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 #include "RuntimeDyldMachO.h"
15 #include "Targets/RuntimeDyldMachOAArch64.h"
16 #include "Targets/RuntimeDyldMachOARM.h"
17 #include "Targets/RuntimeDyldMachOI386.h"
18 #include "Targets/RuntimeDyldMachOX86_64.h"
19 #include "llvm/ADT/STLExtras.h"
20 #include "llvm/ADT/StringRef.h"
21 
22 using namespace llvm;
23 using namespace llvm::object;
24 
25 #define DEBUG_TYPE "dyld"
26 
27 namespace {
28 
29 class LoadedMachOObjectInfo
30     : public RuntimeDyld::LoadedObjectInfoHelper<LoadedMachOObjectInfo> {
31 public:
32   LoadedMachOObjectInfo(RuntimeDyldImpl &RTDyld, unsigned BeginIdx,
33                         unsigned EndIdx)
34       : LoadedObjectInfoHelper(RTDyld, BeginIdx, EndIdx) {}
35 
36   OwningBinary<ObjectFile>
37   getObjectForDebug(const ObjectFile &Obj) const override {
38     return OwningBinary<ObjectFile>();
39   }
40 };
41 
42 }
43 
44 namespace llvm {
45 
46 int64_t RuntimeDyldMachO::memcpyAddend(const RelocationEntry &RE) const {
47   unsigned NumBytes = 1 << RE.Size;
48   uint8_t *Src = Sections[RE.SectionID].Address + RE.Offset;
49 
50   return static_cast<int64_t>(readBytesUnaligned(Src, NumBytes));
51 }
52 
53 RelocationValueRef RuntimeDyldMachO::getRelocationValueRef(
54     const ObjectFile &BaseTObj, const relocation_iterator &RI,
55     const RelocationEntry &RE, ObjSectionToIDMap &ObjSectionToID) {
56 
57   const MachOObjectFile &Obj =
58       static_cast<const MachOObjectFile &>(BaseTObj);
59   MachO::any_relocation_info RelInfo =
60       Obj.getRelocation(RI->getRawDataRefImpl());
61   RelocationValueRef Value;
62 
63   bool IsExternal = Obj.getPlainRelocationExternal(RelInfo);
64   if (IsExternal) {
65     symbol_iterator Symbol = RI->getSymbol();
66     ErrorOr<StringRef> TargetNameOrErr = Symbol->getName();
67     if (std::error_code EC = TargetNameOrErr.getError())
68       report_fatal_error(EC.message());
69     StringRef TargetName = *TargetNameOrErr;
70     RTDyldSymbolTable::const_iterator SI =
71       GlobalSymbolTable.find(TargetName.data());
72     if (SI != GlobalSymbolTable.end()) {
73       const auto &SymInfo = SI->second;
74       Value.SectionID = SymInfo.getSectionID();
75       Value.Offset = SymInfo.getOffset() + RE.Addend;
76     } else {
77       Value.SymbolName = TargetName.data();
78       Value.Offset = RE.Addend;
79     }
80   } else {
81     SectionRef Sec = Obj.getAnyRelocationSection(RelInfo);
82     bool IsCode = Sec.isText();
83     Value.SectionID = findOrEmitSection(Obj, Sec, IsCode, ObjSectionToID);
84     uint64_t Addr = Sec.getAddress();
85     Value.Offset = RE.Addend - Addr;
86   }
87 
88   return Value;
89 }
90 
91 void RuntimeDyldMachO::makeValueAddendPCRel(RelocationValueRef &Value,
92                                             const relocation_iterator &RI,
93                                             unsigned OffsetToNextPC) {
94   auto &O = *cast<MachOObjectFile>(RI->getObject());
95   section_iterator SecI = O.getRelocationRelocatedSection(RI);
96   Value.Offset += RI->getOffset() + OffsetToNextPC + SecI->getAddress();
97 }
98 
99 void RuntimeDyldMachO::dumpRelocationToResolve(const RelocationEntry &RE,
100                                                uint64_t Value) const {
101   const SectionEntry &Section = Sections[RE.SectionID];
102   uint8_t *LocalAddress = Section.Address + RE.Offset;
103   uint64_t FinalAddress = Section.LoadAddress + RE.Offset;
104 
105   dbgs() << "resolveRelocation Section: " << RE.SectionID
106          << " LocalAddress: " << format("%p", LocalAddress)
107          << " FinalAddress: " << format("0x%016" PRIx64, FinalAddress)
108          << " Value: " << format("0x%016" PRIx64, Value) << " Addend: " << RE.Addend
109          << " isPCRel: " << RE.IsPCRel << " MachoType: " << RE.RelType
110          << " Size: " << (1 << RE.Size) << "\n";
111 }
112 
113 section_iterator
114 RuntimeDyldMachO::getSectionByAddress(const MachOObjectFile &Obj,
115                                       uint64_t Addr) {
116   section_iterator SI = Obj.section_begin();
117   section_iterator SE = Obj.section_end();
118 
119   for (; SI != SE; ++SI) {
120     uint64_t SAddr = SI->getAddress();
121     uint64_t SSize = SI->getSize();
122     if ((Addr >= SAddr) && (Addr < SAddr + SSize))
123       return SI;
124   }
125 
126   return SE;
127 }
128 
129 
130 // Populate __pointers section.
