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/MC/MCContext.h"
46 #include "llvm/MC/MCSectionELF.h"
47 #include "llvm/Target/TargetAsmInfo.h"
48 #include "llvm/Target/TargetData.h"
49 #include "llvm/Target/TargetELFWriterInfo.h"
50 #include "llvm/Target/TargetLowering.h"
51 #include "llvm/Target/TargetLoweringObjectFile.h"
52 #include "llvm/Target/TargetMachine.h"
53 #include "llvm/Support/Mangler.h"
54 #include "llvm/Support/Streams.h"
55 #include "llvm/Support/raw_ostream.h"
56 #include "llvm/Support/Debug.h"
57 #include "llvm/Support/ErrorHandling.h"
61 char ELFWriter::ID = 0;
63 /// AddELFWriter - Add the ELF writer to the function pass manager
64 ObjectCodeEmitter *llvm::AddELFWriter(PassManagerBase &PM,
67 ELFWriter *EW = new ELFWriter(O, TM);
69 return EW->getObjectCodeEmitter();
72 //===----------------------------------------------------------------------===//
73 // ELFWriter Implementation
74 //===----------------------------------------------------------------------===//
76 ELFWriter::ELFWriter(raw_ostream &o, TargetMachine &tm)
77 : MachineFunctionPass(&ID), O(o), TM(tm),
78 OutContext(*new MCContext()),
79 TLOF(TM.getTargetLowering()->getObjFileLowering()),
80 is64Bit(TM.getTargetData()->getPointerSizeInBits() == 64),
81 isLittleEndian(TM.getTargetData()->isLittleEndian()),
82 ElfHdr(isLittleEndian, is64Bit) {
84 TAI = TM.getTargetAsmInfo();
85 TEW = TM.getELFWriterInfo();
87 // Create the object code emitter object for this target.
88 ElfCE = new ELFCodeEmitter(*this);
90 // Inital number of sections
94 ELFWriter::~ELFWriter() {
99 // doInitialization - Emit the file header and all of the global variables for
100 // the module to the ELF file.
101 bool ELFWriter::doInitialization(Module &M) {
102 // Initialize TargetLoweringObjectFile.
103 const_cast<TargetLoweringObjectFile&>(TLOF).Initialize(OutContext, TM);
105 Mang = new Mangler(M);
109 // Fields e_shnum e_shstrndx are only known after all section have
110 // been emitted. They locations in the ouput buffer are recorded so
111 // to be patched up later.
115 // emitWord method behaves differently for ELF32 and ELF64, writing
116 // 4 bytes in the former and 8 in the last for *_off and *_addr elf types
118 ElfHdr.emitByte(0x7f); // e_ident[EI_MAG0]
119 ElfHdr.emitByte('E'); // e_ident[EI_MAG1]
120 ElfHdr.emitByte('L'); // e_ident[EI_MAG2]
121 ElfHdr.emitByte('F'); // e_ident[EI_MAG3]
123 ElfHdr.emitByte(TEW->getEIClass()); // e_ident[EI_CLASS]
124 ElfHdr.emitByte(TEW->getEIData()); // e_ident[EI_DATA]
125 ElfHdr.emitByte(EV_CURRENT); // e_ident[EI_VERSION]
126 ElfHdr.emitAlignment(16); // e_ident[EI_NIDENT-EI_PAD]
128 ElfHdr.emitWord16(ET_REL); // e_type
129 ElfHdr.emitWord16(TEW->getEMachine()); // e_machine = target
130 ElfHdr.emitWord32(EV_CURRENT); // e_version
131 ElfHdr.emitWord(0); // e_entry, no entry point in .o file
132 ElfHdr.emitWord(0); // e_phoff, no program header for .o
133 ELFHdr_e_shoff_Offset = ElfHdr.size();
134 ElfHdr.emitWord(0); // e_shoff = sec hdr table off in bytes
135 ElfHdr.emitWord32(TEW->getEFlags()); // e_flags = whatever the target wants
136 ElfHdr.emitWord16(TEW->getHdrSize()); // e_ehsize = ELF header size
137 ElfHdr.emitWord16(0); // e_phentsize = prog header entry size
138 ElfHdr.emitWord16(0); // e_phnum = # prog header entries = 0
140 // e_shentsize = Section header entry size
141 ElfHdr.emitWord16(TEW->getSHdrSize());
143 // e_shnum = # of section header ents
144 ELFHdr_e_shnum_Offset = ElfHdr.size();
145 ElfHdr.emitWord16(0); // Placeholder
147 // e_shstrndx = Section # of '.shstrtab'
148 ELFHdr_e_shstrndx_Offset = ElfHdr.size();
149 ElfHdr.emitWord16(0); // Placeholder
151 // Add the null section, which is required to be first in the file.
154 // The first entry in the symtab is the null symbol and the second
155 // is a local symbol containing the module/file name
156 SymbolList.push_back(new ELFSym());
157 SymbolList.push_back(ELFSym::getFileSym());
162 // AddPendingGlobalSymbol - Add a global to be processed and to
163 // the global symbol lookup, use a zero index because the table
164 // index will be determined later.
