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/TargetAsmInfo.h"
49 #include "llvm/Target/TargetData.h"
50 #include "llvm/Target/TargetELFWriterInfo.h"
51 #include "llvm/Target/TargetLowering.h"
52 #include "llvm/Target/TargetLoweringObjectFile.h"
53 #include "llvm/Target/TargetMachine.h"
54 #include "llvm/Target/TargetRegisterInfo.h"
55 #include "llvm/Support/Debug.h"
56 #include "llvm/Support/ErrorHandling.h"
57 #include "llvm/Support/raw_ostream.h"
58 #include "llvm/ADT/SmallString.h"
61 char ELFWriter::ID = 0;
63 //===----------------------------------------------------------------------===//
64 // ELFWriter Implementation
65 //===----------------------------------------------------------------------===//
67 ELFWriter::ELFWriter(raw_ostream &o, TargetMachine &tm)
68 : MachineFunctionPass(ID), O(o), TM(tm),
69 OutContext(*new MCContext(*TM.getMCAsmInfo(), *TM.getRegisterInfo(),
70 new TargetAsmInfo(tm))),
71 TLOF(TM.getTargetLowering()->getObjFileLowering()),
72 is64Bit(TM.getTargetData()->getPointerSizeInBits() == 64),
73 isLittleEndian(TM.getTargetData()->isLittleEndian()),
74 ElfHdr(isLittleEndian, is64Bit) {
76 MAI = TM.getMCAsmInfo();
77 TEW = TM.getELFWriterInfo();
79 // Create the object code emitter object for this target.
80 ElfCE = new ELFCodeEmitter(*this);
82 // Initial number of sections
86 ELFWriter::~ELFWriter() {
90 while(!SymbolList.empty()) {
91 delete SymbolList.back();
92 SymbolList.pop_back();
95 while(!PrivateSyms.empty()) {
96 delete PrivateSyms.back();
97 PrivateSyms.pop_back();
100 while(!SectionList.empty()) {
101 delete SectionList.back();
102 SectionList.pop_back();
105 // Release the name mangler object.
106 delete Mang; Mang = 0;
109 // doInitialization - Emit the file header and all of the global variables for
110 // the module to the ELF file.
111 bool ELFWriter::doInitialization(Module &M) {
112 // Initialize TargetLoweringObjectFile.
113 const_cast<TargetLoweringObjectFile&>(TLOF).Initialize(OutContext, TM);
115 Mang = new Mangler(OutContext, *TM.getTargetData());
119 // Fields e_shnum e_shstrndx are only known after all section have
120 // been emitted. They locations in the ouput buffer are recorded so
121 // to be patched up later.
125 // emitWord method behaves differently for ELF32 and ELF64, writing
126 // 4 bytes in the former and 8 in the last for *_off and *_addr elf types
128 ElfHdr.emitByte(0x7f); // e_ident[EI_MAG0]
129 ElfHdr.emitByte('E'); // e_ident[EI_MAG1]
130 ElfHdr.emitByte('L'); // e_ident[EI_MAG2]
131 ElfHdr.emitByte('F'); // e_ident[EI_MAG3]
133 ElfHdr.emitByte(TEW->getEIClass()); // e_ident[EI_CLASS]
134 ElfHdr.emitByte(TEW->getEIData()); // e_ident[EI_DATA]
135 ElfHdr.emitByte(ELF::EV_CURRENT); // e_ident[EI_VERSION]
136 ElfHdr.emitAlignment(16); // e_ident[EI_NIDENT-EI_PAD]
138 ElfHdr.emitWord16(ELF::ET_REL); // e_type
139 ElfHdr.emitWord16(TEW->getEMachine()); // e_machine = target
140 ElfHdr.emitWord32(ELF::EV_CURRENT); // e_version
141 ElfHdr.emitWord(0); // e_entry, no entry point in .o file
142 ElfHdr.emitWord(0); // e_phoff, no program header for .o
143 ELFHdr_e_shoff_Offset = ElfHdr.size();
144 ElfHdr.emitWord(0); // e_shoff = sec hdr table off in bytes
145 ElfHdr.emitWord32(TEW->getEFlags()); // e_flags = whatever the target wants
146 ElfHdr.emitWord16(TEW->getHdrSize()); // e_ehsize = ELF header size
147 ElfHdr.emitWord16(0); // e_phentsize = prog header entry size
148 ElfHdr.emitWord16(0); // e_phnum = # prog header entries = 0
150 // e_shentsize = Section header entry size
151 ElfHdr.emitWord16(TEW->getSHdrSize());
153 // e_shnum = # of section header ents
154 ELFHdr_e_shnum_Offset = ElfHdr.size();
155 ElfHdr.emitWord16(0); // Placeholder
157 // e_shstrndx = Section # of '.shstrtab'
158 ELFHdr_e_shstrndx_Offset = ElfHdr.size();
159 ElfHdr.emitWord16(0); // Placeholder
161 // Add the null section, which is required to be first in the file.
164 // The first entry in the symtab is the null symbol and the second
165 // is a local symbol containing the module/file name
166 SymbolList.push_back(new ELFSym());
167 SymbolList.push_back(ELFSym::getFileSym());
172 // AddPendingGlobalSymbol - Add a global to be processed and to
173 // the global symbol lookup, use a zero index because the table
174 // index will be determined later.
