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/MCSection.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 MCSection *Ctor = TLOF.getStaticCtorSection();
182 return getSection(((MCSectionELF*)Ctor)->getName(), ELFSection::SHT_PROGBITS,
183 getElfSectionFlags(Ctor->getKind()));
186 // getDtorSection - Get the static destructor section
187 ELFSection &ELFWriter::getDtorSection() {
188 const MCSection *Dtor = TLOF.getStaticDtorSection();
189 return getSection(((MCSectionELF*)Dtor)->getName(), 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 MCSection *Text = TLOF.SectionForGlobal(F, Mang, TM);
196 return getSection(((MCSectionELF*)Text)->getName(), ELFSection::SHT_PROGBITS,
197 getElfSectionFlags(Text->getKind()));
200 // getJumpTableSection - Get a read only section for constants when
201 // emitting jump tables. TODO: add PIC support
202 ELFSection &ELFWriter::getJumpTableSection() {
203 const MCSection *JT = TLOF.getSectionForConstant(SectionKind::getReadOnly());
204 return getSection(((MCSectionELF*)JT)->getName(),
205 ELFSection::SHT_PROGBITS,
206 getElfSectionFlags(JT->getKind()),
207 TM.getTargetData()->getPointerABIAlignment());
210 // getConstantPoolSection - Get a constant pool section based on the machine
211 // constant pool entry type and relocation info.
212 ELFSection &ELFWriter::getConstantPoolSection(MachineConstantPoolEntry &CPE) {
214 switch (CPE.getRelocationInfo()) {
215 default: llvm_unreachable("Unknown section kind");
216 case 2: Kind = SectionKind::getReadOnlyWithRel(); break;
218 Kind = SectionKind::getReadOnlyWithRelLocal();
221 switch (TM.getTargetData()->getTypeAllocSize(CPE.getType())) {
222 case 4: Kind = SectionKind::getMergeableConst4(); break;
223 case 8: Kind = SectionKind::getMergeableConst8(); break;
224 case 16: Kind = SectionKind::getMergeableConst16(); break;
225 default: Kind = SectionKind::getMergeableConst(); break;
229 const MCSection *CPSect = TLOF.getSectionForConstant(Kind);
230 return getSection(((MCSectionELF*)CPSect)->getName(),
231 ELFSection::SHT_PROGBITS,
232 getElfSectionFlags(Kind),
236 // getRelocSection - Return the relocation section of section 'S'. 'RelA'
237 // is true if the relocation section contains entries with addends.
238 ELFSection &ELFWriter::getRelocSection(ELFSection &S) {
239 unsigned SectionHeaderTy = TEW->hasRelocationAddend() ?
240 ELFSection::SHT_RELA : ELFSection::SHT_REL;
241 std::string RelSName(".rel");
242 if (TEW->hasRelocationAddend())
243 RelSName.append("a");
244 RelSName.append(S.getName());
246 return getSection(RelSName, SectionHeaderTy, 0, TEW->getPrefELFAlignment());
249 // getGlobalELFVisibility - Returns the ELF specific visibility type
250 unsigned ELFWriter::getGlobalELFVisibility(const GlobalValue *GV) {
251 switch (GV->getVisibility()) {
253 llvm_unreachable("unknown visibility type");
254 case GlobalValue::DefaultVisibility:
255 return ELFSym::STV_DEFAULT;
256 case GlobalValue::HiddenVisibility:
257 return ELFSym::STV_HIDDEN;
258 case GlobalValue::ProtectedVisibility:
259 return ELFSym::STV_PROTECTED;
264 // getGlobalELFBinding - Returns the ELF specific binding type
265 unsigned ELFWriter::getGlobalELFBinding(const GlobalValue *GV) {
266 if (GV->hasInternalLinkage())
267 return ELFSym::STB_LOCAL;
269 if (GV->isWeakForLinker() && !GV->hasCommonLinkage())
270 return ELFSym::STB_WEAK;
272 return ELFSym::STB_GLOBAL;
275 // getGlobalELFType - Returns the ELF specific type for a global
276 unsigned ELFWriter::getGlobalELFType(const GlobalValue *GV) {
277 if (GV->isDeclaration())
278 return ELFSym::STT_NOTYPE;
280 if (isa<Function>(GV))
281 return ELFSym::STT_FUNC;
283 return ELFSym::STT_OBJECT;
286 // getElfSectionFlags - Get the ELF Section Header flags based
287 // on the flags defined in SectionKind.h.
