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 : public RuntimeDyld::LoadedObjectInfo {
30 public:
31   LoadedMachOObjectInfo(RuntimeDyldImpl &RTDyld, unsigned BeginIdx,
32                         unsigned EndIdx)
33     : RuntimeDyld::LoadedObjectInfo(RTDyld, BeginIdx, EndIdx) {}
34 
35   OwningBinary<ObjectFile>
36   getObjectForDebug(const ObjectFile &Obj) const override {
37     return OwningBinary<ObjectFile>();
38   }
39 };
40 
41 }
42 
43 namespace llvm {
44 
45 int64_t RuntimeDyldMachO::memcpyAddend(const RelocationEntry &RE) const {
46   unsigned NumBytes = 1 << RE.Size;
47   uint8_t *Src = Sections[RE.SectionID].Address + RE.Offset;
48 
49   return static_cast<int64_t>(readBytesUnaligned(Src, NumBytes));
50 }
51 
52 RelocationValueRef RuntimeDyldMachO::getRelocationValueRef(
53     const ObjectFile &BaseTObj, const relocation_iterator &RI,
54     const RelocationEntry &RE, ObjSectionToIDMap &ObjSectionToID) {
55 
56   const MachOObjectFile &Obj =
57       static_cast<const MachOObjectFile &>(BaseTObj);
58   MachO::any_relocation_info RelInfo =
59       Obj.getRelocation(RI->getRawDataRefImpl());
60   RelocationValueRef Value;
61 
62   bool IsExternal = Obj.getPlainRelocationExternal(RelInfo);
63   if (IsExternal) {
64     symbol_iterator Symbol = RI->getSymbol();
65     StringRef TargetName;
66     Symbol->getName(TargetName);
67     RTDyldSymbolTable::const_iterator SI =
68       GlobalSymbolTable.find(TargetName.data());
69     if (SI != GlobalSymbolTable.end()) {
70       const auto &SymInfo = SI->second;
71       Value.SectionID = SymInfo.getSectionID();
72       Value.Offset = SymInfo.getOffset() + RE.Addend;
73     } else {
74       Value.SymbolName = TargetName.data();
75       Value.Offset = RE.Addend;
76     }
77   } else {
78     SectionRef Sec = Obj.getRelocationSection(RelInfo);
79     bool IsCode = Sec.isText();
80     Value.SectionID = findOrEmitSection(Obj, Sec, IsCode, ObjSectionToID);
81     uint64_t Addr = Sec.getAddress();
82     Value.Offset = RE.Addend - Addr;
83   }
84 
85   return Value;
86 }
87 
88 void RuntimeDyldMachO::makeValueAddendPCRel(RelocationValueRef &Value,
89                                             const ObjectFile &BaseTObj,
90                                             const relocation_iterator &RI,
91                                             unsigned OffsetToNextPC) {
92   const MachOObjectFile &Obj =
93       static_cast<const MachOObjectFile &>(BaseTObj);
94   MachO::any_relocation_info RelInfo =
95       Obj.getRelocation(RI->getRawDataRefImpl());
96 
97   bool IsPCRel = Obj.getAnyRelocationPCRel(RelInfo);
98   if (IsPCRel) {
99     uint64_t RelocAddr = 0;
100     RI->getAddress(RelocAddr);
101     Value.Offset += RelocAddr + OffsetToNextPC;
102   }
103 }
104 
105 void RuntimeDyldMachO::dumpRelocationToResolve(const RelocationEntry &RE,
106                                                uint64_t Value) const {
107   const SectionEntry &Section = Sections[RE.SectionID];
108   uint8_t *LocalAddress = Section.Address + RE.Offset;
109   uint64_t FinalAddress = Section.LoadAddress + RE.Offset;
110 
111   dbgs() << "resolveRelocation Section: " << RE.SectionID
112          << " LocalAddress: " << format("%p", LocalAddress)
113          << " FinalAddress: " << format("0x%016" PRIx64, FinalAddress)
114          << " Value: " << format("0x%016" PRIx64, Value) << " Addend: " << RE.Addend
115          << " isPCRel: " << RE.IsPCRel << " MachoType: " << RE.RelType
116          << " Size: " << (1 << RE.Size) << "\n";
117 }
118 
119 section_iterator
120 RuntimeDyldMachO::getSectionByAddress(const MachOObjectFile &Obj,
121                                       uint64_t Addr) {
122   section_iterator SI = Obj.section_begin();
123   section_iterator SE = Obj.section_end();
124 
125   for (; SI != SE; ++SI) {
126     uint64_t SAddr = SI->getAddress();
127     uint64_t SSize = SI->getSize();
128     if ((Addr >= SAddr) && (Addr < SAddr + SSize))
129       return SI;
130   }
131 
132   return SE;
133 }
134 
135 
136 // Populate __pointers section.
