RuntimeDyldELF.cpp revision 244628 
1//===-- RuntimeDyldELF.cpp - Run-time dynamic linker for MC-JIT -*- C++ -*-===//
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// Implementation of ELF support for the MC-JIT runtime dynamic linker.
11//
12//===----------------------------------------------------------------------===//
13
14#define DEBUG_TYPE "dyld"
15#include "RuntimeDyldELF.h"
16#include "JITRegistrar.h"
17#include "ObjectImageCommon.h"
18#include "llvm/ADT/OwningPtr.h"
19#include "llvm/ADT/StringRef.h"
20#include "llvm/ADT/STLExtras.h"
21#include "llvm/ADT/IntervalMap.h"
22#include "llvm/Object/ObjectFile.h"
23#include "llvm/ExecutionEngine/ObjectImage.h"
24#include "llvm/ExecutionEngine/ObjectBuffer.h"
25#include "llvm/Support/ELF.h"
26#include "llvm/ADT/Triple.h"
27#include "llvm/Object/ELF.h"
28using namespace llvm;
29using namespace llvm::object;
30
31namespace {
32
33static inline
34error_code check(error_code Err) {
35  if (Err) {
36    report_fatal_error(Err.message());
37  }
38  return Err;
39}
40
41template<support::endianness target_endianness, bool is64Bits>
42class DyldELFObject : public ELFObjectFile<target_endianness, is64Bits> {
43  LLVM_ELF_IMPORT_TYPES(target_endianness, is64Bits)
44
45  typedef Elf_Shdr_Impl<target_endianness, is64Bits> Elf_Shdr;
46  typedef Elf_Sym_Impl<target_endianness, is64Bits> Elf_Sym;
47  typedef Elf_Rel_Impl<target_endianness, is64Bits, false> Elf_Rel;
48  typedef Elf_Rel_Impl<target_endianness, is64Bits, true> Elf_Rela;
49
50  typedef Elf_Ehdr_Impl<target_endianness, is64Bits> Elf_Ehdr;
51
52  typedef typename ELFDataTypeTypedefHelper<
53          target_endianness, is64Bits>::value_type addr_type;
54
55public:
56  DyldELFObject(MemoryBuffer *Wrapper, error_code &ec);
57
58  void updateSectionAddress(const SectionRef &Sec, uint64_t Addr);
59  void updateSymbolAddress(const SymbolRef &Sym, uint64_t Addr);
60
61  // Methods for type inquiry through isa, cast and dyn_cast
62  static inline bool classof(const Binary *v) {
63    return (isa<ELFObjectFile<target_endianness, is64Bits> >(v)
64            && classof(cast<ELFObjectFile<target_endianness, is64Bits> >(v)));
65  }
66  static inline bool classof(
67      const ELFObjectFile<target_endianness, is64Bits> *v) {
68    return v->isDyldType();
69  }
70};
71
72template<support::endianness target_endianness, bool is64Bits>
73class ELFObjectImage : public ObjectImageCommon {
74  protected:
75    DyldELFObject<target_endianness, is64Bits> *DyldObj;
76    bool Registered;
77
78  public:
79    ELFObjectImage(ObjectBuffer *Input,
80                   DyldELFObject<target_endianness, is64Bits> *Obj)
81    : ObjectImageCommon(Input, Obj),
82      DyldObj(Obj),
83      Registered(false) {}
84
85    virtual ~ELFObjectImage() {
86      if (Registered)
87        deregisterWithDebugger();
88    }
89
90    // Subclasses can override these methods to update the image with loaded
91    // addresses for sections and common symbols
92    virtual void updateSectionAddress(const SectionRef &Sec, uint64_t Addr)
93    {
94      DyldObj->updateSectionAddress(Sec, Addr);
95    }
96
97    virtual void updateSymbolAddress(const SymbolRef &Sym, uint64_t Addr)
98    {
99      DyldObj->updateSymbolAddress(Sym, Addr);
100    }
101
102    virtual void registerWithDebugger()
103    {
104      JITRegistrar::getGDBRegistrar().registerObject(*Buffer);
105      Registered = true;
106    }
107    virtual void deregisterWithDebugger()
108    {
109      JITRegistrar::getGDBRegistrar().deregisterObject(*Buffer);
110    }
111};
112
113// The MemoryBuffer passed into this constructor is just a wrapper around the
114// actual memory.  Ultimately, the Binary parent class will take ownership of
115// this MemoryBuffer object but not the underlying memory.
