RuntimeDyldELF.cpp revision 249423 
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<class ELFT>
42class DyldELFObject
43  : public ELFObjectFile<ELFT> {
44  LLVM_ELF_IMPORT_TYPES(ELFT)
45
46  typedef Elf_Shdr_Impl<ELFT> Elf_Shdr;
47  typedef Elf_Sym_Impl<ELFT> Elf_Sym;
48  typedef
49    Elf_Rel_Impl<ELFT, false> Elf_Rel;
50  typedef
51    Elf_Rel_Impl<ELFT, true> Elf_Rela;
52
53  typedef Elf_Ehdr_Impl<ELFT> Elf_Ehdr;
54
55  typedef typename ELFDataTypeTypedefHelper<
56          ELFT>::value_type addr_type;
57
58public:
59  DyldELFObject(MemoryBuffer *Wrapper, error_code &ec);
60
61  void updateSectionAddress(const SectionRef &Sec, uint64_t Addr);
62  void updateSymbolAddress(const SymbolRef &Sym, uint64_t Addr);
63
64  // Methods for type inquiry through isa, cast and dyn_cast
65  static inline bool classof(const Binary *v) {
66    return (isa<ELFObjectFile<ELFT> >(v)
67            && classof(cast<ELFObjectFile
68                <ELFT> >(v)));
69  }
70  static inline bool classof(
71      const ELFObjectFile<ELFT> *v) {
72    return v->isDyldType();
73  }
74};
75
76template<class ELFT>
77class ELFObjectImage : public ObjectImageCommon {
78  protected:
79    DyldELFObject<ELFT> *DyldObj;
80    bool Registered;
81
82  public:
83    ELFObjectImage(ObjectBuffer *Input,
84                 DyldELFObject<ELFT> *Obj)
85    : ObjectImageCommon(Input, Obj),
86      DyldObj(Obj),
87      Registered(false) {}
88
89    virtual ~ELFObjectImage() {
90      if (Registered)
91        deregisterWithDebugger();
92    }
93
94    // Subclasses can override these methods to update the image with loaded
95    // addresses for sections and common symbols
96    virtual void updateSectionAddress(const SectionRef &Sec, uint64_t Addr)
97    {
98      DyldObj->updateSectionAddress(Sec, Addr);
99    }
100
101    virtual void updateSymbolAddress(const SymbolRef &Sym, uint64_t Addr)
102    {
103      DyldObj->updateSymbolAddress(Sym, Addr);
104    }
105
106    virtual void registerWithDebugger()
107    {
108      JITRegistrar::getGDBRegistrar().registerObject(*Buffer);
109      Registered = true;
110    }
111    virtual void deregisterWithDebugger()
112    {
113      JITRegistrar::getGDBRegistrar().deregisterObject(*Buffer);
114    }
115};
116
117// The MemoryBuffer passed into this constructor is just a wrapper around the
118// actual memory.  Ultimately, the Binary parent class will take ownership of
119// this MemoryBuffer object but not the underlying memory.
120template<class ELFT>
121DyldELFObject<ELFT>::DyldELFObject(MemoryBuffer *Wrapper, error_code &ec)
122  : ELFObjectFile<ELFT>(Wrapper, ec) {
123  this->isDyldELFObject = true;
124}
125
126template<class ELFT>
127void DyldELFObject<ELFT>::updateSectionAddress(const SectionRef &Sec,
128                                               uint64_t Addr) {
129  DataRefImpl ShdrRef = Sec.getRawDataRefImpl();
130  Elf_Shdr *shdr = const_cast<Elf_Shdr*>(
131                          reinterpret_cast<const Elf_Shdr *>(ShdrRef.p));
132
133  // This assumes the address passed in matches the target address bitness
134  // The template-based type cast handles everything else.
