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/MachineCodeEmitter.h"
41 #include "llvm/CodeGen/ObjectCodeEmitter.h"
42 #include "llvm/CodeGen/MachineCodeEmitter.h"
43 #include "llvm/CodeGen/MachineConstantPool.h"
44 #include "llvm/MC/MCContext.h"
45 #include "llvm/MC/MCSectionELF.h"
46 #include "llvm/MC/MCAsmInfo.h"
47 #include "llvm/Target/Mangler.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/Debug.h"
54 #include "llvm/Support/ErrorHandling.h"
55 #include "llvm/Support/raw_ostream.h"
56 #include "llvm/ADT/SmallString.h"
59 char ELFWriter::ID = 0;
61 //===----------------------------------------------------------------------===//
62 // ELFWriter Implementation
63 //===----------------------------------------------------------------------===//
65 ELFWriter::ELFWriter(raw_ostream &o, TargetMachine &tm)
66 : MachineFunctionPass(&ID), O(o), TM(tm),
67 OutContext(*new MCContext(*TM.getMCAsmInfo())),
68 TLOF(TM.getTargetLowering()->getObjFileLowering()),
69 is64Bit(TM.getTargetData()->getPointerSizeInBits() == 64),
70 isLittleEndian(TM.getTargetData()->isLittleEndian()),
71 ElfHdr(isLittleEndian, is64Bit) {
73 MAI = TM.getMCAsmInfo();
74 TEW = TM.getELFWriterInfo();
76 // Create the object code emitter object for this target.
77 ElfCE = new ELFCodeEmitter(*this);
79 // Inital number of sections
83 ELFWriter::~ELFWriter() {
87 while(!SymbolList.empty()) {
88 delete SymbolList.back();
89 SymbolList.pop_back();
92 while(!PrivateSyms.empty()) {
93 delete PrivateSyms.back();
94 PrivateSyms.pop_back();
97 while(!SectionList.empty()) {
98 delete SectionList.back();
99 SectionList.pop_back();
102 // Release the name mangler object.
103 delete Mang; Mang = 0;
106 // doInitialization - Emit the file header and all of the global variables for
107 // the module to the ELF file.
108 bool ELFWriter::doInitialization(Module &M) {
109 // Initialize TargetLoweringObjectFile.
110 const_cast<TargetLoweringObjectFile&>(TLOF).Initialize(OutContext, TM);
112 Mang = new Mangler(OutContext, *TM.getTargetData());
116 // Fields e_shnum e_shstrndx are only known after all section have
117 // been emitted. They locations in the ouput buffer are recorded so
118 // to be patched up later.
122 // emitWord method behaves differently for ELF32 and ELF64, writing
123 // 4 bytes in the former and 8 in the last for *_off and *_addr elf types
125 ElfHdr.emitByte(0x7f); // e_ident[EI_MAG0]
126 ElfHdr.emitByte('E'); // e_ident[EI_MAG1]
127 ElfHdr.emitByte('L'); // e_ident[EI_MAG2]
128 ElfHdr.emitByte('F'); // e_ident[EI_MAG3]
130 ElfHdr.emitByte(TEW->getEIClass()); // e_ident[EI_CLASS]
131 ElfHdr.emitByte(TEW->getEIData()); // e_ident[EI_DATA]
132 ElfHdr.emitByte(EV_CURRENT); // e_ident[EI_VERSION]
133 ElfHdr.emitAlignment(16); // e_ident[EI_NIDENT-EI_PAD]
135 ElfHdr.emitWord16(ET_REL); // e_type
136 ElfHdr.emitWord16(TEW->getEMachine()); // e_machine = target
137 ElfHdr.emitWord32(EV_CURRENT); // e_version
138 ElfHdr.emitWord(0); // e_entry, no entry point in .o file
139 ElfHdr.emitWord(0); // e_phoff, no program header for .o
140 ELFHdr_e_shoff_Offset = ElfHdr.size();
141 ElfHdr.emitWord(0); // e_shoff = sec hdr table off in bytes
142 ElfHdr.emitWord32(TEW->getEFlags()); // e_flags = whatever the target wants
143 ElfHdr.emitWord16(TEW->getHdrSize()); // e_ehsize = ELF header size
144 ElfHdr.emitWord16(0); // e_phentsize = prog header entry size
145 ElfHdr.emitWord16(0); // e_phnum = # prog header entries = 0
147 // e_shentsize = Section header entry size
148 ElfHdr.emitWord16(TEW->getSHdrSize());
150 // e_shnum = # of section header ents
151 ELFHdr_e_shnum_Offset = ElfHdr.size();
152 ElfHdr.emitWord16(0); // Placeholder
154 // e_shstrndx = Section # of '.shstrtab'
155 ELFHdr_e_shstrndx_Offset = ElfHdr.size();
156 ElfHdr.emitWord16(0); // Placeholder
158 // Add the null section, which is required to be first in the file.
161 // The first entry in the symtab is the null symbol and the second
162 // is a local symbol containing the module/file name
163 SymbolList.push_back(new ELFSym());
164 SymbolList.push_back(ELFSym::getFileSym());
169 // AddPendingGlobalSymbol - Add a global to be processed and to
170 // the global symbol lookup, use a zero index because the table
171 // index will be determined later.
