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/Mangler.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/Support/Debug.h"
55 #include "llvm/Support/ErrorHandling.h"
56 #include "llvm/Support/raw_ostream.h"
57 #include "llvm/ADT/SmallString.h"
60 char ELFWriter::ID = 0;
62 //===----------------------------------------------------------------------===//
63 // ELFWriter Implementation
64 //===----------------------------------------------------------------------===//
66 ELFWriter::ELFWriter(raw_ostream &o, TargetMachine &tm)
67 : MachineFunctionPass(&ID), O(o), TM(tm),
68 OutContext(*new MCContext()),
69 TLOF(TM.getTargetLowering()->getObjFileLowering()),
70 is64Bit(TM.getTargetData()->getPointerSizeInBits() == 64),
71 isLittleEndian(TM.getTargetData()->isLittleEndian()),
72 ElfHdr(isLittleEndian, is64Bit) {
74 MAI = TM.getMCAsmInfo();
75 TEW = TM.getELFWriterInfo();
77 // Create the object code emitter object for this target.
78 ElfCE = new ELFCodeEmitter(*this);
80 // Inital number of sections
84 ELFWriter::~ELFWriter() {
88 while(!SymbolList.empty()) {
89 delete SymbolList.back();
90 SymbolList.pop_back();
93 while(!PrivateSyms.empty()) {
94 delete PrivateSyms.back();
95 PrivateSyms.pop_back();
98 while(!SectionList.empty()) {
99 delete SectionList.back();
100 SectionList.pop_back();
103 // Release the name mangler object.
104 delete Mang; Mang = 0;
107 // doInitialization - Emit the file header and all of the global variables for
108 // the module to the ELF file.
109 bool ELFWriter::doInitialization(Module &M) {
110 // Initialize TargetLoweringObjectFile.
111 const_cast<TargetLoweringObjectFile&>(TLOF).Initialize(OutContext, TM);
113 Mang = new Mangler(*MAI);
117 // Fields e_shnum e_shstrndx are only known after all section have
118 // been emitted. They locations in the ouput buffer are recorded so
119 // to be patched up later.
123 // emitWord method behaves differently for ELF32 and ELF64, writing
124 // 4 bytes in the former and 8 in the last for *_off and *_addr elf types
126 ElfHdr.emitByte(0x7f); // e_ident[EI_MAG0]
127 ElfHdr.emitByte('E'); // e_ident[EI_MAG1]
128 ElfHdr.emitByte('L'); // e_ident[EI_MAG2]
129 ElfHdr.emitByte('F'); // e_ident[EI_MAG3]
131 ElfHdr.emitByte(TEW->getEIClass()); // e_ident[EI_CLASS]
132 ElfHdr.emitByte(TEW->getEIData()); // e_ident[EI_DATA]
133 ElfHdr.emitByte(EV_CURRENT); // e_ident[EI_VERSION]
134 ElfHdr.emitAlignment(16); // e_ident[EI_NIDENT-EI_PAD]
136 ElfHdr.emitWord16(ET_REL); // e_type
137 ElfHdr.emitWord16(TEW->getEMachine()); // e_machine = target
138 ElfHdr.emitWord32(EV_CURRENT); // e_version
139 ElfHdr.emitWord(0); // e_entry, no entry point in .o file
140 ElfHdr.emitWord(0); // e_phoff, no program header for .o
141 ELFHdr_e_shoff_Offset = ElfHdr.size();
142 ElfHdr.emitWord(0); // e_shoff = sec hdr table off in bytes
143 ElfHdr.emitWord32(TEW->getEFlags()); // e_flags = whatever the target wants
144 ElfHdr.emitWord16(TEW->getHdrSize()); // e_ehsize = ELF header size
145 ElfHdr.emitWord16(0); // e_phentsize = prog header entry size
146 ElfHdr.emitWord16(0); // e_phnum = # prog header entries = 0
148 // e_shentsize = Section header entry size
149 ElfHdr.emitWord16(TEW->getSHdrSize());
151 // e_shnum = # of section header ents
152 ELFHdr_e_shnum_Offset = ElfHdr.size();
153 ElfHdr.emitWord16(0); // Placeholder
155 // e_shstrndx = Section # of '.shstrtab'
156 ELFHdr_e_shstrndx_Offset = ElfHdr.size();
157 ElfHdr.emitWord16(0); // Placeholder
159 // Add the null section, which is required to be first in the file.
162 // The first entry in the symtab is the null symbol and the second
163 // is a local symbol containing the module/file name
164 SymbolList.push_back(new ELFSym());
165 SymbolList.push_back(ELFSym::getFileSym());
170 // AddPendingGlobalSymbol - Add a global to be processed and to
171 // the global symbol lookup, use a zero index because the table
172 // index will be determined later.
173 void ELFWriter::AddPendingGlobalSymbol(const GlobalValue *GV,
174 bool AddToLookup /* = false */) {
175 PendingGlobals.insert(GV);
177 GblSymLookup[GV] = 0;
180 // AddPendingExternalSymbol - Add the external to be processed
181 // and to the external symbol lookup, use a zero index because
182 // the symbol table index will be determined later.
