tools/llvm-objdump/ELFDump.cpp

   1 //===-- ELFDump.cpp - ELF-specific dumper -----------------------*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 ///
   9 /// \file
  10 /// This file implements the ELF-specific dumper for llvm-objdump.
  11 ///
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "llvm-objdump.h"
  15 #include "llvm/Demangle/Demangle.h"
  16 #include "llvm/Object/ELFObjectFile.h"
  17 #include "llvm/Support/Format.h"
  18 #include "llvm/Support/MathExtras.h"
  19 #include "llvm/Support/raw_ostream.h"
  20
  21 using namespace llvm::object;
  22
  23 namespace llvm {
  24 template <class ELFT>
  25 static Expected<StringRef> getDynamicStrTab(const ELFFile<ELFT> *Elf) {
  26   auto DynamicEntriesOrError = Elf->dynamicEntries();
  27   if (!DynamicEntriesOrError)
  28     return DynamicEntriesOrError.takeError();
  29
  30   for (const typename ELFT::Dyn &Dyn : *DynamicEntriesOrError) {
  31     if (Dyn.d_tag == ELF::DT_STRTAB) {
  32       auto MappedAddrOrError = Elf->toMappedAddr(Dyn.getPtr());
  33       if (!MappedAddrOrError)
  34         consumeError(MappedAddrOrError.takeError());
  35       return StringRef(reinterpret_cast<const char *>(*MappedAddrOrError));
  36     }
  37   }
  38
  39   // If the dynamic segment is not present, we fall back on the sections.
  40   auto SectionsOrError = Elf->sections();
  41   if (!SectionsOrError)
  42     return SectionsOrError.takeError();
  43
  44   for (const typename ELFT::Shdr &Sec : *SectionsOrError) {
  45     if (Sec.sh_type == ELF::SHT_DYNSYM)
  46       return Elf->getStringTableForSymtab(Sec);
  47   }
  48
  49   return createError("dynamic string table not found");
  50 }
  51
  52 template <class ELFT>
  53 static Error getRelocationValueString(const ELFObjectFile<ELFT> *Obj,
  54                                       const RelocationRef &RelRef,
  55                                       SmallVectorImpl<char> &Result) {
  56   const ELFFile<ELFT> &EF = *Obj->getELFFile();
  57   DataRefImpl Rel = RelRef.getRawDataRefImpl();
  58   auto SecOrErr = EF.getSection(Rel.d.a);
  59   if (!SecOrErr)
  60     return SecOrErr.takeError();
  61
  62   int64_t Addend = 0;
  63   // If there is no Symbol associated with the relocation, we set the undef
  64   // boolean value to 'true'. This will prevent us from calling functions that
  65   // requires the relocation to be associated with a symbol.
  66   //
  67   // In SHT_REL case we would need to read the addend from section data.
  68   // GNU objdump does not do that and we just follow for simplicity atm.
  69   bool Undef = false;
  70   if ((*SecOrErr)->sh_type == ELF::SHT_RELA) {
  71     const typename ELFT::Rela *ERela = Obj->getRela(Rel);
  72     Addend = ERela->r_addend;
  73     Undef = ERela->getSymbol(false) == 0;
  74   } else if ((*SecOrErr)->sh_type != ELF::SHT_REL) {
  75     return make_error<BinaryError>();
  76   }
  77
  78   // Default scheme is to print Target, as well as "+ <addend>" for nonzero
  79   // addend. Should be acceptable for all normal purposes.
