySize);
659 // Get the relocation entry and emit to the relocation section
660 ELFRelocation Rel(RelOffset, SymIdx, RelType, HasRelA, Addend);
661 EmitRelocation(RelSec, Rel, HasRelA);
666 /// EmitRelocation - Write relocation 'Rel' to the relocation section 'Rel'
667 void ELFWriter::EmitRelocation(BinaryObject &RelSec, ELFRelocation &Rel,
669 RelSec.emitWord(Rel.getOffset());
670 RelSec.emitWord(Rel.getInfo(is64Bit));
672 RelSec.emitWord(Rel.getAddend());
675 /// EmitSymbol - Write symbol 'Sym' to the symbol table 'SymbolTable'
676 void ELFWriter::EmitSymbol(BinaryObject &SymbolTable, ELFSym &Sym) {
678 SymbolTable.emitWord32(Sym.NameIdx);
679 SymbolTable.emitByte(Sym.Info);
680 SymbolTable.emitByte(Sym.Other);
681 SymbolTable.emitWord16(Sym.SectionIdx);
682 SymbolTable.emitWord64(Sym.Value);
683 SymbolTable.emitWord64(Sym.Size);
685 SymbolTable.emitWord32(Sym.NameIdx);
686 SymbolTable.emitWord32(Sym.Value);
687 SymbolTable.emitWord32(Sym.Size);
688 SymbolTable.emitByte(Sym.Info);
689 SymbolTable.emitByte(Sym.Other);
690 SymbolTable.emitWord16(Sym.SectionIdx);
694 /// EmitSectionHeader - Write section 'Section' header in 'SHdrTab'
695 /// Section Header Table
696 void ELFWriter::EmitSectionHeader(BinaryObject &SHdrTab,
697 const ELFSection &SHdr) {
698 SHdrTab.emitWord32(SHdr.NameIdx);
699 SHdrTab.emitWord32(SHdr.Type);
701 SHdrTab.emitWord64(SHdr.Flags);
702 SHdrTab.emitWord(SHdr.Addr);
703 SHdrTab.emitWord(SHdr.Offset);
704 SHdrTab.emitWord64(SHdr.Size);
705 SHdrTab.emitWord32(SHdr.Link);
706 SHdrTab.emitWord32(SHdr.Info);
707 SHdrTab.emitWord64(SHdr.Align);
708 SHdrTab.emitWord64(SHdr.EntSize);
710 SHdrTab.emitWord32(SHdr.Flags);
711 SHdrTab.emitWord(SHdr.Addr);
712 SHdrTab.emitWord(SHdr.Offset);
713 SHdrTab.emitWord32(SHdr.Size);
714 SHdrTab.emitWord32(SHdr.Link);
715 SHdrTab.emitWord32(SHdr.Info);
716 SHdrTab.emitWord32(SHdr.Align);
717 SHdrTab.emitWord32(SHdr.EntSize);
721 /// EmitStringTable - If the current symbol table is non-empty, emit the string
723 void ELFWriter::EmitStringTable(const std::string &ModuleName) {
724 if (!SymbolList.size()) return; // Empty symbol table.
725 ELFSection &StrTab = getStringTableSection();
727 // Set the zero'th symbol to a null byte, as required.
730 // Walk on the symbol list and write symbol names into the string table.
732 for (ELFSymIter I=SymbolList.begin(), E=SymbolList.end(); I != E; ++I) {
736 if (Sym.isGlobalValue())
737 // Use the name mangler to uniquify the LLVM symbol.
738 Name.append(Mang->getMangledName(Sym.getGlobalValue()));
739 else if (Sym.isExternalSym())
740 Name.append(Sym.getExternalSymbol());
741 else if (Sym.isFileType())
742 Name.append(ModuleName);
748 StrTab.emitString(Name);
750 // Keep track of the number of bytes emitted to this section.
751 Index += Name.size()+1;
754 assert(Index == StrTab.size());
758 // SortSymbols - On the symbol table local symbols must come before
759 // all other symbols with non-local bindings. The return value is
760 // the position of the first non local symbol.
761 unsigned ELFWriter::SortSymbols() {
762 unsigned FirstNonLocalSymbol;
763 std::vector<ELFSym*> LocalSyms, OtherSyms;
765 for (ELFSymIter I=SymbolList.begin(), E=SymbolList.end(); I != E; ++I) {
766 if ((*I)->isLocalBind())
767 LocalSyms.push_back(*I);
769 OtherSyms.push_back(*I);
772 FirstNonLocalSymbol = LocalSyms.size();
774 for (unsigned i = 0; i < FirstNonLocalSymbol; ++i)
775 SymbolList.push_back(LocalSyms[i]);
777 for (ELFSymIter I=OtherSyms.begin(), E=OtherSyms.end(); I != E; ++I)
778 SymbolList.push_back(*I);
783 return FirstNonLocalSymbol;
786 /// EmitSymbolTable - Emit the symbol table itself.
787 void ELFWriter::EmitSymbolTable() {
788 if (!SymbolList.size()) return; // Empty symbol table.
790 // Now that we have emitted the string table and know the offset into the
791 // string table of each symbol, emit the symbol table itself.
