RuntimeDyldMachO.cpp revision b83a67e1e3fe210bd99a82eccd3dc5b1b44f1503 
1//===-- RuntimeDyldMachO.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 the MC-JIT runtime dynamic linker.
11//
12//===----------------------------------------------------------------------===//
13
14#define DEBUG_TYPE "dyld"
15#include "llvm/ADT/OwningPtr.h"
16#include "llvm/ADT/StringRef.h"
17#include "llvm/ADT/STLExtras.h"
18#include "RuntimeDyldMachO.h"
19using namespace llvm;
20using namespace llvm::object;
21
22namespace llvm {
23
24bool RuntimeDyldMachO::
25resolveRelocation(uint8_t *Address, uint64_t Value, bool isPCRel,
26                  unsigned Type, unsigned Size, int64_t Addend) {
27  // This just dispatches to the proper target specific routine.
28  switch (CPUType) {
29  default: llvm_unreachable("Unsupported CPU type!");
30  case mach::CTM_x86_64:
31    return resolveX86_64Relocation((uintptr_t)Address, (uintptr_t)Value,
32                                   isPCRel, Type, Size, Addend);
33  case mach::CTM_ARM:
34    return resolveARMRelocation((uintptr_t)Address, (uintptr_t)Value,
35                                isPCRel, Type, Size, Addend);
36  }
37  llvm_unreachable("");
38}
39
40bool RuntimeDyldMachO::
41resolveX86_64Relocation(uintptr_t Address, uintptr_t Value, bool isPCRel,
42                        unsigned Type, unsigned Size, int64_t Addend) {
43  // If the relocation is PC-relative, the value to be encoded is the
44  // pointer difference.
45  if (isPCRel)
46    // FIXME: It seems this value needs to be adjusted by 4 for an effective PC
47    // address. Is that expected? Only for branches, perhaps?
48    Value -= Address + 4;
49
50  switch(Type) {
51  default:
52    llvm_unreachable("Invalid relocation type!");
53  case macho::RIT_X86_64_Signed1:
54  case macho::RIT_X86_64_Signed2:
55  case macho::RIT_X86_64_Signed4:
56  case macho::RIT_X86_64_Signed:
57  case macho::RIT_X86_64_Unsigned:
58  case macho::RIT_X86_64_Branch: {
59    Value += Addend;
60    // Mask in the target value a byte at a time (we don't have an alignment
61    // guarantee for the target address, so this is safest).
62    uint8_t *p = (uint8_t*)Address;
63    for (unsigned i = 0; i < Size; ++i) {
64      *p++ = (uint8_t)Value;
65      Value >>= 8;
66    }
67    return false;
68  }
69  case macho::RIT_X86_64_GOTLoad:
70  case macho::RIT_X86_64_GOT:
71  case macho::RIT_X86_64_Subtractor:
72  case macho::RIT_X86_64_TLV:
73    return Error("Relocation type not implemented yet!");
74  }
75}
76
77bool RuntimeDyldMachO::
78resolveARMRelocation(uintptr_t Address, uintptr_t Value, bool isPCRel,
79                     unsigned Type, unsigned Size, int64_t Addend) {
80  // If the relocation is PC-relative, the value to be encoded is the
81  // pointer difference.
82  if (isPCRel) {
83    Value -= Address;
84    // ARM PCRel relocations have an effective-PC offset of two instructions
85    // (four bytes in Thumb mode, 8 bytes in ARM mode).
86    // FIXME: For now, assume ARM mode.
87    Value -= 8;
88  }
89
90  switch(Type) {
91  default:
92    llvm_unreachable("Invalid relocation type!");
93  case macho::RIT_Vanilla: {
94    // Mask in the target value a byte at a time (we don't have an alignment
95    // guarantee for the target address, so this is safest).
