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1 //===-- RuntimeDyld.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 "llvm/ExecutionEngine/RuntimeDyld.h"
15 #include "RuntimeDyldCheckerImpl.h"
16 #include "RuntimeDyldCOFF.h"
17 #include "RuntimeDyldELF.h"
18 #include "RuntimeDyldImpl.h"
19 #include "RuntimeDyldMachO.h"
20 #include "llvm/Object/ELFObjectFile.h"
21 #include "llvm/Object/COFF.h"
22 #include "llvm/Support/MathExtras.h"
23 #include "llvm/Support/MutexGuard.h"
24 
25 using namespace llvm;
26 using namespace llvm::object;
27 
28 #define DEBUG_TYPE "dyld"
29 
30 // Empty out-of-line virtual destructor as the key function.
~RuntimeDyldImpl()31 RuntimeDyldImpl::~RuntimeDyldImpl() {}
32 
33 // Pin LoadedObjectInfo's vtables to this file.
anchor()34 void RuntimeDyld::LoadedObjectInfo::anchor() {}
35 
36 namespace llvm {
37 
registerEHFrames()38 void RuntimeDyldImpl::registerEHFrames() {}
39 
deregisterEHFrames()40 void RuntimeDyldImpl::deregisterEHFrames() {}
41 
42 #ifndef NDEBUG
dumpSectionMemory(const SectionEntry & S,StringRef State)43 static void dumpSectionMemory(const SectionEntry &S, StringRef State) {
44   dbgs() << "----- Contents of section " << S.getName() << " " << State
45          << " -----";
46 
47   if (S.getAddress() == nullptr) {
48     dbgs() << "\n          <section not emitted>\n";
49     return;
50   }
51 
52   const unsigned ColsPerRow = 16;
53 
54   uint8_t *DataAddr = S.getAddress();
55   uint64_t LoadAddr = S.getLoadAddress();
56 
57   unsigned StartPadding = LoadAddr & (ColsPerRow - 1);
58   unsigned BytesRemaining = S.getSize();
59 
60   if (StartPadding) {
61     dbgs() << "\n" << format("0x%016" PRIx64,
62                              LoadAddr & ~(uint64_t)(ColsPerRow - 1)) << ":";
63     while (StartPadding--)
64       dbgs() << "   ";
65   }
66 
67   while (BytesRemaining > 0) {
68     if ((LoadAddr & (ColsPerRow - 1)) == 0)
69       dbgs() << "\n" << format("0x%016" PRIx64, LoadAddr) << ":";
70 
71     dbgs() << " " << format("%02x", *DataAddr);
72 
73     ++DataAddr;
74     ++LoadAddr;
75     --BytesRemaining;
76   }
77 
78   dbgs() << "\n";
79 }
80 #endif
81 
82 // Resolve the relocations for all symbols we currently know about.
resolveRelocations()83 void RuntimeDyldImpl::resolveRelocations() {
84   MutexGuard locked(lock);
85 
86   // Print out the sections prior to relocation.
87   DEBUG(
88     for (int i = 0, e = Sections.size(); i != e; ++i)
89       dumpSectionMemory(Sections[i], "before relocations");
90   );
91 
92   // First, resolve relocations associated with external symbols.
93   resolveExternalSymbols();
94 
95   // Iterate over all outstanding relocations
96   for (auto it = Relocations.begin(), e = Relocations.end(); it != e; ++it) {
97     // The Section here (Sections[i]) refers to the section in which the
98     // symbol for the relocation is located.  The SectionID in the relocation
99     // entry provides the section to which the relocation will be applied.
100     int Idx = it->first;
101     uint64_t Addr = Sections[Idx].getLoadAddress();
102     DEBUG(dbgs() << "Resolving relocations Section #" << Idx << "\t"
103                  << format("%p", (uintptr_t)Addr) << "\n");
104     resolveRelocationList(it->second, Addr);
105   }
106   Relocations.clear();
107 
108   // Print out sections after relocation.
109   DEBUG(
110     for (int i = 0, e = Sections.size(); i != e; ++i)
111       dumpSectionMemory(Sections[i], "after relocations");
112   );
113 
114 }
115 
mapSectionAddress(const void * LocalAddress,uint64_t TargetAddress)116 void RuntimeDyldImpl::mapSectionAddress(const void *LocalAddress,
117                                         uint64_t TargetAddress) {
118   MutexGuard locked(lock);
119   for (unsigned i = 0, e = Sections.size(); i != e; ++i) {
120     if (Sections[i].getAddress() == LocalAddress) {
121       reassignSectionAddress(i, TargetAddress);
122       return;
123     }
124   }
125   llvm_unreachable("Attempting to remap address of unknown section!");
126 }
127 
getOffset(const SymbolRef & Sym,SectionRef Sec,uint64_t & Result)128 static std::error_code getOffset(const SymbolRef &Sym, SectionRef Sec,
129                                  uint64_t &Result) {
130   ErrorOr<uint64_t> AddressOrErr = Sym.getAddress();
131   if (std::error_code EC = AddressOrErr.getError())
132     return EC;
133   Result = *AddressOrErr - Sec.getAddress();
134   return std::error_code();
135 }
136 
137 RuntimeDyldImpl::ObjSectionToIDMap
loadObjectImpl(const object::ObjectFile & Obj)138 RuntimeDyldImpl::loadObjectImpl(const object::ObjectFile &Obj) {
139   MutexGuard locked(lock);
140 
141   // Save information about our target
142   Arch = (Triple::ArchType)Obj.getArch();
143   IsTargetLittleEndian = Obj.isLittleEndian();
144   setMipsABI(Obj);
145 
146   // Compute the memory size required to load all sections to be loaded
147   // and pass this information to the memory manager
148   if (MemMgr.needsToReserveAllocationSpace()) {
149     uint64_t CodeSize = 0, DataSizeRO = 0, DataSizeRW = 0;
150     computeTotalAllocSize(Obj, CodeSize, DataSizeRO, DataSizeRW);
151     MemMgr.reserveAllocationSpace(CodeSize, DataSizeRO, DataSizeRW);
152   }
153 
154   // Used sections from the object file
155   ObjSectionToIDMap LocalSections;
156 
157   // Common symbols requiring allocation, with their sizes and alignments
158   CommonSymbolList CommonSymbols;
159 
160   // Parse symbols
161   DEBUG(dbgs() << "Parse symbols:\n");
162   for (symbol_iterator I = Obj.symbol_begin(), E = Obj.symbol_end(); I != E;
163        ++I) {
164     uint32_t Flags = I->getFlags();
165 
166     if (Flags & SymbolRef::SF_Common)
167       CommonSymbols.push_back(*I);
168     else {
169       object::SymbolRef::Type SymType = I->getType();
170 
171       // Get symbol name.