175 void ELFWriter::AddPendingGlobalSymbol(const GlobalValue *GV,
176 bool AddToLookup /* = false */) {
177 PendingGlobals.insert(GV);
179 GblSymLookup[GV] = 0;
182 // AddPendingExternalSymbol - Add the external to be processed
183 // and to the external symbol lookup, use a zero index because
184 // the symbol table index will be determined later.
185 void ELFWriter::AddPendingExternalSymbol(const char *External) {
186 PendingExternals.insert(External);
187 ExtSymLookup[External] = 0;
190 ELFSection &ELFWriter::getDataSection() {
191 const MCSectionELF *Data = (const MCSectionELF *)TLOF.getDataSection();
192 return getSection(Data->getSectionName(), Data->getType(),
193 Data->getFlags(), 4);
196 ELFSection &ELFWriter::getBSSSection() {
197 const MCSectionELF *BSS = (const MCSectionELF *)TLOF.getBSSSection();
198 return getSection(BSS->getSectionName(), BSS->getType(), BSS->getFlags(), 4);
201 // getCtorSection - Get the static constructor section
202 ELFSection &ELFWriter::getCtorSection() {
203 const MCSectionELF *Ctor = (const MCSectionELF *)TLOF.getStaticCtorSection();
204 return getSection(Ctor->getSectionName(), Ctor->getType(), Ctor->getFlags());
207 // getDtorSection - Get the static destructor section
208 ELFSection &ELFWriter::getDtorSection() {
209 const MCSectionELF *Dtor = (const MCSectionELF *)TLOF.getStaticDtorSection();
210 return getSection(Dtor->getSectionName(), Dtor->getType(), Dtor->getFlags());
213 // getTextSection - Get the text section for the specified function
214 ELFSection &ELFWriter::getTextSection(const Function *F) {
215 const MCSectionELF *Text =
216 (const MCSectionELF *)TLOF.SectionForGlobal(F, Mang, TM);
217 return getSection(Text->getSectionName(), Text->getType(), Text->getFlags());
220 // getJumpTableSection - Get a read only section for constants when
221 // emitting jump tables. TODO: add PIC support
222 ELFSection &ELFWriter::getJumpTableSection() {
223 const MCSectionELF *JT =
224 (const MCSectionELF *)TLOF.getSectionForConstant(SectionKind::getReadOnly());
225 return getSection(JT->getSectionName(), JT->getType(), JT->getFlags(),
226 TM.getTargetData()->getPointerABIAlignment());
229 // getConstantPoolSection - Get a constant pool section based on the machine
230 // constant pool entry type and relocation info.
231 ELFSection &ELFWriter::getConstantPoolSection(MachineConstantPoolEntry &CPE) {
233 switch (CPE.getRelocationInfo()) {
234 default: llvm_unreachable("Unknown section kind");
235 case 2: Kind = SectionKind::getReadOnlyWithRel(); break;
237 Kind = SectionKind::getReadOnlyWithRelLocal();
240 switch (TM.getTargetData()->getTypeAllocSize(CPE.getType())) {
241 case 4: Kind = SectionKind::getMergeableConst4(); break;
242 case 8: Kind = SectionKind::getMergeableConst8(); break;
243 case 16: Kind = SectionKind::getMergeableConst16(); break;
244 default: Kind = SectionKind::getMergeableConst(); break;
248 const MCSectionELF *CPSect =
249 (const MCSectionELF *)TLOF.getSectionForConstant(Kind);
250 return getSection(CPSect->getSectionName(), CPSect->getType(),
251 CPSect->getFlags(), CPE.getAlignment());
254 // getRelocSection - Return the relocation section of section 'S'. 'RelA'
255 // is true if the relocation section contains entries with addends.
256 ELFSection &ELFWriter::getRelocSection(ELFSection &S) {
257 unsigned SectionType = TEW->hasRelocationAddend() ?
258 ELF::SHT_RELA : ELF::SHT_REL;
260 std::string SectionName(".rel");
261 if (TEW->hasRelocationAddend())
262 SectionName.append("a");
263 SectionName.append(S.getName());
265 return getSection(SectionName, SectionType, 0, TEW->getPrefELFAlignment());
268 // getGlobalELFVisibility - Returns the ELF specific visibility type
269 unsigned ELFWriter::getGlobalELFVisibility(const GlobalValue *GV) {
270 switch (GV->getVisibility()) {
272 llvm_unreachable("unknown visibility type");
273 case GlobalValue::DefaultVisibility:
274 return ELF::STV_DEFAULT;
275 case GlobalValue::HiddenVisibility:
276 return ELF::STV_HIDDEN;
277 case GlobalValue::ProtectedVisibility:
278 return ELF::STV_PROTECTED;
283 // getGlobalELFBinding - Returns the ELF specific binding type
284 unsigned ELFWriter::getGlobalELFBinding(const GlobalValue *GV) {
285 if (GV->hasInternalLinkage())
286 return ELF::STB_LOCAL;
288 if (GV->isWeakForLinker() && !GV->hasCommonLinkage())
289 return ELF::STB_WEAK;
291 return ELF::STB_GLOBAL;
294 // getGlobalELFType - Returns the ELF specific type for a global
295 unsigned ELFWriter::getGlobalELFType(const GlobalValue *GV) {
296 if (GV->isDeclaration())
297 return ELF::STT_NOTYPE;
299 if (isa<Function>(GV))
300 return ELF::STT_FUNC;
302 return ELF::STT_OBJECT;
305 // IsELFUndefSym - True if the global value must be marked as a symbol
306 // which points to a SHN_UNDEF section. This means that the symbol has
307 // no definition on the module.
