RuntimeDyldELF.cpp revision 7b449889e7886b263718b5103538970f287bc37e 
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/IntervalMap.h"
19#include "llvm/ADT/OwningPtr.h"
20#include "llvm/ADT/STLExtras.h"
21#include "llvm/ADT/StringRef.h"
22#include "llvm/ADT/Triple.h"
23#include "llvm/ExecutionEngine/ObjectBuffer.h"
24#include "llvm/ExecutionEngine/ObjectImage.h"
25#include "llvm/Object/ELF.h"
26#include "llvm/Object/ObjectFile.h"
27#include "llvm/Support/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_TARGET1 :
294  case ELF::R_ARM_ABS32 :
295    *TargetPtr += Value;
296    break;
297
298  // Write first 16 bit of 32 bit value to the mov instruction.
299  // Last 4 bit should be shifted.
300  case ELF::R_ARM_MOVW_ABS_NC :
301    // We are not expecting any other addend in the relocation address.
302    // Using 0x000F0FFF because MOVW has its 16 bit immediate split into 2
303    // non-contiguous fields.
304    assert((*TargetPtr & 0x000F0FFF) == 0);
305    Value = Value & 0xFFFF;
306    *TargetPtr |= Value & 0xFFF;
307    *TargetPtr |= ((Value >> 12) & 0xF) << 16;
308    break;
309
310  // Write last 16 bit of 32 bit value to the mov instruction.
311  // Last 4 bit should be shifted.
312  case ELF::R_ARM_MOVT_ABS :
313    // We are not expecting any other addend in the relocation address.
314    // Use 0x000F0FFF for the same reason as R_ARM_MOVW_ABS_NC.
315    assert((*TargetPtr & 0x000F0FFF) == 0);
316    Value = (Value >> 16) & 0xFFFF;
317    *TargetPtr |= Value & 0xFFF;
318    *TargetPtr |= ((Value >> 12) & 0xF) << 16;
319    break;
320
321  // Write 24 bit relative value to the branch instruction.
322  case ELF::R_ARM_PC24 :    // Fall through.
323  case ELF::R_ARM_CALL :    // Fall through.
324  case ELF::R_ARM_JUMP24 :
325    int32_t RelValue = static_cast<int32_t>(Value - FinalAddress - 8);
326    RelValue = (RelValue & 0x03FFFFFC) >> 2;
327    *TargetPtr &= 0xFF000000;
328    *TargetPtr |= RelValue;
329    break;
330  }
331}
332
333void RuntimeDyldELF::resolveMIPSRelocation(const SectionEntry &Section,
334                                           uint64_t Offset,
335                                           uint32_t Value,
336                                           uint32_t Type,
337                                           int32_t Addend) {
338  uint32_t* TargetPtr = (uint32_t*)(Section.Address + Offset);
339  Value += Addend;
340
341  DEBUG(dbgs() << "resolveMipselocation, LocalAddress: "
342               << Section.Address + Offset
343               << " FinalAddress: "
344               << format("%p",Section.LoadAddress + Offset)
345               << " Value: " << format("%x",Value)
346               << " Type: " << format("%x",Type)
347               << " Addend: " << format("%x",Addend)
348               << "\n");
349
350  switch(Type) {
351  default:
352    llvm_unreachable("Not implemented relocation type!");
353    break;
354  case ELF::R_MIPS_32:
355    *TargetPtr = Value + (*TargetPtr);
356    break;
357  case ELF::R_MIPS_26:
358    *TargetPtr = ((*TargetPtr) & 0xfc000000) | (( Value & 0x0fffffff) >> 2);
359    break;
360  case ELF::R_MIPS_HI16:
361    // Get the higher 16-bits. Also add 1 if bit 15 is 1.
362    Value += ((*TargetPtr) & 0x0000ffff) << 16;
363    *TargetPtr = ((*TargetPtr) & 0xffff0000) |
364                 (((Value + 0x8000) >> 16) & 0xffff);
365    break;
366   case ELF::R_MIPS_LO16:
367    Value += ((*TargetPtr) & 0x0000ffff);
368    *TargetPtr = ((*TargetPtr) & 0xffff0000) | (Value & 0xffff);
369    break;
370   }
371}
372
373// Return the .TOC. section address to R_PPC64_TOC relocations.