172       ErrorOr<StringRef> NameOrErr = I->getName();
173       Check(NameOrErr.getError());
174       StringRef Name = *NameOrErr;
175 
176       // Compute JIT symbol flags.
177       JITSymbolFlags RTDyldSymFlags = JITSymbolFlags::None;
178       if (Flags & SymbolRef::SF_Weak)
179         RTDyldSymFlags |= JITSymbolFlags::Weak;
180       if (Flags & SymbolRef::SF_Exported)
181         RTDyldSymFlags |= JITSymbolFlags::Exported;
182 
183       if (Flags & SymbolRef::SF_Absolute &&
184           SymType != object::SymbolRef::ST_File) {
185         auto Addr = I->getAddress();
186         Check(Addr.getError());
187         uint64_t SectOffset = *Addr;
188         unsigned SectionID = AbsoluteSymbolSection;
189 
190         DEBUG(dbgs() << "\tType: " << SymType << " (absolute) Name: " << Name
191                      << " SID: " << SectionID << " Offset: "
192                      << format("%p", (uintptr_t)SectOffset)
193                      << " flags: " << Flags << "\n");
194         GlobalSymbolTable[Name] =
195           SymbolTableEntry(SectionID, SectOffset, RTDyldSymFlags);
196       } else if (SymType == object::SymbolRef::ST_Function ||
197                  SymType == object::SymbolRef::ST_Data ||
198                  SymType == object::SymbolRef::ST_Unknown ||
199                  SymType == object::SymbolRef::ST_Other) {
200 
201         ErrorOr<section_iterator> SIOrErr = I->getSection();
202         Check(SIOrErr.getError());
203         section_iterator SI = *SIOrErr;
204         if (SI == Obj.section_end())
205           continue;
206         // Get symbol offset.
207         uint64_t SectOffset;
208         Check(getOffset(*I, *SI, SectOffset));
209         bool IsCode = SI->isText();
210         unsigned SectionID = findOrEmitSection(Obj, *SI, IsCode, LocalSections);
211 
212         DEBUG(dbgs() << "\tType: " << SymType << " Name: " << Name
213                      << " SID: " << SectionID << " Offset: "
214                      << format("%p", (uintptr_t)SectOffset)
215                      << " flags: " << Flags << "\n");
216         GlobalSymbolTable[Name] =
217           SymbolTableEntry(SectionID, SectOffset, RTDyldSymFlags);
218       }
219     }
220   }
221 
222   // Allocate common symbols
223   emitCommonSymbols(Obj, CommonSymbols);
224 
225   // Parse and process relocations
226   DEBUG(dbgs() << "Parse relocations:\n");
227   for (section_iterator SI = Obj.section_begin(), SE = Obj.section_end();
228        SI != SE; ++SI) {
229     unsigned SectionID = 0;
230     StubMap Stubs;
231     section_iterator RelocatedSection = SI->getRelocatedSection();
232 
233     if (RelocatedSection == SE)
234       continue;
235 
236     relocation_iterator I = SI->relocation_begin();
237     relocation_iterator E = SI->relocation_end();
238 
239     if (I == E && !ProcessAllSections)
240       continue;
241 
242     bool IsCode = RelocatedSection->isText();
243     SectionID =
244         findOrEmitSection(Obj, *RelocatedSection, IsCode, LocalSections);
245     DEBUG(dbgs() << "\tSectionID: " << SectionID << "\n");
246 
247     for (; I != E;)
248       I = processRelocationRef(SectionID, I, Obj, LocalSections, Stubs);
249 
250     // If there is an attached checker, notify it about the stubs for this
251     // section so that they can be verified.
252     if (Checker)
253       Checker->registerStubMap(Obj.getFileName(), SectionID, Stubs);
254   }
255 
256   // Give the subclasses a chance to tie-up any loose ends.
257   finalizeLoad(Obj, LocalSections);
258 
259 //   for (auto E : LocalSections)
260 //     llvm::dbgs() << "Added: " << E.first.getRawDataRefImpl() << " -> " << E.second << "\n";
261 
262   return LocalSections;
263 }
264 
265 // A helper method for computeTotalAllocSize.
266 // Computes the memory size required to allocate sections with the given sizes,
267 // assuming that all sections are allocated with the given alignment
268 static uint64_t
computeAllocationSizeForSections(std::vector<uint64_t> & SectionSizes,uint64_t Alignment)269 computeAllocationSizeForSections(std::vector<uint64_t> &SectionSizes,
270                                  uint64_t Alignment) {
271   uint64_t TotalSize = 0;
272   for (size_t Idx = 0, Cnt = SectionSizes.size(); Idx < Cnt; Idx++) {
273     uint64_t AlignedSize =
274         (SectionSizes[Idx] + Alignment - 1) / Alignment * Alignment;
275     TotalSize += AlignedSize;
276   }
277   return TotalSize;
278 }
279 
isRequiredForExecution(const SectionRef Section)280 static bool isRequiredForExecution(const SectionRef Section) {
281   const ObjectFile *Obj = Section.getObject();
282   if (isa<object::ELFObjectFileBase>(Obj))
283     return ELFSectionRef(Section).getFlags() & ELF::SHF_ALLOC;
284   if (auto *COFFObj = dyn_cast<object::COFFObjectFile>(Obj)) {
285     const coff_section *CoffSection = COFFObj->getCOFFSection(Section);
286     // Avoid loading zero-sized COFF sections.
