source: clamav/trunk/libclamav/c++/llvm/lib/MC/ELFObjectWriter.cpp@ 319

Last change on this file since 319 was 319, checked in by Yuri Dario, 14 years ago

clamav: update trunk to 0.97.
File size: 31.5 KB
Line 
1//===- lib/MC/ELFObjectWriter.cpp - ELF File Writer -------------------===//
2//
3// The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file implements ELF object file writer information.
11//
12//===----------------------------------------------------------------------===//
13
14#include "llvm/MC/ELFObjectWriter.h"
15#include "llvm/ADT/STLExtras.h"
16#include "llvm/ADT/StringMap.h"
17#include "llvm/ADT/Twine.h"
18#include "llvm/MC/MCAssembler.h"
19#include "llvm/MC/MCAsmLayout.h"
20#include "llvm/MC/MCContext.h"
21#include "llvm/MC/MCELFSymbolFlags.h"
22#include "llvm/MC/MCExpr.h"
23#include "llvm/MC/MCObjectWriter.h"
24#include "llvm/MC/MCSectionELF.h"
25#include "llvm/MC/MCSymbol.h"
26#include "llvm/MC/MCValue.h"
27#include "llvm/Support/Debug.h"
28#include "llvm/Support/ErrorHandling.h"
29#include "llvm/Support/ELF.h"
30#include "llvm/Target/TargetAsmBackend.h"
31
32#include "../Target/X86/X86FixupKinds.h"
33
34#include <vector>
35using namespace llvm;
36
37namespace {
38
39 class ELFObjectWriterImpl {
40 static bool isFixupKindX86PCRel(unsigned Kind) {
41 switch (Kind) {
42 default:
43 return false;
44 case X86::reloc_pcrel_1byte:
45 case X86::reloc_pcrel_4byte:
46 case X86::reloc_riprel_4byte:
47 case X86::reloc_riprel_4byte_movq_load:
48 return true;
49 }
50 }
51
52 /*static bool isFixupKindX86RIPRel(unsigned Kind) {
53 return Kind == X86::reloc_riprel_4byte ||
54 Kind == X86::reloc_riprel_4byte_movq_load;
55 }*/
56
57
58 /// ELFSymbolData - Helper struct for containing some precomputed information
59 /// on symbols.
60 struct ELFSymbolData {
61 MCSymbolData *SymbolData;
62 uint64_t StringIndex;
63 uint32_t SectionIndex;
64
65 // Support lexicographic sorting.
66 bool operator<(const ELFSymbolData &RHS) const {
67 return SymbolData->getSymbol().getName() <
68 RHS.SymbolData->getSymbol().getName();
69 }
70 };
71
72 /// @name Relocation Data
73 /// @{
74
75 struct ELFRelocationEntry {
76 // Make these big enough for both 32-bit and 64-bit
77 uint64_t r_offset;
78 uint64_t r_info;
79 uint64_t r_addend;
80
81 // Support lexicographic sorting.
82 bool operator<(const ELFRelocationEntry &RE) const {
83 return RE.r_offset < r_offset;
84 }
85 };
86
87 llvm::DenseMap<const MCSectionData*,
88 std::vector<ELFRelocationEntry> > Relocations;
89 DenseMap<const MCSection*, uint64_t> SectionStringTableIndex;
90
91 /// @}
92 /// @name Symbol Table Data
93 /// @{
94
95 SmallString<256> StringTable;
96 std::vector<ELFSymbolData> LocalSymbolData;
97 std::vector<ELFSymbolData> ExternalSymbolData;
98 std::vector<ELFSymbolData> UndefinedSymbolData;
99
100 /// @}
101
102 ELFObjectWriter *Writer;
103
104 raw_ostream &OS;
105
106 // This holds the current offset into the object file.
107 size_t FileOff;
108
109 unsigned Is64Bit : 1;
110
111 bool HasRelocationAddend;
112
113 // This holds the symbol table index of the last local symbol.
114 unsigned LastLocalSymbolIndex;
115 // This holds the .strtab section index.
