1 //===-- ELFWriter.cpp - Target-independent ELF Writer code ----------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements the target-independent ELF writer. This file writes out
11 // the ELF file in the following order:
14 // #2. '.text' section
15 // #3. '.data' section
16 // #4. '.bss' section (conceptual position in file)
18 // #X. '.shstrtab' section
21 // The entries in the section table are laid out as:
22 // #0. Null entry [required]
23 // #1. ".text" entry - the program code
24 // #2. ".data" entry - global variables with initializers. [ if needed ]
25 // #3. ".bss" entry - global variables without initializers. [ if needed ]
27 // #N. ".shstrtab" entry - String table for the section names.
29 //===----------------------------------------------------------------------===//
31 #define DEBUG_TYPE "elfwriter"
33 #include "ELFWriter.h"
34 #include "ELFCodeEmitter.h"
35 #include "llvm/Constants.h"
36 #include "llvm/Module.h"
37 #include "llvm/PassManager.h"
38 #include "llvm/DerivedTypes.h"
39 #include "llvm/CodeGen/BinaryObject.h"
40 #include "llvm/CodeGen/FileWriters.h"
41 #include "llvm/CodeGen/MachineCodeEmitter.h"
42 #include "llvm/CodeGen/ObjectCodeEmitter.h"
43 #include "llvm/CodeGen/MachineCodeEmitter.h"
44 #include "llvm/CodeGen/MachineConstantPool.h"
45 #include "llvm/MC/MCContext.h"
46 #include "llvm/MC/MCSectionELF.h"
47 #include "llvm/Target/TargetAsmInfo.h"
48 #include "llvm/Target/TargetData.h"
49 #include "llvm/Target/TargetELFWriterInfo.h"
50 #include "llvm/Target/TargetLowering.h"
51 #include "llvm/Target/TargetLoweringObjectFile.h"
52 #include "llvm/Target/TargetMachine.h"
53 #include "llvm/Support/Mangler.h"
54 #include "llvm/Support/Streams.h"
55 #include "llvm/Support/raw_ostream.h"
56 #include "llvm/Support/Debug.h"
57 #include "llvm/Support/ErrorHandling.h"
61 char ELFWriter::ID = 0;
63 /// AddELFWriter - Add the ELF writer to the function pass manager
64 ObjectCodeEmitter *llvm::AddELFWriter(PassManagerBase &PM,
67 ELFWriter *EW = new ELFWriter(O, TM);
69 return EW->getObjectCodeEmitter();
72 //===----------------------------------------------------------------------===//
73 // ELFWriter Implementation
74 //===----------------------------------------------------------------------===//
76 ELFWriter::ELFWriter(raw_ostream &o, TargetMachine &tm)
77 : MachineFunctionPass(&ID), O(o), TM(tm),
78 OutContext(*new MCContext()),
79 TLOF(TM.getTargetLowering()->getObjFileLowering()),
80 is64Bit(TM.getTargetData()->getPointerSizeInBits() == 64),
81 isLittleEndian(TM.getTargetData()->isLittleEndian()),
82 ElfHdr(isLittleEndian, is64Bit) {
84 TAI = TM.getTargetAsmInfo();
85 TEW = TM.getELFWriterInfo();
87 // Create the object code emitter object for this target.
88 ElfCE = new ELFCodeEmitter(*this);
90 // Inital number of sections
94 ELFWriter::~ELFWriter() {
99 // doInitialization - Emit the file header and all of the global variables for
100 // the module to the ELF file.
101 bool ELFWriter::doInitialization(Module &M) {
102 // Initialize TargetLoweringObjectFile.
103 const_cast<TargetLoweringObjectFile&>(TLOF).Initialize(OutContext, TM);
105 Mang = new Mangler(M);
109 // Fields e_shnum e_shstrndx are only known after all section have
110 // been emitted. They locations in the ouput buffer are recorded so
111 // to be patched up later.
115 // emitWord method behaves differently for ELF32 and ELF64, writing
116 // 4 bytes in the former and 8 in the last for *_off and *_addr elf types
118 ElfHdr.emitByte(0x7f); // e_ident[EI_MAG0]
119 ElfHdr.emitByte('E'); // e_ident[EI_MAG1]
120 ElfHdr.emitByte('L'); // e_ident[EI_MAG2]
121 ElfHdr.emitByte('F'); // e_ident[EI_MAG3]
123 ElfHdr.emitByte(TEW->getEIClass()); // e_ident[EI_CLASS]
124 ElfHdr.emitByte(TEW->getEIData()); // e_ident[EI_DATA]
125 ElfHdr.emitByte(EV_CURRENT); // e_ident[EI_VERSION]
126 ElfHdr.emitAlignment(16); // e_ident[EI_NIDENT-EI_PAD]
128 ElfHdr.emitWord16(ET_REL); // e_type
129 ElfHdr.emitWord16(TEW->getEMachine()); // e_machine = target
130 ElfHdr.emitWord32(EV_CURRENT); // e_version
131 ElfHdr.emitWord(0); // e_entry, no entry point in .o file
132 ElfHdr.emitWord(0); // e_phoff, no program header for .o
133 ELFHdr_e_shoff_Offset = ElfHdr.size();
134 ElfHdr.emitWord(0); // e_shoff = sec hdr table off in bytes
135 ElfHdr.emitWord32(TEW->getEFlags()); // e_flags = whatever the target wants
136 ElfHdr.emitWord16(TEW->getHdrSize()); // e_ehsize = ELF header size
137 ElfHdr.emitWord16(0); // e_phentsize = prog header entry size
138 ElfHdr.emitWord16(0); // e_phnum = # prog header entries = 0
140 // e_shentsize = Section header entry size
141 ElfHdr.emitWord16(TEW->getSHdrSize());
143 // e_shnum = # of section header ents
144 ELFHdr_e_shnum_Offset = ElfHdr.size();
145 ElfHdr.emitWord16(0); // Placeholder
147 // e_shstrndx = Section # of '.shstrtab'
148 ELFHdr_e_shstrndx_Offset = ElfHdr.size();
149 ElfHdr.emitWord16(0); // Placeholder
151 // Add the null section, which is required to be first in the file.