116template<support::endianness target_endianness, bool is64Bits>
117DyldELFObject<target_endianness, is64Bits>::DyldELFObject(MemoryBuffer *Wrapper,
118                                                          error_code &ec)
119  : ELFObjectFile<target_endianness, is64Bits>(Wrapper, ec) {
120  this->isDyldELFObject = true;
121}
122
123template<support::endianness target_endianness, bool is64Bits>
124void DyldELFObject<target_endianness, is64Bits>::updateSectionAddress(
125                                                       const SectionRef &Sec,
126                                                       uint64_t Addr) {
127  DataRefImpl ShdrRef = Sec.getRawDataRefImpl();
128  Elf_Shdr *shdr = const_cast<Elf_Shdr*>(
129                          reinterpret_cast<const Elf_Shdr *>(ShdrRef.p));
130
131  // This assumes the address passed in matches the target address bitness
132  // The template-based type cast handles everything else.
133  shdr->sh_addr = static_cast<addr_type>(Addr);
134}
135
136template<support::endianness target_endianness, bool is64Bits>
137void DyldELFObject<target_endianness, is64Bits>::updateSymbolAddress(
138                                                       const SymbolRef &SymRef,
139                                                       uint64_t Addr) {
140
141  Elf_Sym *sym = const_cast<Elf_Sym*>(
142                                 ELFObjectFile<target_endianness, is64Bits>::
143                                   getSymbol(SymRef.getRawDataRefImpl()));
144
145  // This assumes the address passed in matches the target address bitness
146  // The template-based type cast handles everything else.
147  sym->st_value = static_cast<addr_type>(Addr);
148}
149
150} // namespace
151
152
153namespace llvm {
154
155ObjectImage *RuntimeDyldELF::createObjectImage(ObjectBuffer *Buffer) {
156  if (Buffer->getBufferSize() < ELF::EI_NIDENT)
157    llvm_unreachable("Unexpected ELF object size");
158  std::pair<unsigned char, unsigned char> Ident = std::make_pair(
159                         (uint8_t)Buffer->getBufferStart()[ELF::EI_CLASS],
160                         (uint8_t)Buffer->getBufferStart()[ELF::EI_DATA]);
161  error_code ec;
162
163  if (Ident.first == ELF::ELFCLASS32 && Ident.second == ELF::ELFDATA2LSB) {
164    DyldELFObject<support::little, false> *Obj =
165           new DyldELFObject<support::little, false>(Buffer->getMemBuffer(), ec);
166    return new ELFObjectImage<support::little, false>(Buffer, Obj);
167  }
168  else if (Ident.first == ELF::ELFCLASS32 && Ident.second == ELF::ELFDATA2MSB) {
169    DyldELFObject<support::big, false> *Obj =
170           new DyldELFObject<support::big, false>(Buffer->getMemBuffer(), ec);
171    return new ELFObjectImage<support::big, false>(Buffer, Obj);
172  }
173  else if (Ident.first == ELF::ELFCLASS64 && Ident.second == ELF::ELFDATA2MSB) {
174    DyldELFObject<support::big, true> *Obj =
175           new DyldELFObject<support::big, true>(Buffer->getMemBuffer(), ec);
176    return new ELFObjectImage<support::big, true>(Buffer, Obj);
177  }
178  else if (Ident.first == ELF::ELFCLASS64 && Ident.second == ELF::ELFDATA2LSB) {
179    DyldELFObject<support::little, true> *Obj =
180           new DyldELFObject<support::little, true>(Buffer->getMemBuffer(), ec);
181    return new ELFObjectImage<support::little, true>(Buffer, Obj);
182  }
183  else
184    llvm_unreachable("Unexpected ELF format");
185}
186
187RuntimeDyldELF::~RuntimeDyldELF() {
188}
189
190void RuntimeDyldELF::resolveX86_64Relocation(const SectionEntry &Section,
191                                             uint64_t Offset,
192                                             uint64_t Value,
193                                             uint32_t Type,
194                                             int64_t Addend) {
195  switch (Type) {
196  default:
197    llvm_unreachable("Relocation type not implemented yet!");
198  break;
199  case ELF::R_X86_64_64: {
200    uint64_t *Target = reinterpret_cast<uint64_t*>(Section.Address + Offset);
201    *Target = Value + Addend;
202    DEBUG(dbgs() << "Writing " << format("%p", (Value + Addend))
203                 << " at " << format("%p\n",Target));
204    break;
205  }
206  case ELF::R_X86_64_32:
207  case ELF::R_X86_64_32S: {
208    Value += Addend;
209    assert((Type == ELF::R_X86_64_32 && (Value <= UINT32_MAX)) ||
210           (Type == ELF::R_X86_64_32S &&
211             ((int64_t)Value <= INT32_MAX && (int64_t)Value >= INT32_MIN)));
212    uint32_t TruncatedAddr = (Value & 0xFFFFFFFF);