135  shdr->sh_addr = static_cast<addr_type>(Addr);
136}
137
138template<class ELFT>
139void DyldELFObject<ELFT>::updateSymbolAddress(const SymbolRef &SymRef,
140                                              uint64_t Addr) {
141
142  Elf_Sym *sym = const_cast<Elf_Sym*>(
143    ELFObjectFile<ELFT>::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
152namespace llvm {
153
154ObjectImage *RuntimeDyldELF::createObjectImage(ObjectBuffer *Buffer) {
155  if (Buffer->getBufferSize() < ELF::EI_NIDENT)
156    llvm_unreachable("Unexpected ELF object size");
157  std::pair<unsigned char, unsigned char> Ident = std::make_pair(
158                         (uint8_t)Buffer->getBufferStart()[ELF::EI_CLASS],
159                         (uint8_t)Buffer->getBufferStart()[ELF::EI_DATA]);
160  error_code ec;
161
162  if (Ident.first == ELF::ELFCLASS32 && Ident.second == ELF::ELFDATA2LSB) {
163    DyldELFObject<ELFType<support::little, 4, false> > *Obj =
164      new DyldELFObject<ELFType<support::little, 4, false> >(
165        Buffer->getMemBuffer(), ec);
166    return new ELFObjectImage<ELFType<support::little, 4, false> >(Buffer, Obj);
167  }
168  else if (Ident.first == ELF::ELFCLASS32 && Ident.second == ELF::ELFDATA2MSB) {
169    DyldELFObject<ELFType<support::big, 4, false> > *Obj =
170      new DyldELFObject<ELFType<support::big, 4, false> >(
171        Buffer->getMemBuffer(), ec);
172    return new ELFObjectImage<ELFType<support::big, 4, false> >(Buffer, Obj);
173  }
174  else if (Ident.first == ELF::ELFCLASS64 && Ident.second == ELF::ELFDATA2MSB) {
175    DyldELFObject<ELFType<support::big, 8, true> > *Obj =
176      new DyldELFObject<ELFType<support::big, 8, true> >(
177        Buffer->getMemBuffer(), ec);
178    return new ELFObjectImage<ELFType<support::big, 8, true> >(Buffer, Obj);
179  }
180  else if (Ident.first == ELF::ELFCLASS64 && Ident.second == ELF::ELFDATA2LSB) {
181    DyldELFObject<ELFType<support::little, 8, true> > *Obj =
182      new DyldELFObject<ELFType<support::little, 8, true> >(
183        Buffer->getMemBuffer(), ec);
184    return new ELFObjectImage<ELFType<support::little, 8, true> >(Buffer, Obj);
185  }
186  else
187    llvm_unreachable("Unexpected ELF format");
188}
189
190RuntimeDyldELF::~RuntimeDyldELF() {
191}
192
193void RuntimeDyldELF::resolveX86_64Relocation(const SectionEntry &Section,
194                                             uint64_t Offset,
195                                             uint64_t Value,
196                                             uint32_t Type,
197                                             int64_t Addend) {
198  switch (Type) {
199  default:
200    llvm_unreachable("Relocation type not implemented yet!");
201  break;
202  case ELF::R_X86_64_64: {
203    uint64_t *Target = reinterpret_cast<uint64_t*>(Section.Address + Offset);
204    *Target = Value + Addend;
205    DEBUG(dbgs() << "Writing " << format("%p", (Value + Addend))
206                 << " at " << format("%p\n",Target));
207    break;
208  }
209  case ELF::R_X86_64_32:
210  case ELF::R_X86_64_32S: {
211    Value += Addend;
212    assert((Type == ELF::R_X86_64_32 && (Value <= UINT32_MAX)) ||
213           (Type == ELF::R_X86_64_32S &&
214             ((int64_t)Value <= INT32_MAX && (int64_t)Value >= INT32_MIN)));
215    uint32_t TruncatedAddr = (Value & 0xFFFFFFFF);
216    uint32_t *Target = reinterpret_cast<uint32_t*>(Section.Address + Offset);
217    *Target = TruncatedAddr;
218    DEBUG(dbgs() << "Writing " << format("%p", TruncatedAddr)
219                 << " at " << format("%p\n",Target));
220    break;
221  }
222  case ELF::R_X86_64_PC32: {
223    // Get the placeholder value from the generated object since
224    // a previous relocation attempt may have overwritten the loaded version
225    uint32_t *Placeholder = reinterpret_cast<uint32_t*>(Section.ObjAddress
226                                                                   + Offset);
227    uint32_t *Target = reinterpret_cast<uint32_t*>(Section.Address + Offset);
228    uint64_t  FinalAddress = Section.LoadAddress + Offset;
229    int64_t RealOffset = *Placeholder + Value + Addend - FinalAddress;
230    assert(RealOffset <= INT32_MAX && RealOffset >= INT32_MIN);