154 // The first entry in the symtab is the null symbol and the second
155 // is a local symbol containing the module/file name
156 SymbolList.push_back(new ELFSym());
157 SymbolList.push_back(ELFSym::getFileSym());
162 // addGlobalSymbol - Add a global to be processed and to the global symbol
163 // lookup, use a zero index because the table index will be determined later.
164 void ELFWriter::addGlobalSymbol(const GlobalValue *GV,
165 bool AddToLookup /* = false */) {
166 PendingGlobals.insert(GV);
168 GblSymLookup[GV] = 0;
171 // addExternalSymbol - Add the external to be processed and to the
172 // external symbol lookup, use a zero index because the symbol
173 // table index will be determined later
174 void ELFWriter::addExternalSymbol(const char *External) {
175 PendingExternals.insert(External);
176 ExtSymLookup[External] = 0;
179 // getCtorSection - Get the static constructor section
180 ELFSection &ELFWriter::getCtorSection() {
181 const MCSectionELF *Ctor = (const MCSectionELF *)TLOF.getStaticCtorSection();
182 return getSection(Ctor->getSectionName(), ELFSection::SHT_PROGBITS,
183 getElfSectionFlags(Ctor->getKind()));
186 // getDtorSection - Get the static destructor section
187 ELFSection &ELFWriter::getDtorSection() {
188 const MCSectionELF *Dtor = (const MCSectionELF *)TLOF.getStaticDtorSection();
189 return getSection(Dtor->getSectionName(), ELFSection::SHT_PROGBITS,
190 getElfSectionFlags(Dtor->getKind()));
193 // getTextSection - Get the text section for the specified function
194 ELFSection &ELFWriter::getTextSection(Function *F) {
195 const MCSectionELF *Text =
196 (const MCSectionELF *)TLOF.SectionForGlobal(F, Mang, TM);
197 return getSection(Text->getSectionName(), ELFSection::SHT_PROGBITS,
198 getElfSectionFlags(Text->getKind()));
201 // getJumpTableSection - Get a read only section for constants when
202 // emitting jump tables. TODO: add PIC support
203 ELFSection &ELFWriter::getJumpTableSection() {
204 const MCSectionELF *JT =
205 (const MCSectionELF *)TLOF.getSectionForConstant(SectionKind::getReadOnly());
206 return getSection(JT->getSectionName(),
207 ELFSection::SHT_PROGBITS,
208 getElfSectionFlags(JT->getKind()),
209 TM.getTargetData()->getPointerABIAlignment());
212 // getConstantPoolSection - Get a constant pool section based on the machine
213 // constant pool entry type and relocation info.
214 ELFSection &ELFWriter::getConstantPoolSection(MachineConstantPoolEntry &CPE) {
216 switch (CPE.getRelocationInfo()) {
217 default: llvm_unreachable("Unknown section kind");
218 case 2: Kind = SectionKind::getReadOnlyWithRel(); break;
220 Kind = SectionKind::getReadOnlyWithRelLocal();
223 switch (TM.getTargetData()->getTypeAllocSize(CPE.getType())) {
224 case 4: Kind = SectionKind::getMergeableConst4(); break;
225 case 8: Kind = SectionKind::getMergeableConst8(); break;
226 case 16: Kind = SectionKind::getMergeableConst16(); break;
227 default: Kind = SectionKind::getMergeableConst(); break;
231 const MCSectionELF *CPSect =
232 (const MCSectionELF *)TLOF.getSectionForConstant(Kind);
233 return getSection(CPSect->getSectionName(),
234 ELFSection::SHT_PROGBITS,
235 getElfSectionFlags(Kind),
239 // getRelocSection - Return the relocation section of section 'S'. 'RelA'
240 // is true if the relocation section contains entries with addends.
241 ELFSection &ELFWriter::getRelocSection(ELFSection &S) {
242 unsigned SectionHeaderTy = TEW->hasRelocationAddend() ?
243 ELFSection::SHT_RELA : ELFSection::SHT_REL;
244 std::string RelSName(".rel");
245 if (TEW->hasRelocationAddend())
246 RelSName.append("a");
247 RelSName.append(S.getName());
249 return getSection(RelSName, SectionHeaderTy, 0, TEW->getPrefELFAlignment());
252 // getGlobalELFVisibility - Returns the ELF specific visibility type
253 unsigned ELFWriter::getGlobalELFVisibility(const GlobalValue *GV) {
254 switch (GV->getVisibility()) {
256 llvm_unreachable("unknown visibility type");
257 case GlobalValue::DefaultVisibility:
258 return ELFSym::STV_DEFAULT;
259 case GlobalValue::HiddenVisibility:
260 return ELFSym::STV_HIDDEN;
261 case GlobalValue::ProtectedVisibility:
262 return ELFSym::STV_PROTECTED;
267 // getGlobalELFBinding - Returns the ELF specific binding type
268 unsigned ELFWriter::getGlobalELFBinding(const GlobalValue *GV) {
269 if (GV->hasInternalLinkage())
270 return ELFSym::STB_LOCAL;
272 if (GV->isWeakForLinker() && !GV->hasCommonLinkage())
273 return ELFSym::STB_WEAK;
275 return ELFSym::STB_GLOBAL;
278 // getGlobalELFType - Returns the ELF specific type for a global
279 unsigned ELFWriter::getGlobalELFType(const GlobalValue *GV) {
280 if (GV->isDeclaration())
281 return ELFSym::STT_NOTYPE;
283 if (isa<Function>(GV))
284 return ELFSym::STT_FUNC;
286 return ELFSym::STT_OBJECT;
289 // getElfSectionFlags - Get the ELF Section Header flags based
290 // on the flags defined in SectionKind.h.