213    uint32_t *Target = reinterpret_cast<uint32_t*>(Section.Address + Offset);
214    *Target = TruncatedAddr;
215    DEBUG(dbgs() << "Writing " << format("%p", TruncatedAddr)
216                 << " at " << format("%p\n",Target));
217    break;
218  }
219  case ELF::R_X86_64_PC32: {
220    // Get the placeholder value from the generated object since
221    // a previous relocation attempt may have overwritten the loaded version
222    uint32_t *Placeholder = reinterpret_cast<uint32_t*>(Section.ObjAddress
223                                                                   + Offset);
224    uint32_t *Target = reinterpret_cast<uint32_t*>(Section.Address + Offset);
225    uint64_t  FinalAddress = Section.LoadAddress + Offset;
226    int64_t RealOffset = *Placeholder + Value + Addend - FinalAddress;
227    assert(RealOffset <= INT32_MAX && RealOffset >= INT32_MIN);
228    int32_t TruncOffset = (RealOffset & 0xFFFFFFFF);
229    *Target = TruncOffset;
230    break;
231  }
232  }
233}
234
235void RuntimeDyldELF::resolveX86Relocation(const SectionEntry &Section,
236                                          uint64_t Offset,
237                                          uint32_t Value,
238                                          uint32_t Type,
239                                          int32_t Addend) {
240  switch (Type) {
241  case ELF::R_386_32: {
242    // Get the placeholder value from the generated object since
243    // a previous relocation attempt may have overwritten the loaded version
244    uint32_t *Placeholder = reinterpret_cast<uint32_t*>(Section.ObjAddress
245                                                                   + Offset);
246    uint32_t *Target = reinterpret_cast<uint32_t*>(Section.Address + Offset);
247    *Target = *Placeholder + Value + Addend;
248    break;
249  }
250  case ELF::R_386_PC32: {
251    // Get the placeholder value from the generated object since
252    // a previous relocation attempt may have overwritten the loaded version
253    uint32_t *Placeholder = reinterpret_cast<uint32_t*>(Section.ObjAddress
254                                                                   + Offset);
255    uint32_t *Target = reinterpret_cast<uint32_t*>(Section.Address + Offset);
256    uint32_t  FinalAddress = ((Section.LoadAddress + Offset) & 0xFFFFFFFF);
257    uint32_t RealOffset = *Placeholder + Value + Addend - FinalAddress;
258    *Target = RealOffset;
259    break;
260    }
261    default:
262      // There are other relocation types, but it appears these are the
263      // only ones currently used by the LLVM ELF object writer
264      llvm_unreachable("Relocation type not implemented yet!");
265      break;
266  }
267}
268
269void RuntimeDyldELF::resolveARMRelocation(const SectionEntry &Section,
270                                          uint64_t Offset,
271                                          uint32_t Value,
272                                          uint32_t Type,
273                                          int32_t Addend) {
274  // TODO: Add Thumb relocations.
275  uint32_t* TargetPtr = (uint32_t*)(Section.Address + Offset);
276  uint32_t FinalAddress = ((Section.LoadAddress + Offset) & 0xFFFFFFFF);
277  Value += Addend;
278
279  DEBUG(dbgs() << "resolveARMRelocation, LocalAddress: "
280               << Section.Address + Offset
281               << " FinalAddress: " << format("%p",FinalAddress)
282               << " Value: " << format("%x",Value)
283               << " Type: " << format("%x",Type)
284               << " Addend: " << format("%x",Addend)
285               << "\n");
286
287  switch(Type) {
288  default:
289    llvm_unreachable("Not implemented relocation type!");
290
291  // Write a 32bit value to relocation address, taking into account the
292  // implicit addend encoded in the target.
293  case ELF::R_ARM_ABS32 :
294    *TargetPtr += Value;
295    break;
296
297  // Write first 16 bit of 32 bit value to the mov instruction.
298  // Last 4 bit should be shifted.
299  case ELF::R_ARM_MOVW_ABS_NC :
300    // We are not expecting any other addend in the relocation address.
301    // Using 0x000F0FFF because MOVW has its 16 bit immediate split into 2
302    // non-contiguous fields.
303    assert((*TargetPtr & 0x000F0FFF) == 0);
304    Value = Value & 0xFFFF;
305    *TargetPtr |= Value & 0xFFF;
306    *TargetPtr |= ((Value >> 12) & 0xF) << 16;
307    break;
308
309  // Write last 16 bit of 32 bit value to the mov instruction.
310  // Last 4 bit should be shifted.
311  case ELF::R_ARM_MOVT_ABS :
312    // We are not expecting any other addend in the relocation address.