172 void ELFWriter::AddPendingGlobalSymbol(const GlobalValue *GV,
173 bool AddToLookup /* = false */) {
174 PendingGlobals.insert(GV);
176 GblSymLookup[GV] = 0;
179 // AddPendingExternalSymbol - Add the external to be processed
180 // and to the external symbol lookup, use a zero index because
181 // the symbol table index will be determined later.
182 void ELFWriter::AddPendingExternalSymbol(const char *External) {
183 PendingExternals.insert(External);
184 ExtSymLookup[External] = 0;
187 ELFSection &ELFWriter::getDataSection() {
188 const MCSectionELF *Data = (const MCSectionELF *)TLOF.getDataSection();
189 return getSection(Data->getSectionName(), Data->getType(),
190 Data->getFlags(), 4);
193 ELFSection &ELFWriter::getBSSSection() {
194 const MCSectionELF *BSS = (const MCSectionELF *)TLOF.getBSSSection();
195 return getSection(BSS->getSectionName(), BSS->getType(), BSS->getFlags(), 4);
198 // getCtorSection - Get the static constructor section
199 ELFSection &ELFWriter::getCtorSection() {
200 const MCSectionELF *Ctor = (const MCSectionELF *)TLOF.getStaticCtorSection();
201 return getSection(Ctor->getSectionName(), Ctor->getType(), Ctor->getFlags());
204 // getDtorSection - Get the static destructor section
205 ELFSection &ELFWriter::getDtorSection() {
206 const MCSectionELF *Dtor = (const MCSectionELF *)TLOF.getStaticDtorSection();
207 return getSection(Dtor->getSectionName(), Dtor->getType(), Dtor->getFlags());
210 // getTextSection - Get the text section for the specified function
211 ELFSection &ELFWriter::getTextSection(const Function *F) {
212 const MCSectionELF *Text =
213 (const MCSectionELF *)TLOF.SectionForGlobal(F, Mang, TM);
214 return getSection(Text->getSectionName(), Text->getType(), Text->getFlags());
217 // getJumpTableSection - Get a read only section for constants when
218 // emitting jump tables. TODO: add PIC support
219 ELFSection &ELFWriter::getJumpTableSection() {
220 const MCSectionELF *JT =
221 (const MCSectionELF *)TLOF.getSectionForConstant(SectionKind::getReadOnly());
222 return getSection(JT->getSectionName(), JT->getType(), JT->getFlags(),
223 TM.getTargetData()->getPointerABIAlignment());
226 // getConstantPoolSection - Get a constant pool section based on the machine
227 // constant pool entry type and relocation info.
228 ELFSection &ELFWriter::getConstantPoolSection(MachineConstantPoolEntry &CPE) {
230 switch (CPE.getRelocationInfo()) {
231 default: llvm_unreachable("Unknown section kind");
232 case 2: Kind = SectionKind::getReadOnlyWithRel(); break;
234 Kind = SectionKind::getReadOnlyWithRelLocal();
237 switch (TM.getTargetData()->getTypeAllocSize(CPE.getType())) {
238 case 4: Kind = SectionKind::getMergeableConst4(); break;
239 case 8: Kind = SectionKind::getMergeableConst8(); break;
240 case 16: Kind = SectionKind::getMergeableConst16(); break;
241 default: Kind = SectionKind::getMergeableConst(); break;
245 const MCSectionELF *CPSect =
246 (const MCSectionELF *)TLOF.getSectionForConstant(Kind);
247 return getSection(CPSect->getSectionName(), CPSect->getType(),
248 CPSect->getFlags(), CPE.getAlignment());
251 // getRelocSection - Return the relocation section of section 'S'. 'RelA'
252 // is true if the relocation section contains entries with addends.
253 ELFSection &ELFWriter::getRelocSection(ELFSection &S) {
254 unsigned SectionType = TEW->hasRelocationAddend() ?
255 ELFSection::SHT_RELA : ELFSection::SHT_REL;
257 std::string SectionName(".rel");
258 if (TEW->hasRelocationAddend())
259 SectionName.append("a");
260 SectionName.append(S.getName());
262 return getSection(SectionName, SectionType, 0, TEW->getPrefELFAlignment());
265 // getGlobalELFVisibility - Returns the ELF specific visibility type
266 unsigned ELFWriter::getGlobalELFVisibility(const GlobalValue *GV) {
267 switch (GV->getVisibility()) {
269 llvm_unreachable("unknown visibility type");
270 case GlobalValue::DefaultVisibility:
271 return ELFSym::STV_DEFAULT;
272 case GlobalValue::HiddenVisibility:
273 return ELFSym::STV_HIDDEN;
274 case GlobalValue::ProtectedVisibility:
275 return ELFSym::STV_PROTECTED;
280 // getGlobalELFBinding - Returns the ELF specific binding type
281 unsigned ELFWriter::getGlobalELFBinding(const GlobalValue *GV) {
282 if (GV->hasInternalLinkage())
283 return ELFSym::STB_LOCAL;
285 if (GV->isWeakForLinker() && !GV->hasCommonLinkage())
286 return ELFSym::STB_WEAK;
288 return ELFSym::STB_GLOBAL;
291 // getGlobalELFType - Returns the ELF specific type for a global
292 unsigned ELFWriter::getGlobalELFType(const GlobalValue *GV) {
293 if (GV->isDeclaration())
294 return ELFSym::STT_NOTYPE;
296 if (isa<Function>(GV))
297 return ELFSym::STT_FUNC;
299 return ELFSym::STT_OBJECT;
302 // IsELFUndefSym - True if the global value must be marked as a symbol
303 // which points to a SHN_UNDEF section. This means that the symbol has
304 // no definition on the module.
