1 //===-- DWARFContext.cpp --------------------------------------------------===//
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 #include "llvm/DebugInfo/DWARF/DWARFContext.h"
11 #include "llvm/ADT/SmallString.h"
12 #include "llvm/ADT/StringSwitch.h"
13 #include "llvm/DebugInfo/DWARF/DWARFAcceleratorTable.h"
14 #include "llvm/DebugInfo/DWARF/DWARFDebugArangeSet.h"
15 #include "llvm/DebugInfo/DWARF/DWARFDebugPubTable.h"
16 #include "llvm/DebugInfo/DWARF/DWARFUnitIndex.h"
17 #include "llvm/Object/Decompressor.h"
18 #include "llvm/Object/MachO.h"
19 #include "llvm/Object/RelocVisitor.h"
20 #include "llvm/Support/Compression.h"
21 #include "llvm/Support/Dwarf.h"
22 #include "llvm/Support/ELF.h"
23 #include "llvm/Support/Format.h"
24 #include "llvm/Support/Path.h"
25 #include "llvm/Support/raw_ostream.h"
26 #include <algorithm>
27 using namespace llvm;
28 using namespace dwarf;
29 using namespace object;
30 
31 #define DEBUG_TYPE "dwarf"
32 
33 typedef DWARFDebugLine::LineTable DWARFLineTable;
34 typedef DILineInfoSpecifier::FileLineInfoKind FileLineInfoKind;
35 typedef DILineInfoSpecifier::FunctionNameKind FunctionNameKind;
36 
37 static void dumpAccelSection(raw_ostream &OS, StringRef Name,
38                              const DWARFSection& Section, StringRef StringSection,
39                              bool LittleEndian) {
40   DataExtractor AccelSection(Section.Data, LittleEndian, 0);
41   DataExtractor StrData(StringSection, LittleEndian, 0);
42   OS << "\n." << Name << " contents:\n";
43   DWARFAcceleratorTable Accel(AccelSection, StrData, Section.Relocs);
44   if (!Accel.extract())
45     return;
46   Accel.dump(OS);
47 }
48 
49 void DWARFContext::dump(raw_ostream &OS, DIDumpType DumpType, bool DumpEH,
50                         bool SummarizeTypes) {
51   if (DumpType == DIDT_All || DumpType == DIDT_Abbrev) {
52     OS << ".debug_abbrev contents:\n";
53     getDebugAbbrev()->dump(OS);
54   }
55 
56   if (DumpType == DIDT_All || DumpType == DIDT_AbbrevDwo)
57     if (const DWARFDebugAbbrev *D = getDebugAbbrevDWO()) {
58       OS << "\n.debug_abbrev.dwo contents:\n";
59       D->dump(OS);
60     }
61 
62   if (DumpType == DIDT_All || DumpType == DIDT_Info) {
63     OS << "\n.debug_info contents:\n";
64     for (const auto &CU : compile_units())
65       CU->dump(OS);
66   }
67 
68   if ((DumpType == DIDT_All || DumpType == DIDT_InfoDwo) &&
69       getNumDWOCompileUnits()) {
70     OS << "\n.debug_info.dwo contents:\n";
71     for (const auto &DWOCU : dwo_compile_units())
72       DWOCU->dump(OS);
73   }
74 
75   if ((DumpType == DIDT_All || DumpType == DIDT_Types) && getNumTypeUnits()) {
76     OS << "\n.debug_types contents:\n";
77     for (const auto &TUS : type_unit_sections())
78       for (const auto &TU : TUS)
79         TU->dump(OS, SummarizeTypes);
80   }
81 
82   if ((DumpType == DIDT_All || DumpType == DIDT_TypesDwo) &&
83       getNumDWOTypeUnits()) {
84     OS << "\n.debug_types.dwo contents:\n";
85     for (const auto &DWOTUS : dwo_type_unit_sections())
86       for (const auto &DWOTU : DWOTUS)
87         DWOTU->dump(OS, SummarizeTypes);
88   }
89 
90   if (DumpType == DIDT_All || DumpType == DIDT_Loc) {
91     OS << "\n.debug_loc contents:\n";
92     getDebugLoc()->dump(OS);
93   }
94 
95   if (DumpType == DIDT_All || DumpType == DIDT_LocDwo) {
96     OS << "\n.debug_loc.dwo contents:\n";
97     getDebugLocDWO()->dump(OS);
98   }
99 
100   if (DumpType == DIDT_All || DumpType == DIDT_Frames) {