96    uint8_t *p = (uint8_t*)Address;
97    for (unsigned i = 0; i < Size; ++i) {
98      *p++ = (uint8_t)Value;
99      Value >>= 8;
100    }
101    break;
102  }
103  case macho::RIT_ARM_Branch24Bit: {
104    // Mask the value into the target address. We know instructions are
105    // 32-bit aligned, so we can do it all at once.
106    uint32_t *p = (uint32_t*)Address;
107    // The low two bits of the value are not encoded.
108    Value >>= 2;
109    // Mask the value to 24 bits.
110    Value &= 0xffffff;
111    // FIXME: If the destination is a Thumb function (and the instruction
112    // is a non-predicated BL instruction), we need to change it to a BLX
113    // instruction instead.
114
115    // Insert the value into the instruction.
116    *p = (*p & ~0xffffff) | Value;
117    break;
118  }
119  case macho::RIT_ARM_ThumbBranch22Bit:
120  case macho::RIT_ARM_ThumbBranch32Bit:
121  case macho::RIT_ARM_Half:
122  case macho::RIT_ARM_HalfDifference:
123  case macho::RIT_Pair:
124  case macho::RIT_Difference:
125  case macho::RIT_ARM_LocalDifference:
126  case macho::RIT_ARM_PreboundLazyPointer:
127    return Error("Relocation type not implemented yet!");
128  }
129  return false;
130}
131
132bool RuntimeDyldMachO::
133loadSegment32(const MachOObject *Obj,
134              const MachOObject::LoadCommandInfo *SegmentLCI,
135              const InMemoryStruct<macho::SymtabLoadCommand> &SymtabLC) {
136  // FIXME: This should really be combined w/ loadSegment64. Templatized
137  // function on the 32/64 datatypes maybe?
138  InMemoryStruct<macho::SegmentLoadCommand> SegmentLC;
139  Obj->ReadSegmentLoadCommand(*SegmentLCI, SegmentLC);
140  if (!SegmentLC)
141    return Error("unable to load segment load command");
142
143
144  SmallVector<unsigned, 16> SectionMap;
145  for (unsigned SectNum = 0; SectNum != SegmentLC->NumSections; ++SectNum) {
146    InMemoryStruct<macho::Section> Sect;
147    Obj->ReadSection(*SegmentLCI, SectNum, Sect);
148    if (!Sect)
149      return Error("unable to load section: '" + Twine(SectNum) + "'");
150
151    // Allocate memory via the MM for the section.
152    uint8_t *Buffer;
153    uint32_t SectionID = Sections.size();
154    if (Sect->Flags != 0x80000400)
155      Buffer = MemMgr->allocateCodeSection(Sect->Size, Sect->Align, SectionID);
156    else
157      Buffer = MemMgr->allocateDataSection(Sect->Size, Sect->Align, SectionID);
158
159    DEBUG(dbgs() << "Loading "
160                 << ((Sect->Flags == 0x80000400) ? "text" : "data")
161                 << " (ID #" << SectionID << ")"
162                 << " '" << Sect->SegmentName << ","
163                 << Sect->Name << "' of size " << Sect->Size
164                 << " to address " << Buffer << ".\n");
165
166    // Copy the payload from the object file into the allocated buffer.
167    uint8_t *Base = (uint8_t*)Obj->getData(SegmentLC->FileOffset,
168                                           SegmentLC->FileSize).data();
169    memcpy(Buffer, Base + Sect->Address, Sect->Size);
170
171    // Remember what got allocated for this SectionID.
172    Sections.push_back(sys::MemoryBlock(Buffer, Sect->Size));
173    SectionLocalMemToID[Buffer] = SectionID;
174
175    // By default, the load address of a section is its memory buffer.
176    SectionLoadAddress.push_back((uint64_t)Buffer);
177
178    // Keep a map of object file section numbers to corresponding SectionIDs
179    // while processing the file.
180    SectionMap.push_back(SectionID);
181  }
182
183  // Process the symbol table.