288 unsigned ELFWriter::getElfSectionFlags(SectionKind Kind, bool IsAlloc) {
289 unsigned ElfSectionFlags = 0;
292 ElfSectionFlags |= ELFSection::SHF_ALLOC;
294 ElfSectionFlags |= ELFSection::SHF_EXECINSTR;
295 if (Kind.isWriteable())
296 ElfSectionFlags |= ELFSection::SHF_WRITE;
297 if (Kind.isMergeableConst() || Kind.isMergeableCString())
298 ElfSectionFlags |= ELFSection::SHF_MERGE;
299 if (Kind.isThreadLocal())
300 ElfSectionFlags |= ELFSection::SHF_TLS;
301 if (Kind.isMergeableCString())
302 ElfSectionFlags |= ELFSection::SHF_STRINGS;
304 return ElfSectionFlags;
307 // isUndefOrNull - The constant is either a null initialized value or an
309 static bool isUndefOrNull(const Constant *CV) {
310 return (CV->isNullValue() || isa<UndefValue>(CV));
313 // isELFUndefSym - the symbol has no section and must be placed in
314 // the symbol table with a reference to the null section.
315 static bool isELFUndefSym(const GlobalValue *GV) {
316 // Functions which make up until this point references are an undef symbol
317 return GV->isDeclaration() || (isa<Function>(GV));
320 // isELFBssSym - for an undef or null value, the symbol must go to a bss
321 // section if it's not weak for linker, otherwise it's a common sym.
322 static bool isELFBssSym(const GlobalVariable *GV, SectionKind Kind) {
323 const Constant *CV = GV->getInitializer();
325 return (!Kind.isMergeableCString() &&
327 !GV->isWeakForLinker());
330 // isELFCommonSym - for an undef or null value, the symbol must go to a
331 // common section if it's weak for linker, otherwise bss.
332 static bool isELFCommonSym(const GlobalVariable *GV) {
333 return (isUndefOrNull(GV->getInitializer()) && GV->isWeakForLinker());
336 // EmitGlobal - Choose the right section for global and emit it
337 void ELFWriter::EmitGlobal(const GlobalValue *GV) {
339 // Check if the referenced symbol is already emitted
340 if (GblSymLookup.find(GV) != GblSymLookup.end())
343 // Handle ELF Bind, Visibility and Type for the current symbol
344 unsigned SymBind = getGlobalELFBinding(GV);
345 unsigned SymType = getGlobalELFType(GV);
347 // All undef symbols have the same binding, type and visibily and
348 // are classified regardless of their type.
349 ELFSym *GblSym = isELFUndefSym(GV) ? ELFSym::getUndefGV(GV, SymBind)
350 : ELFSym::getGV(GV, SymBind, SymType, getGlobalELFVisibility(GV));
352 if (!isELFUndefSym(GV)) {
353 assert(isa<GlobalVariable>(GV) && "GV not a global variable!");
354 const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV);
356 // Handle special llvm globals
357 if (EmitSpecialLLVMGlobal(GVar))
360 // Get the ELF section where this global belongs from TLOF
361 const MCSection *S = TLOF.SectionForGlobal(GV, Mang, TM);
362 SectionKind Kind = ((MCSectionELF*)S)->getKind();
363 unsigned SectionFlags = getElfSectionFlags(Kind);
365 // The symbol align should update the section alignment if needed
366 const TargetData *TD = TM.getTargetData();
367 unsigned Align = TD->getPreferredAlignment(GVar);
368 unsigned Size = TD->getTypeAllocSize(GVar->getInitializer()->getType());
371 if (isELFCommonSym(GVar)) {
372 GblSym->SectionIdx = ELFSection::SHN_COMMON;
373 getSection(((MCSectionELF*)S)->getName(),
374 ELFSection::SHT_NOBITS, SectionFlags, 1);
376 // A new linkonce section is created for each global in the
377 // common section, the default alignment is 1 and the symbol
378 // value contains its alignment.
379 GblSym->Value = Align;
381 } else if (isELFBssSym(GVar, Kind)) {
383 getSection(((MCSectionELF*)S)->getName(), ELFSection::SHT_NOBITS,
385 GblSym->SectionIdx = ES.SectionIdx;
387 // Update the size with alignment and the next object can
388 // start in the right offset in the section
389 if (Align) ES.Size = (ES.Size + Align-1) & ~(Align-1);
390 ES.Align = std::max(ES.Align, Align);
392 // GblSym->Value should contain the virtual offset inside the section.
393 // Virtual because the BSS space is not allocated on ELF objects
394 GblSym->Value = ES.Size;
397 } else { // The symbol must go to some kind of data section
399 getSection(((MCSectionELF*)S)->getName(), ELFSection::SHT_PROGBITS,
401 GblSym->SectionIdx = ES.SectionIdx;
403 // GblSym->Value should contain the symbol offset inside the section,
404 // and all symbols should start on their required alignment boundary
405 ES.Align = std::max(ES.Align, Align);
406 ES.emitAlignment(Align);
407 GblSym->Value = ES.size();
409 // Emit the global to the data section 'ES'
410 EmitGlobalConstant(GVar->getInitializer(), ES);
414 if (GV->hasPrivateLinkage()) {
415 // For a private symbols, keep track of the index inside the
416 // private list since it will never go to the symbol table and
417 // won't be patched up later.