287     // In PE files, VirtualSize gives the section size, and SizeOfRawData
288     // may be zero for sections with content. In Obj files, SizeOfRawData
289     // gives the section size, and VirtualSize is always zero. Hence
290     // the need to check for both cases below.
291     bool HasContent = (CoffSection->VirtualSize > 0)
292       || (CoffSection->SizeOfRawData > 0);
293     bool IsDiscardable = CoffSection->Characteristics &
294       (COFF::IMAGE_SCN_MEM_DISCARDABLE | COFF::IMAGE_SCN_LNK_INFO);
295     return HasContent && !IsDiscardable;
296   }
297 
298   assert(isa<MachOObjectFile>(Obj));
299   return true;
300 }
301 
isReadOnlyData(const SectionRef Section)302 static bool isReadOnlyData(const SectionRef Section) {
303   const ObjectFile *Obj = Section.getObject();
304   if (isa<object::ELFObjectFileBase>(Obj))
305     return !(ELFSectionRef(Section).getFlags() &
306              (ELF::SHF_WRITE | ELF::SHF_EXECINSTR));
307   if (auto *COFFObj = dyn_cast<object::COFFObjectFile>(Obj))
308     return ((COFFObj->getCOFFSection(Section)->Characteristics &
309              (COFF::IMAGE_SCN_CNT_INITIALIZED_DATA
310              | COFF::IMAGE_SCN_MEM_READ
311              | COFF::IMAGE_SCN_MEM_WRITE))
312              ==
313              (COFF::IMAGE_SCN_CNT_INITIALIZED_DATA
314              | COFF::IMAGE_SCN_MEM_READ));
315 
316   assert(isa<MachOObjectFile>(Obj));
317   return false;
318 }
319 
isZeroInit(const SectionRef Section)320 static bool isZeroInit(const SectionRef Section) {
321   const ObjectFile *Obj = Section.getObject();
322   if (isa<object::ELFObjectFileBase>(Obj))
323     return ELFSectionRef(Section).getType() == ELF::SHT_NOBITS;
324   if (auto *COFFObj = dyn_cast<object::COFFObjectFile>(Obj))
325     return COFFObj->getCOFFSection(Section)->Characteristics &
326             COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA;
327 
328   auto *MachO = cast<MachOObjectFile>(Obj);
329   unsigned SectionType = MachO->getSectionType(Section);
330   return SectionType == MachO::S_ZEROFILL ||
331          SectionType == MachO::S_GB_ZEROFILL;
332 }
333 
334 // Compute an upper bound of the memory size that is required to load all
335 // sections
computeTotalAllocSize(const ObjectFile & Obj,uint64_t & CodeSize,uint64_t & DataSizeRO,uint64_t & DataSizeRW)336 void RuntimeDyldImpl::computeTotalAllocSize(const ObjectFile &Obj,
337                                             uint64_t &CodeSize,
338                                             uint64_t &DataSizeRO,
339                                             uint64_t &DataSizeRW) {
340   // Compute the size of all sections required for execution
341   std::vector<uint64_t> CodeSectionSizes;
342   std::vector<uint64_t> ROSectionSizes;
343   std::vector<uint64_t> RWSectionSizes;
344   uint64_t MaxAlignment = sizeof(void *);
345 
346   // Collect sizes of all sections to be loaded;
347   // also determine the max alignment of all sections
348   for (section_iterator SI = Obj.section_begin(), SE = Obj.section_end();
349        SI != SE; ++SI) {
350     const SectionRef &Section = *SI;
351 
352     bool IsRequired = isRequiredForExecution(Section);
353 
354     // Consider only the sections that are required to be loaded for execution
355     if (IsRequired) {
356       StringRef Name;
357       uint64_t DataSize = Section.getSize();
358       uint64_t Alignment64 = Section.getAlignment();
359       bool IsCode = Section.isText();
360       bool IsReadOnly = isReadOnlyData(Section);
361       Check(Section.getName(Name));
362       unsigned Alignment = (unsigned)Alignment64 & 0xffffffffL;
363 
364       uint64_t StubBufSize = computeSectionStubBufSize(Obj, Section);
365       uint64_t SectionSize = DataSize + StubBufSize;
366 
367       // The .eh_frame section (at least on Linux) needs an extra four bytes
368       // padded
369       // with zeroes added at the end.  For MachO objects, this section has a
370       // slightly different name, so this won't have any effect for MachO
371       // objects.
372       if (Name == ".eh_frame")
373         SectionSize += 4;
374 
375       if (!SectionSize)
376         SectionSize = 1;
377 
378       if (IsCode) {
379         CodeSectionSizes.push_back(SectionSize);
380       } else if (IsReadOnly) {
381         ROSectionSizes.push_back(SectionSize);
382       } else {
383         RWSectionSizes.push_back(SectionSize);
384       }
385 
386       // update the max alignment
387       if (Alignment > MaxAlignment) {
388         MaxAlignment = Alignment;
389       }
390     }
391   }
392 
393   // Compute the size of all common symbols
394   uint64_t CommonSize = 0;
395   for (symbol_iterator I = Obj.symbol_begin(), E = Obj.symbol_end(); I != E;
396        ++I) {
397     uint32_t Flags = I->getFlags();
398     if (Flags & SymbolRef::SF_Common) {
399       // Add the common symbols to a list.  We'll allocate them all below.