101     OS << "\n.debug_frame contents:\n";
102     getDebugFrame()->dump(OS);
103     if (DumpEH) {
104       OS << "\n.eh_frame contents:\n";
105       getEHFrame()->dump(OS);
106     }
107   }
108 
109   if (DumpType == DIDT_All || DumpType == DIDT_Macro) {
110     OS << "\n.debug_macinfo contents:\n";
111     getDebugMacro()->dump(OS);
112   }
113 
114   uint32_t offset = 0;
115   if (DumpType == DIDT_All || DumpType == DIDT_Aranges) {
116     OS << "\n.debug_aranges contents:\n";
117     DataExtractor arangesData(getARangeSection(), isLittleEndian(), 0);
118     DWARFDebugArangeSet set;
119     while (set.extract(arangesData, &offset))
120       set.dump(OS);
121   }
122 
123   uint8_t savedAddressByteSize = 0;
124   if (DumpType == DIDT_All || DumpType == DIDT_Line) {
125     OS << "\n.debug_line contents:\n";
126     for (const auto &CU : compile_units()) {
127       savedAddressByteSize = CU->getAddressByteSize();
128       auto CUDIE = CU->getUnitDIE();
129       if (!CUDIE)
130         continue;
131       if (auto StmtOffset = toSectionOffset(CUDIE.find(DW_AT_stmt_list))) {
132         DataExtractor lineData(getLineSection().Data, isLittleEndian(),
133                                savedAddressByteSize);
134         DWARFDebugLine::LineTable LineTable;
135         uint32_t Offset = *StmtOffset;
136         LineTable.parse(lineData, &getLineSection().Relocs, &Offset);
137         LineTable.dump(OS);
138       }
139     }
140   }
141 
142   if (DumpType == DIDT_All || DumpType == DIDT_CUIndex) {
143     OS << "\n.debug_cu_index contents:\n";
144     getCUIndex().dump(OS);
145   }
146 
147   if (DumpType == DIDT_All || DumpType == DIDT_TUIndex) {
148     OS << "\n.debug_tu_index contents:\n";
149     getTUIndex().dump(OS);
150   }
151 
152   if (DumpType == DIDT_All || DumpType == DIDT_LineDwo) {
153     OS << "\n.debug_line.dwo contents:\n";
154     unsigned stmtOffset = 0;
155     DataExtractor lineData(getLineDWOSection().Data, isLittleEndian(),
156                            savedAddressByteSize);
157     DWARFDebugLine::LineTable LineTable;
158     while (LineTable.Prologue.parse(lineData, &stmtOffset)) {
159       LineTable.dump(OS);
160       LineTable.clear();
161     }
162   }
163 
164   if (DumpType == DIDT_All || DumpType == DIDT_Str) {
165     OS << "\n.debug_str contents:\n";
166     DataExtractor strData(getStringSection(), isLittleEndian(), 0);
167     offset = 0;
168     uint32_t strOffset = 0;
169     while (const char *s = strData.getCStr(&offset)) {
170       OS << format("0x%8.8x: \"%s\"\n", strOffset, s);
171       strOffset = offset;
172     }
173   }
174 
175   if ((DumpType == DIDT_All || DumpType == DIDT_StrDwo) &&
176       !getStringDWOSection().empty()) {
177     OS << "\n.debug_str.dwo contents:\n";
178     DataExtractor strDWOData(getStringDWOSection(), isLittleEndian(), 0);
179     offset = 0;
180     uint32_t strDWOOffset = 0;
181     while (const char *s = strDWOData.getCStr(&offset)) {
182       OS << format("0x%8.8x: \"%s\"\n", strDWOOffset, s);
183       strDWOOffset = offset;
184     }
185   }
186 
187   if (DumpType == DIDT_All || DumpType == DIDT_Ranges) {
188     OS << "\n.debug_ranges contents:\n";
189     // In fact, different compile units may have different address byte
190     // sizes, but for simplicity we just use the address byte size of the last
191     // compile unit (there is no easy and fast way to associate address range
192     // list and the compile unit it describes).