308 static bool IsELFUndefSym(const GlobalValue *GV) {
309 return GV->isDeclaration() || (isa<Function>(GV));
312 // AddToSymbolList - Update the symbol lookup and If the symbol is
313 // private add it to PrivateSyms list, otherwise to SymbolList.
314 void ELFWriter::AddToSymbolList(ELFSym *GblSym) {
315 assert(GblSym->isGlobalValue() && "Symbol must be a global value");
317 const GlobalValue *GV = GblSym->getGlobalValue();
318 if (GV->hasPrivateLinkage()) {
319 // For a private symbols, keep track of the index inside
320 // the private list since it will never go to the symbol
321 // table and won't be patched up later.
322 PrivateSyms.push_back(GblSym);
323 GblSymLookup[GV] = PrivateSyms.size()-1;
325 // Non private symbol are left with zero indices until
326 // they are patched up during the symbol table emition
327 // (where the indicies are created).
328 SymbolList.push_back(GblSym);
329 GblSymLookup[GV] = 0;
333 /// HasCommonSymbols - True if this section holds common symbols, this is
334 /// indicated on the ELF object file by a symbol with SHN_COMMON section
336 static bool HasCommonSymbols(const MCSectionELF &S) {
337 // FIXME: this is wrong, a common symbol can be in .data for example.
338 if (StringRef(S.getSectionName()).startswith(".gnu.linkonce."))
345 // EmitGlobal - Choose the right section for global and emit it
346 void ELFWriter::EmitGlobal(const GlobalValue *GV) {
348 // Check if the referenced symbol is already emitted
349 if (GblSymLookup.find(GV) != GblSymLookup.end())
352 // Handle ELF Bind, Visibility and Type for the current symbol
353 unsigned SymBind = getGlobalELFBinding(GV);
354 unsigned SymType = getGlobalELFType(GV);
355 bool IsUndefSym = IsELFUndefSym(GV);
357 ELFSym *GblSym = IsUndefSym ? ELFSym::getUndefGV(GV, SymBind)
358 : ELFSym::getGV(GV, SymBind, SymType, getGlobalELFVisibility(GV));
361 assert(isa<GlobalVariable>(GV) && "GV not a global variable!");
362 const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV);
364 // Handle special llvm globals
365 if (EmitSpecialLLVMGlobal(GVar))
368 // Get the ELF section where this global belongs from TLOF
369 const MCSectionELF *S =
370 (const MCSectionELF *)TLOF.SectionForGlobal(GV, Mang, TM);
372 getSection(S->getSectionName(), S->getType(), S->getFlags());
373 SectionKind Kind = S->getKind();
375 // The symbol align should update the section alignment if needed
376 const TargetData *TD = TM.getTargetData();
377 unsigned Align = TD->getPreferredAlignment(GVar);
378 unsigned Size = TD->getTypeAllocSize(GVar->getInitializer()->getType());
381 if (HasCommonSymbols(*S)) { // Symbol must go to a common section
382 GblSym->SectionIdx = ELF::SHN_COMMON;
384 // A new linkonce section is created for each global in the
385 // common section, the default alignment is 1 and the symbol
386 // value contains its alignment.
388 GblSym->Value = Align;
390 } else if (Kind.isBSS() || Kind.isThreadBSS()) { // Symbol goes to BSS.
391 GblSym->SectionIdx = ES.SectionIdx;
393 // Update the size with alignment and the next object can
394 // start in the right offset in the section
395 if (Align) ES.Size = (ES.Size + Align-1) & ~(Align-1);
396 ES.Align = std::max(ES.Align, Align);
398 // GblSym->Value should contain the virtual offset inside the section.
399 // Virtual because the BSS space is not allocated on ELF objects
400 GblSym->Value = ES.Size;
403 } else { // The symbol must go to some kind of data section
404 GblSym->SectionIdx = ES.SectionIdx;
406 // GblSym->Value should contain the symbol offset inside the section,
407 // and all symbols should start on their required alignment boundary
408 ES.Align = std::max(ES.Align, Align);
409 ES.emitAlignment(Align);
410 GblSym->Value = ES.size();
412 // Emit the global to the data section 'ES'
413 EmitGlobalConstant(GVar->getInitializer(), ES);
417 AddToSymbolList(GblSym);
420 void ELFWriter::EmitGlobalConstantStruct(const ConstantStruct *CVS,
423 // Print the fields in successive locations. Pad to align if needed!
424 const TargetData *TD = TM.getTargetData();
425 unsigned Size = TD->getTypeAllocSize(CVS->getType());
426 const StructLayout *cvsLayout = TD->getStructLayout(CVS->getType());
427 uint64_t sizeSoFar = 0;
428 for (unsigned i = 0, e = CVS->getNumOperands(); i != e; ++i) {
429 const Constant* field = CVS->getOperand(i);
431 // Check if padding is needed and insert one or more 0s.