137 void RuntimeDyldMachO::populateIndirectSymbolPointersSection(
138                                                     const MachOObjectFile &Obj,
139                                                     const SectionRef &PTSection,
140                                                     unsigned PTSectionID) {
141   assert(!Obj.is64Bit() &&
142          "Pointer table section not supported in 64-bit MachO.");
143 
144   MachO::dysymtab_command DySymTabCmd = Obj.getDysymtabLoadCommand();
145   MachO::section Sec32 = Obj.getSection(PTSection.getRawDataRefImpl());
146   uint32_t PTSectionSize = Sec32.size;
147   unsigned FirstIndirectSymbol = Sec32.reserved1;
148   const unsigned PTEntrySize = 4;
149   unsigned NumPTEntries = PTSectionSize / PTEntrySize;
150   unsigned PTEntryOffset = 0;
151 
152   assert((PTSectionSize % PTEntrySize) == 0 &&
153          "Pointers section does not contain a whole number of stubs?");
154 
155   DEBUG(dbgs() << "Populating pointer table section "
156                << Sections[PTSectionID].Name
157                << ", Section ID " << PTSectionID << ", "
158                << NumPTEntries << " entries, " << PTEntrySize
159                << " bytes each:\n");
160 
161   for (unsigned i = 0; i < NumPTEntries; ++i) {
162     unsigned SymbolIndex =
163       Obj.getIndirectSymbolTableEntry(DySymTabCmd, FirstIndirectSymbol + i);
164     symbol_iterator SI = Obj.getSymbolByIndex(SymbolIndex);
165     StringRef IndirectSymbolName;
166     SI->getName(IndirectSymbolName);
167     DEBUG(dbgs() << "  " << IndirectSymbolName << ": index " << SymbolIndex
168           << ", PT offset: " << PTEntryOffset << "\n");
169     RelocationEntry RE(PTSectionID, PTEntryOffset,
170                        MachO::GENERIC_RELOC_VANILLA, 0, false, 2);
171     addRelocationForSymbol(RE, IndirectSymbolName);
172     PTEntryOffset += PTEntrySize;
173   }
174 }
175 
176 bool RuntimeDyldMachO::isCompatibleFile(const object::ObjectFile &Obj) const {
177   return Obj.isMachO();
178 }
179 
180 template <typename Impl>
181 void RuntimeDyldMachOCRTPBase<Impl>::finalizeLoad(const ObjectFile &Obj,
182                                                   ObjSectionToIDMap &SectionMap) {
183   unsigned EHFrameSID = RTDYLD_INVALID_SECTION_ID;
184   unsigned TextSID = RTDYLD_INVALID_SECTION_ID;
185   unsigned ExceptTabSID = RTDYLD_INVALID_SECTION_ID;
186 
187   for (const auto &Section : Obj.sections()) {
188     StringRef Name;
189     Section.getName(Name);
190 
191     // Force emission of the __text, __eh_frame, and __gcc_except_tab sections
192     // if they're present. Otherwise call down to the impl to handle other
193     // sections that have already been emitted.