116 unsigned StringTableIndex;
117
118 unsigned ShstrtabIndex;
119
120 public:
121 ELFObjectWriterImpl(ELFObjectWriter *_Writer, bool _Is64Bit,
122 bool _HasRelAddend)
123 : Writer(_Writer), OS(Writer->getStream()), FileOff(0),
124 Is64Bit(_Is64Bit), HasRelocationAddend(_HasRelAddend) {
125 }
126
127 void Write8(uint8_t Value) { Writer->Write8(Value); }
128 void Write16(uint16_t Value) { Writer->Write16(Value); }
129 void Write32(uint32_t Value) { Writer->Write32(Value); }
130 //void Write64(uint64_t Value) { Writer->Write64(Value); }
131 void WriteZeros(unsigned N) { Writer->WriteZeros(N); }
132 //void WriteBytes(StringRef Str, unsigned ZeroFillSize = 0) {
133 // Writer->WriteBytes(Str, ZeroFillSize);
134 //}
135
136 void WriteWord(uint64_t W) {
137 if (Is64Bit)
138 Writer->Write64(W);
139 else
140 Writer->Write32(W);
141 }
142
143 void String8(char *buf, uint8_t Value) {
144 buf[0] = Value;
145 }
146
147 void StringLE16(char *buf, uint16_t Value) {
148 buf[0] = char(Value >> 0);
149 buf[1] = char(Value >> 8);
150 }
151
152 void StringLE32(char *buf, uint32_t Value) {
153 StringLE16(buf, uint16_t(Value >> 0));
154 StringLE16(buf + 2, uint16_t(Value >> 16));
155 }
156
157 void StringLE64(char *buf, uint64_t Value) {
158 StringLE32(buf, uint32_t(Value >> 0));
159 StringLE32(buf + 4, uint32_t(Value >> 32));
160 }
161
162 void StringBE16(char *buf ,uint16_t Value) {
163 buf[0] = char(Value >> 8);
164 buf[1] = char(Value >> 0);
165 }
166
167 void StringBE32(char *buf, uint32_t Value) {
168 StringBE16(buf, uint16_t(Value >> 16));
169 StringBE16(buf + 2, uint16_t(Value >> 0));
170 }
171
172 void StringBE64(char *buf, uint64_t Value) {
173 StringBE32(buf, uint32_t(Value >> 32));
174 StringBE32(buf + 4, uint32_t(Value >> 0));
175 }
176
177 void String16(char *buf, uint16_t Value) {
178 if (Writer->isLittleEndian())
179 StringLE16(buf, Value);
180 else
181 StringBE16(buf, Value);
182 }
183
184 void String32(char *buf, uint32_t Value) {
185 if (Writer->isLittleEndian())
186 StringLE32(buf, Value);
187 else
188 StringBE32(buf, Value);
189 }
190
191 void String64(char *buf, uint64_t Value) {
192 if (Writer->isLittleEndian())
193 StringLE64(buf, Value);
194 else
195 StringBE64(buf, Value);
196 }
197
198 void WriteHeader(uint64_t SectionDataSize, unsigned NumberOfSections);
199
200 void WriteSymbolEntry(MCDataFragment *F, uint64_t name, uint8_t info,
201 uint64_t value, uint64_t size,
202 uint8_t other, uint16_t shndx);
203
204 void WriteSymbol(MCDataFragment *F, ELFSymbolData &MSD,
205 const MCAsmLayout &Layout);
206
207 void WriteSymbolTable(MCDataFragment *F, const MCAssembler &Asm,
208 const MCAsmLayout &Layout);
209
210 void RecordRelocation(const MCAssembler &Asm, const MCAsmLayout &Layout,
211 const MCFragment *Fragment, const MCFixup &Fixup,
212 MCValue Target, uint64_t &FixedValue);
213
214 uint64_t getSymbolIndexInSymbolTable(const MCAssembler &Asm,
215 const MCSymbol *S);
216
217 /// ComputeSymbolTable - Compute the symbol table data
218 ///
219 /// \param StringTable [out] - The string table data.
220 /// \param StringIndexMap [out] - Map from symbol names to offsets in the
221 /// string table.
222 void ComputeSymbolTable(MCAssembler &Asm);
223
224 void WriteRelocation(MCAssembler &Asm, MCAsmLayout &Layout,
225 const MCSectionData &SD);
226
227 void WriteRelocations(MCAssembler &Asm, MCAsmLayout &Layout) {
228 for (MCAssembler::const_iterator it = Asm.begin(),
229 ie = Asm.end(); it != ie; ++it) {
230 WriteRelocation(Asm, Layout, *it);
231 }
232 }
233
234 void CreateMetadataSections(MCAssembler &Asm, MCAsmLayout &Layout);
235
236 void ExecutePostLayoutBinding(MCAssembler &Asm) {
237 // Compute symbol table information.
238 ComputeSymbolTable(Asm);
239 }
240
241 void WriteSecHdrEntry(uint32_t Name, uint32_t Type, uint64_t Flags,
242 uint64_t Address, uint64_t Offset,
243 uint64_t Size, uint32_t Link, uint32_t Info,
244 uint64_t Alignment, uint64_t EntrySize);
245
246 void WriteRelocationsFragment(const MCAssembler &Asm, MCDataFragment *F,
247 const MCSectionData *SD);
248
249 void WriteObject(const MCAssembler &Asm, const MCAsmLayout &Layout);
250 };
251
252}
253
254// Emit the ELF header.
255void ELFObjectWriterImpl::WriteHeader(uint64_t SectionDataSize,
256 unsigned NumberOfSections) {
257 // ELF Header
258 // ----------
259 //
260 // Note
261 // ----
262 // emitWord method behaves differently for ELF32 and ELF64, writing
263 // 4 bytes in the former and 8 in the latter.
