src/llvm/lib/DebugInfo/DWARFUnit.cpp

   1 //===-- DWARFUnit.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/DWARFUnit.h"
  11 #include "llvm/DebugInfo/DWARFContext.h"
  12 #include "llvm/DebugInfo/DWARFFormValue.h"
  13 #include "llvm/Support/Dwarf.h"
  14 #include "llvm/Support/Path.h"
  15 #include <cstdio>
  16
  17 using namespace llvm;
  18 using namespace dwarf;
  19
  20 void DWARFUnitSectionBase::parse(DWARFContext &C, const DWARFSection &Section) {
  21   parseImpl(C, Section, C.getDebugAbbrev(), C.getRangeSection(),
  22             C.getStringSection(), StringRef(), C.getAddrSection(),
  23             C.isLittleEndian());
  24 }
  25
  26 void DWARFUnitSectionBase::parseDWO(DWARFContext &C,
  27                                     const DWARFSection &DWOSection) {
  28   parseImpl(C, DWOSection, C.getDebugAbbrevDWO(), C.getRangeDWOSection(),
  29             C.getStringDWOSection(), C.getStringOffsetDWOSection(),
  30             C.getAddrSection(), C.isLittleEndian());
  31 }
  32
  33 DWARFUnit::DWARFUnit(DWARFContext &DC, const DWARFSection &Section,
  34                      const DWARFDebugAbbrev *DA, StringRef RS, StringRef SS,
  35                      StringRef SOS, StringRef AOS, bool LE,
  36                      const DWARFUnitSectionBase &UnitSection)
  37     : Context(DC), InfoSection(Section), Abbrev(DA), RangeSection(RS),
  38       StringSection(SS), StringOffsetSection(SOS), AddrOffsetSection(AOS),
  39       isLittleEndian(LE), UnitSection(UnitSection) {
  40   clear();
  41 }
  42
  43 DWARFUnit::~DWARFUnit() {
  44 }
  45
  46 bool DWARFUnit::getAddrOffsetSectionItem(uint32_t Index,
  47                                                 uint64_t &Result) const {
  48   uint32_t Offset = AddrOffsetSectionBase + Index * AddrSize;
  49   if (AddrOffsetSection.size() < Offset + AddrSize)
  50     return false;
  51   DataExtractor DA(AddrOffsetSection, isLittleEndian, AddrSize);
  52   Result = DA.getAddress(&Offset);
  53   return true;
  54 }
  55
  56 bool DWARFUnit::getStringOffsetSectionItem(uint32_t Index,
  57                                                   uint32_t &Result) const {
  58   // FIXME: string offset section entries are 8-byte for DWARF64.
  59   const uint32_t ItemSize = 4;
  60   uint32_t Offset = Index * ItemSize;
  61   if (StringOffsetSection.size() < Offset + ItemSize)
  62     return false;
  63   DataExtractor DA(StringOffsetSection, isLittleEndian, 0);
  64   Result = DA.getU32(&Offset);
  65   return true;
  66 }
  67
  68 bool DWARFUnit::extractImpl(DataExtractor debug_info, uint32_t *offset_ptr) {
  69   Length = debug_info.getU32(offset_ptr);
  70   Version = debug_info.getU16(offset_ptr);
  71   uint64_t AbbrOffset = debug_info.getU32(offset_ptr);
  72   AddrSize = debug_info.getU8(offset_ptr);
  73
  74   bool LengthOK = debug_info.isValidOffset(getNextUnitOffset() - 1);
  75   bool VersionOK = DWARFContext::isSupportedVersion(Version);
  76   bool AddrSizeOK = AddrSize == 4 || AddrSize == 8;
  77
  78   if (!LengthOK || !VersionOK || !AddrSizeOK)
  79     return false;
  80
  81   Abbrevs = Abbrev->getAbbreviationDeclarationSet(AbbrOffset);
  82   if (Abbrevs == nullptr)
  83     return false;
  84
  85   return true;
  86 }
  87
  88 bool DWARFUnit::extract(DataExtractor debug_info, uint32_t *offset_ptr) {
  89   clear();
  90
  91   Offset = *offset_ptr;
  92
  93   if (debug_info.isValidOffset(*offset_ptr)) {
  94     if (extractImpl(debug_info, offset_ptr))
  95       return true;
  96
  97     // reset the offset to where we tried to parse from if anything went wrong
  98     *offset_ptr = Offset;
  99   }
 100
 101   return false;
 102 }
 103
 104 bool DWARFUnit::extractRangeList(uint32_t RangeListOffset,
 105                                         DWARFDebugRangeList &RangeList) const {
 106   // Require that compile unit is extracted.
