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/MC/MCAsmInfo.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/Mangler.h"
56 #include "llvm/Support/raw_ostream.h"
60 char ELFWriter::ID = 0;
62 /// AddELFWriter - Add the ELF writer to the function pass manager
63 ObjectCodeEmitter *llvm::AddELFWriter(PassManagerBase &PM,
66 ELFWriter *EW = new ELFWriter(O, TM);
68 return EW->getObjectCodeEmitter();
71 //===----------------------------------------------------------------------===//
72 // ELFWriter Implementation
73 //===----------------------------------------------------------------------===//
75 ELFWriter::ELFWriter(raw_ostream &o, TargetMachine &tm)
76 : MachineFunctionPass(&ID), O(o), TM(tm),
77 OutContext(*new MCContext()),
78 TLOF(TM.getTargetLowering()->getObjFileLowering()),
79 is64Bit(TM.getTargetData()->getPointerSizeInBits() == 64),
80 isLittleEndian(TM.getTargetData()->isLittleEndian()),
81 ElfHdr(isLittleEndian, is64Bit) {
83 MAI = TM.getMCAsmInfo();
84 TEW = TM.getELFWriterInfo();
86 // Create the object code emitter object for this target.
87 ElfCE = new ELFCodeEmitter(*this);
89 // Inital number of sections
93 ELFWriter::~ELFWriter() {
97 while(!SymbolList.empty()) {
98 delete SymbolList.back();
99 SymbolList.pop_back();
102 while(!PrivateSyms.empty()) {
103 delete PrivateSyms.back();
104 PrivateSyms.pop_back();
107 while(!SectionList.empty()) {
108 delete SectionList.back();
109 SectionList.pop_back();
112 // Release the name mangler object.
113 delete Mang; Mang = 0;
116 // doInitialization - Emit the file header and all of the global variables for
117 // the module to the ELF file.
118 bool ELFWriter::doInitialization(Module &M) {
119 // Initialize TargetLoweringObjectFile.
120 const_cast<TargetLoweringObjectFile&>(TLOF).Initialize(OutContext, TM);
122 Mang = new Mangler(M);
126 // Fields e_shnum e_shstrndx are only known after all section have
127 // been emitted. They locations in the ouput buffer are recorded so
128 // to be patched up later.
132 // emitWord method behaves differently for ELF32 and ELF64, writing
133 // 4 bytes in the former and 8 in the last for *_off and *_addr elf types
135 ElfHdr.emitByte(0x7f); // e_ident[EI_MAG0]
136 ElfHdr.emitByte('E'); // e_ident[EI_MAG1]
137 ElfHdr.emitByte('L'); // e_ident[EI_MAG2]
138 ElfHdr.emitByte('F'); // e_ident[EI_MAG3]
140 ElfHdr.emitByte(TEW->getEIClass()); // e_ident[EI_CLASS]
141 ElfHdr.emitByte(TEW->getEIData()); // e_ident[EI_DATA]
142 ElfHdr.emitByte(EV_CURRENT); // e_ident[EI_VERSION]
143 ElfHdr.emitAlignment(16); // e_ident[EI_NIDENT-EI_PAD]
145 ElfHdr.emitWord16(ET_REL); // e_type
146 ElfHdr.emitWord16(TEW->getEMachine()); // e_machine = target
147 ElfHdr.emitWord32(EV_CURRENT); // e_version
148 ElfHdr.emitWord(0); // e_entry, no entry point in .o file
149 ElfHdr.emitWord(0); // e_phoff, no program header for .o
150 ELFHdr_e_shoff_Offset = ElfHdr.size();
151 ElfHdr.emitWord(0); // e_shoff = sec hdr table off in bytes
152 ElfHdr.emitWord32(TEW->getEFlags()); // e_flags = whatever the target wants
153 ElfHdr.emitWord16(TEW->getHdrSize()); // e_ehsize = ELF header size
154 ElfHdr.emitWord16(0); // e_phentsize = prog header entry size
155 ElfHdr.emitWord16(0); // e_phnum = # prog header entries = 0
157 // e_shentsize = Section header entry size
158 ElfHdr.emitWord16(TEW->getSHdrSize());
160 // e_shnum = # of section header ents
161 ELFHdr_e_shnum_Offset = ElfHdr.size();
162 ElfHdr.emitWord16(0); // Placeholder
164 // e_shstrndx = Section # of '.shstrtab'
165 ELFHdr_e_shstrndx_Offset = ElfHdr.size();
166 ElfHdr.emitWord16(0); // Placeholder
168 // Add the null section, which is required to be first in the file.
171 // The first entry in the symtab is the null symbol and the second
172 // is a local symbol containing the module/file name
173 SymbolList.push_back(new ELFSym());
174 SymbolList.push_back(ELFSym::getFileSym());
179 // AddPendingGlobalSymbol - Add a global to be processed and to
180 // the global symbol lookup, use a zero index because the table
181 // index will be determined later.
182 void ELFWriter::AddPendingGlobalSymbol(const GlobalValue *GV,
183 bool AddToLookup /* = false */) {
184 PendingGlobals.insert(GV);
186 GblSymLookup[GV] = 0;
189 // AddPendingExternalSymbol - Add the external to be processed
190 // and to the external symbol lookup, use a zero index because
191 // the symbol table index will be determined later.