183 void ELFWriter::AddPendingExternalSymbol(const char *External) {
184 PendingExternals.insert(External);
185 ExtSymLookup[External] = 0;
188 ELFSection &ELFWriter::getDataSection() {
189 const MCSectionELF *Data = (const MCSectionELF *)TLOF.getDataSection();
190 return getSection(Data->getSectionName(), Data->getType(),
191 Data->getFlags(), 4);
194 ELFSection &ELFWriter::getBSSSection() {
195 const MCSectionELF *BSS = (const MCSectionELF *)TLOF.getBSSSection();
196 return getSection(BSS->getSectionName(), BSS->getType(), BSS->getFlags(), 4);
199 // getCtorSection - Get the static constructor section
200 ELFSection &ELFWriter::getCtorSection() {
201 const MCSectionELF *Ctor = (const MCSectionELF *)TLOF.getStaticCtorSection();
202 return getSection(Ctor->getSectionName(), Ctor->getType(), Ctor->getFlags());
205 // getDtorSection - Get the static destructor section
206 ELFSection &ELFWriter::getDtorSection() {
207 const MCSectionELF *Dtor = (const MCSectionELF *)TLOF.getStaticDtorSection();
208 return getSection(Dtor->getSectionName(), Dtor->getType(), Dtor->getFlags());
211 // getTextSection - Get the text section for the specified function
212 ELFSection &ELFWriter::getTextSection(Function *F) {
213 const MCSectionELF *Text =
214 (const MCSectionELF *)TLOF.SectionForGlobal(F, Mang, TM);
215 return getSection(Text->getSectionName(), Text->getType(), Text->getFlags());
218 // getJumpTableSection - Get a read only section for constants when
219 // emitting jump tables. TODO: add PIC support
220 ELFSection &ELFWriter::getJumpTableSection() {
221 const MCSectionELF *JT =
222 (const MCSectionELF *)TLOF.getSectionForConstant(SectionKind::getReadOnly());
223 return getSection(JT->getSectionName(), JT->getType(), JT->getFlags(),
224 TM.getTargetData()->getPointerABIAlignment());
227 // getConstantPoolSection - Get a constant pool section based on the machine
228 // constant pool entry type and relocation info.
229 ELFSection &ELFWriter::getConstantPoolSection(MachineConstantPoolEntry &CPE) {
231 switch (CPE.getRelocationInfo()) {
232 default: llvm_unreachable("Unknown section kind");
233 case 2: Kind = SectionKind::getReadOnlyWithRel(); break;
235 Kind = SectionKind::getReadOnlyWithRelLocal();
238 switch (TM.getTargetData()->getTypeAllocSize(CPE.getType())) {
239 case 4: Kind = SectionKind::getMergeableConst4(); break;
240 case 8: Kind = SectionKind::getMergeableConst8(); break;
241 case 16: Kind = SectionKind::getMergeableConst16(); break;
242 default: Kind = SectionKind::getMergeableConst(); break;
246 const MCSectionELF *CPSect =
247 (const MCSectionELF *)TLOF.getSectionForConstant(Kind);
248 return getSection(CPSect->getSectionName(), CPSect->getType(),
249 CPSect->getFlags(), CPE.getAlignment());
252 // getRelocSection - Return the relocation section of section 'S'. 'RelA'
253 // is true if the relocation section contains entries with addends.
254 ELFSection &ELFWriter::getRelocSection(ELFSection &S) {
255 unsigned SectionType = TEW->hasRelocationAddend() ?
256 ELFSection::SHT_RELA : ELFSection::SHT_REL;
258 std::string SectionName(".rel");
259 if (TEW->hasRelocationAddend())
260 SectionName.append("a");
261 SectionName.append(S.getName());
263 return getSection(SectionName, SectionType, 0, TEW->getPrefELFAlignment());
266 // getGlobalELFVisibility - Returns the ELF specific visibility type
267 unsigned ELFWriter::getGlobalELFVisibility(const GlobalValue *GV) {
268 switch (GV->getVisibility()) {
270 llvm_unreachable("unknown visibility type");
271 case GlobalValue::DefaultVisibility:
272 return ELFSym::STV_DEFAULT;
273 case GlobalValue::HiddenVisibility:
274 return ELFSym::STV_HIDDEN;
275 case GlobalValue::ProtectedVisibility:
276 return ELFSym::STV_PROTECTED;
281 // getGlobalELFBinding - Returns the ELF specific binding type
282 unsigned ELFWriter::getGlobalELFBinding(const GlobalValue *GV) {
283 if (GV->hasInternalLinkage())
284 return ELFSym::STB_LOCAL;
286 if (GV->isWeakForLinker() && !GV->hasCommonLinkage())
287 return ELFSym::STB_WEAK;
289 return ELFSym::STB_GLOBAL;
292 // getGlobalELFType - Returns the ELF specific type for a global
293 unsigned ELFWriter::getGlobalELFType(const GlobalValue *GV) {
294 if (GV->isDeclaration())
295 return ELFSym::STT_NOTYPE;
297 if (isa<Function>(GV))
298 return ELFSym::STT_FUNC;
300 return ELFSym::STT_OBJECT;
303 // IsELFUndefSym - True if the global value must be marked as a symbol
304 // which points to a SHN_UNDEF section. This means that the symbol has
305 // no definition on the module.