184  SmallVector<StringRef, 64> SymbolNames;
185  processSymbols32(Obj, SectionMap, SymbolNames, SymtabLC);
186
187  // Process the relocations for each section we're loading.
188  Relocations.grow(Relocations.size() + SegmentLC->NumSections);
189  for (unsigned SectNum = 0; SectNum != SegmentLC->NumSections; ++SectNum) {
190    InMemoryStruct<macho::Section> Sect;
191    Obj->ReadSection(*SegmentLCI, SectNum, Sect);
192    if (!Sect)
193      return Error("unable to load section: '" + Twine(SectNum) + "'");
194    for (unsigned j = 0; j != Sect->NumRelocationTableEntries; ++j) {
195      InMemoryStruct<macho::RelocationEntry> RE;
196      Obj->ReadRelocationEntry(Sect->RelocationTableOffset, j, RE);
197      if (RE->Word0 & macho::RF_Scattered)
198        return Error("NOT YET IMPLEMENTED: scattered relocations.");
199      // Word0 of the relocation is the offset into the section where the
200      // relocation should be applied. We need to translate that into an
201      // offset into a function since that's our atom.
202      uint32_t Offset = RE->Word0;
203      bool isExtern = (RE->Word1 >> 27) & 1;
204
205      // FIXME: Get the relocation addend from the target address.
206      // FIXME: VERY imporant for internal relocations.
207
208      // Figure out the source symbol of the relocation. If isExtern is true,
209      // this relocation references the symbol table, otherwise it references
210      // a section in the same object, numbered from 1 through NumSections
211      // (SectionBases is [0, NumSections-1]).
212      uint32_t SourceNum = RE->Word1 & 0xffffff; // 24-bit value
213      if (!isExtern) {
214        assert(SourceNum > 0 && "Invalid relocation section number!");
215        unsigned SectionID = SectionMap[SourceNum - 1];
216        unsigned TargetID = SectionMap[SectNum];
217        DEBUG(dbgs() << "Internal relocation at Section #"
218                     << TargetID << " + " << Offset
219                     << " from Section #"
220                     << SectionID << " (Word1: "
221                     << format("0x%x", RE->Word1) << ")\n");
222
223        // Store the relocation information. It will get resolved when
224        // the section addresses are assigned.
225        Relocations[SectionID].push_back(RelocationEntry(TargetID,
226                                                         Offset,
227                                                         RE->Word1,
228                                                         0 /*Addend*/));
229      } else {
230        StringRef SourceName = SymbolNames[SourceNum];
231
232        // Now store the relocation information. Associate it with the source
233        // symbol. Just add it to the unresolved list and let the general
234        // path post-load resolve it if we know where the symbol is.
235        UnresolvedRelocations[SourceName].push_back(RelocationEntry(SectNum,
236                                                                    Offset,
237                                                                    RE->Word1,
238                                                                 0 /*Addend*/));
239        DEBUG(dbgs() << "Relocation at Section #" << SectNum << " + " << Offset
240              << " from '" << SourceName << "(Word1: "
241              << format("0x%x", RE->Word1) << ")\n");
242      }
243    }
244  }
245
246  // Resolve the addresses of any symbols that were defined in this segment.
247  for (int i = 0, e = SymbolNames.size(); i != e; ++i)
248    resolveSymbol(SymbolNames[i]);
249
250  return false;
251}
252
253
254bool RuntimeDyldMachO::
255loadSegment64(const MachOObject *Obj,
256              const MachOObject::LoadCommandInfo *SegmentLCI,
257              const InMemoryStruct<macho::SymtabLoadCommand> &SymtabLC) {
258  InMemoryStruct<macho::Segment64LoadCommand> Segment64LC;
259  Obj->ReadSegment64LoadCommand(*SegmentLCI, Segment64LC);
260  if (!Segment64LC)
261    return Error("unable to load segment load command");
262
263
264  SmallVector<unsigned, 16> SectionMap;
265  for (unsigned SectNum = 0; SectNum != Segment64LC->NumSections; ++SectNum) {
266    InMemoryStruct<macho::Section64> Sect;
267    Obj->ReadSection64(*SegmentLCI, SectNum, Sect);
268    if (!Sect)
269      return Error("unable to load section: '" + Twine(SectNum) + "'");
270
271    // Allocate memory via the MM for the section.