231    int32_t TruncOffset = (RealOffset & 0xFFFFFFFF);
232    *Target = TruncOffset;
233    break;
234  }
235  }
236}
237
238void RuntimeDyldELF::resolveX86Relocation(const SectionEntry &Section,
239                                          uint64_t Offset,
240                                          uint32_t Value,
241                                          uint32_t Type,
242                                          int32_t Addend) {
243  switch (Type) {
244  case ELF::R_386_32: {
245    // Get the placeholder value from the generated object since
246    // a previous relocation attempt may have overwritten the loaded version
247    uint32_t *Placeholder = reinterpret_cast<uint32_t*>(Section.ObjAddress
248                                                                   + Offset);
249    uint32_t *Target = reinterpret_cast<uint32_t*>(Section.Address + Offset);
250    *Target = *Placeholder + Value + Addend;
251    break;
252  }
253  case ELF::R_386_PC32: {
254    // Get the placeholder value from the generated object since
255    // a previous relocation attempt may have overwritten the loaded version
256    uint32_t *Placeholder = reinterpret_cast<uint32_t*>(Section.ObjAddress
257                                                                   + Offset);
258    uint32_t *Target = reinterpret_cast<uint32_t*>(Section.Address + Offset);
259    uint32_t  FinalAddress = ((Section.LoadAddress + Offset) & 0xFFFFFFFF);
260    uint32_t RealOffset = *Placeholder + Value + Addend - FinalAddress;
261    *Target = RealOffset;
262    break;
263    }
264    default:
265      // There are other relocation types, but it appears these are the
266      // only ones currently used by the LLVM ELF object writer
267      llvm_unreachable("Relocation type not implemented yet!");
268      break;
269  }
270}
271
272void RuntimeDyldELF::resolveARMRelocation(const SectionEntry &Section,
273                                          uint64_t Offset,
274                                          uint32_t Value,
275                                          uint32_t Type,
276                                          int32_t Addend) {
277  // TODO: Add Thumb relocations.
278  uint32_t* TargetPtr = (uint32_t*)(Section.Address + Offset);
279  uint32_t FinalAddress = ((Section.LoadAddress + Offset) & 0xFFFFFFFF);
280  Value += Addend;
281
282  DEBUG(dbgs() << "resolveARMRelocation, LocalAddress: "
283               << Section.Address + Offset
284               << " FinalAddress: " << format("%p",FinalAddress)
285               << " Value: " << format("%x",Value)
286               << " Type: " << format("%x",Type)
287               << " Addend: " << format("%x",Addend)
288               << "\n");
289
290  switch(Type) {
291  default:
292    llvm_unreachable("Not implemented relocation type!");
293
294  // Write a 32bit value to relocation address, taking into account the
295  // implicit addend encoded in the target.
296  case ELF::R_ARM_TARGET1 :
297  case ELF::R_ARM_ABS32 :
298    *TargetPtr += Value;
299    break;
300
301  // Write first 16 bit of 32 bit value to the mov instruction.
302  // Last 4 bit should be shifted.
303  case ELF::R_ARM_MOVW_ABS_NC :
304    // We are not expecting any other addend in the relocation address.
305    // Using 0x000F0FFF because MOVW has its 16 bit immediate split into 2
306    // non-contiguous fields.
307    assert((*TargetPtr & 0x000F0FFF) == 0);
308    Value = Value & 0xFFFF;
309    *TargetPtr |= Value & 0xFFF;
310    *TargetPtr |= ((Value >> 12) & 0xF) << 16;
311    break;
312
313  // Write last 16 bit of 32 bit value to the mov instruction.
314  // Last 4 bit should be shifted.
315  case ELF::R_ARM_MOVT_ABS :
316    // We are not expecting any other addend in the relocation address.
317    // Use 0x000F0FFF for the same reason as R_ARM_MOVW_ABS_NC.
318    assert((*TargetPtr & 0x000F0FFF) == 0);
319    Value = (Value >> 16) & 0xFFFF;
320    *TargetPtr |= Value & 0xFFF;
321    *TargetPtr |= ((Value >> 12) & 0xF) << 16;
322    break;
323
324  // Write 24 bit relative value to the branch instruction.
325  case ELF::R_ARM_PC24 :    // Fall through.
326  case ELF::R_ARM_CALL :    // Fall through.