306 static bool IsELFUndefSym(const GlobalValue *GV) {
307 return GV->isDeclaration() || (isa<Function>(GV));
310 // AddToSymbolList - Update the symbol lookup and If the symbol is
311 // private add it to PrivateSyms list, otherwise to SymbolList.
312 void ELFWriter::AddToSymbolList(ELFSym *GblSym) {
313 assert(GblSym->isGlobalValue() && "Symbol must be a global value");
315 const GlobalValue *GV = GblSym->getGlobalValue();
316 if (GV->hasPrivateLinkage()) {
317 // For a private symbols, keep track of the index inside
318 // the private list since it will never go to the symbol
319 // table and won't be patched up later.
320 PrivateSyms.push_back(GblSym);
321 GblSymLookup[GV] = PrivateSyms.size()-1;
323 // Non private symbol are left with zero indices until
324 // they are patched up during the symbol table emition
325 // (where the indicies are created).
326 SymbolList.push_back(GblSym);
327 GblSymLookup[GV] = 0;
331 // EmitGlobal - Choose the right section for global and emit it
332 void ELFWriter::EmitGlobal(const GlobalValue *GV) {
334 // Check if the referenced symbol is already emitted
335 if (GblSymLookup.find(GV) != GblSymLookup.end())
338 // Handle ELF Bind, Visibility and Type for the current symbol
339 unsigned SymBind = getGlobalELFBinding(GV);
340 unsigned SymType = getGlobalELFType(GV);
341 bool IsUndefSym = IsELFUndefSym(GV);
343 ELFSym *GblSym = IsUndefSym ? ELFSym::getUndefGV(GV, SymBind)
344 : ELFSym::getGV(GV, SymBind, SymType, getGlobalELFVisibility(GV));
347 assert(isa<GlobalVariable>(GV) && "GV not a global variable!");
348 const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV);
350 // Handle special llvm globals
351 if (EmitSpecialLLVMGlobal(GVar))
354 // Get the ELF section where this global belongs from TLOF
355 const MCSectionELF *S =
356 (const MCSectionELF *)TLOF.SectionForGlobal(GV, Mang, TM);
358 getSection(S->getSectionName(), S->getType(), S->getFlags());
359 SectionKind Kind = S->getKind();
361 // The symbol align should update the section alignment if needed
362 const TargetData *TD = TM.getTargetData();
363 unsigned Align = TD->getPreferredAlignment(GVar);
364 unsigned Size = TD->getTypeAllocSize(GVar->getInitializer()->getType());
367 if (S->HasCommonSymbols()) { // Symbol must go to a common section
368 GblSym->SectionIdx = ELFSection::SHN_COMMON;
370 // A new linkonce section is created for each global in the
371 // common section, the default alignment is 1 and the symbol
372 // value contains its alignment.
374 GblSym->Value = Align;
376 } else if (Kind.isBSS() || Kind.isThreadBSS()) { // Symbol goes to BSS.
377 GblSym->SectionIdx = ES.SectionIdx;
379 // Update the size with alignment and the next object can
380 // start in the right offset in the section
381 if (Align) ES.Size = (ES.Size + Align-1) & ~(Align-1);
382 ES.Align = std::max(ES.Align, Align);
384 // GblSym->Value should contain the virtual offset inside the section.
385 // Virtual because the BSS space is not allocated on ELF objects
386 GblSym->Value = ES.Size;
389 } else { // The symbol must go to some kind of data section
390 GblSym->SectionIdx = ES.SectionIdx;
392 // GblSym->Value should contain the symbol offset inside the section,
393 // and all symbols should start on their required alignment boundary
394 ES.Align = std::max(ES.Align, Align);
395 ES.emitAlignment(Align);
396 GblSym->Value = ES.size();
398 // Emit the global to the data section 'ES'
399 EmitGlobalConstant(GVar->getInitializer(), ES);
403 AddToSymbolList(GblSym);
406 void ELFWriter::EmitGlobalConstantStruct(const ConstantStruct *CVS,
409 // Print the fields in successive locations. Pad to align if needed!
410 const TargetData *TD = TM.getTargetData();
411 unsigned Size = TD->getTypeAllocSize(CVS->getType());
412 const StructLayout *cvsLayout = TD->getStructLayout(CVS->getType());
413 uint64_t sizeSoFar = 0;
414 for (unsigned i = 0, e = CVS->getNumOperands(); i != e; ++i) {
415 const Constant* field = CVS->getOperand(i);
417 // Check if padding is needed and insert one or more 0s.
418 uint64_t fieldSize = TD->getTypeAllocSize(field->getType());
419 uint64_t padSize = ((i == e-1 ? Size : cvsLayout->getElementOffset(i+1))
420 - cvsLayout->getElementOffset(i)) - fieldSize;
421 sizeSoFar += fieldSize + padSize;
423 // Now print the actual field value.
424 EmitGlobalConstant(field, GblS);
426 // Insert padding - this may include padding to increase the size of the
427 // current field up to the ABI size (if the struct is not packed) as well
428 // as padding to ensure that the next field starts at the right offset.