272    uint8_t *Buffer;
273    uint32_t SectionID = Sections.size();
274    unsigned Align = 1 << Sect->Align; // .o file has log2 alignment.
275    if (Sect->Flags == 0x80000400)
276      Buffer = MemMgr->allocateCodeSection(Sect->Size, Align, SectionID);
277    else
278      Buffer = MemMgr->allocateDataSection(Sect->Size, Align, SectionID);
279
280    DEBUG(dbgs() << "Loading "
281                 << ((Sect->Flags == 0x80000400) ? "text" : "data")
282                 << " (ID #" << SectionID << ")"
283                 << " '" << Sect->SegmentName << ","
284                 << Sect->Name << "' of size " << Sect->Size
285                 << " (align " << Align << ")"
286                 << " to address " << Buffer << ".\n");
287
288    // Copy the payload from the object file into the allocated buffer.
289    uint8_t *Base = (uint8_t*)Obj->getData(Segment64LC->FileOffset,
290                                           Segment64LC->FileSize).data();
291    memcpy(Buffer, Base + Sect->Address, Sect->Size);
292
293    // Remember what got allocated for this SectionID.
294    Sections.push_back(sys::MemoryBlock(Buffer, Sect->Size));
295    SectionLocalMemToID[Buffer] = SectionID;
296
297    // By default, the load address of a section is its memory buffer.
298    SectionLoadAddress.push_back((uint64_t)Buffer);
299
300    // Keep a map of object file section numbers to corresponding SectionIDs
301    // while processing the file.
302    SectionMap.push_back(SectionID);
303  }
304
305  // Process the symbol table.
306  SmallVector<StringRef, 64> SymbolNames;
307  processSymbols64(Obj, SectionMap, SymbolNames, SymtabLC);
308
309  // Process the relocations for each section we're loading.
310  Relocations.grow(Relocations.size() + Segment64LC->NumSections);
311  for (unsigned SectNum = 0; SectNum != Segment64LC->NumSections; ++SectNum) {
312    InMemoryStruct<macho::Section64> Sect;
313    Obj->ReadSection64(*SegmentLCI, SectNum, Sect);
314    if (!Sect)
315      return Error("unable to load section: '" + Twine(SectNum) + "'");
316    for (unsigned j = 0; j != Sect->NumRelocationTableEntries; ++j) {
317      InMemoryStruct<macho::RelocationEntry> RE;
318      Obj->ReadRelocationEntry(Sect->RelocationTableOffset, j, RE);
319      if (RE->Word0 & macho::RF_Scattered)
320        return Error("NOT YET IMPLEMENTED: scattered relocations.");
321      // Word0 of the relocation is the offset into the section where the
322      // relocation should be applied. We need to translate that into an
323      // offset into a function since that's our atom.
324      uint32_t Offset = RE->Word0;
325      bool isExtern = (RE->Word1 >> 27) & 1;
326
327      // FIXME: Get the relocation addend from the target address.
328      // FIXME: VERY imporant for internal relocations.
329
330      // Figure out the source symbol of the relocation. If isExtern is true,
331      // this relocation references the symbol table, otherwise it references
332      // a section in the same object, numbered from 1 through NumSections
333      // (SectionBases is [0, NumSections-1]).
334      uint32_t SourceNum = RE->Word1 & 0xffffff; // 24-bit value
335      if (!isExtern) {
336        assert(SourceNum > 0 && "Invalid relocation section number!");
337        unsigned SectionID = SectionMap[SourceNum - 1];
338        unsigned TargetID = SectionMap[SectNum];
339        DEBUG(dbgs() << "Internal relocation at Section #"
340                     << TargetID << " + " << Offset
341                     << " from Section #"
342                     << SectionID << " (Word1: "
343                     << format("0x%x", RE->Word1) << ")\n");
344
345        // Store the relocation information. It will get resolved when
346        // the section addresses are assigned.