400       uint64_t Size = I->getCommonSize();
401       CommonSize += Size;
402     }
403   }
404   if (CommonSize != 0) {
405     RWSectionSizes.push_back(CommonSize);
406   }
407 
408   // Compute the required allocation space for each different type of sections
409   // (code, read-only data, read-write data) assuming that all sections are
410   // allocated with the max alignment. Note that we cannot compute with the
411   // individual alignments of the sections, because then the required size
412   // depends on the order, in which the sections are allocated.
413   CodeSize = computeAllocationSizeForSections(CodeSectionSizes, MaxAlignment);
414   DataSizeRO = computeAllocationSizeForSections(ROSectionSizes, MaxAlignment);
415   DataSizeRW = computeAllocationSizeForSections(RWSectionSizes, MaxAlignment);
416 }
417 
418 // compute stub buffer size for the given section
computeSectionStubBufSize(const ObjectFile & Obj,const SectionRef & Section)419 unsigned RuntimeDyldImpl::computeSectionStubBufSize(const ObjectFile &Obj,
420                                                     const SectionRef &Section) {
421   unsigned StubSize = getMaxStubSize();
422   if (StubSize == 0) {
423     return 0;
424   }
425   // FIXME: this is an inefficient way to handle this. We should computed the
426   // necessary section allocation size in loadObject by walking all the sections
427   // once.
428   unsigned StubBufSize = 0;
429   for (section_iterator SI = Obj.section_begin(), SE = Obj.section_end();
430        SI != SE; ++SI) {
431     section_iterator RelSecI = SI->getRelocatedSection();
432     if (!(RelSecI == Section))
433       continue;
434 
435     for (const RelocationRef &Reloc : SI->relocations())
436       if (relocationNeedsStub(Reloc))
437         StubBufSize += StubSize;
438   }
439 
440   // Get section data size and alignment
441   uint64_t DataSize = Section.getSize();
442   uint64_t Alignment64 = Section.getAlignment();
443 
444   // Add stubbuf size alignment
445   unsigned Alignment = (unsigned)Alignment64 & 0xffffffffL;
446   unsigned StubAlignment = getStubAlignment();
447   unsigned EndAlignment = (DataSize | Alignment) & -(DataSize | Alignment);
448   if (StubAlignment > EndAlignment)
449     StubBufSize += StubAlignment - EndAlignment;
450   return StubBufSize;
451 }
452 
readBytesUnaligned(uint8_t * Src,unsigned Size) const453 uint64_t RuntimeDyldImpl::readBytesUnaligned(uint8_t *Src,
454                                              unsigned Size) const {
455   uint64_t Result = 0;
456   if (IsTargetLittleEndian) {
457     Src += Size - 1;
458     while (Size--)
459       Result = (Result << 8) | *Src--;
460   } else
461     while (Size--)
462       Result = (Result << 8) | *Src++;
463 
464   return Result;
465 }
466 
writeBytesUnaligned(uint64_t Value,uint8_t * Dst,unsigned Size) const467 void RuntimeDyldImpl::writeBytesUnaligned(uint64_t Value, uint8_t *Dst,
468                                           unsigned Size) const {
469   if (IsTargetLittleEndian) {
470     while (Size--) {
471       *Dst++ = Value & 0xFF;
472       Value >>= 8;
473     }
474   } else {
475     Dst += Size - 1;
476     while (Size--) {
477       *Dst-- = Value & 0xFF;
478       Value >>= 8;
479     }
480   }
481 }
482 
emitCommonSymbols(const ObjectFile & Obj,CommonSymbolList & CommonSymbols)483 void RuntimeDyldImpl::emitCommonSymbols(const ObjectFile &Obj,
484                                         CommonSymbolList &CommonSymbols) {
485   if (CommonSymbols.empty())
486     return;
487 
488   uint64_t CommonSize = 0;
489   CommonSymbolList SymbolsToAllocate;
490 
491   DEBUG(dbgs() << "Processing common symbols...\n");
492 
493   for (const auto &Sym : CommonSymbols) {
494     ErrorOr<StringRef> NameOrErr = Sym.getName();
495     Check(NameOrErr.getError());
496     StringRef Name = *NameOrErr;
497 
498     // Skip common symbols already elsewhere.
499     if (GlobalSymbolTable.count(Name) ||
500         Resolver.findSymbolInLogicalDylib(Name)) {
501       DEBUG(dbgs() << "\tSkipping already emitted common symbol '" << Name
502                    << "'\n");
503       continue;
504     }
505 
506     uint32_t Align = Sym.getAlignment();
507     uint64_t Size = Sym.getCommonSize();
508 
509     CommonSize += Align + Size;
510     SymbolsToAllocate.push_back(Sym);
511   }
512 
513   // Allocate memory for the section
514   unsigned SectionID = Sections.size();
515   uint8_t *Addr = MemMgr.allocateDataSection(CommonSize, sizeof(void *),
516                                              SectionID, StringRef(), false);
517   if (!Addr)
518     report_fatal_error("Unable to allocate memory for common symbols!");
519   uint64_t Offset = 0;
520   Sections.push_back(
521       SectionEntry("<common symbols>", Addr, CommonSize, CommonSize, 0));
522   memset(Addr, 0, CommonSize);
523 
524   DEBUG(dbgs() << "emitCommonSection SectionID: " << SectionID << " new addr: "
525                << format("%p", Addr) << " DataSize: " << CommonSize << "\n");
526 
527   // Assign the address of each symbol
528   for (auto &Sym : SymbolsToAllocate) {
529     uint32_t Align = Sym.getAlignment();
530     uint64_t Size = Sym.getCommonSize();
531     ErrorOr<StringRef> NameOrErr = Sym.getName();
532     Check(NameOrErr.getError());
533     StringRef Name = *NameOrErr;
534     if (Align) {
535       // This symbol has an alignment requirement.