 107   assert(DieArray.size() > 0);
 108   DataExtractor RangesData(RangeSection, isLittleEndian, AddrSize);
 109   uint32_t ActualRangeListOffset = RangeSectionBase + RangeListOffset;
 110   return RangeList.extract(RangesData, &ActualRangeListOffset);
 111 }
 112
 113 void DWARFUnit::clear() {
 114   Offset = 0;
 115   Length = 0;
 116   Version = 0;
 117   Abbrevs = nullptr;
 118   AddrSize = 0;
 119   BaseAddr = 0;
 120   RangeSectionBase = 0;
 121   AddrOffsetSectionBase = 0;
 122   clearDIEs(false);
 123   DWO.reset();
 124 }
 125
 126 const char *DWARFUnit::getCompilationDir() {
 127   extractDIEsIfNeeded(true);
 128   if (DieArray.empty())
 129     return nullptr;
 130   return DieArray[0].getAttributeValueAsString(this, DW_AT_comp_dir, nullptr);
 131 }
 132
 133 uint64_t DWARFUnit::getDWOId() {
 134   extractDIEsIfNeeded(true);
 135   const uint64_t FailValue = -1ULL;
 136   if (DieArray.empty())
 137     return FailValue;
 138   return DieArray[0]
 139       .getAttributeValueAsUnsignedConstant(this, DW_AT_GNU_dwo_id, FailValue);
 140 }
 141
 142 void DWARFUnit::setDIERelations() {
 143   if (DieArray.size() <= 1)
 144     return;
 145
 146   std::vector<DWARFDebugInfoEntryMinimal *> ParentChain;
 147   DWARFDebugInfoEntryMinimal *SiblingChain = nullptr;
 148   for (auto &DIE : DieArray) {
 149     if (SiblingChain) {
 150       SiblingChain->setSibling(&DIE);
 151     }
 152     if (const DWARFAbbreviationDeclaration *AbbrDecl =
 153             DIE.getAbbreviationDeclarationPtr()) {
 154       // Normal DIE.
 155       if (AbbrDecl->hasChildren()) {
 156         ParentChain.push_back(&DIE);
 157         SiblingChain = nullptr;
 158       } else {
 159         SiblingChain = &DIE;
 160       }
 161     } else {
 162       // NULL entry terminates the sibling chain.
 163       SiblingChain = ParentChain.back();
 164       ParentChain.pop_back();
 165     }
 166   }
 167   assert(SiblingChain == nullptr || SiblingChain == &DieArray[0]);
 168   assert(ParentChain.empty());
 169 }
 170
 171 void DWARFUnit::extractDIEsToVector(
 172     bool AppendCUDie, bool AppendNonCUDies,
 173     std::vector<DWARFDebugInfoEntryMinimal> &Dies) const {
 174   if (!AppendCUDie && !AppendNonCUDies)
 175     return;
 176
 177   // Set the offset to that of the first DIE and calculate the start of the
 178   // next compilation unit header.
 179   uint32_t DIEOffset = Offset + getHeaderSize();
 180   uint32_t NextCUOffset = getNextUnitOffset();
 181   DWARFDebugInfoEntryMinimal DIE;
 182   uint32_t Depth = 0;
 183   bool IsCUDie = true;
 184
 185   while (DIEOffset < NextCUOffset && DIE.extractFast(this, &DIEOffset)) {
 186     if (IsCUDie) {
 187       if (AppendCUDie)
 188         Dies.push_back(DIE);
 189       if (!AppendNonCUDies)
 190         break;
 191       // The average bytes per DIE entry has been seen to be
 192       // around 14-20 so let's pre-reserve the needed memory for
 193       // our DIE entries accordingly.