347        Relocations[SectionID].push_back(RelocationEntry(TargetID,
348                                                         Offset,
349                                                         RE->Word1,
350                                                         0 /*Addend*/));
351      } else {
352        StringRef SourceName = SymbolNames[SourceNum];
353
354        // Now store the relocation information. Associate it with the source
355        // symbol. Just add it to the unresolved list and let the general
356        // path post-load resolve it if we know where the symbol is.
357        UnresolvedRelocations[SourceName].push_back(RelocationEntry(SectNum,
358                                                                    Offset,
359                                                                    RE->Word1,
360                                                                 0 /*Addend*/));
361        DEBUG(dbgs() << "Relocation at Section #" << SectNum << " + " << Offset
362              << " from '" << SourceName << "(Word1: "
363              << format("0x%x", RE->Word1) << ")\n");
364      }
365    }
366  }
367
368  // Resolve the addresses of any symbols that were defined in this segment.
369  for (int i = 0, e = SymbolNames.size(); i != e; ++i)
370    resolveSymbol(SymbolNames[i]);
371
372  return false;
373}
374
375bool RuntimeDyldMachO::
376processSymbols32(const MachOObject *Obj,
377                 SmallVectorImpl<unsigned> &SectionMap,
378                 SmallVectorImpl<StringRef> &SymbolNames,
379                 const InMemoryStruct<macho::SymtabLoadCommand> &SymtabLC) {
380  // FIXME: Combine w/ processSymbols64. Factor 64/32 datatype and such.
381  for (unsigned i = 0; i != SymtabLC->NumSymbolTableEntries; ++i) {
382    InMemoryStruct<macho::SymbolTableEntry> STE;
383    Obj->ReadSymbolTableEntry(SymtabLC->SymbolTableOffset, i, STE);
384    if (!STE)
385      return Error("unable to read symbol: '" + Twine(i) + "'");
386    // Get the symbol name.
387    StringRef Name = Obj->getStringAtIndex(STE->StringIndex);
388    SymbolNames.push_back(Name);
389
390    // FIXME: Check the symbol type and flags.
391    if (STE->Type != 0xF)  // external, defined in this segment.
392      continue;
393    // Flags in the upper nibble we don't care about.
394    if ((STE->Flags & 0xf) != 0x0)
395      continue;
396
397    // Remember the symbol.
398    uint32_t SectionID = SectionMap[STE->SectionIndex - 1];
399    SymbolTable[Name] = SymbolLoc(SectionID, STE->Value);
400
401    DEBUG(dbgs() << "Symbol: '" << Name << "' @ "
402                 << (getSectionAddress(SectionID) + STE->Value)
403                 << "\n");
404  }
405  return false;
406}
407
408bool RuntimeDyldMachO::
409processSymbols64(const MachOObject *Obj,
410                 SmallVectorImpl<unsigned> &SectionMap,
411                 SmallVectorImpl<StringRef> &SymbolNames,
412                 const InMemoryStruct<macho::SymtabLoadCommand> &SymtabLC) {
413  for (unsigned i = 0; i != SymtabLC->NumSymbolTableEntries; ++i) {
414    InMemoryStruct<macho::Symbol64TableEntry> STE;
415    Obj->ReadSymbol64TableEntry(SymtabLC->SymbolTableOffset, i, STE);
416    if (!STE)
417      return Error("unable to read symbol: '" + Twine(i) + "'");
418    // Get the symbol name.
419    StringRef Name = Obj->getStringAtIndex(STE->StringIndex);
420    SymbolNames.push_back(Name);
421
422    // FIXME: Check the symbol type and flags.