  80   std::string FmtBuf;
  81   raw_string_ostream Fmt(FmtBuf);
  82
  83   if (!Undef) {
  84     symbol_iterator SI = RelRef.getSymbol();
  85     const typename ELFT::Sym *Sym = Obj->getSymbol(SI->getRawDataRefImpl());
  86     if (Sym->getType() == ELF::STT_SECTION) {
  87       Expected<section_iterator> SymSI = SI->getSection();
  88       if (!SymSI)
  89         return SymSI.takeError();
  90       const typename ELFT::Shdr *SymSec =
  91           Obj->getSection((*SymSI)->getRawDataRefImpl());
  92       auto SecName = EF.getSectionName(SymSec);
  93       if (!SecName)
  94         return SecName.takeError();
  95       Fmt << *SecName;
  96     } else {
  97       Expected<StringRef> SymName = SI->getName();
  98       if (!SymName)
  99         return SymName.takeError();
 100       if (Demangle)
 101         Fmt << demangle(*SymName);
 102       else
 103         Fmt << *SymName;
 104     }
 105   } else {
 106     Fmt << "*ABS*";
 107   }
 108
 109   if (Addend != 0)
 110     Fmt << (Addend < 0 ? "" : "+") << Addend;
 111   Fmt.flush();
 112   Result.append(FmtBuf.begin(), FmtBuf.end());
 113   return Error::success();
 114 }
 115
 116 Error getELFRelocationValueString(const ELFObjectFileBase *Obj,
 117                                   const RelocationRef &Rel,
 118                                   SmallVectorImpl<char> &Result) {
 119   if (auto *ELF32LE = dyn_cast<ELF32LEObjectFile>(Obj))
 120     return getRelocationValueString(ELF32LE, Rel, Result);
 121   if (auto *ELF64LE = dyn_cast<ELF64LEObjectFile>(Obj))
 122     return getRelocationValueString(ELF64LE, Rel, Result);
 123   if (auto *ELF32BE = dyn_cast<ELF32BEObjectFile>(Obj))
 124     return getRelocationValueString(ELF32BE, Rel, Result);
 125   auto *ELF64BE = cast<ELF64BEObjectFile>(Obj);
 126   return getRelocationValueString(ELF64BE, Rel, Result);
 127 }
 128
 129 template <class ELFT>
 130 static uint64_t getSectionLMA(const ELFFile<ELFT> *Obj,
 131                               const object::ELFSectionRef &Sec) {
 132   auto PhdrRangeOrErr = Obj->program_headers();
 133   if (!PhdrRangeOrErr)
 134     report_fatal_error(toString(PhdrRangeOrErr.takeError()));
 135
 136   // Search for a PT_LOAD segment containing the requested section. Use this
 137   // segment's p_addr to calculate the section's LMA.
 138   for (const typename ELFT::Phdr &Phdr : *PhdrRangeOrErr)
 139     if ((Phdr.p_type == ELF::PT_LOAD) && (Phdr.p_vaddr <= Sec.getAddress()) &&
 140         (Phdr.p_vaddr + Phdr.p_memsz > Sec.getAddress()))
 141       return Sec.getAddress() - Phdr.p_vaddr + Phdr.p_paddr;
 142
 143   // Return section's VMA if it isn't in a PT_LOAD segment.