193     DataExtractor rangesData(getRangeSection(), isLittleEndian(),
194                              savedAddressByteSize);
195     offset = 0;
196     DWARFDebugRangeList rangeList;
197     while (rangeList.extract(rangesData, &offset))
198       rangeList.dump(OS);
199   }
200 
201   if (DumpType == DIDT_All || DumpType == DIDT_Pubnames)
202     DWARFDebugPubTable(getPubNamesSection(), isLittleEndian(), false)
203         .dump("debug_pubnames", OS);
204 
205   if (DumpType == DIDT_All || DumpType == DIDT_Pubtypes)
206     DWARFDebugPubTable(getPubTypesSection(), isLittleEndian(), false)
207         .dump("debug_pubtypes", OS);
208 
209   if (DumpType == DIDT_All || DumpType == DIDT_GnuPubnames)
210     DWARFDebugPubTable(getGnuPubNamesSection(), isLittleEndian(),
211                        true /* GnuStyle */)
212         .dump("debug_gnu_pubnames", OS);
213 
214   if (DumpType == DIDT_All || DumpType == DIDT_GnuPubtypes)
215     DWARFDebugPubTable(getGnuPubTypesSection(), isLittleEndian(),
216                        true /* GnuStyle */)
217         .dump("debug_gnu_pubtypes", OS);
218 
219   if ((DumpType == DIDT_All || DumpType == DIDT_StrOffsetsDwo) &&
220       !getStringOffsetDWOSection().empty()) {
221     OS << "\n.debug_str_offsets.dwo contents:\n";
222     DataExtractor strOffsetExt(getStringOffsetDWOSection(), isLittleEndian(),
223                                0);
224     offset = 0;
225     uint64_t size = getStringOffsetDWOSection().size();
226     while (offset < size) {
227       OS << format("0x%8.8x: ", offset);
228       OS << format("%8.8x\n", strOffsetExt.getU32(&offset));
229     }
230   }
231 
232   if ((DumpType == DIDT_All || DumpType == DIDT_GdbIndex) &&
233       !getGdbIndexSection().empty()) {
234     OS << "\n.gnu_index contents:\n";
235     getGdbIndex().dump(OS);
236   }
237 
238   if (DumpType == DIDT_All || DumpType == DIDT_AppleNames)
239     dumpAccelSection(OS, "apple_names", getAppleNamesSection(),
240                      getStringSection(), isLittleEndian());
241 
242   if (DumpType == DIDT_All || DumpType == DIDT_AppleTypes)
243     dumpAccelSection(OS, "apple_types", getAppleTypesSection(),
244                      getStringSection(), isLittleEndian());
245 
246   if (DumpType == DIDT_All || DumpType == DIDT_AppleNamespaces)
247     dumpAccelSection(OS, "apple_namespaces", getAppleNamespacesSection(),
248                      getStringSection(), isLittleEndian());
249 
250   if (DumpType == DIDT_All || DumpType == DIDT_AppleObjC)
251     dumpAccelSection(OS, "apple_objc", getAppleObjCSection(),
252                      getStringSection(), isLittleEndian());
253 }
254 
255 const DWARFUnitIndex &DWARFContext::getCUIndex() {
256   if (CUIndex)
257     return *CUIndex;
258 
259   DataExtractor CUIndexData(getCUIndexSection(), isLittleEndian(), 0);
260 
261   CUIndex = llvm::make_unique<DWARFUnitIndex>(DW_SECT_INFO);
262   CUIndex->parse(CUIndexData);
263   return *CUIndex;
264 }
265 
266 const DWARFUnitIndex &DWARFContext::getTUIndex() {
267   if (TUIndex)
268     return *TUIndex;
269 
270   DataExtractor TUIndexData(getTUIndexSection(), isLittleEndian(), 0);
271 
272   TUIndex = llvm::make_unique<DWARFUnitIndex>(DW_SECT_TYPES);
273   TUIndex->parse(TUIndexData);
274   return *TUIndex;
275 }
276 
277 DWARFGdbIndex &DWARFContext::getGdbIndex() {
278   if (GdbIndex)
279     return *GdbIndex;
280 
281   DataExtractor GdbIndexData(getGdbIndexSection(), true /*LE*/, 0);
282   GdbIndex = llvm::make_unique<DWARFGdbIndex>();
283   GdbIndex->parse(GdbIndexData);
284   return *GdbIndex;
285 }
286 
287 const DWARFDebugAbbrev *DWARFContext::getDebugAbbrev() {
288   if (Abbrev)
289     return Abbrev.get();
290 
291   DataExtractor abbrData(getAbbrevSection(), isLittleEndian(), 0);
292 
293   Abbrev.reset(new DWARFDebugAbbrev());