423    if (STE->Type != 0xF)  // external, defined in this segment.
424      continue;
425    // Flags in the upper nibble we don't care about.
426    if ((STE->Flags & 0xf) != 0x0)
427      continue;
428
429    // Remember the symbol.
430    uint32_t SectionID = SectionMap[STE->SectionIndex - 1];
431    SymbolTable[Name] = SymbolLoc(SectionID, STE->Value);
432
433    DEBUG(dbgs() << "Symbol: '" << Name << "' @ "
434                 << (getSectionAddress(SectionID) + STE->Value)
435                 << "\n");
436  }
437  return false;
438}
439
440// resolveSymbol - Resolve any relocations to the specified symbol if
441// we know where it lives.
442void RuntimeDyldMachO::resolveSymbol(StringRef Name) {
443  StringMap<SymbolLoc>::const_iterator Loc = SymbolTable.find(Name);
444  if (Loc == SymbolTable.end())
445    return;
446
447  RelocationList &Relocs = UnresolvedRelocations[Name];
448  DEBUG(dbgs() << "Resolving symbol '" << Name << "'\n");
449  for (int i = 0, e = Relocs.size(); i != e; ++i) {
450    // Change the relocation to be section relative rather than symbol
451    // relative and move it to the resolved relocation list.
452    RelocationEntry Entry = Relocs[i];
453    Entry.Addend += Loc->second.second;
454    Relocations[Loc->second.first].push_back(Entry);
455  }
456  // FIXME: Keep a worklist of the relocations we've added so that we can
457  // resolve more selectively later.
458  Relocs.clear();
459}
460
461bool RuntimeDyldMachO::loadObject(MemoryBuffer *InputBuffer) {
462  // If the linker is in an error state, don't do anything.
463  if (hasError())
464    return true;
465  // Load the Mach-O wrapper object.
466  std::string ErrorStr;
467  OwningPtr<MachOObject> Obj(
468    MachOObject::LoadFromBuffer(InputBuffer, &ErrorStr));
469  if (!Obj)
470    return Error("unable to load object: '" + ErrorStr + "'");
471
472  // Get the CPU type information from the header.
473  const macho::Header &Header = Obj->getHeader();
474
475  // FIXME: Error checking that the loaded object is compatible with
476  //        the system we're running on.
477  CPUType = Header.CPUType;
478  CPUSubtype = Header.CPUSubtype;
479
480  // Validate that the load commands match what we expect.
481  const MachOObject::LoadCommandInfo *SegmentLCI = 0, *SymtabLCI = 0,
482    *DysymtabLCI = 0;
483  for (unsigned i = 0; i != Header.NumLoadCommands; ++i) {
484    const MachOObject::LoadCommandInfo &LCI = Obj->getLoadCommandInfo(i);
485    switch (LCI.Command.Type) {
486    case macho::LCT_Segment:
487    case macho::LCT_Segment64:
488      if (SegmentLCI)
489        return Error("unexpected input object (multiple segments)");
490      SegmentLCI = &LCI;
491      break;
492    case macho::LCT_Symtab:
493      if (SymtabLCI)
494        return Error("unexpected input object (multiple symbol tables)");
495      SymtabLCI = &LCI;
496      break;
497    case macho::LCT_Dysymtab:
498      if (DysymtabLCI)
499        return Error("unexpected input object (multiple symbol tables)");
500      DysymtabLCI = &LCI;
501      break;
502    default:
503      return Error("unexpected input object (unexpected load command");
504    }
505  }
506
507  if (!SymtabLCI)
508    return Error("no symbol table found in object");
509  if (!SegmentLCI)
510    return Error("no segments found in object");
511
512  // Read and register the symbol table data.
513  InMemoryStruct<macho::SymtabLoadCommand> SymtabLC;
514  Obj->ReadSymtabLoadCommand(*SymtabLCI, SymtabLC);
515  if (!SymtabLC)
516    return Error("unable to load symbol table load command");
517  Obj->RegisterStringTable(*SymtabLC);
518
519  // Read the dynamic link-edit information, if present (not present in static
520  // objects).