536       uint64_t AlignOffset = OffsetToAlignment((uint64_t)Addr, Align);
537       Addr += AlignOffset;
538       Offset += AlignOffset;
539     }
540     uint32_t Flags = Sym.getFlags();
541     JITSymbolFlags RTDyldSymFlags = JITSymbolFlags::None;
542     if (Flags & SymbolRef::SF_Weak)
543       RTDyldSymFlags |= JITSymbolFlags::Weak;
544     if (Flags & SymbolRef::SF_Exported)
545       RTDyldSymFlags |= JITSymbolFlags::Exported;
546     DEBUG(dbgs() << "Allocating common symbol " << Name << " address "
547                  << format("%p", Addr) << "\n");
548     GlobalSymbolTable[Name] =
549       SymbolTableEntry(SectionID, Offset, RTDyldSymFlags);
550     Offset += Size;
551     Addr += Size;
552   }
553 
554   if (Checker)
555     Checker->registerSection(Obj.getFileName(), SectionID);
556 }
557 
emitSection(const ObjectFile & Obj,const SectionRef & Section,bool IsCode)558 unsigned RuntimeDyldImpl::emitSection(const ObjectFile &Obj,
559                                       const SectionRef &Section, bool IsCode) {
560 
561   StringRef data;
562   uint64_t Alignment64 = Section.getAlignment();
563 
564   unsigned Alignment = (unsigned)Alignment64 & 0xffffffffL;
565   unsigned PaddingSize = 0;
566   unsigned StubBufSize = 0;
567   StringRef Name;
568   bool IsRequired = isRequiredForExecution(Section);
569   bool IsVirtual = Section.isVirtual();
570   bool IsZeroInit = isZeroInit(Section);
571   bool IsReadOnly = isReadOnlyData(Section);
572   uint64_t DataSize = Section.getSize();
573   Check(Section.getName(Name));
574 
575   StubBufSize = computeSectionStubBufSize(Obj, Section);
576 
577   // The .eh_frame section (at least on Linux) needs an extra four bytes padded
578   // with zeroes added at the end.  For MachO objects, this section has a
579   // slightly different name, so this won't have any effect for MachO objects.
580   if (Name == ".eh_frame")
581     PaddingSize = 4;
582 
583   uintptr_t Allocate;
584   unsigned SectionID = Sections.size();
585   uint8_t *Addr;
586   const char *pData = nullptr;
587 
588   // If this section contains any bits (i.e. isn't a virtual or bss section),
589   // grab a reference to them.
590   if (!IsVirtual && !IsZeroInit) {
591     // In either case, set the location of the unrelocated section in memory,
592     // since we still process relocations for it even if we're not applying them.
593     Check(Section.getContents(data));
594     pData = data.data();
595   }
596 
597   // Code section alignment needs to be at least as high as stub alignment or
598   // padding calculations may by incorrect when the section is remapped to a
599   // higher alignment.
600   if (IsCode)
601     Alignment = std::max(Alignment, getStubAlignment());
602 
603   // Some sections, such as debug info, don't need to be loaded for execution.
604   // Leave those where they are.
605   if (IsRequired) {
606     Allocate = DataSize + PaddingSize + StubBufSize;
607     if (!Allocate)
608       Allocate = 1;
609     Addr = IsCode ? MemMgr.allocateCodeSection(Allocate, Alignment, SectionID,
610                                                Name)
611                   : MemMgr.allocateDataSection(Allocate, Alignment, SectionID,
612                                                Name, IsReadOnly);
613     if (!Addr)
614       report_fatal_error("Unable to allocate section memory!");
615 
616     // Zero-initialize or copy the data from the image
617     if (IsZeroInit || IsVirtual)
618       memset(Addr, 0, DataSize);
619     else
620       memcpy(Addr, pData, DataSize);
621 
622     // Fill in any extra bytes we allocated for padding
623     if (PaddingSize != 0) {
624       memset(Addr + DataSize, 0, PaddingSize);
625       // Update the DataSize variable so that the stub offset is set correctly.
626       DataSize += PaddingSize;
627     }
628 
629     DEBUG(dbgs() << "emitSection SectionID: " << SectionID << " Name: " << Name
630                  << " obj addr: " << format("%p", pData)
631                  << " new addr: " << format("%p", Addr)
632                  << " DataSize: " << DataSize << " StubBufSize: " << StubBufSize
633                  << " Allocate: " << Allocate << "\n");
634   } else {
635     // Even if we didn't load the section, we need to record an entry for it
636     // to handle later processing (and by 'handle' I mean don't do anything
637     // with these sections).
638     Allocate = 0;
639     Addr = nullptr;
640     DEBUG(dbgs() << "emitSection SectionID: " << SectionID << " Name: " << Name
641                  << " obj addr: " << format("%p", data.data()) << " new addr: 0"
642                  << " DataSize: " << DataSize << " StubBufSize: " << StubBufSize
643                  << " Allocate: " << Allocate << "\n");
644   }
645 
646   Sections.push_back(
647       SectionEntry(Name, Addr, DataSize, Allocate, (uintptr_t)pData));
648 
649   if (Checker)
650     Checker->registerSection(Obj.getFileName(), SectionID);
651 
652   return SectionID;
653 }
654 
findOrEmitSection(const ObjectFile & Obj,const SectionRef & Section,bool IsCode,ObjSectionToIDMap & LocalSections)655 unsigned RuntimeDyldImpl::findOrEmitSection(const ObjectFile &Obj,
656                                             const SectionRef &Section,
657                                             bool IsCode,
658                                             ObjSectionToIDMap &LocalSections) {
659 
660   unsigned SectionID = 0;
661   ObjSectionToIDMap::iterator i = LocalSections.find(Section);
662   if (i != LocalSections.end())
663     SectionID = i->second;
664   else {
665     SectionID = emitSection(Obj, Section, IsCode);
666     LocalSections[Section] = SectionID;
667   }
668   return SectionID;
669 }
670 
addRelocationForSection(const RelocationEntry & RE,unsigned SectionID)671 void RuntimeDyldImpl::addRelocationForSection(const RelocationEntry &RE,
672                                               unsigned SectionID) {
673   Relocations[SectionID].push_back(RE);
674 }
675 
addRelocationForSymbol(const RelocationEntry & RE,StringRef SymbolName)676 void RuntimeDyldImpl::addRelocationForSymbol(const RelocationEntry &RE,
677                                              StringRef SymbolName) {
678   // Relocation by symbol.  If the symbol is found in the global symbol table,
679   // create an appropriate section relocation.  Otherwise, add it to
680   // ExternalSymbolRelocations.