294   Abbrev->extract(abbrData);
295   return Abbrev.get();
296 }
297 
298 const DWARFDebugAbbrev *DWARFContext::getDebugAbbrevDWO() {
299   if (AbbrevDWO)
300     return AbbrevDWO.get();
301 
302   DataExtractor abbrData(getAbbrevDWOSection(), isLittleEndian(), 0);
303   AbbrevDWO.reset(new DWARFDebugAbbrev());
304   AbbrevDWO->extract(abbrData);
305   return AbbrevDWO.get();
306 }
307 
308 const DWARFDebugLoc *DWARFContext::getDebugLoc() {
309   if (Loc)
310     return Loc.get();
311 
312   DataExtractor LocData(getLocSection().Data, isLittleEndian(), 0);
313   Loc.reset(new DWARFDebugLoc(getLocSection().Relocs));
314   // assume all compile units have the same address byte size
315   if (getNumCompileUnits())
316     Loc->parse(LocData, getCompileUnitAtIndex(0)->getAddressByteSize());
317   return Loc.get();
318 }
319 
320 const DWARFDebugLocDWO *DWARFContext::getDebugLocDWO() {
321   if (LocDWO)
322     return LocDWO.get();
323 
324   DataExtractor LocData(getLocDWOSection().Data, isLittleEndian(), 0);
325   LocDWO.reset(new DWARFDebugLocDWO());
326   LocDWO->parse(LocData);
327   return LocDWO.get();
328 }
329 
330 const DWARFDebugAranges *DWARFContext::getDebugAranges() {
331   if (Aranges)
332     return Aranges.get();
333 
334   Aranges.reset(new DWARFDebugAranges());
335   Aranges->generate(this);
336   return Aranges.get();
337 }
338 
339 const DWARFDebugFrame *DWARFContext::getDebugFrame() {
340   if (DebugFrame)
341     return DebugFrame.get();
342 
343   // There's a "bug" in the DWARFv3 standard with respect to the target address
344   // size within debug frame sections. While DWARF is supposed to be independent
345   // of its container, FDEs have fields with size being "target address size",
346   // which isn't specified in DWARF in general. It's only specified for CUs, but
347   // .eh_frame can appear without a .debug_info section. Follow the example of
348   // other tools (libdwarf) and extract this from the container (ObjectFile
349   // provides this information). This problem is fixed in DWARFv4
350   // See this dwarf-discuss discussion for more details:
351   // http://lists.dwarfstd.org/htdig.cgi/dwarf-discuss-dwarfstd.org/2011-December/001173.html
352   DataExtractor debugFrameData(getDebugFrameSection(), isLittleEndian(),
353                                getAddressSize());
354   DebugFrame.reset(new DWARFDebugFrame(false /* IsEH */));
355   DebugFrame->parse(debugFrameData);
356   return DebugFrame.get();
357 }
358 
359 const DWARFDebugFrame *DWARFContext::getEHFrame() {
360   if (EHFrame)
361     return EHFrame.get();
362 
363   DataExtractor debugFrameData(getEHFrameSection(), isLittleEndian(),
364                                getAddressSize());
365   DebugFrame.reset(new DWARFDebugFrame(true /* IsEH */));
366   DebugFrame->parse(debugFrameData);
367   return DebugFrame.get();
368 }
369 
370 const DWARFDebugMacro *DWARFContext::getDebugMacro() {
371   if (Macro)
372     return Macro.get();
373 
374   DataExtractor MacinfoData(getMacinfoSection(), isLittleEndian(), 0);
375   Macro.reset(new DWARFDebugMacro());
376   Macro->parse(MacinfoData);
377   return Macro.get();
378 }
379 
380 const DWARFLineTable *
381 DWARFContext::getLineTableForUnit(DWARFUnit *U) {
382   if (!Line)
383     Line.reset(new DWARFDebugLine(&getLineSection().Relocs));
384 
385   auto UnitDIE = U->getUnitDIE();
386   if (!UnitDIE)
387     return nullptr;
388 
389   auto Offset = toSectionOffset(UnitDIE.find(DW_AT_stmt_list));
390   if (!Offset)
391     return nullptr; // No line table for this compile unit.
392 
393   uint32_t stmtOffset = *Offset + U->getLineTableOffset();
394   // See if the line table is cached.
395   if (const DWARFLineTable *lt = Line->getLineTable(stmtOffset))
396     return lt;
397 
398   // We have to parse it first.