429 GblS.emitZeros(padSize);
431 assert(sizeSoFar == cvsLayout->getSizeInBytes() &&
432 "Layout of constant struct may be incorrect!");
435 void ELFWriter::EmitGlobalConstant(const Constant *CV, ELFSection &GblS) {
436 const TargetData *TD = TM.getTargetData();
437 unsigned Size = TD->getTypeAllocSize(CV->getType());
439 if (const ConstantArray *CVA = dyn_cast<ConstantArray>(CV)) {
440 for (unsigned i = 0, e = CVA->getNumOperands(); i != e; ++i)
441 EmitGlobalConstant(CVA->getOperand(i), GblS);
443 } else if (isa<ConstantAggregateZero>(CV)) {
444 GblS.emitZeros(Size);
446 } else if (const ConstantStruct *CVS = dyn_cast<ConstantStruct>(CV)) {
447 EmitGlobalConstantStruct(CVS, GblS);
449 } else if (const ConstantFP *CFP = dyn_cast<ConstantFP>(CV)) {
450 APInt Val = CFP->getValueAPF().bitcastToAPInt();
451 if (CFP->getType()->isDoubleTy())
452 GblS.emitWord64(Val.getZExtValue());
453 else if (CFP->getType()->isFloatTy())
454 GblS.emitWord32(Val.getZExtValue());
455 else if (CFP->getType()->isX86_FP80Ty()) {
456 unsigned PadSize = TD->getTypeAllocSize(CFP->getType())-
457 TD->getTypeStoreSize(CFP->getType());
458 GblS.emitWordFP80(Val.getRawData(), PadSize);
459 } else if (CFP->getType()->isPPC_FP128Ty())
460 llvm_unreachable("PPC_FP128Ty global emission not implemented");
462 } else if (const ConstantInt *CI = dyn_cast<ConstantInt>(CV)) {
464 GblS.emitByte(CI->getZExtValue());
466 GblS.emitWord16(CI->getZExtValue());
468 GblS.emitWord32(CI->getZExtValue());
470 EmitGlobalConstantLargeInt(CI, GblS);
472 } else if (const ConstantVector *CP = dyn_cast<ConstantVector>(CV)) {
473 const VectorType *PTy = CP->getType();
474 for (unsigned I = 0, E = PTy->getNumElements(); I < E; ++I)
475 EmitGlobalConstant(CP->getOperand(I), GblS);
477 } else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(CV)) {
478 // Resolve a constant expression which returns a (Constant, Offset)
479 // pair. If 'Res.first' is a GlobalValue, emit a relocation with
480 // the offset 'Res.second', otherwise emit a global constant like
481 // it is always done for not contant expression types.
482 CstExprResTy Res = ResolveConstantExpr(CE);
483 const Constant *Op = Res.first;
485 if (isa<GlobalValue>(Op))
486 EmitGlobalDataRelocation(cast<const GlobalValue>(Op),
487 TD->getTypeAllocSize(Op->getType()),
490 EmitGlobalConstant(Op, GblS);
493 } else if (CV->getType()->getTypeID() == Type::PointerTyID) {
494 // Fill the data entry with zeros or emit a relocation entry
495 if (isa<ConstantPointerNull>(CV))
496 GblS.emitZeros(Size);
498 EmitGlobalDataRelocation(cast<const GlobalValue>(CV),
501 } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(CV)) {
502 // This is a constant address for a global variable or function and
503 // therefore must be referenced using a relocation entry.
504 EmitGlobalDataRelocation(GV, Size, GblS);
509 raw_string_ostream ErrorMsg(msg);
510 ErrorMsg << "Constant unimp for type: " << *CV->getType();
511 llvm_report_error(ErrorMsg.str());
514 // ResolveConstantExpr - Resolve the constant expression until it stop
515 // yielding other constant expressions.
516 CstExprResTy ELFWriter::ResolveConstantExpr(const Constant *CV) {
517 const TargetData *TD = TM.getTargetData();
519 // There ins't constant expression inside others anymore
520 if (!isa<ConstantExpr>(CV))
521 return std::make_pair(CV, 0);
523 const ConstantExpr *CE = dyn_cast<ConstantExpr>(CV);
524 switch (CE->getOpcode()) {
525 case Instruction::BitCast:
526 return ResolveConstantExpr(CE->getOperand(0));
528 case Instruction::GetElementPtr: {
529 const Constant *ptrVal = CE->getOperand(0);
530 SmallVector<Value*, 8> idxVec(CE->op_begin()+1, CE->op_end());
531 int64_t Offset = TD->getIndexedOffset(ptrVal->getType(), &idxVec[0],
533 return std::make_pair(ptrVal, Offset);
535 case Instruction::IntToPtr: {
536 Constant *Op = CE->getOperand(0);
537 Op = ConstantExpr::getIntegerCast(Op, TD->getIntPtrType(CV->getContext()),
539 return ResolveConstantExpr(Op);
541 case Instruction::PtrToInt: {
542 Constant *Op = CE->getOperand(0);
543 const Type *Ty = CE->getType();
545 // We can emit the pointer value into this slot if the slot is an
546 // integer slot greater or equal to the size of the pointer.