432 uint64_t fieldSize = TD->getTypeAllocSize(field->getType());
433 uint64_t padSize = ((i == e-1 ? Size : cvsLayout->getElementOffset(i+1))
434 - cvsLayout->getElementOffset(i)) - fieldSize;
435 sizeSoFar += fieldSize + padSize;
437 // Now print the actual field value.
438 EmitGlobalConstant(field, GblS);
440 // Insert padding - this may include padding to increase the size of the
441 // current field up to the ABI size (if the struct is not packed) as well
442 // as padding to ensure that the next field starts at the right offset.
443 GblS.emitZeros(padSize);
445 assert(sizeSoFar == cvsLayout->getSizeInBytes() &&
446 "Layout of constant struct may be incorrect!");
449 void ELFWriter::EmitGlobalConstant(const Constant *CV, ELFSection &GblS) {
450 const TargetData *TD = TM.getTargetData();
451 unsigned Size = TD->getTypeAllocSize(CV->getType());
453 if (const ConstantArray *CVA = dyn_cast<ConstantArray>(CV)) {
454 for (unsigned i = 0, e = CVA->getNumOperands(); i != e; ++i)
455 EmitGlobalConstant(CVA->getOperand(i), GblS);
457 } else if (isa<ConstantAggregateZero>(CV)) {
458 GblS.emitZeros(Size);
460 } else if (const ConstantStruct *CVS = dyn_cast<ConstantStruct>(CV)) {
461 EmitGlobalConstantStruct(CVS, GblS);
463 } else if (const ConstantFP *CFP = dyn_cast<ConstantFP>(CV)) {
464 APInt Val = CFP->getValueAPF().bitcastToAPInt();
465 if (CFP->getType()->isDoubleTy())
466 GblS.emitWord64(Val.getZExtValue());
467 else if (CFP->getType()->isFloatTy())
468 GblS.emitWord32(Val.getZExtValue());
469 else if (CFP->getType()->isX86_FP80Ty()) {
470 unsigned PadSize = TD->getTypeAllocSize(CFP->getType())-
471 TD->getTypeStoreSize(CFP->getType());
472 GblS.emitWordFP80(Val.getRawData(), PadSize);
473 } else if (CFP->getType()->isPPC_FP128Ty())
474 llvm_unreachable("PPC_FP128Ty global emission not implemented");
476 } else if (const ConstantInt *CI = dyn_cast<ConstantInt>(CV)) {
478 GblS.emitByte(CI->getZExtValue());
480 GblS.emitWord16(CI->getZExtValue());
482 GblS.emitWord32(CI->getZExtValue());
484 EmitGlobalConstantLargeInt(CI, GblS);
486 } else if (const ConstantVector *CP = dyn_cast<ConstantVector>(CV)) {
487 VectorType *PTy = CP->getType();
488 for (unsigned I = 0, E = PTy->getNumElements(); I < E; ++I)
489 EmitGlobalConstant(CP->getOperand(I), GblS);
491 } else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(CV)) {
492 // Resolve a constant expression which returns a (Constant, Offset)
493 // pair. If 'Res.first' is a GlobalValue, emit a relocation with
494 // the offset 'Res.second', otherwise emit a global constant like
495 // it is always done for not contant expression types.
496 CstExprResTy Res = ResolveConstantExpr(CE);
497 const Constant *Op = Res.first;
499 if (isa<GlobalValue>(Op))
500 EmitGlobalDataRelocation(cast<const GlobalValue>(Op),
501 TD->getTypeAllocSize(Op->getType()),
504 EmitGlobalConstant(Op, GblS);
507 } else if (CV->getType()->getTypeID() == Type::PointerTyID) {
508 // Fill the data entry with zeros or emit a relocation entry
509 if (isa<ConstantPointerNull>(CV))
510 GblS.emitZeros(Size);
512 EmitGlobalDataRelocation(cast<const GlobalValue>(CV),
515 } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(CV)) {
516 // This is a constant address for a global variable or function and
517 // therefore must be referenced using a relocation entry.
518 EmitGlobalDataRelocation(GV, Size, GblS);
523 raw_string_ostream ErrorMsg(msg);
524 ErrorMsg << "Constant unimp for type: " << *CV->getType();
525 report_fatal_error(ErrorMsg.str());
528 // ResolveConstantExpr - Resolve the constant expression until it stop
529 // yielding other constant expressions.
530 CstExprResTy ELFWriter::ResolveConstantExpr(const Constant *CV) {
531 const TargetData *TD = TM.getTargetData();
533 // There ins't constant expression inside others anymore
534 if (!isa<ConstantExpr>(CV))
535 return std::make_pair(CV, 0);
537 const ConstantExpr *CE = dyn_cast<ConstantExpr>(CV);
538 switch (CE->getOpcode()) {
539 case Instruction::BitCast:
540 return ResolveConstantExpr(CE->getOperand(0));
542 case Instruction::GetElementPtr: {
543 const Constant *ptrVal = CE->getOperand(0);
544 SmallVector<Value*, 8> idxVec(CE->op_begin()+1, CE->op_end());
545 int64_t Offset = TD->getIndexedOffset(ptrVal->getType(), &idxVec[0],
547 return std::make_pair(ptrVal, Offset);
549 case Instruction::IntToPtr: {
550 Constant *Op = CE->getOperand(0);
551 Op = ConstantExpr::getIntegerCast(Op, TD->getIntPtrType(CV->getContext()),
553 return ResolveConstantExpr(Op);
555 case Instruction::PtrToInt: {
556 Constant *Op = CE->getOperand(0);
557 Type *Ty = CE->getType();
559 // We can emit the pointer value into this slot if the slot is an
560 // integer slot greater or equal to the size of the pointer.