165 void ELFWriter::AddPendingGlobalSymbol(const GlobalValue *GV,
166 bool AddToLookup /* = false */) {
167 PendingGlobals.insert(GV);
169 GblSymLookup[GV] = 0;
172 // AddPendingExternalSymbol - Add the external to be processed
173 // and to the external symbol lookup, use a zero index because
174 // the symbol table index will be determined later.
175 void ELFWriter::AddPendingExternalSymbol(const char *External) {
176 PendingExternals.insert(External);
177 ExtSymLookup[External] = 0;
180 ELFSection &ELFWriter::getDataSection() {
181 const MCSectionELF *Data = (const MCSectionELF *)TLOF.getDataSection();
182 return getSection(Data->getSectionName(), Data->getType(),
183 Data->getFlags(), 4);
186 ELFSection &ELFWriter::getBSSSection() {
187 const MCSectionELF *BSS = (const MCSectionELF *)TLOF.getBSSSection();
188 return getSection(BSS->getSectionName(), BSS->getType(), BSS->getFlags(), 4);
191 // getCtorSection - Get the static constructor section
192 ELFSection &ELFWriter::getCtorSection() {
193 const MCSectionELF *Ctor = (const MCSectionELF *)TLOF.getStaticCtorSection();
194 return getSection(Ctor->getSectionName(), Ctor->getType(), Ctor->getFlags());
197 // getDtorSection - Get the static destructor section
198 ELFSection &ELFWriter::getDtorSection() {
199 const MCSectionELF *Dtor = (const MCSectionELF *)TLOF.getStaticDtorSection();
200 return getSection(Dtor->getSectionName(), Dtor->getType(), Dtor->getFlags());
203 // getTextSection - Get the text section for the specified function
204 ELFSection &ELFWriter::getTextSection(Function *F) {
205 const MCSectionELF *Text =
206 (const MCSectionELF *)TLOF.SectionForGlobal(F, Mang, TM);
207 return getSection(Text->getSectionName(), Text->getType(), Text->getFlags());
210 // getJumpTableSection - Get a read only section for constants when
211 // emitting jump tables. TODO: add PIC support
212 ELFSection &ELFWriter::getJumpTableSection() {
213 const MCSectionELF *JT =
214 (const MCSectionELF *)TLOF.getSectionForConstant(SectionKind::getReadOnly());
215 return getSection(JT->getSectionName(), JT->getType(), JT->getFlags(),
216 TM.getTargetData()->getPointerABIAlignment());
219 // getConstantPoolSection - Get a constant pool section based on the machine
220 // constant pool entry type and relocation info.
221 ELFSection &ELFWriter::getConstantPoolSection(MachineConstantPoolEntry &CPE) {
223 switch (CPE.getRelocationInfo()) {
224 default: llvm_unreachable("Unknown section kind");
225 case 2: Kind = SectionKind::getReadOnlyWithRel(); break;
227 Kind = SectionKind::getReadOnlyWithRelLocal();
230 switch (TM.getTargetData()->getTypeAllocSize(CPE.getType())) {
231 case 4: Kind = SectionKind::getMergeableConst4(); break;
232 case 8: Kind = SectionKind::getMergeableConst8(); break;
233 case 16: Kind = SectionKind::getMergeableConst16(); break;
234 default: Kind = SectionKind::getMergeableConst(); break;
238 const MCSectionELF *CPSect =
239 (const MCSectionELF *)TLOF.getSectionForConstant(Kind);
240 return getSection(CPSect->getSectionName(), CPSect->getType(),
241 CPSect->getFlags(), CPE.getAlignment());
244 // getRelocSection - Return the relocation section of section 'S'. 'RelA'
245 // is true if the relocation section contains entries with addends.
246 ELFSection &ELFWriter::getRelocSection(ELFSection &S) {
247 unsigned SectionType = TEW->hasRelocationAddend() ?
248 ELFSection::SHT_RELA : ELFSection::SHT_REL;
250 std::string SectionName(".rel");
251 if (TEW->hasRelocationAddend())
252 SectionName.append("a");
253 SectionName.append(S.getName());
255 return getSection(SectionName, SectionType, 0, TEW->getPrefELFAlignment());
258 // getGlobalELFVisibility - Returns the ELF specific visibility type
259 unsigned ELFWriter::getGlobalELFVisibility(const GlobalValue *GV) {
260 switch (GV->getVisibility()) {
262 llvm_unreachable("unknown visibility type");
263 case GlobalValue::DefaultVisibility:
264 return ELFSym::STV_DEFAULT;
265 case GlobalValue::HiddenVisibility:
266 return ELFSym::STV_HIDDEN;
267 case GlobalValue::ProtectedVisibility:
268 return ELFSym::STV_PROTECTED;
273 // getGlobalELFBinding - Returns the ELF specific binding type
274 unsigned ELFWriter::getGlobalELFBinding(const GlobalValue *GV) {
275 if (GV->hasInternalLinkage())
276 return ELFSym::STB_LOCAL;
278 if (GV->isWeakForLinker() && !GV->hasCommonLinkage())
279 return ELFSym::STB_WEAK;
281 return ELFSym::STB_GLOBAL;
284 // getGlobalELFType - Returns the ELF specific type for a global
285 unsigned ELFWriter::getGlobalELFType(const GlobalValue *GV) {
286 if (GV->isDeclaration())
287 return ELFSym::STT_NOTYPE;
289 if (isa<Function>(GV))
290 return ELFSym::STT_FUNC;
292 return ELFSym::STT_OBJECT;
295 // IsELFUndefSym - True if the global value must be marked as a symbol
296 // which points to a SHN_UNDEF section. This means that the symbol has
297 // no definition on the module.
