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