305 static bool IsELFUndefSym(const GlobalValue *GV) {
306 return GV->isDeclaration() || (isa<Function>(GV));
309 // AddToSymbolList - Update the symbol lookup and If the symbol is
310 // private add it to PrivateSyms list, otherwise to SymbolList.
311 void ELFWriter::AddToSymbolList(ELFSym *GblSym) {
312 assert(GblSym->isGlobalValue() && "Symbol must be a global value");
314 const GlobalValue *GV = GblSym->getGlobalValue();
315 if (GV->hasPrivateLinkage()) {
316 // For a private symbols, keep track of the index inside
317 // the private list since it will never go to the symbol
318 // table and won't be patched up later.
319 PrivateSyms.push_back(GblSym);
320 GblSymLookup[GV] = PrivateSyms.size()-1;
322 // Non private symbol are left with zero indices until
323 // they are patched up during the symbol table emition
324 // (where the indicies are created).
325 SymbolList.push_back(GblSym);
326 GblSymLookup[GV] = 0;
330 // EmitGlobal - Choose the right section for global and emit it
331 void ELFWriter::EmitGlobal(const GlobalValue *GV) {
333 // Check if the referenced symbol is already emitted
334 if (GblSymLookup.find(GV) != GblSymLookup.end())
337 // Handle ELF Bind, Visibility and Type for the current symbol
338 unsigned SymBind = getGlobalELFBinding(GV);
339 unsigned SymType = getGlobalELFType(GV);
340 bool IsUndefSym = IsELFUndefSym(GV);
342 ELFSym *GblSym = IsUndefSym ? ELFSym::getUndefGV(GV, SymBind)
343 : ELFSym::getGV(GV, SymBind, SymType, getGlobalELFVisibility(GV));
346 assert(isa<GlobalVariable>(GV) && "GV not a global variable!");
347 const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV);
349 // Handle special llvm globals
350 if (EmitSpecialLLVMGlobal(GVar))
353 // Get the ELF section where this global belongs from TLOF
354 const MCSectionELF *S =
355 (const MCSectionELF *)TLOF.SectionForGlobal(GV, Mang, TM);
357 getSection(S->getSectionName(), S->getType(), S->getFlags());
358 SectionKind Kind = S->getKind();
360 // The symbol align should update the section alignment if needed
361 const TargetData *TD = TM.getTargetData();
362 unsigned Align = TD->getPreferredAlignment(GVar);
363 unsigned Size = TD->getTypeAllocSize(GVar->getInitializer()->getType());
366 if (S->HasCommonSymbols()) { // Symbol must go to a common section
367 GblSym->SectionIdx = ELFSection::SHN_COMMON;
369 // A new linkonce section is created for each global in the
370 // common section, the default alignment is 1 and the symbol
371 // value contains its alignment.
373 GblSym->Value = Align;
375 } else if (Kind.isBSS() || Kind.isThreadBSS()) { // Symbol goes to BSS.
376 GblSym->SectionIdx = ES.SectionIdx;
378 // Update the size with alignment and the next object can
379 // start in the right offset in the section
380 if (Align) ES.Size = (ES.Size + Align-1) & ~(Align-1);
381 ES.Align = std::max(ES.Align, Align);
383 // GblSym->Value should contain the virtual offset inside the section.
384 // Virtual because the BSS space is not allocated on ELF objects
385 GblSym->Value = ES.Size;
388 } else { // The symbol must go to some kind of data section
389 GblSym->SectionIdx = ES.SectionIdx;
391 // GblSym->Value should contain the symbol offset inside the section,
392 // and all symbols should start on their required alignment boundary
393 ES.Align = std::max(ES.Align, Align);
394 ES.emitAlignment(Align);
395 GblSym->Value = ES.size();
397 // Emit the global to the data section 'ES'
398 EmitGlobalConstant(GVar->getInitializer(), ES);
402 AddToSymbolList(GblSym);
405 void ELFWriter::EmitGlobalConstantStruct(const ConstantStruct *CVS,
408 // Print the fields in successive locations. Pad to align if needed!
409 const TargetData *TD = TM.getTargetData();
410 unsigned Size = TD->getTypeAllocSize(CVS->getType());
411 const StructLayout *cvsLayout = TD->getStructLayout(CVS->getType());
412 uint64_t sizeSoFar = 0;
413 for (unsigned i = 0, e = CVS->getNumOperands(); i != e; ++i) {
414 const Constant* field = CVS->getOperand(i);
416 // Check if padding is needed and insert one or more 0s.
417 uint64_t fieldSize = TD->getTypeAllocSize(field->getType());
418 uint64_t padSize = ((i == e-1 ? Size : cvsLayout->getElementOffset(i+1))
419 - cvsLayout->getElementOffset(i)) - fieldSize;
420 sizeSoFar += fieldSize + padSize;
422 // Now print the actual field value.