298 static bool IsELFUndefSym(const GlobalValue *GV) {
299 return GV->isDeclaration() || (isa<Function>(GV));
302 // AddToSymbolList - Update the symbol lookup and If the symbol is
303 // private add it to PrivateSyms list, otherwise to SymbolList.
304 void ELFWriter::AddToSymbolList(ELFSym *GblSym) {
305 assert(GblSym->isGlobalValue() && "Symbol must be a global value");
307 const GlobalValue *GV = GblSym->getGlobalValue();
308 if (GV->hasPrivateLinkage()) {
309 // For a private symbols, keep track of the index inside
310 // the private list since it will never go to the symbol
311 // table and won't be patched up later.
312 PrivateSyms.push_back(GblSym);
313 GblSymLookup[GV] = PrivateSyms.size()-1;
315 // Non private symbol are left with zero indices until
316 // they are patched up during the symbol table emition
317 // (where the indicies are created).
318 SymbolList.push_back(GblSym);
319 GblSymLookup[GV] = 0;
323 // EmitGlobal - Choose the right section for global and emit it
324 void ELFWriter::EmitGlobal(const GlobalValue *GV) {
326 // Check if the referenced symbol is already emitted
327 if (GblSymLookup.find(GV) != GblSymLookup.end())
330 // Handle ELF Bind, Visibility and Type for the current symbol
331 unsigned SymBind = getGlobalELFBinding(GV);
332 unsigned SymType = getGlobalELFType(GV);
333 bool IsUndefSym = IsELFUndefSym(GV);
335 ELFSym *GblSym = IsUndefSym ? ELFSym::getUndefGV(GV, SymBind)
336 : ELFSym::getGV(GV, SymBind, SymType, getGlobalELFVisibility(GV));
339 assert(isa<GlobalVariable>(GV) && "GV not a global variable!");
340 const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV);
342 // Handle special llvm globals
343 if (EmitSpecialLLVMGlobal(GVar))
346 // Get the ELF section where this global belongs from TLOF
347 const MCSectionELF *S =
348 (const MCSectionELF *)TLOF.SectionForGlobal(GV, Mang, TM);
350 getSection(S->getSectionName(), S->getType(), S->getFlags());
351 SectionKind Kind = S->getKind();
353 // The symbol align should update the section alignment if needed
354 const TargetData *TD = TM.getTargetData();
355 unsigned Align = TD->getPreferredAlignment(GVar);
356 unsigned Size = TD->getTypeAllocSize(GVar->getInitializer()->getType());
359 if (S->IsCommon()) { // Symbol must go to a common section
360 GblSym->SectionIdx = ELFSection::SHN_COMMON;
362 // A new linkonce section is created for each global in the
363 // common section, the default alignment is 1 and the symbol
364 // value contains its alignment.
366 GblSym->Value = Align;
368 } else if (Kind.isBSS() || Kind.isThreadBSS()) { // Symbol goes to BSS.
369 GblSym->SectionIdx = ES.SectionIdx;
371 // Update the size with alignment and the next object can
372 // start in the right offset in the section
373 if (Align) ES.Size = (ES.Size + Align-1) & ~(Align-1);
374 ES.Align = std::max(ES.Align, Align);
376 // GblSym->Value should contain the virtual offset inside the section.
377 // Virtual because the BSS space is not allocated on ELF objects
378 GblSym->Value = ES.Size;
381 } else { // The symbol must go to some kind of data section
382 GblSym->SectionIdx = ES.SectionIdx;
384 // GblSym->Value should contain the symbol offset inside the section,
385 // and all symbols should start on their required alignment boundary
386 ES.Align = std::max(ES.Align, Align);
387 ES.emitAlignment(Align);
388 GblSym->Value = ES.size();
390 // Emit the global to the data section 'ES'
391 EmitGlobalConstant(GVar->getInitializer(), ES);
395 AddToSymbolList(GblSym);
398 void ELFWriter::EmitGlobalConstantStruct(const ConstantStruct *CVS,
401 // Print the fields in successive locations. Pad to align if needed!
402 const TargetData *TD = TM.getTargetData();
403 unsigned Size = TD->getTypeAllocSize(CVS->getType());
404 const StructLayout *cvsLayout = TD->getStructLayout(CVS->getType());
405 uint64_t sizeSoFar = 0;
406 for (unsigned i = 0, e = CVS->getNumOperands(); i != e; ++i) {
407 const Constant* field = CVS->getOperand(i);
409 // Check if padding is needed and insert one or more 0s.
410 uint64_t fieldSize = TD->getTypeAllocSize(field->getType());
411 uint64_t padSize = ((i == e-1 ? Size : cvsLayout->getElementOffset(i+1))
412 - cvsLayout->getElementOffset(i)) - fieldSize;
413 sizeSoFar += fieldSize + padSize;
415 // Now print the actual field value.
416 EmitGlobalConstant(field, GblS);
418 // Insert padding - this may include padding to increase the size of the
419 // current field up to the ABI size (if the struct is not packed) as well
420 // as padding to ensure that the next field starts at the right offset.