418 PrivateSyms.push_back(GblSym);
419 GblSymLookup[GV] = PrivateSyms.size()-1;
421 // Non private symbol are left with zero indices until they are patched
422 // up during the symbol table emition (where the indicies are created).
423 SymbolList.push_back(GblSym);
424 GblSymLookup[GV] = 0;
428 void ELFWriter::EmitGlobalConstantStruct(const ConstantStruct *CVS,
431 // Print the fields in successive locations. Pad to align if needed!
432 const TargetData *TD = TM.getTargetData();
433 unsigned Size = TD->getTypeAllocSize(CVS->getType());
434 const StructLayout *cvsLayout = TD->getStructLayout(CVS->getType());
435 uint64_t sizeSoFar = 0;
436 for (unsigned i = 0, e = CVS->getNumOperands(); i != e; ++i) {
437 const Constant* field = CVS->getOperand(i);
439 // Check if padding is needed and insert one or more 0s.
440 uint64_t fieldSize = TD->getTypeAllocSize(field->getType());
441 uint64_t padSize = ((i == e-1 ? Size : cvsLayout->getElementOffset(i+1))
442 - cvsLayout->getElementOffset(i)) - fieldSize;
443 sizeSoFar += fieldSize + padSize;
445 // Now print the actual field value.
446 EmitGlobalConstant(field, GblS);
448 // Insert padding - this may include padding to increase the size of the
449 // current field up to the ABI size (if the struct is not packed) as well
450 // as padding to ensure that the next field starts at the right offset.
451 GblS.emitZeros(padSize);
453 assert(sizeSoFar == cvsLayout->getSizeInBytes() &&
454 "Layout of constant struct may be incorrect!");
457 void ELFWriter::EmitGlobalConstant(const Constant *CV, ELFSection &GblS) {
458 const TargetData *TD = TM.getTargetData();
459 unsigned Size = TD->getTypeAllocSize(CV->getType());
461 if (const ConstantArray *CVA = dyn_cast<ConstantArray>(CV)) {
462 for (unsigned i = 0, e = CVA->getNumOperands(); i != e; ++i)
463 EmitGlobalConstant(CVA->getOperand(i), GblS);
465 } else if (isa<ConstantAggregateZero>(CV)) {
466 GblS.emitZeros(Size);
468 } else if (const ConstantStruct *CVS = dyn_cast<ConstantStruct>(CV)) {
469 EmitGlobalConstantStruct(CVS, GblS);
471 } else if (const ConstantFP *CFP = dyn_cast<ConstantFP>(CV)) {
472 APInt Val = CFP->getValueAPF().bitcastToAPInt();
473 if (CFP->getType() == Type::DoubleTy)
474 GblS.emitWord64(Val.getZExtValue());
475 else if (CFP->getType() == Type::FloatTy)
476 GblS.emitWord32(Val.getZExtValue());
477 else if (CFP->getType() == Type::X86_FP80Ty) {
478 unsigned PadSize = TD->getTypeAllocSize(Type::X86_FP80Ty)-
479 TD->getTypeStoreSize(Type::X86_FP80Ty);
480 GblS.emitWordFP80(Val.getRawData(), PadSize);
481 } else if (CFP->getType() == Type::PPC_FP128Ty)
482 llvm_unreachable("PPC_FP128Ty global emission not implemented");
484 } else if (const ConstantInt *CI = dyn_cast<ConstantInt>(CV)) {
486 GblS.emitByte(CI->getZExtValue());
488 GblS.emitWord16(CI->getZExtValue());
490 GblS.emitWord32(CI->getZExtValue());
492 EmitGlobalConstantLargeInt(CI, GblS);
494 } else if (const ConstantVector *CP = dyn_cast<ConstantVector>(CV)) {
495 const VectorType *PTy = CP->getType();
496 for (unsigned I = 0, E = PTy->getNumElements(); I < E; ++I)
497 EmitGlobalConstant(CP->getOperand(I), GblS);
499 } else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(CV)) {
500 // Resolve a constant expression which returns a (Constant, Offset)
501 // pair. If 'Res.first' is a GlobalValue, emit a relocation with
502 // the offset 'Res.second', otherwise emit a global constant like
503 // it is always done for not contant expression types.