547 if (TD->getTypeAllocSize(Ty) == TD->getTypeAllocSize(Op->getType()))
548 return ResolveConstantExpr(Op);
550 llvm_unreachable("Integer size less then pointer size");
552 case Instruction::Add:
553 case Instruction::Sub: {
554 // Only handle cases where there's a constant expression with GlobalValue
555 // as first operand and ConstantInt as second, which are the cases we can
556 // solve direclty using a relocation entry. GlobalValue=Op0, CstInt=Op1
557 // 1) Instruction::Add => (global) + CstInt
558 // 2) Instruction::Sub => (global) + -CstInt
559 const Constant *Op0 = CE->getOperand(0);
560 const Constant *Op1 = CE->getOperand(1);
561 assert(isa<ConstantInt>(Op1) && "Op1 must be a ConstantInt");
563 CstExprResTy Res = ResolveConstantExpr(Op0);
564 assert(isa<GlobalValue>(Res.first) && "Op0 must be a GlobalValue");
566 const APInt &RHS = cast<ConstantInt>(Op1)->getValue();
567 switch (CE->getOpcode()) {
568 case Instruction::Add:
569 return std::make_pair(Res.first, RHS.getSExtValue());
570 case Instruction::Sub:
571 return std::make_pair(Res.first, (-RHS).getSExtValue());
576 std::string msg(CE->getOpcodeName());
577 raw_string_ostream ErrorMsg(msg);
578 ErrorMsg << ": Unsupported ConstantExpr type";
579 llvm_report_error(ErrorMsg.str());
581 return std::make_pair(CV, 0); // silence warning
584 void ELFWriter::EmitGlobalDataRelocation(const GlobalValue *GV, unsigned Size,
585 ELFSection &GblS, int64_t Offset) {
586 // Create the relocation entry for the global value
587 MachineRelocation MR =
588 MachineRelocation::getGV(GblS.getCurrentPCOffset(),
589 TEW->getAbsoluteLabelMachineRelTy(),
590 const_cast<GlobalValue*>(GV),
593 // Fill the data entry with zeros
594 GblS.emitZeros(Size);
596 // Add the relocation entry for the current data section
597 GblS.addRelocation(MR);
600 void ELFWriter::EmitGlobalConstantLargeInt(const ConstantInt *CI,
602 const TargetData *TD = TM.getTargetData();
603 unsigned BitWidth = CI->getBitWidth();
604 assert(isPowerOf2_32(BitWidth) &&
605 "Non-power-of-2-sized integers not handled!");
607 const uint64_t *RawData = CI->getValue().getRawData();
609 for (unsigned i = 0, e = BitWidth / 64; i != e; ++i) {
610 Val = (TD->isBigEndian()) ? RawData[e - i - 1] : RawData[i];
615 /// EmitSpecialLLVMGlobal - Check to see if the specified global is a
616 /// special global used by LLVM. If so, emit it and return true, otherwise
617 /// do nothing and return false.
618 bool ELFWriter::EmitSpecialLLVMGlobal(const GlobalVariable *GV) {
619 if (GV->getName() == "llvm.used")
620 llvm_unreachable("not implemented yet");
622 // Ignore debug and non-emitted data. This handles llvm.compiler.used.
623 if (GV->getSection() == "llvm.metadata" ||
624 GV->hasAvailableExternallyLinkage())
627 if (!GV->hasAppendingLinkage()) return false;
629 assert(GV->hasInitializer() && "Not a special LLVM global!");
631 const TargetData *TD = TM.getTargetData();
632 unsigned Align = TD->getPointerPrefAlignment();
633 if (GV->getName() == "llvm.global_ctors") {
634 ELFSection &Ctor = getCtorSection();
635 Ctor.emitAlignment(Align);
636 EmitXXStructorList(GV->getInitializer(), Ctor);
640 if (GV->getName() == "llvm.global_dtors") {
641 ELFSection &Dtor = getDtorSection();
642 Dtor.emitAlignment(Align);
643 EmitXXStructorList(GV->getInitializer(), Dtor);
650 /// EmitXXStructorList - Emit the ctor or dtor list. This just emits out the
651 /// function pointers, ignoring the init priority.
652 void ELFWriter::EmitXXStructorList(Constant *List, ELFSection &Xtor) {
653 // Should be an array of '{ int, void ()* }' structs. The first value is the
654 // init priority, which we ignore.
655 if (!isa<ConstantArray>(List)) return;
656 ConstantArray *InitList = cast<ConstantArray>(List);
657 for (unsigned i = 0, e = InitList->getNumOperands(); i != e; ++i)
658 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(InitList->getOperand(i))){
659 if (CS->getNumOperands() != 2) return; // Not array of 2-element structs.
661 if (CS->getOperand(1)->isNullValue())
662 return; // Found a null terminator, exit printing.
663 // Emit the function pointer.
664 EmitGlobalConstant(CS->getOperand(1), Xtor);
668 bool ELFWriter::runOnMachineFunction(MachineFunction &MF) {
669 // Nothing to do here, this is all done through the ElfCE object above.
673 /// doFinalization - Now that the module has been completely processed, emit
674 /// the ELF file to 'O'.
675 bool ELFWriter::doFinalization(Module &M) {
676 // Emit .data section placeholder
679 // Emit .bss section placeholder
682 // Build and emit data, bss and "common" sections.