131 void RuntimeDyldMachO::populateIndirectSymbolPointersSection(
132                                                     const MachOObjectFile &Obj,
133                                                     const SectionRef &PTSection,
134                                                     unsigned PTSectionID) {
135   assert(!Obj.is64Bit() &&
136          "Pointer table section not supported in 64-bit MachO.");
137 
138   MachO::dysymtab_command DySymTabCmd = Obj.getDysymtabLoadCommand();
139   MachO::section Sec32 = Obj.getSection(PTSection.getRawDataRefImpl());
140   uint32_t PTSectionSize = Sec32.size;
141   unsigned FirstIndirectSymbol = Sec32.reserved1;
142   const unsigned PTEntrySize = 4;
143   unsigned NumPTEntries = PTSectionSize / PTEntrySize;
144   unsigned PTEntryOffset = 0;
145 
146   assert((PTSectionSize % PTEntrySize) == 0 &&
147          "Pointers section does not contain a whole number of stubs?");
148 
149   DEBUG(dbgs() << "Populating pointer table section "
150                << Sections[PTSectionID].Name
151                << ", Section ID " << PTSectionID << ", "
152                << NumPTEntries << " entries, " << PTEntrySize
153                << " bytes each:\n");
154 
155   for (unsigned i = 0; i < NumPTEntries; ++i) {
156     unsigned SymbolIndex =
157       Obj.getIndirectSymbolTableEntry(DySymTabCmd, FirstIndirectSymbol + i);
158     symbol_iterator SI = Obj.getSymbolByIndex(SymbolIndex);
159     ErrorOr<StringRef> IndirectSymbolNameOrErr = SI->getName();
160     if (std::error_code EC = IndirectSymbolNameOrErr.getError())
161       report_fatal_error(EC.message());
162     StringRef IndirectSymbolName = *IndirectSymbolNameOrErr;
163     DEBUG(dbgs() << "  " << IndirectSymbolName << ": index " << SymbolIndex
164           << ", PT offset: " << PTEntryOffset << "\n");
165     RelocationEntry RE(PTSectionID, PTEntryOffset,
166                        MachO::GENERIC_RELOC_VANILLA, 0, false, 2);
167     addRelocationForSymbol(RE, IndirectSymbolName);
168     PTEntryOffset += PTEntrySize;
169   }
170 }
171 
172 bool RuntimeDyldMachO::isCompatibleFile(const object::ObjectFile &Obj) const {
173   return Obj.isMachO();
174 }
175 
176 template <typename Impl>
177 void RuntimeDyldMachOCRTPBase<Impl>::finalizeLoad(const ObjectFile &Obj,
178                                                   ObjSectionToIDMap &SectionMap) {
179   unsigned EHFrameSID = RTDYLD_INVALID_SECTION_ID;
180   unsigned TextSID = RTDYLD_INVALID_SECTION_ID;
181   unsigned ExceptTabSID = RTDYLD_INVALID_SECTION_ID;
182 
183   for (const auto &Section : Obj.sections()) {
184     StringRef Name;
185     Section.getName(Name);
186 
187     // Force emission of the __text, __eh_frame, and __gcc_except_tab sections
188     // if they're present. Otherwise call down to the impl to handle other
189     // sections that have already been emitted.