504 CstExprResTy Res = ResolveConstantExpr(CE);
505 const Constant *Op = Res.first;
507 if (isa<GlobalValue>(Op))
508 EmitGlobalDataRelocation(cast<const GlobalValue>(Op),
509 TD->getTypeAllocSize(Op->getType()),
512 EmitGlobalConstant(Op, GblS);
515 } else if (CV->getType()->getTypeID() == Type::PointerTyID) {
516 // Fill the data entry with zeros or emit a relocation entry
517 if (isa<ConstantPointerNull>(CV))
518 GblS.emitZeros(Size);
520 EmitGlobalDataRelocation(cast<const GlobalValue>(CV),
523 } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(CV)) {
524 // This is a constant address for a global variable or function and
525 // therefore must be referenced using a relocation entry.
526 EmitGlobalDataRelocation(GV, Size, GblS);
531 raw_string_ostream ErrorMsg(msg);
532 ErrorMsg << "Constant unimp for type: " << *CV->getType();
533 llvm_report_error(ErrorMsg.str());
536 // ResolveConstantExpr - Resolve the constant expression until it stop
537 // yielding other constant expressions.
538 CstExprResTy ELFWriter::ResolveConstantExpr(const Constant *CV) {
539 const TargetData *TD = TM.getTargetData();
541 // There ins't constant expression inside others anymore
542 if (!isa<ConstantExpr>(CV))
543 return std::make_pair(CV, 0);
545 const ConstantExpr *CE = dyn_cast<ConstantExpr>(CV);
546 switch (CE->getOpcode()) {
547 case Instruction::BitCast:
548 return ResolveConstantExpr(CE->getOperand(0));
550 case Instruction::GetElementPtr: {
551 const Constant *ptrVal = CE->getOperand(0);
552 SmallVector<Value*, 8> idxVec(CE->op_begin()+1, CE->op_end());
553 int64_t Offset = TD->getIndexedOffset(ptrVal->getType(), &idxVec[0],
555 return std::make_pair(ptrVal, Offset);
557 case Instruction::IntToPtr: {
558 Constant *Op = CE->getOperand(0);
559 Op = ConstantExpr::getIntegerCast(Op, TD->getIntPtrType(), false/*ZExt*/);
560 return ResolveConstantExpr(Op);
562 case Instruction::PtrToInt: {
563 Constant *Op = CE->getOperand(0);
564 const Type *Ty = CE->getType();
566 // We can emit the pointer value into this slot if the slot is an
567 // integer slot greater or equal to the size of the pointer.
568 if (TD->getTypeAllocSize(Ty) == TD->getTypeAllocSize(Op->getType()))
569 return ResolveConstantExpr(Op);
571 llvm_unreachable("Integer size less then pointer size");
573 case Instruction::Add:
574 case Instruction::Sub: {
575 // Only handle cases where there's a constant expression with GlobalValue
576 // as first operand and ConstantInt as second, which are the cases we can
577 // solve direclty using a relocation entry. GlobalValue=Op0, CstInt=Op1
578 // 1) Instruction::Add => (global) + CstInt
579 // 2) Instruction::Sub => (global) + -CstInt
580 const Constant *Op0 = CE->getOperand(0);
581 const Constant *Op1 = CE->getOperand(1);
582 assert(isa<ConstantInt>(Op1) && "Op1 must be a ConstantInt");
584 CstExprResTy Res = ResolveConstantExpr(Op0);
585 assert(isa<GlobalValue>(Res.first) && "Op0 must be a GlobalValue");
587 const APInt &RHS = cast<ConstantInt>(Op1)->getValue();
588 switch (CE->getOpcode()) {
589 case Instruction::Add:
590 return std::make_pair(Res.first, RHS.getSExtValue());
591 case Instruction::Sub:
592 return std::make_pair(Res.first, (-RHS).getSExtValue());
597 std::string msg(CE->getOpcodeName());
598 raw_string_ostream ErrorMsg(msg);
599 ErrorMsg << ": Unsupported ConstantExpr type";
600 llvm_report_error(ErrorMsg.str());
602 return std::make_pair(CV, 0); // silence warning
605 void ELFWriter::EmitGlobalDataRelocation(const GlobalValue *GV, unsigned Size,
606 ELFSection &GblS, int64_t Offset) {
607 // Create the relocation entry for the global value
608 MachineRelocation MR =
609 MachineRelocation::getGV(GblS.getCurrentPCOffset(),
610 TEW->getAbsoluteLabelMachineRelTy(),
611 const_cast<GlobalValue*>(GV),
614 // Fill the data entry with zeros
615 GblS.emitZeros(Size);
617 // Add the relocation entry for the current data section
618 GblS.addRelocation(MR);
621 void ELFWriter::EmitGlobalConstantLargeInt(const ConstantInt *CI,
623 const TargetData *TD = TM.getTargetData();
624 unsigned BitWidth = CI->getBitWidth();
625 assert(isPowerOf2_32(BitWidth) &&
626 "Non-power-of-2-sized integers not handled!");
628 const uint64_t *RawData = CI->getValue().getRawData();
630 for (unsigned i = 0, e = BitWidth / 64; i != e; ++i) {
631 Val = (TD->isBigEndian()) ? RawData[e - i - 1] : RawData[i];
636 /// EmitSpecialLLVMGlobal - Check to see if the specified global is a
637 /// special global used by LLVM. If so, emit it and return true, otherwise
638 /// do nothing and return false.