683 for (Module::global_iterator I = M.global_begin(), E = M.global_end();
687 // Emit all pending globals
688 for (PendingGblsIter I = PendingGlobals.begin(), E = PendingGlobals.end();
692 // Emit all pending externals
693 for (PendingExtsIter I = PendingExternals.begin(), E = PendingExternals.end();
695 SymbolList.push_back(ELFSym::getExtSym(*I));
697 // Emit a symbol for each section created until now, skip null section
698 for (unsigned i = 1, e = SectionList.size(); i < e; ++i) {
699 ELFSection &ES = *SectionList[i];
700 ELFSym *SectionSym = ELFSym::getSectionSym();
701 SectionSym->SectionIdx = ES.SectionIdx;
702 SymbolList.push_back(SectionSym);
703 ES.Sym = SymbolList.back();
707 EmitStringTable(M.getModuleIdentifier());
709 // Emit the symbol table now, if non-empty.
712 // Emit the relocation sections.
715 // Emit the sections string table.
716 EmitSectionTableStringTable();
718 // Dump the sections and section table to the .o file.
719 OutputSectionsAndSectionTable();
724 // RelocateField - Patch relocatable field with 'Offset' in 'BO'
725 // using a 'Value' of known 'Size'
726 void ELFWriter::RelocateField(BinaryObject &BO, uint32_t Offset,
727 int64_t Value, unsigned Size) {
729 BO.fixWord32(Value, Offset);
731 BO.fixWord64(Value, Offset);
733 llvm_unreachable("don't know howto patch relocatable field");
736 /// EmitRelocations - Emit relocations
737 void ELFWriter::EmitRelocations() {
739 // True if the target uses the relocation entry to hold the addend,
740 // otherwise the addend is written directly to the relocatable field.
741 bool HasRelA = TEW->hasRelocationAddend();
743 // Create Relocation sections for each section which needs it.
744 for (unsigned i=0, e=SectionList.size(); i != e; ++i) {
745 ELFSection &S = *SectionList[i];
747 // This section does not have relocations
748 if (!S.hasRelocations()) continue;
749 ELFSection &RelSec = getRelocSection(S);
751 // 'Link' - Section hdr idx of the associated symbol table
752 // 'Info' - Section hdr idx of the section to which the relocation applies
753 ELFSection &SymTab = getSymbolTableSection();
754 RelSec.Link = SymTab.SectionIdx;
755 RelSec.Info = S.SectionIdx;
756 RelSec.EntSize = TEW->getRelocationEntrySize();
758 // Get the relocations from Section
759 std::vector<MachineRelocation> Relos = S.getRelocations();
760 for (std::vector<MachineRelocation>::iterator MRI = Relos.begin(),
761 MRE = Relos.end(); MRI != MRE; ++MRI) {
762 MachineRelocation &MR = *MRI;
764 // Relocatable field offset from the section start
765 unsigned RelOffset = MR.getMachineCodeOffset();
767 // Symbol index in the symbol table
770 // Target specific relocation field type and size
771 unsigned RelType = TEW->getRelocationType(MR.getRelocationType());
772 unsigned RelTySize = TEW->getRelocationTySize(RelType);
775 // There are several machine relocations types, and each one of
776 // them needs a different approach to retrieve the symbol table index.
777 if (MR.isGlobalValue()) {
778 const GlobalValue *G = MR.getGlobalValue();
779 int64_t GlobalOffset = MR.getConstantVal();
780 SymIdx = GblSymLookup[G];
781 if (G->hasPrivateLinkage()) {
782 // If the target uses a section offset in the relocation:
783 // SymIdx + Addend = section sym for global + section offset
784 unsigned SectionIdx = PrivateSyms[SymIdx]->SectionIdx;
785 Addend = PrivateSyms[SymIdx]->Value + GlobalOffset;
786 SymIdx = SectionList[SectionIdx]->getSymbolTableIndex();
788 Addend = TEW->getDefaultAddendForRelTy(RelType, GlobalOffset);
790 } else if (MR.isExternalSymbol()) {
791 const char *ExtSym = MR.getExternalSymbol();
792 SymIdx = ExtSymLookup[ExtSym];
793 Addend = TEW->getDefaultAddendForRelTy(RelType);
795 // Get the symbol index for the section symbol
796 unsigned SectionIdx = MR.getConstantVal();
797 SymIdx = SectionList[SectionIdx]->getSymbolTableIndex();
799 // The symbol offset inside the section
800 int64_t SymOffset = (int64_t)MR.getResultPointer();
802 // For pc relative relocations where symbols are defined in the same
803 // section they are referenced, ignore the relocation entry and patch
804 // the relocatable field with the symbol offset directly.