 144   return Sec.getAddress();
 145 }
 146
 147 uint64_t getELFSectionLMA(const object::ELFSectionRef &Sec) {
 148   if (const auto *ELFObj = dyn_cast<ELF32LEObjectFile>(Sec.getObject()))
 149     return getSectionLMA(ELFObj->getELFFile(), Sec);
 150   else if (const auto *ELFObj = dyn_cast<ELF32BEObjectFile>(Sec.getObject()))
 151     return getSectionLMA(ELFObj->getELFFile(), Sec);
 152   else if (const auto *ELFObj = dyn_cast<ELF64LEObjectFile>(Sec.getObject()))
 153     return getSectionLMA(ELFObj->getELFFile(), Sec);
 154   const auto *ELFObj = cast<ELF64BEObjectFile>(Sec.getObject());
 155   return getSectionLMA(ELFObj->getELFFile(), Sec);
 156 }
 157
 158 template <class ELFT>
 159 void printDynamicSection(const ELFFile<ELFT> *Elf, StringRef Filename) {
 160   ArrayRef<typename ELFT::Dyn> DynamicEntries =
 161       unwrapOrError(Elf->dynamicEntries(), Filename);
 162   outs() << "Dynamic Section:\n";
 163   for (const typename ELFT::Dyn &Dyn : DynamicEntries) {
 164     if (Dyn.d_tag == ELF::DT_NULL)
 165       continue;
 166
 167     std::string Str = Elf->getDynamicTagAsString(Dyn.d_tag);
 168     outs() << format("  %-21s", Str.c_str());
 169
 170     const char *Fmt =
 171         ELFT::Is64Bits ? "0x%016" PRIx64 "\n" : "0x%08" PRIx64 "\n";
 172     if (Dyn.d_tag == ELF::DT_NEEDED || Dyn.d_tag == ELF::DT_RPATH ||
 173         Dyn.d_tag == ELF::DT_RUNPATH || Dyn.d_tag == ELF::DT_SONAME ||
 174         Dyn.d_tag == ELF::DT_AUXILIARY || Dyn.d_tag == ELF::DT_FILTER) {
 175       Expected<StringRef> StrTabOrErr = getDynamicStrTab(Elf);
 176       if (StrTabOrErr) {
 177         const char *Data = StrTabOrErr.get().data();
 178         outs() << (Data + Dyn.d_un.d_val) << "\n";
 179         continue;
 180       }
 181       reportWarning(toString(StrTabOrErr.takeError()), Filename);
 182       consumeError(StrTabOrErr.takeError());
 183     }
 184     outs() << format(Fmt, (uint64_t)Dyn.d_un.d_val);
 185   }
 186 }
 187
 188 template <class ELFT> void printProgramHeaders(const ELFFile<ELFT> *o) {
 189   outs() << "Program Header:\n";
 190   auto ProgramHeaderOrError = o->program_headers();
 191   if (!ProgramHeaderOrError)
 192     report_fatal_error(toString(ProgramHeaderOrError.takeError()));
 193   for (const typename ELFT::Phdr &Phdr : *ProgramHeaderOrError) {
 194     switch (Phdr.p_type) {
 195     case ELF::PT_DYNAMIC:
 196       outs() << " DYNAMIC ";
 197       break;
 198     case ELF::PT_GNU_EH_FRAME:
 199       outs() << "EH_FRAME ";
 200       break;
 201     case ELF::PT_GNU_RELRO:
 202       outs() << "   RELRO ";
 203       break;
 204     case ELF::PT_GNU_STACK:
 205       outs() << "   STACK ";
 206       break;
 207     case ELF::PT_INTERP:
 208       outs() << "  INTERP ";
 209       break;
 210     case ELF::PT_LOAD:
 211       outs() << "    LOAD ";
 212       break;
 213     case ELF::PT_NOTE:
 214       outs() << "    NOTE ";
 215       break;
 216     case ELF::PT_OPENBSD_BOOTDATA:
 217       outs() << "    OPENBSD_BOOTDATA ";
 218       break;
 219     case ELF::PT_OPENBSD_RANDOMIZE:
 220       outs() << "    OPENBSD_RANDOMIZE ";
 221       break;
 222     case ELF::PT_OPENBSD_WXNEEDED:
 223       outs() << "    OPENBSD_WXNEEDED ";
 224       break;
 225     case ELF::PT_PHDR:
 226       outs() << "    PHDR ";
 227       break;
 228     case ELF::PT_TLS:
 229       outs() << "    TLS ";
 230       break;
 231     default:
 232       outs() << " UNKNOWN ";
 233     }
 234
 235     const char *Fmt = ELFT::Is64Bits ? "0x%016" PRIx64 " " : "0x%08" PRIx64 " ";
 236
 237     outs() << "off    " << format(Fmt, (uint64_t)Phdr.p_offset) << "vaddr "
 238            << format(Fmt, (uint64_t)Phdr.p_vaddr) << "paddr "
 239            << format(Fmt, (uint64_t)Phdr.p_paddr)
 240            << format("align 2**%u\n",
 241                      countTrailingZeros<uint64_t>(Phdr.p_align))
 242            << "         filesz " << format(Fmt, (uint64_t)Phdr.p_filesz)
 243            << "memsz " << format(Fmt, (uint64_t)Phdr.p_memsz) << "flags "
 244            << ((Phdr.p_flags & ELF::PF_R) ? "r" : "-")
 245            << ((Phdr.p_flags & ELF::PF_W) ? "w" : "-")
 246            << ((Phdr.p_flags & ELF::PF_X) ? "x" : "-") << "\n";
 247   }
 248   outs() << "\n";
 249 }
 250
 251 template <class ELFT>
 252 void printSymbolVersionDependency(ArrayRef<uint8_t> Contents,
 253                                   StringRef StrTab) {
 254   outs() << "Version References:\n";
 255
 256   const uint8_t *Buf = Contents.data();
 257   while (Buf) {
 258     auto *Verneed = reinterpret_cast<const typename ELFT::Verneed *>(Buf);
 259     outs() << "  required from "
 260            << StringRef(StrTab.drop_front(Verneed->vn_file).data()) << ":\n";
 261
 262     const uint8_t *BufAux = Buf + Verneed->vn_aux;
 263     while (BufAux) {
 264       auto *Vernaux = reinterpret_cast<const typename ELFT::Vernaux *>(BufAux);
 265       outs() << "    "
 266              << format("0x%08" PRIx32 " ", (uint32_t)Vernaux->vna_hash)
 267              << format("0x%02" PRIx16 " ", (uint16_t)Vernaux->vna_flags)
 268              << format("%02" PRIu16 " ", (uint16_t)Vernaux->vna_other)
 269              << StringRef(StrTab.drop_front(Vernaux->vna_name).data()) << '\n';
 270       BufAux = Vernaux->vna_next ? BufAux + Vernaux->vna_next : nullptr;
 271     }
 272     Buf = Verneed->vn_next ? Buf + Verneed->vn_next : nullptr;
 273   }
 274 }
 275
 276 template <class ELFT>
 277 void printSymbolVersionDefinition(const typename ELFT::Shdr &Shdr,
 278                                   ArrayRef<uint8_t> Contents,
 279                                   StringRef StrTab) {
 280   outs() << "Version definitions:\n";
 281
 282   const uint8_t *Buf = Contents.data();
 283   uint32_t VerdefIndex = 1;
 284   // sh_info contains the number of entries in the SHT_GNU_verdef section. To
 285   // make the index column have consistent width, we should insert blank spaces
 286   // according to sh_info.