421 GblS.emitZeros(padSize);
423 assert(sizeSoFar == cvsLayout->getSizeInBytes() &&
424 "Layout of constant struct may be incorrect!");
427 void ELFWriter::EmitGlobalConstant(const Constant *CV, ELFSection &GblS) {
428 const TargetData *TD = TM.getTargetData();
429 unsigned Size = TD->getTypeAllocSize(CV->getType());
431 if (const ConstantArray *CVA = dyn_cast<ConstantArray>(CV)) {
432 for (unsigned i = 0, e = CVA->getNumOperands(); i != e; ++i)
433 EmitGlobalConstant(CVA->getOperand(i), GblS);
435 } else if (isa<ConstantAggregateZero>(CV)) {
436 GblS.emitZeros(Size);
438 } else if (const ConstantStruct *CVS = dyn_cast<ConstantStruct>(CV)) {
439 EmitGlobalConstantStruct(CVS, GblS);
441 } else if (const ConstantFP *CFP = dyn_cast<ConstantFP>(CV)) {
442 APInt Val = CFP->getValueAPF().bitcastToAPInt();
443 if (CFP->getType() == Type::DoubleTy)
444 GblS.emitWord64(Val.getZExtValue());
445 else if (CFP->getType() == Type::FloatTy)
446 GblS.emitWord32(Val.getZExtValue());
447 else if (CFP->getType() == Type::X86_FP80Ty) {
448 unsigned PadSize = TD->getTypeAllocSize(Type::X86_FP80Ty)-
449 TD->getTypeStoreSize(Type::X86_FP80Ty);
450 GblS.emitWordFP80(Val.getRawData(), PadSize);
451 } else if (CFP->getType() == Type::PPC_FP128Ty)
452 llvm_unreachable("PPC_FP128Ty global emission not implemented");
454 } else if (const ConstantInt *CI = dyn_cast<ConstantInt>(CV)) {
456 GblS.emitByte(CI->getZExtValue());
458 GblS.emitWord16(CI->getZExtValue());
460 GblS.emitWord32(CI->getZExtValue());
462 EmitGlobalConstantLargeInt(CI, GblS);
464 } else if (const ConstantVector *CP = dyn_cast<ConstantVector>(CV)) {
465 const VectorType *PTy = CP->getType();
466 for (unsigned I = 0, E = PTy->getNumElements(); I < E; ++I)
467 EmitGlobalConstant(CP->getOperand(I), GblS);
469 } else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(CV)) {
470 // Resolve a constant expression which returns a (Constant, Offset)
471 // pair. If 'Res.first' is a GlobalValue, emit a relocation with
472 // the offset 'Res.second', otherwise emit a global constant like
473 // it is always done for not contant expression types.
474 CstExprResTy Res = ResolveConstantExpr(CE);
475 const Constant *Op = Res.first;
477 if (isa<GlobalValue>(Op))
478 EmitGlobalDataRelocation(cast<const GlobalValue>(Op),
479 TD->getTypeAllocSize(Op->getType()),
482 EmitGlobalConstant(Op, GblS);
485 } else if (CV->getType()->getTypeID() == Type::PointerTyID) {
486 // Fill the data entry with zeros or emit a relocation entry
487 if (isa<ConstantPointerNull>(CV))
488 GblS.emitZeros(Size);
490 EmitGlobalDataRelocation(cast<const GlobalValue>(CV),
493 } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(CV)) {
494 // This is a constant address for a global variable or function and
495 // therefore must be referenced using a relocation entry.
496 EmitGlobalDataRelocation(GV, Size, GblS);
501 raw_string_ostream ErrorMsg(msg);
502 ErrorMsg << "Constant unimp for type: " << *CV->getType();
503 llvm_report_error(ErrorMsg.str());
506 // ResolveConstantExpr - Resolve the constant expression until it stop
507 // yielding other constant expressions.
508 CstExprResTy ELFWriter::ResolveConstantExpr(const Constant *CV) {
509 const TargetData *TD = TM.getTargetData();
511 // There ins't constant expression inside others anymore
512 if (!isa<ConstantExpr>(CV))
513 return std::make_pair(CV, 0);
515 const ConstantExpr *CE = dyn_cast<ConstantExpr>(CV);
516 switch (CE->getOpcode()) {
517 case Instruction::BitCast:
518 return ResolveConstantExpr(CE->getOperand(0));
520 case Instruction::GetElementPtr: {
521 const Constant *ptrVal = CE->getOperand(0);
522 SmallVector<Value*, 8> idxVec(CE->op_begin()+1, CE->op_end());
523 int64_t Offset = TD->getIndexedOffset(ptrVal->getType(), &idxVec[0],
525 return std::make_pair(ptrVal, Offset);
527 case Instruction::IntToPtr: {
528 Constant *Op = CE->getOperand(0);
529 Op = ConstantExpr::getIntegerCast(Op, TD->getIntPtrType(), false/*ZExt*/);
530 return ResolveConstantExpr(Op);
532 case Instruction::PtrToInt: {
533 Constant *Op = CE->getOperand(0);
534 const Type *Ty = CE->getType();
536 // We can emit the pointer value into this slot if the slot is an
537 // integer slot greater or equal to the size of the pointer.