192 void ELFWriter::AddPendingExternalSymbol(const char *External) {
193 PendingExternals.insert(External);
194 ExtSymLookup[External] = 0;
197 ELFSection &ELFWriter::getDataSection() {
198 const MCSectionELF *Data = (const MCSectionELF *)TLOF.getDataSection();
199 return getSection(Data->getSectionName(), Data->getType(),
200 Data->getFlags(), 4);
203 ELFSection &ELFWriter::getBSSSection() {
204 const MCSectionELF *BSS = (const MCSectionELF *)TLOF.getBSSSection();
205 return getSection(BSS->getSectionName(), BSS->getType(), BSS->getFlags(), 4);
208 // getCtorSection - Get the static constructor section
209 ELFSection &ELFWriter::getCtorSection() {
210 const MCSectionELF *Ctor = (const MCSectionELF *)TLOF.getStaticCtorSection();
211 return getSection(Ctor->getSectionName(), Ctor->getType(), Ctor->getFlags());
214 // getDtorSection - Get the static destructor section
215 ELFSection &ELFWriter::getDtorSection() {
216 const MCSectionELF *Dtor = (const MCSectionELF *)TLOF.getStaticDtorSection();
217 return getSection(Dtor->getSectionName(), Dtor->getType(), Dtor->getFlags());
220 // getTextSection - Get the text section for the specified function
221 ELFSection &ELFWriter::getTextSection(Function *F) {
222 const MCSectionELF *Text =
223 (const MCSectionELF *)TLOF.SectionForGlobal(F, Mang, TM);
224 return getSection(Text->getSectionName(), Text->getType(), Text->getFlags());
227 // getJumpTableSection - Get a read only section for constants when
228 // emitting jump tables. TODO: add PIC support
229 ELFSection &ELFWriter::getJumpTableSection() {
230 const MCSectionELF *JT =
231 (const MCSectionELF *)TLOF.getSectionForConstant(SectionKind::getReadOnly());
232 return getSection(JT->getSectionName(), JT->getType(), JT->getFlags(),
233 TM.getTargetData()->getPointerABIAlignment());
236 // getConstantPoolSection - Get a constant pool section based on the machine
237 // constant pool entry type and relocation info.
238 ELFSection &ELFWriter::getConstantPoolSection(MachineConstantPoolEntry &CPE) {
240 switch (CPE.getRelocationInfo()) {
241 default: llvm_unreachable("Unknown section kind");
242 case 2: Kind = SectionKind::getReadOnlyWithRel(); break;
244 Kind = SectionKind::getReadOnlyWithRelLocal();
247 switch (TM.getTargetData()->getTypeAllocSize(CPE.getType())) {
248 case 4: Kind = SectionKind::getMergeableConst4(); break;
249 case 8: Kind = SectionKind::getMergeableConst8(); break;
250 case 16: Kind = SectionKind::getMergeableConst16(); break;
251 default: Kind = SectionKind::getMergeableConst(); break;
255 const MCSectionELF *CPSect =
256 (const MCSectionELF *)TLOF.getSectionForConstant(Kind);
257 return getSection(CPSect->getSectionName(), CPSect->getType(),
258 CPSect->getFlags(), CPE.getAlignment());
261 // getRelocSection - Return the relocation section of section 'S'. 'RelA'
262 // is true if the relocation section contains entries with addends.
263 ELFSection &ELFWriter::getRelocSection(ELFSection &S) {
264 unsigned SectionType = TEW->hasRelocationAddend() ?
265 ELFSection::SHT_RELA : ELFSection::SHT_REL;
267 std::string SectionName(".rel");
268 if (TEW->hasRelocationAddend())
269 SectionName.append("a");
270 SectionName.append(S.getName());
272 return getSection(SectionName, SectionType, 0, TEW->getPrefELFAlignment());
275 // getGlobalELFVisibility - Returns the ELF specific visibility type
276 unsigned ELFWriter::getGlobalELFVisibility(const GlobalValue *GV) {
277 switch (GV->getVisibility()) {
279 llvm_unreachable("unknown visibility type");
280 case GlobalValue::DefaultVisibility:
281 return ELFSym::STV_DEFAULT;
282 case GlobalValue::HiddenVisibility:
283 return ELFSym::STV_HIDDEN;
284 case GlobalValue::ProtectedVisibility:
285 return ELFSym::STV_PROTECTED;
290 // getGlobalELFBinding - Returns the ELF specific binding type
291 unsigned ELFWriter::getGlobalELFBinding(const GlobalValue *GV) {
292 if (GV->hasInternalLinkage())
293 return ELFSym::STB_LOCAL;
295 if (GV->isWeakForLinker() && !GV->hasCommonLinkage())
296 return ELFSym::STB_WEAK;
298 return ELFSym::STB_GLOBAL;
301 // getGlobalELFType - Returns the ELF specific type for a global
302 unsigned ELFWriter::getGlobalELFType(const GlobalValue *GV) {
303 if (GV->isDeclaration())
304 return ELFSym::STT_NOTYPE;
306 if (isa<Function>(GV))
307 return ELFSym::STT_FUNC;
309 return ELFSym::STT_OBJECT;
312 // IsELFUndefSym - True if the global value must be marked as a symbol
313 // which points to a SHN_UNDEF section. This means that the symbol has
314 // no definition on the module.