291 unsigned ELFWriter::getElfSectionFlags(SectionKind Kind, bool IsAlloc) {
292 unsigned ElfSectionFlags = 0;
295 ElfSectionFlags |= ELFSection::SHF_ALLOC;
297 ElfSectionFlags |= ELFSection::SHF_EXECINSTR;
298 if (Kind.isWriteable())
299 ElfSectionFlags |= ELFSection::SHF_WRITE;
300 if (Kind.isMergeableConst() || Kind.isMergeableCString())
301 ElfSectionFlags |= ELFSection::SHF_MERGE;
302 if (Kind.isThreadLocal())
303 ElfSectionFlags |= ELFSection::SHF_TLS;
304 if (Kind.isMergeableCString())
305 ElfSectionFlags |= ELFSection::SHF_STRINGS;
307 return ElfSectionFlags;
310 // isUndefOrNull - The constant is either a null initialized value or an
312 static bool isUndefOrNull(const Constant *CV) {
313 return (CV->isNullValue() || isa<UndefValue>(CV));
316 // isELFUndefSym - the symbol has no section and must be placed in
317 // the symbol table with a reference to the null section.
318 static bool isELFUndefSym(const GlobalValue *GV) {
319 // Functions which make up until this point references are an undef symbol
320 return GV->isDeclaration() || (isa<Function>(GV));
323 // isELFBssSym - for an undef or null value, the symbol must go to a bss
324 // section if it's not weak for linker, otherwise it's a common sym.
325 static bool isELFBssSym(const GlobalVariable *GV, SectionKind Kind) {
326 const Constant *CV = GV->getInitializer();
328 return (!Kind.isMergeableCString() &&
330 !GV->isWeakForLinker());
333 // isELFCommonSym - for an undef or null value, the symbol must go to a
334 // common section if it's weak for linker, otherwise bss.
335 static bool isELFCommonSym(const GlobalVariable *GV) {
336 return (isUndefOrNull(GV->getInitializer()) && GV->isWeakForLinker());
339 // EmitGlobal - Choose the right section for global and emit it
340 void ELFWriter::EmitGlobal(const GlobalValue *GV) {
342 // Check if the referenced symbol is already emitted
343 if (GblSymLookup.find(GV) != GblSymLookup.end())
346 // Handle ELF Bind, Visibility and Type for the current symbol
347 unsigned SymBind = getGlobalELFBinding(GV);
348 unsigned SymType = getGlobalELFType(GV);
350 // All undef symbols have the same binding, type and visibily and
351 // are classified regardless of their type.
352 ELFSym *GblSym = isELFUndefSym(GV) ? ELFSym::getUndefGV(GV, SymBind)
353 : ELFSym::getGV(GV, SymBind, SymType, getGlobalELFVisibility(GV));
355 if (!isELFUndefSym(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);
366 SectionKind Kind = S->getKind();
367 unsigned SectionFlags = getElfSectionFlags(Kind);
369 // The symbol align should update the section alignment if needed
370 const TargetData *TD = TM.getTargetData();
371 unsigned Align = TD->getPreferredAlignment(GVar);
372 unsigned Size = TD->getTypeAllocSize(GVar->getInitializer()->getType());
375 if (isELFCommonSym(GVar)) {
376 GblSym->SectionIdx = ELFSection::SHN_COMMON;
377 getSection(S->getSectionName(),
378 ELFSection::SHT_NOBITS, SectionFlags, 1);
380 // A new linkonce section is created for each global in the
381 // common section, the default alignment is 1 and the symbol
382 // value contains its alignment.
383 GblSym->Value = Align;
385 } else if (isELFBssSym(GVar, Kind)) {
387 getSection(S->getSectionName(), ELFSection::SHT_NOBITS,
389 GblSym->SectionIdx = ES.SectionIdx;
391 // Update the size with alignment and the next object can
392 // start in the right offset in the section
393 if (Align) ES.Size = (ES.Size + Align-1) & ~(Align-1);
394 ES.Align = std::max(ES.Align, Align);
396 // GblSym->Value should contain the virtual offset inside the section.
397 // Virtual because the BSS space is not allocated on ELF objects
398 GblSym->Value = ES.Size;
401 } else { // The symbol must go to some kind of data section
403 getSection(S->getSectionName(), ELFSection::SHT_PROGBITS,
405 GblSym->SectionIdx = ES.SectionIdx;
407 // GblSym->Value should contain the symbol offset inside the section,
408 // and all symbols should start on their required alignment boundary
409 ES.Align = std::max(ES.Align, Align);
410 ES.emitAlignment(Align);
411 GblSym->Value = ES.size();
413 // Emit the global to the data section 'ES'
414 EmitGlobalConstant(GVar->getInitializer(), ES);
418 if (GV->hasPrivateLinkage()) {
419 // For a private symbols, keep track of the index inside the
420 // private list since it will never go to the symbol table and
421 // won't be patched up later.
