1 //===- DWARF.cpp ----------------------------------------------------------===// 2 // 3 // The LLVM Linker 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // The -gdb-index option instructs the linker to emit a .gdb_index section. 11 // The section contains information to make gdb startup faster. 12 // The format of the section is described at 13 // https://sourceware.org/gdb/onlinedocs/gdb/Index-Section-Format.html. 14 // 15 //===----------------------------------------------------------------------===// 16 17 #include "DWARF.h" 18 #include "Symbols.h" 19 #include "Target.h" 20 #include "lld/Common/Memory.h" 21 #include "llvm/DebugInfo/DWARF/DWARFDebugPubTable.h" 22 #include "llvm/Object/ELFObjectFile.h" 23 24 using namespace llvm; 25 using namespace llvm::object; 26 using namespace lld; 27 using namespace lld::elf; 28 29 template <class ELFT> LLDDwarfObj<ELFT>::LLDDwarfObj(ObjFile<ELFT> *Obj) { 30 for (InputSectionBase *Sec : Obj->getSections()) { 31 if (!Sec) 32 continue; 33 34 if (LLDDWARFSection *M = 35 StringSwitch<LLDDWARFSection *>(Sec->Name) 36 .Case(".debug_gnu_pubnames", &GnuPubNamesSection) 37 .Case(".debug_gnu_pubtypes", &GnuPubTypesSection) 38 .Case(".debug_info", &InfoSection) 39 .Case(".debug_ranges", &RangeSection) 40 .Case(".debug_line", &LineSection) 41 .Default(nullptr)) { 42 M->Data = toStringRef(Sec->data()); 43 M->Sec = Sec; 44 continue; 45 } 46 47 if (Sec->Name == ".debug_abbrev") 48 AbbrevSection = toStringRef(Sec->data()); 49 else if (Sec->Name == ".debug_str") 50 StrSection = toStringRef(Sec->data()); 51 else if (Sec->Name == ".debug_line_str") 52 LineStringSection = toStringRef(Sec->data()); 53 } 54 } 55 56 // Find if there is a relocation at Pos in Sec. The code is a bit 57 // more complicated than usual because we need to pass a section index 58 // to llvm since it has no idea about InputSection. 59 template <class ELFT> 60 template <class RelTy> 61 Optional<RelocAddrEntry> 62 LLDDwarfObj<ELFT>::findAux(const InputSectionBase &Sec, uint64_t Pos, 63 ArrayRef<RelTy> Rels) const { 64 auto It = std::lower_bound( 65 Rels.begin(), Rels.end(), Pos, 66 [](const RelTy &A, uint64_t B) { return A.r_offset < B; }); 67 if (It == Rels.end() || It->r_offset != Pos) 68 return None; 69 const RelTy &Rel = *It; 70 71 const ObjFile<ELFT> *File = Sec.getFile<ELFT>(); 72 uint32_t SymIndex = Rel.getSymbol(Config->IsMips64EL); 73 const typename ELFT::Sym &Sym = File->getELFSyms()[SymIndex]; 74 uint32_t SecIndex = File->getSectionIndex(Sym); 75 76 // Broken debug info can point to a non-Defined symbol. 77 auto *DR = dyn_cast<Defined>(&File->getRelocTargetSym(Rel)); 78 if (!DR) { 79 RelType Type = Rel.getType(Config->IsMips64EL); 80 if (Type != Target->NoneRel) 81 error(toString(File) + ": relocation " + lld::toString(Type) + " at 0x" + 82 llvm::utohexstr(Rel.r_offset) + " has unsupported target"); 83 return None; 84 } 85 uint64_t Val = DR->Value + getAddend<ELFT>(Rel); 86 87 // FIXME: We should be consistent about always adding the file 88 // offset or not. 89 if (DR->Section->Flags & ELF::SHF_ALLOC) 90 Val += cast<InputSection>(DR->Section)->getOffsetInFile(); 91 92 return RelocAddrEntry{SecIndex, Val}; 93 } 94 95 template <class ELFT> 96 Optional<RelocAddrEntry> LLDDwarfObj<ELFT>::find(const llvm::DWARFSection &S, 97 uint64_t Pos) const { 98 auto &Sec = static_cast<const LLDDWARFSection &>(S); 99 if (Sec.Sec->AreRelocsRela) 100 return findAux(*Sec.Sec, Pos, Sec.Sec->template relas<ELFT>()); 101 return findAux(*Sec.Sec, Pos, Sec.Sec->template rels<ELFT>()); 102 } 103 104 template class elf::LLDDwarfObj<ELF32LE>; 105 template class elf::LLDDwarfObj<ELF32BE>; 106 template class elf::LLDDwarfObj<ELF64LE>; 107 template class elf::LLDDwarfObj<ELF64BE>; 108