423 EmitGlobalConstant(field, GblS);
425 // Insert padding - this may include padding to increase the size of the
426 // current field up to the ABI size (if the struct is not packed) as well
427 // as padding to ensure that the next field starts at the right offset.
428 GblS.emitZeros(padSize);
430 assert(sizeSoFar == cvsLayout->getSizeInBytes() &&
431 "Layout of constant struct may be incorrect!");
434 void ELFWriter::EmitGlobalConstant(const Constant *CV, ELFSection &GblS) {
435 const TargetData *TD = TM.getTargetData();
436 unsigned Size = TD->getTypeAllocSize(CV->getType());
438 if (const ConstantArray *CVA = dyn_cast<ConstantArray>(CV)) {
439 for (unsigned i = 0, e = CVA->getNumOperands(); i != e; ++i)
440 EmitGlobalConstant(CVA->getOperand(i), GblS);
442 } else if (isa<ConstantAggregateZero>(CV)) {
443 GblS.emitZeros(Size);
445 } else if (const ConstantStruct *CVS = dyn_cast<ConstantStruct>(CV)) {
446 EmitGlobalConstantStruct(CVS, GblS);
448 } else if (const ConstantFP *CFP = dyn_cast<ConstantFP>(CV)) {
449 APInt Val = CFP->getValueAPF().bitcastToAPInt();
450 if (CFP->getType()->isDoubleTy())
451 GblS.emitWord64(Val.getZExtValue());
452 else if (CFP->getType()->isFloatTy())
453 GblS.emitWord32(Val.getZExtValue());
454 else if (CFP->getType()->isX86_FP80Ty()) {
455 unsigned PadSize = TD->getTypeAllocSize(CFP->getType())-
456 TD->getTypeStoreSize(CFP->getType());
457 GblS.emitWordFP80(Val.getRawData(), PadSize);
458 } else if (CFP->getType()->isPPC_FP128Ty())
459 llvm_unreachable("PPC_FP128Ty global emission not implemented");
461 } else if (const ConstantInt *CI = dyn_cast<ConstantInt>(CV)) {
463 GblS.emitByte(CI->getZExtValue());
465 GblS.emitWord16(CI->getZExtValue());
467 GblS.emitWord32(CI->getZExtValue());
469 EmitGlobalConstantLargeInt(CI, GblS);
471 } else if (const ConstantVector *CP = dyn_cast<ConstantVector>(CV)) {
472 const VectorType *PTy = CP->getType();
473 for (unsigned I = 0, E = PTy->getNumElements(); I < E; ++I)
474 EmitGlobalConstant(CP->getOperand(I), GblS);
476 } else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(CV)) {
477 // Resolve a constant expression which returns a (Constant, Offset)
478 // pair. If 'Res.first' is a GlobalValue, emit a relocation with
479 // the offset 'Res.second', otherwise emit a global constant like
480 // it is always done for not contant expression types.
481 CstExprResTy Res = ResolveConstantExpr(CE);
482 const Constant *Op = Res.first;
484 if (isa<GlobalValue>(Op))
485 EmitGlobalDataRelocation(cast<const GlobalValue>(Op),
486 TD->getTypeAllocSize(Op->getType()),
489 EmitGlobalConstant(Op, GblS);
492 } else if (CV->getType()->getTypeID() == Type::PointerTyID) {
493 // Fill the data entry with zeros or emit a relocation entry
494 if (isa<ConstantPointerNull>(CV))
495 GblS.emitZeros(Size);
497 EmitGlobalDataRelocation(cast<const GlobalValue>(CV),
500 } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(CV)) {
501 // This is a constant address for a global variable or function and
502 // therefore must be referenced using a relocation entry.
503 EmitGlobalDataRelocation(GV, Size, GblS);
508 raw_string_ostream ErrorMsg(msg);
509 ErrorMsg << "Constant unimp for type: " << *CV->getType();
510 report_fatal_error(ErrorMsg.str());
513 // ResolveConstantExpr - Resolve the constant expression until it stop
514 // yielding other constant expressions.
515 CstExprResTy ELFWriter::ResolveConstantExpr(const Constant *CV) {
516 const TargetData *TD = TM.getTargetData();
518 // There ins't constant expression inside others anymore
519 if (!isa<ConstantExpr>(CV))
520 return std::make_pair(CV, 0);
522 const ConstantExpr *CE = dyn_cast<ConstantExpr>(CV);
523 switch (CE->getOpcode()) {
524 case Instruction::BitCast:
525 return ResolveConstantExpr(CE->getOperand(0));
527 case Instruction::GetElementPtr: {
528 const Constant *ptrVal = CE->getOperand(0);
529 SmallVector<Value*, 8> idxVec(CE->op_begin()+1, CE->op_end());
530 int64_t Offset = TD->getIndexedOffset(ptrVal->getType(), &idxVec[0],
532 return std::make_pair(ptrVal, Offset);
534 case Instruction::IntToPtr: {
535 Constant *Op = CE->getOperand(0);
536 Op = ConstantExpr::getIntegerCast(Op, TD->getIntPtrType(CV->getContext()),
538 return ResolveConstantExpr(Op);
540 case Instruction::PtrToInt: {
541 Constant *Op = CE->getOperand(0);
542 const Type *Ty = CE->getType();
544 // We can emit the pointer value into this slot if the slot is an
545 // integer slot greater or equal to the size of the pointer.