422 PrivateSyms.push_back(GblSym);
423 GblSymLookup[GV] = PrivateSyms.size()-1;
425 // Non private symbol are left with zero indices until they are patched
426 // up during the symbol table emition (where the indicies are created).
427 SymbolList.push_back(GblSym);
428 GblSymLookup[GV] = 0;
432 void ELFWriter::EmitGlobalConstantStruct(const ConstantStruct *CVS,
435 // Print the fields in successive locations. Pad to align if needed!
436 const TargetData *TD = TM.getTargetData();
437 unsigned Size = TD->getTypeAllocSize(CVS->getType());
438 const StructLayout *cvsLayout = TD->getStructLayout(CVS->getType());
439 uint64_t sizeSoFar = 0;
440 for (unsigned i = 0, e = CVS->getNumOperands(); i != e; ++i) {
441 const Constant* field = CVS->getOperand(i);
443 // Check if padding is needed and insert one or more 0s.
444 uint64_t fieldSize = TD->getTypeAllocSize(field->getType());
445 uint64_t padSize = ((i == e-1 ? Size : cvsLayout->getElementOffset(i+1))
446 - cvsLayout->getElementOffset(i)) - fieldSize;
447 sizeSoFar += fieldSize + padSize;
449 // Now print the actual field value.
450 EmitGlobalConstant(field, GblS);
452 // Insert padding - this may include padding to increase the size of the
453 // current field up to the ABI size (if the struct is not packed) as well
454 // as padding to ensure that the next field starts at the right offset.
455 GblS.emitZeros(padSize);
457 assert(sizeSoFar == cvsLayout->getSizeInBytes() &&
458 "Layout of constant struct may be incorrect!");
461 void ELFWriter::EmitGlobalConstant(const Constant *CV, ELFSection &GblS) {
462 const TargetData *TD = TM.getTargetData();
463 unsigned Size = TD->getTypeAllocSize(CV->getType());
465 if (const ConstantArray *CVA = dyn_cast<ConstantArray>(CV)) {
466 for (unsigned i = 0, e = CVA->getNumOperands(); i != e; ++i)
467 EmitGlobalConstant(CVA->getOperand(i), GblS);
469 } else if (isa<ConstantAggregateZero>(CV)) {
470 GblS.emitZeros(Size);
472 } else if (const ConstantStruct *CVS = dyn_cast<ConstantStruct>(CV)) {
473 EmitGlobalConstantStruct(CVS, GblS);
475 } else if (const ConstantFP *CFP = dyn_cast<ConstantFP>(CV)) {
476 APInt Val = CFP->getValueAPF().bitcastToAPInt();
477 if (CFP->getType() == Type::DoubleTy)
478 GblS.emitWord64(Val.getZExtValue());
479 else if (CFP->getType() == Type::FloatTy)
480 GblS.emitWord32(Val.getZExtValue());
481 else if (CFP->getType() == Type::X86_FP80Ty) {
482 unsigned PadSize = TD->getTypeAllocSize(Type::X86_FP80Ty)-
483 TD->getTypeStoreSize(Type::X86_FP80Ty);
484 GblS.emitWordFP80(Val.getRawData(), PadSize);
485 } else if (CFP->getType() == Type::PPC_FP128Ty)
486 llvm_unreachable("PPC_FP128Ty global emission not implemented");
488 } else if (const ConstantInt *CI = dyn_cast<ConstantInt>(CV)) {
490 GblS.emitByte(CI->getZExtValue());
492 GblS.emitWord16(CI->getZExtValue());
494 GblS.emitWord32(CI->getZExtValue());
496 EmitGlobalConstantLargeInt(CI, GblS);
498 } else if (const ConstantVector *CP = dyn_cast<ConstantVector>(CV)) {
499 const VectorType *PTy = CP->getType();
500 for (unsigned I = 0, E = PTy->getNumElements(); I < E; ++I)
501 EmitGlobalConstant(CP->getOperand(I), GblS);
503 } else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(CV)) {
504 // Resolve a constant expression which returns a (Constant, Offset)
505 // pair. If 'Res.first' is a GlobalValue, emit a relocation with
506 // the offset 'Res.second', otherwise emit a global constant like
507 // it is always done for not contant expression types.
508 CstExprResTy Res = ResolveConstantExpr(CE);
509 const Constant *Op = Res.first;
511 if (isa<GlobalValue>(Op))
512 EmitGlobalDataRelocation(cast<const GlobalValue>(Op),
513 TD->getTypeAllocSize(Op->getType()),
516 EmitGlobalConstant(Op, GblS);
519 } else if (CV->getType()->getTypeID() == Type::PointerTyID) {
520 // Fill the data entry with zeros or emit a relocation entry
521 if (isa<ConstantPointerNull>(CV))
522 GblS.emitZeros(Size);
524 EmitGlobalDataRelocation(cast<const GlobalValue>(CV),
527 } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(CV)) {
528 // This is a constant address for a global variable or function and
529 // therefore must be referenced using a relocation entry.
530 EmitGlobalDataRelocation(GV, Size, GblS);
535 raw_string_ostream ErrorMsg(msg);
536 ErrorMsg << "Constant unimp for type: " << *CV->getType();
537 llvm_report_error(ErrorMsg.str());
540 // ResolveConstantExpr - Resolve the constant expression until it stop
541 // yielding other constant expressions.