313    // Use 0x000F0FFF for the same reason as R_ARM_MOVW_ABS_NC.
314    assert((*TargetPtr & 0x000F0FFF) == 0);
315    Value = (Value >> 16) & 0xFFFF;
316    *TargetPtr |= Value & 0xFFF;
317    *TargetPtr |= ((Value >> 12) & 0xF) << 16;
318    break;
319
320  // Write 24 bit relative value to the branch instruction.
321  case ELF::R_ARM_PC24 :    // Fall through.
322  case ELF::R_ARM_CALL :    // Fall through.
323  case ELF::R_ARM_JUMP24 :
324    int32_t RelValue = static_cast<int32_t>(Value - FinalAddress - 8);
325    RelValue = (RelValue & 0x03FFFFFC) >> 2;
326    *TargetPtr &= 0xFF000000;
327    *TargetPtr |= RelValue;
328    break;
329  }
330}
331
332void RuntimeDyldELF::resolveMIPSRelocation(const SectionEntry &Section,
333                                           uint64_t Offset,
334                                           uint32_t Value,
335                                           uint32_t Type,
336                                           int32_t Addend) {
337  uint32_t* TargetPtr = (uint32_t*)(Section.Address + Offset);
338  Value += Addend;
339
340  DEBUG(dbgs() << "resolveMipselocation, LocalAddress: "
341               << Section.Address + Offset
342               << " FinalAddress: "
343               << format("%p",Section.LoadAddress + Offset)
344               << " Value: " << format("%x",Value)
345               << " Type: " << format("%x",Type)
346               << " Addend: " << format("%x",Addend)
347               << "\n");
348
349  switch(Type) {
350  default:
351    llvm_unreachable("Not implemented relocation type!");
352    break;
353  case ELF::R_MIPS_32:
354    *TargetPtr = Value + (*TargetPtr);
355    break;
356  case ELF::R_MIPS_26:
357    *TargetPtr = ((*TargetPtr) & 0xfc000000) | (( Value & 0x0fffffff) >> 2);
358    break;
359  case ELF::R_MIPS_HI16:
360    // Get the higher 16-bits. Also add 1 if bit 15 is 1.
361    Value += ((*TargetPtr) & 0x0000ffff) << 16;
362    *TargetPtr = ((*TargetPtr) & 0xffff0000) |
363                 (((Value + 0x8000) >> 16) & 0xffff);
364    break;
365   case ELF::R_MIPS_LO16:
366    Value += ((*TargetPtr) & 0x0000ffff);
367    *TargetPtr = ((*TargetPtr) & 0xffff0000) | (Value & 0xffff);
368    break;
369   }
370}
371
372// Return the .TOC. section address to R_PPC64_TOC relocations.
373uint64_t RuntimeDyldELF::findPPC64TOC() const {
374  // The TOC consists of sections .got, .toc, .tocbss, .plt in that
375  // order. The TOC starts where the first of these sections starts.
376  SectionList::const_iterator it = Sections.begin();
377  SectionList::const_iterator ite = Sections.end();
378  for (; it != ite; ++it) {
379    if (it->Name == ".got" ||
380        it->Name == ".toc" ||
381        it->Name == ".tocbss" ||
382        it->Name == ".plt")
383      break;
384  }
385  if (it == ite) {
386    // This may happen for
387    // * references to TOC base base (sym@toc, .odp relocation) without
388    // a .toc directive.
389    // In this case just use the first section (which is usually
390    // the .odp) since the code won't reference the .toc base
391    // directly.
392    it = Sections.begin();
393  }
394  assert (it != ite);
395  // Per the ppc64-elf-linux ABI, The TOC base is TOC value plus 0x8000
396  // thus permitting a full 64 Kbytes segment.
397  return it->LoadAddress + 0x8000;
398}
399
400// Returns the sections and offset associated with the ODP entry referenced
401// by Symbol.