639 bool ELFWriter::EmitSpecialLLVMGlobal(const GlobalVariable *GV) {
640 if (GV->getName() == "llvm.used")
641 llvm_unreachable("not implemented yet");
643 // Ignore debug and non-emitted data. This handles llvm.compiler.used.
644 if (GV->getSection() == "llvm.metadata" ||
645 GV->hasAvailableExternallyLinkage())
648 if (!GV->hasAppendingLinkage()) return false;
650 assert(GV->hasInitializer() && "Not a special LLVM global!");
652 const TargetData *TD = TM.getTargetData();
653 unsigned Align = TD->getPointerPrefAlignment();
654 if (GV->getName() == "llvm.global_ctors") {
655 ELFSection &Ctor = getCtorSection();
656 Ctor.emitAlignment(Align);
657 EmitXXStructorList(GV->getInitializer(), Ctor);
661 if (GV->getName() == "llvm.global_dtors") {
662 ELFSection &Dtor = getDtorSection();
663 Dtor.emitAlignment(Align);
664 EmitXXStructorList(GV->getInitializer(), Dtor);
671 /// EmitXXStructorList - Emit the ctor or dtor list. This just emits out the
672 /// function pointers, ignoring the init priority.
673 void ELFWriter::EmitXXStructorList(Constant *List, ELFSection &Xtor) {
674 // Should be an array of '{ int, void ()* }' structs. The first value is the
675 // init priority, which we ignore.
676 if (!isa<ConstantArray>(List)) return;
677 ConstantArray *InitList = cast<ConstantArray>(List);
678 for (unsigned i = 0, e = InitList->getNumOperands(); i != e; ++i)
679 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(InitList->getOperand(i))){
680 if (CS->getNumOperands() != 2) return; // Not array of 2-element structs.
682 if (CS->getOperand(1)->isNullValue())
683 return; // Found a null terminator, exit printing.
684 // Emit the function pointer.
685 EmitGlobalConstant(CS->getOperand(1), Xtor);
689 bool ELFWriter::runOnMachineFunction(MachineFunction &MF) {
690 // Nothing to do here, this is all done through the ElfCE object above.
694 /// doFinalization - Now that the module has been completely processed, emit
695 /// the ELF file to 'O'.
696 bool ELFWriter::doFinalization(Module &M) {
697 // Emit .data section placeholder
700 // Emit .bss section placeholder
703 // Build and emit data, bss and "common" sections.
704 for (Module::global_iterator I = M.global_begin(), E = M.global_end();
708 // Emit all pending globals
709 for (PendingGblsIter I = PendingGlobals.begin(), E = PendingGlobals.end();
713 // Emit all pending externals
714 for (PendingExtsIter I = PendingExternals.begin(), E = PendingExternals.end();
716 SymbolList.push_back(ELFSym::getExtSym(*I));
718 // Emit non-executable stack note
719 if (TAI->getNonexecutableStackDirective())
720 getNonExecStackSection();
722 // Emit a symbol for each section created until now, skip null section
723 for (unsigned i = 1, e = SectionList.size(); i < e; ++i) {
724 ELFSection &ES = *SectionList[i];
725 ELFSym *SectionSym = ELFSym::getSectionSym();
726 SectionSym->SectionIdx = ES.SectionIdx;
727 SymbolList.push_back(SectionSym);
728 ES.Sym = SymbolList.back();
732 EmitStringTable(M.getModuleIdentifier());
734 // Emit the symbol table now, if non-empty.
737 // Emit the relocation sections.
740 // Emit the sections string table.
741 EmitSectionTableStringTable();
743 // Dump the sections and section table to the .o file.
744 OutputSectionsAndSectionTable();
746 // We are done with the abstract symbols.
751 // Release the name mangler object.
752 delete Mang; Mang = 0;
756 // RelocateField - Patch relocatable field with 'Offset' in 'BO'
757 // using a 'Value' of known 'Size'
758 void ELFWriter::RelocateField(BinaryObject &BO, uint32_t Offset,
759 int64_t Value, unsigned Size) {
761 BO.fixWord32(Value, Offset);
763 BO.fixWord64(Value, Offset);
765 llvm_unreachable("don't know howto patch relocatable field");
768 /// EmitRelocations - Emit relocations
769 void ELFWriter::EmitRelocations() {
771 // True if the target uses the relocation entry to hold the addend,
772 // otherwise the addend is written directly to the relocatable field.