374uint64_t RuntimeDyldELF::findPPC64TOC() const {
375  // The TOC consists of sections .got, .toc, .tocbss, .plt in that
376  // order. The TOC starts where the first of these sections starts.
377  SectionList::const_iterator it = Sections.begin();
378  SectionList::const_iterator ite = Sections.end();
379  for (; it != ite; ++it) {
380    if (it->Name == ".got" ||
381        it->Name == ".toc" ||
382        it->Name == ".tocbss" ||
383        it->Name == ".plt")
384      break;
385  }
386  if (it == ite) {
387    // This may happen for
388    // * references to TOC base base (sym@toc, .odp relocation) without
389    // a .toc directive.
390    // In this case just use the first section (which is usually
391    // the .odp) since the code won't reference the .toc base
392    // directly.
393    it = Sections.begin();
394  }
395  assert (it != ite);
396  // Per the ppc64-elf-linux ABI, The TOC base is TOC value plus 0x8000
397  // thus permitting a full 64 Kbytes segment.
398  return it->LoadAddress + 0x8000;
399}
400
401// Returns the sections and offset associated with the ODP entry referenced
402// by Symbol.
403void RuntimeDyldELF::findOPDEntrySection(ObjectImage &Obj,
404                                         ObjSectionToIDMap &LocalSections,
405                                         RelocationValueRef &Rel) {
406  // Get the ELF symbol value (st_value) to compare with Relocation offset in
407  // .opd entries
408
409  error_code err;
410  for (section_iterator si = Obj.begin_sections(),
411     se = Obj.end_sections(); si != se; si.increment(err)) {
412    StringRef SectionName;
413    check(si->getName(SectionName));
414    if (SectionName != ".opd")
415      continue;
416
417    for (relocation_iterator i = si->begin_relocations(),
418         e = si->end_relocations(); i != e;) {
419      check(err);
420
421      // The R_PPC64_ADDR64 relocation indicates the first field
422      // of a .opd entry
423      uint64_t TypeFunc;
424      check(i->getType(TypeFunc));
425      if (TypeFunc != ELF::R_PPC64_ADDR64) {
426        i.increment(err);
427        continue;
428      }
429
430      SymbolRef TargetSymbol;
431      uint64_t TargetSymbolOffset;
432      int64_t TargetAdditionalInfo;
433      check(i->getSymbol(TargetSymbol));
434      check(i->getOffset(TargetSymbolOffset));
435      check(i->getAdditionalInfo(TargetAdditionalInfo));
436
437      i = i.increment(err);
438      if (i == e)
439        break;
440      check(err);
441
442      // Just check if following relocation is a R_PPC64_TOC
443      uint64_t TypeTOC;
444      check(i->getType(TypeTOC));
445      if (TypeTOC != ELF::R_PPC64_TOC)
446        continue;
447
448      // Finally compares the Symbol value and the target symbol offset
449      // to check if this .opd entry refers to the symbol the relocation
450      // points to.
451      if (Rel.Addend != (intptr_t)TargetSymbolOffset)
452        continue;
453
454      section_iterator tsi(Obj.end_sections());
455      check(TargetSymbol.getSection(tsi));
456      Rel.SectionID = findOrEmitSection(Obj, (*tsi), true, LocalSections);
457      Rel.Addend = (intptr_t)TargetAdditionalInfo;
458      return;
459    }
460  }
461  llvm_unreachable("Attempting to get address of ODP entry!");
462}
463
464// Relocation masks following the #lo(value), #hi(value), #higher(value),
465// and #highest(value) macros defined in section 4.5.1. Relocation Types
466// in PPC-elf64abi document.