264
265 Write8(0x7f); // e_ident[EI_MAG0]
266 Write8('E'); // e_ident[EI_MAG1]
267 Write8('L'); // e_ident[EI_MAG2]
268 Write8('F'); // e_ident[EI_MAG3]
269
270 Write8(Is64Bit ? ELF::ELFCLASS64 : ELF::ELFCLASS32); // e_ident[EI_CLASS]
271
272 // e_ident[EI_DATA]
273 Write8(Writer->isLittleEndian() ? ELF::ELFDATA2LSB : ELF::ELFDATA2MSB);
274
275 Write8(ELF::EV_CURRENT); // e_ident[EI_VERSION]
276 Write8(ELF::ELFOSABI_LINUX); // e_ident[EI_OSABI]
277 Write8(0); // e_ident[EI_ABIVERSION]
278
279 WriteZeros(ELF::EI_NIDENT - ELF::EI_PAD);
280
281 Write16(ELF::ET_REL); // e_type
282
283 // FIXME: Make this configurable
284 Write16(Is64Bit ? ELF::EM_X86_64 : ELF::EM_386); // e_machine = target
285
286 Write32(ELF::EV_CURRENT); // e_version
287 WriteWord(0); // e_entry, no entry point in .o file
288 WriteWord(0); // e_phoff, no program header for .o
289 WriteWord(SectionDataSize + (Is64Bit ? sizeof(ELF::Elf64_Ehdr) :
290 sizeof(ELF::Elf32_Ehdr))); // e_shoff = sec hdr table off in bytes
291
292 // FIXME: Make this configurable.
293 Write32(0); // e_flags = whatever the target wants
294
295 // e_ehsize = ELF header size
296 Write16(Is64Bit ? sizeof(ELF::Elf64_Ehdr) : sizeof(ELF::Elf32_Ehdr));
297
298 Write16(0); // e_phentsize = prog header entry size
299 Write16(0); // e_phnum = # prog header entries = 0
300
301 // e_shentsize = Section header entry size
302 Write16(Is64Bit ? sizeof(ELF::Elf64_Shdr) : sizeof(ELF::Elf32_Shdr));
303
304 // e_shnum = # of section header ents
305 Write16(NumberOfSections);
306
307 // e_shstrndx = Section # of '.shstrtab'
308 Write16(ShstrtabIndex);
309}
310
311void ELFObjectWriterImpl::WriteSymbolEntry(MCDataFragment *F, uint64_t name,
312 uint8_t info, uint64_t value,
313 uint64_t size, uint8_t other,
314 uint16_t shndx) {
315 if (Is64Bit) {
316 char buf[8];
317
318 String32(buf, name);
319 F->getContents() += StringRef(buf, 4); // st_name
320
321 String8(buf, info);
322 F->getContents() += StringRef(buf, 1); // st_info
323
324 String8(buf, other);
325 F->getContents() += StringRef(buf, 1); // st_other
326
327 String16(buf, shndx);
328 F->getContents() += StringRef(buf, 2); // st_shndx
329
330 String64(buf, value);
331 F->getContents() += StringRef(buf, 8); // st_value
332
333 String64(buf, size);
334 F->getContents() += StringRef(buf, 8); // st_size
335 } else {
336 char buf[4];
337
338 String32(buf, name);
339 F->getContents() += StringRef(buf, 4); // st_name
340
341 String32(buf, value);
342 F->getContents() += StringRef(buf, 4); // st_value
343
344 String32(buf, size);
345 F->getContents() += StringRef(buf, 4); // st_size
346
347 String8(buf, info);
348 F->getContents() += StringRef(buf, 1); // st_info
349
350 String8(buf, other);
351 F->getContents() += StringRef(buf, 1); // st_other
352
353 String16(buf, shndx);
354 F->getContents() += StringRef(buf, 2); // st_shndx
355 }
356}
357
358void ELFObjectWriterImpl::WriteSymbol(MCDataFragment *F, ELFSymbolData &MSD,
359 const MCAsmLayout &Layout) {
360 MCSymbolData &Data = *MSD.SymbolData;
361 uint8_t Info = (Data.getFlags() & 0xff);
362 uint8_t Other = ((Data.getFlags() & 0xf00) >> ELF_STV_Shift);
363 uint64_t Value = 0;
364 uint64_t Size = 0;
365 const MCExpr *ESize;
366
367 if (Data.isCommon() && Data.isExternal())
368 Value = Data.getCommonAlignment();
369
370 if (!Data.isCommon())
371 if (MCFragment *FF = Data.getFragment())
372 Value = Layout.getSymbolAddress(&Data) -
373 Layout.getSectionAddress(FF->getParent());
374
375 ESize = Data.getSize();
376 if (Data.getSize()) {
377 MCValue Res;
378 if (ESize->getKind() == MCExpr::Binary) {
379 const MCBinaryExpr *BE = static_cast<const MCBinaryExpr *>(ESize);
380
381 if (BE->EvaluateAsRelocatable(Res, &Layout)) {
382 MCSymbolData &A =
383 Layout.getAssembler().getSymbolData(Res.getSymA()->getSymbol());
384 MCSymbolData &B =
385 Layout.getAssembler().getSymbolData(Res.getSymB()->getSymbol());
386
387 Size = Layout.getSymbolAddress(&A) - Layout.getSymbolAddress(&B);
388 }
389 } else if (ESize->getKind() == MCExpr::Constant) {
390 Size = static_cast<const MCConstantExpr *>(ESize)->getValue();
391 } else {
392 assert(0 && "Unsupported size expression");
393 }
394 }
395
396 // Write out the symbol table entry
397 WriteSymbolEntry(F, MSD.StringIndex, Info, Value,
398 Size, Other, MSD.SectionIndex);
399}
400
401void ELFObjectWriterImpl::WriteSymbolTable(MCDataFragment *F,
402 const MCAssembler &Asm,
403 const MCAsmLayout &Layout) {
404 // The string table must be emitted first because we need the index
405 // into the string table for all the symbol names.