773 bool HasRelA = TEW->hasRelocationAddend();
775 // Create Relocation sections for each section which needs it.
776 for (unsigned i=0, e=SectionList.size(); i != e; ++i) {
777 ELFSection &S = *SectionList[i];
779 // This section does not have relocations
780 if (!S.hasRelocations()) continue;
781 ELFSection &RelSec = getRelocSection(S);
783 // 'Link' - Section hdr idx of the associated symbol table
784 // 'Info' - Section hdr idx of the section to which the relocation applies
785 ELFSection &SymTab = getSymbolTableSection();
786 RelSec.Link = SymTab.SectionIdx;
787 RelSec.Info = S.SectionIdx;
788 RelSec.EntSize = TEW->getRelocationEntrySize();
790 // Get the relocations from Section
791 std::vector<MachineRelocation> Relos = S.getRelocations();
792 for (std::vector<MachineRelocation>::iterator MRI = Relos.begin(),
793 MRE = Relos.end(); MRI != MRE; ++MRI) {
794 MachineRelocation &MR = *MRI;
796 // Relocatable field offset from the section start
797 unsigned RelOffset = MR.getMachineCodeOffset();
799 // Symbol index in the symbol table
802 // Target specific relocation field type and size
803 unsigned RelType = TEW->getRelocationType(MR.getRelocationType());
804 unsigned RelTySize = TEW->getRelocationTySize(RelType);
807 // There are several machine relocations types, and each one of
808 // them needs a different approach to retrieve the symbol table index.
809 if (MR.isGlobalValue()) {
810 const GlobalValue *G = MR.getGlobalValue();
811 int64_t GlobalOffset = MR.getConstantVal();
812 SymIdx = GblSymLookup[G];
813 if (G->hasPrivateLinkage()) {
814 // If the target uses a section offset in the relocation:
815 // SymIdx + Addend = section sym for global + section offset
816 unsigned SectionIdx = PrivateSyms[SymIdx]->SectionIdx;
817 Addend = PrivateSyms[SymIdx]->Value + GlobalOffset;
818 SymIdx = SectionList[SectionIdx]->getSymbolTableIndex();
820 Addend = TEW->getDefaultAddendForRelTy(RelType, GlobalOffset);
822 } else if (MR.isExternalSymbol()) {
823 const char *ExtSym = MR.getExternalSymbol();
824 SymIdx = ExtSymLookup[ExtSym];
825 Addend = TEW->getDefaultAddendForRelTy(RelType);
827 // Get the symbol index for the section symbol
828 unsigned SectionIdx = MR.getConstantVal();
829 SymIdx = SectionList[SectionIdx]->getSymbolTableIndex();
831 // The symbol offset inside the section
832 int64_t SymOffset = (int64_t)MR.getResultPointer();
834 // For pc relative relocations where symbols are defined in the same
835 // section they are referenced, ignore the relocation entry and patch
836 // the relocatable field with the symbol offset directly.
837 if (S.SectionIdx == SectionIdx && TEW->isPCRelativeRel(RelType)) {
838 int64_t Value = TEW->computeRelocation(SymOffset, RelOffset, RelType);
839 RelocateField(S, RelOffset, Value, RelTySize);
843 Addend = TEW->getDefaultAddendForRelTy(RelType, SymOffset);
846 // The target without addend on the relocation symbol must be
847 // patched in the relocation place itself to contain the addend
848 // otherwise write zeros to make sure there is no garbage there
849 RelocateField(S, RelOffset, HasRelA ? 0 : Addend, RelTySize);
851 // Get the relocation entry and emit to the relocation section
852 ELFRelocation Rel(RelOffset, SymIdx, RelType, HasRelA, Addend);
853 EmitRelocation(RelSec, Rel, HasRelA);
858 /// EmitRelocation - Write relocation 'Rel' to the relocation section 'Rel'
859 void ELFWriter::EmitRelocation(BinaryObject &RelSec, ELFRelocation &Rel,
861 RelSec.emitWord(Rel.getOffset());
862 RelSec.emitWord(Rel.getInfo(is64Bit));
864 RelSec.emitWord(Rel.getAddend());
867 /// EmitSymbol - Write symbol 'Sym' to the symbol table 'SymbolTable'