315 static bool IsELFUndefSym(const GlobalValue *GV) {
316 return GV->isDeclaration() || (isa<Function>(GV));
319 // AddToSymbolList - Update the symbol lookup and If the symbol is
320 // private add it to PrivateSyms list, otherwise to SymbolList.
321 void ELFWriter::AddToSymbolList(ELFSym *GblSym) {
322 assert(GblSym->isGlobalValue() && "Symbol must be a global value");
324 const GlobalValue *GV = GblSym->getGlobalValue();
325 if (GV->hasPrivateLinkage()) {
326 // For a private symbols, keep track of the index inside
327 // the private list since it will never go to the symbol
328 // table and won't be patched up later.
329 PrivateSyms.push_back(GblSym);
330 GblSymLookup[GV] = PrivateSyms.size()-1;
332 // Non private symbol are left with zero indices until
333 // they are patched up during the symbol table emition
334 // (where the indicies are created).
335 SymbolList.push_back(GblSym);
336 GblSymLookup[GV] = 0;
340 // EmitGlobal - Choose the right section for global and emit it
341 void ELFWriter::EmitGlobal(const GlobalValue *GV) {
343 // Check if the referenced symbol is already emitted
344 if (GblSymLookup.find(GV) != GblSymLookup.end())
347 // Handle ELF Bind, Visibility and Type for the current symbol
348 unsigned SymBind = getGlobalELFBinding(GV);
349 unsigned SymType = getGlobalELFType(GV);
350 bool IsUndefSym = IsELFUndefSym(GV);
352 ELFSym *GblSym = IsUndefSym ? ELFSym::getUndefGV(GV, SymBind)
353 : ELFSym::getGV(GV, SymBind, SymType, getGlobalELFVisibility(GV));
356 assert(isa<GlobalVariable>(GV) && "GV not a global variable!");
357 const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV);
359 // Handle special llvm globals
360 if (EmitSpecialLLVMGlobal(GVar))
363 // Get the ELF section where this global belongs from TLOF
364 const MCSectionELF *S =
365 (const MCSectionELF *)TLOF.SectionForGlobal(GV, Mang, TM);
367 getSection(S->getSectionName(), S->getType(), S->getFlags());
368 SectionKind Kind = S->getKind();
370 // The symbol align should update the section alignment if needed
371 const TargetData *TD = TM.getTargetData();
372 unsigned Align = TD->getPreferredAlignment(GVar);
373 unsigned Size = TD->getTypeAllocSize(GVar->getInitializer()->getType());
376 if (S->HasCommonSymbols()) { // Symbol must go to a common section
377 GblSym->SectionIdx = ELFSection::SHN_COMMON;
379 // A new linkonce section is created for each global in the
380 // common section, the default alignment is 1 and the symbol
381 // value contains its alignment.
383 GblSym->Value = Align;
385 } else if (Kind.isBSS() || Kind.isThreadBSS()) { // Symbol goes to BSS.
386 GblSym->SectionIdx = ES.SectionIdx;
388 // Update the size with alignment and the next object can
389 // start in the right offset in the section
390 if (Align) ES.Size = (ES.Size + Align-1) & ~(Align-1);
391 ES.Align = std::max(ES.Align, Align);
393 // GblSym->Value should contain the virtual offset inside the section.
394 // Virtual because the BSS space is not allocated on ELF objects
395 GblSym->Value = ES.Size;
398 } else { // The symbol must go to some kind of data section
399 GblSym->SectionIdx = ES.SectionIdx;
401 // GblSym->Value should contain the symbol offset inside the section,
402 // and all symbols should start on their required alignment boundary
403 ES.Align = std::max(ES.Align, Align);
404 ES.emitAlignment(Align);
405 GblSym->Value = ES.size();
407 // Emit the global to the data section 'ES'
408 EmitGlobalConstant(GVar->getInitializer(), ES);
412 AddToSymbolList(GblSym);
415 void ELFWriter::EmitGlobalConstantStruct(const ConstantStruct *CVS,
418 // Print the fields in successive locations. Pad to align if needed!
419 const TargetData *TD = TM.getTargetData();
420 unsigned Size = TD->getTypeAllocSize(CVS->getType());
421 const StructLayout *cvsLayout = TD->getStructLayout(CVS->getType());
422 uint64_t sizeSoFar = 0;
423 for (unsigned i = 0, e = CVS->getNumOperands(); i != e; ++i) {
424 const Constant* field = CVS->getOperand(i);
426 // Check if padding is needed and insert one or more 0s.
427 uint64_t fieldSize = TD->getTypeAllocSize(field->getType());
428 uint64_t padSize = ((i == e-1 ? Size : cvsLayout->getElementOffset(i+1))
429 - cvsLayout->getElementOffset(i)) - fieldSize;
430 sizeSoFar += fieldSize + padSize;
432 // Now print the actual field value.
433 EmitGlobalConstant(field, GblS);
435 // Insert padding - this may include padding to increase the size of the
436 // current field up to the ABI size (if the struct is not packed) as well
437 // as padding to ensure that the next field starts at the right offset.