538 if (TD->getTypeAllocSize(Ty) == TD->getTypeAllocSize(Op->getType()))
539 return ResolveConstantExpr(Op);
541 llvm_unreachable("Integer size less then pointer size");
543 case Instruction::Add:
544 case Instruction::Sub: {
545 // Only handle cases where there's a constant expression with GlobalValue
546 // as first operand and ConstantInt as second, which are the cases we can
547 // solve direclty using a relocation entry. GlobalValue=Op0, CstInt=Op1
548 // 1) Instruction::Add => (global) + CstInt
549 // 2) Instruction::Sub => (global) + -CstInt
550 const Constant *Op0 = CE->getOperand(0);
551 const Constant *Op1 = CE->getOperand(1);
552 assert(isa<ConstantInt>(Op1) && "Op1 must be a ConstantInt");
554 CstExprResTy Res = ResolveConstantExpr(Op0);
555 assert(isa<GlobalValue>(Res.first) && "Op0 must be a GlobalValue");
557 const APInt &RHS = cast<ConstantInt>(Op1)->getValue();
558 switch (CE->getOpcode()) {
559 case Instruction::Add:
560 return std::make_pair(Res.first, RHS.getSExtValue());
561 case Instruction::Sub:
562 return std::make_pair(Res.first, (-RHS).getSExtValue());
567 std::string msg(CE->getOpcodeName());
568 raw_string_ostream ErrorMsg(msg);
569 ErrorMsg << ": Unsupported ConstantExpr type";
570 llvm_report_error(ErrorMsg.str());
572 return std::make_pair(CV, 0); // silence warning
575 void ELFWriter::EmitGlobalDataRelocation(const GlobalValue *GV, unsigned Size,
576 ELFSection &GblS, int64_t Offset) {
577 // Create the relocation entry for the global value
578 MachineRelocation MR =
579 MachineRelocation::getGV(GblS.getCurrentPCOffset(),
580 TEW->getAbsoluteLabelMachineRelTy(),
581 const_cast<GlobalValue*>(GV),
584 // Fill the data entry with zeros
585 GblS.emitZeros(Size);
587 // Add the relocation entry for the current data section
588 GblS.addRelocation(MR);
591 void ELFWriter::EmitGlobalConstantLargeInt(const ConstantInt *CI,
593 const TargetData *TD = TM.getTargetData();
594 unsigned BitWidth = CI->getBitWidth();
595 assert(isPowerOf2_32(BitWidth) &&
596 "Non-power-of-2-sized integers not handled!");
598 const uint64_t *RawData = CI->getValue().getRawData();
600 for (unsigned i = 0, e = BitWidth / 64; i != e; ++i) {
601 Val = (TD->isBigEndian()) ? RawData[e - i - 1] : RawData[i];
606 /// EmitSpecialLLVMGlobal - Check to see if the specified global is a
607 /// special global used by LLVM. If so, emit it and return true, otherwise
608 /// do nothing and return false.
609 bool ELFWriter::EmitSpecialLLVMGlobal(const GlobalVariable *GV) {
610 if (GV->getName() == "llvm.used")
611 llvm_unreachable("not implemented yet");
613 // Ignore debug and non-emitted data. This handles llvm.compiler.used.
614 if (GV->getSection() == "llvm.metadata" ||
615 GV->hasAvailableExternallyLinkage())
618 if (!GV->hasAppendingLinkage()) return false;
620 assert(GV->hasInitializer() && "Not a special LLVM global!");
622 const TargetData *TD = TM.getTargetData();
623 unsigned Align = TD->getPointerPrefAlignment();
624 if (GV->getName() == "llvm.global_ctors") {
625 ELFSection &Ctor = getCtorSection();
626 Ctor.emitAlignment(Align);
627 EmitXXStructorList(GV->getInitializer(), Ctor);
631 if (GV->getName() == "llvm.global_dtors") {
632 ELFSection &Dtor = getDtorSection();
633 Dtor.emitAlignment(Align);
634 EmitXXStructorList(GV->getInitializer(), Dtor);
641 /// EmitXXStructorList - Emit the ctor or dtor list. This just emits out the
642 /// function pointers, ignoring the init priority.
643 void ELFWriter::EmitXXStructorList(Constant *List, ELFSection &Xtor) {
644 // Should be an array of '{ int, void ()* }' structs. The first value is the
645 // init priority, which we ignore.
646 if (!isa<ConstantArray>(List)) return;
647 ConstantArray *InitList = cast<ConstantArray>(List);
648 for (unsigned i = 0, e = InitList->getNumOperands(); i != e; ++i)
649 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(InitList->getOperand(i))){
650 if (CS->getNumOperands() != 2) return; // Not array of 2-element structs.
652 if (CS->getOperand(1)->isNullValue())
653 return; // Found a null terminator, exit printing.
654 // Emit the function pointer.
655 EmitGlobalConstant(CS->getOperand(1), Xtor);
659 bool ELFWriter::runOnMachineFunction(MachineFunction &MF) {
660 // Nothing to do here, this is all done through the ElfCE object above.
664 /// doFinalization - Now that the module has been completely processed, emit
665 /// the ELF file to 'O'.
666 bool ELFWriter::doFinalization(Module &M) {
667 // Emit .data section placeholder
670 // Emit .bss section placeholder
673 // Build and emit data, bss and "common" sections.