805 if (S.SectionIdx == SectionIdx && TEW->isPCRelativeRel(RelType)) {
806 int64_t Value = TEW->computeRelocation(SymOffset, RelOffset, RelType);
807 RelocateField(S, RelOffset, Value, RelTySize);
811 Addend = TEW->getDefaultAddendForRelTy(RelType, SymOffset);
814 // The target without addend on the relocation symbol must be
815 // patched in the relocation place itself to contain the addend
816 // otherwise write zeros to make sure there is no garbage there
817 RelocateField(S, RelOffset, HasRelA ? 0 : Addend, RelTySize);
819 // Get the relocation entry and emit to the relocation section
820 ELFRelocation Rel(RelOffset, SymIdx, RelType, HasRelA, Addend);
821 EmitRelocation(RelSec, Rel, HasRelA);
826 /// EmitRelocation - Write relocation 'Rel' to the relocation section 'Rel'
827 void ELFWriter::EmitRelocation(BinaryObject &RelSec, ELFRelocation &Rel,
829 RelSec.emitWord(Rel.getOffset());
830 RelSec.emitWord(Rel.getInfo(is64Bit));
832 RelSec.emitWord(Rel.getAddend());
835 /// EmitSymbol - Write symbol 'Sym' to the symbol table 'SymbolTable'
836 void ELFWriter::EmitSymbol(BinaryObject &SymbolTable, ELFSym &Sym) {
838 SymbolTable.emitWord32(Sym.NameIdx);
839 SymbolTable.emitByte(Sym.Info);
840 SymbolTable.emitByte(Sym.Other);
841 SymbolTable.emitWord16(Sym.SectionIdx);
842 SymbolTable.emitWord64(Sym.Value);
843 SymbolTable.emitWord64(Sym.Size);
845 SymbolTable.emitWord32(Sym.NameIdx);
846 SymbolTable.emitWord32(Sym.Value);
847 SymbolTable.emitWord32(Sym.Size);
848 SymbolTable.emitByte(Sym.Info);
849 SymbolTable.emitByte(Sym.Other);
850 SymbolTable.emitWord16(Sym.SectionIdx);
854 /// EmitSectionHeader - Write section 'Section' header in 'SHdrTab'
855 /// Section Header Table
856 void ELFWriter::EmitSectionHeader(BinaryObject &SHdrTab,
857 const ELFSection &SHdr) {
858 SHdrTab.emitWord32(SHdr.NameIdx);
859 SHdrTab.emitWord32(SHdr.Type);
861 SHdrTab.emitWord64(SHdr.Flags);
862 SHdrTab.emitWord(SHdr.Addr);
863 SHdrTab.emitWord(SHdr.Offset);
864 SHdrTab.emitWord64(SHdr.Size);
865 SHdrTab.emitWord32(SHdr.Link);
866 SHdrTab.emitWord32(SHdr.Info);
867 SHdrTab.emitWord64(SHdr.Align);
868 SHdrTab.emitWord64(SHdr.EntSize);
870 SHdrTab.emitWord32(SHdr.Flags);
871 SHdrTab.emitWord(SHdr.Addr);
872 SHdrTab.emitWord(SHdr.Offset);
873 SHdrTab.emitWord32(SHdr.Size);
874 SHdrTab.emitWord32(SHdr.Link);
875 SHdrTab.emitWord32(SHdr.Info);
876 SHdrTab.emitWord32(SHdr.Align);
877 SHdrTab.emitWord32(SHdr.EntSize);
881 /// EmitStringTable - If the current symbol table is non-empty, emit the string
883 void ELFWriter::EmitStringTable(const std::string &ModuleName) {
884 if (!SymbolList.size()) return; // Empty symbol table.
885 ELFSection &StrTab = getStringTableSection();
887 // Set the zero'th symbol to a null byte, as required.
890 // Walk on the symbol list and write symbol names into the string table.
892 for (ELFSymIter I=SymbolList.begin(), E=SymbolList.end(); I != E; ++I) {
896 if (Sym.isGlobalValue()) {
897 SmallString<40> NameStr;
898 Mang->getNameWithPrefix(NameStr, Sym.getGlobalValue(), false);
899 Name.append(NameStr.begin(), NameStr.end());
900 } else if (Sym.isExternalSym())
901 Name.append(Sym.getExternalSymbol());
902 else if (Sym.isFileType())
903 Name.append(ModuleName);
909 StrTab.emitString(Name);
911 // Keep track of the number of bytes emitted to this section.
912 Index += Name.size()+1;
915 assert(Index == StrTab.size());
919 // SortSymbols - On the symbol table local symbols must come before
920 // all other symbols with non-local bindings. The return value is
921 // the position of the first non local symbol.
922 unsigned ELFWriter::SortSymbols() {
923 unsigned FirstNonLocalSymbol;
924 std::vector<ELFSym*> LocalSyms, OtherSyms;
926 for (ELFSymIter I=SymbolList.begin(), E=SymbolList.end(); I != E; ++I) {
927 if ((*I)->isLocalBind())
928 LocalSyms.push_back(*I);
930 OtherSyms.push_back(*I);
933 FirstNonLocalSymbol = LocalSyms.size();
935 for (unsigned i = 0; i < FirstNonLocalSymbol; ++i)
936 SymbolList.push_back(LocalSyms[i]);
938 for (ELFSymIter I=OtherSyms.begin(), E=OtherSyms.end(); I != E; ++I)
939 SymbolList.push_back(*I);
944 return FirstNonLocalSymbol;
947 /// EmitSymbolTable - Emit the symbol table itself.
948 void ELFWriter::EmitSymbolTable() {
949 if (!SymbolList.size()) return; // Empty symbol table.
951 // Now that we have emitted the string table and know the offset into the
952 // string table of each symbol, emit the symbol table itself.