438 GblS.emitZeros(padSize);
440 assert(sizeSoFar == cvsLayout->getSizeInBytes() &&
441 "Layout of constant struct may be incorrect!");
444 void ELFWriter::EmitGlobalConstant(const Constant *CV, ELFSection &GblS) {
445 const TargetData *TD = TM.getTargetData();
446 unsigned Size = TD->getTypeAllocSize(CV->getType());
448 if (const ConstantArray *CVA = dyn_cast<ConstantArray>(CV)) {
449 for (unsigned i = 0, e = CVA->getNumOperands(); i != e; ++i)
450 EmitGlobalConstant(CVA->getOperand(i), GblS);
452 } else if (isa<ConstantAggregateZero>(CV)) {
453 GblS.emitZeros(Size);
455 } else if (const ConstantStruct *CVS = dyn_cast<ConstantStruct>(CV)) {
456 EmitGlobalConstantStruct(CVS, GblS);
458 } else if (const ConstantFP *CFP = dyn_cast<ConstantFP>(CV)) {
459 APInt Val = CFP->getValueAPF().bitcastToAPInt();
460 if (CFP->getType()->isDoubleTy())
461 GblS.emitWord64(Val.getZExtValue());
462 else if (CFP->getType()->isFloatTy())
463 GblS.emitWord32(Val.getZExtValue());
464 else if (CFP->getType()->isX86_FP80Ty()) {
465 unsigned PadSize = TD->getTypeAllocSize(CFP->getType())-
466 TD->getTypeStoreSize(CFP->getType());
467 GblS.emitWordFP80(Val.getRawData(), PadSize);
468 } else if (CFP->getType()->isPPC_FP128Ty())
469 llvm_unreachable("PPC_FP128Ty global emission not implemented");
471 } else if (const ConstantInt *CI = dyn_cast<ConstantInt>(CV)) {
473 GblS.emitByte(CI->getZExtValue());
475 GblS.emitWord16(CI->getZExtValue());
477 GblS.emitWord32(CI->getZExtValue());
479 EmitGlobalConstantLargeInt(CI, GblS);
481 } else if (const ConstantVector *CP = dyn_cast<ConstantVector>(CV)) {
482 const VectorType *PTy = CP->getType();
483 for (unsigned I = 0, E = PTy->getNumElements(); I < E; ++I)
484 EmitGlobalConstant(CP->getOperand(I), GblS);
486 } else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(CV)) {
487 // Resolve a constant expression which returns a (Constant, Offset)
488 // pair. If 'Res.first' is a GlobalValue, emit a relocation with
489 // the offset 'Res.second', otherwise emit a global constant like
490 // it is always done for not contant expression types.
491 CstExprResTy Res = ResolveConstantExpr(CE);
492 const Constant *Op = Res.first;
494 if (isa<GlobalValue>(Op))
495 EmitGlobalDataRelocation(cast<const GlobalValue>(Op),
496 TD->getTypeAllocSize(Op->getType()),
499 EmitGlobalConstant(Op, GblS);
502 } else if (CV->getType()->getTypeID() == Type::PointerTyID) {
503 // Fill the data entry with zeros or emit a relocation entry
504 if (isa<ConstantPointerNull>(CV))
505 GblS.emitZeros(Size);
507 EmitGlobalDataRelocation(cast<const GlobalValue>(CV),
510 } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(CV)) {
511 // This is a constant address for a global variable or function and
512 // therefore must be referenced using a relocation entry.
513 EmitGlobalDataRelocation(GV, Size, GblS);
518 raw_string_ostream ErrorMsg(msg);
519 ErrorMsg << "Constant unimp for type: " << *CV->getType();
520 llvm_report_error(ErrorMsg.str());
523 // ResolveConstantExpr - Resolve the constant expression until it stop
524 // yielding other constant expressions.
525 CstExprResTy ELFWriter::ResolveConstantExpr(const Constant *CV) {
526 const TargetData *TD = TM.getTargetData();
528 // There ins't constant expression inside others anymore
529 if (!isa<ConstantExpr>(CV))
530 return std::make_pair(CV, 0);
532 const ConstantExpr *CE = dyn_cast<ConstantExpr>(CV);
533 switch (CE->getOpcode()) {
534 case Instruction::BitCast:
535 return ResolveConstantExpr(CE->getOperand(0));
537 case Instruction::GetElementPtr: {
538 const Constant *ptrVal = CE->getOperand(0);
539 SmallVector<Value*, 8> idxVec(CE->op_begin()+1, CE->op_end());
540 int64_t Offset = TD->getIndexedOffset(ptrVal->getType(), &idxVec[0],
542 return std::make_pair(ptrVal, Offset);
544 case Instruction::IntToPtr: {
545 Constant *Op = CE->getOperand(0);
546 Op = ConstantExpr::getIntegerCast(Op, TD->getIntPtrType(CV->getContext()),
548 return ResolveConstantExpr(Op);
550 case Instruction::PtrToInt: {
551 Constant *Op = CE->getOperand(0);
552 const Type *Ty = CE->getType();
554 // We can emit the pointer value into this slot if the slot is an
555 // integer slot greater or equal to the size of the pointer.