546 if (TD->getTypeAllocSize(Ty) == TD->getTypeAllocSize(Op->getType()))
547 return ResolveConstantExpr(Op);
549 llvm_unreachable("Integer size less then pointer size");
551 case Instruction::Add:
552 case Instruction::Sub: {
553 // Only handle cases where there's a constant expression with GlobalValue
554 // as first operand and ConstantInt as second, which are the cases we can
555 // solve direclty using a relocation entry. GlobalValue=Op0, CstInt=Op1
556 // 1) Instruction::Add => (global) + CstInt
557 // 2) Instruction::Sub => (global) + -CstInt
558 const Constant *Op0 = CE->getOperand(0);
559 const Constant *Op1 = CE->getOperand(1);
560 assert(isa<ConstantInt>(Op1) && "Op1 must be a ConstantInt");
562 CstExprResTy Res = ResolveConstantExpr(Op0);
563 assert(isa<GlobalValue>(Res.first) && "Op0 must be a GlobalValue");
565 const APInt &RHS = cast<ConstantInt>(Op1)->getValue();
566 switch (CE->getOpcode()) {
567 case Instruction::Add:
568 return std::make_pair(Res.first, RHS.getSExtValue());
569 case Instruction::Sub:
570 return std::make_pair(Res.first, (-RHS).getSExtValue());
575 report_fatal_error(CE->getOpcodeName() +
576 StringRef(": Unsupported ConstantExpr type"));
578 return std::make_pair(CV, 0); // silence warning
581 void ELFWriter::EmitGlobalDataRelocation(const GlobalValue *GV, unsigned Size,
582 ELFSection &GblS, int64_t Offset) {
583 // Create the relocation entry for the global value
584 MachineRelocation MR =
585 MachineRelocation::getGV(GblS.getCurrentPCOffset(),
586 TEW->getAbsoluteLabelMachineRelTy(),
587 const_cast<GlobalValue*>(GV),
590 // Fill the data entry with zeros
591 GblS.emitZeros(Size);
593 // Add the relocation entry for the current data section
594 GblS.addRelocation(MR);
597 void ELFWriter::EmitGlobalConstantLargeInt(const ConstantInt *CI,
599 const TargetData *TD = TM.getTargetData();
600 unsigned BitWidth = CI->getBitWidth();
601 assert(isPowerOf2_32(BitWidth) &&
602 "Non-power-of-2-sized integers not handled!");
604 const uint64_t *RawData = CI->getValue().getRawData();
606 for (unsigned i = 0, e = BitWidth / 64; i != e; ++i) {
607 Val = (TD->isBigEndian()) ? RawData[e - i - 1] : RawData[i];
612 /// EmitSpecialLLVMGlobal - Check to see if the specified global is a
613 /// special global used by LLVM. If so, emit it and return true, otherwise
614 /// do nothing and return false.
615 bool ELFWriter::EmitSpecialLLVMGlobal(const GlobalVariable *GV) {
616 if (GV->getName() == "llvm.used")
617 llvm_unreachable("not implemented yet");
619 // Ignore debug and non-emitted data. This handles llvm.compiler.used.
620 if (GV->getSection() == "llvm.metadata" ||
621 GV->hasAvailableExternallyLinkage())
624 if (!GV->hasAppendingLinkage()) return false;
626 assert(GV->hasInitializer() && "Not a special LLVM global!");
628 const TargetData *TD = TM.getTargetData();
629 unsigned Align = TD->getPointerPrefAlignment();
630 if (GV->getName() == "llvm.global_ctors") {
631 ELFSection &Ctor = getCtorSection();
632 Ctor.emitAlignment(Align);
633 EmitXXStructorList(GV->getInitializer(), Ctor);
637 if (GV->getName() == "llvm.global_dtors") {
638 ELFSection &Dtor = getDtorSection();
639 Dtor.emitAlignment(Align);
640 EmitXXStructorList(GV->getInitializer(), Dtor);
647 /// EmitXXStructorList - Emit the ctor or dtor list. This just emits out the
648 /// function pointers, ignoring the init priority.
649 void ELFWriter::EmitXXStructorList(Constant *List, ELFSection &Xtor) {
650 // Should be an array of '{ int, void ()* }' structs. The first value is the
651 // init priority, which we ignore.
652 if (!isa<ConstantArray>(List)) return;
653 ConstantArray *InitList = cast<ConstantArray>(List);
654 for (unsigned i = 0, e = InitList->getNumOperands(); i != e; ++i)
655 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(InitList->getOperand(i))){
656 if (CS->getNumOperands() != 2) return; // Not array of 2-element structs.
658 if (CS->getOperand(1)->isNullValue())
659 return; // Found a null terminator, exit printing.
660 // Emit the function pointer.
661 EmitGlobalConstant(CS->getOperand(1), Xtor);
665 bool ELFWriter::runOnMachineFunction(MachineFunction &MF) {
666 // Nothing to do here, this is all done through the ElfCE object above.
670 /// doFinalization - Now that the module has been completely processed, emit
671 /// the ELF file to 'O'.
672 bool ELFWriter::doFinalization(Module &M) {
673 // Emit .data section placeholder
676 // Emit .bss section placeholder
679 // Build and emit data, bss and "common" sections.