561 if (TD->getTypeAllocSize(Ty) == TD->getTypeAllocSize(Op->getType()))
562 return ResolveConstantExpr(Op);
564 llvm_unreachable("Integer size less then pointer size");
566 case Instruction::Add:
567 case Instruction::Sub: {
568 // Only handle cases where there's a constant expression with GlobalValue
569 // as first operand and ConstantInt as second, which are the cases we can
570 // solve direclty using a relocation entry. GlobalValue=Op0, CstInt=Op1
571 // 1) Instruction::Add => (global) + CstInt
572 // 2) Instruction::Sub => (global) + -CstInt
573 const Constant *Op0 = CE->getOperand(0);
574 const Constant *Op1 = CE->getOperand(1);
575 assert(isa<ConstantInt>(Op1) && "Op1 must be a ConstantInt");
577 CstExprResTy Res = ResolveConstantExpr(Op0);
578 assert(isa<GlobalValue>(Res.first) && "Op0 must be a GlobalValue");
580 const APInt &RHS = cast<ConstantInt>(Op1)->getValue();
581 switch (CE->getOpcode()) {
582 case Instruction::Add:
583 return std::make_pair(Res.first, RHS.getSExtValue());
584 case Instruction::Sub:
585 return std::make_pair(Res.first, (-RHS).getSExtValue());
590 report_fatal_error(CE->getOpcodeName() +
591 StringRef(": Unsupported ConstantExpr type"));
593 return std::make_pair(CV, 0); // silence warning
596 void ELFWriter::EmitGlobalDataRelocation(const GlobalValue *GV, unsigned Size,
597 ELFSection &GblS, int64_t Offset) {
598 // Create the relocation entry for the global value
599 MachineRelocation MR =
600 MachineRelocation::getGV(GblS.getCurrentPCOffset(),
601 TEW->getAbsoluteLabelMachineRelTy(),
602 const_cast<GlobalValue*>(GV),
605 // Fill the data entry with zeros
606 GblS.emitZeros(Size);
608 // Add the relocation entry for the current data section
609 GblS.addRelocation(MR);
612 void ELFWriter::EmitGlobalConstantLargeInt(const ConstantInt *CI,
614 const TargetData *TD = TM.getTargetData();
615 unsigned BitWidth = CI->getBitWidth();
616 assert(isPowerOf2_32(BitWidth) &&
617 "Non-power-of-2-sized integers not handled!");
619 const uint64_t *RawData = CI->getValue().getRawData();
621 for (unsigned i = 0, e = BitWidth / 64; i != e; ++i) {
622 Val = (TD->isBigEndian()) ? RawData[e - i - 1] : RawData[i];
627 /// EmitSpecialLLVMGlobal - Check to see if the specified global is a
628 /// special global used by LLVM. If so, emit it and return true, otherwise
629 /// do nothing and return false.
630 bool ELFWriter::EmitSpecialLLVMGlobal(const GlobalVariable *GV) {
631 if (GV->getName() == "llvm.used")
632 llvm_unreachable("not implemented yet");
634 // Ignore debug and non-emitted data. This handles llvm.compiler.used.
635 if (GV->getSection() == "llvm.metadata" ||
636 GV->hasAvailableExternallyLinkage())
639 if (!GV->hasAppendingLinkage()) return false;
641 assert(GV->hasInitializer() && "Not a special LLVM global!");
643 const TargetData *TD = TM.getTargetData();
644 unsigned Align = TD->getPointerPrefAlignment();
645 if (GV->getName() == "llvm.global_ctors") {
646 ELFSection &Ctor = getCtorSection();
647 Ctor.emitAlignment(Align);
648 EmitXXStructorList(GV->getInitializer(), Ctor);
652 if (GV->getName() == "llvm.global_dtors") {
653 ELFSection &Dtor = getDtorSection();
654 Dtor.emitAlignment(Align);
655 EmitXXStructorList(GV->getInitializer(), Dtor);
662 /// EmitXXStructorList - Emit the ctor or dtor list. This just emits out the
663 /// function pointers, ignoring the init priority.
664 void ELFWriter::EmitXXStructorList(const Constant *List, ELFSection &Xtor) {
665 // Should be an array of '{ i32, void ()* }' structs. The first value is the
666 // init priority, which we ignore.
667 if (List->isNullValue()) return;
668 const ConstantArray *InitList = cast<ConstantArray>(List);
669 for (unsigned i = 0, e = InitList->getNumOperands(); i != e; ++i) {
670 if (InitList->getOperand(i)->isNullValue())
672 ConstantStruct *CS = cast<ConstantStruct>(InitList->getOperand(i));
674 if (CS->getOperand(1)->isNullValue())
677 // Emit the function pointer.
678 EmitGlobalConstant(CS->getOperand(1), Xtor);
682 bool ELFWriter::runOnMachineFunction(MachineFunction &MF) {
683 // Nothing to do here, this is all done through the ElfCE object above.
687 /// doFinalization - Now that the module has been completely processed, emit
688 /// the ELF file to 'O'.