327  case ELF::R_ARM_JUMP24 :
328    int32_t RelValue = static_cast<int32_t>(Value - FinalAddress - 8);
329    RelValue = (RelValue & 0x03FFFFFC) >> 2;
330    *TargetPtr &= 0xFF000000;
331    *TargetPtr |= RelValue;
332    break;
333  }
334}
335
336void RuntimeDyldELF::resolveMIPSRelocation(const SectionEntry &Section,
337                                           uint64_t Offset,
338                                           uint32_t Value,
339                                           uint32_t Type,
340                                           int32_t Addend) {
341  uint32_t* TargetPtr = (uint32_t*)(Section.Address + Offset);
342  Value += Addend;
343
344  DEBUG(dbgs() << "resolveMipselocation, LocalAddress: "
345               << Section.Address + Offset
346               << " FinalAddress: "
347               << format("%p",Section.LoadAddress + Offset)
348               << " Value: " << format("%x",Value)
349               << " Type: " << format("%x",Type)
350               << " Addend: " << format("%x",Addend)
351               << "\n");
352
353  switch(Type) {
354  default:
355    llvm_unreachable("Not implemented relocation type!");
356    break;
357  case ELF::R_MIPS_32:
358    *TargetPtr = Value + (*TargetPtr);
359    break;
360  case ELF::R_MIPS_26:
361    *TargetPtr = ((*TargetPtr) & 0xfc000000) | (( Value & 0x0fffffff) >> 2);
362    break;
363  case ELF::R_MIPS_HI16:
364    // Get the higher 16-bits. Also add 1 if bit 15 is 1.
365    Value += ((*TargetPtr) & 0x0000ffff) << 16;
366    *TargetPtr = ((*TargetPtr) & 0xffff0000) |
367                 (((Value + 0x8000) >> 16) & 0xffff);
368    break;
369   case ELF::R_MIPS_LO16:
370    Value += ((*TargetPtr) & 0x0000ffff);
371    *TargetPtr = ((*TargetPtr) & 0xffff0000) | (Value & 0xffff);
372    break;
373   }
374}
375
376// Return the .TOC. section address to R_PPC64_TOC relocations.
377uint64_t RuntimeDyldELF::findPPC64TOC() const {
378  // The TOC consists of sections .got, .toc, .tocbss, .plt in that
379  // order. The TOC starts where the first of these sections starts.
380  SectionList::const_iterator it = Sections.begin();
381  SectionList::const_iterator ite = Sections.end();
382  for (; it != ite; ++it) {
383    if (it->Name == ".got" ||
384        it->Name == ".toc" ||
385        it->Name == ".tocbss" ||
386        it->Name == ".plt")
387      break;
388  }
389  if (it == ite) {
390    // This may happen for
391    // * references to TOC base base (sym@toc, .odp relocation) without
392    // a .toc directive.
393    // In this case just use the first section (which is usually
394    // the .odp) since the code won't reference the .toc base
395    // directly.
396    it = Sections.begin();
397  }
398  assert (it != ite);
399  // Per the ppc64-elf-linux ABI, The TOC base is TOC value plus 0x8000
400  // thus permitting a full 64 Kbytes segment.
401  return it->LoadAddress + 0x8000;
402}
403
404// Returns the sections and offset associated with the ODP entry referenced
405// by Symbol.
406void RuntimeDyldELF::findOPDEntrySection(ObjectImage &Obj,
407                                         ObjSectionToIDMap &LocalSections,
408                                         RelocationValueRef &Rel) {
409  // Get the ELF symbol value (st_value) to compare with Relocation offset in
410  // .opd entries
411
412  error_code err;
413  for (section_iterator si = Obj.begin_sections(),
414     se = Obj.end_sections(); si != se; si.increment(err)) {
415    StringRef SectionName;
416    check(si->getName(SectionName));
417    if (SectionName != ".opd")
418      continue;
419
420    for (relocation_iterator i = si->begin_relocations(),
421         e = si->end_relocations(); i != e;) {
422      check(err);
423
424      // The R_PPC64_ADDR64 relocation indicates the first field
425      // of a .opd entry
426      uint64_t TypeFunc;
427      check(i->getType(TypeFunc));
428      if (TypeFunc != ELF::R_PPC64_ADDR64) {
429        i.increment(err);
430        continue;
431      }
432
433      SymbolRef TargetSymbol;
434      uint64_t TargetSymbolOffset;
435      int64_t TargetAdditionalInfo;
436      check(i->getSymbol(TargetSymbol));
437      check(i->getOffset(TargetSymbolOffset));
438      check(i->getAdditionalInfo(TargetAdditionalInfo));
439
440      i = i.increment(err);
441      if (i == e)
442        break;
443      check(err);
444
445      // Just check if following relocation is a R_PPC64_TOC
446      uint64_t TypeTOC;
447      check(i->getType(TypeTOC));
448      if (TypeTOC != ELF::R_PPC64_TOC)
449        continue;
450
451      // Finally compares the Symbol value and the target symbol offset
452      // to check if this .opd entry refers to the symbol the relocation
453      // points to.