402void RuntimeDyldELF::findOPDEntrySection(ObjectImage &Obj,
403                                         ObjSectionToIDMap &LocalSections,
404                                         RelocationValueRef &Rel) {
405  // Get the ELF symbol value (st_value) to compare with Relocation offset in
406  // .opd entries
407
408  error_code err;
409  for (section_iterator si = Obj.begin_sections(),
410     se = Obj.end_sections(); si != se; si.increment(err)) {
411    StringRef SectionName;
412    check(si->getName(SectionName));
413    if (SectionName != ".opd")
414      continue;
415
416    for (relocation_iterator i = si->begin_relocations(),
417         e = si->end_relocations(); i != e;) {
418      check(err);
419
420      // The R_PPC64_ADDR64 relocation indicates the first field
421      // of a .opd entry
422      uint64_t TypeFunc;
423      check(i->getType(TypeFunc));
424      if (TypeFunc != ELF::R_PPC64_ADDR64) {
425        i.increment(err);
426        continue;
427      }
428
429      SymbolRef TargetSymbol;
430      uint64_t TargetSymbolOffset;
431      int64_t TargetAdditionalInfo;
432      check(i->getSymbol(TargetSymbol));
433      check(i->getOffset(TargetSymbolOffset));
434      check(i->getAdditionalInfo(TargetAdditionalInfo));
435
436      i = i.increment(err);
437      if (i == e)
438        break;
439      check(err);
440
441      // Just check if following relocation is a R_PPC64_TOC
442      uint64_t TypeTOC;
443      check(i->getType(TypeTOC));
444      if (TypeTOC != ELF::R_PPC64_TOC)
445        continue;
446
447      // Finally compares the Symbol value and the target symbol offset
448      // to check if this .opd entry refers to the symbol the relocation
449      // points to.
450      if (Rel.Addend != (intptr_t)TargetSymbolOffset)
451        continue;
452
453      section_iterator tsi(Obj.end_sections());
454      check(TargetSymbol.getSection(tsi));
455      Rel.SectionID = findOrEmitSection(Obj, (*tsi), true, LocalSections);
456      Rel.Addend = (intptr_t)TargetAdditionalInfo;
457      return;
458    }
459  }
460  llvm_unreachable("Attempting to get address of ODP entry!");
461}
462
463// Relocation masks following the #lo(value), #hi(value), #higher(value),
464// and #highest(value) macros defined in section 4.5.1. Relocation Types
465// in PPC-elf64abi document.
466//
467static inline
468uint16_t applyPPClo (uint64_t value)
469{
470  return value & 0xffff;
471}
472
473static inline
474uint16_t applyPPChi (uint64_t value)
475{
476  return (value >> 16) & 0xffff;
477}
478
479static inline
480uint16_t applyPPChigher (uint64_t value)
481{
482  return (value >> 32) & 0xffff;
483}
484
485static inline
486uint16_t applyPPChighest (uint64_t value)
487{
488  return (value >> 48) & 0xffff;
489}
490
491void RuntimeDyldELF::resolvePPC64Relocation(const SectionEntry &Section,
492                                            uint64_t Offset,
493                                            uint64_t Value,
494                                            uint32_t Type,
495                                            int64_t Addend) {
496  uint8_t* LocalAddress = Section.Address + Offset;
497  switch (Type) {
498  default:
499    llvm_unreachable("Relocation type not implemented yet!");
500  break;
501  case ELF::R_PPC64_ADDR16_LO :
502    writeInt16BE(LocalAddress, applyPPClo (Value + Addend));
503    break;
504  case ELF::R_PPC64_ADDR16_HI :
505    writeInt16BE(LocalAddress, applyPPChi (Value + Addend));
506    break;
507  case ELF::R_PPC64_ADDR16_HIGHER :
508    writeInt16BE(LocalAddress, applyPPChigher (Value + Addend));
509    break;
510  case ELF::R_PPC64_ADDR16_HIGHEST :
511    writeInt16BE(LocalAddress, applyPPChighest (Value + Addend));
512    break;
513  case ELF::R_PPC64_ADDR14 : {
514    assert(((Value + Addend) & 3) == 0);
515    // Preserve the AA/LK bits in the branch instruction
516    uint8_t aalk = *(LocalAddress+3);
517    writeInt16BE(LocalAddress + 2, (aalk & 3) | ((Value + Addend) & 0xfffc));
518  } break;
519  case ELF::R_PPC64_REL24 : {
520    uint64_t FinalAddress = (Section.LoadAddress + Offset);
521    int32_t delta = static_cast<int32_t>(Value - FinalAddress + Addend);
522    if (SignExtend32<24>(delta) != delta)
523      llvm_unreachable("Relocation R_PPC64_REL24 overflow");
524    // Generates a 'bl <address>' instruction
525    writeInt32BE(LocalAddress, 0x48000001 | (delta & 0x03FFFFFC));
526  } break;
527  case ELF::R_PPC64_ADDR64 :
528    writeInt64BE(LocalAddress, Value + Addend);
529    break;
530  case ELF::R_PPC64_TOC :
531    writeInt64BE(LocalAddress, findPPC64TOC());
532    break;
533  case ELF::R_PPC64_TOC16 : {
534    uint64_t TOCStart = findPPC64TOC();
535    Value = applyPPClo((Value + Addend) - TOCStart);
536    writeInt16BE(LocalAddress, applyPPClo(Value));
537  } break;
538  case ELF::R_PPC64_TOC16_DS : {
539    uint64_t TOCStart = findPPC64TOC();
540    Value = ((Value + Addend) - TOCStart);
541    writeInt16BE(LocalAddress, applyPPClo(Value));
542  } break;
543  }
544}
545
546
547void RuntimeDyldELF::resolveRelocation(const SectionEntry &Section,
548                                       uint64_t Offset,
549                                       uint64_t Value,
550                                       uint32_t Type,
551                                       int64_t Addend) {
552  switch (Arch) {
553  case Triple::x86_64:
554    resolveX86_64Relocation(Section, Offset, Value, Type, Addend);
555    break;
556  case Triple::x86:
557    resolveX86Relocation(Section, Offset,
558                         (uint32_t)(Value & 0xffffffffL), Type,
559                         (uint32_t)(Addend & 0xffffffffL));
560    break;
561  case Triple::arm:    // Fall through.