399   DataExtractor lineData(U->getLineSection(), isLittleEndian(),
400                          U->getAddressByteSize());
401   return Line->getOrParseLineTable(lineData, stmtOffset);
402 }
403 
404 void DWARFContext::parseCompileUnits() {
405   CUs.parse(*this, getInfoSection());
406 }
407 
408 void DWARFContext::parseTypeUnits() {
409   if (!TUs.empty())
410     return;
411   for (const auto &I : getTypesSections()) {
412     TUs.emplace_back();
413     TUs.back().parse(*this, I.second);
414   }
415 }
416 
417 void DWARFContext::parseDWOCompileUnits() {
418   DWOCUs.parseDWO(*this, getInfoDWOSection());
419 }
420 
421 void DWARFContext::parseDWOTypeUnits() {
422   if (!DWOTUs.empty())
423     return;
424   for (const auto &I : getTypesDWOSections()) {
425     DWOTUs.emplace_back();
426     DWOTUs.back().parseDWO(*this, I.second);
427   }
428 }
429 
430 DWARFCompileUnit *DWARFContext::getCompileUnitForOffset(uint32_t Offset) {
431   parseCompileUnits();
432   return CUs.getUnitForOffset(Offset);
433 }
434 
435 DWARFCompileUnit *DWARFContext::getCompileUnitForAddress(uint64_t Address) {
436   // First, get the offset of the compile unit.
437   uint32_t CUOffset = getDebugAranges()->findAddress(Address);
438   // Retrieve the compile unit.
439   return getCompileUnitForOffset(CUOffset);
440 }
441 
442 static bool getFunctionNameForAddress(DWARFCompileUnit *CU, uint64_t Address,
443                                       FunctionNameKind Kind,
444                                       std::string &FunctionName) {
445   if (Kind == FunctionNameKind::None)
446     return false;
447   // The address may correspond to instruction in some inlined function,
448   // so we have to build the chain of inlined functions and take the
449   // name of the topmost function in it.SmallVectorImpl<DWARFDie> &InlinedChain
450   SmallVector<DWARFDie, 4> InlinedChain;
451   CU->getInlinedChainForAddress(Address, InlinedChain);
452   if (InlinedChain.size() == 0)
453     return false;
454   if (const char *Name = InlinedChain[0].getSubroutineName(Kind)) {
455     FunctionName = Name;
456     return true;
457   }
458   return false;
459 }
460 
461 DILineInfo DWARFContext::getLineInfoForAddress(uint64_t Address,
462                                                DILineInfoSpecifier Spec) {
463   DILineInfo Result;
464 
465   DWARFCompileUnit *CU = getCompileUnitForAddress(Address);
466   if (!CU)
467     return Result;
468   getFunctionNameForAddress(CU, Address, Spec.FNKind, Result.FunctionName);
469   if (Spec.FLIKind != FileLineInfoKind::None) {
470     if (const DWARFLineTable *LineTable = getLineTableForUnit(CU))
471       LineTable->getFileLineInfoForAddress(Address, CU->getCompilationDir(),
472                                            Spec.FLIKind, Result);
473   }
474   return Result;
475 }
476 
477 DILineInfoTable
478 DWARFContext::getLineInfoForAddressRange(uint64_t Address, uint64_t Size,
479                                          DILineInfoSpecifier Spec) {
480   DILineInfoTable  Lines;
481   DWARFCompileUnit *CU = getCompileUnitForAddress(Address);
482   if (!CU)
483     return Lines;
484 
485   std::string FunctionName = "<invalid>";
486   getFunctionNameForAddress(CU, Address, Spec.FNKind, FunctionName);
487 
488   // If the Specifier says we don't need FileLineInfo, just
489   // return the top-most function at the starting address.
490   if (Spec.FLIKind == FileLineInfoKind::None) {
491     DILineInfo Result;
492     Result.FunctionName = FunctionName;
493     Lines.push_back(std::make_pair(Address, Result));
494     return Lines;
495   }
496 
497   const DWARFLineTable *LineTable = getLineTableForUnit(CU);
498 
499   // Get the index of row we're looking for in the line table.
500   std::vector<uint32_t> RowVector;
501   if (!LineTable->lookupAddressRange(Address, Size, RowVector))
502     return Lines;
503 
504   for (uint32_t RowIndex : RowVector) {
505     // Take file number and line/column from the row.