 287   uint16_t VerdefIndexWidth = std::to_string(Shdr.sh_info).size();
 288   while (Buf) {
 289     auto *Verdef = reinterpret_cast<const typename ELFT::Verdef *>(Buf);
 290     outs() << format_decimal(VerdefIndex++, VerdefIndexWidth) << " "
 291            << format("0x%02" PRIx16 " ", (uint16_t)Verdef->vd_flags)
 292            << format("0x%08" PRIx32 " ", (uint32_t)Verdef->vd_hash);
 293
 294     const uint8_t *BufAux = Buf + Verdef->vd_aux;
 295     uint16_t VerdauxIndex = 0;
 296     while (BufAux) {
 297       auto *Verdaux = reinterpret_cast<const typename ELFT::Verdaux *>(BufAux);
 298       if (VerdauxIndex)
 299         outs() << std::string(VerdefIndexWidth + 17, ' ');
 300       outs() << StringRef(StrTab.drop_front(Verdaux->vda_name).data()) << '\n';
 301       BufAux = Verdaux->vda_next ? BufAux + Verdaux->vda_next : nullptr;
 302       ++VerdauxIndex;
 303     }
 304     Buf = Verdef->vd_next ? Buf + Verdef->vd_next : nullptr;
 305   }
 306 }
 307
 308 template <class ELFT>
 309 void printSymbolVersionInfo(const ELFFile<ELFT> *Elf, StringRef FileName) {
 310   ArrayRef<typename ELFT::Shdr> Sections =
 311       unwrapOrError(Elf->sections(), FileName);
 312   for (const typename ELFT::Shdr &Shdr : Sections) {
 313     if (Shdr.sh_type != ELF::SHT_GNU_verneed &&
 314         Shdr.sh_type != ELF::SHT_GNU_verdef)
 315       continue;
 316
 317     ArrayRef<uint8_t> Contents =
 318         unwrapOrError(Elf->getSectionContents(&Shdr), FileName);
 319     const typename ELFT::Shdr *StrTabSec =
 320         unwrapOrError(Elf->getSection(Shdr.sh_link), FileName);
 321     StringRef StrTab = unwrapOrError(Elf->getStringTable(StrTabSec), FileName);
 322
 323     if (Shdr.sh_type == ELF::SHT_GNU_verneed)
 324       printSymbolVersionDependency<ELFT>(Contents, StrTab);
 325     else
 326       printSymbolVersionDefinition<ELFT>(Shdr, Contents, StrTab);
 327   }
 328 }
 329
 330 void printELFFileHeader(const object::ObjectFile *Obj) {
 331   if (const auto *ELFObj = dyn_cast<ELF32LEObjectFile>(Obj))
 332     printProgramHeaders(ELFObj->getELFFile());
 333   else if (const auto *ELFObj = dyn_cast<ELF32BEObjectFile>(Obj))
 334     printProgramHeaders(ELFObj->getELFFile());
 335   else if (const auto *ELFObj = dyn_cast<ELF64LEObjectFile>(Obj))
 336     printProgramHeaders(ELFObj->getELFFile());
 337   else if (const auto *ELFObj = dyn_cast<ELF64BEObjectFile>(Obj))
 338     printProgramHeaders(ELFObj->getELFFile());
 339 }
 340
 341 void printELFDynamicSection(const object::ObjectFile *Obj) {
 342   if (const auto *ELFObj = dyn_cast<ELF32LEObjectFile>(Obj))
 343     printDynamicSection(ELFObj->getELFFile(), Obj->getFileName());
 344   else if (const auto *ELFObj = dyn_cast<ELF32BEObjectFile>(Obj))
 345     printDynamicSection(ELFObj->getELFFile(), Obj->getFileName());
 346   else if (const auto *ELFObj = dyn_cast<ELF64LEObjectFile>(Obj))
 347     printDynamicSection(ELFObj->getELFFile(), Obj->getFileName());
 348   else if (const auto *ELFObj = dyn_cast<ELF64BEObjectFile>(Obj))
 349     printDynamicSection(ELFObj->getELFFile(), Obj->getFileName());
 350 }
 351
 352 void printELFSymbolVersionInfo(const object::ObjectFile *Obj) {
 353   if (const auto *ELFObj = dyn_cast<ELF32LEObjectFile>(Obj))
 354     printSymbolVersionInfo(ELFObj->getELFFile(), Obj->getFileName());
 355   else if (const auto *ELFObj = dyn_cast<ELF32BEObjectFile>(Obj))
 356     printSymbolVersionInfo(ELFObj->getELFFile(), Obj->getFileName());
 357   else if (const auto *ELFObj = dyn_cast<ELF64LEObjectFile>(Obj))
 358     printSymbolVersionInfo(ELFObj->getELFFile(), Obj->getFileName());
 359   else if (const auto *ELFObj = dyn_cast<ELF64BEObjectFile>(Obj))
 360     printSymbolVersionInfo(ELFObj->getELFFile(), Obj->getFileName());
 361 }
 362 } // namespace llvm