 194       Dies.reserve(Dies.size() + getDebugInfoSize() / 14);
 195       IsCUDie = false;
 196     } else {
 197       Dies.push_back(DIE);
 198     }
 199
 200     if (const DWARFAbbreviationDeclaration *AbbrDecl =
 201             DIE.getAbbreviationDeclarationPtr()) {
 202       // Normal DIE
 203       if (AbbrDecl->hasChildren())
 204         ++Depth;
 205     } else {
 206       // NULL DIE.
 207       if (Depth > 0)
 208         --Depth;
 209       if (Depth == 0)
 210         break;  // We are done with this compile unit!
 211     }
 212   }
 213
 214   // Give a little bit of info if we encounter corrupt DWARF (our offset
 215   // should always terminate at or before the start of the next compilation
 216   // unit header).
 217   if (DIEOffset > NextCUOffset)
 218     fprintf(stderr, "warning: DWARF compile unit extends beyond its "
 219                     "bounds cu 0x%8.8x at 0x%8.8x'\n", getOffset(), DIEOffset);
 220 }
 221
 222 size_t DWARFUnit::extractDIEsIfNeeded(bool CUDieOnly) {
 223   if ((CUDieOnly && DieArray.size() > 0) ||
 224       DieArray.size() > 1)
 225     return 0; // Already parsed.
 226
 227   bool HasCUDie = DieArray.size() > 0;
 228   extractDIEsToVector(!HasCUDie, !CUDieOnly, DieArray);
 229
 230   if (DieArray.empty())
 231     return 0;
 232
 233   // If CU DIE was just parsed, copy several attribute values from it.
 234   if (!HasCUDie) {
 235     uint64_t BaseAddr =
 236         DieArray[0].getAttributeValueAsAddress(this, DW_AT_low_pc, -1ULL);
 237     if (BaseAddr == -1ULL)
 238       BaseAddr = DieArray[0].getAttributeValueAsAddress(this, DW_AT_entry_pc, 0);
 239     setBaseAddress(BaseAddr);
 240     AddrOffsetSectionBase = DieArray[0].getAttributeValueAsSectionOffset(
 241         this, DW_AT_GNU_addr_base, 0);
 242     RangeSectionBase = DieArray[0].getAttributeValueAsSectionOffset(
 243         this, DW_AT_ranges_base, 0);
 244     // Don't fall back to DW_AT_GNU_ranges_base: it should be ignored for
 245     // skeleton CU DIE, so that DWARF users not aware of it are not broken.
 246   }
 247
 248   setDIERelations();
 249   return DieArray.size();
 250 }
 251
 252 DWARFUnit::DWOHolder::DWOHolder(StringRef DWOPath)
 253     : DWOFile(), DWOContext(), DWOU(nullptr) {
 254   auto Obj = object::ObjectFile::createObjectFile(DWOPath);
 255   if (!Obj)
 256     return;
 257   DWOFile = std::move(Obj.get());
 258   DWOContext.reset(
 259       cast<DWARFContext>(DIContext::getDWARFContext(*DWOFile.getBinary())));
 260   if (DWOContext->getNumDWOCompileUnits() > 0)
 261     DWOU = DWOContext->getDWOCompileUnitAtIndex(0);
 262 }
 263
 264 bool DWARFUnit::parseDWO() {
 265   if (DWO.get())
 266     return false;
 267   extractDIEsIfNeeded(true);
 268   if (DieArray.empty())
 269     return false;
 270   const char *DWOFileName =
 271       DieArray[0].getAttributeValueAsString(this, DW_AT_GNU_dwo_name, nullptr);
 272   if (!DWOFileName)
 273     return false;
 274   const char *CompilationDir =
 275       DieArray[0].getAttributeValueAsString(this, DW_AT_comp_dir, nullptr);
 276   SmallString<16> AbsolutePath;
 277   if (sys::path::is_relative(DWOFileName) && CompilationDir != nullptr) {
 278     sys::path::append(AbsolutePath, CompilationDir);
 279   }
 280   sys::path::append(AbsolutePath, DWOFileName);
 281   DWO = llvm::make_unique<DWOHolder>(AbsolutePath);
 282   DWARFUnit *DWOCU = DWO->getUnit();
 283   // Verify that compile unit in .dwo file is valid.