556 if (TD->getTypeAllocSize(Ty) == TD->getTypeAllocSize(Op->getType()))
557 return ResolveConstantExpr(Op);
559 llvm_unreachable("Integer size less then pointer size");
561 case Instruction::Add:
562 case Instruction::Sub: {
563 // Only handle cases where there's a constant expression with GlobalValue
564 // as first operand and ConstantInt as second, which are the cases we can
565 // solve direclty using a relocation entry. GlobalValue=Op0, CstInt=Op1
566 // 1) Instruction::Add => (global) + CstInt
567 // 2) Instruction::Sub => (global) + -CstInt
568 const Constant *Op0 = CE->getOperand(0);
569 const Constant *Op1 = CE->getOperand(1);
570 assert(isa<ConstantInt>(Op1) && "Op1 must be a ConstantInt");
572 CstExprResTy Res = ResolveConstantExpr(Op0);
573 assert(isa<GlobalValue>(Res.first) && "Op0 must be a GlobalValue");
575 const APInt &RHS = cast<ConstantInt>(Op1)->getValue();
576 switch (CE->getOpcode()) {
577 case Instruction::Add:
578 return std::make_pair(Res.first, RHS.getSExtValue());
579 case Instruction::Sub:
580 return std::make_pair(Res.first, (-RHS).getSExtValue());
585 std::string msg(CE->getOpcodeName());
586 raw_string_ostream ErrorMsg(msg);
587 ErrorMsg << ": Unsupported ConstantExpr type";
588 llvm_report_error(ErrorMsg.str());
590 return std::make_pair(CV, 0); // silence warning
593 void ELFWriter::EmitGlobalDataRelocation(const GlobalValue *GV, unsigned Size,
594 ELFSection &GblS, int64_t Offset) {
595 // Create the relocation entry for the global value
596 MachineRelocation MR =
597 MachineRelocation::getGV(GblS.getCurrentPCOffset(),
598 TEW->getAbsoluteLabelMachineRelTy(),
599 const_cast<GlobalValue*>(GV),
602 // Fill the data entry with zeros
603 GblS.emitZeros(Size);
605 // Add the relocation entry for the current data section
606 GblS.addRelocation(MR);
609 void ELFWriter::EmitGlobalConstantLargeInt(const ConstantInt *CI,
611 const TargetData *TD = TM.getTargetData();
612 unsigned BitWidth = CI->getBitWidth();
613 assert(isPowerOf2_32(BitWidth) &&
614 "Non-power-of-2-sized integers not handled!");
616 const uint64_t *RawData = CI->getValue().getRawData();
618 for (unsigned i = 0, e = BitWidth / 64; i != e; ++i) {
619 Val = (TD->isBigEndian()) ? RawData[e - i - 1] : RawData[i];
624 /// EmitSpecialLLVMGlobal - Check to see if the specified global is a
625 /// special global used by LLVM. If so, emit it and return true, otherwise
626 /// do nothing and return false.
627 bool ELFWriter::EmitSpecialLLVMGlobal(const GlobalVariable *GV) {
628 if (GV->getName() == "llvm.used")
629 llvm_unreachable("not implemented yet");
631 // Ignore debug and non-emitted data. This handles llvm.compiler.used.
632 if (GV->getSection() == "llvm.metadata" ||
633 GV->hasAvailableExternallyLinkage())
636 if (!GV->hasAppendingLinkage()) return false;
638 assert(GV->hasInitializer() && "Not a special LLVM global!");
640 const TargetData *TD = TM.getTargetData();
641 unsigned Align = TD->getPointerPrefAlignment();
642 if (GV->getName() == "llvm.global_ctors") {
643 ELFSection &Ctor = getCtorSection();
644 Ctor.emitAlignment(Align);
645 EmitXXStructorList(GV->getInitializer(), Ctor);
649 if (GV->getName() == "llvm.global_dtors") {
650 ELFSection &Dtor = getDtorSection();
651 Dtor.emitAlignment(Align);
652 EmitXXStructorList(GV->getInitializer(), Dtor);
659 /// EmitXXStructorList - Emit the ctor or dtor list. This just emits out the
660 /// function pointers, ignoring the init priority.
661 void ELFWriter::EmitXXStructorList(Constant *List, ELFSection &Xtor) {
662 // Should be an array of '{ int, void ()* }' structs. The first value is the
663 // init priority, which we ignore.
664 if (!isa<ConstantArray>(List)) return;
665 ConstantArray *InitList = cast<ConstantArray>(List);
666 for (unsigned i = 0, e = InitList->getNumOperands(); i != e; ++i)
667 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(InitList->getOperand(i))){
668 if (CS->getNumOperands() != 2) return; // Not array of 2-element structs.
670 if (CS->getOperand(1)->isNullValue())
671 return; // Found a null terminator, exit printing.
672 // Emit the function pointer.
673 EmitGlobalConstant(CS->getOperand(1), Xtor);
677 bool ELFWriter::runOnMachineFunction(MachineFunction &MF) {
678 // Nothing to do here, this is all done through the ElfCE object above.
682 /// doFinalization - Now that the module has been completely processed, emit
683 /// the ELF file to 'O'.
684 bool ELFWriter::doFinalization(Module &M) {
685 // Emit .data section placeholder
688 // Emit .bss section placeholder
691 // Build and emit data, bss and "common" sections.