792 ELFSection &SymTab = getSymbolTableSection();
793 SymTab.Align = TEW->getPrefELFAlignment();
795 // Section Index of .strtab.
796 SymTab.Link = getStringTableSection().SectionIdx;
798 // Size of each symtab entry.
799 SymTab.EntSize = TEW->getSymTabEntrySize();
801 // The first entry in the symtab is the null symbol
802 SymbolList.insert(SymbolList.begin(), new ELFSym());
804 // Reorder the symbol table with local symbols first!
805 unsigned FirstNonLocalSymbol = SortSymbols();
807 // Emit all the symbols to the symbol table.
808 for (unsigned i = 0, e = SymbolList.size(); i < e; ++i) {
809 ELFSym &Sym = *SymbolList[i];
811 // Emit symbol to the symbol table
812 EmitSymbol(SymTab, Sym);
814 // Record the symbol table index for each symbol
815 if (Sym.isGlobalValue())
816 GblSymLookup[Sym.getGlobalValue()] = i;
817 else if (Sym.isExternalSym())
818 ExtSymLookup[Sym.getExternalSymbol()] = i;
820 // Keep track on the symbol index into the symbol table
824 // One greater than the symbol table index of the last local symbol
825 SymTab.Info = FirstNonLocalSymbol;
826 SymTab.Size = SymTab.size();
829 /// EmitSectionTableStringTable - This method adds and emits a section for the
830 /// ELF Section Table string table: the string table that holds all of the
832 void ELFWriter::EmitSectionTableStringTable() {
833 // First step: add the section for the string table to the list of sections:
834 ELFSection &SHStrTab = getSectionHeaderStringTableSection();
836 // Now that we know which section number is the .shstrtab section, update the
837 // e_shstrndx entry in the ELF header.
838 ElfHdr.fixWord16(SHStrTab.SectionIdx, ELFHdr_e_shstrndx_Offset);
840 // Set the NameIdx of each section in the string table and emit the bytes for
844 for (ELFSectionIter I=SectionList.begin(), E=SectionList.end(); I != E; ++I) {
845 ELFSection &S = *(*I);
846 // Set the index into the table. Note if we have lots of entries with
847 // common suffixes, we could memoize them here if we cared.
849 SHStrTab.emitString(S.getName());
851 // Keep track of the number of bytes emitted to this section.
852 Index += S.getName().size()+1;
855 // Set the size of .shstrtab now that we know what it is.
856 assert(Index == SHStrTab.size());
857 SHStrTab.Size = Index;
860 /// OutputSectionsAndSectionTable - Now that we have constructed the file header
861 /// and all of the sections, emit these to the ostream destination and emit the
863 void ELFWriter::OutputSectionsAndSectionTable() {
864 // Pass #1: Compute the file offset for each section.
865 size_t FileOff = ElfHdr.size(); // File header first.
867 // Adjust alignment of all section if needed, skip the null section.
868 for (unsigned i=1, e=SectionList.size(); i < e; ++i) {
869 ELFSection &ES = *SectionList[i];
875 // Update Section size
879 // Align FileOff to whatever the alignment restrictions of the section are.
881 FileOff = (FileOff+ES.Align-1) & ~(ES.Align-1);
887 // Align Section Header.
888 unsigned TableAlign = TEW->getPrefELFAlignment();
889 FileOff = (FileOff+TableAlign-1) & ~(TableAlign-1);
891 // Now that we know where all of the sections will be emitted, set the e_shnum
892 // entry in the ELF header.
893 ElfHdr.fixWord16(NumSections, ELFHdr_e_shnum_Offset);
895 // Now that we know the offset in the file of the section table, update the
896 // e_shoff address in the ELF header.
897 ElfHdr.fixWord(FileOff, ELFHdr_e_shoff_Offset);
899 // Now that we know all of the data in the file header, emit it and all of the
901 O.write((char *)&ElfHdr.getData()[0], ElfHdr.size());
902 FileOff = ElfHdr.size();
904 // Section Header Table blob
905 BinaryObject SHdrTable(isLittleEndian, is64Bit);
907 // Emit all of sections to the file and build the section header table.
908 for (ELFSectionIter I=SectionList.begin(), E=SectionList.end(); I != E; ++I) {
909 ELFSection &S = *(*I);
910 DOUT << "SectionIdx: " << S.SectionIdx << ", Name: " << S.getName()
911 << ", Size: " << S.Size << ", Offset: " << S.Offset
912 << ", SectionData Size: " << S.size() << "\n";
914 // Align FileOff to whatever the alignment restrictions of the section are.
917 for (size_t NewFileOff = (FileOff+S.Align-1) & ~(S.Align-1);
918 FileOff != NewFileOff; ++FileOff)
921 O.write((char *)&S.getData()[0], S.Size);
925 EmitSectionHeader(SHdrTable, S);
928 // Align output for the section table.
929 for (size_t NewFileOff = (FileOff+TableAlign-1) & ~(TableAlign-1);
930 FileOff != NewFileOff; ++FileOff)
933 // Emit the section table itself.
934 O.write((char *)&SHdrTable.getData()[0], SHdrTable.size());