406 assert(StringTable.size() && "Missing string table");
407
408 // FIXME: Make sure the start of the symbol table is aligned.
409
410 // The first entry is the undefined symbol entry.
411 unsigned EntrySize = Is64Bit ? ELF::SYMENTRY_SIZE64 : ELF::SYMENTRY_SIZE32;
412 F->getContents().append(EntrySize, '\x00');
413
414 // Write the symbol table entries.
415 LastLocalSymbolIndex = LocalSymbolData.size() + 1;
416 for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i) {
417 ELFSymbolData &MSD = LocalSymbolData[i];
418 WriteSymbol(F, MSD, Layout);
419 }
420
421 // Write out a symbol table entry for each section.
422 // leaving out the just added .symtab which is at
423 // the very end
424 unsigned Index = 1;
425 for (MCAssembler::const_iterator it = Asm.begin(),
426 ie = Asm.end(); it != ie; ++it, ++Index) {
427 const MCSectionELF &Section =
428 static_cast<const MCSectionELF&>(it->getSection());
429 // Leave out relocations so we don't have indexes within
430 // the relocations messed up
431 if (Section.getType() == ELF::SHT_RELA || Section.getType() == ELF::SHT_REL)
432 continue;
433 if (Index == Asm.size())
434 continue;
435 WriteSymbolEntry(F, 0, ELF::STT_SECTION, 0, 0, ELF::STV_DEFAULT, Index);
436 LastLocalSymbolIndex++;
437 }
438
439 for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i) {
440 ELFSymbolData &MSD = ExternalSymbolData[i];
441 MCSymbolData &Data = *MSD.SymbolData;
442 assert((Data.getFlags() & ELF_STB_Global) &&
443 "External symbol requires STB_GLOBAL flag");
444 WriteSymbol(F, MSD, Layout);
445 if (Data.getFlags() & ELF_STB_Local)
446 LastLocalSymbolIndex++;
447 }
448
449 for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i) {
450 ELFSymbolData &MSD = UndefinedSymbolData[i];
451 MCSymbolData &Data = *MSD.SymbolData;
452 Data.setFlags(Data.getFlags() | ELF_STB_Global);
453 WriteSymbol(F, MSD, Layout);
454 if (Data.getFlags() & ELF_STB_Local)
455 LastLocalSymbolIndex++;
456 }
457}
458
459// FIXME: this is currently X86/X86_64 only
460void ELFObjectWriterImpl::RecordRelocation(const MCAssembler &Asm,
461 const MCAsmLayout &Layout,
462 const MCFragment *Fragment,
463 const MCFixup &Fixup,
464 MCValue Target,
465 uint64_t &FixedValue) {
466 int64_t Addend = 0;
467 unsigned Index = 0;
468 int64_t Value = Target.getConstant();
469
470 if (!Target.isAbsolute()) {
471 const MCSymbol *Symbol = &Target.getSymA()->getSymbol();
472 MCSymbolData &SD = Asm.getSymbolData(*Symbol);
473 const MCSymbolData *Base = Asm.getAtom(Layout, &SD);
474 MCFragment *F = SD.getFragment();
475
476 if (Base) {
477 if (F && (!Symbol->isInSection() || SD.isCommon()) && !SD.isExternal()) {
478 Index = F->getParent()->getOrdinal() + LocalSymbolData.size() + 1;
479 Value += Layout.getSymbolAddress(&SD);
480 } else
481 Index = getSymbolIndexInSymbolTable(Asm, Symbol);
482 if (Base != &SD)
483 Value += Layout.getSymbolAddress(&SD) - Layout.getSymbolAddress(Base);
484 Addend = Value;
485 // Compensate for the addend on i386.
486 if (Is64Bit)
487 Value = 0;
488 } else {
489 if (F) {
490 // Index of the section in .symtab against this symbol
491 // is being relocated + 2 (empty section + abs. symbols).