692 for (Module::global_iterator I = M.global_begin(), E = M.global_end();
696 // Emit all pending globals
697 for (PendingGblsIter I = PendingGlobals.begin(), E = PendingGlobals.end();
701 // Emit all pending externals
702 for (PendingExtsIter I = PendingExternals.begin(), E = PendingExternals.end();
704 SymbolList.push_back(ELFSym::getExtSym(*I));
706 // Emit non-executable stack note
707 if (MAI->getNonexecutableStackDirective())
708 getNonExecStackSection();
710 // Emit a symbol for each section created until now, skip null section
711 for (unsigned i = 1, e = SectionList.size(); i < e; ++i) {
712 ELFSection &ES = *SectionList[i];
713 ELFSym *SectionSym = ELFSym::getSectionSym();
714 SectionSym->SectionIdx = ES.SectionIdx;
715 SymbolList.push_back(SectionSym);
716 ES.Sym = SymbolList.back();
720 EmitStringTable(M.getModuleIdentifier());
722 // Emit the symbol table now, if non-empty.
725 // Emit the relocation sections.
728 // Emit the sections string table.
729 EmitSectionTableStringTable();
731 // Dump the sections and section table to the .o file.
732 OutputSectionsAndSectionTable();
737 // RelocateField - Patch relocatable field with 'Offset' in 'BO'
738 // using a 'Value' of known 'Size'
739 void ELFWriter::RelocateField(BinaryObject &BO, uint32_t Offset,
740 int64_t Value, unsigned Size) {
742 BO.fixWord32(Value, Offset);
744 BO.fixWord64(Value, Offset);
746 llvm_unreachable("don't know howto patch relocatable field");
749 /// EmitRelocations - Emit relocations
750 void ELFWriter::EmitRelocations() {
752 // True if the target uses the relocation entry to hold the addend,
753 // otherwise the addend is written directly to the relocatable field.
754 bool HasRelA = TEW->hasRelocationAddend();
756 // Create Relocation sections for each section which needs it.
757 for (unsigned i=0, e=SectionList.size(); i != e; ++i) {
758 ELFSection &S = *SectionList[i];
760 // This section does not have relocations
761 if (!S.hasRelocations()) continue;
762 ELFSection &RelSec = getRelocSection(S);
764 // 'Link' - Section hdr idx of the associated symbol table
765 // 'Info' - Section hdr idx of the section to which the relocation applies
766 ELFSection &SymTab = getSymbolTableSection();
767 RelSec.Link = SymTab.SectionIdx;
768 RelSec.Info = S.SectionIdx;
769 RelSec.EntSize = TEW->getRelocationEntrySize();
771 // Get the relocations from Section
772 std::vector<MachineRelocation> Relos = S.getRelocations();
773 for (std::vector<MachineRelocation>::iterator MRI = Relos.begin(),
774 MRE = Relos.end(); MRI != MRE; ++MRI) {
775 MachineRelocation &MR = *MRI;
777 // Relocatable field offset from the section start
778 unsigned RelOffset = MR.getMachineCodeOffset();
780 // Symbol index in the symbol table
783 // Target specific relocation field type and size
784 unsigned RelType = TEW->getRelocationType(MR.getRelocationType());
785 unsigned RelTySize = TEW->getRelocationTySize(RelType);
788 // There are several machine relocations types, and each one of
789 // them needs a different approach to retrieve the symbol table index.
790 if (MR.isGlobalValue()) {
791 const GlobalValue *G = MR.getGlobalValue();
792 int64_t GlobalOffset = MR.getConstantVal();
793 SymIdx = GblSymLookup[G];
794 if (G->hasPrivateLinkage()) {
795 // If the target uses a section offset in the relocation:
796 // SymIdx + Addend = section sym for global + section offset
797 unsigned SectionIdx = PrivateSyms[SymIdx]->SectionIdx;
798 Addend = PrivateSyms[SymIdx]->Value + GlobalOffset;
799 SymIdx = SectionList[SectionIdx]->getSymbolTableIndex();
801 Addend = TEW->getDefaultAddendForRelTy(RelType, GlobalOffset);
803 } else if (MR.isExternalSymbol()) {
804 const char *ExtSym = MR.getExternalSymbol();
805 SymIdx = ExtSymLookup[ExtSym];
806 Addend = TEW->getDefaultAddendForRelTy(RelType);
808 // Get the symbol index for the section symbol
809 unsigned SectionIdx = MR.getConstantVal();
810 SymIdx = SectionList[SectionIdx]->getSymbolTableIndex();
812 // The symbol offset inside the section
813 int64_t SymOffset = (int64_t)MR.getResultPointer();
815 // For pc relative relocations where symbols are defined in the same
816 // section they are referenced, ignore the relocation entry and patch
817 // the relocatable field with the symbol offset directly.