868 void ELFWriter::EmitSymbol(BinaryObject &SymbolTable, ELFSym &Sym) {
870 SymbolTable.emitWord32(Sym.NameIdx);
871 SymbolTable.emitByte(Sym.Info);
872 SymbolTable.emitByte(Sym.Other);
873 SymbolTable.emitWord16(Sym.SectionIdx);
874 SymbolTable.emitWord64(Sym.Value);
875 SymbolTable.emitWord64(Sym.Size);
877 SymbolTable.emitWord32(Sym.NameIdx);
878 SymbolTable.emitWord32(Sym.Value);
879 SymbolTable.emitWord32(Sym.Size);
880 SymbolTable.emitByte(Sym.Info);
881 SymbolTable.emitByte(Sym.Other);
882 SymbolTable.emitWord16(Sym.SectionIdx);
886 /// EmitSectionHeader - Write section 'Section' header in 'SHdrTab'
887 /// Section Header Table
888 void ELFWriter::EmitSectionHeader(BinaryObject &SHdrTab,
889 const ELFSection &SHdr) {
890 SHdrTab.emitWord32(SHdr.NameIdx);
891 SHdrTab.emitWord32(SHdr.Type);
893 SHdrTab.emitWord64(SHdr.Flags);
894 SHdrTab.emitWord(SHdr.Addr);
895 SHdrTab.emitWord(SHdr.Offset);
896 SHdrTab.emitWord64(SHdr.Size);
897 SHdrTab.emitWord32(SHdr.Link);
898 SHdrTab.emitWord32(SHdr.Info);
899 SHdrTab.emitWord64(SHdr.Align);
900 SHdrTab.emitWord64(SHdr.EntSize);
902 SHdrTab.emitWord32(SHdr.Flags);
903 SHdrTab.emitWord(SHdr.Addr);
904 SHdrTab.emitWord(SHdr.Offset);
905 SHdrTab.emitWord32(SHdr.Size);
906 SHdrTab.emitWord32(SHdr.Link);
907 SHdrTab.emitWord32(SHdr.Info);
908 SHdrTab.emitWord32(SHdr.Align);
909 SHdrTab.emitWord32(SHdr.EntSize);
913 /// EmitStringTable - If the current symbol table is non-empty, emit the string
915 void ELFWriter::EmitStringTable(const std::string &ModuleName) {
916 if (!SymbolList.size()) return; // Empty symbol table.
917 ELFSection &StrTab = getStringTableSection();
919 // Set the zero'th symbol to a null byte, as required.
922 // Walk on the symbol list and write symbol names into the string table.
924 for (ELFSymIter I=SymbolList.begin(), E=SymbolList.end(); I != E; ++I) {
928 if (Sym.isGlobalValue())
929 Name.append(Mang->getMangledName(Sym.getGlobalValue()));
930 else if (Sym.isExternalSym())
931 Name.append(Sym.getExternalSymbol());
932 else if (Sym.isFileType())
933 Name.append(ModuleName);
939 StrTab.emitString(Name);
941 // Keep track of the number of bytes emitted to this section.
942 Index += Name.size()+1;
945 assert(Index == StrTab.size());
949 // SortSymbols - On the symbol table local symbols must come before
950 // all other symbols with non-local bindings. The return value is
951 // the position of the first non local symbol.
952 unsigned ELFWriter::SortSymbols() {
953 unsigned FirstNonLocalSymbol;
954 std::vector<ELFSym*> LocalSyms, OtherSyms;
956 for (ELFSymIter I=SymbolList.begin(), E=SymbolList.end(); I != E; ++I) {
957 if ((*I)->isLocalBind())
958 LocalSyms.push_back(*I);
960 OtherSyms.push_back(*I);
963 FirstNonLocalSymbol = LocalSyms.size();
965 for (unsigned i = 0; i < FirstNonLocalSymbol; ++i)
966 SymbolList.push_back(LocalSyms[i]);
968 for (ELFSymIter I=OtherSyms.begin(), E=OtherSyms.end(); I != E; ++I)
969 SymbolList.push_back(*I);
974 return FirstNonLocalSymbol;
977 /// EmitSymbolTable - Emit the symbol table itself.
978 void ELFWriter::EmitSymbolTable() {
979 if (!SymbolList.size()) return; // Empty symbol table.
981 // Now that we have emitted the string table and know the offset into the
982 // string table of each symbol, emit the symbol table itself.
983 ELFSection &SymTab = getSymbolTableSection();
984 SymTab.Align = TEW->getPrefELFAlignment();
986 // Section Index of .strtab.
987 SymTab.Link = getStringTableSection().SectionIdx;
989 // Size of each symtab entry.
990 SymTab.EntSize = TEW->getSymTabEntrySize();
992 // Reorder the symbol table with local symbols first!
993 unsigned FirstNonLocalSymbol = SortSymbols();
995 // Emit all the symbols to the symbol table.