542 CstExprResTy ELFWriter::ResolveConstantExpr(const Constant *CV) {
543 const TargetData *TD = TM.getTargetData();
545 // There ins't constant expression inside others anymore
546 if (!isa<ConstantExpr>(CV))
547 return std::make_pair(CV, 0);
549 const ConstantExpr *CE = dyn_cast<ConstantExpr>(CV);
550 switch (CE->getOpcode()) {
551 case Instruction::BitCast:
552 return ResolveConstantExpr(CE->getOperand(0));
554 case Instruction::GetElementPtr: {
555 const Constant *ptrVal = CE->getOperand(0);
556 SmallVector<Value*, 8> idxVec(CE->op_begin()+1, CE->op_end());
557 int64_t Offset = TD->getIndexedOffset(ptrVal->getType(), &idxVec[0],
559 return std::make_pair(ptrVal, Offset);
561 case Instruction::IntToPtr: {
562 Constant *Op = CE->getOperand(0);
563 Op = ConstantExpr::getIntegerCast(Op, TD->getIntPtrType(), false/*ZExt*/);
564 return ResolveConstantExpr(Op);
566 case Instruction::PtrToInt: {
567 Constant *Op = CE->getOperand(0);
568 const Type *Ty = CE->getType();
570 // We can emit the pointer value into this slot if the slot is an
571 // integer slot greater or equal to the size of the pointer.
572 if (TD->getTypeAllocSize(Ty) == TD->getTypeAllocSize(Op->getType()))
573 return ResolveConstantExpr(Op);
575 llvm_unreachable("Integer size less then pointer size");
577 case Instruction::Add:
578 case Instruction::Sub: {
579 // Only handle cases where there's a constant expression with GlobalValue
580 // as first operand and ConstantInt as second, which are the cases we can
581 // solve direclty using a relocation entry. GlobalValue=Op0, CstInt=Op1
582 // 1) Instruction::Add => (global) + CstInt
583 // 2) Instruction::Sub => (global) + -CstInt
584 const Constant *Op0 = CE->getOperand(0);
585 const Constant *Op1 = CE->getOperand(1);
586 assert(isa<ConstantInt>(Op1) && "Op1 must be a ConstantInt");
588 CstExprResTy Res = ResolveConstantExpr(Op0);
589 assert(isa<GlobalValue>(Res.first) && "Op0 must be a GlobalValue");
591 const APInt &RHS = cast<ConstantInt>(Op1)->getValue();
592 switch (CE->getOpcode()) {
593 case Instruction::Add:
594 return std::make_pair(Res.first, RHS.getSExtValue());
595 case Instruction::Sub:
596 return std::make_pair(Res.first, (-RHS).getSExtValue());
601 std::string msg(CE->getOpcodeName());
602 raw_string_ostream ErrorMsg(msg);
603 ErrorMsg << ": Unsupported ConstantExpr type";
604 llvm_report_error(ErrorMsg.str());
606 return std::make_pair(CV, 0); // silence warning
609 void ELFWriter::EmitGlobalDataRelocation(const GlobalValue *GV, unsigned Size,
610 ELFSection &GblS, int64_t Offset) {
611 // Create the relocation entry for the global value
612 MachineRelocation MR =
613 MachineRelocation::getGV(GblS.getCurrentPCOffset(),
614 TEW->getAbsoluteLabelMachineRelTy(),
615 const_cast<GlobalValue*>(GV),
618 // Fill the data entry with zeros
619 GblS.emitZeros(Size);
621 // Add the relocation entry for the current data section
622 GblS.addRelocation(MR);
625 void ELFWriter::EmitGlobalConstantLargeInt(const ConstantInt *CI,
627 const TargetData *TD = TM.getTargetData();
628 unsigned BitWidth = CI->getBitWidth();
629 assert(isPowerOf2_32(BitWidth) &&
630 "Non-power-of-2-sized integers not handled!");
632 const uint64_t *RawData = CI->getValue().getRawData();
634 for (unsigned i = 0, e = BitWidth / 64; i != e; ++i) {
635 Val = (TD->isBigEndian()) ? RawData[e - i - 1] : RawData[i];
640 /// EmitSpecialLLVMGlobal - Check to see if the specified global is a
641 /// special global used by LLVM. If so, emit it and return true, otherwise
642 /// do nothing and return false.
643 bool ELFWriter::EmitSpecialLLVMGlobal(const GlobalVariable *GV) {
644 if (GV->getName() == "llvm.used")
645 llvm_unreachable("not implemented yet");
647 // Ignore debug and non-emitted data. This handles llvm.compiler.used.
648 if (GV->getSection() == "llvm.metadata" ||
649 GV->hasAvailableExternallyLinkage())
652 if (!GV->hasAppendingLinkage()) return false;
654 assert(GV->hasInitializer() && "Not a special LLVM global!");
656 const TargetData *TD = TM.getTargetData();
657 unsigned Align = TD->getPointerPrefAlignment();
658 if (GV->getName() == "llvm.global_ctors") {
659 ELFSection &Ctor = getCtorSection();
660 Ctor.emitAlignment(Align);
661 EmitXXStructorList(GV->getInitializer(), Ctor);
665 if (GV->getName() == "llvm.global_dtors") {
666 ELFSection &Dtor = getDtorSection();
667 Dtor.emitAlignment(Align);
668 EmitXXStructorList(GV->getInitializer(), Dtor);
675 /// EmitXXStructorList - Emit the ctor or dtor list. This just emits out the
676 /// function pointers, ignoring the init priority.
677 void ELFWriter::EmitXXStructorList(Constant *List, ELFSection &Xtor) {
678 // Should be an array of '{ int, void ()* }' structs. The first value is the
679 // init priority, which we ignore.