818 if (S.SectionIdx == SectionIdx && TEW->isPCRelativeRel(RelType)) {
819 int64_t Value = TEW->computeRelocation(SymOffset, RelOffset, RelType);
820 RelocateField(S, RelOffset, Value, RelTySize);
824 Addend = TEW->getDefaultAddendForRelTy(RelType, SymOffset);
827 // The target without addend on the relocation symbol must be
828 // patched in the relocation place itself to contain the addend
829 // otherwise write zeros to make sure there is no garbage there
830 RelocateField(S, RelOffset, HasRelA ? 0 : Addend, RelTySize);
832 // Get the relocation entry and emit to the relocation section
833 ELFRelocation Rel(RelOffset, SymIdx, RelType, HasRelA, Addend);
834 EmitRelocation(RelSec, Rel, HasRelA);
839 /// EmitRelocation - Write relocation 'Rel' to the relocation section 'Rel'
840 void ELFWriter::EmitRelocation(BinaryObject &RelSec, ELFRelocation &Rel,
842 RelSec.emitWord(Rel.getOffset());
843 RelSec.emitWord(Rel.getInfo(is64Bit));
845 RelSec.emitWord(Rel.getAddend());
848 /// EmitSymbol - Write symbol 'Sym' to the symbol table 'SymbolTable'
849 void ELFWriter::EmitSymbol(BinaryObject &SymbolTable, ELFSym &Sym) {
851 SymbolTable.emitWord32(Sym.NameIdx);
852 SymbolTable.emitByte(Sym.Info);
853 SymbolTable.emitByte(Sym.Other);
854 SymbolTable.emitWord16(Sym.SectionIdx);
855 SymbolTable.emitWord64(Sym.Value);
856 SymbolTable.emitWord64(Sym.Size);
858 SymbolTable.emitWord32(Sym.NameIdx);
859 SymbolTable.emitWord32(Sym.Value);
860 SymbolTable.emitWord32(Sym.Size);
861 SymbolTable.emitByte(Sym.Info);
862 SymbolTable.emitByte(Sym.Other);
863 SymbolTable.emitWord16(Sym.SectionIdx);
867 /// EmitSectionHeader - Write section 'Section' header in 'SHdrTab'
868 /// Section Header Table
869 void ELFWriter::EmitSectionHeader(BinaryObject &SHdrTab,
870 const ELFSection &SHdr) {
871 SHdrTab.emitWord32(SHdr.NameIdx);
872 SHdrTab.emitWord32(SHdr.Type);
874 SHdrTab.emitWord64(SHdr.Flags);
875 SHdrTab.emitWord(SHdr.Addr);
876 SHdrTab.emitWord(SHdr.Offset);
877 SHdrTab.emitWord64(SHdr.Size);
878 SHdrTab.emitWord32(SHdr.Link);
879 SHdrTab.emitWord32(SHdr.Info);
880 SHdrTab.emitWord64(SHdr.Align);
881 SHdrTab.emitWord64(SHdr.EntSize);
883 SHdrTab.emitWord32(SHdr.Flags);
884 SHdrTab.emitWord(SHdr.Addr);
885 SHdrTab.emitWord(SHdr.Offset);
886 SHdrTab.emitWord32(SHdr.Size);
887 SHdrTab.emitWord32(SHdr.Link);
888 SHdrTab.emitWord32(SHdr.Info);
889 SHdrTab.emitWord32(SHdr.Align);
890 SHdrTab.emitWord32(SHdr.EntSize);
894 /// EmitStringTable - If the current symbol table is non-empty, emit the string
896 void ELFWriter::EmitStringTable(const std::string &ModuleName) {
897 if (!SymbolList.size()) return; // Empty symbol table.
898 ELFSection &StrTab = getStringTableSection();
900 // Set the zero'th symbol to a null byte, as required.
903 // Walk on the symbol list and write symbol names into the string table.
905 for (ELFSymIter I=SymbolList.begin(), E=SymbolList.end(); I != E; ++I) {
909 if (Sym.isGlobalValue())
910 Name.append(Mang->getMangledName(Sym.getGlobalValue()));
911 else if (Sym.isExternalSym())
912 Name.append(Sym.getExternalSymbol());
913 else if (Sym.isFileType())
914 Name.append(ModuleName);
920 StrTab.emitString(Name);
922 // Keep track of the number of bytes emitted to this section.
923 Index += Name.size()+1;
926 assert(Index == StrTab.size());
930 // SortSymbols - On the symbol table local symbols must come before
931 // all other symbols with non-local bindings. The return value is
932 // the position of the first non local symbol.
933 unsigned ELFWriter::SortSymbols() {
934 unsigned FirstNonLocalSymbol;
935 std::vector<ELFSym*> LocalSyms, OtherSyms;
937 for (ELFSymIter I=SymbolList.begin(), E=SymbolList.end(); I != E; ++I) {
938 if ((*I)->isLocalBind())
939 LocalSyms.push_back(*I);
941 OtherSyms.push_back(*I);
944 FirstNonLocalSymbol = LocalSyms.size();
946 for (unsigned i = 0; i < FirstNonLocalSymbol; ++i)
947 SymbolList.push_back(LocalSyms[i]);
949 for (ELFSymIter I=OtherSyms.begin(), E=OtherSyms.end(); I != E; ++I)
950 SymbolList.push_back(*I);
955 return FirstNonLocalSymbol;
958 /// EmitSymbolTable - Emit the symbol table itself.
959 void ELFWriter::EmitSymbolTable() {
960 if (!SymbolList.size()) return; // Empty symbol table.
962 // Now that we have emitted the string table and know the offset into the
963 // string table of each symbol, emit the symbol table itself.