996 for (unsigned i = 0, e = SymbolList.size(); i < e; ++i) {
997 ELFSym &Sym = *SymbolList[i];
999 // Emit symbol to the symbol table
1000 EmitSymbol(SymTab, Sym);
1002 // Record the symbol table index for each symbol
1003 if (Sym.isGlobalValue())
1004 GblSymLookup[Sym.getGlobalValue()] = i;
1005 else if (Sym.isExternalSym())
1006 ExtSymLookup[Sym.getExternalSymbol()] = i;
1008 // Keep track on the symbol index into the symbol table
1012 // One greater than the symbol table index of the last local symbol
1013 SymTab.Info = FirstNonLocalSymbol;
1014 SymTab.Size = SymTab.size();
1017 /// EmitSectionTableStringTable - This method adds and emits a section for the
1018 /// ELF Section Table string table: the string table that holds all of the
1020 void ELFWriter::EmitSectionTableStringTable() {
1021 // First step: add the section for the string table to the list of sections:
1022 ELFSection &SHStrTab = getSectionHeaderStringTableSection();
1024 // Now that we know which section number is the .shstrtab section, update the
1025 // e_shstrndx entry in the ELF header.
1026 ElfHdr.fixWord16(SHStrTab.SectionIdx, ELFHdr_e_shstrndx_Offset);
1028 // Set the NameIdx of each section in the string table and emit the bytes for
1029 // the string table.
1032 for (ELFSectionIter I=SectionList.begin(), E=SectionList.end(); I != E; ++I) {
1033 ELFSection &S = *(*I);
1034 // Set the index into the table. Note if we have lots of entries with
1035 // common suffixes, we could memoize them here if we cared.
1037 SHStrTab.emitString(S.getName());
1039 // Keep track of the number of bytes emitted to this section.
1040 Index += S.getName().size()+1;
1043 // Set the size of .shstrtab now that we know what it is.
1044 assert(Index == SHStrTab.size());
1045 SHStrTab.Size = Index;
1048 /// OutputSectionsAndSectionTable - Now that we have constructed the file header
1049 /// and all of the sections, emit these to the ostream destination and emit the
1051 void ELFWriter::OutputSectionsAndSectionTable() {
1052 // Pass #1: Compute the file offset for each section.
1053 size_t FileOff = ElfHdr.size(); // File header first.
1055 // Adjust alignment of all section if needed, skip the null section.
1056 for (unsigned i=1, e=SectionList.size(); i < e; ++i) {
1057 ELFSection &ES = *SectionList[i];
1059 ES.Offset = FileOff;
1063 // Update Section size
1065 ES.Size = ES.size();
1067 // Align FileOff to whatever the alignment restrictions of the section are.
1069 FileOff = (FileOff+ES.Align-1) & ~(ES.Align-1);
1071 ES.Offset = FileOff;
1075 // Align Section Header.
1076 unsigned TableAlign = TEW->getPrefELFAlignment();
1077 FileOff = (FileOff+TableAlign-1) & ~(TableAlign-1);
1079 // Now that we know where all of the sections will be emitted, set the e_shnum
1080 // entry in the ELF header.
1081 ElfHdr.fixWord16(NumSections, ELFHdr_e_shnum_Offset);
1083 // Now that we know the offset in the file of the section table, update the
1084 // e_shoff address in the ELF header.
1085 ElfHdr.fixWord(FileOff, ELFHdr_e_shoff_Offset);
1087 // Now that we know all of the data in the file header, emit it and all of the
1089 O.write((char *)&ElfHdr.getData()[0], ElfHdr.size());
1090 FileOff = ElfHdr.size();
1092 // Section Header Table blob
1093 BinaryObject SHdrTable(isLittleEndian, is64Bit);
1095 // Emit all of sections to the file and build the section header table.
1096 for (ELFSectionIter I=SectionList.begin(), E=SectionList.end(); I != E; ++I) {
1097 ELFSection &S = *(*I);
1098 DOUT << "SectionIdx: " << S.SectionIdx << ", Name: " << S.getName()
1099 << ", Size: " << S.Size << ", Offset: " << S.Offset
1100 << ", SectionData Size: " << S.size() << "\n";
1102 // Align FileOff to whatever the alignment restrictions of the section are.
1105 for (size_t NewFileOff = (FileOff+S.Align-1) & ~(S.Align-1);
1106 FileOff != NewFileOff; ++FileOff)
1109 O.write((char *)&S.getData()[0], S.Size);
1113 EmitSectionHeader(SHdrTable, S);
1116 // Align output for the section table.
1117 for (size_t NewFileOff = (FileOff+TableAlign-1) & ~(TableAlign-1);
1118 FileOff != NewFileOff; ++FileOff)
1121 // Emit the section table itself.
1122 O.write((char *)&SHdrTable.getData()[0], SHdrTable.size());