506     const DWARFDebugLine::Row &Row = LineTable->Rows[RowIndex];
507     DILineInfo Result;
508     LineTable->getFileNameByIndex(Row.File, CU->getCompilationDir(),
509                                   Spec.FLIKind, Result.FileName);
510     Result.FunctionName = FunctionName;
511     Result.Line = Row.Line;
512     Result.Column = Row.Column;
513     Lines.push_back(std::make_pair(Row.Address, Result));
514   }
515 
516   return Lines;
517 }
518 
519 DIInliningInfo
520 DWARFContext::getInliningInfoForAddress(uint64_t Address,
521                                         DILineInfoSpecifier Spec) {
522   DIInliningInfo InliningInfo;
523 
524   DWARFCompileUnit *CU = getCompileUnitForAddress(Address);
525   if (!CU)
526     return InliningInfo;
527 
528   const DWARFLineTable *LineTable = nullptr;
529   SmallVector<DWARFDie, 4> InlinedChain;
530   CU->getInlinedChainForAddress(Address, InlinedChain);
531   if (InlinedChain.size() == 0) {
532     // If there is no DIE for address (e.g. it is in unavailable .dwo file),
533     // try to at least get file/line info from symbol table.
534     if (Spec.FLIKind != FileLineInfoKind::None) {
535       DILineInfo Frame;
536       LineTable = getLineTableForUnit(CU);
537       if (LineTable &&
538           LineTable->getFileLineInfoForAddress(Address, CU->getCompilationDir(),
539                                                Spec.FLIKind, Frame))
540         InliningInfo.addFrame(Frame);
541     }
542     return InliningInfo;
543   }
544 
545   uint32_t CallFile = 0, CallLine = 0, CallColumn = 0;
546   for (uint32_t i = 0, n = InlinedChain.size(); i != n; i++) {
547     DWARFDie &FunctionDIE = InlinedChain[i];
548     DILineInfo Frame;
549     // Get function name if necessary.
550     if (const char *Name = FunctionDIE.getSubroutineName(Spec.FNKind))
551       Frame.FunctionName = Name;
552     if (Spec.FLIKind != FileLineInfoKind::None) {
553       if (i == 0) {
554         // For the topmost frame, initialize the line table of this
555         // compile unit and fetch file/line info from it.
556         LineTable = getLineTableForUnit(CU);
557         // For the topmost routine, get file/line info from line table.
558         if (LineTable)
559           LineTable->getFileLineInfoForAddress(Address, CU->getCompilationDir(),
560                                                Spec.FLIKind, Frame);
561       } else {
562         // Otherwise, use call file, call line and call column from
563         // previous DIE in inlined chain.
564         if (LineTable)
565           LineTable->getFileNameByIndex(CallFile, CU->getCompilationDir(),
566                                         Spec.FLIKind, Frame.FileName);
567         Frame.Line = CallLine;
568         Frame.Column = CallColumn;
569       }
570       // Get call file/line/column of a current DIE.
571       if (i + 1 < n) {
572         FunctionDIE.getCallerFrame(CallFile, CallLine, CallColumn);
573       }
574     }
575     InliningInfo.addFrame(Frame);
576   }
577   return InliningInfo;
578 }
579 
580 DWARFContextInMemory::DWARFContextInMemory(const object::ObjectFile &Obj,
581     const LoadedObjectInfo *L)
582     : IsLittleEndian(Obj.isLittleEndian()),
583       AddressSize(Obj.getBytesInAddress()) {
584   for (const SectionRef &Section : Obj.sections()) {
585     StringRef name;
586     Section.getName(name);
587     // Skip BSS and Virtual sections, they aren't interesting.
588     bool IsBSS = Section.isBSS();
589     if (IsBSS)
590       continue;
591     bool IsVirtual = Section.isVirtual();
592     if (IsVirtual)
593       continue;
594     StringRef data;
595 
596     section_iterator RelocatedSection = Section.getRelocatedSection();
597     // Try to obtain an already relocated version of this section.
598     // Else use the unrelocated section from the object file. We'll have to
599     // apply relocations ourselves later.
600     if (!L || !L->getLoadedSectionContents(*RelocatedSection,data))
601       Section.getContents(data);
602 
603     if (Decompressor::isCompressed(Section)) {
604       Expected<Decompressor> Decompressor =
605           Decompressor::create(name, data, IsLittleEndian, AddressSize == 8);
606       if (!Decompressor)
607         continue;
608       SmallString<32> Out;
609       if (auto Err = Decompressor->decompress(Out))
610         continue;
611       UncompressedSections.emplace_back(std::move(Out));
612       data = UncompressedSections.back();
613     }
614 
615     // Compressed sections names in GNU style starts from ".z",
616     // at this point section is decompressed and we drop compression prefix.
617     name = name.substr(
618         name.find_first_not_of("._z")); // Skip ".", "z" and "_" prefixes.