964 ELFSection &SymTab = getSymbolTableSection();
965 SymTab.Align = TEW->getPrefELFAlignment();
967 // Section Index of .strtab.
968 SymTab.Link = getStringTableSection().SectionIdx;
970 // Size of each symtab entry.
971 SymTab.EntSize = TEW->getSymTabEntrySize();
973 // Reorder the symbol table with local symbols first!
974 unsigned FirstNonLocalSymbol = SortSymbols();
976 // Emit all the symbols to the symbol table.
977 for (unsigned i = 0, e = SymbolList.size(); i < e; ++i) {
978 ELFSym &Sym = *SymbolList[i];
980 // Emit symbol to the symbol table
981 EmitSymbol(SymTab, Sym);
983 // Record the symbol table index for each symbol
984 if (Sym.isGlobalValue())
985 GblSymLookup[Sym.getGlobalValue()] = i;
986 else if (Sym.isExternalSym())
987 ExtSymLookup[Sym.getExternalSymbol()] = i;
989 // Keep track on the symbol index into the symbol table
993 // One greater than the symbol table index of the last local symbol
994 SymTab.Info = FirstNonLocalSymbol;
995 SymTab.Size = SymTab.size();
998 /// EmitSectionTableStringTable - This method adds and emits a section for the
999 /// ELF Section Table string table: the string table that holds all of the
1001 void ELFWriter::EmitSectionTableStringTable() {
1002 // First step: add the section for the string table to the list of sections:
1003 ELFSection &SHStrTab = getSectionHeaderStringTableSection();
1005 // Now that we know which section number is the .shstrtab section, update the
1006 // e_shstrndx entry in the ELF header.
1007 ElfHdr.fixWord16(SHStrTab.SectionIdx, ELFHdr_e_shstrndx_Offset);
1009 // Set the NameIdx of each section in the string table and emit the bytes for
1010 // the string table.
1013 for (ELFSectionIter I=SectionList.begin(), E=SectionList.end(); I != E; ++I) {
1014 ELFSection &S = *(*I);
1015 // Set the index into the table. Note if we have lots of entries with
1016 // common suffixes, we could memoize them here if we cared.
1018 SHStrTab.emitString(S.getName());
1020 // Keep track of the number of bytes emitted to this section.
1021 Index += S.getName().size()+1;
1024 // Set the size of .shstrtab now that we know what it is.
1025 assert(Index == SHStrTab.size());
1026 SHStrTab.Size = Index;
1029 /// OutputSectionsAndSectionTable - Now that we have constructed the file header
1030 /// and all of the sections, emit these to the ostream destination and emit the
1032 void ELFWriter::OutputSectionsAndSectionTable() {
1033 // Pass #1: Compute the file offset for each section.
1034 size_t FileOff = ElfHdr.size(); // File header first.
1036 // Adjust alignment of all section if needed, skip the null section.
1037 for (unsigned i=1, e=SectionList.size(); i < e; ++i) {
1038 ELFSection &ES = *SectionList[i];
1040 ES.Offset = FileOff;
1044 // Update Section size
1046 ES.Size = ES.size();
1048 // Align FileOff to whatever the alignment restrictions of the section are.
1050 FileOff = (FileOff+ES.Align-1) & ~(ES.Align-1);
1052 ES.Offset = FileOff;
1056 // Align Section Header.
1057 unsigned TableAlign = TEW->getPrefELFAlignment();
1058 FileOff = (FileOff+TableAlign-1) & ~(TableAlign-1);
1060 // Now that we know where all of the sections will be emitted, set the e_shnum
1061 // entry in the ELF header.
1062 ElfHdr.fixWord16(NumSections, ELFHdr_e_shnum_Offset);
1064 // Now that we know the offset in the file of the section table, update the
1065 // e_shoff address in the ELF header.
1066 ElfHdr.fixWord(FileOff, ELFHdr_e_shoff_Offset);
1068 // Now that we know all of the data in the file header, emit it and all of the
1070 O.write((char *)&ElfHdr.getData()[0], ElfHdr.size());
1071 FileOff = ElfHdr.size();
1073 // Section Header Table blob
1074 BinaryObject SHdrTable(isLittleEndian, is64Bit);
1076 // Emit all of sections to the file and build the section header table.
1077 for (ELFSectionIter I=SectionList.begin(), E=SectionList.end(); I != E; ++I) {
1078 ELFSection &S = *(*I);
1079 DEBUG(errs() << "SectionIdx: " << S.SectionIdx << ", Name: " << S.getName()
1080 << ", Size: " << S.Size << ", Offset: " << S.Offset
1081 << ", SectionData Size: " << S.size() << "\n");
1083 // Align FileOff to whatever the alignment restrictions of the section are.
1086 for (size_t NewFileOff = (FileOff+S.Align-1) & ~(S.Align-1);
1087 FileOff != NewFileOff; ++FileOff)
1090 O.write((char *)&S.getData()[0], S.Size);
1094 EmitSectionHeader(SHdrTable, S);
1097 // Align output for the section table.
1098 for (size_t NewFileOff = (FileOff+TableAlign-1) & ~(TableAlign-1);
1099 FileOff != NewFileOff; ++FileOff)
1102 // Emit the section table itself.
1103 O.write((char *)&SHdrTable.getData()[0], SHdrTable.size());