492 Index = F->getParent()->getOrdinal() + LocalSymbolData.size() + 1;
493
494 MCSectionData *FSD = F->getParent();
495 // Offset of the symbol in the section
496 Addend = Layout.getSymbolAddress(&SD) - Layout.getSectionAddress(FSD);
497 } else {
498 FixedValue = Value;
499 return;
500 }
501 }
502 }
503
504 FixedValue = Value;
505
506 // determine the type of the relocation
507 bool IsPCRel = isFixupKindX86PCRel(Fixup.getKind());
508 unsigned Type;
509 if (Is64Bit) {
510 if (IsPCRel) {
511 Type = ELF::R_X86_64_PC32;
512 } else {
513 switch ((unsigned)Fixup.getKind()) {
514 default: llvm_unreachable("invalid fixup kind!");
515 case FK_Data_8: Type = ELF::R_X86_64_64; break;
516 case X86::reloc_pcrel_4byte:
517 case FK_Data_4:
518 // check that the offset fits within a signed long
519 if (isInt<32>(Target.getConstant()))
520 Type = ELF::R_X86_64_32S;
521 else
522 Type = ELF::R_X86_64_32;
523 break;
524 case FK_Data_2: Type = ELF::R_X86_64_16; break;
525 case X86::reloc_pcrel_1byte:
526 case FK_Data_1: Type = ELF::R_X86_64_8; break;
527 }
528 }
529 } else {
530 if (IsPCRel) {
531 Type = ELF::R_386_PC32;
532 } else {
533 switch ((unsigned)Fixup.getKind()) {
534 default: llvm_unreachable("invalid fixup kind!");
535 case X86::reloc_pcrel_4byte:
536 case FK_Data_4: Type = ELF::R_386_32; break;
537 case FK_Data_2: Type = ELF::R_386_16; break;
538 case X86::reloc_pcrel_1byte:
539 case FK_Data_1: Type = ELF::R_386_8; break;
540 }
541 }
542 }
543
544 ELFRelocationEntry ERE;
545
546 if (Is64Bit) {
547 struct ELF::Elf64_Rela ERE64;
548 ERE64.setSymbolAndType(Index, Type);
549 ERE.r_info = ERE64.r_info;
550 } else {
551 struct ELF::Elf32_Rela ERE32;
552 ERE32.setSymbolAndType(Index, Type);
553 ERE.r_info = ERE32.r_info;
554 }
555
556 ERE.r_offset = Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
557
558 if (HasRelocationAddend)
559 ERE.r_addend = Addend;
560 else
561 ERE.r_addend = 0; // Silence compiler warning.
562
563 Relocations[Fragment->getParent()].push_back(ERE);
564}
565
566uint64_t
567ELFObjectWriterImpl::getSymbolIndexInSymbolTable(const MCAssembler &Asm,
568 const MCSymbol *S) {
569 MCSymbolData &SD = Asm.getSymbolData(*S);
570
571 // Local symbol.
572 if (!SD.isExternal() && !S->isUndefined())
573 return SD.getIndex() + /* empty symbol */ 1;
574
575 // External or undefined symbol.
576 return SD.getIndex() + Asm.size() + /* empty symbol */ 1;
577}
578
579void ELFObjectWriterImpl::ComputeSymbolTable(MCAssembler &Asm) {
580 // Build section lookup table.
581 DenseMap<const MCSection*, uint8_t> SectionIndexMap;
582 unsigned Index = 1;
583 for (MCAssembler::iterator it = Asm.begin(),
584 ie = Asm.end(); it != ie; ++it, ++Index)
585 SectionIndexMap[&it->getSection()] = Index;
586
587 // Index 0 is always the empty string.
588 StringMap<uint64_t> StringIndexMap;
589 StringTable += '\x00';
590
591 // Add the data for local symbols.
592 for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
593 ie = Asm.symbol_end(); it != ie; ++it) {
594 const MCSymbol &Symbol = it->getSymbol();
595
596 // Ignore non-linker visible symbols.
597 if (!Asm.isSymbolLinkerVisible(Symbol))
598 continue;
599
600 if (it->isExternal() || Symbol.isUndefined())
601 continue;
602
603 uint64_t &Entry = StringIndexMap[Symbol.getName()];
604 if (!Entry) {
605 Entry = StringTable.size();
606 StringTable += Symbol.getName();
607 StringTable += '\x00';
608 }
609
610 ELFSymbolData MSD;
611 MSD.SymbolData = it;
612 MSD.StringIndex = Entry;
613
614 if (Symbol.isAbsolute()) {
615 MSD.SectionIndex = ELF::SHN_ABS;
616 LocalSymbolData.push_back(MSD);
617 } else {
618 MSD.SectionIndex = SectionIndexMap.lookup(&Symbol.getSection());
619 assert(MSD.SectionIndex && "Invalid section index!");
620 LocalSymbolData.push_back(MSD);
621 }
622 }
623
624 // Now add non-local symbols.