467//
468static inline
469uint16_t applyPPClo (uint64_t value)
470{
471  return value & 0xffff;
472}
473
474static inline
475uint16_t applyPPChi (uint64_t value)
476{
477  return (value >> 16) & 0xffff;
478}
479
480static inline
481uint16_t applyPPChigher (uint64_t value)
482{
483  return (value >> 32) & 0xffff;
484}
485
486static inline
487uint16_t applyPPChighest (uint64_t value)
488{
489  return (value >> 48) & 0xffff;
490}
491
492void RuntimeDyldELF::resolvePPC64Relocation(const SectionEntry &Section,
493                                            uint64_t Offset,
494                                            uint64_t Value,
495                                            uint32_t Type,
496                                            int64_t Addend) {
497  uint8_t* LocalAddress = Section.Address + Offset;
498  switch (Type) {
499  default:
500    llvm_unreachable("Relocation type not implemented yet!");
501  break;
502  case ELF::R_PPC64_ADDR16_LO :
503    writeInt16BE(LocalAddress, applyPPClo (Value + Addend));
504    break;
505  case ELF::R_PPC64_ADDR16_HI :
506    writeInt16BE(LocalAddress, applyPPChi (Value + Addend));
507    break;
508  case ELF::R_PPC64_ADDR16_HIGHER :
509    writeInt16BE(LocalAddress, applyPPChigher (Value + Addend));
510    break;
511  case ELF::R_PPC64_ADDR16_HIGHEST :
512    writeInt16BE(LocalAddress, applyPPChighest (Value + Addend));
513    break;
514  case ELF::R_PPC64_ADDR14 : {
515    assert(((Value + Addend) & 3) == 0);
516    // Preserve the AA/LK bits in the branch instruction
517    uint8_t aalk = *(LocalAddress+3);
518    writeInt16BE(LocalAddress + 2, (aalk & 3) | ((Value + Addend) & 0xfffc));
519  } break;
520  case ELF::R_PPC64_ADDR32 : {
521    int32_t Result = static_cast<int32_t>(Value + Addend);
522    if (SignExtend32<32>(Result) != Result)
523      llvm_unreachable("Relocation R_PPC64_REL32 overflow");
524    writeInt32BE(LocalAddress, Result);
525  } break;
526  case ELF::R_PPC64_REL24 : {
527    uint64_t FinalAddress = (Section.LoadAddress + Offset);
528    int32_t delta = static_cast<int32_t>(Value - FinalAddress + Addend);
529    if (SignExtend32<24>(delta) != delta)
530      llvm_unreachable("Relocation R_PPC64_REL24 overflow");
531    // Generates a 'bl <address>' instruction
532    writeInt32BE(LocalAddress, 0x48000001 | (delta & 0x03FFFFFC));
533  } break;
534  case ELF::R_PPC64_ADDR64 :
535    writeInt64BE(LocalAddress, Value + Addend);
536    break;
537  case ELF::R_PPC64_TOC :
538    writeInt64BE(LocalAddress, findPPC64TOC());
539    break;
540  case ELF::R_PPC64_TOC16 : {
541    uint64_t TOCStart = findPPC64TOC();
542    Value = applyPPClo((Value + Addend) - TOCStart);
543    writeInt16BE(LocalAddress, applyPPClo(Value));
544  } break;
545  case ELF::R_PPC64_TOC16_DS : {
546    uint64_t TOCStart = findPPC64TOC();
547    Value = ((Value + Addend) - TOCStart);
548    writeInt16BE(LocalAddress, applyPPClo(Value));
549  } break;
550  }
551}
552
553
554void RuntimeDyldELF::resolveRelocation(const SectionEntry &Section,
555                                       uint64_t Offset,
556                                       uint64_t Value,
557                                       uint32_t Type,
558                                       int64_t Addend) {
559  switch (Arch) {
560  case Triple::x86_64:
561    resolveX86_64Relocation(Section, Offset, Value, Type, Addend);
562    break;
563  case Triple::x86:
564    resolveX86Relocation(Section, Offset,
565                         (uint32_t)(Value & 0xffffffffL), Type,
566                         (uint32_t)(Addend & 0xffffffffL));
567    break;
568  case Triple::arm:    // Fall through.
569  case Triple::thumb:
570    resolveARMRelocation(Section, Offset,
571                         (uint32_t)(Value & 0xffffffffL), Type,
572                         (uint32_t)(Addend & 0xffffffffL));
573    break;
574  case Triple::mips:    // Fall through.