194     if (Name == "__text")
195       TextSID = findOrEmitSection(Obj, Section, true, SectionMap);
196     else if (Name == "__eh_frame")
197       EHFrameSID = findOrEmitSection(Obj, Section, false, SectionMap);
198     else if (Name == "__gcc_except_tab")
199       ExceptTabSID = findOrEmitSection(Obj, Section, true, SectionMap);
200     else {
201       auto I = SectionMap.find(Section);
202       if (I != SectionMap.end())
203         impl().finalizeSection(Obj, I->second, Section);
204     }
205   }
206   UnregisteredEHFrameSections.push_back(
207     EHFrameRelatedSections(EHFrameSID, TextSID, ExceptTabSID));
208 }
209 
210 template <typename Impl>
211 unsigned char *RuntimeDyldMachOCRTPBase<Impl>::processFDE(unsigned char *P,
212                                                           int64_t DeltaForText,
213                                                           int64_t DeltaForEH) {
214   typedef typename Impl::TargetPtrT TargetPtrT;
215 
216   DEBUG(dbgs() << "Processing FDE: Delta for text: " << DeltaForText
217                << ", Delta for EH: " << DeltaForEH << "\n");
218   uint32_t Length = readBytesUnaligned(P, 4);
219   P += 4;
220   unsigned char *Ret = P + Length;
221   uint32_t Offset = readBytesUnaligned(P, 4);
222   if (Offset == 0) // is a CIE
223     return Ret;
224 
225   P += 4;
226   TargetPtrT FDELocation = readBytesUnaligned(P, sizeof(TargetPtrT));
227   TargetPtrT NewLocation = FDELocation - DeltaForText;
228   writeBytesUnaligned(NewLocation, P, sizeof(TargetPtrT));
229 
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 = readBytesUnaligned(P, sizeof(TargetPtrT));
239     TargetPtrT NewLSDA = LSDA - DeltaForEH;
240     writeBytesUnaligned(NewLSDA, P, sizeof(TargetPtrT));
241   }
242 
243   return Ret;
244 }
245 
246 static int64_t computeDelta(SectionEntry *A, SectionEntry *B) {
247   int64_t ObjDistance =
248     static_cast<int64_t>(A->ObjAddress) - static_cast<int64_t>(B->ObjAddress);
249   int64_t MemDistance = A->LoadAddress - B->LoadAddress;
250   return ObjDistance - MemDistance;
251 }
252 
253 template <typename Impl>
254 void RuntimeDyldMachOCRTPBase<Impl>::registerEHFrames() {
255 
256   for (int i = 0, e = UnregisteredEHFrameSections.size(); i != e; ++i) {
257     EHFrameRelatedSections &SectionInfo = UnregisteredEHFrameSections[i];
258     if (SectionInfo.EHFrameSID == RTDYLD_INVALID_SECTION_ID ||
259         SectionInfo.TextSID == RTDYLD_INVALID_SECTION_ID)
260       continue;
261     SectionEntry *Text = &Sections[SectionInfo.TextSID];
262     SectionEntry *EHFrame = &Sections[SectionInfo.EHFrameSID];
263     SectionEntry *ExceptTab = nullptr;
264     if (SectionInfo.ExceptTabSID != RTDYLD_INVALID_SECTION_ID)
265       ExceptTab = &Sections[SectionInfo.ExceptTabSID];
266 
267     int64_t DeltaForText = computeDelta(Text, EHFrame);
268     int64_t DeltaForEH = 0;
269     if (ExceptTab)
270       DeltaForEH = computeDelta(ExceptTab, EHFrame);
271 
272     unsigned char *P = EHFrame->Address;
273     unsigned char *End = P + EHFrame->Size;
274     do {
275       P = processFDE(P, DeltaForText, DeltaForEH);
276     } while (P != End);
277 
278     MemMgr.registerEHFrames(EHFrame->Address, EHFrame->LoadAddress,
279                             EHFrame->Size);
280   }
281   UnregisteredEHFrameSections.clear();
282 }
283 
284 std::unique_ptr<RuntimeDyldMachO>
285 RuntimeDyldMachO::create(Triple::ArchType Arch,
286                          RuntimeDyld::MemoryManager &MemMgr,
287                          RuntimeDyld::SymbolResolver &Resolver) {
288   switch (Arch) {
289   default:
290     llvm_unreachable("Unsupported target for RuntimeDyldMachO.");
291     break;
292   case Triple::arm:
293     return make_unique<RuntimeDyldMachOARM>(MemMgr, Resolver);
294   case Triple::aarch64:
295     return make_unique<RuntimeDyldMachOAArch64>(MemMgr, Resolver);
296   case Triple::x86:
297     return make_unique<RuntimeDyldMachOI386>(MemMgr, Resolver);
298   case Triple::x86_64:
299     return make_unique<RuntimeDyldMachOX86_64>(MemMgr, Resolver);
300   }
301 }
302 
303 std::unique_ptr<RuntimeDyld::LoadedObjectInfo>
304 RuntimeDyldMachO::loadObject(const object::ObjectFile &O) {
305   unsigned SectionStartIdx, SectionEndIdx;
306   std::tie(SectionStartIdx, SectionEndIdx) = loadObjectImpl(O);
307   return llvm::make_unique<LoadedMachOObjectInfo>(*this, SectionStartIdx,
308                                                   SectionEndIdx);
309 }
310 
311 } // end namespace llvm
312