681   RTDyldSymbolTable::const_iterator Loc = GlobalSymbolTable.find(SymbolName);
682   if (Loc == GlobalSymbolTable.end()) {
683     ExternalSymbolRelocations[SymbolName].push_back(RE);
684   } else {
685     // Copy the RE since we want to modify its addend.
686     RelocationEntry RECopy = RE;
687     const auto &SymInfo = Loc->second;
688     RECopy.Addend += SymInfo.getOffset();
689     Relocations[SymInfo.getSectionID()].push_back(RECopy);
690   }
691 }
692 
createStubFunction(uint8_t * Addr,unsigned AbiVariant)693 uint8_t *RuntimeDyldImpl::createStubFunction(uint8_t *Addr,
694                                              unsigned AbiVariant) {
695   if (Arch == Triple::aarch64 || Arch == Triple::aarch64_be) {
696     // This stub has to be able to access the full address space,
697     // since symbol lookup won't necessarily find a handy, in-range,
698     // PLT stub for functions which could be anywhere.
699     // Stub can use ip0 (== x16) to calculate address
700     writeBytesUnaligned(0xd2e00010, Addr,    4); // movz ip0, #:abs_g3:<addr>
701     writeBytesUnaligned(0xf2c00010, Addr+4,  4); // movk ip0, #:abs_g2_nc:<addr>
702     writeBytesUnaligned(0xf2a00010, Addr+8,  4); // movk ip0, #:abs_g1_nc:<addr>
703     writeBytesUnaligned(0xf2800010, Addr+12, 4); // movk ip0, #:abs_g0_nc:<addr>
704     writeBytesUnaligned(0xd61f0200, Addr+16, 4); // br ip0
705 
706     return Addr;
707   } else if (Arch == Triple::arm || Arch == Triple::armeb) {
708     // TODO: There is only ARM far stub now. We should add the Thumb stub,
709     // and stubs for branches Thumb - ARM and ARM - Thumb.
710     writeBytesUnaligned(0xe51ff004, Addr, 4); // ldr pc,<label>
711     return Addr + 4;
712   } else if (IsMipsO32ABI) {
713     // 0:   3c190000        lui     t9,%hi(addr).
714     // 4:   27390000        addiu   t9,t9,%lo(addr).
715     // 8:   03200008        jr      t9.
716     // c:   00000000        nop.
717     const unsigned LuiT9Instr = 0x3c190000, AdduiT9Instr = 0x27390000;
718     const unsigned JrT9Instr = 0x03200008, NopInstr = 0x0;
719 
720     writeBytesUnaligned(LuiT9Instr, Addr, 4);
721     writeBytesUnaligned(AdduiT9Instr, Addr+4, 4);
722     writeBytesUnaligned(JrT9Instr, Addr+8, 4);
723     writeBytesUnaligned(NopInstr, Addr+12, 4);
724     return Addr;
725   } else if (Arch == Triple::ppc64 || Arch == Triple::ppc64le) {
726     // Depending on which version of the ELF ABI is in use, we need to
727     // generate one of two variants of the stub.  They both start with
728     // the same sequence to load the target address into r12.
729     writeInt32BE(Addr,    0x3D800000); // lis   r12, highest(addr)
730     writeInt32BE(Addr+4,  0x618C0000); // ori   r12, higher(addr)
731     writeInt32BE(Addr+8,  0x798C07C6); // sldi  r12, r12, 32
732     writeInt32BE(Addr+12, 0x658C0000); // oris  r12, r12, h(addr)
733     writeInt32BE(Addr+16, 0x618C0000); // ori   r12, r12, l(addr)
734     if (AbiVariant == 2) {
735       // PowerPC64 stub ELFv2 ABI: The address points to the function itself.
736       // The address is already in r12 as required by the ABI.  Branch to it.
737       writeInt32BE(Addr+20, 0xF8410018); // std   r2,  24(r1)
738       writeInt32BE(Addr+24, 0x7D8903A6); // mtctr r12
739       writeInt32BE(Addr+28, 0x4E800420); // bctr
740     } else {
741       // PowerPC64 stub ELFv1 ABI: The address points to a function descriptor.
742       // Load the function address on r11 and sets it to control register. Also
743       // loads the function TOC in r2 and environment pointer to r11.
744       writeInt32BE(Addr+20, 0xF8410028); // std   r2,  40(r1)
745       writeInt32BE(Addr+24, 0xE96C0000); // ld    r11, 0(r12)
746       writeInt32BE(Addr+28, 0xE84C0008); // ld    r2,  0(r12)
747       writeInt32BE(Addr+32, 0x7D6903A6); // mtctr r11
748       writeInt32BE(Addr+36, 0xE96C0010); // ld    r11, 16(r2)
749       writeInt32BE(Addr+40, 0x4E800420); // bctr
750     }
751     return Addr;
752   } else if (Arch == Triple::systemz) {
753     writeInt16BE(Addr,    0xC418);     // lgrl %r1,.+8
754     writeInt16BE(Addr+2,  0x0000);
755     writeInt16BE(Addr+4,  0x0004);
756     writeInt16BE(Addr+6,  0x07F1);     // brc 15,%r1
757     // 8-byte address stored at Addr + 8
758     return Addr;
759   } else if (Arch == Triple::x86_64) {
760     *Addr      = 0xFF; // jmp
761     *(Addr+1)  = 0x25; // rip
762     // 32-bit PC-relative address of the GOT entry will be stored at Addr+2
763   } else if (Arch == Triple::x86) {
764     *Addr      = 0xE9; // 32-bit pc-relative jump.