575  case Triple::mipsel:
576    resolveMIPSRelocation(Section, Offset,
577                          (uint32_t)(Value & 0xffffffffL), Type,
578                          (uint32_t)(Addend & 0xffffffffL));
579    break;
580  case Triple::ppc64:
581    resolvePPC64Relocation(Section, Offset, Value, Type, Addend);
582    break;
583  default: llvm_unreachable("Unsupported CPU type!");
584  }
585}
586
587void RuntimeDyldELF::processRelocationRef(const ObjRelocationInfo &Rel,
588                                          ObjectImage &Obj,
589                                          ObjSectionToIDMap &ObjSectionToID,
590                                          const SymbolTableMap &Symbols,
591                                          StubMap &Stubs) {
592
593  uint32_t RelType = (uint32_t)(Rel.Type & 0xffffffffL);
594  intptr_t Addend = (intptr_t)Rel.AdditionalInfo;
595  const SymbolRef &Symbol = Rel.Symbol;
596
597  // Obtain the symbol name which is referenced in the relocation
598  StringRef TargetName;
599  Symbol.getName(TargetName);
600  DEBUG(dbgs() << "\t\tRelType: " << RelType
601               << " Addend: " << Addend
602               << " TargetName: " << TargetName
603               << "\n");
604  RelocationValueRef Value;
605  // First search for the symbol in the local symbol table
606  SymbolTableMap::const_iterator lsi = Symbols.find(TargetName.data());
607  SymbolRef::Type SymType;
608  Symbol.getType(SymType);
609  if (lsi != Symbols.end()) {
610    Value.SectionID = lsi->second.first;
611    Value.Addend = lsi->second.second;
612  } else {
613    // Search for the symbol in the global symbol table
614    SymbolTableMap::const_iterator gsi =
615        GlobalSymbolTable.find(TargetName.data());
616    if (gsi != GlobalSymbolTable.end()) {
617      Value.SectionID = gsi->second.first;
618      Value.Addend = gsi->second.second;
619    } else {
620      switch (SymType) {
621        case SymbolRef::ST_Debug: {
622          // TODO: Now ELF SymbolRef::ST_Debug = STT_SECTION, it's not obviously
623          // and can be changed by another developers. Maybe best way is add
624          // a new symbol type ST_Section to SymbolRef and use it.
625          section_iterator si(Obj.end_sections());
626          Symbol.getSection(si);
627          if (si == Obj.end_sections())
628            llvm_unreachable("Symbol section not found, bad object file format!");
629          DEBUG(dbgs() << "\t\tThis is section symbol\n");
630          // Default to 'true' in case isText fails (though it never does).
631          bool isCode = true;
632          si->isText(isCode);
633          Value.SectionID = findOrEmitSection(Obj,
634                                              (*si),
635                                              isCode,
636                                              ObjSectionToID);
637          Value.Addend = Addend;
638          break;
639        }
640        case SymbolRef::ST_Unknown: {
641          Value.SymbolName = TargetName.data();
642          Value.Addend = Addend;
643          break;
644        }
645        default:
646          llvm_unreachable("Unresolved symbol type!");
647          break;
648      }
649    }
650  }
651  DEBUG(dbgs() << "\t\tRel.SectionID: " << Rel.SectionID
652               << " Rel.Offset: " << Rel.Offset
653               << "\n");
654  if (Arch == Triple::arm &&
655      (RelType == ELF::R_ARM_PC24 ||
656       RelType == ELF::R_ARM_CALL ||
657       RelType == ELF::R_ARM_JUMP24)) {
658    // This is an ARM branch relocation, need to use a stub function.
659    DEBUG(dbgs() << "\t\tThis is an ARM branch relocation.");
660    SectionEntry &Section = Sections[Rel.SectionID];
661
662    // Look for an existing stub.
663    StubMap::const_iterator i = Stubs.find(Value);
664    if (i != Stubs.end()) {
665        resolveRelocation(Section, Rel.Offset,
666                          (uint64_t)Section.Address + i->second, RelType, 0);
667      DEBUG(dbgs() << " Stub function found\n");
668    } else {
669      // Create a new stub function.