953 ELFSection &SymTab = getSymbolTableSection();
954 SymTab.Align = TEW->getPrefELFAlignment();
956 // Section Index of .strtab.
957 SymTab.Link = getStringTableSection().SectionIdx;
959 // Size of each symtab entry.
960 SymTab.EntSize = TEW->getSymTabEntrySize();
962 // Reorder the symbol table with local symbols first!
963 unsigned FirstNonLocalSymbol = SortSymbols();
965 // Emit all the symbols to the symbol table.
966 for (unsigned i = 0, e = SymbolList.size(); i < e; ++i) {
967 ELFSym &Sym = *SymbolList[i];
969 // Emit symbol to the symbol table
970 EmitSymbol(SymTab, Sym);
972 // Record the symbol table index for each symbol
973 if (Sym.isGlobalValue())
974 GblSymLookup[Sym.getGlobalValue()] = i;
975 else if (Sym.isExternalSym())
976 ExtSymLookup[Sym.getExternalSymbol()] = i;
978 // Keep track on the symbol index into the symbol table
982 // One greater than the symbol table index of the last local symbol
983 SymTab.Info = FirstNonLocalSymbol;
984 SymTab.Size = SymTab.size();
987 /// EmitSectionTableStringTable - This method adds and emits a section for the
988 /// ELF Section Table string table: the string table that holds all of the
990 void ELFWriter::EmitSectionTableStringTable() {
991 // First step: add the section for the string table to the list of sections:
992 ELFSection &SHStrTab = getSectionHeaderStringTableSection();
994 // Now that we know which section number is the .shstrtab section, update the
995 // e_shstrndx entry in the ELF header.
996 ElfHdr.fixWord16(SHStrTab.SectionIdx, ELFHdr_e_shstrndx_Offset);
998 // Set the NameIdx of each section in the string table and emit the bytes for
1002 for (ELFSectionIter I=SectionList.begin(), E=SectionList.end(); I != E; ++I) {
1003 ELFSection &S = *(*I);
1004 // Set the index into the table. Note if we have lots of entries with
1005 // common suffixes, we could memoize them here if we cared.
1007 SHStrTab.emitString(S.getName());
1009 // Keep track of the number of bytes emitted to this section.
1010 Index += S.getName().size()+1;
1013 // Set the size of .shstrtab now that we know what it is.
1014 assert(Index == SHStrTab.size());
1015 SHStrTab.Size = Index;
1018 /// OutputSectionsAndSectionTable - Now that we have constructed the file header
1019 /// and all of the sections, emit these to the ostream destination and emit the
1021 void ELFWriter::OutputSectionsAndSectionTable() {
1022 // Pass #1: Compute the file offset for each section.
1023 size_t FileOff = ElfHdr.size(); // File header first.
1025 // Adjust alignment of all section if needed, skip the null section.
1026 for (unsigned i=1, e=SectionList.size(); i < e; ++i) {
1027 ELFSection &ES = *SectionList[i];
1029 ES.Offset = FileOff;
1033 // Update Section size
1035 ES.Size = ES.size();
1037 // Align FileOff to whatever the alignment restrictions of the section are.
1039 FileOff = (FileOff+ES.Align-1) & ~(ES.Align-1);
1041 ES.Offset = FileOff;
1045 // Align Section Header.
1046 unsigned TableAlign = TEW->getPrefELFAlignment();
1047 FileOff = (FileOff+TableAlign-1) & ~(TableAlign-1);
1049 // Now that we know where all of the sections will be emitted, set the e_shnum
1050 // entry in the ELF header.
1051 ElfHdr.fixWord16(NumSections, ELFHdr_e_shnum_Offset);
1053 // Now that we know the offset in the file of the section table, update the
1054 // e_shoff address in the ELF header.
1055 ElfHdr.fixWord(FileOff, ELFHdr_e_shoff_Offset);
1057 // Now that we know all of the data in the file header, emit it and all of the
1059 O.write((char *)&ElfHdr.getData()[0], ElfHdr.size());
1060 FileOff = ElfHdr.size();
1062 // Section Header Table blob
1063 BinaryObject SHdrTable(isLittleEndian, is64Bit);
1065 // Emit all of sections to the file and build the section header table.
1066 for (ELFSectionIter I=SectionList.begin(), E=SectionList.end(); I != E; ++I) {
1067 ELFSection &S = *(*I);
1068 DEBUG(dbgs() << "SectionIdx: " << S.SectionIdx << ", Name: " << S.getName()
1069 << ", Size: " << S.Size << ", Offset: " << S.Offset
1070 << ", SectionData Size: " << S.size() << "\n");
1072 // Align FileOff to whatever the alignment restrictions of the section are.
1075 for (size_t NewFileOff = (FileOff+S.Align-1) & ~(S.Align-1);
1076 FileOff != NewFileOff; ++FileOff)
1079 O.write((char *)&S.getData()[0], S.Size);
1083 EmitSectionHeader(SHdrTable, S);
1086 // Align output for the section table.
1087 for (size_t NewFileOff = (FileOff+TableAlign-1) & ~(TableAlign-1);
1088 FileOff != NewFileOff; ++FileOff)
1091 // Emit the section table itself.
1092 O.write((char *)&SHdrTable.getData()[0], SHdrTable.size());