674 for (Module::global_iterator I = M.global_begin(), E = M.global_end();
678 // Emit all pending globals
679 for (PendingGblsIter I = PendingGlobals.begin(), E = PendingGlobals.end();
683 // Emit all pending externals
684 for (PendingExtsIter I = PendingExternals.begin(), E = PendingExternals.end();
686 SymbolList.push_back(ELFSym::getExtSym(*I));
688 // Emit non-executable stack note
689 if (TAI->getNonexecutableStackDirective())
690 getNonExecStackSection();
692 // Emit a symbol for each section created until now, skip null section
693 for (unsigned i = 1, e = SectionList.size(); i < e; ++i) {
694 ELFSection &ES = *SectionList[i];
695 ELFSym *SectionSym = ELFSym::getSectionSym();
696 SectionSym->SectionIdx = ES.SectionIdx;
697 SymbolList.push_back(SectionSym);
698 ES.Sym = SymbolList.back();
702 EmitStringTable(M.getModuleIdentifier());
704 // Emit the symbol table now, if non-empty.
707 // Emit the relocation sections.
710 // Emit the sections string table.
711 EmitSectionTableStringTable();
713 // Dump the sections and section table to the .o file.
714 OutputSectionsAndSectionTable();
716 // We are done with the abstract symbols.
721 // Release the name mangler object.
722 delete Mang; Mang = 0;
726 // RelocateField - Patch relocatable field with 'Offset' in 'BO'
727 // using a 'Value' of known 'Size'
728 void ELFWriter::RelocateField(BinaryObject &BO, uint32_t Offset,
729 int64_t Value, unsigned Size) {
731 BO.fixWord32(Value, Offset);
733 BO.fixWord64(Value, Offset);
735 llvm_unreachable("don't know howto patch relocatable field");
738 /// EmitRelocations - Emit relocations
739 void ELFWriter::EmitRelocations() {
741 // True if the target uses the relocation entry to hold the addend,
742 // otherwise the addend is written directly to the relocatable field.
743 bool HasRelA = TEW->hasRelocationAddend();
745 // Create Relocation sections for each section which needs it.
746 for (unsigned i=0, e=SectionList.size(); i != e; ++i) {
747 ELFSection &S = *SectionList[i];
749 // This section does not have relocations
750 if (!S.hasRelocations()) continue;
751 ELFSection &RelSec = getRelocSection(S);
753 // 'Link' - Section hdr idx of the associated symbol table
754 // 'Info' - Section hdr idx of the section to which the relocation applies
755 ELFSection &SymTab = getSymbolTableSection();
756 RelSec.Link = SymTab.SectionIdx;
757 RelSec.Info = S.SectionIdx;
758 RelSec.EntSize = TEW->getRelocationEntrySize();
760 // Get the relocations from Section
761 std::vector<MachineRelocation> Relos = S.getRelocations();
762 for (std::vector<MachineRelocation>::iterator MRI = Relos.begin(),
763 MRE = Relos.end(); MRI != MRE; ++MRI) {
764 MachineRelocation &MR = *MRI;
766 // Relocatable field offset from the section start
767 unsigned RelOffset = MR.getMachineCodeOffset();
769 // Symbol index in the symbol table
772 // Target specific relocation field type and size
773 unsigned RelType = TEW->getRelocationType(MR.getRelocationType());
774 unsigned RelTySize = TEW->getRelocationTySize(RelType);
777 // There are several machine relocations types, and each one of
778 // them needs a different approach to retrieve the symbol table index.
779 if (MR.isGlobalValue()) {
780 const GlobalValue *G = MR.getGlobalValue();
781 int64_t GlobalOffset = MR.getConstantVal();
782 SymIdx = GblSymLookup[G];
783 if (G->hasPrivateLinkage()) {
784 // If the target uses a section offset in the relocation:
785 // SymIdx + Addend = section sym for global + section offset
786 unsigned SectionIdx = PrivateSyms[SymIdx]->SectionIdx;
787 Addend = PrivateSyms[SymIdx]->Value + GlobalOffset;
788 SymIdx = SectionList[SectionIdx]->getSymbolTableIndex();
790 Addend = TEW->getDefaultAddendForRelTy(RelType, GlobalOffset);
792 } else if (MR.isExternalSymbol()) {
793 const char *ExtSym = MR.getExternalSymbol();
794 SymIdx = ExtSymLookup[ExtSym];
795 Addend = TEW->getDefaultAddendForRelTy(RelType);
797 // Get the symbol index for the section symbol
798 unsigned SectionIdx = MR.getConstantVal();
799 SymIdx = SectionList[SectionIdx]->getSymbolTableIndex();
801 // The symbol offset inside the section
802 int64_t SymOffset = (int64_t)MR.getResultPointer();
804 // For pc relative relocations where symbols are defined in the same
805 // section they are referenced, ignore the relocation entry and patch
806 // the relocatable field with the symbol offset directly.