670      DEBUG(dbgs() << " Create a new stub function\n");
671      Stubs[Value] = Section.StubOffset;
672      uint8_t *StubTargetAddr = createStubFunction(Section.Address +
673                                                   Section.StubOffset);
674      RelocationEntry RE(Rel.SectionID, StubTargetAddr - Section.Address,
675                         ELF::R_ARM_ABS32, Value.Addend);
676      if (Value.SymbolName)
677        addRelocationForSymbol(RE, Value.SymbolName);
678      else
679        addRelocationForSection(RE, Value.SectionID);
680
681      resolveRelocation(Section, Rel.Offset,
682                        (uint64_t)Section.Address + Section.StubOffset,
683                        RelType, 0);
684      Section.StubOffset += getMaxStubSize();
685    }
686  } else if ((Arch == Triple::mipsel || Arch == Triple::mips) &&
687             RelType == ELF::R_MIPS_26) {
688    // This is an Mips branch relocation, need to use a stub function.
689    DEBUG(dbgs() << "\t\tThis is a Mips branch relocation.");
690    SectionEntry &Section = Sections[Rel.SectionID];
691    uint8_t *Target = Section.Address + Rel.Offset;
692    uint32_t *TargetAddress = (uint32_t *)Target;
693
694    // Extract the addend from the instruction.
695    uint32_t Addend = ((*TargetAddress) & 0x03ffffff) << 2;
696
697    Value.Addend += Addend;
698
699    //  Look up for existing stub.
700    StubMap::const_iterator i = Stubs.find(Value);
701    if (i != Stubs.end()) {
702      resolveRelocation(Section, Rel.Offset,
703                        (uint64_t)Section.Address + i->second, RelType, 0);
704      DEBUG(dbgs() << " Stub function found\n");
705    } else {
706      // Create a new stub function.
707      DEBUG(dbgs() << " Create a new stub function\n");
708      Stubs[Value] = Section.StubOffset;
709      uint8_t *StubTargetAddr = createStubFunction(Section.Address +
710                                                   Section.StubOffset);
711
712      // Creating Hi and Lo relocations for the filled stub instructions.
713      RelocationEntry REHi(Rel.SectionID,
714                           StubTargetAddr - Section.Address,
715                           ELF::R_MIPS_HI16, Value.Addend);
716      RelocationEntry RELo(Rel.SectionID,
717                           StubTargetAddr - Section.Address + 4,
718                           ELF::R_MIPS_LO16, Value.Addend);
719
720      if (Value.SymbolName) {
721        addRelocationForSymbol(REHi, Value.SymbolName);
722        addRelocationForSymbol(RELo, Value.SymbolName);
723      } else {
724        addRelocationForSection(REHi, Value.SectionID);
725        addRelocationForSection(RELo, Value.SectionID);
726      }
727
728      resolveRelocation(Section, Rel.Offset,
729                        (uint64_t)Section.Address + Section.StubOffset,
730                        RelType, 0);
731      Section.StubOffset += getMaxStubSize();
732    }
733  } else if (Arch == Triple::ppc64) {
734    if (RelType == ELF::R_PPC64_REL24) {
735      // A PPC branch relocation will need a stub function if the target is
736      // an external symbol (Symbol::ST_Unknown) or if the target address
737      // is not within the signed 24-bits branch address.
738      SectionEntry &Section = Sections[Rel.SectionID];
739      uint8_t *Target = Section.Address + Rel.Offset;
740      bool RangeOverflow = false;
741      if (SymType != SymbolRef::ST_Unknown) {
742        // A function call may points to the .opd entry, so the final symbol value
743        // in calculated based in the relocation values in .opd section.
744        findOPDEntrySection(Obj, ObjSectionToID, Value);
745        uint8_t *RelocTarget = Sections[Value.SectionID].Address + Value.Addend;
746        int32_t delta = static_cast<int32_t>(Target - RelocTarget);
747        // If it is within 24-bits branch range, just set the branch target
748        if (SignExtend32<24>(delta) == delta) {
749          RelocationEntry RE(Rel.SectionID, Rel.Offset, RelType, Value.Addend);
750          if (Value.SymbolName)
751            addRelocationForSymbol(RE, Value.SymbolName);
752          else
753            addRelocationForSection(RE, Value.SectionID);
754        } else {
755          RangeOverflow = true;
756        }
757      }
758      if (SymType == SymbolRef::ST_Unknown || RangeOverflow == true) {
759        // It is an external symbol (SymbolRef::ST_Unknown) or within a range
760        // larger than 24-bits.
