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