454      if (Rel.Addend != (intptr_t)TargetSymbolOffset)
455        continue;
456
457      section_iterator tsi(Obj.end_sections());
458      check(TargetSymbol.getSection(tsi));
459      Rel.SectionID = findOrEmitSection(Obj, (*tsi), true, LocalSections);
460      Rel.Addend = (intptr_t)TargetAdditionalInfo;
461      return;
462    }
463  }
464  llvm_unreachable("Attempting to get address of ODP entry!");
465}
466
467// Relocation masks following the #lo(value), #hi(value), #higher(value),
468// and #highest(value) macros defined in section 4.5.1. Relocation Types
469// in PPC-elf64abi document.
470//
471static inline
472uint16_t applyPPClo (uint64_t value)
473{
474  return value & 0xffff;
475}
476
477static inline
478uint16_t applyPPChi (uint64_t value)
479{
480  return (value >> 16) & 0xffff;
481}
482
483static inline
484uint16_t applyPPChigher (uint64_t value)
485{
486  return (value >> 32) & 0xffff;
487}
488
489static inline
490uint16_t applyPPChighest (uint64_t value)
491{
492  return (value >> 48) & 0xffff;
493}
494
495void RuntimeDyldELF::resolvePPC64Relocation(const SectionEntry &Section,
496                                            uint64_t Offset,
497                                            uint64_t Value,
498                                            uint32_t Type,
499                                            int64_t Addend) {
500  uint8_t* LocalAddress = Section.Address + Offset;
501  switch (Type) {
502  default:
503    llvm_unreachable("Relocation type not implemented yet!");
504  break;
505  case ELF::R_PPC64_ADDR16_LO :
506    writeInt16BE(LocalAddress, applyPPClo (Value + Addend));
507    break;
508  case ELF::R_PPC64_ADDR16_HI :
509    writeInt16BE(LocalAddress, applyPPChi (Value + Addend));
510    break;
511  case ELF::R_PPC64_ADDR16_HIGHER :
512    writeInt16BE(LocalAddress, applyPPChigher (Value + Addend));
513    break;
514  case ELF::R_PPC64_ADDR16_HIGHEST :
515    writeInt16BE(LocalAddress, applyPPChighest (Value + Addend));
516    break;
517  case ELF::R_PPC64_ADDR14 : {
518    assert(((Value + Addend) & 3) == 0);
519    // Preserve the AA/LK bits in the branch instruction
520    uint8_t aalk = *(LocalAddress+3);
521    writeInt16BE(LocalAddress + 2, (aalk & 3) | ((Value + Addend) & 0xfffc));
522  } break;
523  case ELF::R_PPC64_ADDR32 : {
524    int32_t Result = static_cast<int32_t>(Value + Addend);
525    if (SignExtend32<32>(Result) != Result)
526      llvm_unreachable("Relocation R_PPC64_ADDR32 overflow");
527    writeInt32BE(LocalAddress, Result);
528  } break;
529  case ELF::R_PPC64_REL24 : {
530    uint64_t FinalAddress = (Section.LoadAddress + Offset);
531    int32_t delta = static_cast<int32_t>(Value - FinalAddress + Addend);
532    if (SignExtend32<24>(delta) != delta)
533      llvm_unreachable("Relocation R_PPC64_REL24 overflow");
534    // Generates a 'bl <address>' instruction
535    writeInt32BE(LocalAddress, 0x48000001 | (delta & 0x03FFFFFC));
536  } break;
537  case ELF::R_PPC64_REL32 : {
538    uint64_t FinalAddress = (Section.LoadAddress + Offset);
539    int32_t delta = static_cast<int32_t>(Value - FinalAddress + Addend);
540    if (SignExtend32<32>(delta) != delta)
541      llvm_unreachable("Relocation R_PPC64_REL32 overflow");
542    writeInt32BE(LocalAddress, delta);
543  } break;
544  case ELF::R_PPC64_ADDR64 :
545    writeInt64BE(LocalAddress, Value + Addend);
546    break;
547  case ELF::R_PPC64_TOC :
548    writeInt64BE(LocalAddress, findPPC64TOC());
549    break;
550  case ELF::R_PPC64_TOC16 : {
551    uint64_t TOCStart = findPPC64TOC();
552    Value = applyPPClo((Value + Addend) - TOCStart);
553    writeInt16BE(LocalAddress, applyPPClo(Value));
554  } break;
555  case ELF::R_PPC64_TOC16_DS : {
556    uint64_t TOCStart = findPPC64TOC();
557    Value = ((Value + Addend) - TOCStart);
558    writeInt16BE(LocalAddress, applyPPClo(Value));
559  } break;
560  }
561}
562
563void RuntimeDyldELF::resolveRelocation(const SectionEntry &Section,
564                                       uint64_t Offset,
565                                       uint64_t Value,
566                                       uint32_t Type,
567                                       int64_t Addend) {
568  switch (Arch) {
569  case Triple::x86_64:
570    resolveX86_64Relocation(Section, Offset, Value, Type, Addend);
571    break;
572  case Triple::x86:
573    resolveX86Relocation(Section, Offset,
574                         (uint32_t)(Value & 0xffffffffL), Type,
575                         (uint32_t)(Addend & 0xffffffffL));
576    break;
577  case Triple::arm:    // Fall through.