689 bool ELFWriter::doFinalization(Module &M) {
690 // Emit .data section placeholder
693 // Emit .bss section placeholder
696 // Build and emit data, bss and "common" sections.
697 for (Module::global_iterator I = M.global_begin(), E = M.global_end();
701 // Emit all pending globals
702 for (PendingGblsIter I = PendingGlobals.begin(), E = PendingGlobals.end();
706 // Emit all pending externals
707 for (PendingExtsIter I = PendingExternals.begin(), E = PendingExternals.end();
709 SymbolList.push_back(ELFSym::getExtSym(*I));
711 // Emit a symbol for each section created until now, skip null section
712 for (unsigned i = 1, e = SectionList.size(); i < e; ++i) {
713 ELFSection &ES = *SectionList[i];
714 ELFSym *SectionSym = ELFSym::getSectionSym();
715 SectionSym->SectionIdx = ES.SectionIdx;
716 SymbolList.push_back(SectionSym);
717 ES.Sym = SymbolList.back();
721 EmitStringTable(M.getModuleIdentifier());
723 // Emit the symbol table now, if non-empty.
726 // Emit the relocation sections.
729 // Emit the sections string table.
730 EmitSectionTableStringTable();
732 // Dump the sections and section table to the .o file.
733 OutputSectionsAndSectionTable();
738 // RelocateField - Patch relocatable field with 'Offset' in 'BO'
739 // using a 'Value' of known 'Size'
740 void ELFWriter::RelocateField(BinaryObject &BO, uint32_t Offset,
741 int64_t Value, unsigned Size) {
743 BO.fixWord32(Value, Offset);
745 BO.fixWord64(Value, Offset);
747 llvm_unreachable("don't know howto patch relocatable field");
750 /// EmitRelocations - Emit relocations
751 void ELFWriter::EmitRelocations() {
753 // True if the target uses the relocation entry to hold the addend,
754 // otherwise the addend is written directly to the relocatable field.
755 bool HasRelA = TEW->hasRelocationAddend();
757 // Create Relocation sections for each section which needs it.
758 for (unsigned i=0, e=SectionList.size(); i != e; ++i) {
759 ELFSection &S = *SectionList[i];
761 // This section does not have relocations
762 if (!S.hasRelocations()) continue;
763 ELFSection &RelSec = getRelocSection(S);
765 // 'Link' - Section hdr idx of the associated symbol table
766 // 'Info' - Section hdr idx of the section to which the relocation applies
767 ELFSection &SymTab = getSymbolTableSection();
768 RelSec.Link = SymTab.SectionIdx;
769 RelSec.Info = S.SectionIdx;
770 RelSec.EntSize = TEW->getRelocationEntrySize();
772 // Get the relocations from Section
773 std::vector<MachineRelocation> Relos = S.getRelocations();
774 for (std::vector<MachineRelocation>::iterator MRI = Relos.begin(),
775 MRE = Relos.end(); MRI != MRE; ++MRI) {
776 MachineRelocation &MR = *MRI;
778 // Relocatable field offset from the section start
779 unsigned RelOffset = MR.getMachineCodeOffset();
781 // Symbol index in the symbol table
784 // Target specific relocation field type and size
785 unsigned RelType = TEW->getRelocationType(MR.getRelocationType());
786 unsigned RelTySize = TEW->getRelocationTySize(RelType);
789 // There are several machine relocations types, and each one of
790 // them needs a different approach to retrieve the symbol table index.
791 if (MR.isGlobalValue()) {
792 const GlobalValue *G = MR.getGlobalValue();
793 int64_t GlobalOffset = MR.getConstantVal();
794 SymIdx = GblSymLookup[G];
795 if (G->hasPrivateLinkage()) {
796 // If the target uses a section offset in the relocation:
797 // SymIdx + Addend = section sym for global + section offset
798 unsigned SectionIdx = PrivateSyms[SymIdx]->SectionIdx;
799 Addend = PrivateSyms[SymIdx]->Value + GlobalOffset;
800 SymIdx = SectionList[SectionIdx]->getSymbolTableIndex();
802 Addend = TEW->getDefaultAddendForRelTy(RelType, GlobalOffset);
804 } else if (MR.isExternalSymbol()) {
805 const char *ExtSym = MR.getExternalSymbol();
806 SymIdx = ExtSymLookup[ExtSym];
807 Addend = TEW->getDefaultAddendForRelTy(RelType);
809 // Get the symbol index for the section symbol
810 unsigned SectionIdx = MR.getConstantVal();
811 SymIdx = SectionList[SectionIdx]->getSymbolTableIndex();
813 // The symbol offset inside the section
814 int64_t SymOffset = (int64_t)MR.getResultPointer();
816 // For pc relative relocations where symbols are defined in the same
817 // section they are referenced, ignore the relocation entry and patch
818 // the relocatable field with the symbol offset directly.