625 for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
626 ie = Asm.symbol_end(); it != ie; ++it) {
627 const MCSymbol &Symbol = it->getSymbol();
628
629 // Ignore non-linker visible symbols.
630 if (!Asm.isSymbolLinkerVisible(Symbol))
631 continue;
632
633 if (!it->isExternal() && !Symbol.isUndefined())
634 continue;
635
636 uint64_t &Entry = StringIndexMap[Symbol.getName()];
637 if (!Entry) {
638 Entry = StringTable.size();
639 StringTable += Symbol.getName();
640 StringTable += '\x00';
641 }
642
643 ELFSymbolData MSD;
644 MSD.SymbolData = it;
645 MSD.StringIndex = Entry;
646
647 if (Symbol.isUndefined()) {
648 MSD.SectionIndex = ELF::SHN_UNDEF;
649 // XXX: for some reason we dont Emit* this
650 it->setFlags(it->getFlags() | ELF_STB_Global);
651 UndefinedSymbolData.push_back(MSD);
652 } else if (Symbol.isAbsolute()) {
653 MSD.SectionIndex = ELF::SHN_ABS;
654 ExternalSymbolData.push_back(MSD);
655 } else if (it->isCommon()) {
656 MSD.SectionIndex = ELF::SHN_COMMON;
657 ExternalSymbolData.push_back(MSD);
658 } else {
659 MSD.SectionIndex = SectionIndexMap.lookup(&Symbol.getSection());
660 assert(MSD.SectionIndex && "Invalid section index!");
661 ExternalSymbolData.push_back(MSD);
662 }
663 }
664
665 // Symbols are required to be in lexicographic order.
666 array_pod_sort(LocalSymbolData.begin(), LocalSymbolData.end());
667 array_pod_sort(ExternalSymbolData.begin(), ExternalSymbolData.end());
668 array_pod_sort(UndefinedSymbolData.begin(), UndefinedSymbolData.end());
669
670 // Set the symbol indices. Local symbols must come before all other
671 // symbols with non-local bindings.
672 Index = 0;
673 for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i)
674 LocalSymbolData[i].SymbolData->setIndex(Index++);
675 for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i)
676 ExternalSymbolData[i].SymbolData->setIndex(Index++);
677 for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i)
678 UndefinedSymbolData[i].SymbolData->setIndex(Index++);
679}
680
681void ELFObjectWriterImpl::WriteRelocation(MCAssembler &Asm, MCAsmLayout &Layout,
682 const MCSectionData &SD) {
683 if (!Relocations[&SD].empty()) {
684 MCContext &Ctx = Asm.getContext();
685 const MCSection *RelaSection;
686 const MCSectionELF &Section =
687 static_cast<const MCSectionELF&>(SD.getSection());
688
689 const StringRef SectionName = Section.getSectionName();
690 std::string RelaSectionName = HasRelocationAddend ? ".rela" : ".rel";
691 RelaSectionName += SectionName;
692
693 unsigned EntrySize;
694 if (HasRelocationAddend)