807 if (S.SectionIdx == SectionIdx && TEW->isPCRelativeRel(RelType)) {
808 int64_t Value = TEW->computeRelocation(SymOffset, RelOffset, RelType);
809 RelocateField(S, RelOffset, Value, RelTySize);
813 Addend = TEW->getDefaultAddendForRelTy(RelType, SymOffset);
816 // The target without addend on the relocation symbol must be
817 // patched in the relocation place itself to contain the addend
818 // otherwise write zeros to make sure there is no garbage there
819 RelocateField(S, RelOffset, HasRelA ? 0 : Addend, RelTySize);
821 // Get the relocation entry and emit to the relocation section
822 ELFRelocation Rel(RelOffset, SymIdx, RelType, HasRelA, Addend);
823 EmitRelocation(RelSec, Rel, HasRelA);
828 /// EmitRelocation - Write relocation 'Rel' to the relocation section 'Rel'
829 void ELFWriter::EmitRelocation(BinaryObject &RelSec, ELFRelocation &Rel,
831 RelSec.emitWord(Rel.getOffset());
832 RelSec.emitWord(Rel.getInfo(is64Bit));
834 RelSec.emitWord(Rel.getAddend());
837 /// EmitSymbol - Write symbol 'Sym' to the symbol table 'SymbolTable'
838 void ELFWriter::EmitSymbol(BinaryObject &SymbolTable, ELFSym &Sym) {
840 SymbolTable.emitWord32(Sym.NameIdx);
841 SymbolTable.emitByte(Sym.Info);
842 SymbolTable.emitByte(Sym.Other);
843 SymbolTable.emitWord16(Sym.SectionIdx);
844 SymbolTable.emitWord64(Sym.Value);
845 SymbolTable.emitWord64(Sym.Size);
847 SymbolTable.emitWord32(Sym.NameIdx);
848 SymbolTable.emitWord32(Sym.Value);
849 SymbolTable.emitWord32(Sym.Size);
850 SymbolTable.emitByte(Sym.Info);
851 SymbolTable.emitByte(Sym.Other);
852 SymbolTable.emitWord16(Sym.SectionIdx);
856 /// EmitSectionHeader - Write section 'Section' header in 'SHdrTab'
857 /// Section Header Table
858 void ELFWriter::EmitSectionHeader(BinaryObject &SHdrTab,
859 const ELFSection &SHdr) {
860 SHdrTab.emitWord32(SHdr.NameIdx);
861 SHdrTab.emitWord32(SHdr.Type);
863 SHdrTab.emitWord64(SHdr.Flags);
864 SHdrTab.emitWord(SHdr.Addr);
865 SHdrTab.emitWord(SHdr.Offset);
866 SHdrTab.emitWord64(SHdr.Size);
867 SHdrTab.emitWord32(SHdr.Link);
868 SHdrTab.emitWord32(SHdr.Info);
869 SHdrTab.emitWord64(SHdr.Align);
870 SHdrTab.emitWord64(SHdr.EntSize);
872 SHdrTab.emitWord32(SHdr.Flags);
873 SHdrTab.emitWord(SHdr.Addr);
874 SHdrTab.emitWord(SHdr.Offset);
875 SHdrTab.emitWord32(SHdr.Size);
876 SHdrTab.emitWord32(SHdr.Link);
877 SHdrTab.emitWord32(SHdr.Info);
878 SHdrTab.emitWord32(SHdr.Align);
879 SHdrTab.emitWord32(SHdr.EntSize);
883 /// EmitStringTable - If the current symbol table is non-empty, emit the string
885 void ELFWriter::EmitStringTable(const std::string &ModuleName) {
886 if (!SymbolList.size()) return; // Empty symbol table.
887 ELFSection &StrTab = getStringTableSection();
889 // Set the zero'th symbol to a null byte, as required.
892 // Walk on the symbol list and write symbol names into the string table.
894 for (ELFSymIter I=SymbolList.begin(), E=SymbolList.end(); I != E; ++I) {
898 if (Sym.isGlobalValue())
899 Name.append(Mang->getMangledName(Sym.getGlobalValue()));
900 else if (Sym.isExternalSym())
901 Name.append(Sym.getExternalSymbol());
902 else if (Sym.isFileType())
903 Name.append(ModuleName);
909 StrTab.emitString(Name);
911 // Keep track of the number of bytes emitted to this section.
912 Index += Name.size()+1;
915 assert(Index == StrTab.size());
919 // SortSymbols - On the symbol table local symbols must come before
920 // all other symbols with non-local bindings. The return value is
921 // the position of the first non local symbol.
922 unsigned ELFWriter::SortSymbols() {
923 unsigned FirstNonLocalSymbol;
924 std::vector<ELFSym*> LocalSyms, OtherSyms;
926 for (ELFSymIter I=SymbolList.begin(), E=SymbolList.end(); I != E; ++I) {
927 if ((*I)->isLocalBind())
928 LocalSyms.push_back(*I);
930 OtherSyms.push_back(*I);
933 FirstNonLocalSymbol = LocalSyms.size();
935 for (unsigned i = 0; i < FirstNonLocalSymbol; ++i)
936 SymbolList.push_back(LocalSyms[i]);
938 for (ELFSymIter I=OtherSyms.begin(), E=OtherSyms.end(); I != E; ++I)
939 SymbolList.push_back(*I);
944 return FirstNonLocalSymbol;
947 /// EmitSymbolTable - Emit the symbol table itself.
948 void ELFWriter::EmitSymbolTable() {
949 if (!SymbolList.size()) return; // Empty symbol table.
951 // Now that we have emitted the string table and know the offset into the
952 // string table of each symbol, emit the symbol table itself.