562  case Triple::thumb:
563    resolveARMRelocation(Section, Offset,
564                         (uint32_t)(Value & 0xffffffffL), Type,
565                         (uint32_t)(Addend & 0xffffffffL));
566    break;
567  case Triple::mips:    // Fall through.
568  case Triple::mipsel:
569    resolveMIPSRelocation(Section, Offset,
570                          (uint32_t)(Value & 0xffffffffL), Type,
571                          (uint32_t)(Addend & 0xffffffffL));
572    break;
573  case Triple::ppc64:
574    resolvePPC64Relocation(Section, Offset, Value, Type, Addend);
575    break;
576  default: llvm_unreachable("Unsupported CPU type!");
577  }
578}
579
580void RuntimeDyldELF::processRelocationRef(const ObjRelocationInfo &Rel,
581                                          ObjectImage &Obj,
582                                          ObjSectionToIDMap &ObjSectionToID,
583                                          const SymbolTableMap &Symbols,
584                                          StubMap &Stubs) {
585
586  uint32_t RelType = (uint32_t)(Rel.Type & 0xffffffffL);
587  intptr_t Addend = (intptr_t)Rel.AdditionalInfo;
588  const SymbolRef &Symbol = Rel.Symbol;
589
590  // Obtain the symbol name which is referenced in the relocation
591  StringRef TargetName;
592  Symbol.getName(TargetName);
593  DEBUG(dbgs() << "\t\tRelType: " << RelType
594               << " Addend: " << Addend
595               << " TargetName: " << TargetName
596               << "\n");
597  RelocationValueRef Value;
598  // First search for the symbol in the local symbol table
599  SymbolTableMap::const_iterator lsi = Symbols.find(TargetName.data());
600  SymbolRef::Type SymType;
601  Symbol.getType(SymType);
602  if (lsi != Symbols.end()) {
603    Value.SectionID = lsi->second.first;
604    Value.Addend = lsi->second.second;
605  } else {
606    // Search for the symbol in the global symbol table
607    SymbolTableMap::const_iterator gsi =
608        GlobalSymbolTable.find(TargetName.data());
609    if (gsi != GlobalSymbolTable.end()) {
610      Value.SectionID = gsi->second.first;
611      Value.Addend = gsi->second.second;
612    } else {
613      switch (SymType) {
614        case SymbolRef::ST_Debug: {
615          // TODO: Now ELF SymbolRef::ST_Debug = STT_SECTION, it's not obviously
616          // and can be changed by another developers. Maybe best way is add
617          // a new symbol type ST_Section to SymbolRef and use it.
618          section_iterator si(Obj.end_sections());
619          Symbol.getSection(si);
620          if (si == Obj.end_sections())
621            llvm_unreachable("Symbol section not found, bad object file format!");
622          DEBUG(dbgs() << "\t\tThis is section symbol\n");
623          // Default to 'true' in case isText fails (though it never does).
624          bool isCode = true;
625          si->isText(isCode);
626          Value.SectionID = findOrEmitSection(Obj,
627                                              (*si),
628                                              isCode,
629                                              ObjSectionToID);
630          Value.Addend = Addend;
631          break;
632        }
633        case SymbolRef::ST_Unknown: {
634          Value.SymbolName = TargetName.data();
635          Value.Addend = Addend;
636          break;
637        }
638        default:
639          llvm_unreachable("Unresolved symbol type!");
640          break;
641      }
642    }
643  }
644  DEBUG(dbgs() << "\t\tRel.SectionID: " << Rel.SectionID
645               << " Rel.Offset: " << Rel.Offset
646               << "\n");
647  if (Arch == Triple::arm &&
648      (RelType == ELF::R_ARM_PC24 ||
649       RelType == ELF::R_ARM_CALL ||
650       RelType == ELF::R_ARM_JUMP24)) {
651    // This is an ARM branch relocation, need to use a stub function.