680 if (!isa<ConstantArray>(List)) return;
681 ConstantArray *InitList = cast<ConstantArray>(List);
682 for (unsigned i = 0, e = InitList->getNumOperands(); i != e; ++i)
683 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(InitList->getOperand(i))){
684 if (CS->getNumOperands() != 2) return; // Not array of 2-element structs.
686 if (CS->getOperand(1)->isNullValue())
687 return; // Found a null terminator, exit printing.
688 // Emit the function pointer.
689 EmitGlobalConstant(CS->getOperand(1), Xtor);
693 bool ELFWriter::runOnMachineFunction(MachineFunction &MF) {
694 // Nothing to do here, this is all done through the ElfCE object above.
698 /// doFinalization - Now that the module has been completely processed, emit
699 /// the ELF file to 'O'.
700 bool ELFWriter::doFinalization(Module &M) {
701 // Emit .data section placeholder
704 // Emit .bss section placeholder
707 // Build and emit data, bss and "common" sections.
708 for (Module::global_iterator I = M.global_begin(), E = M.global_end();
712 // Emit all pending globals
713 for (PendingGblsIter I = PendingGlobals.begin(), E = PendingGlobals.end();
717 // Emit all pending externals
718 for (PendingExtsIter I = PendingExternals.begin(), E = PendingExternals.end();
720 SymbolList.push_back(ELFSym::getExtSym(*I));
722 // Emit non-executable stack note
723 if (TAI->getNonexecutableStackDirective())
724 getNonExecStackSection();
726 // Emit a symbol for each section created until now, skip null section
727 for (unsigned i = 1, e = SectionList.size(); i < e; ++i) {
728 ELFSection &ES = *SectionList[i];
729 ELFSym *SectionSym = ELFSym::getSectionSym();
730 SectionSym->SectionIdx = ES.SectionIdx;
731 SymbolList.push_back(SectionSym);
732 ES.Sym = SymbolList.back();
736 EmitStringTable(M.getModuleIdentifier());
738 // Emit the symbol table now, if non-empty.
741 // Emit the relocation sections.
744 // Emit the sections string table.
745 EmitSectionTableStringTable();
747 // Dump the sections and section table to the .o file.
748 OutputSectionsAndSectionTable();
750 // We are done with the abstract symbols.
755 // Release the name mangler object.
756 delete Mang; Mang = 0;
760 // RelocateField - Patch relocatable field with 'Offset' in 'BO'
761 // using a 'Value' of known 'Size'
762 void ELFWriter::RelocateField(BinaryObject &BO, uint32_t Offset,
763 int64_t Value, unsigned Size) {
765 BO.fixWord32(Value, Offset);
767 BO.fixWord64(Value, Offset);
769 llvm_unreachable("don't know howto patch relocatable field");
772 /// EmitRelocations - Emit relocations
773 void ELFWriter::EmitRelocations() {
775 // True if the target uses the relocation entry to hold the addend,
776 // otherwise the addend is written directly to the relocatable field.
777 bool HasRelA = TEW->hasRelocationAddend();
779 // Create Relocation sections for each section which needs it.
780 for (unsigned i=0, e=SectionList.size(); i != e; ++i) {
781 ELFSection &S = *SectionList[i];
783 // This section does not have relocations
784 if (!S.hasRelocations()) continue;
785 ELFSection &RelSec = getRelocSection(S);
787 // 'Link' - Section hdr idx of the associated symbol table
788 // 'Info' - Section hdr idx of the section to which the relocation applies
789 ELFSection &SymTab = getSymbolTableSection();
790 RelSec.Link = SymTab.SectionIdx;
791 RelSec.Info = S.SectionIdx;
792 RelSec.EntSize = TEW->getRelocationEntrySize();
794 // Get the relocations from Section
795 std::vector<MachineRelocation> Relos = S.getRelocations();
796 for (std::vector<MachineRelocation>::iterator MRI = Relos.begin(),
797 MRE = Relos.end(); MRI != MRE; ++MRI) {
798 MachineRelocation &MR = *MRI;
800 // Relocatable field offset from the section start
801 unsigned RelOffset = MR.getMachineCodeOffset();
803 // Symbol index in the symbol table
806 // Target specific relocation field type and size
807 unsigned RelType = TEW->getRelocationType(MR.getRelocationType());
808 unsigned RelTySize = TEW->getRelocationTySize(RelType);
811 // There are several machine relocations types, and each one of
812 // them needs a different approach to retrieve the symbol table index.
813 if (MR.isGlobalValue()) {
814 const GlobalValue *G = MR.getGlobalValue();
815 int64_t GlobalOffset = MR.getConstantVal();
816 SymIdx = GblSymLookup[G];
817 if (G->hasPrivateLinkage()) {
818 // If the target uses a section offset in the relocation:
819 // SymIdx + Addend = section sym for global + section offset
820 unsigned SectionIdx = PrivateSyms[SymIdx]->SectionIdx;
821 Addend = PrivateSyms[SymIdx]->Value + GlobalOffset;
822 SymIdx = SectionList[SectionIdx]->getSymbolTableIndex();
824 Addend = TEW->getDefaultAddendForRelTy(RelType, GlobalOffset);
826 } else if (MR.isExternalSymbol()) {
827 const char *ExtSym = MR.getExternalSymbol();
828 SymIdx = ExtSymLookup[ExtSym];
829 Addend = TEW->getDefaultAddendForRelTy(RelType);
831 // Get the symbol index for the section symbol
832 unsigned SectionIdx = MR.getConstantVal();
833 SymIdx = SectionList[SectionIdx]->getSymbolTableIndex();
835 // The symbol offset inside the section
836 int64_t SymOffset = (int64_t)MR.getResultPointer();
838 // For pc relative relocations where symbols are defined in the same
839 // section they are referenced, ignore the relocation entry and patch
840 // the relocatable field with the symbol offset directly.