695 EntrySize = Is64Bit ? sizeof(ELF::Elf64_Rela) : sizeof(ELF::Elf32_Rela);
696 else
697 EntrySize = Is64Bit ? sizeof(ELF::Elf64_Rel) : sizeof(ELF::Elf32_Rel);
698
699 RelaSection = Ctx.getELFSection(RelaSectionName, HasRelocationAddend ?
700 ELF::SHT_RELA : ELF::SHT_REL, 0,
701 SectionKind::getReadOnly(),
702 false, EntrySize);
703
704 MCSectionData &RelaSD = Asm.getOrCreateSectionData(*RelaSection);
705 RelaSD.setAlignment(1);
706
707 MCDataFragment *F = new MCDataFragment(&RelaSD);
708
709 WriteRelocationsFragment(Asm, F, &SD);
710
711 Asm.AddSectionToTheEnd(RelaSD, Layout);
712 }
713}
714
715void ELFObjectWriterImpl::WriteSecHdrEntry(uint32_t Name, uint32_t Type,
716 uint64_t Flags, uint64_t Address,
717 uint64_t Offset, uint64_t Size,
718 uint32_t Link, uint32_t Info,
719 uint64_t Alignment,
720 uint64_t EntrySize) {
721 Write32(Name); // sh_name: index into string table
722 Write32(Type); // sh_type
723 WriteWord(Flags); // sh_flags
724 WriteWord(Address); // sh_addr
725 WriteWord(Offset); // sh_offset
726 WriteWord(Size); // sh_size
727 Write32(Link); // sh_link
728 Write32(Info); // sh_info
729 WriteWord(Alignment); // sh_addralign
730 WriteWord(EntrySize); // sh_entsize
731}
732
733void ELFObjectWriterImpl::WriteRelocationsFragment(const MCAssembler &Asm,
734 MCDataFragment *F,
735 const MCSectionData *SD) {
736 std::vector<ELFRelocationEntry> &Relocs = Relocations[SD];
737 // sort by the r_offset just like gnu as does
738 array_pod_sort(Relocs.begin(), Relocs.end());
739
740 for (unsigned i = 0, e = Relocs.size(); i != e; ++i) {
741 ELFRelocationEntry entry = Relocs[e - i - 1];
742
743 unsigned WordSize = Is64Bit ? 8 : 4;
744 F->getContents() += StringRef((const char *)&entry.r_offset, WordSize);
745 F->getContents() += StringRef((const char *)&entry.r_info, WordSize);
746
747 if (HasRelocationAddend)
748 F->getContents() += StringRef((const char *)&entry.r_addend, WordSize);
749 }
750}
751
752void ELFObjectWriterImpl::CreateMetadataSections(MCAssembler &Asm,
753 MCAsmLayout &Layout) {
754 MCContext &Ctx = Asm.getContext();
755 MCDataFragment *F;
756
757 WriteRelocations(Asm, Layout);
758
759 const MCSection *SymtabSection;
760 unsigned EntrySize = Is64Bit ? ELF::SYMENTRY_SIZE64 : ELF::SYMENTRY_SIZE32;
761
762 SymtabSection = Ctx.getELFSection(".symtab", ELF::SHT_SYMTAB, 0,
763 SectionKind::getReadOnly(),
764 false, EntrySize);
765
766 MCSectionData &SymtabSD = Asm.getOrCreateSectionData(*SymtabSection);
767
768 SymtabSD.setAlignment(Is64Bit ? 8 : 4);
769
770 F = new MCDataFragment(&SymtabSD);
771
772 // Symbol table
773 WriteSymbolTable(F, Asm, Layout);
774 Asm.AddSectionToTheEnd(SymtabSD, Layout);
775
776 const MCSection *StrtabSection;
777 StrtabSection = Ctx.getELFSection(".strtab", ELF::SHT_STRTAB, 0,
778 SectionKind::getReadOnly(), false);
779
780 MCSectionData &StrtabSD = Asm.getOrCreateSectionData(*StrtabSection);
781 StrtabSD.setAlignment(1);
782
783 // FIXME: This isn't right. If the sections get rearranged this will
784 // be wrong. We need a proper lookup.
785 StringTableIndex = Asm.size();
786
787 F = new MCDataFragment(&StrtabSD);
788 F->getContents().append(StringTable.begin(), StringTable.end());
789 Asm.AddSectionToTheEnd(StrtabSD, Layout);
790
791 const MCSection *ShstrtabSection;
792 ShstrtabSection = Ctx.getELFSection(".shstrtab", ELF::SHT_STRTAB, 0,
793 SectionKind::getReadOnly(), false);
794
795 MCSectionData &ShstrtabSD = Asm.getOrCreateSectionData(*ShstrtabSection);
796 ShstrtabSD.setAlignment(1);
797
798 F = new MCDataFragment(&ShstrtabSD);
799
800 // FIXME: This isn't right. If the sections get rearranged this will
801 // be wrong. We need a proper lookup.
802 ShstrtabIndex = Asm.size();
803
804 // Section header string table.
805 //
806 // The first entry of a string table holds a null character so skip
807 // section 0.
808 uint64_t Index = 1;
809 F->getContents() += '\x00';
810
811 for (MCAssembler::const_iterator it = Asm.begin(),
812 ie = Asm.end(); it != ie; ++it) {
813 const MCSectionELF &Section =
814 static_cast<const MCSectionELF&>(it->getSection());
815
816 // Remember the index into the string table so we can write it
817 // into the sh_name field of the section header table.
818 SectionStringTableIndex[&it->getSection()] = Index;
819
820 Index += Section.getSectionName().size() + 1;
821 F->getContents() += Section.getSectionName();
822 F->getContents() += '\x00';
823 }
824
825 Asm.AddSectionToTheEnd(ShstrtabSD, Layout);
826}
827
828void ELFObjectWriterImpl::WriteObject(const MCAssembler &Asm,
829 const MCAsmLayout &Layout) {
830 CreateMetadataSections(const_cast<MCAssembler&>(Asm),
831 const_cast<MCAsmLayout&>(Layout));
832
833 // Add 1 for the null section.
834 unsigned NumSections = Asm.size() + 1;
835
836 uint64_t SectionDataSize = 0;
837
838 for (MCAssembler::const_iterator it = Asm.begin(),
839 ie = Asm.end(); it != ie; ++it) {
840 const MCSectionData &SD = *it;
841
842 // Get the size of the section in the output file (including padding).
843 uint64_t Size = Layout.getSectionFileSize(&SD);
844 SectionDataSize += Size;
845 }
846
847 // Write out the ELF header ...