652    DEBUG(dbgs() << "\t\tThis is an ARM branch relocation.");
653    SectionEntry &Section = Sections[Rel.SectionID];
654
655    // Look for an existing stub.
656    StubMap::const_iterator i = Stubs.find(Value);
657    if (i != Stubs.end()) {
658        resolveRelocation(Section, Rel.Offset,
659                          (uint64_t)Section.Address + i->second, RelType, 0);
660      DEBUG(dbgs() << " Stub function found\n");
661    } else {
662      // Create a new stub function.
663      DEBUG(dbgs() << " Create a new stub function\n");
664      Stubs[Value] = Section.StubOffset;
665      uint8_t *StubTargetAddr = createStubFunction(Section.Address +
666                                                   Section.StubOffset);
667      RelocationEntry RE(Rel.SectionID, StubTargetAddr - Section.Address,
668                         ELF::R_ARM_ABS32, Value.Addend);
669      if (Value.SymbolName)
670        addRelocationForSymbol(RE, Value.SymbolName);
671      else
672        addRelocationForSection(RE, Value.SectionID);
673
674      resolveRelocation(Section, Rel.Offset,
675                        (uint64_t)Section.Address + Section.StubOffset,
676                        RelType, 0);
677      Section.StubOffset += getMaxStubSize();
678    }
679  } else if ((Arch == Triple::mipsel || Arch == Triple::mips) &&
680             RelType == ELF::R_MIPS_26) {
681    // This is an Mips branch relocation, need to use a stub function.
682    DEBUG(dbgs() << "\t\tThis is a Mips branch relocation.");
683    SectionEntry &Section = Sections[Rel.SectionID];
684    uint8_t *Target = Section.Address + Rel.Offset;
685    uint32_t *TargetAddress = (uint32_t *)Target;
686
687    // Extract the addend from the instruction.
688    uint32_t Addend = ((*TargetAddress) & 0x03ffffff) << 2;
689
690    Value.Addend += Addend;
691
692    //  Look up for existing stub.
693    StubMap::const_iterator i = Stubs.find(Value);
694    if (i != Stubs.end()) {
695      resolveRelocation(Section, Rel.Offset,
696                        (uint64_t)Section.Address + i->second, RelType, 0);
697      DEBUG(dbgs() << " Stub function found\n");
698    } else {
699      // Create a new stub function.
700      DEBUG(dbgs() << " Create a new stub function\n");
701      Stubs[Value] = Section.StubOffset;
702      uint8_t *StubTargetAddr = createStubFunction(Section.Address +
703                                                   Section.StubOffset);
704
705      // Creating Hi and Lo relocations for the filled stub instructions.
706      RelocationEntry REHi(Rel.SectionID,
707                           StubTargetAddr - Section.Address,
708                           ELF::R_MIPS_HI16, Value.Addend);
709      RelocationEntry RELo(Rel.SectionID,
710                           StubTargetAddr - Section.Address + 4,
711                           ELF::R_MIPS_LO16, Value.Addend);
712
713      if (Value.SymbolName) {
714        addRelocationForSymbol(REHi, Value.SymbolName);
715        addRelocationForSymbol(RELo, Value.SymbolName);
716      } else {
717        addRelocationForSection(REHi, Value.SectionID);
718        addRelocationForSection(RELo, Value.SectionID);
719      }
720
721      resolveRelocation(Section, Rel.Offset,
722                        (uint64_t)Section.Address + Section.StubOffset,
723                        RelType, 0);
724      Section.StubOffset += getMaxStubSize();
725    }
726  } else if (Arch == Triple::ppc64) {
727    if (RelType == ELF::R_PPC64_REL24) {
728      // A PPC branch relocation will need a stub function if the target is
729      // an external symbol (Symbol::ST_Unknown) or if the target address
730      // is not within the signed 24-bits branch address.
731      SectionEntry &Section = Sections[Rel.SectionID];
732      uint8_t *Target = Section.Address + Rel.Offset;
733      bool RangeOverflow = false;
734      if (SymType != SymbolRef::ST_Unknown) {
735        // A function call may points to the .opd entry, so the final symbol value
736        // in calculated based in the relocation values in .opd section.