765   }
766   return Addr;
767 }
768 
769 // Assign an address to a symbol name and resolve all the relocations
770 // associated with it.
reassignSectionAddress(unsigned SectionID,uint64_t Addr)771 void RuntimeDyldImpl::reassignSectionAddress(unsigned SectionID,
772                                              uint64_t Addr) {
773   // The address to use for relocation resolution is not
774   // the address of the local section buffer. We must be doing
775   // a remote execution environment of some sort. Relocations can't
776   // be applied until all the sections have been moved.  The client must
777   // trigger this with a call to MCJIT::finalize() or
778   // RuntimeDyld::resolveRelocations().
779   //
780   // Addr is a uint64_t because we can't assume the pointer width
781   // of the target is the same as that of the host. Just use a generic
782   // "big enough" type.
783   DEBUG(dbgs() << "Reassigning address for section " << SectionID << " ("
784                << Sections[SectionID].getName() << "): "
785                << format("0x%016" PRIx64, Sections[SectionID].getLoadAddress())
786                << " -> " << format("0x%016" PRIx64, Addr) << "\n");
787   Sections[SectionID].setLoadAddress(Addr);
788 }
789 
resolveRelocationList(const RelocationList & Relocs,uint64_t Value)790 void RuntimeDyldImpl::resolveRelocationList(const RelocationList &Relocs,
791                                             uint64_t Value) {
792   for (unsigned i = 0, e = Relocs.size(); i != e; ++i) {
793     const RelocationEntry &RE = Relocs[i];
794     // Ignore relocations for sections that were not loaded
795     if (Sections[RE.SectionID].getAddress() == nullptr)
796       continue;
797     resolveRelocation(RE, Value);
798   }
799 }
800 
resolveExternalSymbols()801 void RuntimeDyldImpl::resolveExternalSymbols() {
802   while (!ExternalSymbolRelocations.empty()) {
803     StringMap<RelocationList>::iterator i = ExternalSymbolRelocations.begin();
804 
805     StringRef Name = i->first();
806     if (Name.size() == 0) {
807       // This is an absolute symbol, use an address of zero.
808       DEBUG(dbgs() << "Resolving absolute relocations."
809                    << "\n");
810       RelocationList &Relocs = i->second;
811       resolveRelocationList(Relocs, 0);
812     } else {
813       uint64_t Addr = 0;
814       RTDyldSymbolTable::const_iterator Loc = GlobalSymbolTable.find(Name);
815       if (Loc == GlobalSymbolTable.end()) {
816         // This is an external symbol, try to get its address from the symbol
817         // resolver.
818         Addr = Resolver.findSymbol(Name.data()).getAddress();
819         // The call to getSymbolAddress may have caused additional modules to
820         // be loaded, which may have added new entries to the
821         // ExternalSymbolRelocations map.  Consquently, we need to update our
822         // iterator.  This is also why retrieval of the relocation list
823         // associated with this symbol is deferred until below this point.
824         // New entries may have been added to the relocation list.
825         i = ExternalSymbolRelocations.find(Name);
826       } else {
827         // We found the symbol in our global table.  It was probably in a
828         // Module that we loaded previously.
829         const auto &SymInfo = Loc->second;
830         Addr = getSectionLoadAddress(SymInfo.getSectionID()) +
831                SymInfo.getOffset();
832       }
833 
834       // FIXME: Implement error handling that doesn't kill the host program!
835       if (!Addr)
836         report_fatal_error("Program used external function '" + Name +
837                            "' which could not be resolved!");
838 
839       // If Resolver returned UINT64_MAX, the client wants to handle this symbol
840       // manually and we shouldn't resolve its relocations.
841       if (Addr != UINT64_MAX) {
842         DEBUG(dbgs() << "Resolving relocations Name: " << Name << "\t"
843                      << format("0x%lx", Addr) << "\n");
844         // This list may have been updated when we called getSymbolAddress, so
845         // don't change this code to get the list earlier.
846         RelocationList &Relocs = i->second;
847         resolveRelocationList(Relocs, Addr);
848       }
849     }
850 
851     ExternalSymbolRelocations.erase(i);
852   }
853 }
854 
855 //===----------------------------------------------------------------------===//
856 // RuntimeDyld class implementation
857 
getSectionLoadAddress(const object::SectionRef & Sec) const858 uint64_t RuntimeDyld::LoadedObjectInfo::getSectionLoadAddress(
859                                           const object::SectionRef &Sec) const {
860 
861   auto I = ObjSecToIDMap.find(Sec);
862   if (I != ObjSecToIDMap.end())
863     return RTDyld.Sections[I->second].getLoadAddress();
864 
865   return 0;
866 }
867 
anchor()868 void RuntimeDyld::MemoryManager::anchor() {}
anchor()869 void RuntimeDyld::SymbolResolver::anchor() {}
870 
RuntimeDyld(RuntimeDyld::MemoryManager & MemMgr,RuntimeDyld::SymbolResolver & Resolver)871 RuntimeDyld::RuntimeDyld(RuntimeDyld::MemoryManager &MemMgr,
872                          RuntimeDyld::SymbolResolver &Resolver)
873     : MemMgr(MemMgr), Resolver(Resolver) {
874   // FIXME: There's a potential issue lurking here if a single instance of
875   // RuntimeDyld is used to load multiple objects.  The current implementation
876   // associates a single memory manager with a RuntimeDyld instance.  Even
877   // though the public class spawns a new 'impl' instance for each load,
878   // they share a single memory manager.  This can become a problem when page
879   // permissions are applied.