819 if (S.SectionIdx == SectionIdx && TEW->isPCRelativeRel(RelType)) {
820 int64_t Value = TEW->computeRelocation(SymOffset, RelOffset, RelType);
821 RelocateField(S, RelOffset, Value, RelTySize);
825 Addend = TEW->getDefaultAddendForRelTy(RelType, SymOffset);
828 // The target without addend on the relocation symbol must be
829 // patched in the relocation place itself to contain the addend
830 // otherwise write zeros to make sure there is no garbage there
831 RelocateField(S, RelOffset, HasRelA ? 0 : Addend, RelTySize);
833 // Get the relocation entry and emit to the relocation section
834 ELFRelocation Rel(RelOffset, SymIdx, RelType, HasRelA, Addend);
835 EmitRelocation(RelSec, Rel, HasRelA);
840 /// EmitRelocation - Write relocation 'Rel' to the relocation section 'Rel'
841 void ELFWriter::EmitRelocation(BinaryObject &RelSec, ELFRelocation &Rel,
843 RelSec.emitWord(Rel.getOffset());
844 RelSec.emitWord(Rel.getInfo(is64Bit));
846 RelSec.emitWord(Rel.getAddend());
849 /// EmitSymbol - Write symbol 'Sym' to the symbol table 'SymbolTable'
850 void ELFWriter::EmitSymbol(BinaryObject &SymbolTable, ELFSym &Sym) {
852 SymbolTable.emitWord32(Sym.NameIdx);
853 SymbolTable.emitByte(Sym.Info);
854 SymbolTable.emitByte(Sym.Other);
855 SymbolTable.emitWord16(Sym.SectionIdx);
856 SymbolTable.emitWord64(Sym.Value);
857 SymbolTable.emitWord64(Sym.Size);
859 SymbolTable.emitWord32(Sym.NameIdx);
860 SymbolTable.emitWord32(Sym.Value);
861 SymbolTable.emitWord32(Sym.Size);
862 SymbolTable.emitByte(Sym.Info);
863 SymbolTable.emitByte(Sym.Other);
864 SymbolTable.emitWord16(Sym.SectionIdx);
868 /// EmitSectionHeader - Write section 'Section' header in 'SHdrTab'
869 /// Section Header Table
870 void ELFWriter::EmitSectionHeader(BinaryObject &SHdrTab,
871 const ELFSection &SHdr) {
872 SHdrTab.emitWord32(SHdr.NameIdx);
873 SHdrTab.emitWord32(SHdr.Type);
875 SHdrTab.emitWord64(SHdr.Flags);
876 SHdrTab.emitWord(SHdr.Addr);
877 SHdrTab.emitWord(SHdr.Offset);
878 SHdrTab.emitWord64(SHdr.Size);
879 SHdrTab.emitWord32(SHdr.Link);
880 SHdrTab.emitWord32(SHdr.Info);
881 SHdrTab.emitWord64(SHdr.Align);
882 SHdrTab.emitWord64(SHdr.EntSize);
884 SHdrTab.emitWord32(SHdr.Flags);
885 SHdrTab.emitWord(SHdr.Addr);
886 SHdrTab.emitWord(SHdr.Offset);
887 SHdrTab.emitWord32(SHdr.Size);
888 SHdrTab.emitWord32(SHdr.Link);
889 SHdrTab.emitWord32(SHdr.Info);
890 SHdrTab.emitWord32(SHdr.Align);
891 SHdrTab.emitWord32(SHdr.EntSize);
895 /// EmitStringTable - If the current symbol table is non-empty, emit the string
897 void ELFWriter::EmitStringTable(const std::string &ModuleName) {
898 if (!SymbolList.size()) return; // Empty symbol table.
899 ELFSection &StrTab = getStringTableSection();
901 // Set the zero'th symbol to a null byte, as required.
904 // Walk on the symbol list and write symbol names into the string table.
906 for (ELFSymIter I=SymbolList.begin(), E=SymbolList.end(); I != E; ++I) {
910 if (Sym.isGlobalValue()) {
911 SmallString<40> NameStr;
912 Mang->getNameWithPrefix(NameStr, Sym.getGlobalValue(), false);
913 Name.append(NameStr.begin(), NameStr.end());
914 } else if (Sym.isExternalSym())
915 Name.append(Sym.getExternalSymbol());
916 else if (Sym.isFileType())
917 Name.append(ModuleName);
923 StrTab.emitString(Name);
925 // Keep track of the number of bytes emitted to this section.
926 Index += Name.size()+1;
929 assert(Index == StrTab.size());
933 // SortSymbols - On the symbol table local symbols must come before
934 // all other symbols with non-local bindings. The return value is
935 // the position of the first non local symbol.
936 unsigned ELFWriter::SortSymbols() {
937 unsigned FirstNonLocalSymbol;
938 std::vector<ELFSym*> LocalSyms, OtherSyms;
940 for (ELFSymIter I=SymbolList.begin(), E=SymbolList.end(); I != E; ++I) {
941 if ((*I)->isLocalBind())
942 LocalSyms.push_back(*I);
944 OtherSyms.push_back(*I);
947 FirstNonLocalSymbol = LocalSyms.size();
949 for (unsigned i = 0; i < FirstNonLocalSymbol; ++i)
950 SymbolList.push_back(LocalSyms[i]);
952 for (ELFSymIter I=OtherSyms.begin(), E=OtherSyms.end(); I != E; ++I)
953 SymbolList.push_back(*I);
958 return FirstNonLocalSymbol;
961 /// EmitSymbolTable - Emit the symbol table itself.
962 void ELFWriter::EmitSymbolTable() {
963 if (!SymbolList.size()) return; // Empty symbol table.
965 // Now that we have emitted the string table and know the offset into the
966 // string table of each symbol, emit the symbol table itself.