578  case Triple::thumb:
579    resolveARMRelocation(Section, Offset,
580                         (uint32_t)(Value & 0xffffffffL), Type,
581                         (uint32_t)(Addend & 0xffffffffL));
582    break;
583  case Triple::mips:    // Fall through.
584  case Triple::mipsel:
585    resolveMIPSRelocation(Section, Offset,
586                          (uint32_t)(Value & 0xffffffffL), Type,
587                          (uint32_t)(Addend & 0xffffffffL));
588    break;
589  case Triple::ppc64:
590    resolvePPC64Relocation(Section, Offset, Value, Type, Addend);
591    break;
592  default: llvm_unreachable("Unsupported CPU type!");
593  }
594}
595
596void RuntimeDyldELF::processRelocationRef(const ObjRelocationInfo &Rel,
597                                          ObjectImage &Obj,
598                                          ObjSectionToIDMap &ObjSectionToID,
599                                          const SymbolTableMap &Symbols,
600                                          StubMap &Stubs) {
601
602  uint32_t RelType = (uint32_t)(Rel.Type & 0xffffffffL);
603  intptr_t Addend = (intptr_t)Rel.AdditionalInfo;
604  const SymbolRef &Symbol = Rel.Symbol;
605
606  // Obtain the symbol name which is referenced in the relocation
607  StringRef TargetName;
608  Symbol.getName(TargetName);
609  DEBUG(dbgs() << "\t\tRelType: " << RelType
610               << " Addend: " << Addend
611               << " TargetName: " << TargetName
612               << "\n");
613  RelocationValueRef Value;
614  // First search for the symbol in the local symbol table
615  SymbolTableMap::const_iterator lsi = Symbols.find(TargetName.data());
616  SymbolRef::Type SymType;
617  Symbol.getType(SymType);
618  if (lsi != Symbols.end()) {
619    Value.SectionID = lsi->second.first;
620    Value.Addend = lsi->second.second;
621  } else {
622    // Search for the symbol in the global symbol table
623    SymbolTableMap::const_iterator gsi =
624        GlobalSymbolTable.find(TargetName.data());
625    if (gsi != GlobalSymbolTable.end()) {
626      Value.SectionID = gsi->second.first;
627      Value.Addend = gsi->second.second;
628    } else {
629      switch (SymType) {
630        case SymbolRef::ST_Debug: {
631          // TODO: Now ELF SymbolRef::ST_Debug = STT_SECTION, it's not obviously
632          // and can be changed by another developers. Maybe best way is add
633          // a new symbol type ST_Section to SymbolRef and use it.
634          section_iterator si(Obj.end_sections());
635          Symbol.getSection(si);
636          if (si == Obj.end_sections())
637            llvm_unreachable("Symbol section not found, bad object file format!");
638          DEBUG(dbgs() << "\t\tThis is section symbol\n");
639          // Default to 'true' in case isText fails (though it never does).
640          bool isCode = true;
641          si->isText(isCode);
642          Value.SectionID = findOrEmitSection(Obj,
643                                              (*si),
644                                              isCode,
645                                              ObjSectionToID);
646          Value.Addend = Addend;
647          break;
648        }
649        case SymbolRef::ST_Unknown: {
650          Value.SymbolName = TargetName.data();
651          Value.Addend = Addend;
652          break;
653        }
654        default:
655          llvm_unreachable("Unresolved symbol type!");
656          break;
657      }
658    }
659  }
660  DEBUG(dbgs() << "\t\tRel.SectionID: " << Rel.SectionID
661               << " Rel.Offset: " << Rel.Offset
662               << "\n");
663  if (Arch == Triple::arm &&
664      (RelType == ELF::R_ARM_PC24 ||
665       RelType == ELF::R_ARM_CALL ||
666       RelType == ELF::R_ARM_JUMP24)) {
667    // This is an ARM branch relocation, need to use a stub function.