190     if (Name == "__text")
191       TextSID = findOrEmitSection(Obj, Section, true, SectionMap);
192     else if (Name == "__eh_frame")
193       EHFrameSID = findOrEmitSection(Obj, Section, false, SectionMap);
194     else if (Name == "__gcc_except_tab")
195       ExceptTabSID = findOrEmitSection(Obj, Section, true, SectionMap);
196     else {
197       auto I = SectionMap.find(Section);
198       if (I != SectionMap.end())
199         impl().finalizeSection(Obj, I->second, Section);
200     }
201   }
202   UnregisteredEHFrameSections.push_back(
203     EHFrameRelatedSections(EHFrameSID, TextSID, ExceptTabSID));
204 }
205 
206 template <typename Impl>
207 unsigned char *RuntimeDyldMachOCRTPBase<Impl>::processFDE(unsigned char *P,
208                                                           int64_t DeltaForText,
209                                                           int64_t DeltaForEH) {
210   typedef typename Impl::TargetPtrT TargetPtrT;
211 
212   DEBUG(dbgs() << "Processing FDE: Delta for text: " << DeltaForText
213                << ", Delta for EH: " << DeltaForEH << "\n");
214   uint32_t Length = readBytesUnaligned(P, 4);
215   P += 4;
216   unsigned char *Ret = P + Length;
217   uint32_t Offset = readBytesUnaligned(P, 4);
218   if (Offset == 0) // is a CIE
219     return Ret;
220 
221   P += 4;
222   TargetPtrT FDELocation = readBytesUnaligned(P, sizeof(TargetPtrT));
223   TargetPtrT NewLocation = FDELocation - DeltaForText;
224   writeBytesUnaligned(NewLocation, P, sizeof(TargetPtrT));
225 
226   P += sizeof(TargetPtrT);
227 
228   // Skip the FDE address range
229   P += sizeof(TargetPtrT);
230 
231   uint8_t Augmentationsize = *P;
232   P += 1;
233   if (Augmentationsize != 0) {
234     TargetPtrT LSDA = readBytesUnaligned(P, sizeof(TargetPtrT));
235     TargetPtrT NewLSDA = LSDA - DeltaForEH;
236     writeBytesUnaligned(NewLSDA, P, sizeof(TargetPtrT));
237   }
238 
239   return Ret;
240 }
241 
242 static int64_t computeDelta(SectionEntry *A, SectionEntry *B) {
243   int64_t ObjDistance =
244     static_cast<int64_t>(A->ObjAddress) - static_cast<int64_t>(B->ObjAddress);
245   int64_t MemDistance = A->LoadAddress - B->LoadAddress;
246   return ObjDistance - MemDistance;
247 }
248 
249 template <typename Impl>
250 void RuntimeDyldMachOCRTPBase<Impl>::registerEHFrames() {
251 
252   for (int i = 0, e = UnregisteredEHFrameSections.size(); i != e; ++i) {
253     EHFrameRelatedSections &SectionInfo = UnregisteredEHFrameSections[i];
254     if (SectionInfo.EHFrameSID == RTDYLD_INVALID_SECTION_ID ||
255         SectionInfo.TextSID == RTDYLD_INVALID_SECTION_ID)
256       continue;
257     SectionEntry *Text = &Sections[SectionInfo.TextSID];
258     SectionEntry *EHFrame = &Sections[SectionInfo.EHFrameSID];
259     SectionEntry *ExceptTab = nullptr;
260     if (SectionInfo.ExceptTabSID != RTDYLD_INVALID_SECTION_ID)
261       ExceptTab = &Sections[SectionInfo.ExceptTabSID];
262 
263     int64_t DeltaForText = computeDelta(Text, EHFrame);
264     int64_t DeltaForEH = 0;
265     if (ExceptTab)
266       DeltaForEH = computeDelta(ExceptTab, EHFrame);
267 
268     unsigned char *P = EHFrame->Address;
269     unsigned char *End = P + EHFrame->Size;
270     do {
271       P = processFDE(P, DeltaForText, DeltaForEH);
272     } while (P != End);
273 
274     MemMgr.registerEHFrames(EHFrame->Address, EHFrame->LoadAddress,
275                             EHFrame->Size);
276   }
277   UnregisteredEHFrameSections.clear();
278 }
279 
280 std::unique_ptr<RuntimeDyldMachO>
281 RuntimeDyldMachO::create(Triple::ArchType Arch,
282                          RuntimeDyld::MemoryManager &MemMgr,
283                          RuntimeDyld::SymbolResolver &Resolver) {
284   switch (Arch) {
285   default:
286     llvm_unreachable("Unsupported target for RuntimeDyldMachO.");
287     break;
288   case Triple::arm:
289     return make_unique<RuntimeDyldMachOARM>(MemMgr, Resolver);
290   case Triple::aarch64:
291     return make_unique<RuntimeDyldMachOAArch64>(MemMgr, Resolver);
292   case Triple::x86:
293     return make_unique<RuntimeDyldMachOI386>(MemMgr, Resolver);
294   case Triple::x86_64:
295     return make_unique<RuntimeDyldMachOX86_64>(MemMgr, Resolver);
296   }
297 }
298 
299 std::unique_ptr<RuntimeDyld::LoadedObjectInfo>
300 RuntimeDyldMachO::loadObject(const object::ObjectFile &O) {
301   unsigned SectionStartIdx, SectionEndIdx;
302   std::tie(SectionStartIdx, SectionEndIdx) = loadObjectImpl(O);
303   return llvm::make_unique<LoadedMachOObjectInfo>(*this, SectionStartIdx,
304                                                   SectionEndIdx);
305 }
306 
307 } // end namespace llvm
308