880   Dyld = nullptr;
881   ProcessAllSections = false;
882   Checker = nullptr;
883 }
884 
~RuntimeDyld()885 RuntimeDyld::~RuntimeDyld() {}
886 
887 static std::unique_ptr<RuntimeDyldCOFF>
createRuntimeDyldCOFF(Triple::ArchType Arch,RuntimeDyld::MemoryManager & MM,RuntimeDyld::SymbolResolver & Resolver,bool ProcessAllSections,RuntimeDyldCheckerImpl * Checker)888 createRuntimeDyldCOFF(Triple::ArchType Arch, RuntimeDyld::MemoryManager &MM,
889                       RuntimeDyld::SymbolResolver &Resolver,
890                       bool ProcessAllSections, RuntimeDyldCheckerImpl *Checker) {
891   std::unique_ptr<RuntimeDyldCOFF> Dyld =
892     RuntimeDyldCOFF::create(Arch, MM, Resolver);
893   Dyld->setProcessAllSections(ProcessAllSections);
894   Dyld->setRuntimeDyldChecker(Checker);
895   return Dyld;
896 }
897 
898 static std::unique_ptr<RuntimeDyldELF>
createRuntimeDyldELF(RuntimeDyld::MemoryManager & MM,RuntimeDyld::SymbolResolver & Resolver,bool ProcessAllSections,RuntimeDyldCheckerImpl * Checker)899 createRuntimeDyldELF(RuntimeDyld::MemoryManager &MM,
900                      RuntimeDyld::SymbolResolver &Resolver,
901                      bool ProcessAllSections, RuntimeDyldCheckerImpl *Checker) {
902   std::unique_ptr<RuntimeDyldELF> Dyld(new RuntimeDyldELF(MM, Resolver));
903   Dyld->setProcessAllSections(ProcessAllSections);
904   Dyld->setRuntimeDyldChecker(Checker);
905   return Dyld;
906 }
907 
908 static std::unique_ptr<RuntimeDyldMachO>
createRuntimeDyldMachO(Triple::ArchType Arch,RuntimeDyld::MemoryManager & MM,RuntimeDyld::SymbolResolver & Resolver,bool ProcessAllSections,RuntimeDyldCheckerImpl * Checker)909 createRuntimeDyldMachO(Triple::ArchType Arch, RuntimeDyld::MemoryManager &MM,
910                        RuntimeDyld::SymbolResolver &Resolver,
911                        bool ProcessAllSections,
912                        RuntimeDyldCheckerImpl *Checker) {
913   std::unique_ptr<RuntimeDyldMachO> Dyld =
914     RuntimeDyldMachO::create(Arch, MM, Resolver);
915   Dyld->setProcessAllSections(ProcessAllSections);
916   Dyld->setRuntimeDyldChecker(Checker);
917   return Dyld;
918 }
919 
920 std::unique_ptr<RuntimeDyld::LoadedObjectInfo>
loadObject(const ObjectFile & Obj)921 RuntimeDyld::loadObject(const ObjectFile &Obj) {
922   if (!Dyld) {
923     if (Obj.isELF())
924       Dyld = createRuntimeDyldELF(MemMgr, Resolver, ProcessAllSections, Checker);
925     else if (Obj.isMachO())
926       Dyld = createRuntimeDyldMachO(
927                static_cast<Triple::ArchType>(Obj.getArch()), MemMgr, Resolver,
928                ProcessAllSections, Checker);
929     else if (Obj.isCOFF())
930       Dyld = createRuntimeDyldCOFF(
931                static_cast<Triple::ArchType>(Obj.getArch()), MemMgr, Resolver,
932                ProcessAllSections, Checker);
933     else
934       report_fatal_error("Incompatible object format!");
935   }
936 
937   if (!Dyld->isCompatibleFile(Obj))
938     report_fatal_error("Incompatible object format!");
939 
940   return Dyld->loadObject(Obj);
941 }
942 
getSymbolLocalAddress(StringRef Name) const943 void *RuntimeDyld::getSymbolLocalAddress(StringRef Name) const {
944   if (!Dyld)
945     return nullptr;
946   return Dyld->getSymbolLocalAddress(Name);
947 }
948 
getSymbol(StringRef Name) const949 RuntimeDyld::SymbolInfo RuntimeDyld::getSymbol(StringRef Name) const {
950   if (!Dyld)
951     return nullptr;
952   return Dyld->getSymbol(Name);
953 }
954 
resolveRelocations()955 void RuntimeDyld::resolveRelocations() { Dyld->resolveRelocations(); }
956 
reassignSectionAddress(unsigned SectionID,uint64_t Addr)957 void RuntimeDyld::reassignSectionAddress(unsigned SectionID, uint64_t Addr) {
958   Dyld->reassignSectionAddress(SectionID, Addr);
959 }
960 
mapSectionAddress(const void * LocalAddress,uint64_t TargetAddress)961 void RuntimeDyld::mapSectionAddress(const void *LocalAddress,
962                                     uint64_t TargetAddress) {
963   Dyld->mapSectionAddress(LocalAddress, TargetAddress);
964 }
965 
hasError()966 bool RuntimeDyld::hasError() { return Dyld->hasError(); }
967 
getErrorString()968 StringRef RuntimeDyld::getErrorString() { return Dyld->getErrorString(); }
969 
registerEHFrames()970 void RuntimeDyld::registerEHFrames() {
971   if (Dyld)
972     Dyld->registerEHFrames();
973 }
974 
deregisterEHFrames()975 void RuntimeDyld::deregisterEHFrames() {
976   if (Dyld)
977     Dyld->deregisterEHFrames();
978 }
979 
980 } // end namespace llvm
981