668    DEBUG(dbgs() << "\t\tThis is an ARM branch relocation.");
669    SectionEntry &Section = Sections[Rel.SectionID];
670
671    // Look for an existing stub.
672    StubMap::const_iterator i = Stubs.find(Value);
673    if (i != Stubs.end()) {
674        resolveRelocation(Section, Rel.Offset,
675                          (uint64_t)Section.Address + i->second, RelType, 0);
676      DEBUG(dbgs() << " Stub function found\n");
677    } else {
678      // Create a new stub function.
679      DEBUG(dbgs() << " Create a new stub function\n");
680      Stubs[Value] = Section.StubOffset;
681      uint8_t *StubTargetAddr = createStubFunction(Section.Address +
682                                                   Section.StubOffset);
683      RelocationEntry RE(Rel.SectionID, StubTargetAddr - Section.Address,
684                         ELF::R_ARM_ABS32, Value.Addend);
685      if (Value.SymbolName)
686        addRelocationForSymbol(RE, Value.SymbolName);
687      else
688        addRelocationForSection(RE, Value.SectionID);
689
690      resolveRelocation(Section, Rel.Offset,
691                        (uint64_t)Section.Address + Section.StubOffset,
692                        RelType, 0);
693      Section.StubOffset += getMaxStubSize();
694    }
695  } else if ((Arch == Triple::mipsel || Arch == Triple::mips) &&
696             RelType == ELF::R_MIPS_26) {
697    // This is an Mips branch relocation, need to use a stub function.
698    DEBUG(dbgs() << "\t\tThis is a Mips branch relocation.");
699    SectionEntry &Section = Sections[Rel.SectionID];
700    uint8_t *Target = Section.Address + Rel.Offset;
701    uint32_t *TargetAddress = (uint32_t *)Target;
702
703    // Extract the addend from the instruction.
704    uint32_t Addend = ((*TargetAddress) & 0x03ffffff) << 2;
705
706    Value.Addend += Addend;
707
708    //  Look up for existing stub.
709    StubMap::const_iterator i = Stubs.find(Value);
710    if (i != Stubs.end()) {
711      resolveRelocation(Section, Rel.Offset,
712                        (uint64_t)Section.Address + i->second, RelType, 0);
713      DEBUG(dbgs() << " Stub function found\n");
714    } else {
715      // Create a new stub function.
716      DEBUG(dbgs() << " Create a new stub function\n");
717      Stubs[Value] = Section.StubOffset;
718      uint8_t *StubTargetAddr = createStubFunction(Section.Address +
719                                                   Section.StubOffset);
720
721      // Creating Hi and Lo relocations for the filled stub instructions.
722      RelocationEntry REHi(Rel.SectionID,
723                           StubTargetAddr - Section.Address,
724                           ELF::R_MIPS_HI16, Value.Addend);
725      RelocationEntry RELo(Rel.SectionID,
726                           StubTargetAddr - Section.Address + 4,
727                           ELF::R_MIPS_LO16, Value.Addend);
728
729      if (Value.SymbolName) {
730        addRelocationForSymbol(REHi, Value.SymbolName);
731        addRelocationForSymbol(RELo, Value.SymbolName);
732      } else {
733        addRelocationForSection(REHi, Value.SectionID);
734        addRelocationForSection(RELo, Value.SectionID);
735      }
736
737      resolveRelocation(Section, Rel.Offset,
738                        (uint64_t)Section.Address + Section.StubOffset,
739                        RelType, 0);
740      Section.StubOffset += getMaxStubSize();
741    }
742  } else if (Arch == Triple::ppc64) {
743    if (RelType == ELF::R_PPC64_REL24) {
744      // A PPC branch relocation will need a stub function if the target is
745      // an external symbol (Symbol::ST_Unknown) or if the target address
746      // is not within the signed 24-bits branch address.
747      SectionEntry &Section = Sections[Rel.SectionID];
748      uint8_t *Target = Section.Address + Rel.Offset;
749      bool RangeOverflow = false;
750      if (SymType != SymbolRef::ST_Unknown) {
751        // A function call may points to the .opd entry, so the final symbol value
752        // in calculated based in the relocation values in .opd section.