848 WriteHeader(SectionDataSize, NumSections);
849 FileOff = Is64Bit ? sizeof(ELF::Elf64_Ehdr) : sizeof(ELF::Elf32_Ehdr);
850
851 // ... then all of the sections ...
852 DenseMap<const MCSection*, uint64_t> SectionOffsetMap;
853
854 DenseMap<const MCSection*, uint8_t> SectionIndexMap;
855
856 unsigned Index = 1;
857 for (MCAssembler::const_iterator it = Asm.begin(),
858 ie = Asm.end(); it != ie; ++it) {
859 // Remember the offset into the file for this section.
860 SectionOffsetMap[&it->getSection()] = FileOff;
861
862 SectionIndexMap[&it->getSection()] = Index++;
863
864 const MCSectionData &SD = *it;
865 FileOff += Layout.getSectionFileSize(&SD);
866
867 Asm.WriteSectionData(it, Layout, Writer);
868 }
869
870 // ... and then the section header table.
871 // Should we align the section header table?
872 //
873 // Null section first.
874 WriteSecHdrEntry(0, 0, 0, 0, 0, 0, 0, 0, 0, 0);
875
876 for (MCAssembler::const_iterator it = Asm.begin(),
877 ie = Asm.end(); it != ie; ++it) {
878 const MCSectionData &SD = *it;
879 const MCSectionELF &Section =
880 static_cast<const MCSectionELF&>(SD.getSection());
881
882 uint64_t sh_link = 0;
883 uint64_t sh_info = 0;
884
885 switch(Section.getType()) {
886 case ELF::SHT_DYNAMIC:
887 sh_link = SectionStringTableIndex[&it->getSection()];
888 sh_info = 0;
889 break;
890
891 case ELF::SHT_REL:
892 case ELF::SHT_RELA: {
893 const MCSection *SymtabSection;
894 const MCSection *InfoSection;
895
896 SymtabSection = Asm.getContext().getELFSection(".symtab", ELF::SHT_SYMTAB, 0,
897 SectionKind::getReadOnly(),
898 false);
899 sh_link = SectionIndexMap[SymtabSection];
900
901 // Remove ".rel" and ".rela" prefixes.
902 unsigned SecNameLen = (Section.getType() == ELF::SHT_REL) ? 4 : 5;
903 StringRef SectionName = Section.getSectionName().substr(SecNameLen);
904
905 InfoSection = Asm.getContext().getELFSection(SectionName,
906 ELF::SHT_PROGBITS, 0,
907 SectionKind::getReadOnly(),
908 false);
909 sh_info = SectionIndexMap[InfoSection];
910 break;
911 }
912
913 case ELF::SHT_SYMTAB:
914 case ELF::SHT_DYNSYM:
915 sh_link = StringTableIndex;
916 sh_info = LastLocalSymbolIndex;
917 break;
918
919 case ELF::SHT_PROGBITS:
920 case ELF::SHT_STRTAB:
921 case ELF::SHT_NOBITS:
922 case ELF::SHT_NULL:
923 // Nothing to do.
924 break;
925
926 case ELF::SHT_HASH:
927 case ELF::SHT_GROUP:
928 case ELF::SHT_SYMTAB_SHNDX:
929 default:
930 assert(0 && "FIXME: sh_type value not supported!");
931 break;
932 }
933
934 WriteSecHdrEntry(SectionStringTableIndex[&it->getSection()],
935 Section.getType(), Section.getFlags(),
936 Layout.getSectionAddress(&SD),
937 SectionOffsetMap.lookup(&SD.getSection()),
938 Layout.getSectionSize(&SD), sh_link,
939 sh_info, SD.getAlignment(),
940 Section.getEntrySize());
941 }
942}
943
944ELFObjectWriter::ELFObjectWriter(raw_ostream &OS,
945 bool Is64Bit,
946 bool IsLittleEndian,
947 bool HasRelocationAddend)
948 : MCObjectWriter(OS, IsLittleEndian)
949{
950 Impl = new ELFObjectWriterImpl(this, Is64Bit, HasRelocationAddend);
951}
952
953ELFObjectWriter::~ELFObjectWriter() {
954 delete (ELFObjectWriterImpl*) Impl;
955}
956
957void ELFObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm) {
958 ((ELFObjectWriterImpl*) Impl)->ExecutePostLayoutBinding(Asm);
959}
960
961void ELFObjectWriter::RecordRelocation(const MCAssembler &Asm,
962 const MCAsmLayout &Layout,
963 const MCFragment *Fragment,
964 const MCFixup &Fixup, MCValue Target,
965 uint64_t &FixedValue) {
966 ((ELFObjectWriterImpl*) Impl)->RecordRelocation(Asm, Layout, Fragment, Fixup,
967 Target, FixedValue);
968}
969
970void ELFObjectWriter::WriteObject(const MCAssembler &Asm,
971 const MCAsmLayout &Layout) {
972 ((ELFObjectWriterImpl*) Impl)->WriteObject(Asm, Layout);
973}
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