680 for (Module::global_iterator I = M.global_begin(), E = M.global_end();
684 // Emit all pending globals
685 for (PendingGblsIter I = PendingGlobals.begin(), E = PendingGlobals.end();
689 // Emit all pending externals
690 for (PendingExtsIter I = PendingExternals.begin(), E = PendingExternals.end();
692 SymbolList.push_back(ELFSym::getExtSym(*I));
694 // Emit a symbol for each section created until now, skip null section
695 for (unsigned i = 1, e = SectionList.size(); i < e; ++i) {
696 ELFSection &ES = *SectionList[i];
697 ELFSym *SectionSym = ELFSym::getSectionSym();
698 SectionSym->SectionIdx = ES.SectionIdx;
699 SymbolList.push_back(SectionSym);
700 ES.Sym = SymbolList.back();
704 EmitStringTable(M.getModuleIdentifier());
706 // Emit the symbol table now, if non-empty.
709 // Emit the relocation sections.
712 // Emit the sections string table.
713 EmitSectionTableStringTable();
715 // Dump the sections and section table to the .o file.
716 OutputSectionsAndSectionTable();
721 // RelocateField - Patch relocatable field with 'Offset' in 'BO'
722 // using a 'Value' of known 'Size'
723 void ELFWriter::RelocateField(BinaryObject &BO, uint32_t Offset,
724 int64_t Value, unsigned Size) {
726 BO.fixWord32(Value, Offset);
728 BO.fixWord64(Value, Offset);
730 llvm_unreachable("don't know howto patch relocatable field");
733 /// EmitRelocations - Emit relocations
734 void ELFWriter::EmitRelocations() {
736 // True if the target uses the relocation entry to hold the addend,
737 // otherwise the addend is written directly to the relocatable field.
738 bool HasRelA = TEW->hasRelocationAddend();
740 // Create Relocation sections for each section which needs it.
741 for (unsigned i=0, e=SectionList.size(); i != e; ++i) {
742 ELFSection &S = *SectionList[i];
744 // This section does not have relocations
745 if (!S.hasRelocations()) continue;
746 ELFSection &RelSec = getRelocSection(S);
748 // 'Link' - Section hdr idx of the associated symbol table
749 // 'Info' - Section hdr idx of the section to which the relocation applies
750 ELFSection &SymTab = getSymbolTableSection();
751 RelSec.Link = SymTab.SectionIdx;
752 RelSec.Info = S.SectionIdx;
753 RelSec.EntSize = TEW->getRelocationEntrySize();
755 // Get the relocations from Section
756 std::vector<MachineRelocation> Relos = S.getRelocations();
757 for (std::vector<MachineRelocation>::iterator MRI = Relos.begin(),
758 MRE = Relos.end(); MRI != MRE; ++MRI) {
759 MachineRelocation &MR = *MRI;
761 // Relocatable field offset from the section start
762 unsigned RelOffset = MR.getMachineCodeOffset();
764 // Symbol index in the symbol table
767 // Target specific relocation field type and size
768 unsigned RelType = TEW->getRelocationType(MR.getRelocationType());
769 unsigned RelTySize = TEW->getRelocationTySize(RelType);
772 // There are several machine relocations types, and each one of
773 // them needs a different approach to retrieve the symbol table index.
774 if (MR.isGlobalValue()) {
775 const GlobalValue *G = MR.getGlobalValue();
776 int64_t GlobalOffset = MR.getConstantVal();
777 SymIdx = GblSymLookup[G];
778 if (G->hasPrivateLinkage()) {
779 // If the target uses a section offset in the relocation:
780 // SymIdx + Addend = section sym for global + section offset
781 unsigned SectionIdx = PrivateSyms[SymIdx]->SectionIdx;
782 Addend = PrivateSyms[SymIdx]->Value + GlobalOffset;
783 SymIdx = SectionList[SectionIdx]->getSymbolTableIndex();
785 Addend = TEW->getDefaultAddendForRelTy(RelType, GlobalOffset);
787 } else if (MR.isExternalSymbol()) {
788 const char *ExtSym = MR.getExternalSymbol();
789 SymIdx = ExtSymLookup[ExtSym];
790 Addend = TEW->getDefaultAddendForRelTy(RelType);
792 // Get the symbol index for the section symbol
793 unsigned SectionIdx = MR.getConstantVal();
794 SymIdx = SectionList[SectionIdx]->getSymbolTableIndex();
796 // The symbol offset inside the section
797 int64_t SymOffset = (int64_t)MR.getResultPointer();
799 // For pc relative relocations where symbols are defined in the same
800 // section they are referenced, ignore the relocation entry and patch
801 // the relocatable field with the symbol offset directly.