619 
620     StringRef *SectionData =
621         StringSwitch<StringRef *>(name)
622             .Case("debug_info", &InfoSection.Data)
623             .Case("debug_abbrev", &AbbrevSection)
624             .Case("debug_loc", &LocSection.Data)
625             .Case("debug_line", &LineSection.Data)
626             .Case("debug_aranges", &ARangeSection)
627             .Case("debug_frame", &DebugFrameSection)
628             .Case("eh_frame", &EHFrameSection)
629             .Case("debug_str", &StringSection)
630             .Case("debug_ranges", &RangeSection)
631             .Case("debug_macinfo", &MacinfoSection)
632             .Case("debug_pubnames", &PubNamesSection)
633             .Case("debug_pubtypes", &PubTypesSection)
634             .Case("debug_gnu_pubnames", &GnuPubNamesSection)
635             .Case("debug_gnu_pubtypes", &GnuPubTypesSection)
636             .Case("debug_info.dwo", &InfoDWOSection.Data)
637             .Case("debug_abbrev.dwo", &AbbrevDWOSection)
638             .Case("debug_loc.dwo", &LocDWOSection.Data)
639             .Case("debug_line.dwo", &LineDWOSection.Data)
640             .Case("debug_str.dwo", &StringDWOSection)
641             .Case("debug_str_offsets.dwo", &StringOffsetDWOSection)
642             .Case("debug_addr", &AddrSection)
643             .Case("apple_names", &AppleNamesSection.Data)
644             .Case("apple_types", &AppleTypesSection.Data)
645             .Case("apple_namespaces", &AppleNamespacesSection.Data)
646             .Case("apple_namespac", &AppleNamespacesSection.Data)
647             .Case("apple_objc", &AppleObjCSection.Data)
648             .Case("debug_cu_index", &CUIndexSection)
649             .Case("debug_tu_index", &TUIndexSection)
650             .Case("gdb_index", &GdbIndexSection)
651             // Any more debug info sections go here.
652             .Default(nullptr);
653     if (SectionData) {
654       *SectionData = data;
655       if (name == "debug_ranges") {
656         // FIXME: Use the other dwo range section when we emit it.
657         RangeDWOSection = data;
658       }
659     } else if (name == "debug_types") {
660       // Find debug_types data by section rather than name as there are
661       // multiple, comdat grouped, debug_types sections.
662       TypesSections[Section].Data = data;
663     } else if (name == "debug_types.dwo") {
664       TypesDWOSections[Section].Data = data;
665     }
666 
667     if (RelocatedSection == Obj.section_end())
668       continue;
669 
670     StringRef RelSecName;
671     StringRef RelSecData;
672     RelocatedSection->getName(RelSecName);
673 
674     // If the section we're relocating was relocated already by the JIT,
675     // then we used the relocated version above, so we do not need to process
676     // relocations for it now.
677     if (L && L->getLoadedSectionContents(*RelocatedSection,RelSecData))
678       continue;
679 
680     // In Mach-o files, the relocations do not need to be applied if
681     // there is no load offset to apply. The value read at the
682     // relocation point already factors in the section address
683     // (actually applying the relocations will produce wrong results
684     // as the section address will be added twice).
685     if (!L && isa<MachOObjectFile>(&Obj))
686       continue;
687 
688     RelSecName = RelSecName.substr(
689         RelSecName.find_first_not_of("._")); // Skip . and _ prefixes.
690 
691     // TODO: Add support for relocations in other sections as needed.
692     // Record relocations for the debug_info and debug_line sections.
693     RelocAddrMap *Map = StringSwitch<RelocAddrMap*>(RelSecName)
694         .Case("debug_info", &InfoSection.Relocs)
695         .Case("debug_loc", &LocSection.Relocs)
696         .Case("debug_info.dwo", &InfoDWOSection.Relocs)
697         .Case("debug_line", &LineSection.Relocs)
698         .Case("apple_names", &AppleNamesSection.Relocs)
699         .Case("apple_types", &AppleTypesSection.Relocs)
700         .Case("apple_namespaces", &AppleNamespacesSection.Relocs)
701         .Case("apple_namespac", &AppleNamespacesSection.Relocs)
702         .Case("apple_objc", &AppleObjCSection.Relocs)
703         .Default(nullptr);
704     if (!Map) {
705       // Find debug_types relocs by section rather than name as there are
706       // multiple, comdat grouped, debug_types sections.