967 ELFSection &SymTab = getSymbolTableSection();
968 SymTab.Align = TEW->getPrefELFAlignment();
970 // Section Index of .strtab.
971 SymTab.Link = getStringTableSection().SectionIdx;
973 // Size of each symtab entry.
974 SymTab.EntSize = TEW->getSymTabEntrySize();
976 // Reorder the symbol table with local symbols first!
977 unsigned FirstNonLocalSymbol = SortSymbols();
979 // Emit all the symbols to the symbol table.
980 for (unsigned i = 0, e = SymbolList.size(); i < e; ++i) {
981 ELFSym &Sym = *SymbolList[i];
983 // Emit symbol to the symbol table
984 EmitSymbol(SymTab, Sym);
986 // Record the symbol table index for each symbol
987 if (Sym.isGlobalValue())
988 GblSymLookup[Sym.getGlobalValue()] = i;
989 else if (Sym.isExternalSym())
990 ExtSymLookup[Sym.getExternalSymbol()] = i;
992 // Keep track on the symbol index into the symbol table
996 // One greater than the symbol table index of the last local symbol
997 SymTab.Info = FirstNonLocalSymbol;
998 SymTab.Size = SymTab.size();
1001 /// EmitSectionTableStringTable - This method adds and emits a section for the
1002 /// ELF Section Table string table: the string table that holds all of the
1004 void ELFWriter::EmitSectionTableStringTable() {
1005 // First step: add the section for the string table to the list of sections:
1006 ELFSection &SHStrTab = getSectionHeaderStringTableSection();
1008 // Now that we know which section number is the .shstrtab section, update the
1009 // e_shstrndx entry in the ELF header.
1010 ElfHdr.fixWord16(SHStrTab.SectionIdx, ELFHdr_e_shstrndx_Offset);
1012 // Set the NameIdx of each section in the string table and emit the bytes for
1013 // the string table.
1016 for (ELFSectionIter I=SectionList.begin(), E=SectionList.end(); I != E; ++I) {
1017 ELFSection &S = *(*I);
1018 // Set the index into the table. Note if we have lots of entries with
1019 // common suffixes, we could memoize them here if we cared.
1021 SHStrTab.emitString(S.getName());
1023 // Keep track of the number of bytes emitted to this section.
1024 Index += S.getName().size()+1;
1027 // Set the size of .shstrtab now that we know what it is.
1028 assert(Index == SHStrTab.size());
1029 SHStrTab.Size = Index;
1032 /// OutputSectionsAndSectionTable - Now that we have constructed the file header
1033 /// and all of the sections, emit these to the ostream destination and emit the
1035 void ELFWriter::OutputSectionsAndSectionTable() {
1036 // Pass #1: Compute the file offset for each section.
1037 size_t FileOff = ElfHdr.size(); // File header first.
1039 // Adjust alignment of all section if needed, skip the null section.
1040 for (unsigned i=1, e=SectionList.size(); i < e; ++i) {
1041 ELFSection &ES = *SectionList[i];
1043 ES.Offset = FileOff;
1047 // Update Section size
1049 ES.Size = ES.size();
1051 // Align FileOff to whatever the alignment restrictions of the section are.
1053 FileOff = (FileOff+ES.Align-1) & ~(ES.Align-1);
1055 ES.Offset = FileOff;
1059 // Align Section Header.
1060 unsigned TableAlign = TEW->getPrefELFAlignment();
1061 FileOff = (FileOff+TableAlign-1) & ~(TableAlign-1);
1063 // Now that we know where all of the sections will be emitted, set the e_shnum
1064 // entry in the ELF header.
1065 ElfHdr.fixWord16(NumSections, ELFHdr_e_shnum_Offset);
1067 // Now that we know the offset in the file of the section table, update the
1068 // e_shoff address in the ELF header.
1069 ElfHdr.fixWord(FileOff, ELFHdr_e_shoff_Offset);
1071 // Now that we know all of the data in the file header, emit it and all of the
1073 O.write((char *)&ElfHdr.getData()[0], ElfHdr.size());
1074 FileOff = ElfHdr.size();
1076 // Section Header Table blob
1077 BinaryObject SHdrTable(isLittleEndian, is64Bit);
1079 // Emit all of sections to the file and build the section header table.
1080 for (ELFSectionIter I=SectionList.begin(), E=SectionList.end(); I != E; ++I) {
1081 ELFSection &S = *(*I);
1082 DEBUG(dbgs() << "SectionIdx: " << S.SectionIdx << ", Name: " << S.getName()
1083 << ", Size: " << S.Size << ", Offset: " << S.Offset
1084 << ", SectionData Size: " << S.size() << "\n");
1086 // Align FileOff to whatever the alignment restrictions of the section are.
1089 for (size_t NewFileOff = (FileOff+S.Align-1) & ~(S.Align-1);
1090 FileOff != NewFileOff; ++FileOff)
1093 O.write((char *)&S.getData()[0], S.Size);
1097 EmitSectionHeader(SHdrTable, S);
1100 // Align output for the section table.
1101 for (size_t NewFileOff = (FileOff+TableAlign-1) & ~(TableAlign-1);
1102 FileOff != NewFileOff; ++FileOff)
1105 // Emit the section table itself.
1106 O.write((char *)&SHdrTable.getData()[0], SHdrTable.size());