841 if (S.SectionIdx == SectionIdx && TEW->isPCRelativeRel(RelType)) {
842 int64_t Value = TEW->computeRelocation(SymOffset, RelOffset, RelType);
843 RelocateField(S, RelOffset, Value, RelTySize);
847 Addend = TEW->getDefaultAddendForRelTy(RelType, SymOffset);
850 // The target without addend on the relocation symbol must be
851 // patched in the relocation place itself to contain the addend
852 // otherwise write zeros to make sure there is no garbage there
853 RelocateField(S, RelOffset, HasRelA ? 0 : Addend, RelTySize);
855 // Get the relocation entry and emit to the relocation section
856 ELFRelocation Rel(RelOffset, SymIdx, RelType, HasRelA, Addend);
857 EmitRelocation(RelSec, Rel, HasRelA);
862 /// EmitRelocation - Write relocation 'Rel' to the relocation section 'Rel'
863 void ELFWriter::EmitRelocation(BinaryObject &RelSec, ELFRelocation &Rel,
865 RelSec.emitWord(Rel.getOffset());
866 RelSec.emitWord(Rel.getInfo(is64Bit));
868 RelSec.emitWord(Rel.getAddend());
871 /// EmitSymbol - Write symbol 'Sym' to the symbol table 'SymbolTable'
872 void ELFWriter::EmitSymbol(BinaryObject &SymbolTable, ELFSym &Sym) {
874 SymbolTable.emitWord32(Sym.NameIdx);
875 SymbolTable.emitByte(Sym.Info);
876 SymbolTable.emitByte(Sym.Other);
877 SymbolTable.emitWord16(Sym.SectionIdx);
878 SymbolTable.emitWord64(Sym.Value);
879 SymbolTable.emitWord64(Sym.Size);
881 SymbolTable.emitWord32(Sym.NameIdx);
882 SymbolTable.emitWord32(Sym.Value);
883 SymbolTable.emitWord32(Sym.Size);
884 SymbolTable.emitByte(Sym.Info);
885 SymbolTable.emitByte(Sym.Other);
886 SymbolTable.emitWord16(Sym.SectionIdx);
890 /// EmitSectionHeader - Write section 'Section' header in 'SHdrTab'
891 /// Section Header Table
892 void ELFWriter::EmitSectionHeader(BinaryObject &SHdrTab,
893 const ELFSection &SHdr) {
894 SHdrTab.emitWord32(SHdr.NameIdx);
895 SHdrTab.emitWord32(SHdr.Type);
897 SHdrTab.emitWord64(SHdr.Flags);
898 SHdrTab.emitWord(SHdr.Addr);
899 SHdrTab.emitWord(SHdr.Offset);
900 SHdrTab.emitWord64(SHdr.Size);
901 SHdrTab.emitWord32(SHdr.Link);
902 SHdrTab.emitWord32(SHdr.Info);
903 SHdrTab.emitWord64(SHdr.Align);
904 SHdrTab.emitWord64(SHdr.EntSize);
906 SHdrTab.emitWord32(SHdr.Flags);
907 SHdrTab.emitWord(SHdr.Addr);
908 SHdrTab.emitWord(SHdr.Offset);
909 SHdrTab.emitWord32(SHdr.Size);
910 SHdrTab.emitWord32(SHdr.Link);
911 SHdrTab.emitWord32(SHdr.Info);
912 SHdrTab.emitWord32(SHdr.Align);
913 SHdrTab.emitWord32(SHdr.EntSize);
917 /// EmitStringTable - If the current symbol table is non-empty, emit the string
919 void ELFWriter::EmitStringTable(const std::string &ModuleName) {
920 if (!SymbolList.size()) return; // Empty symbol table.
921 ELFSection &StrTab = getStringTableSection();
923 // Set the zero'th symbol to a null byte, as required.
926 // Walk on the symbol list and write symbol names into the string table.
928 for (ELFSymIter I=SymbolList.begin(), E=SymbolList.end(); I != E; ++I) {
932 if (Sym.isGlobalValue())
933 Name.append(Mang->getMangledName(Sym.getGlobalValue()));
934 else if (Sym.isExternalSym())
935 Name.append(Sym.getExternalSymbol());
936 else if (Sym.isFileType())
937 Name.append(ModuleName);
943 StrTab.emitString(Name);
945 // Keep track of the number of bytes emitted to this section.
946 Index += Name.size()+1;
949 assert(Index == StrTab.size());
953 // SortSymbols - On the symbol table local symbols must come before
954 // all other symbols with non-local bindings. The return value is
955 // the position of the first non local symbol.
956 unsigned ELFWriter::SortSymbols() {
957 unsigned FirstNonLocalSymbol;
958 std::vector<ELFSym*> LocalSyms, OtherSyms;
960 for (ELFSymIter I=SymbolList.begin(), E=SymbolList.end(); I != E; ++I) {
961 if ((*I)->isLocalBind())
962 LocalSyms.push_back(*I);
964 OtherSyms.push_back(*I);
967 FirstNonLocalSymbol = LocalSyms.size();
969 for (unsigned i = 0; i < FirstNonLocalSymbol; ++i)
970 SymbolList.push_back(LocalSyms[i]);
972 for (ELFSymIter I=OtherSyms.begin(), E=OtherSyms.end(); I != E; ++I)
973 SymbolList.push_back(*I);
978 return FirstNonLocalSymbol;
981 /// EmitSymbolTable - Emit the symbol table itself.