737        findOPDEntrySection(Obj, ObjSectionToID, Value);
738        uint8_t *RelocTarget = Sections[Value.SectionID].Address + Value.Addend;
739        int32_t delta = static_cast<int32_t>(Target - RelocTarget);
740        // If it is within 24-bits branch range, just set the branch target
741        if (SignExtend32<24>(delta) == delta) {
742          RelocationEntry RE(Rel.SectionID, Rel.Offset, RelType, Value.Addend);
743          if (Value.SymbolName)
744            addRelocationForSymbol(RE, Value.SymbolName);
745          else
746            addRelocationForSection(RE, Value.SectionID);
747        } else {
748          RangeOverflow = true;
749        }
750      }
751      if (SymType == SymbolRef::ST_Unknown || RangeOverflow == true) {
752        // It is an external symbol (SymbolRef::ST_Unknown) or within a range
753        // larger than 24-bits.
754        StubMap::const_iterator i = Stubs.find(Value);
755        if (i != Stubs.end()) {
756          // Symbol function stub already created, just relocate to it
757          resolveRelocation(Section, Rel.Offset,
758                            (uint64_t)Section.Address + i->second, RelType, 0);
759          DEBUG(dbgs() << " Stub function found\n");
760        } else {
761          // Create a new stub function.
762          DEBUG(dbgs() << " Create a new stub function\n");
763          Stubs[Value] = Section.StubOffset;
764          uint8_t *StubTargetAddr = createStubFunction(Section.Address +
765                                                       Section.StubOffset);
766          RelocationEntry RE(Rel.SectionID, StubTargetAddr - Section.Address,
767                             ELF::R_PPC64_ADDR64, Value.Addend);
768
769          // Generates the 64-bits address loads as exemplified in section
770          // 4.5.1 in PPC64 ELF ABI.
771          RelocationEntry REhst(Rel.SectionID,
772                                StubTargetAddr - Section.Address + 2,
773                                ELF::R_PPC64_ADDR16_HIGHEST, Value.Addend);
774          RelocationEntry REhr(Rel.SectionID,
775                               StubTargetAddr - Section.Address + 6,
776                               ELF::R_PPC64_ADDR16_HIGHER, Value.Addend);
777          RelocationEntry REh(Rel.SectionID,
778                              StubTargetAddr - Section.Address + 14,
779                              ELF::R_PPC64_ADDR16_HI, Value.Addend);
780          RelocationEntry REl(Rel.SectionID,
781                              StubTargetAddr - Section.Address + 18,
782                              ELF::R_PPC64_ADDR16_LO, Value.Addend);
783
784          if (Value.SymbolName) {
785            addRelocationForSymbol(REhst, Value.SymbolName);
786            addRelocationForSymbol(REhr,  Value.SymbolName);
787            addRelocationForSymbol(REh,   Value.SymbolName);
788            addRelocationForSymbol(REl,   Value.SymbolName);
789          } else {
790            addRelocationForSection(REhst, Value.SectionID);
791            addRelocationForSection(REhr,  Value.SectionID);
792            addRelocationForSection(REh,   Value.SectionID);
793            addRelocationForSection(REl,   Value.SectionID);
794          }
795
796          resolveRelocation(Section, Rel.Offset,
797                            (uint64_t)Section.Address + Section.StubOffset,
798                            RelType, 0);
799          if (SymType == SymbolRef::ST_Unknown)
800            // Restore the TOC for external calls
801            writeInt32BE(Target+4, 0xE8410028); // ld r2,40(r1)
802          Section.StubOffset += getMaxStubSize();
803        }
804      }
805    } else {
806      RelocationEntry RE(Rel.SectionID, Rel.Offset, RelType, Value.Addend);
807      // Extra check to avoid relocation againt empty symbols (usually
808      // the R_PPC64_TOC).
809      if (Value.SymbolName && !TargetName.empty())
810        addRelocationForSymbol(RE, Value.SymbolName);
811      else
812        addRelocationForSection(RE, Value.SectionID);
813    }
814  } else {
815    RelocationEntry RE(Rel.SectionID, Rel.Offset, RelType, Value.Addend);
816    if (Value.SymbolName)
817      addRelocationForSymbol(RE, Value.SymbolName);
818    else
819      addRelocationForSection(RE, Value.SectionID);
820  }
821}
822
823unsigned RuntimeDyldELF::getCommonSymbolAlignment(const SymbolRef &Sym) {
824  // In ELF, the value of an SHN_COMMON symbol is its alignment requirement.
825  uint64_t Align;
826  Check(Sym.getValue(Align));
827  return Align;
828}
829
830bool RuntimeDyldELF::isCompatibleFormat(const ObjectBuffer *Buffer) const {
831  if (Buffer->getBufferSize() < strlen(ELF::ElfMagic))
832    return false;
833  return (memcmp(Buffer->getBufferStart(), ELF::ElfMagic, strlen(ELF::ElfMagic))) == 0;
834}
835} // namespace llvm
836