521  if (DysymtabLCI) {
522    InMemoryStruct<macho::DysymtabLoadCommand> DysymtabLC;
523    Obj->ReadDysymtabLoadCommand(*DysymtabLCI, DysymtabLC);
524    if (!DysymtabLC)
525      return Error("unable to load dynamic link-exit load command");
526
527    // FIXME: We don't support anything interesting yet.
528//    if (DysymtabLC->LocalSymbolsIndex != 0)
529//      return Error("NOT YET IMPLEMENTED: local symbol entries");
530//    if (DysymtabLC->ExternalSymbolsIndex != 0)
531//      return Error("NOT YET IMPLEMENTED: non-external symbol entries");
532//    if (DysymtabLC->UndefinedSymbolsIndex != SymtabLC->NumSymbolTableEntries)
533//      return Error("NOT YET IMPLEMENTED: undefined symbol entries");
534  }
535
536  // Load the segment load command.
537  if (SegmentLCI->Command.Type == macho::LCT_Segment) {
538    if (loadSegment32(Obj.get(), SegmentLCI, SymtabLC))
539      return true;
540  } else {
541    if (loadSegment64(Obj.get(), SegmentLCI, SymtabLC))
542      return true;
543  }
544
545  // Assign the addresses of the sections from the object so that any
546  // relocations to them get set properly.
547  // FIXME: This is done directly from the client at the moment. We should
548  // default the values to the local storage, at least when the target arch
549  // is the same as the host arch.
550
551  return false;
552}
553
554// Assign an address to a symbol name and resolve all the relocations
555// associated with it.
556void RuntimeDyldMachO::reassignSectionAddress(unsigned SectionID,
557                                              uint64_t Addr) {
558  // The address to use for relocation resolution is not
559  // the address of the local section buffer. We must be doing
560  // a remote execution environment of some sort. Re-apply any
561  // relocations referencing this section with the given address.
562  //
563  // Addr is a uint64_t because we can't assume the pointer width
564  // of the target is the same as that of the host. Just use a generic
565  // "big enough" type.
566
567  SectionLoadAddress[SectionID] = Addr;
568
569  RelocationList &Relocs = Relocations[SectionID];
570  for (unsigned i = 0, e = Relocs.size(); i != e; ++i) {
571    RelocationEntry &RE = Relocs[i];
572    uint8_t *Target = (uint8_t*)Sections[RE.SectionID].base() + RE.Offset;
573    bool isPCRel = (RE.Data >> 24) & 1;
574    unsigned Type = (RE.Data >> 28) & 0xf;
575    unsigned Size = 1 << ((RE.Data >> 25) & 3);
576
577    DEBUG(dbgs() << "Resolving relocation at Section #" << RE.SectionID
578          << " + " << RE.Offset << " (" << format("%p", Target) << ")"
579          << " from Section #" << SectionID << " (" << format("%p", Addr) << ")"
580          << "(" << (isPCRel ? "pcrel" : "absolute")
581          << ", type: " << Type << ", Size: " << Size << ", Addend: "
582          << RE.Addend << ").\n");
583
584    resolveRelocation(Target, Addr, isPCRel, Type, Size, RE.Addend);
585  }
586}
587
588bool RuntimeDyldMachO::isKnownFormat(const MemoryBuffer *InputBuffer) {
589  StringRef Magic = InputBuffer->getBuffer().slice(0, 4);
590  if (Magic == "\xFE\xED\xFA\xCE") return true;
591  if (Magic == "\xCE\xFA\xED\xFE") return true;
592  if (Magic == "\xFE\xED\xFA\xCF") return true;
593  if (Magic == "\xCF\xFA\xED\xFE") return true;
594  return false;
595}
596
597} // end namespace llvm
598