 284   if (!DWOCU || DWOCU->getDWOId() != getDWOId()) {
 285     DWO.reset();
 286     return false;
 287   }
 288   // Share .debug_addr and .debug_ranges section with compile unit in .dwo
 289   DWOCU->setAddrOffsetSection(AddrOffsetSection, AddrOffsetSectionBase);
 290   uint32_t DWORangesBase = DieArray[0].getRangesBaseAttribute(this, 0);
 291   DWOCU->setRangesSection(RangeSection, DWORangesBase);
 292   return true;
 293 }
 294
 295 void DWARFUnit::clearDIEs(bool KeepCUDie) {
 296   if (DieArray.size() > (unsigned)KeepCUDie) {
 297     // std::vectors never get any smaller when resized to a smaller size,
 298     // or when clear() or erase() are called, the size will report that it
 299     // is smaller, but the memory allocated remains intact (call capacity()
 300     // to see this). So we need to create a temporary vector and swap the
 301     // contents which will cause just the internal pointers to be swapped
 302     // so that when temporary vector goes out of scope, it will destroy the
 303     // contents.
 304     std::vector<DWARFDebugInfoEntryMinimal> TmpArray;
 305     DieArray.swap(TmpArray);
 306     // Save at least the compile unit DIE
 307     if (KeepCUDie)
 308       DieArray.push_back(TmpArray.front());
 309   }
 310 }
 311
 312 void DWARFUnit::collectAddressRanges(DWARFAddressRangesVector &CURanges) {
 313   // First, check if CU DIE describes address ranges for the unit.
 314   const auto &CUDIERanges = getCompileUnitDIE()->getAddressRanges(this);
 315   if (!CUDIERanges.empty()) {
 316     CURanges.insert(CURanges.end(), CUDIERanges.begin(), CUDIERanges.end());
 317     return;
 318   }
 319
 320   // This function is usually called if there in no .debug_aranges section
 321   // in order to produce a compile unit level set of address ranges that
 322   // is accurate. If the DIEs weren't parsed, then we don't want all dies for
 323   // all compile units to stay loaded when they weren't needed. So we can end
 324   // up parsing the DWARF and then throwing them all away to keep memory usage
 325   // down.
 326   const bool ClearDIEs = extractDIEsIfNeeded(false) > 1;
 327   DieArray[0].collectChildrenAddressRanges(this, CURanges);
 328
 329   // Collect address ranges from DIEs in .dwo if necessary.
 330   bool DWOCreated = parseDWO();
 331   if (DWO.get())
 332     DWO->getUnit()->collectAddressRanges(CURanges);
 333   if (DWOCreated)
 334     DWO.reset();
 335
 336   // Keep memory down by clearing DIEs if this generate function
 337   // caused them to be parsed.
 338   if (ClearDIEs)
 339     clearDIEs(true);
 340 }
 341
 342 const DWARFDebugInfoEntryMinimal *
 343 DWARFUnit::getSubprogramForAddress(uint64_t Address) {
 344   extractDIEsIfNeeded(false);
 345   for (const DWARFDebugInfoEntryMinimal &DIE : DieArray) {
 346     if (DIE.isSubprogramDIE() &&
 347         DIE.addressRangeContainsAddress(this, Address)) {
 348       return &DIE;
 349     }
 350   }
 351   return nullptr;
 352 }
 353
 354 DWARFDebugInfoEntryInlinedChain
 355 DWARFUnit::getInlinedChainForAddress(uint64_t Address) {
 356   // First, find a subprogram that contains the given address (the root
 357   // of inlined chain).
 358   const DWARFUnit *ChainCU = nullptr;
 359   const DWARFDebugInfoEntryMinimal *SubprogramDIE =
 360       getSubprogramForAddress(Address);
 361   if (SubprogramDIE) {
 362     ChainCU = this;
 363   } else {
 364     // Try to look for subprogram DIEs in the DWO file.
 365     parseDWO();
 366     if (DWO.get()) {
 367       SubprogramDIE = DWO->getUnit()->getSubprogramForAddress(Address);
 368       if (SubprogramDIE)
 369         ChainCU = DWO->getUnit();
 370     }
 371   }
 372
 373   // Get inlined chain rooted at this subprogram DIE.
 374   if (!SubprogramDIE)
 375     return DWARFDebugInfoEntryInlinedChain();
 376   return SubprogramDIE->getInlinedChainForAddress(ChainCU, Address);
 377 }