753        findOPDEntrySection(Obj, ObjSectionToID, Value);
754        uint8_t *RelocTarget = Sections[Value.SectionID].Address + Value.Addend;
755        int32_t delta = static_cast<int32_t>(Target - RelocTarget);
756        // If it is within 24-bits branch range, just set the branch target
757        if (SignExtend32<24>(delta) == delta) {
758          RelocationEntry RE(Rel.SectionID, Rel.Offset, RelType, Value.Addend);
759          if (Value.SymbolName)
760            addRelocationForSymbol(RE, Value.SymbolName);
761          else
762            addRelocationForSection(RE, Value.SectionID);
763        } else {
764          RangeOverflow = true;
765        }
766      }
767      if (SymType == SymbolRef::ST_Unknown || RangeOverflow == true) {
768        // It is an external symbol (SymbolRef::ST_Unknown) or within a range
769        // larger than 24-bits.
770        StubMap::const_iterator i = Stubs.find(Value);
771        if (i != Stubs.end()) {
772          // Symbol function stub already created, just relocate to it
773          resolveRelocation(Section, Rel.Offset,
774                            (uint64_t)Section.Address + i->second, RelType, 0);
775          DEBUG(dbgs() << " Stub function found\n");
776        } else {
777          // Create a new stub function.
778          DEBUG(dbgs() << " Create a new stub function\n");
779          Stubs[Value] = Section.StubOffset;
780          uint8_t *StubTargetAddr = createStubFunction(Section.Address +
781                                                       Section.StubOffset);
782          RelocationEntry RE(Rel.SectionID, StubTargetAddr - Section.Address,
783                             ELF::R_PPC64_ADDR64, Value.Addend);
784
785          // Generates the 64-bits address loads as exemplified in section
786          // 4.5.1 in PPC64 ELF ABI.
787          RelocationEntry REhst(Rel.SectionID,
788                                StubTargetAddr - Section.Address + 2,
789                                ELF::R_PPC64_ADDR16_HIGHEST, Value.Addend);
790          RelocationEntry REhr(Rel.SectionID,
791                               StubTargetAddr - Section.Address + 6,
792                               ELF::R_PPC64_ADDR16_HIGHER, Value.Addend);
793          RelocationEntry REh(Rel.SectionID,
794                              StubTargetAddr - Section.Address + 14,
795                              ELF::R_PPC64_ADDR16_HI, Value.Addend);
796          RelocationEntry REl(Rel.SectionID,
797                              StubTargetAddr - Section.Address + 18,
798                              ELF::R_PPC64_ADDR16_LO, Value.Addend);
799
800          if (Value.SymbolName) {
801            addRelocationForSymbol(REhst, Value.SymbolName);
802            addRelocationForSymbol(REhr,  Value.SymbolName);
803            addRelocationForSymbol(REh,   Value.SymbolName);
804            addRelocationForSymbol(REl,   Value.SymbolName);
805          } else {
806            addRelocationForSection(REhst, Value.SectionID);
807            addRelocationForSection(REhr,  Value.SectionID);
808            addRelocationForSection(REh,   Value.SectionID);
809            addRelocationForSection(REl,   Value.SectionID);
810          }
811
812          resolveRelocation(Section, Rel.Offset,
813                            (uint64_t)Section.Address + Section.StubOffset,
814                            RelType, 0);
815          if (SymType == SymbolRef::ST_Unknown)
816            // Restore the TOC for external calls
817            writeInt32BE(Target+4, 0xE8410028); // ld r2,40(r1)
818          Section.StubOffset += getMaxStubSize();
819        }
820      }
821    } else {
822      RelocationEntry RE(Rel.SectionID, Rel.Offset, RelType, Value.Addend);
823      // Extra check to avoid relocation againt empty symbols (usually
824      // the R_PPC64_TOC).
825      if (Value.SymbolName && !TargetName.empty())
826        addRelocationForSymbol(RE, Value.SymbolName);
827      else
828        addRelocationForSection(RE, Value.SectionID);
829    }
830  } else {
831    RelocationEntry RE(Rel.SectionID, Rel.Offset, RelType, Value.Addend);
832    if (Value.SymbolName)
833      addRelocationForSymbol(RE, Value.SymbolName);
834    else
835      addRelocationForSection(RE, Value.SectionID);
836  }
837}
838
839unsigned RuntimeDyldELF::getCommonSymbolAlignment(const SymbolRef &Sym) {
840  // In ELF, the value of an SHN_COMMON symbol is its alignment requirement.
841  uint64_t Align;
842  Check(Sym.getValue(Align));
843  return Align;
844}
845
846bool RuntimeDyldELF::isCompatibleFormat(const ObjectBuffer *Buffer) const {
847  if (Buffer->getBufferSize() < strlen(ELF::ElfMagic))
848    return false;
849  return (memcmp(Buffer->getBufferStart(), ELF::ElfMagic, strlen(ELF::ElfMagic))) == 0;
850}
851} // namespace llvm
852