953 ELFSection &SymTab = getSymbolTableSection();
954 SymTab.Align = TEW->getPrefELFAlignment();
956 // Section Index of .strtab.
957 SymTab.Link = getStringTableSection().SectionIdx;
959 // Size of each symtab entry.
960 SymTab.EntSize = TEW->getSymTabEntrySize();
962 // Reorder the symbol table with local symbols first!
963 unsigned FirstNonLocalSymbol = SortSymbols();
965 // Emit all the symbols to the symbol table.
966 for (unsigned i = 0, e = SymbolList.size(); i < e; ++i) {
967 ELFSym &Sym = *SymbolList[i];
969 // Emit symbol to the symbol table
970 EmitSymbol(SymTab, Sym);
972 // Record the symbol table index for each symbol
973 if (Sym.isGlobalValue())
974 GblSymLookup[Sym.getGlobalValue()] = i;
975 else if (Sym.isExternalSym())
976 ExtSymLookup[Sym.getExternalSymbol()] = i;
978 // Keep track on the symbol index into the symbol table
982 // One greater than the symbol table index of the last local symbol
983 SymTab.Info = FirstNonLocalSymbol;
984 SymTab.Size = SymTab.size();
987 /// EmitSectionTableStringTable - This method adds and emits a section for the
988 /// ELF Section Table string table: the string table that holds all of the
990 void ELFWriter::EmitSectionTableStringTable() {
991 // First step: add the section for the string table to the list of sections:
992 ELFSection &SHStrTab = getSectionHeaderStringTableSection();
994 // Now that we know which section number is the .shstrtab section, update the
995 // e_shstrndx entry in the ELF header.
996 ElfHdr.fixWord16(SHStrTab.SectionIdx, ELFHdr_e_shstrndx_Offset);
998 // Set the NameIdx of each section in the string table and emit the bytes for
1002 for (ELFSectionIter I=SectionList.begin(), E=SectionList.end(); I != E; ++I) {
1003 ELFSection &S = *(*I);
1004 // Set the index into the table. Note if we have lots of entries with
1005 // common suffixes, we could memoize them here if we cared.
1007 SHStrTab.emitString(S.getName());
1009 // Keep track of the number of bytes emitted to this section.
1010 Index += S.getName().size()+1;
1013 // Set the size of .shstrtab now that we know what it is.
1014 assert(Index == SHStrTab.size());
1015 SHStrTab.Size = Index;
1018 /// OutputSectionsAndSectionTable - Now that we have constructed the file header
1019 /// and all of the sections, emit these to the ostream destination and emit the
1021 void ELFWriter::OutputSectionsAndSectionTable() {
1022 // Pass #1: Compute the file offset for each section.
1023 size_t FileOff = ElfHdr.size(); // File header first.
1025 // Adjust alignment of all section if needed, skip the null section.
1026 for (unsigned i=1, e=SectionList.size(); i < e; ++i) {
1027 ELFSection &ES = *SectionList[i];
1029 ES.Offset = FileOff;
1033 // Update Section size
1035 ES.Size = ES.size();
1037 // Align FileOff to whatever the alignment restrictions of the section are.
1039 FileOff = (FileOff+ES.Align-1) & ~(ES.Align-1);
1041 ES.Offset = FileOff;
1045 // Align Section Header.
1046 unsigned TableAlign = TEW->getPrefELFAlignment();
1047 FileOff = (FileOff+TableAlign-1) & ~(TableAlign-1);
1049 // Now that we know where all of the sections will be emitted, set the e_shnum
1050 // entry in the ELF header.
1051 ElfHdr.fixWord16(NumSections, ELFHdr_e_shnum_Offset);
1053 // Now that we know the offset in the file of the section table, update the
1054 // e_shoff address in the ELF header.
1055 ElfHdr.fixWord(FileOff, ELFHdr_e_shoff_Offset);
1057 // Now that we know all of the data in the file header, emit it and all of the
1059 O.write((char *)&ElfHdr.getData()[0], ElfHdr.size());
1060 FileOff = ElfHdr.size();
1062 // Section Header Table blob
1063 BinaryObject SHdrTable(isLittleEndian, is64Bit);
1065 // Emit all of sections to the file and build the section header table.
1066 for (ELFSectionIter I=SectionList.begin(), E=SectionList.end(); I != E; ++I) {
1067 ELFSection &S = *(*I);
1068 DOUT << "SectionIdx: " << S.SectionIdx << ", Name: " << S.getName()
1069 << ", Size: " << S.Size << ", Offset: " << S.Offset
1070 << ", SectionData Size: " << S.size() << "\n";
1072 // Align FileOff to whatever the alignment restrictions of the section are.
1075 for (size_t NewFileOff = (FileOff+S.Align-1) & ~(S.Align-1);
1076 FileOff != NewFileOff; ++FileOff)
1079 O.write((char *)&S.getData()[0], S.Size);
1083 EmitSectionHeader(SHdrTable, S);
1086 // Align output for the section table.
1087 for (size_t NewFileOff = (FileOff+TableAlign-1) & ~(TableAlign-1);
1088 FileOff != NewFileOff; ++FileOff)
1091 // Emit the section table itself.
1092 O.write((char *)&SHdrTable.getData()[0], SHdrTable.size());