802 if (S.SectionIdx == SectionIdx && TEW->isPCRelativeRel(RelType)) {
803 int64_t Value = TEW->computeRelocation(SymOffset, RelOffset, RelType);
804 RelocateField(S, RelOffset, Value, RelTySize);
808 Addend = TEW->getDefaultAddendForRelTy(RelType, SymOffset);
811 // The target without addend on the relocation symbol must be
812 // patched in the relocation place itself to contain the addend
813 // otherwise write zeros to make sure there is no garbage there
814 RelocateField(S, RelOffset, HasRelA ? 0 : Addend, RelTySize);
816 // Get the relocation entry and emit to the relocation section
817 ELFRelocation Rel(RelOffset, SymIdx, RelType, HasRelA, Addend);
818 EmitRelocation(RelSec, Rel, HasRelA);
823 /// EmitRelocation - Write relocation 'Rel' to the relocation section 'Rel'
824 void ELFWriter::EmitRelocation(BinaryObject &RelSec, ELFRelocation &Rel,
826 RelSec.emitWord(Rel.getOffset());
827 RelSec.emitWord(Rel.getInfo(is64Bit));
829 RelSec.emitWord(Rel.getAddend());
832 /// EmitSymbol - Write symbol 'Sym' to the symbol table 'SymbolTable'
833 void ELFWriter::EmitSymbol(BinaryObject &SymbolTable, ELFSym &Sym) {
835 SymbolTable.emitWord32(Sym.NameIdx);
836 SymbolTable.emitByte(Sym.Info);
837 SymbolTable.emitByte(Sym.Other);
838 SymbolTable.emitWord16(Sym.SectionIdx);
839 SymbolTable.emitWord64(Sym.Value);
840 SymbolTable.emitWord64(Sym.Size);
842 SymbolTable.emitWord32(Sym.NameIdx);
843 SymbolTable.emitWord32(Sym.Value);
844 SymbolTable.emitWord32(Sym.Size);
845 SymbolTable.emitByte(Sym.Info);
846 SymbolTable.emitByte(Sym.Other);
847 SymbolTable.emitWord16(Sym.SectionIdx);
851 /// EmitSectionHeader - Write section 'Section' header in 'SHdrTab'
852 /// Section Header Table
853 void ELFWriter::EmitSectionHeader(BinaryObject &SHdrTab,
854 const ELFSection &SHdr) {
855 SHdrTab.emitWord32(SHdr.NameIdx);
856 SHdrTab.emitWord32(SHdr.Type);
858 SHdrTab.emitWord64(SHdr.Flags);
859 SHdrTab.emitWord(SHdr.Addr);
860 SHdrTab.emitWord(SHdr.Offset);
861 SHdrTab.emitWord64(SHdr.Size);
862 SHdrTab.emitWord32(SHdr.Link);
863 SHdrTab.emitWord32(SHdr.Info);
864 SHdrTab.emitWord64(SHdr.Align);
865 SHdrTab.emitWord64(SHdr.EntSize);
867 SHdrTab.emitWord32(SHdr.Flags);
868 SHdrTab.emitWord(SHdr.Addr);
869 SHdrTab.emitWord(SHdr.Offset);
870 SHdrTab.emitWord32(SHdr.Size);
871 SHdrTab.emitWord32(SHdr.Link);
872 SHdrTab.emitWord32(SHdr.Info);
873 SHdrTab.emitWord32(SHdr.Align);
874 SHdrTab.emitWord32(SHdr.EntSize);
878 /// EmitStringTable - If the current symbol table is non-empty, emit the string
880 void ELFWriter::EmitStringTable(const std::string &ModuleName) {
881 if (!SymbolList.size()) return; // Empty symbol table.
882 ELFSection &StrTab = getStringTableSection();
884 // Set the zero'th symbol to a null byte, as required.
887 // Walk on the symbol list and write symbol names into the string table.
889 for (ELFSymIter I=SymbolList.begin(), E=SymbolList.end(); I != E; ++I) {
893 if (Sym.isGlobalValue()) {
894 SmallString<40> NameStr;
895 Mang->getNameWithPrefix(NameStr, Sym.getGlobalValue(), false);
896 Name.append(NameStr.begin(), NameStr.end());
897 } else if (Sym.isExternalSym())
898 Name.append(Sym.getExternalSymbol());
899 else if (Sym.isFileType())
900 Name.append(ModuleName);
906 StrTab.emitString(Name);
908 // Keep track of the number of bytes emitted to this section.
909 Index += Name.size()+1;
912 assert(Index == StrTab.size());
916 // SortSymbols - On the symbol table local symbols must come before
917 // all other symbols with non-local bindings. The return value is
918 // the position of the first non local symbol.
919 unsigned ELFWriter::SortSymbols() {
920 unsigned FirstNonLocalSymbol;
921 std::vector<ELFSym*> LocalSyms, OtherSyms;
923 for (ELFSymIter I=SymbolList.begin(), E=SymbolList.end(); I != E; ++I) {
924 if ((*I)->isLocalBind())
925 LocalSyms.push_back(*I);
927 OtherSyms.push_back(*I);
930 FirstNonLocalSymbol = LocalSyms.size();
932 for (unsigned i = 0; i < FirstNonLocalSymbol; ++i)
933 SymbolList.push_back(LocalSyms[i]);
935 for (ELFSymIter I=OtherSyms.begin(), E=OtherSyms.end(); I != E; ++I)
936 SymbolList.push_back(*I);
941 return FirstNonLocalSymbol;
944 /// EmitSymbolTable - Emit the symbol table itself.
945 void ELFWriter::EmitSymbolTable() {
946 if (!SymbolList.size()) return; // Empty symbol table.
948 // Now that we have emitted the string table and know the offset into the
949 // string table of each symbol, emit the symbol table itself.