761        StubMap::const_iterator i = Stubs.find(Value);
762        if (i != Stubs.end()) {
763          // Symbol function stub already created, just relocate to it
764          resolveRelocation(Section, Rel.Offset,
765                            (uint64_t)Section.Address + i->second, RelType, 0);
766          DEBUG(dbgs() << " Stub function found\n");
767        } else {
768          // Create a new stub function.
769          DEBUG(dbgs() << " Create a new stub function\n");
770          Stubs[Value] = Section.StubOffset;
771          uint8_t *StubTargetAddr = createStubFunction(Section.Address +
772                                                       Section.StubOffset);
773          RelocationEntry RE(Rel.SectionID, StubTargetAddr - Section.Address,
774                             ELF::R_PPC64_ADDR64, Value.Addend);
775
776          // Generates the 64-bits address loads as exemplified in section
777          // 4.5.1 in PPC64 ELF ABI.
778          RelocationEntry REhst(Rel.SectionID,
779                                StubTargetAddr - Section.Address + 2,
780                                ELF::R_PPC64_ADDR16_HIGHEST, Value.Addend);
781          RelocationEntry REhr(Rel.SectionID,
782                               StubTargetAddr - Section.Address + 6,
783                               ELF::R_PPC64_ADDR16_HIGHER, Value.Addend);
784          RelocationEntry REh(Rel.SectionID,
785                              StubTargetAddr - Section.Address + 14,
786                              ELF::R_PPC64_ADDR16_HI, Value.Addend);
787          RelocationEntry REl(Rel.SectionID,
788                              StubTargetAddr - Section.Address + 18,
789                              ELF::R_PPC64_ADDR16_LO, Value.Addend);
790
791          if (Value.SymbolName) {
792            addRelocationForSymbol(REhst, Value.SymbolName);
793            addRelocationForSymbol(REhr,  Value.SymbolName);
794            addRelocationForSymbol(REh,   Value.SymbolName);
795            addRelocationForSymbol(REl,   Value.SymbolName);
796          } else {
797            addRelocationForSection(REhst, Value.SectionID);
798            addRelocationForSection(REhr,  Value.SectionID);
799            addRelocationForSection(REh,   Value.SectionID);
800            addRelocationForSection(REl,   Value.SectionID);
801          }
802
803          resolveRelocation(Section, Rel.Offset,
804                            (uint64_t)Section.Address + Section.StubOffset,
805                            RelType, 0);
806          if (SymType == SymbolRef::ST_Unknown)
807            // Restore the TOC for external calls
808            writeInt32BE(Target+4, 0xE8410028); // ld r2,40(r1)
809          Section.StubOffset += getMaxStubSize();
810        }
811      }
812    } else {
813      RelocationEntry RE(Rel.SectionID, Rel.Offset, RelType, Value.Addend);
814      // Extra check to avoid relocation againt empty symbols (usually
815      // the R_PPC64_TOC).
816      if (Value.SymbolName && !TargetName.empty())
817        addRelocationForSymbol(RE, Value.SymbolName);
818      else
819        addRelocationForSection(RE, Value.SectionID);
820    }
821  } else {
822    RelocationEntry RE(Rel.SectionID, Rel.Offset, RelType, Value.Addend);
823    if (Value.SymbolName)
824      addRelocationForSymbol(RE, Value.SymbolName);
825    else
826      addRelocationForSection(RE, Value.SectionID);
827  }
828}
829
830unsigned RuntimeDyldELF::getCommonSymbolAlignment(const SymbolRef &Sym) {
831  // In ELF, the value of an SHN_COMMON symbol is its alignment requirement.
832  uint64_t Align;
833  Check(Sym.getValue(Align));
834  return Align;
835}
836
837bool RuntimeDyldELF::isCompatibleFormat(const ObjectBuffer *Buffer) const {
838  if (Buffer->getBufferSize() < strlen(ELF::ElfMagic))
839    return false;
840  return (memcmp(Buffer->getBufferStart(), ELF::ElfMagic, strlen(ELF::ElfMagic))) == 0;
841}
842} // namespace llvm
843