982 void ELFWriter::EmitSymbolTable() {
983 if (!SymbolList.size()) return; // Empty symbol table.
985 // Now that we have emitted the string table and know the offset into the
986 // string table of each symbol, emit the symbol table itself.
987 ELFSection &SymTab = getSymbolTableSection();
988 SymTab.Align = TEW->getPrefELFAlignment();
990 // Section Index of .strtab.
991 SymTab.Link = getStringTableSection().SectionIdx;
993 // Size of each symtab entry.
994 SymTab.EntSize = TEW->getSymTabEntrySize();
996 // Reorder the symbol table with local symbols first!
997 unsigned FirstNonLocalSymbol = SortSymbols();
999 // Emit all the symbols to the symbol table.
1000 for (unsigned i = 0, e = SymbolList.size(); i < e; ++i) {
1001 ELFSym &Sym = *SymbolList[i];
1003 // Emit symbol to the symbol table
1004 EmitSymbol(SymTab, Sym);
1006 // Record the symbol table index for each symbol
1007 if (Sym.isGlobalValue())
1008 GblSymLookup[Sym.getGlobalValue()] = i;
1009 else if (Sym.isExternalSym())
1010 ExtSymLookup[Sym.getExternalSymbol()] = i;
1012 // Keep track on the symbol index into the symbol table
1016 // One greater than the symbol table index of the last local symbol
1017 SymTab.Info = FirstNonLocalSymbol;
1018 SymTab.Size = SymTab.size();
1021 /// EmitSectionTableStringTable - This method adds and emits a section for the
1022 /// ELF Section Table string table: the string table that holds all of the
1024 void ELFWriter::EmitSectionTableStringTable() {
1025 // First step: add the section for the string table to the list of sections:
1026 ELFSection &SHStrTab = getSectionHeaderStringTableSection();
1028 // Now that we know which section number is the .shstrtab section, update the
1029 // e_shstrndx entry in the ELF header.
1030 ElfHdr.fixWord16(SHStrTab.SectionIdx, ELFHdr_e_shstrndx_Offset);
1032 // Set the NameIdx of each section in the string table and emit the bytes for
1033 // the string table.
1036 for (ELFSectionIter I=SectionList.begin(), E=SectionList.end(); I != E; ++I) {
1037 ELFSection &S = *(*I);
1038 // Set the index into the table. Note if we have lots of entries with
1039 // common suffixes, we could memoize them here if we cared.
1041 SHStrTab.emitString(S.getName());
1043 // Keep track of the number of bytes emitted to this section.
1044 Index += S.getName().size()+1;
1047 // Set the size of .shstrtab now that we know what it is.
1048 assert(Index == SHStrTab.size());
1049 SHStrTab.Size = Index;
1052 /// OutputSectionsAndSectionTable - Now that we have constructed the file header
1053 /// and all of the sections, emit these to the ostream destination and emit the
1055 void ELFWriter::OutputSectionsAndSectionTable() {
1056 // Pass #1: Compute the file offset for each section.
1057 size_t FileOff = ElfHdr.size(); // File header first.
1059 // Adjust alignment of all section if needed, skip the null section.
1060 for (unsigned i=1, e=SectionList.size(); i < e; ++i) {
1061 ELFSection &ES = *SectionList[i];
1063 ES.Offset = FileOff;
1067 // Update Section size
1069 ES.Size = ES.size();
1071 // Align FileOff to whatever the alignment restrictions of the section are.
1073 FileOff = (FileOff+ES.Align-1) & ~(ES.Align-1);
1075 ES.Offset = FileOff;
1079 // Align Section Header.
1080 unsigned TableAlign = TEW->getPrefELFAlignment();
1081 FileOff = (FileOff+TableAlign-1) & ~(TableAlign-1);
1083 // Now that we know where all of the sections will be emitted, set the e_shnum
1084 // entry in the ELF header.
1085 ElfHdr.fixWord16(NumSections, ELFHdr_e_shnum_Offset);
1087 // Now that we know the offset in the file of the section table, update the
1088 // e_shoff address in the ELF header.
1089 ElfHdr.fixWord(FileOff, ELFHdr_e_shoff_Offset);
1091 // Now that we know all of the data in the file header, emit it and all of the
1093 O.write((char *)&ElfHdr.getData()[0], ElfHdr.size());
1094 FileOff = ElfHdr.size();
1096 // Section Header Table blob
1097 BinaryObject SHdrTable(isLittleEndian, is64Bit);
1099 // Emit all of sections to the file and build the section header table.
1100 for (ELFSectionIter I=SectionList.begin(), E=SectionList.end(); I != E; ++I) {
1101 ELFSection &S = *(*I);
1102 DOUT << "SectionIdx: " << S.SectionIdx << ", Name: " << S.getName()
1103 << ", Size: " << S.Size << ", Offset: " << S.Offset
1104 << ", SectionData Size: " << S.size() << "\n";
1106 // Align FileOff to whatever the alignment restrictions of the section are.
1109 for (size_t NewFileOff = (FileOff+S.Align-1) & ~(S.Align-1);
1110 FileOff != NewFileOff; ++FileOff)
1113 O.write((char *)&S.getData()[0], S.Size);
1117 EmitSectionHeader(SHdrTable, S);
1120 // Align output for the section table.
1121 for (size_t NewFileOff = (FileOff+TableAlign-1) & ~(TableAlign-1);
1122 FileOff != NewFileOff; ++FileOff)
1125 // Emit the section table itself.
1126 O.write((char *)&SHdrTable.getData()[0], SHdrTable.size());