950 ELFSection &SymTab = getSymbolTableSection();
951 SymTab.Align = TEW->getPrefELFAlignment();
953 // Section Index of .strtab.
954 SymTab.Link = getStringTableSection().SectionIdx;
956 // Size of each symtab entry.
957 SymTab.EntSize = TEW->getSymTabEntrySize();
959 // Reorder the symbol table with local symbols first!
960 unsigned FirstNonLocalSymbol = SortSymbols();
962 // Emit all the symbols to the symbol table.
963 for (unsigned i = 0, e = SymbolList.size(); i < e; ++i) {
964 ELFSym &Sym = *SymbolList[i];
966 // Emit symbol to the symbol table
967 EmitSymbol(SymTab, Sym);
969 // Record the symbol table index for each symbol
970 if (Sym.isGlobalValue())
971 GblSymLookup[Sym.getGlobalValue()] = i;
972 else if (Sym.isExternalSym())
973 ExtSymLookup[Sym.getExternalSymbol()] = i;
975 // Keep track on the symbol index into the symbol table
979 // One greater than the symbol table index of the last local symbol
980 SymTab.Info = FirstNonLocalSymbol;
981 SymTab.Size = SymTab.size();
984 /// EmitSectionTableStringTable - This method adds and emits a section for the
985 /// ELF Section Table string table: the string table that holds all of the
987 void ELFWriter::EmitSectionTableStringTable() {
988 // First step: add the section for the string table to the list of sections:
989 ELFSection &SHStrTab = getSectionHeaderStringTableSection();
991 // Now that we know which section number is the .shstrtab section, update the
992 // e_shstrndx entry in the ELF header.
993 ElfHdr.fixWord16(SHStrTab.SectionIdx, ELFHdr_e_shstrndx_Offset);
995 // Set the NameIdx of each section in the string table and emit the bytes for
999 for (ELFSectionIter I=SectionList.begin(), E=SectionList.end(); I != E; ++I) {
1000 ELFSection &S = *(*I);
1001 // Set the index into the table. Note if we have lots of entries with
1002 // common suffixes, we could memoize them here if we cared.
1004 SHStrTab.emitString(S.getName());
1006 // Keep track of the number of bytes emitted to this section.
1007 Index += S.getName().size()+1;
1010 // Set the size of .shstrtab now that we know what it is.
1011 assert(Index == SHStrTab.size());
1012 SHStrTab.Size = Index;
1015 /// OutputSectionsAndSectionTable - Now that we have constructed the file header
1016 /// and all of the sections, emit these to the ostream destination and emit the
1018 void ELFWriter::OutputSectionsAndSectionTable() {
1019 // Pass #1: Compute the file offset for each section.
1020 size_t FileOff = ElfHdr.size(); // File header first.
1022 // Adjust alignment of all section if needed, skip the null section.
1023 for (unsigned i=1, e=SectionList.size(); i < e; ++i) {
1024 ELFSection &ES = *SectionList[i];
1026 ES.Offset = FileOff;
1030 // Update Section size
1032 ES.Size = ES.size();
1034 // Align FileOff to whatever the alignment restrictions of the section are.
1036 FileOff = (FileOff+ES.Align-1) & ~(ES.Align-1);
1038 ES.Offset = FileOff;
1042 // Align Section Header.
1043 unsigned TableAlign = TEW->getPrefELFAlignment();
1044 FileOff = (FileOff+TableAlign-1) & ~(TableAlign-1);
1046 // Now that we know where all of the sections will be emitted, set the e_shnum
1047 // entry in the ELF header.
1048 ElfHdr.fixWord16(NumSections, ELFHdr_e_shnum_Offset);
1050 // Now that we know the offset in the file of the section table, update the
1051 // e_shoff address in the ELF header.
1052 ElfHdr.fixWord(FileOff, ELFHdr_e_shoff_Offset);
1054 // Now that we know all of the data in the file header, emit it and all of the
1056 O.write((char *)&ElfHdr.getData()[0], ElfHdr.size());
1057 FileOff = ElfHdr.size();
1059 // Section Header Table blob
1060 BinaryObject SHdrTable(isLittleEndian, is64Bit);
1062 // Emit all of sections to the file and build the section header table.
1063 for (ELFSectionIter I=SectionList.begin(), E=SectionList.end(); I != E; ++I) {
1064 ELFSection &S = *(*I);
1065 DEBUG(dbgs() << "SectionIdx: " << S.SectionIdx << ", Name: " << S.getName()
1066 << ", Size: " << S.Size << ", Offset: " << S.Offset
1067 << ", SectionData Size: " << S.size() << "\n");
1069 // Align FileOff to whatever the alignment restrictions of the section are.
1072 for (size_t NewFileOff = (FileOff+S.Align-1) & ~(S.Align-1);
1073 FileOff != NewFileOff; ++FileOff)
1076 O.write((char *)&S.getData()[0], S.Size);
1080 EmitSectionHeader(SHdrTable, S);
1083 // Align output for the section table.
1084 for (size_t NewFileOff = (FileOff+TableAlign-1) & ~(TableAlign-1);
1085 FileOff != NewFileOff; ++FileOff)
1088 // Emit the section table itself.
1089 O.write((char *)&SHdrTable.getData()[0], SHdrTable.size());