707       if (RelSecName == "debug_types")
708         Map = &TypesSections[*RelocatedSection].Relocs;
709       else if (RelSecName == "debug_types.dwo")
710         Map = &TypesDWOSections[*RelocatedSection].Relocs;
711       else
712         continue;
713     }
714 
715     if (Section.relocation_begin() != Section.relocation_end()) {
716       uint64_t SectionSize = RelocatedSection->getSize();
717       for (const RelocationRef &Reloc : Section.relocations()) {
718         uint64_t Address = Reloc.getOffset();
719         uint64_t Type = Reloc.getType();
720         uint64_t SymAddr = 0;
721         uint64_t SectionLoadAddress = 0;
722         object::symbol_iterator Sym = Reloc.getSymbol();
723         object::section_iterator RSec = Obj.section_end();
724 
725         // First calculate the address of the symbol or section as it appears
726         // in the objct file
727         if (Sym != Obj.symbol_end()) {
728           Expected<uint64_t> SymAddrOrErr = Sym->getAddress();
729           if (!SymAddrOrErr) {
730             std::string Buf;
731             raw_string_ostream OS(Buf);
732             logAllUnhandledErrors(SymAddrOrErr.takeError(), OS, "");
733             OS.flush();
734             errs() << "error: failed to compute symbol address: "
735                    << Buf << '\n';
736             continue;
737           }
738           SymAddr = *SymAddrOrErr;
739           // Also remember what section this symbol is in for later
740           auto SectOrErr = Sym->getSection();
741           if (!SectOrErr) {
742             std::string Buf;
743             raw_string_ostream OS(Buf);
744             logAllUnhandledErrors(SectOrErr.takeError(), OS, "");
745             OS.flush();
746             errs() << "error: failed to get symbol section: "
747                    << Buf << '\n';
748             continue;
749           }
750           RSec = *SectOrErr;
751         } else if (auto *MObj = dyn_cast<MachOObjectFile>(&Obj)) {
752           // MachO also has relocations that point to sections and
753           // scattered relocations.
754           auto RelocInfo = MObj->getRelocation(Reloc.getRawDataRefImpl());
755           if (MObj->isRelocationScattered(RelocInfo)) {
756             // FIXME: it's not clear how to correctly handle scattered
757             // relocations.
758             continue;
759           } else {
760             RSec = MObj->getRelocationSection(Reloc.getRawDataRefImpl());
761             SymAddr = RSec->getAddress();
762           }
763         }
764 
765         // If we are given load addresses for the sections, we need to adjust:
766         // SymAddr = (Address of Symbol Or Section in File) -
767         //           (Address of Section in File) +
768         //           (Load Address of Section)
769         if (L != nullptr && RSec != Obj.section_end()) {
770           // RSec is now either the section being targeted or the section
771           // containing the symbol being targeted. In either case,
772           // we need to perform the same computation.
773           StringRef SecName;
774           RSec->getName(SecName);
775 //           llvm::dbgs() << "Name: '" << SecName
776 //                        << "', RSec: " << RSec->getRawDataRefImpl()
777 //                        << ", Section: " << Section.getRawDataRefImpl() << "\n";
778           SectionLoadAddress = L->getSectionLoadAddress(*RSec);
779           if (SectionLoadAddress != 0)
780             SymAddr += SectionLoadAddress - RSec->getAddress();
781         }
782 
783         object::RelocVisitor V(Obj);
784         object::RelocToApply R(V.visit(Type, Reloc, SymAddr));
785         if (V.error()) {
786           SmallString<32> Name;
787           Reloc.getTypeName(Name);
788           errs() << "error: failed to compute relocation: "
789                  << Name << "\n";
790           continue;
791         }
792 
793         if (Address + R.Width > SectionSize) {
794           errs() << "error: " << R.Width << "-byte relocation starting "
795                  << Address << " bytes into section " << name << " which is "
796                  << SectionSize << " bytes long.\n";
797           continue;
798         }
799         if (R.Width > 8) {
800           errs() << "error: can't handle a relocation of more than 8 bytes at "
801                     "a time.\n";
802           continue;
803         }
804         DEBUG(dbgs() << "Writing " << format("%p", R.Value)
805                      << " at " << format("%p", Address)
806                      << " with width " << format("%d", R.Width)
807                      << "\n");
808         Map->insert(std::make_pair(Address, std::make_pair(R.Width, R.Value)));
809       }
810     }
811   }
812 }
813 
814 void DWARFContextInMemory::anchor() { }
815